Fight Aging!

While I suspect that COVID-19 will feature prominently in most retrospectives on 2020, I'll say only a little on it. The data on mortality by year end, if taken at face value, continues to suggest that the outcome will fall at the higher end of the early estimates of a pandemic three to six times worse than a bad influenza year, ten times worse than a normal influenza year. The people who die are near entirely the old, the co-morbid, and the immunocompromised. They die because they are suffering the damage and dysfunction of aging. Yet the societal conversation and the actions of policy makers ignore this.

There is little discussion outside the research community on greater efforts to restore immune function in the old, or indeed about the reality of the age-related mortality of COVID-19 at all. All infections are treated as equally dangerous; the media dwells extensively upon the very few young victims; the whole of society is closed, at staggering cost, when the risk to most of society is little worse than yearly influenza, and certainly less than that of than driving to work. There was a better approach to this, a cloistering in safety for only the vulnerable, and a continuing willful blindness to that better approach. A cynic might argue that those factions among the powers that be that are ever seeking after greater control, greater surveillance, greater submission, greater conformance, are in the driver's seat these days.

This issue with COVID-19 and aging is perhaps a subset of the broader collection of mistaken views on aging, some of them actively propagated by researchers. Take the concept of "successful aging" for example. By definition, age is an increased risk of death and disease. That is not success, and even where people are using this term to mean a slowing of decline, that is simply aiming too low. We can do better. Rejuvenation is possible in principle, via periodic repair of underlying damage. This has been demonstrated in animal models via strategies such as clearance of senescent cells, and should be the primary goal of research and clinical development.

The Longevity Community

Philanthropic fundraising for research has been impacted by the pandemic, like many other areas. The SENS Research Foundation is nonetheless still running their year end fundraiser, with nearly a million dollars in matching funds from generous donors as an incentive. Donate before the year ends! Further, COVID-19 is no barrier to ongoing conversations, education, and persuasion, whether Aubrey de Grey talking to the Effective Altruism community, the SENS Research Foundation putting out their annual report, or continued political advocacy for longevity in Europe, where single-issue political parties are a viable approach. Much of the world has yet to be persuaded that the treatment of aging is possible, something other than a pipe dream. There is work to accomplish, eyes to be opened.

The longevity industry has been relatively insulated from the impact of COVID-19, which is to say progress has been slowed, but not derailed. Setting aside the dramatic reduction in biotech investment for much of 2020, the usual investor reaction to panic and uncertainty, most life science companies are classed as essential businesses in the US and have continued to work through the shutdown. The more advanced of the early companies have treatments in clinical trials, even while most are still at the preclinical stage. New companies have launched, though we still need many more to cover areas yet to be worked on in earnest. Existing companies made progress and raised funding throughout the year: covered Juvena Therapeutics, Senisca, SIWA Therapeutics, Calico, Oisin Biotechnologies and OncoSenX, the other senolytics companies as a whole, Kimer Med, Insilico Medicine, Five Alarm Bio and Biosens, OneSkin's DNA methylation clock for skin aging, Lygenesis, Juvenescence (several times), Turn.bio and other Methuselah Fund porfolio companies.

EnClear Therapies brought in $10 million for their approach to cerebrospinal fluid filtration to remove molecular wastes that contribute to neurodegeneration. Revel Pharmaceuticals finally obtained seed funding to work on glucosepane cross-link breakers. BioAge raised $90 million for clinical trials of small molecules to slow aging. Investors are building funds and other vehicles (such as the Moonshot Venture Fellowship) to focus on the longevity industry. Examples include Ronjon Nag, Kingsley Advani, and the folk at SP8CEVC, Longevitytech.fund, and LongeVC. It nonetheless remains the case that there are too few experienced biotech funds involved able to support later, larger investments. That is changing, slowly.

Some initial clinical trials have been failing, as often takes place in the early years of an industry. Unity Biotechnology's first senolytic failed phase 2 trial for knee osteoarthritis, provoking a great deal of discussion (some justified, some unfairly post-hoc) as to why it was a poor design and strategy. Still, Big Pharma entities are starting to launch their own senolytics programs. There is gold in those hills.

Conferences of Interest

I attended a few conferences in person in early 2020, prior to the COVID-19 shutdowns, and wrote up notes. The SENS Research Foundation pitch day during the J.P. Morgan Healthcare conference offered a most interesting selection of startups from the longevity industry. Much the same could be said of the Longevity Therapeutics conference, with the addition of researchers presenting on their academic programs. It was all online conferences after that, however. Later in the year I noted a selection of senolytic company showcases from the Longevity Leaders event, and some of the panels from Longevity Week events.

Senescent Cells and Senolytic Therapies

The development of senolytic drugs to clear senescent cells, as well as methods of assessing their effectiveness, is rolling onwards, broadening to include many novel strategies, and attracting greater attention from beyond the scientific community. Further data arrived this year to support the use of senolytics to expand the donor organ supply by salvaging otherwise unusuable organs. Additionally, studies have shown or suggested that senolytics can treat a very wide selection of conditions: osteoporosis, cardiovascular disease, the chondrocyte hypertrophy characteristic of osteoarthritis, osteoarthritis more generally, vulnerability to the cytokine storm of SARS-CoV-2 infection, fibrotic disease, atrial fibrillation, a range of other heart issues, peripheral neuropathy caused by chemotherapy, Alzheimer's disease (a fair amount of research here) and other neurodegenerative conditions, pulmonary fibrosis, glaucoma and other eye conditions, non-healing wounds, even when caused by diabetes, chronic kidney disease, loss of insulin sensitivity, cancers of bone marrow, cervical cancer, accelerated aging resulting from cancer treatments, the atrophy of the thymus, and lung disease. Demonstrating that nothing is ever universally true in biology, researchers found this year that uterine fibrosis does not respond to senolytic treatment, unlike the other forms of fibrotic disease tested.

This year OneSkin launched their topical senolytic treatment, ahead of any published data on its effectiveness in humans, though the data in skin models is intriguing. Of other new approaches to senolytics, taking existing cell-killing drugs and making them safe prodrugs - only activated in the target cells, rather than generally - is perhaps most interesting. Conjugating navitoclax with galactose, for example, ensuring that it is only cleaved into the cytotoxic navitoclax in senescent cells. That has also been accomplished for other chemotherapeutics. Another evolution of navitoclax to reduce its harmful side-effects is to turn it into a PROTAC drug, a compound that removes target molecules by causing them to be degraded by the ubiquitin-proteasome system.

Vaccination against CD153 appears to be mildly senolytic, as are SYK inhibitors, through an as yet unknown mechanism of action. Researchers are still attempting to determine whether nutraceutical senolytics (including plant extracts such as fisetin or the senotherapeutic naringenin) can be effective enough to be interesting. In most cases, one suspects not. MYSM1 upregulation reduces the senescent cell burden in mice. Chimeric antigen receptor approaches can be used to produce senolytic immunotherapies, though not particularly cost-effective ones. Physical fitness, on the other hand, reduces inflammation, but isn't senolytic at all. Reversing cellular senescence by delivering new mitochondria or PDK1 inhibition is scientifically interesting, but sounds risky - some fraction of senescent cells are damaged in ways that may lead to cancer. Hormone therapy in women correlates with lower SASP expression, though it is unclear as to why this is the case. Researchers have started to examine the past use of long-approved drugs newly found to be senolytic, to see if there is any evidence for the degree of benefits. So far this is proving to be challenging.

Beyond senolytics, researchers continue to mine the biology of senescent cells in ever more depth. Any mechanism involved in the onset or maintenance of senescence might turn out to be a useful basis for therapies. The SASP Atlas is one of the results of this work, mapping the senescence assocatiated secretory phenotype (SASP), potentially a rich source of ways to measure the burden of senescence. TGF-β is an important SASP component implicated in the transmission of senescence via the SASP, and so may be microRNAs miR-21 and miR-217. The SASP component CyPA may link hematopoietic cell senescence with cognitive decline. Some degree of suppression of the SASP can be achieved via a variety of approaches, including HDAC inhibition and inhibition of ATM kinase. G3BP1 is required for the SASP to exist, making it perhaps a more attractive potential point of intervention. Genetic databases are being used to identify genes involved in inhibition of cellular senescence - targeting those genes may be a basis for therapy. The genomic architecture of senescent cells is quite different from that of normal cells, and the details are being mapped in more detail. It is possible that non-replicating cells develop a senescence-like state in aged tissues.

Further research is ongoing. Astrocyte senescence kills neurons in cell culture, implicating these cells in neurodegenerative conditions. A better understanding has been developed of how senescent cells cause lung fibrosis (the target of one of the clinical trials for senolytic drugs). USP7 inhibition was shown to be senolytic. Vascular cellular senescence is increased by microRNA-34a. It is suggested that variability in outcomes in stem cell transplantation may be due to the presence of more or fewer senescent cells after expansion of the cells for transplant. Senescent cells contribute to declining NAD+ levels in aging.

Tissue by tissue data is finally arriving for senescent cell accumulation, for both mice and humans. A taxonomy of senescence is beginning to form, as researches start to get a handle on how senescence can differ between cells. A senescent population for which removal might be problematic was identified in the livers of aged mice. Researchers are exploring roles for long non-coding RNAs in cellular senescence. Persistent CMV infection provokes greater senescent cell accumulation, perhaps by causing immune dysfunction. AQP1 is involved in cellular senescence in tendons. Senescent cell accumulation may also be the primary mechanism by which cosmic radiation exposure produces detrimental health outcomes. T cell senescence increases with age and is quite harmful, forming part of an inflammatory feedback loop that can damage healthy tissue.

Cross-Links

Some researchers argue that cross-linking is a hallmark of aging that was overlooked by the authors of the noted Hallmarks of Aging paper. Stiffening of the extracellular matrix in tissues is a consequence of cross-linking, among other factors, is normally considered in skin and blood vessels, but researchers noted this year that it contributes to age-related loss of muscle function as well. A novel approach to breaking cross-links was discussed, the use of spiroligomers, carefully designed to interact in specific ways with cross-link molecules. The supporting work needed for projects focused on glucosepane cross-links, the most prevalent in humans, continued this year with the creation of anti-glucosepane antibodies. Researchers have also proposed inhibition of protein glycation as a way to reduce the creation of cross-links, though life-long therapy of this sort compares unfavorably with approaches that can be applied every few years to clean up existing cross-links. Measuring the cross-link burden in tissues remains challenging; more work will be needed here as targeted approaches to remove cross-links become viable.

Protein Aggregates

There are many forms of amyloid, misfolded proteins that replicate and aggregate in the body, beyond the few (amyloid-β, tau, α-synuclein) that are the focus of neurodegenerative research. This year, it was noted that medin amyloid causes cerebral vascular dysfunction. A good overview of transthyretin amyloidosis was alo published recently.

Microbiomes and Aging

The microbiomes of the body, particularly that of the gut, and their relationships with age are an area of growing research interest. Age-related changes in microbial populations take place, both caused by mechanisms of aging and causative of age-related dysfunctions, a two-way relationship. While most research focuses on the gut microbiome, the skin microbiome was given more attention of late, as are the varied microbiomes of the rest of the body. Researchers are in the process of cataloging specific gut microbial metabolites that harm or aid the body, and for which production changes with age: butyrate is beneficial, while trimethylamine is harmful to arterial function. Polyamine from gut microbes may mediate the relationship between higher environmental temperature and lower rates of osteoporosis. In general, aging results in larger inflammatory populations of gut microbes, and inflammation may be the primary way by which changes in the gut microbiome contribute to conditions such as Alzheimer's disease. In that context it is interesting that changing metabolite production by the microbiome correlates with amyloid burden in the brain. Transplanting gut microbes from old mice to young mice impairs cognitive function.

When it comes to addressing age-related changes in the gut microbiome, a wide range of strategies are being discovered and refined. Supplementation with IAP reduces gut inflammation. Delivery of cyclic peptides suppresses harmful populations to much the same end. Transplanting gut microbes from old rats to young rats produces inflammation and cognitive decline. The old standby of programs of physical activity may exert some of its beneficial effects on health via better maintenance of the gut microbiome.

Immune Aging and Chronic Inflammation

The immune system declines with age, in a complex and yet to be fully mapped fashion. Thus building better vaccines for older people is a poor alternative to rejuvenation of the immune system. We shouldn't need COVID-19 as a reminder in order to be able to argue for greater research into immune system rejuvenation. Yet a lot more work takes place on improving vaccines than there is on improving the immune system, more is the pity.

Immune aging isn't just the cause of increased mortality due to infectious disease. It is likely a major driver of many age-related conditions via chronic inflammation, the persistent unresolved activation of the immune response. This and other issues ensure that rejuvenation of immune function is vital to the treatment of aging. Sustained inflammation encourages cancer metastasis, and the progression of many other age-related conditions, including sarcopenia, vascular stiffness, and, ironically, dysfunction in the generation of new immune cells. It harms the blood-brain barrier, enabling the passage of damaging molecules and cells into the brain. In the brain, microglia become ever more inflammatory with age. It is thought that the evolutionary tradeoff that has produced this inflammatory aging of the immune system is between (a) protection against infection via greater immune activation versus (b) faster aging due to that immune activation.

Inflammation manifests in the actions of the immune system, but has its source in forms of molecular damage and cellular dysfunction in tissues throughout the body that provoke those actions. It is the failure of the immune system to clear senescent cells in later life that accounts for a great deal of that provocation. Skin tissue, being the largest organ provides a sizable contribution, but perhaps not as much as visceral fat tissue in overweight individuals, both tissues becoming laden with senescent cells in older people. Gum disease is another common contribution to raised inflammation, and a risk factor for inflammatory age-related conditions. Cortisol levels decline with age, causing macrophages to become more inflammatory. Interestingly, some contributions to chronic inflammation are physical and structural, such as shear stress in the blood flow of the heart.

Suppression of inflammation by interfering in cell signaling is a going concern, but present clinical strategies are blunt tools. The research community in search of more sophisticated ways to achieve this goal, only suppressing undesirable, excessive, long-term inflammation, while allowing useful, short-term inflammatory processes to proceed. The NLRP3 inflammasome is one potential target. The small molecule MW189 has been tested in patients to reduce inflammation in the brain. IGF-1R inhibition reduces inflammation in Alzheimer's disease mouse models, and delivery of BDNF reverses inflammatory microgial activity in the brains of old mice. MicroRNA-192 in extracellular vesicles suppresses inflammation, and so is a potential basis for treatments. Metformin can reduce liver inflammation. Glucosamine supplementation and TNFα blockade may reduce mortality by lowering inflammation. Alpha-ketogluarate may do much the same. The ketone body β-hydroxybutyrate and RAGE inhibition also inhibit inflammation. Eosinophil immune cells are anti-inflammatory and decline in number with age. Delivering eosinophil cells into visceral fat reduces chronic inflammation caused by that tissue.

The thymus atrophies with age, and evidence continues to accumulate to show this to be an important contributing cause of immune system decline. The thymus is where thymocytes, created in the bone marrow, go to become T cells of the adaptive immune system. Fewer new T cells means a growing loss of immune function. So why not rebuild a thymus? Recellularizing a rat thymus with human cells produces a functional thymus, only the latest of a range of tissue engineering approaches. Thymic atrophy is in part caused by loss of function in thymic epithelial progenitor cells. Cell therapy approaches to thymic regeneration are possible, and two were demonstrated in animal models this year using reprogrammed embryonic fibroblasts and T cell progenitors.

Other approaches exist - and are necessary - to address immune system aging. Replacing the hematopoietic stem cell population for example, as it becomes damaged and dysfunctional, or at the very least stop the signaling that degrades hematopoiesis. Introducing young hematopoietic stem cells extends life span while transplanting bone marrow improves measures of aging, both in old mice. Pharmacological approaches to improving the existing population are more widely considered, however.

Genetics of Aging

The study of genetic variants and their role on longevity is increasing looking like a dead end from the point of view of discovering ways to meaningfully slow or reverse aging. Intensive and expanding analysis of data has found very few genetic influences on longevity, and the effect sizes are small. There are still those who think that very rare variants with large effects on longevity could exist, buried somewhere in the human data. The business as usual is still a matter of discovering variants with small effects on mechanisms connected to aging, however. A BPIFB4 variant affects inflammation and is found in long lived individuals. Overall, long-lived humans do not exihibit fewer harmful gene variants, perhaps suggesting that genetics has a small effect only on variations in life expectancy.

DNA Damage

Nuclear DNA damage of various types occurs progressively with age, and is certainly a cause of cancer. Beyond cancer, researchers are investigating the clonal expansion of mutations that occur in stem cells and progenitor cells in order to find out whether it contributes meaningfully to metabolic disarray in aging. This may or may not be the case, and isn't the only possible mechanism by which further harm may occur. An abnormal chromosome count, aneuploidy, is another form of damage, though it is argued that this can be beneficial in some circumstances, an adaptation that tries to resist some of the damage of aging. Repetitive elements that can copy themselves in the genome are yet another form of DNA damage. They are suppressed in youth, less so in old age. This can be used as the basis for a biomarker of aging, as illustrated by the fact that repetitive element activity is reduced by many interventions known to slow aging in mice.

Mitochondrial Function

Mitochondrial function declines with age, and disruption to mitochondrial structure and activities is noted in many specific age-related conditions, such as cardiovascular disease in general and heart failure and atherosclerosis specifically. Loss of mitochondrial function in T cells produces accelerate aging symptoms in mice. That same loss in monocytes contributes to chronic inflammation in aging. Low mitochondrial DNA copy number was shown this year to produce age-related epigenetic changes in the cell nucleus.

Heart issues are connected to failing mitophagy, the quality control mechanism responsible for removing worn and damage mitochondria, and which falters in its operation with age. Loss of mitophagy is implicated in many age-related conditions, and upregulation of mitophagy is considered a good basis for therapies to improve age-related conditions. Some of this age-related decline in mitophagy is proximately caused by epigenetic changes that suppress mitochondrial function, while deeper causes remain debated.

Many groups are trying to find ways to slow or at least somewhat reverse mitochondrial decline with age. Mitochondrially targeted antioxidants have made their way into the supplement market, or clinical trials and approval in some countries. It remains to be seen how they compare with exercise or NAD+ enhancement. SS-31 is an example yet to reach the clinic, still gathering data. Other approaches include downregulation of miR-155-5p, and delivery of whole new mitochondria to replace the old ones, shown to improve function in old mice. Photobiomodulation via near infrared light appears to modestly improve mitochondrial function, and visual function in older people, though how it does so remains to be determined. Long term low dose ethanol intake extends life modestly in mice and is suggested to do fo via improved mitochondrial function.

Among the better approaches to mitochondrial aging under development, the SENS Research Foundation is one of the few groups presently working on alloptic expression. This is the copying of mitochondrial genes into the cell nucleus in order to avoid the negative consequences of mitochondrial DNA damage. At present the consensus on the cause of mitochondrial DNA damage is learning towards it occuring during DNA replication rather than by interaction with reactive molecules. Not that all mitochondrial DNA damage is equal, as point mutations are well tolerated. It is more disruptive mutational damage that causes issues. Repair of that damage - or potentially allotopic expression to make the damage irrelevant - is a potential treatment for the aging of the heart.

NAD+ levels decline with age, and NAD+ upregulation improves mitophagy and mitochondrial function. For example, it reduces the burden of point mutations in mitochondrial DNA and slows female reproductive aging in mice. Loss of NAD+ is implicated in circadian rhythm dysfunction. There are many approaches to NAD+ upregulation, some dating back through decades of sporadic clinical trials, and none of which have yet been shown to increase NAD+ any more than is the case for structured exercise programs. This year saw new data for nicotinamide mononucleotide supplementation to improve neurovascular function and fertility in mice. Animal data on nicotinamide riboside supplementation also continues to be published: it improves the generation of immune cells in mice. Additionally, CD38 is becoming a target of interest related to NAD+ metabolism due to is role in degrading NAD, but it is a little early to say what sort of therapies might emerge to target CD38.

Age-Related Deafness

There is some debate over whether age-related hearing loss is caused by damage to sensory hair cells or via loss of the connections between those cells and the brain. Chronic inflammation is shown to be a significant factor in the risk and development of age-related hearing loss, as is loss of mitochondrial function. Hearing loss may contribute to the onset of dementia by depriving the brain of stimulation necessary for normal operation.

Blood Vessels and Blood Pressure

A reduction in the capacity to grow new blood vessels, and consequent loss of blood vessel density, takes place throughout the body with age, reducing blood supply, with negative consequences that are most noticable in energy-hungry tissues such as the brain, muscles, and especially the heart. It is noted that a better blood supply to the brain slows cognitive decline with age. Exercise can increase blood vessel density, at least in mice. Other approaches to achieve this goal presently under study focus on BMP6 and VEGF-B.

Raised blood pressure, hypertension, is one of the more harmful downstream consequences of the underlying molecular damage of aging. It causes structural damage to tissues, and aggressive control of blood pressure - without addressing the causes of hypertension - can rein in further downstream harm such as damage to the brain that accelerates cognitive decline. Indeed, early control of hypertension in later life reduces risk of dementia and atrial fibrillation. More intensive blood pressure reductions lead to a few year increase in life expectancy. This increase holds even in the most frail of elderly people. Further, gene variants associated with risk of hypertension also associate with reduced life expectancy.

Atherosclerosis is probably the worst thing to happen to blood vessels with age, in that it kills a sizable fraction of the population. By the time they are in their 40s, many people already have preclinical atherosclerosis, a study revealed this year. Atherosclerosis is driven by inflammation, and reducing chronic inflammation is as effective as lowering blood cholesterol in the treatment of the condition. There are numerous ways in which macrophages might be manipulated to slow or reverse atherosclerosis, given their role in clearing up damage to blood vessel walls. Some approaches published this past year include adjusting their polarization or encouraging them to greater clearance of debris in atherosclerotic plaque. Other approaches don't directly target macrophages, but do benefit them, such as cyclodextrin-containing nanoparticles that sequester harmful oxidized cholesterol. CD9 blockade appears to prevent senescence in endothelial cells, and was demonstrated to reduce progression of atherosclerosis in mice.

Parabiosis Research

Heterochronic parabiosis is the joining of two circulatory systems, an old and young animal. The young animal exhibits signs of accelerated aging, while the old animal exhibits signs of rejuvenation. Research initially focused on potential factors in young blood that might be producing benefits. Now however, evidence continues to emerge for the dilution of harmful factors in old blood to be the primary cause of benefits resulting from parabiosis. A few months ago, researchers demonstrated that plasma diluation reduces inflammation and improves cognitive function in old mice, and shortly thereafter self-experimenters ran a small human test based on this work, with intriguing signs of benefits.

Regenerative Medicine

The regenerative medicine community is focused on cell therapies to provoke greater regeneration, largely through signals secreted by the transplanted cells, rather than any significant integration of those cells. This is an area of research and development too large to do more than point out a few highlights and reviews, such as a discussion of the present state of mesenchymal stem cell therapies, reversal of photoaging via stem cell transplantation, or replacement of microglia or dopaminergenic neurons in the brain. Reprogramming is an interesting topic, when used to produce, say, patient-matched photoreceptor cells for transplantation to treat retinal degeneration, or neurons for transplantation as a stroke treatment. Reprogramming has of late been delivered in vivo, changing cells in living animals. This has been shown to improve cognitive function.

A great many stem cell therapies can in principle be replaced with the delivery of extracellular vesicles secreted by those stem cells. This is logistically easier to take to the clinic, is as effective where compared head to head, and thus an area of considerable activity at the moment. Examples of the potential of this approach are accumulating: stroke recovery via neural stem cell exosomes; a treatment for neurodegenerative conditions; a treatment for sarcopenia; a treatment of skin aging; a way to suppress senescent cell signaling.

Further, many regenerative therapies might in principle be replaced with treatments that restore native stem cell activity, which declines with age, or due to chronic inflammation. This is at least the case in people whose stem cell populations are not very damaged by aging. Such potential therapies are largely based on manipulation of cell signaling, such as Wnt signaling. A variety of such approaches were reviewed in the context of restoring muscle stem cell activity, a population known to largely retain its capabilities into later life, even while becoming quiescent. Secreted stem cell factors are proposed as a treatment for male pattern baldness. Lin28 upregulation and electrical stimulation can spur nerve regeneration. Lef1 upregulation enables skin regeneration without scarring, while protrudin gene therapy provokes regeneration in optive nerve.

There are other approaches, such as the guide nerve regrowth or heart tissue regrowth that would not normally have occurred. More cells survive for longer following transplantation if supported by a scaffold such as a heart patch, or if treated before transplantion with strategies such as mitochondrial transfer. Decellularization is another approach, using donor organs stripped of their cells. This can be done between species, as demonstrated by the production of tiny human livers from decellularized rat livers. Other unrelated work includes improving transplanted stem cell function via tethered signal molecules, improving mitochondrial function in neurons to cause greater regrowth, or using small bioprinters to print structured tissue directly into wounds.

Neurodegeneration

Neurodegeneration is a blend of many forms of damage and symptoms, not nice neat categories of disease. This is another area in which a great deal of work takes place, making any selection of that research something of a sampler plate. The risk of dementia is falling for any given individual, but total incidence is increasing because the population is increasingly older. The integrity of the blood-brain barrier declines with age, allowing harmful molecules and cells into the brain, where they can cause issues such as chronic inflammation. Other forms of vascular dysfunction also contribute, and are often reviewed in the literature. Inflammation due to the aging of the immune system is very much associated with neurodegenerative conditions such as Alzheimer's disease. Targeting mechanisms of inflammation to suppress it in brain tissue is considered a basis for the development of therapies, and is shown to slow the onset of neurodegeneration in animal models. Additionally, the presence of bacterial DNA appears to promote tau aggregation through mechanisms independent of the inflammation of infection. Persistent infection is hypothesized to contribute to Alzheimer's disease.

Mitochondrial decline led by a progressive disruption of the quality control mechanism of mitophagy are implicated in numerous neurodegenerative conditions. Impairment of the ubiquitin-proteasome system responsible for recycling proteins also appears relevant. Loss of myelin seems to have some negative effect in aging, as illustrated by the connection between declining oligodendrocyte production and failing memory, oligodendrocytes being the cells responsible for maintaining myelin. Thus it is interesting to note potential strategies to spur greater remyelination, such as PAR1 inhibition, theophylline use, and glial progenitor cell therapy. Researchers are looking for ways to improve mitochondrial function in neurons, to reverse the age-related loss that is linked to neurodegeneration. Activating ILC2 immune cells results in signaling that improves cognitive function, involving IL-5 and other yet to be identified molecules. HDAC1 activation improves DNA repair in neurons and slows cognitive decline. PTB inhibition converts astrocytes into neurons, reversing Parkinson's symptoms in mice. A fisetin variant, CMS121, has slowed disease progress in Alzheimer's mice. Parkinson's disease is splitting into two distinct conditions that converge on the same outcome. ISRIB treatment in old mice quickly restored youthful cognitive function, suggesting a large role for reversible cell signaling and cell state in neurodegeneration.

Amyloid-β remains an important target in the development of Alzheimer's therapies. The failure of immunotherapies targeting amyloid-β are not stopping the expansion of efforts to test immunotherapies targeting both amyloid-β and tau - tau being more harmful than amyloid-β. Not all amyloid plaques are the same; those containing nucleic acids may be worse and more inflammatory, thus potentially explaining differences between individuals who appear to have similar levels of plaque. Enhancing a natural process by which cells ingest and break down misfolded extracellular proteins might be a basis for treating neurodegenerative conditions in which protein aggregates are important. TREM2 antibodies are explored as a way to encourage greater microglia activity to clear molecular waste and treat Alzheimer's disease. Other groups are looking into sequestration of amyloid-β into nanoparticles.

While Leucadia Therapeutics and EnClear Therapies continue to progress towards their respective approaches to dealing with the clearance of molecular waste from cerebrospinal fluid, more evidence continues to arrive in support of the role of reduced cerebrospinal fluid drainage (and thus reduced removal of waste products from the brain) in the development of neurodegenerative conditions. It isn't just cerebrospinal fluid; blood drainage from the brain also slows with age, with consequences to brain structure.

Biomarkers of Aging

The assessment of biological age is a growing concern. It is widely recognized that some way of reliably testing biological age is necessary to speed development of therapies capable of rejuvenation, to separate the wheat from the chaff, and direct resources to the best outcomes. Setting aside a few initiatives to construct biomarkers of aging from simple assessments of frailty, much of the present focus is on clocks derived from epigenomic, transcriptomic, metabolomic, and proteomic data gathered from populations at different ages. There are even clocks based on protein glycosylation, antibody binding, and ionomic (elemental composition of tissue) patterns.

These clocks are proliferating and specializing but it remains the case that there is no connection between the clock and the underlying damage processes that it reflects. Thus there is no assurance that any given clock will in fact accurately measure the outcome of a therapy: each would have to be calibrated for each type of intervention, using life span studies. There is every reason to expect these clocks to only partially represent the full portfolio of age-related mechanisms, or exhibit odd quirks, such as an underestimation of age in later life, or heart tissue showing up younger than other tissues. Nonethless, clocks are starting to be used in clinical trials.

Meanwhile, the research continues. Pulmonary aging correlates with epigenetic age acceleration. A clock was developed for skeletal muscle tissue, two more using metabolomics and the plasma proteome, then the RNAAgeCalc transcriptional clock, and yet another new transcriptomic clock. Many of the clocks have been compared head to head in large study populations, and the GrimAge clock is coming out ahead in such comparisons. Recently a the more accurage DeepMAge clock was developed using machine learning approaches.

Mitochondrial DNA copy number correlates with epigenetic age. Exceptionally long-lived individuals exhibit slower epigenetic aging. Blood metabolites can be used as a marker of frailty. Work on protein biomarkers overlaps with work on senescent cells, as the SASP contains many molecules that might be used to mark the progression of aging, as represented by an increased burden of senescent cells. The rate of germline mutations and certain molecular changes in the lens of the eye may also protentially provide a way to assess the pace of aging. Circular RNAs may be a useful basis for a biomarker of aging.

Muscle Function

Follistatin gene therapy is still under investigation in animal models, and still shown to double muscle mass in mice. A more recent approach is DOK7 gene therapy, which regrows neuromuscular junctions to improve aged muscle function. Inhibition of mTORC1 also slows muscle aging via preservation of neuromuscular junctions. Further, CCR2 inhibition reduces inflammatory signaling to promote muscle regeneration in old mice, while upregulation of unacetylated ghrelin and 15-PGDH inhibition slows loss of muscle with age. Resistance training reliably improves muscle mass and strength in old people, and there are many ways to optimize this approach by combining training with various other interventions. Aerobic exercise boosts muscle stem cell activity. Molecular signals released by damaged muscle fibers promote muscle stem cell activity, for example.

Telomeres and Telomerase

Telomerase gene therapy is under development by a number of groups. It is considered a potential treatment for heart disease, among other age-related conditions. It may treat fibrosis via reducing the burden of senescent cells in old tissues. Other approaches to lengthening telomeres are under investigation, such as the use of small molecules to disrupt the balance of mechanisms in favor of more telomere lengthening activity in stem ells.

Cancer

Cancer research is a vast field, and there is always far too much to note. Mortality rates continue to fall. The most important areas of cancer research are those that are likely to give rise to treatments that can impact many or near all cancers with little to no per-cancer adjustment required. They must target universal mechanisms that cancers cannot evade. There are simply too many cancer types, and too much evolution within any given cancer, to make meaningful progress otherwise. This year, researchers have suggested targeting lipid metabolism to suppress metastasis, MR1 as a signature of cancerous cells, use of the small molecule NU-1 to inhibit telomerase activity, lipid nanoparticles carrying calicum phosphate and citrate, inhibition of mitochondrial DNA transcription, and TREM2 antibody therapy.

In other parts of the cancer field, chimeric antigen receptor immunotherapies are expanding to use in macrophages as well as T cells. The immune response to cancer changes with age in ways that are far from fully understood, making the development of immunotherapies a more complex proposition than would otherwise be the case. Researchers have shown that cancer treatment increases cancer risk for cancer survivors. This may be mediated by the creation of excess senescent cells.

Stress Response Mechanisms

In this age of comfort, low-cost calories, and machineries of transport, all too few people are as fit as they might be. Yet fitness and activity is one of the most reliable interventions to reduce age-related disease and mortality, in this world still lacking widespread and proven anti-aging therapies. Even light physical activity is significantly better than a sedentary lifestyle when it comes to mortality risk. Being sedentary raises the risk of cancer mortality. A healthier lifestyle at age 50 increases healthspan by nearly a decade. The data keeps on arriving to reinforce this point, year after year. Training for a marathon reverses some age-related vascular stiffness and hypertension. Exercise improves memory via increased blood flow, and also correlates with improved functional connectively in the brain. Exercise acts through Wnt signaling to slow brain aging and also helps T cells kill cancer cells. Physical activity is a treatment for frailty, can actually reverse frailty to some degree, and produces beneficial metabolic adaptations mediated by myokine signaling, such as increasing ubiquitination to clear damaged proteins from cells. Physical fitness correlates with a lesser decline in gray matter with age.

Calorie restriction is, of course, the other long-standing and well proven existing intervention that can reduce age-related disease and mortality. A great deal of thought has gone into why the calorie restriction response evolved early in the history of life. Data arrives every year to reinforce the small mountain of evidence that already exists in support of the health benefits. Calorie restriction reduces the harmful chronic inflammation of aging, perhaps largely by suppressing the inflammatory SASP of senescent cells. Intermittent fasting is also shown to be beneficial in human patients, improving biomarkers in metabolic syndrome, and improving chemotherapy effectiveness while reducing side effects. In mice, it increases neurogenesis and accelerates wound healing. Calorie restriction slows muscle aging in non-human primates, and reverses gene expression changes in old rats, even when started late. Calorie restriction also slows the aging of microglia in the brain and improves intestinal stem cell and intestinal barrier function.

Most, and I would say too much, of present research and development related to the treatment of aging is focused on upregulation of stress response mechanisms, in attempts to mimic the benefits of calorie restriction and exercise. This cannot have a large enough beneficial outcome to be worth the effort. It won't add decades to healthy life spans. Nonetheless, it is the largest portion of the field today. Upregulation of autophagy is arguably the most important of these stress responses. Indeed, if autophagy is inhibited, then accelerated aging result, such as increased T cell inflammatory activity. Impairment of autophagy occurs with aging, for reasons that include the presence of protein aggregates, and is implicated in loss of stem cell function. It contributes to osteoporosis.

Strategies noted in this past year to upregulate stress response mechanisms engaged by calorie restriction or exercise include sestrin upregulation, use of the small molecule nilotinib, cyclin D1 upregulation, injection of metformin rather than oral administration, mTORC2 activation, TAT peptide delivery, increased levels of β-hydroxybutyrate, intermittent treatment with rapamycin, which some feel should be widely prescribed, HNF4α inbition, use of metolazone, and overexpression of Gpld1. Other approaches that boost stress responses include PASK deficiency, cAMP upregulation, lowered body temperature, and induction of mitochondrial uncoupling, given a safe way to achieve that goal. It is also possible to create many of the effects of calorie restriction by restricting intake of only one essential amino acid, such as threonine. Aspirin, of course, is also a calorie restriction mimetic drug that improves health via autophagy.

Self-Experimentation

There is a small but energetic community of self-experimenters, interesting in assessing the outcomes of various strategies. I published a few notes on this topic over the past year. Firstly, an analysis as to why sex steroid ablation isn't a viable approach to thymus regeneration, at least not without a great deal more work on the part of the research community. Secondly, an outline for recreating a flagellin immunization study that was carried out in mice and noted to favorably adjust the gut microbiome. Other groups are trying to raise the bar on information for self-experimenters. Forever Healthy Foundation published a conservative risk-benefit analysis for the use of the dasatinib and quercetin senolytic combination.

Slowing Aging in Animal Models

Brd2 inhibition, astaxanthin based drugs, CDC42 inhibition via CASIN, low dose PPARγ agonist treatment, and overexpression of humanin have been found to slow aging in laboratory species for reasons that are either unclear, or involve many distinct mechanisms with little evidence for which are more or less important. In a case that is a little more cut and dried, mifepristone reduces innate immune driven inflammation in flies, slowing aging as a result.

Odds and Ends

There are always areas of research, some quite ambitious, some of it not, but nonetheless interesting, that don't quite fit into any of the usual buckets. This is a barnstorming era in biotechnology, in which it is possible to try all sorts of adventurous options to see if they can work, at least in principle. A selection follows. Increased expression of DICER has been suggested as a treatment for age-related macular degeneration as well as a way to improve the metabolic benefits of exercise in later life. Aging can be divided into "ageotype" categories based on how the common mechanisms develop into distinct patterns in different individuals. ELOVL2 upregulation reverses vision decline in aging eyes. Researchers have speculated that a downward trend in body temperature over the past few centuries reflects a lower burden of infection-driven inflammation, and thus is a feature linked to increased life expectancy.

Amyloid-β aggregation may be more than just a mechanism of Alzheimer's disease, but also a contributing cause of cardiovascular disease. Klotho is an area of interest because of its effects on aspects of aging. Recently delivery of soluable α-klotho was shown to reduce cardiac fibrosis in mice. The effects of klotho on life span may take place in part due to increased resistance to hypertension. Plasma transfer is an area of interest, in that transfer from young rats to old rats reduces measures of aging and senescent cell burden. A lower socioeconomic status correlates with faster age-related decline. Researchers have devised a way to provide photoreceptors with near-infrared sensitivity, as a way to restore light sensitivity in degenerating retina that have lost their normal visible light sensitivity, but retain cells able to function.

There is an age-related increase in CD47 expression that impairs vascular function, and inhibiting CD47 reverses this effect. Hyperbaric oxygen treatment may have some benefits, such as improved cerebral blood flow, but it doesn't seem likely that it truly reverses aging, such as via strong senolytic effects. Transcranial magnetic strimulation might be getting to the point of showing some reliable benefits to cognitive function in old people; the precise details of the technique used may be important, and thus few approaches will actually work. Thermoregulation is impaired by aging for reasons yet to be comprehensively explored. Despite failures of past years, some researchers continue to be interested in the use of laser light to break down harmful protein aggregates. Something like 30% to 40% of dementia might be avoided through better lifestyle choices. Increased insulin receptor expression improves memory in old rats. The story of C60 in olive oil came to a sad but predictable end. It is not in fact a viable was to slow aging, and the original study that suggested it was should be discarded.

Looking Ahead

Achieving healthy human longevity, a life that is vigorous and youthful in old age, is the challenge of our era. Work on the treatment of aging is expanding, but even though the old are becoming functionally younger, these are early years yet. Aging remains the largest and brightest unexplored new therapeutic frontier. Aging research should be a higher priority and enjoy far more funding given the prospects to improve the human condition - we should be trying to treat aging, and thereby improve many diseases, not continue treating the symptoms of aging on a disease by disease basis. Further, the future should involve a great deal more experimentation with combinations of therapies for aging. This is an underexplored area. Despite the promise of the field, a great deal of education and advocacy remains necessary: the public, and indeed many investors, cannot yet distinguish between scientific, unscientific, likely good and likely bad approaches to longevity. Those of us with a better idea of the nature of the field have a responsibility to spread our knowledge.

Some might hope that analysis of mortality data for elite athletes, largely meaning those who compete in professional events, could support an unambiguous relationship between physical fitness and longevity, and encourage more of us to be more active. Alas, nothing is simple in human health data. To start with, elite chess players, not noted for being a particularly athletic group, appear to gain much the same benefit to longevity as do the elite athletes. Thus perhaps this has more to do with socioeconomic status, or character traits such as drive and diligence that occur more often in professional sports participants, and also coincide with an overall better approach to long-term health practices. The open access paper here adds further depth to such discussions.

The positive effects of physical activity and recreational sports on health have been well-examined and are well-proven. In contrast, the consequences of extensive elite sports on life expectancy and mortality rates have been described in significantly less unique and comprehensive terms. here is a lack of models that systematically summarize the factors influencing the life span of elite athletes. Therefore, this study identifies the difference between all 6,066 German participants in Olympic Games between 1956 and 2016 and the total population.

An exposure group's mortality rates always show the sum of positive and negative factors effective at a specific measurement point in time in comparison to a control group. This means that the results are always preliminary. Nevertheless, since 1956, the sum of positive and negative effects of elite sports on the mortality of German Olympic participants appears to have been negative in comparison to the general population over 14 years old.

The lower mortality rates of elite athletes in most countries other than Germany compared to the respective country's general population could possibly be explained by the comparatively high life expectancy in Germany, as well as by the lower socioeconomic profit generated from a career in elite sports in Germany. This is also indicated by findings which show that German elite athletes generally have a lower life satisfaction compared to the overall population of the same age. The here presented study shows a negative influence on life span when participating in the Olympic Games several times and thus developing a high metabolism for a longer time. It also appears to be the case that previous studies compared the mortality of elite athletes with the total population, including infants. The higher infant mortality may, however, make the results appear more favorable for Olympic participants.

Link: https://doi.org/10.3389/fspor.2020.588204

This review paper contrasts two classes of approach to senolytic therapies that selectively target senescent cells for destruction. Inducing apoptosis in senescent cells by disrupting the balance between pro-apoptotic and anti-apoptotic signaling should be familiar to this audience, as it is the basis of some of the first senolytic drugs discovered, such as navitoclax. The other approach is more novel and less well explored, being the targeting of abnormalities in mitochondrial function that are peculiar to senescent cells. In order to be selective, any senolytic approach must exploit some difference between senescent cells and normal cells. It is interesting to see the list of those exploitable differences grow as researchers put more effort into mapping the biochemistry of cellular senescence.

Senescent cells with replicative arrest can be generated during genotoxic, oxidative, and oncogenic stress. Long-term retention of senescent cells in the body, which is attributed to highly expressed BCL-family proteins, chronically damages tissues mainly through a senescence-associated secretory phenotype (SASP). It has been documented that accumulation of senescent cells contributes to chronic diseases and aging-related diseases.

Despite the fact that no unique marker is available to identify senescent cells, increased p16INK4a expression has long been used as an in vitro and in vivo marker of senescent cells. We reviewed five existing p16INK4a reporter mouse models to detect, isolate, and deplete senescent cells. Senescent cells express high levels of anti-apoptotic and pro-apoptotic genes compared to normal cells. Thus, disrupting the balance between anti-apoptotic and pro-apoptotic gene expression, such as ABT-263 and ABT-737, can activate the apoptotic signaling pathway and remove senescent cells.

Mitochondrial abnormalities in senescent cells were also discussed, for example mitochondrial DNA mutation accumulation, dysfunctional mitophagy, and mitochondrial unfolded protein response (mtUPR). The mitochondrial-targeted tamoxifen, MitoTam, can efficiently remove senescent cells due to its inhibition of respiratory complex I and low expression of adenine nucleotide translocase-2 (ANT2) in senescent cells. Therefore, senescent cells can be removed by various strategies, which delays chronic and aging-related diseases and enhances lifespan and healthy conditions in the body.

Link: https://doi.org/10.3389/fphys.2020.593630

Many groups are attempting to develop calorie restriction mimetic drugs that produce benefits to health - and slow the progression of aging - by triggering some fraction of the stress response mechanisms engaged by the practice of calorie restriction. The most notable such mechanism is autophagy, a collection of cellular housekeeping processes that recycle damaged proteins and structures in the cell. Greater efficiency or activation of autophagy is a feature of a great many interventions known to slow aging in laboratory species.

Based on existing data, we should not expect any of these therapies to move the needle all that far on human life span, however. We have the example of calorie restriction, for which the health effects are fairly well known in human subjects. We also have aspirin, which is a calorie restriction mimetic, and is the subject of many very large human studies. Neither does all that much for life span in the grand scheme of things; a few years here, a few years there. We simply cannot expect novel calorie restriction mimetics to do more than modestly improve health and modestly reduce mortality, given this wealth of existing data that establishes the bounds of the possible for this approach to the treatment of aging.

Autophagy-mediated metabolic effects of aspirin

Aspirin is one of the oldest molecules to be used as a chemically defined entity for the treatment of human disease. Indeed, salicylate and its derivatives contained in plant extracts have been used since Mesopotamian times. As true for many other pharmaceutical agents, the effects of aspirin have been determined empirically to include anti-inflammatory, analgesic, and thrombosis-preventive effects before a molecular mode of action would have been postulated

Here, we investigated the metabolic effects of aspirin on the extracellular (plasma) and intracellular metabolome in mice by comparing them with those elicited by fasting. We and others have previously demonstrated that fasting or other caloric restriction mimetics than aspirin (such as spermidine and resveratrol) induce a broad deacetylation of multiple proteins involved in the regulation or execution of autophagy. We show that aspirin induces metabolic changes that are commensurate with the alterations produced by nutrient starvation, that it can indeed cause protein deacetylation in circulating white blood cells, that it inhibits EP300 but also other protein acetyltransferases, and that it mediates its positive metabolic effects through the induction of autophagy.

Indeed, the capacity of aspirin to reduce dietary adiposity, diabetes, and hepatosteatosis, as well as to enhance the efficacy of immunogenic chemotherapeutics, was lost in two distinct genetic mouse models of autophagy deficiency, as well as upon knockdown of Atg5 autophagy gene in cancer cells, respectively. Hence, the health-improving effects of aspirin depend on autophagy.

Cell signaling is vital to the metabolic and health benefits of exercise. Much of that signaling is carried by extracellular vesicles, tiny membrane-wrapped packages of molecules. Signaling taken as as a whole is a vast topic, and remains comparatively poorly mapped. Researchers are making incremental progress in the areas of greatest interest, those relating to response to cellular stress, in search of a basis for therapies that mimic some of the effects of calorie restriction, exercise, and other beneficial lifestyle choices and environmental factors.

The different physiological stimuli during physical exercise lead to an alteration of the extracellular vesicle (EV) landscape in blood. Research in humans was mainly focused on flow cytometric analysis of large EVs from platelets and endothelial cells, also called microparticles. The concentration of platelet microparticles increases during physical activity, starting at an early phase of exercise and reaching baseline few hours after the exercise session. Their release has been attributed to the activation of coagulative processes and shear stress. In contrast, abundance of endothelial microparticles varied between studies, but was reported as unchanged in most cases after exercise.

Recently, small extracellular vesicles (sEVs) have caught attention in the context of physical activity and an increasing number of studies addressed the release and their possible involvement in signaling pathways. Some studies in humans and rodents observed an immediate increase of sEVs after a single bout of physical exercise. One study found a direct reduction of total EV numbers, while detecting an increased population of muscle cell-derived EVs. Furthermore, elevation of resting EV levels were detected in response to long-term exercise interventions. sEVs released upon physical exercise (ExerVs) appear as a complex mixture of vesicles originating from platelets, endothelial progenitor, or endothelial cells, leukocytes, and muscle cells, which most probably varies depending on exercise mode and time of investigation.

Analysis of the protein cargo of ExerVs identified various proteins associated with key signaling pathways, including angiogenesis, immune signaling, and glycolysis. Additionally, the secretion and transport of myokines via ExerVs was suggested. Moreover, several studies found evidence for the transport of an altered miRNA panel via sEVs in response to exercise bouts or training. Some of the miRNAs carried by ExerVs belong to the group of myomirs indicating involvement of EVs in muscle regeneration processes following exercise. Functional analysis of ExerVs suggested contribution to cardio protection in ischemia / reperfusion-injury, hypoxia / reoxygenation-assays, tissue remodeling, endothelial function, as well as muscle remodeling and growth, potentially mediated by ExerV-cargo transported in response to exercise stimuli.

Overall, these studies provide evidence that sEVs are actively released into the circulation upon physical exercise and may function as mediators of different key signaling pathways, possibly involved in adaptation processes triggered by exercise.

Link: https://doi.org/10.3389/fphys.2020.576150

Cell signaling is carried far and wide in the body via the bloodstream. The molecules involve change significantly with age, including a rise in inflammatory signaling and consequent chronic inflammation. This is a reaction to, or consequence of, forms of damage involved in aging, but it is also a source of significant further dysfunction. That much is demonstrated by plasma dilution studies, in which improved tissue function in several organs is noted as a result of diluting the signals carried by the bloodstream in an aged body.

Traditional indicators of biological age are not always informative and often require extensive and expensive analysis. The study of blood factors is a simple and easily accessible way to assess individual health and supplement the traditional indicators of a person's biological age with new objective criteria. With age, the processes of growth and development, tissue regeneration and repair decline; they are gradually replaced by enhanced catabolism, inflammatory cell activity, and insulin resistance. The number of senescent cells supporting the inflammatory loop rises; cellular clearance by autophagy and mitophagy slows down, resulting in mitochondrial and cellular damage and dysfunction. Monitoring of circulated blood factors not only reflects these processes, but also allows suggesting medical intervention to prevent or decelerate the development of age-related diseases.

Blocking factors that negatively affect lifespan is a reasonable strategy to prevent early disability and prolong the active life of older people. Among such strategies, tested in the clinical practice or which will be translated to the clinical practice, one can highlight overcoming the insulin resistance by diet restriction, increasing FGF21 in blood circulation, pharmacological treatment of insulin resistance (e.g., with dehydroepiandrosterone and metformin), stimulation of tissue repair by GH, oxytocin, GDF11, and TIMP2, vascular regeneration with bFGF, EGF, VEGF, PDGF-AB, and BMP9, preventing the development of "inflammaging" by administering anti-inflammatory molecules, including COX-2 inhibitors, leukotriene receptor antagonists, TIMP2, or other matrix metalloproteinase inhibitors, overcoming the cell senescence by administration of TM5441 analogs, optimizing the autophagy and mitophagy with mTOR inhibitors, with TGF-β inhibitors, antioxidant therapy, reduction of NAD+ exhaustion. The indicators and mechanisms discussed above reflect the natural and pathological aging processes.

Link: https://doi.org/10.3390/biomedicines8120615

Today's research materials discuss an interesting aspect of cancer epidemiology. Cancer survivors exhibit a greater risk of developing later primary cancers, unconnected to the prior cancer, and in addition suffer a greater mortality than first time cancer patients with those same cancer types. There are a number of possible explanations for this data, two of which are noted below. The data leans strongly towards the first of the two.

Firstly, cancer risk is driven by specific mechanisms of aging: a faltering immune system, unable to stop cancers in their earliest stages by killing precancerous cells efficiently enough; greater chronic inflammation, spurring faster growth of cancerous tissue; greater levels of DNA damage and clonal expansion of mutations throughout tissue. People who have cancer will, on balance, be more damaged and more aged than those who do not have cancer. Thus they will continue to have a higher risk in the future. Picking people who have already survived cancer is a way of selecting for individuals who have, on average, a greater burden of age-related damage and other pro-cancer mechanisms and circumstances, such as obesity or a smoking habit.

Secondly, the treatment of cancer is inherently damaging in and of itself. The most commonly used cancer therapies, chemotherapy and radiotherapy, produce a sizable increase in the number of lingering senescent cells in the body as a side-effect of killing cancerous tissues. Stressed, damaged cells that do not die will become senescent, and the aged immune system present in most cancer patients will not efficiently destroy those senescent cells. Senescent cells secrete an inflammatory, pro-growth mix of signals that makes future cancers that much more likely, and indeed accelerate progression of all of the other aspects of aging as well. Surviving chemotherapy is about as bad for your long-term health as a robust smoking habit, when looking at the mortality data.

Study finds cancer survivors run greater risk of developing, dying from second cancers

A new study finds that adult-onset cancer survivors run a greater risk of developing and dying from subsequent primary cancers (SPCs) than the general population. Cancers associated with smoking or obesity comprised a majority of SPC incidence and mortality among all survivors. For the study, investigators analyzed data on nearly 1.54 million cancer survivors from 1992 to 2017 from 12 Surveillance, Epidemiology, and End Results registries in the United States. The findings suggest that among the 1,537,101 survivors, 156,442 were diagnosed with an SPC and 88,818 died of an SPC. Results found that male survivors had an 11% higher risk of developing SPCs and a 45% higher risk of dying from SPCs compared with the risk in the general population. Female survivors had a 10% higher risk of developing SPCs and a 33% higher risk of dying from SPCs.

Results show the risks of smoking-related SPCs were commonly elevated among survivors of smoking-related first cancers. Among survivors of all cancers, four common smoking-related SPCs including lung, urinary bladder, oral cavity/pharynx, and esophagus, accounted for 26% to 45% of the total SPC incidence and mortality. Furthermore, lung cancer alone comprised 31% to 33% of the total mortality from SPCs. Similarly, survivors of many obesity-related cancers had an elevated risk of developing obesity-related SPCs. Among survivors of all cancers, four common obesity-related cancers colorectum, pancreas, corpus uteri, and liver, comprised 22% to 26% of total SPC mortality.

Association of First Primary Cancer With Risk of Subsequent Primary Cancer Among Survivors of Adult-Onset Cancers in the United States

The objective of this study is to quantify the overall and cancer type-specific risks of subsequent primary cancers (SPCs) among adult-onset cancer survivors by first primary cancer (FPC) types and sex. Among 1,537,101 survivors (mean age, 60.4 years; 48.8% women), 156,442 SPC cases and 88,818 SPC deaths occurred during 11,197,890 person-years of follow-up (mean, 7.3 years). Among men, the overall risk of developing any SPCs was statistically significantly higher for 18 of the 30 FPC types, and risk of dying from any SPCs was statistically significantly higher for 27 of 30 FPC types as compared with risks in the general population. Among women, the overall risk of developing any SPCs was statistically significantly higher for 21 of the 31 FPC types, and risk of dying from any SPCs was statistically significantly higher for 28 of 31 FPC types as compared with risks in the general population.

The highest overall standardized incidence ratio (SIR) and standardized mortality ratio (SMR) were estimated among survivors of laryngeal cancer (SIR, 1.75; incidence, 373 per 10,000 person-years) and gallbladder cancer (SMR, 3.82; mortality, 341 per 10,000 person-years) among men, and among survivors of laryngeal cancer (SIR, 2.48; incidence, 336 per 10,000 person-years; SMR, 4.56; mortality, 268 per 10,000 person-years) among women. Substantial variation existed in the associations of specific types of FPCs with specific types of SPC risk; however, only a few smoking- or obesity-associated SPCs, such as lung, urinary bladder, oral cavity/pharynx, colorectal, pancreatic, uterine corpus, and liver cancers constituted considerable proportions of the total incidence and mortality, with lung cancer alone accounting for 31% to 33% of mortality from all SPCs.

Among survivors of adult-onset cancers in the United States, several types of primary cancer were significantly associated with greater risk of developing and dying from an SPC, compared with the general population. Cancers associated with smoking or obesity comprised substantial proportions of overall SPC incidence and mortality among all survivors and highlight the importance of ongoing surveillance and efforts to prevent new cancers among survivors.

In recent years, transposable element activation has come to be seen as potentially important in aging. Transposable elements such as retrotransposons are DNA sequences that can copy themselves into other locations in the genome, potentially causing all sorts of disruption. These transposable elements are repressed in youth by epigenetic mechanisms such as DNA methylation, but become more active in aging. It is unclear as to the degree that this represents a rising burden of damaged and senescent cells, in which transposon activity is a part of their dysfunction, versus a more general issue across all cells that causes greater damage and senescence. Here, researchers focus on the LINE-1 retrotransposons, looking at cell-free DNA in circulation, the debris from destroyed cells, to see whether there is a clear association between the state of epigenetic marks on LINE-1 retrotransposons and the progression of aging.

LINE-1 hypomethylation, a loss of DNA methylation in the CpG-rich promoter sequences of Long Interspersed Nuclear Elements retrotransposons, occurs as "genome-wide" or "global" DNA hypomethylation in many cancer types. LINE-1 hypomethylation is therefore one of the characteristic methylation profile changes common to many cancers. LINE-1 hypomethylation often leads to LINE-1 activation, i.e., expression of LINE-1 RNA and proteins, including its potent endonuclease. This activation may elicit DNA damage and repair, stress responses, tumor progression and apoptosis, especially if additional cellular retrotransposition control mechanisms have been overcome.

Interestingly, a gradual loss of LINE-1 methylation has also been observed during aging that may likewise derepress silenced LINE-1 retroelements followed by increased genomic instability. Aging is known as a main risk factor for cancer. In this regard, we had provided additional evidence that genome-wide hypomethylation of LINE-1 retroelements in cell-free DNA (cfDNA) in blood is an epigenetic biomarker of human aging. Recently, it has been shown that LINE-1 sequences are a major component of circulating cfDNA. This finding suggests the idea that cfDNA may originate in aging or tumor cells afflicted by LINE-1 hypomethylation. Such cells would have a significantly elevated rate of LINE-1 activation and retrotransposition, affecting genomic integrity. Ultimately, this could result in apoptosis and release of their LINE-1-enriched cfDNA.

Here we present a new methodological strategy to properly and unambiguously extract DNA methylation patterns of repetitive, as well as single genetic loci from pure cell-free DNA from peripheral blood. Since this nucleic acid fraction originates mainly in apoptotic, senescent, and cancerous cells, this approach allows efficient analysis of aged and cancerous cell-specific DNA methylation patterns for diagnostic and prognostic purposes. Using this methodology, we observe a significant age-associated erosion of LINE-1 methylation in cfDNA suggesting that the threshold of hypomethylation sufficient for relevant LINE-1 activation and consequential harmful retrotransposition might be reached at higher age. We speculate that this process might contribute to making aging the main risk factor for many cancers.

Link: https://doi.org/10.1038/s41598-020-79126-z

The open access paper here is a good companion to yesterday's review of what is know of the way in which chronic inflammation disrupts hematopoiesis. Hematopoiesis is the complex process by which hematopoietic stem cells in the bone marrow produce blood and immune cells, vital to the function of the immune system. The immune system becomes overactive in later life, pushed into a constant state of low grade inflammation by the damage of aging and its consequences, such as rising numbers of senescent cells that produce inflammatory signaling. This chronic inflammation causes dysfunction in hematopoiesis, thus further harming immune function.

In the skeletal system, vasculature plays a crucial role in nutrient delivery and maintenance of the resident stem cells and progenitor cells that regulate osteogenesis and hematopoiesis. Bone marrow (BM) harbors stem and progenitor cells of different lineages including hematopoietic and mesenchymal stem cells that differentiate into a variety of mature functional cells, contributing to osteogenesis and hematopoiesis. These stem and progenitor cells reside in specialized local microenvironments within the BM, known as BM niches. BM niches provide crucial signals for stem and progenitor cell survival, quiescence, mobilization, and differentiation. These signals come in the form of soluble factors, cell surface ligands, or cell-to-cell interactions which regulate stem and progenitor cell fates.

The BM microenvironment is highly sensitive to stress. Growing evidence suggests that stress-induced molecular changes of the BM microenvironment disrupt homeostasis. BM endothelial cells (ECs) and their secreted factors, called angiocrine factors, regulate hematopoietic stem and progenitor cell homeostasis and function. Stress associated with aging, inflammation, bone diseases, or bone malignancies can disrupt vascular morphology and angiocrine signaling, with significant impacts on osteogenesis, bone angiogenesis, and hematopoiesis.

The response of the BM microenvironment to stressful conditions and diseases has received increased attention over the past few years. Nevertheless, the knowledge about the effects of stress on the BM microenvironment remains incomplete and is a hot topic of research. This review aims to define the cellular and molecular response of the BM vascular niche to different stresses by comparing the BM vascular niches in homeostasis and under various stress conditions such as aging, inflammation, and malignancy.

Link: https://doi.org/10.3389/fcell.2020.602269

Hematopoiesis is the generation of blood and immune cells that takes place in the bone marrow, conducted by an array of stem cell and progenitor cell populations that are differentiated from hematopoietic stem cells, a tree of subpopulations with differing tasks that together contribute to the overall outcome. Nothing in biology is simple, and hematopoiesis is a complex, dynamic process governed by many interacting regulatory mechanisms. Hematopoietic cells respond to signals from other tissues, and particularly to the activities of the immune system, such as the inflammatory signals that arise when immune activity is needed. This complexity of feedback mechanisms is well known, but far from completely mapped. For example, it is thought that the thymus, the organ in which thymocytes created in the bone marrow mature into T cells of the adaptive immune system, can influence hematopoiesis, but it is unclear as to how exactly this cross-talk occurs.

Hematopoiesis becomes altered with age, both faltering in the output of immune cells, and becoming biased to the production of myeloid rather than lympoid cells. This progressive deterioration is an important contribution to the age-related decline of the immune system. As today's open access paper notes, the age-related dysfunction of the immune system is in fact a contributing cause of these problems in hematopoiesis. With age, the immune system falls into a state of chronic inflammation, constantly roused to inappropriate activation and generation of inflammatory signals. The causes of this inflammatory state include persistent infections, metabolic waste, excess visceral fat, and rising numbers of senescent cells. Chronic inflammation is disruptive of tissue function throughout the body, and bone marrow and its hematopoietic cell populations are among those negatively affected.

Immuno-Modulation of Hematopoietic Stem and Progenitor Cells in Inflammation

Lifelong blood production is maintained by bone marrow (BM)-residing hematopoietic stem cells (HSCs) that are defined by two special properties: multipotency and self-renewal. Since dysregulation of either may lead to a differentiation block or extensive proliferation causing dysplasia or neoplasia, the genomic integrity and cellular function of HSCs must be tightly controlled and preserved by cell-intrinsic programs and cell-extrinsic environmental factors of the BM.

Since the initial establishment of the hematopoietic differentiation tree, our understanding of the hematopoietic system, and of the HSC population situated at its apex undergoes continuous refinement. Formerly presumed unresponsive to tissue insult, HSCs in fact show high adaptability under various scenarios and actively cooperate with downstream hematopoietic progenitors, mature cells, and environmental stromal cells as frontline responders to preserve blood homeostasis. However, their ability to respond deftly through self-renewal and differentiation at times brings about detrimental consequences.

It is now clear that the BM is not immune-ignorant but a prominent lymphoid organ that receives a large spectrum of hemato-immunological insults. Likewise, BM-residing HSCs are not just quiescent sleeping cells but directly respond to insults not limited to infection and inflammation but also the regeneration of the BM after toxic agents or irradiation. Depending on the type of DAMPs, PAMPs, cytokines, and growth factors involved and the strength and duration of the stimulation, HSCs will alter their fate toward myelopoiesis, granulopoiesis, or even bypass progenitors altogether to directly orchestrate on-demand hematopoiesis. HSCs positioned at the interface of perturbed hematopoiesis will execute distinct emergency programs to integrate and fine-tune responses to maintain hematopoietic integrity.

However, such beneficial effects of HSC activation can be counteracted by chronic inflammatory conditions. HSC dysfunction upon chronic inflammation or aging as the cause of clonal hematopoiesis and in certain cases leukemic transformation are all readily imaginable scenarios, although direct causality remains to be demonstrated.

Many approaches to stem cell therapy might be replaced in the years ahead by delivery of exosomes secreted by those stem cells. Most cell therapies produce benefits via the signals generated by the transplanted cells. Those signals produce beneficial changes in the behavior of native cells, such as suppression of inflammation or greater tissue maintenance activities. Without extensive engineering of supporting structures the transplanted cells survive only for a short time. Thus why not just deliver the signals? A sizable fraction of cell signaling is delivered via extracellular vesicles such as exosomes, membrane-wrapped packages of signal molecules that pass between cells. Harvesting exosomes from cell cultures for use in therapy is logistically easier than building cell therapies, and thus a great many research groups and companies are presently working on regenerative therapies based on delivery of natural or modified exosomes.

Despite the recent advances in the biology of neurodegenerative diseases, these disorders remains incurable, and most of the existing drugs provide only symptomatic relief and do not affect the progression of the disease. For this reason, there is a pressing need to identify alternative therapies to treat these disorders. Therefore, there is an urgent need for new treatments for these diseases, since the World Health Organization has predicted that neurodegenerative diseases affecting motor function will become the second-most prevalent cause of death in the next 20 years.

In this sense, cell therapy, using stem cells, has been recognized as the best candidate for treating incurable diseases, including neurodegenerative disorders. However, in the last decade, accumulating evidence supports the idea that mesenchymal stem cells (MSCs) perform their therapeutic roles in a paracrine manner. For a long time, it was considered that the therapeutic effects of the stem cells were associated with the replacement of dead cells. However, in a model of kidney injury it was verified that transplanted stem cells remain in the injury site up to a few days only, and, subsequently, are not found in the tissue. Similar results were observed in subsequent studies.

Altogether, these data suggest that the therapeutic effects of MSCs are mediated by their "secretome", which is composed of a spectrum of protective bioactive molecules, which are comprised of anti-inflammatory cytokines, growth factors, neuronal factors, and antioxidants. The rediscovery that cells secrete a plethora of factors into nanosized vesicles surrounded by a lipid bilayer membrane (extracellular vesicles) has allowed exploring the therapeutic use of these vesicles in a novel therapeutic modality known as cell-free therapy.

The class of extracellular vesicle known as exosomes emerge as a promising therapeutic approach for neurodegenerative diseases. This is because, due to their nano-sized diameter, the exosomes can cross the blood brain-barrier, acting as carriers of bioactive molecules naturally secreted by their derived cells, or they can be engineered as carriers of drugs. Despite the evidence of the benefits of cell-free therapy for neurodegenerative diseases, efforts are necessary to improve the available exosome isolation methodologies in order to realize scalable vesicles production for clinical purposes. In addition, it is also crucial to provide guidelines for studying these vesicles in order to guarantee acceptance criteria by regulatory agencies.

Link: https://doi.org/10.3390/cells9122663

Evidence has accumulated in recent years for the accumulation of senescent cells in aged tissues to be an important driver of fibrosis, particularly the evidence resulting from studies that employed senolytic therapies to selectively destroy sensescent cells and thereby reverse fibrosis. Fibrosis is a malfunction of tissue maintenance, in which cells deposit excessive collagen to form scar-like structures that disrupt organ function. There is comparatively little that can be done to treat patients with fibrotic disease at present, and so there is considerable interest in any new path to therapy. Senescent cells secrete pro-inflammatory, pro-growth factors, and thus they are the prime suspects in many disruptions of normal tissue maintenance processes.

Aging is an inevitable and complex natural phenomenon due to the increase in age. Cellular senescence means a non-proliferative but viable cellular physiological state. It is the basis of aging, and it exists in the body at any time point. Idiopathic pulmonary fibrosis (IPF) is an interstitial fibrous lung disease with unknown etiology, characterized by irreversible destruction of lung structure and function. Aging is one of the most critical risk factors for IPF, and extensive epidemiological data confirms IPF as an aging-related disease.

Senescent fibroblasts in IPF show abnormal activation, telomere shortening, metabolic reprogramming, mitochondrial dysfunction, apoptosis resistance, autophagy deficiency, and senescence-associated secretory phenotypes (SASP). These characteristics of senescent fibroblasts establish a close link between cellular senescence and IPF. The treatment of senescence-related molecules and pathways is continually emerging, and using senolytics eliminating senescent fibroblasts is also actively tried as a new therapy for IPF.

Link: https://doi.org/10.3389/fcell.2020.593283

The open access papers I'll point out today are but two among many similar publications, in which researchers catalog ever more of the age-related changes in omics data that take place in mice. The omics fields cover measurement and analysis of data related to the genome, epigenome, transcriptome, proteome, metabolome, and then specific subsets of these sizable volumes of data, such as the secretome of specific cell types. The genome is the DNA of a cell, the epigenome the regulatory chemical additions to the genome that govern gene expression. The transcriptome is the set of RNA transcripts produced by a cell at any given time, and the proteome the proteins presently circulating or found within specific cells. The metabolome is the broader set of molecules circulating in the body, not all of which are manufactured by cells.

Technological progress of the past few decades has resulted in a rapid increase in capability and reduction in cost in omics technologies. Enormous amounts of data are easily obtained, and are indeed constantly obtained by many research groups, but analysis and synthesis remain challenging. These latter efforts are now the bottlenecks to progress in this part of the field. It is one thing to better measure the details of a young organism and an old organism in order to flag the differences at the molecular level. It is quite another thing to make sense of that data, to arrange it into cause and consequence, to identify processes that produce the observed results, to move from observation to proposed therapy. Comparatively little has been accomplished on that latter front, as illustrated by the point that epigenetic (or transcriptomic, or proteomic) clocks that correlate with age and mortality risk are well established, but no-one can yet explain exactly why these epigenetic changes are associated so closely with the process of becoming old.

Tissue-specific Gene Expression Changes Are Associated with Aging in Mice

Aging is a complex process that can be characterized by functional and cognitive decline in an individual. Aging can be assessed based on the functional capacity of vital organs and their intricate interactions with one another. Thus, the nature of aging can be described by focusing on a specific organ and an individual itself. However, to fully understand the complexity of aging, one must investigate not only a single tissue or biological process but also its complex interplay and interdependencies with other biological processes.

Here, using RNA-seq, we monitored changes in the transcriptome during aging in four tissues (including brain, blood, skin and liver) in mice at 9 months, 15 months, and 24 months, with a final evaluation at the very old age of 30 months. We identified several genes and processes that were differentially regulated during aging in both tissue-dependent and tissue-independent manners. Most importantly, we found that the electron transport chain (ETC) of mitochondria was similarly affected at the transcriptome level in the four tissues during the aging process. We also identified the liver as the tissue showing the largest variety of differentially expressed genes (DEGs) over time. Lcn2 (Lipocalin-2) was found to be similarly regulated among all tissues, and its effect on longevity and survival was validated using its orthologue in Caenorhabditis elegans.

In conclusion, our study demonstrated that the molecular processes of aging are relatively subtle in their progress, and the aging process of every tissue depends on the tissue's specialized function and environment. Hence, individual gene or process alone cannot be described as the key of aging in the whole organism.

Mouse Age Matters: How Age Affects the Murine Plasma Metabolome

A large part of metabolomics research relies on experiments involving mouse models, which are usually 6 to 20 weeks of age. However, in this age range mice undergo dramatic developmental changes. Even small age differences may lead to different metabolomes, which in turn could increase inter-sample variability and impair the reproducibility and comparability of metabolomics results. In order to learn more about the variability of the murine plasma metabolome, we analyzed male and female C57BL/6J, C57BL/6NTac, 129S1/SvImJ, and C3HeB/FeJ mice at 6, 10, 14, and 20 weeks of age, using targeted metabolomics.

Our analysis revealed high variability of the murine plasma metabolome during adolescence and early adulthood. A general age range with minimal variability, and thus a stable metabolome, could not be identified. Age-related metabolomic changes as well as the metabolite profiles at specific ages differed markedly between mouse strains. This observation illustrates the fact that the developmental timing in mice is strain specific. We therefore stress the importance of deliberate strain choice, as well as consistency and precise documentation of animal age, in metabolomics studies.

The growing interest in manipulating aspects of metabolism related to aging is still largely focused on the range of cell maintenance mechanisms that are triggered into greater operation by calorie restriction and other stresses. Efforts are underway to discover existing approved drugs that have a large enough effect on these mechanisms to be repurposed as therapies to slow aging. This type of initiative does has the potential to produce important discoveries, such as the first senolytic drugs capable of selectively destroying senescent cells. But where it focuses on upregulation of cell maintenance processes such as autophagy or the unfolded protein response, it seems unlikely to produce more than incrementally beneficial outcomes. We know what the practice of calorie restriction or exercise can achieve in humans via these stress response mechanisms, meaning a healthier old age but only a few additional years of life. Mimicking a fraction of these processes is not going to be capable of greatly changing the shape of a human life.

Researchers know that mitochondria play an important role in aging. Specifically, when mitochondria are harmed in some way and their function is impaired, a process called mitochondrial unfolded protein response (UPRmt) occurs that repairs mitochondria and benefits cell survival. Therefore, some scientists think it is possible to increase lifespan by identifying drugs that activate UPRmt. A team of scientists searched through a chemical library of existing drugs to find one that can activate this stress response in the worm Caenorhabditis elegans. They found that an anti-hypertension drug called metolazone prolongs C. elegans lifespan, marking the first step in developing anti-aging pharmaceuticals.

Past experiments with Caenorhabditis elegans - a worm commonly used in biological research as a model - have found several compounds that increase the worm's lifespan by triggering UPRmt. Against the backdrop of these previous studies, this team screened about 3,000 drugs in worms that are engineered to glow if drug treatment activates hsp-6, a gene that is highly expressed when UPRmt occurs. It is interesting to note that of these 3000 drugs, 1300 were off-patent drugs approved by regulatory agencies, and the remaining 1700 were unapproved bioactive ones.

Through this method, the team identified metolazone, a drug used to treat heart failure and high blood pressure. They then tested the drug on C. elegans and found that it increased wild-type worm lifespan. Additionally, they found that metolazone did not extend lifespans in worms in whom the genes atfs-1, ubl-5, and nkcc-1 were mutated and thus non-functional. The former two genes are known to be essential for UPRmt function, suggesting that metolazone is acting on the UPRmt pathway. The third gene, nkcc-1, encodes a protein that is part of a protein family targeted by metolazone in its usual function as an anti-hypertension drug. The fact that metolazone did not increase the lifespans of nkcc-1 mutated C. elegans suggests that the drug may need to block the nkcc-1 protein to activate the UPRmt pathway.

Link: https://www.osaka-cu.ac.jp/en/news/2020/blood-pressure-drug-may-be-key-to-increasing-lifespan-new-study-shows-1

Researchers here note an approach to destructively destabilizing the metabolism of cancer cells via lipid nanoparticle delivery of calcium phosphate and citrate. The precise details of the mechanisms by which cancer cells are specifically vulnerable to this mode of delivery, while normal cells essentially reject the nanoparticles, are presently unknown. That will likely limit the further development of this approach to therapy until there is a greater understanding of how exactly it works, even given the promising initial results in mice.

Researchers have developed a novel type of nanoparticle that efficiently and selectively kills cancer cells, thus opening up new therapeutic options for the treatment of tumors. Both calcium phosphate and citrate are involved in the regulation of many cellular signaling pathways. Hence, the levels of these substances present in the cytoplasm are tightly controlled, in order to avoid disruption of these pathways. Crucially, the nanoparticles described in the new study are able to bypass these regulatory controls. Researchers repared amorphous and porous nanoparticles consisting of calcium phosphate and citrate, which are encapsulated in a lipid layer. The encapsulation ensures that these particles are readily taken up by cells without triggering countermeasures. Once inside the cell, the lipid layer is efficiently broken down, and large amounts of calcium and citrate are deposited in the cytoplasm.

Experiments on cultured cells revealed that the particles are selectively lethal - killing cancer cells, but leaving healthy cells (which also take up particles) essentially unscathed. During cellular uptake, the nanoparticles acquire a second membrane coat. The authors of the study postulate that an unknown mechanism - which is specific to cancer cells - causes a rupture of this outer membrane, allowing the contents of the vesicles to leak into the cytoplasm. In healthy cells, on the other hand, this outermost layer retains its integrity, and the vesicles are subsequently excreted intact into the extracellular medium.

"The highly selective toxicity of the particles made it possible for us to successfully treat two different types of highly aggressive pleural tumors in mice. With only two doses, administered locally, we were able to reduce tumor sizes by 40 and 70%, respectively. Furthermore, over the course of a 2-month treatment, no signs of serious side-effects were detected."

Link: https://www.en.uni-muenchen.de/news/newsarchiv/2020/engelke_nanoparticles.html

Today's news from the self-experimentation community notes a more adventurous effort, in which a few volunteers underwent blood plasma dilution followed by assessments of function. Plasma dilution, or neutral blood exchange, involves extracting blood, replacing the plasma fraction of that blood with saline and albumin, then reintroducing the new mix. The effect is a dilution of the circulating plasma and all that it contains. For most people this procedure is past the outer limits of practicality as a self-experiment. It requires a good amount of scientific or medical knowledge, familiarity with the latest research on the topic, and cooperative physicians.

Plasma dilution as a treatment to favorably adjust the age-damaged operation of metabolism is one of the more interesting outcomes of heterochronic parabiosis research. In a heterochronic parabiosis study, old and young mice have their circulatory systems linked. The old mice show signs of reversed aging, while the young mice show signs of accelerated aging. Is this because of factors in young blood that improve the function of old tissues, or is it because old blood is packed with damaging factors that impair tissue function?

It may be both, but the most compelling evidence points to old blood being full of actively harmful molecules, such as debris from damaged cells, the inflammatory signaling of senescent cells, and so forth. Diluting these signals restores a better operation of tissue throughout the body - at least in mice. Formal human trials lie somewhere in the years ahead, but the volunteers noted here are to be commended for responsibly stepping up to try the procedure and publish their data. It would be a better world were more of the self-experimentation community as competent in their efforts.

Biohackers Perform First Plasma Dilution Experiment on Humans

How did your group first get interested in the idea of plasma dilution? I understand that Irina Conboy's work had a certain influence?

Not just influence. It played a central role. The Conboys' study was published in May. It showed that simple plasma dilution can recapitulate most of the benefits of parabiosis. The original parabiosis results hinted on the existence of certain systemic factors of aging and at the possibility of its reversal. This recent study made the procedure easier and eliminated ethical controversies. The procedure is almost similar to donating blood plasma. This simple procedure yielded some interesting results: it triggered muscle regeneration in mice, liver regeneration in older animals, and improved neurogenesis. Recently, in late November, I think, another study was published that showed some real cognitive improvement following this procedure. So, now we have some serious proof that blood contains signaling molecules that harm the organism, but there is no data on whether this procedure actually prolongs lifespan. I think there is a reason for it. It is highly unlikely that this procedure results in any meaningful life extension. I think most of the effect is on healthspan rather than on lifespan. It is still good news, since we currently have very few ways to extend healthspan.

Why did you decide to participate in this small-scale experiment on humans?

Our team has existed for some time now. It is a small community of biohackers. It seemed like a great way to quickly test this intervention, get some results fast, and tell people about it.

How did you choose the tests for the panel?

It would have been interesting to look at cognitive and muscular markers, but both our participants were too young: 50-60 years old. They probably do not have sarcopenia or cognitive decline yet, so there was no way for us to measure it. We chose different biomarkers, such as liver function - both of our participants had had some abnormalities in their liver biomarkers. We wanted to check kidney function because it declines with age. We checked the immune system, because as we age, the number of naïve T cells declines, and these are indispensable for fighting new infections. Hematopoietic cell aging is characterized by a shift towards myeloid progenitors. We looked at the ratio of neutrophils and lymphocytes, how it changed. Cholesterol is another important marker in the lipid profile of blood. We did a very comprehensive lipid profile that included a rare biomarker that many labs do not check for - oxidized low-density lipoproteins (Ox-LDL). I can say that this marker plummeted all the way down to its normal level in one participant that had it elevated prior to the procedure. We also checked for various hormones, including insulin-like growth factor (IGF), that are related to aging and lifespan, and many other markers, including biochemical ones, such as urea and uric acid, along with oxidative stress markers, such as lipid peroxidation products and glutathione. Contrary to epigenetic clocks, these markers can be clinically interpreted.

Do you plan to publish the results, maybe as a case study?

We have all the data published on our website so that researchers can see it. We do not plan to publish an article. First, I am convinced that soon we will have full-scale clinical trials of this method, maybe by the Conboys, and there is something in the works here in Russia as well. I do not know how valuable our data is, considering our sample size was just two people. We just wanted to see whether it was possible to arrange such an intervention in humans using the means we had at our disposal, and whether it would do any good. Now we know it actually did some good, in terms of the number of naïve T-cells, levels of oxidized LDL. The drop in Ox-LDL levels was probably due not simply to dilution but to some deeper processes, because in one participant, these levels declined, while in the other they went up from an originally low level. So, in both participants, LDL levels normalized and stayed normal for at least two weeks. Liver markers improved by a lot, and the myelocyte/lymphocyte ratio improved. There were some controversial results, such as one participant having insulin levels decline four-fold but not the other one.

The authors of this open access papers discuss the prominent role of cell signaling in the better known classes of intervention that have been shown to slow aging in worms, flies, and mice. The body is a network in which cells in one tissue influence the behavior of cells in other tissues via the signal molecules and vesicles that they secrete into the circulatory system. This leads to a focus on mimicking these signals, such as in the production of calorie restriction mimetics and exercise mimetics. As an approach to extending healthy life span, this seems likely to be bounded in effectiveness by the present natural variability of life span in response to environment and circumstance. Many of us consider this to be a case of aiming too low, a poor strategy in comparison to the goal of periodic repair of the underlying damage that causes aging.

The benefits of discovering therapeutics that target aging are many, including (1) decreasing the financial burden on our strained healthcare system, (2) increasing the amount of time older adults live free of chronic diseases (often denoted as healthspan), and (3) potentially increasing maximum human lifespan. Organismal lifespan was first presented as a genetically modifiable trait by groundbreaking publications describing the effects of the FOXO transcription factor DAF-16 on longevity in Caenorhabditis elegans. Although modifying genes or substantially changing environments is not plausible in humans, it is feasible to find anti-aging therapeutics that mimic environmental cues or genetic signaling environments.

Deciphering how cells relay information to one another remains one of the foundational discoveries in biology. This concept, that cells can relay critical information to other cells in response to an initial signaling cue, allows for genes expressed in one cell or tissue to affect the physiology of other cells and tissues. This ability of genes to affect processes outside of the cells they are expressed in is often referred to as cell non-autonomous action or signaling.

More recently, high-profile publications from multiple labs have shown that many signaling pathways reported to improve longevity (e.g. mitochondrial stress, insulin-like signaling, heat shock, and the hypoxic response) act through cell non-autonomous signaling mechanisms. These pathways originate in sensory cells, often neurons, that signal to peripheral tissues and promote survival during the presence of stress. Importantly, this activation of stress response pathways, either through genetic modification or exposure to environmental stress, is often sufficient to improve health and longevity. Additionally, genetic modification of these pathways can often target the aging process while sparing growth/development/reproduction effects that are often consequences of environmental stress. Understanding how cell non-autonomous signaling influences longevity is a relatively recent concept in aging research and presents a novel opportunity to discover pharmacological interventions that modulate signaling to increase healthspan and longevity.

With the establishment of cell non-autonomous regulation of aging in multiple pathways and organisms, there is immense therapeutic potential for this area going forward. Most therapeutics logically target the tissues where physiological change is important, while understanding signaling networks provides a unique opportunity to use the natural signaling network to 'trick' key tissues into improving long-term health. This will not necessarily be easy, as targeting neural circuits using broad drugs (e.g. SSRIs) often have pleiotropic effects, but the better we understand the signaling networks the more specifically we could, in theory, mimic the signals. Using a signaling approach to anti-aging therapeutics would allow for induction of hormetic effects without the need for an acute stress, and has great potential to mimic well-established longevity interventions such as dietary restriction.

Link: https://doi.org/10.7554/eLife.62659

Researchers here provide evidence for loss of ribbon synapases in the inner ear to be an early stage of the neurodegeneration that leads to age-related deafness. Other evidence also points to loss of neural connections between ear and brain as the most important contributing cause in age-related deafness, more so than any loss of sensory hair cells in the inner ear that might take place. This points towards approaches to therapy that are primarily based on regeneration of neural connections, rather than provision of replacement cells. While there is some overlap between specific implementations of these strategies, they are quite different end goals.

Age-related hearing loss (ARHL), or presbycusis, is a progressive and pathological process that results from age-related degeneration of the cochlea and central auditory system. It affects almost half of individuals over the age of 75 years. It is characterized by significant elevations in the hearing threshold with reductions in speech discrimination and difficulty in localization of sound sources, particularly in noisy environments. Previous studies have shown that the loss of outer hair cells (OHCs), damage to the stereocilia, and degenerated alterations of the auditory nerves are possible mechanisms underlying ARHL. However, recent studies have reported that these degenerative morphological changes in the cochlea occur after the onset of the hearing disorder. For example, specific noise exposure can cause hearing loss coupled with intact cochlear hair cells, stereocilia, and spiral ganglion neurons (SGNs), which suggests that other cochlear components may be responsible for hearing loss.

Both the ototoxic drugs such as gentamicin, and noise exposure have been proposed to cause a loss of ribbon synapses, which account for hearing impairment. Ribbon synapses of the inner hair cells (IHCs) are formed on the cochlea with a powerful function specialized for encoding acoustic signals with high temporal precision over long periods. It has been reported that aging cochlea could form unexpected folded endings in the postsynaptic nerve terminals, suggesting that aging could affect the morphologies or function of ribbon synapses. However, it remains unclear whether the quantity and function of the ribbon synapse are initially disrupted and thus contribute to the consequent hearing loss during aging.

In this study, we aimed to verify whether cochlear ribbon synapses are vulnerable to aging insult in C57BL/6J mice, a widespread model for ARHL. We explored the correlation between the number and function of ribbon synapses and the reduction of hearing function in the early stage of aging. We found that the loss of cochlear ribbon synapses is an initial pathological event in the early stage of aging, which causes hearing loss and may consequently induce loss or damage to other cochlear components, such as IHCs, and SGNs.

Link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7724364/

The general consensus on mortality due to COVID-19 is that it falls most heavily on people who are more impacted by aging: poor immune function when it comes to defense against pathogens; high levels of chronic inflammation that create a greater susceptibility to the way in which SARS-CoV-2 kills people; existing chronic disease; and a mortality rate that is already high even setting aside the pandemic. When younger people die due to the virus, in much smaller numbers, it is where they share these characteristics of inflammation, deficient immune systems, and chronic disease. This level of morbidity is unusual in younger individuals, but very prevalent in the old.

In today's open access commentary we see that COVID-19 mortality in older people is becoming comparable to that of the major age-related conditions, such as cancer. Those killed by COVID-19 are largely people with greater degrees of frailty and a shorter remaining life expectancy. We might see mortality fall significantly in the next few years, after the present pandemic mortality subsides due to the combination of vaccination and immunity to this virus. An appreciable fraction of those individuals who would have survived to die of non-communicable age-related conditions in 2021 or 2022 are dying now.

As to the numbers themselves, COVID-19 appears to continue to be on track to be at the worse end of the expected 3 to 6 times multiple of a bad influenza year: 300,000 deaths in the US versus 60,000 for the 2017-2018 influenza season. While there are numerous lessons to be taken from the past year regarding the behavior of highly regulated organizations and services, none of which are likely to be heeded, the most important lesson for the long term is that (a) old people are vulnerable to infection precisely because they have a failing immune system, and (b) there are many clear and obvious research projects that offer the potential to rejuvenate the aged immune system. Regrowing the thymus, restoring hematopoietic stem cell function, clearing out worn and damaged immune cells, and so forth. A great deal more funding and attention should be given to these lines of research.

COVID-19 as the Leading Cause of Death in the United States

A helpful approach to put the effects of the pandemic in context is to compare COVID-19-related mortality rates with the leading causes of death that, under ordinary circumstances, would pose the greatest threat to different age groups. The conditions listed in the table include the three leading causes of death in each of the 10 age groups from infancy to old age. Using data from the Centers for Disease Control and Prevention, the table shows mortality rates for these conditions during the period of March through October 2018 (the most recent year for which detailed cause-of-death data are available) with COVID-19 mortality rates during March through October 2020.

The table shows that by October 2020 COVID-19 had become the third leading cause of death for persons aged 45 through 84 years and the second leading cause of death for those aged 85 years or older. Adults 45 years or older were more likely to die from COVID-19 during those months than from chronic lower respiratory disease, transport accidents (eg, motor vehicle fatalities), drug overdoses, suicide, or homicide. In contrast, for individuals younger than age 45 years, other causes of death, such as drug overdoses, suicide, transport accidents, cancer, and homicide exceeded those from COVID-19.

Between November 1, 2020, and December 13, 2020, the 7-day moving average for daily COVID-19 deaths tripled, from 826 to 2430 deaths per day, and if this trend is unabated will soon surpass the daily rate observed at the height of the spring surge (2856 deaths per day on April 21, 2020). As occurred in the spring, COVID-19 has become the leading cause of death in the United States (daily mortality rates for heart disease and cancer, which for decades have been the two leading causes of death, are approximately 1700 and 1600 deaths per day, respectively). With COVID-19 mortality rates now exceeding these thresholds, this infectious disease has become deadlier than heart disease and cancer, and its lethality may increase further as transmission increases with holiday travel and gatherings and with the intensified indoor exposure that winter brings.

Researchers here use the mitochondrially targeted peptide SS-31 to demonstrate a role for increased proton leak and consequent mitochondrial dysfunction in the progression of cardiomyopathy towards heart failure. Mitochondria are the power plants of the cell, producing chemical energy store molecules to power cellular processes. With age, mitochondria become less functional throughout the body. This is particularly problematic in energy-hungry tissues such as heart muscle. Numerous lines of research and development attempt to fix one or another of the many proximate causes of that loss of mitochondrial function, with varying degrees of success. Here, it is noted that SS-31 can restore a third of the lost diastolic function in old mice by reducing proton leak and improving mitochondrial performance.

While more attention has been placed on mitochondrial electron leak and consequent free radical generation, proton leak is a highly significant aspect of mitochondrial energetics, as it accounts for more than 20% of oxygen consumption in the liver and 35-50% of that in muscle in the resting state. There are two types of proton leak in the mitochondria: (1) constitutive, basal proton leak, and (2) inducible, regulated proton leak, including that mediated by uncoupling proteins (UCPs). In skeletal muscle, a majority of basal proton conductance has been attributed to adenine nucleotide translocase (ANT). Although aging-related increased mitochondrial proton leak was detected in the mouse heart, kidneys, and liver by indirect measurement of oxygen consumption in isolated mitochondria, direct evidence of functional impact remains to be further investigated. Moreover, the exact site and underlying mechanisms responsible for aging-related mitochondrial proton leak are unclear.

SS-31 (elamipretide) binds to cardiolipin-containing membranes and improves cristae curvature. Prevention of cytochrome c peroxidase activity and release has been proposed as its major basis of activity. SS-31 is highly effective in increasing resistance to a broad range of diseases, including heart ischemia reperfusion injury, heart failure, neurodegenerative disease, and metabolic syndrome. In aged mice, SS-31 ameliorates kidney glomerulopathy and brain oxidative stress and has shown beneficial effects on skeletal muscle performance. We have recently shown that administration of SS-31 to 24-month-old mice for 8 weeks reverses the age-related decline in diastolic function, restoring this parameter 35% toward that of young (5-month-old) mice. However, how SS-31 benefits and protects aged cardiac cells remains unclear.

In this report, we investigated the effect and underlying mechanism of action of SS-31 on aged cardiomyocytes, especially on the mitochondrial proton leak. Using the naturally aged rodent model we provided direct evidence of increased proton leak as the primary energetic change in aged mitochondria. We further show that the inner membrane protein ANT1 mediates the augmented proton entry in the old mitochondria. Most significantly, we demonstrate that SS-31 acutely prevents the excessive mitochondrial proton entry and rejuvenates mitochondrial function through direct association with ANT1 and stabilization of the ATP synthasome.

Link: https://doi.org/10.7554/eLife.60827

Exercise beneficially influences fat tissue metabolism, and researchers here find that the protein DICER is necessary for these benefits to take place. Expression of DICER declines with age, but is increased by structured exercise programs - though to a very variable degree. This variability suggests that a great deal more exploration is needed in order to understand this portion of the diverse set of mechanisms by which exercise improves health. DICER is just one part of a network of signals and regulators, and much is yet to be cataloged of their interactions.

Adipose tissue is not just a simple reservoir of energy for periods of food scarcity. It contributes significantly to regulation of the metabolism, releasing various molecules into the bloodstream, including microRNAs that modulate the expression of key genes in different parts of the organism, including the liver, pancreas, and muscles. Research has shown that both aging and obesity can impair the production of these regulatory microRNAs by adipose tissue and favor the development of diseases such as diabetes and dyslipidemia.

Results showed the occurrence of communication between muscle and adipose tissue during aerobic exercise via signaling molecules secreted into the bloodstream. This exchange of information makes energy consumption by adipose cells more efficient, enabling the metabolism to adapt to exercise and enhancing the performance of the muscles. Mice were subjected to a 60-minute treadmill running protocol for eight weeks. As they became fitter, treadmill speed and inclination were increased. At the end, in addition to the improvement in performance, the scientists found a significant elevation in adipocyte levels of DICER expression, which was accompanied by a reduction in body weight and visceral fat.

When they repeated the experiment with mice that were genetically modified not to express DICER in adipose cells, the researchers found that the beneficial effects of aerobic exercise were far smaller. "The animals didn't lose weight or visceral fat, and their overall fitness didn't improve. We also observed that adipose cells used the energy substrate differently in these GM mice than in wild mice, leaving less glucose available for muscles." In humans, six weeks of high-intensity interval training (HIIT) were sufficient to yield a fivefold increase in the amount of DICER in adipose tissue on average. The effect was observed in both younger volunteers, aged about 36, and older subjects, aged about 63. The response varied considerably between individuals, however, with DICER increasing as much as 25 times in some, and very little in others.

"We identified a molecule called miR-203-3p, whose expression increases with both training and caloric restriction. We showed that this microRNA is responsible for promoting metabolic adjustment in adipocytes. When muscles use up all their glycogen during prolonged exercise, molecular signals are sent to adipose tissue and miR-203-3p fine-tunes the adipocyte metabolism. We found this metabolic flexibility to be essential to good health as well as performance enhancement. In genetically modified mice that don't express DICER in adipocytes, this conversation between adipose tissue and muscles doesn't happen. It's a model that mimics aging and obesity. So when DICER declines, metabolic health is poor and degenerative processes accelerate."

Link: https://www.eurekalert.org/pub_releases/2020-12/fda-sdh120720.php

The key to a universal cancer therapy is to find a vulnerability that is (a) common to all cancers, something fundamental to cancer as a class, (b) nowhere near as prevalent in normal cells, and (c) can be cost-effectively exploited as a basis for treatment. Lengthening of telomeres is a good example, and an area in which at least a few groups are working at an early stage. Cancer cells must employ telomerase or alternative lengthening of telomeres mechanisms to evade the Hayflick limit on replication, triggered by short telomeres, as telomere length is reduced with each cell division. Other examples include other mechanisms related to cell replication, unsurprisingly given that unfettered replication is a defining characteristic of cancer. Today's research materials discuss an interesting example of this type of approach.

Researchers here note that production of proteins from mitochondrial DNA is critical to cell replication. Yet their experiments in interfering in that process demonstrate that mitochondrial gene expression is not so critical that it can't be turned off for a while in normal tissues, given a normal rate of cell division. Cancerous cells, on the other hand, with their rampant pace of replication, run into issues if their ability to produce proteins from mitochondrial DNA is impaired. Reducing the ability of cancerous cells to replicate is a promising way to improve the effectiveness of any treatment based on killing cancerous cells, and particularly if it can be applied to any cancer by virtue of the universality of the underlying mechanism.

Novel principle for cancer treatment shows promising effect

Mitochondria are the power plants of our cells. They are essential for converting the energy in the food we eat into the common energy currency that is required for a variety of cellular functions. Cancer cells are critically dependent on mitochondria, not only for providing energy but also for producing a variety of building blocks needed to make more cells as the cancer cells divide. The continuous cell division means that a cancer cell must constantly make new mitochondria in order to grow.

Previous attempts to target mitochondria for cancer treatment have focused on acutely inhibiting mitochondrial function. However, this strategy has often resulted in severe side effects due to the crucial role of mitochondria for normal tissue function. As an alternative, researchers developed a novel strategy that does not directly interfere with the function of existing mitochondria. Instead, they designed highly selective inhibitors that target the mitochondria's own genetic material, mtDNA, which has a critical role in the formation of new mitochondria.

When investigating the mechanism of action of these novel inhibitors, the researchers observed that the inhibitors put cancer cells into a state of severe energy and nutrient depletion. This leads to loss of necessary cellular building blocks, reduced tumour cell growth and ultimately cell death. "Previous findings from our research group have shown that rapidly dividing cells, such as cancer cells, are crucially dependent on mtDNA to form new functional mitochondria. Consequently, treatment with our inhibitors specifically affects proliferation of tumour cells, whereas healthy cells in tissues such as skeletal muscle, liver, or heart remain unaffected for a surprisingly long time."

Small-molecule inhibitors of human mitochondrial DNA transcription

Altered expression of mitochondrial DNA (mtDNA) occurs in ageing and a range of human pathologies (for example, inborn errors of metabolism, neurodegeneration, and cancer). Here we describe first-in-class specific inhibitors of mitochondrial transcription (IMTs) that target the human mitochondrial RNA polymerase (POLRMT), which is essential for biogenesis of the oxidative phosphorylation (OXPHOS) system. The IMTs efficiently impair mtDNA transcription and cause a dose-dependent inhibition of mtDNA expression and OXPHOS in cell lines.

The growth of cancer cells and the persistence of therapy-resistant cancer stem cells has previously been reported to depend on OXPHOS, and we therefore investigated whether IMTs have anti-tumour effects. Four weeks of oral treatment with an IMT is well-tolerated in mice and does not cause OXPHOS dysfunction or toxicity in normal tissues, despite inducing a strong anti-tumour response in xenografts of human cancer cells. In summary, IMTs provide a potent and specific chemical biology tool to study the role of mtDNA expression in physiology and disease.

Here I'll point out a very high level review of the present senolytics biotech companies. These companies are all quite young, focused on various means of selectively destroying the senescent cells that accumulate with age. Animal data from mice shows that these cells are an important contributing cause of aging and age-related disease, as clearing them reverses the progression many aspects of aging and age-related diseases, while also extending life span. Senescent cells exhibit the senescence-associated secretory phenotype (SASP), producing a mix of molecules that provoke chronic inflammation and tissue dysfunction. The biochemistry of senescence is, so far as the research community has determined to date, very similar in all its important aspects in mice and humans. It is thus hoped that senolytic therapies will be the first rejuvenation treatments worthy of title.

Unity Biotechnology is way ahead of the pack: No other company is in the clinic (though Mayo Clinic has a Dasatinib + Quercetin Phase 2 trial). Unity has already completed a Phase 2 (UBX0101, failed) and they are currently conducting a new Phase 1 (UBX1325). But first is not always best - Unity's approach is somewhat crude compared to the targeted approaches of newer senolytics companies. But perhaps it will be enough. More senolytic trials are coming: Unity won't be alone in the clinical stage for long. I believe that FoxBio, Senolytic Therapeutics, Numeric Biotech, and Rubedo Life Science will be in the clinic within 12 - 24 months.

1st Gen vs 2nd Gen: Dasatinib, Navitoclax, UBX0101 were 1st generation senolytics developed by hypothesis: That existing drugs that targeted anti-apoptotic pathways might also clear senescent cells. Unfortunately, many of these 1st gen drugs have off-target effects that kill non-senescent cells, too. Now it appears the majority of the industry is focusing on 2nd generation therapies through high-throughput screens to improve selectivity. Novel targeted modalities (peptides, monoclonal antibodies, gene therapy, immunotherapy, RNA) and delivery (nanoparticles and conjugate prodrugs) are being developed as well.

Unity Biotechnology is the only senolytics company to go public so far. However, Juvenescence is planning to go public within ~6 months, at which point you will be able to own a slice of FoxBio. The current market is amenable to IPOs so I wouldn't be surprised if another senolytics company went public just before their Phase 1 trials - perhaps in the next two to three years, should markets hold up.

The majority of companies are focussing on killing senescent cells with senolytics. However, four companies have senomorphic pipelines (Senolytic Therapeutics, Senisca, Atropos Therapeutics, Dorian Therapeutics). I'm excited to see which approach will prove most effective, though I am less sanguine on the clinical prospects of approaches that merely slow senescence.

Would a second Unity Biotechnology failure have an impact on the future of senolytics? Yes and no. Unity is just one of many companies developing senolytics and their current clinical trials are only testing the earliest senolytic strategy (1st gen). There are many more senolytics companies aiming for clinical trials in the next two years and some will be testing 2nd generation targeted therapies. If UBX1325 were to fail in Phase 2 the immediate effect would be a decrease in unsophisticated capital in the senolytics space - from those who don't understand the other promising targets and modalities in development. This might be a notable amount of money in the short term but long term I am optimistic about senolytics. All it takes is one success for the floodgates to open.

Link: https://longevitymarketcap.substack.com/p/018-a-tour-of-all-senolytics-companies

People who maintain cardiovascular fitness as they age exhibit an onset of degeneration and age-related disease that takes place more slowly than that of their peers. This includes a much lower risk of dementia, as illustrated by the study data noted here, indicating the strong influence of the cardiovascular system on brain function. Firstly, the brain is an energy-hungry organ, and worse circulation leads to worse function quite directly. Separately, cardiovascular fitness tends to correlate with a lesser degree of hypertension with age. The raised blood pressure of hypertension causes damage to brain tissue and vessels in the brain, and a consistently lower level that damage makes a noteworthy difference over time. Distinctly again, the exercise needed to maintain physical fitness produces greater cell maintenance activities, leading to a slower accumulation of many forms of cell and tissue damage that contribute to to onset of dementia.

Very few studies have explored the patterns of cardiovascular health (CVH) metrics in midlife and late life in relation to risk of dementia. We examined the associations of composite CVH metrics from midlife to late life with risk of incident dementia. This cohort study included 1,449 participants from the Finnish Cardiovascular Risk Factors, Aging, and Dementia (CAIDE) study, who were followed from midlife (baseline from 1972 to 1987; mean age 50.4 years; 62.1% female) to late life (1998), and then 744 dementia-free survivors were followed further into late life (2005 to 2008). We defined and scored global CVH metrics based on 6 of the 7 components (i.e., smoking, physical activity, and body mass index [BMI] as behavioral CVH metrics; fasting plasma glucose, total cholesterol, and blood pressure as biological CVH metrics) following the modified American Heart Association (AHA)'s recommendations. Then, the composite global, behavioral, and biological CVH metrics were categorized into poor, intermediate, and ideal levels. Dementia was diagnosed following the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) criteria.

During the follow-up examinations, dementia was diagnosed in 61 persons in 1998 and additional 47 persons in 2005 to 2008. The fully adjusted hazard ratio (HR) of dementia was 0.71 and 0.52 for midlife intermediate and ideal levels (versus poor level) of global CVH metrics, respectively; the corresponding figures for late-life global CVH metrics were 0.60 and 0.91 . Compared with poor global CVH metrics in both midlife and late life, the fully adjusted HR of dementia was 0.25 for people with intermediate global CVH metrics in both midlife and late life and 0.14 for those with midlife ideal and late-life intermediate global CVH metrics. Having an intermediate or ideal level of behavioral CVH in both midlife and late life (versus poor level in both midlife and late life) was significantly associated with a lower dementia risk, whereas people with midlife intermediate and late-life ideal biological CVH metrics had a significantly increased risk of dementia.

In this study, we observed that having the ideal CVH metrics, and ideal behavioral CVH metrics in particular, from midlife onwards is associated with a reduced risk of dementia as compared with people having poor CVH metrics. Maintaining life-long health behaviors may be crucial to reduce late-life risk of dementia.

Link: https://doi.org/10.1371/journal.pmed.1003474

Senolytic drugs are those capable of selectively destroying senescent cells. A range of such therapies are at various stages of development, including those that have reached initial human clinical trials. Senescent cell accumulation is an important cause of degenerative aging, and the removal of such cells via senolytic treatments has been shown to produce rejuvenation and extension of life in animal models of age-related disease. Senescent cells, while never very large in numbers relative to other cells in the body, secrete a potent mix of molecules that spurs chronic inflammation and degrades tissue structure and function. The more senescent cells, the worse the outcome.

At present assessment of senolytics in human medicine is still at a comparatively early, albeit promising, stage. Data will emerge at the usual glacial pace characteristic of the highly regulated medical industry. It may be possible to extract some data on the performance of first generation senolytic drugs in advance of clinical trials, however. Many of these drugs have been widely used for years in patient populations, as treatments for various age-related conditions, and all of that data still exists, there to be analyzed.

The primary challenge here is that most such first generation senolytic drugs are chemotherapeutics. Firstly the patients in question were not in good shape at all, exhibiting significant mortality and loss of function due to cancer and its complications, making it hard to pick out benefits to health. Secondly chemotherapeutic doses are higher and more sustained than senolytic doses, causing significant additional cell death and dysfunction. Is it possible to work around these issues by picking a comparatively isolated part of the body, such as the retina, as is the case in today's open access paper? Maybe, but I think that there remain sizable issues that would need to be addressed before one could take any such data at face value. Particularly given the very small sample size used here as a proof of concept for the ability to gather and analyze a broader range of data. For now, this is an interesting idea, perhaps worthy of further exploration.

Evaluating the neuroprotective impact of senolytic drugs on human vision

Based on neuropathological similarities of glaucoma with other age-related neurodegenerative diseases such as Alzheimer's and the involvement of the ubiquitin-proteasome and chaperone systems, researchers have hypothesized a cellular senescence contribution to glaucoma pathogenesis. Preclinical evidence has supported the cellular senescence hypothesis as a contributor to glaucoma pathogenesis. Senescent cells secrete a plethora of molecules known as senescence associated secretory proteins (SASP), which affect surrounding cells by inducing either apoptosis or senescence, thus propagating the phenotype. There are several senolytic drugs that are able to specifically target senescent cells to overcome the apoptosis block to remove them, presenting an attractive hypothesis for potential treatment of glaucoma.

Indeed, our recent study has shown that targeting senescent retinal ganglion cells (RGCs) in a mouse model of glaucoma using the senolytic drug dasatinib protected the remaining RGCs and visual function from glaucomatous injury. These data are also supported by evidence from human studies, as a bioinformatics analysis of genes associated with primary open angle glaucoma suggested senescence as a key factor in pathogenesis.

Little is known about the neuroprotective effects or safety of senolytic drugs on vision in human patients, however. Clinical management of glaucoma involves acquisition of extensive longitudinal data including visual acuity, intraocular pressure (IOP), visual field sensitivity, and retinal nerve fiber thickness. Compared to other neurodegenerative diseases that often lack objective standardized metrics of clinical progression, some of these ophthalmic data are readily available and amenable to investigations of novel therapeutics, including senolytic drugs. To this end, we performed a retrospective analysis of existing clinical data to evaluate the effect of senolytics on vision and glaucoma progression. For the current study, we queried the electronic health record (EHR) system of a large academic medical center to identify glaucoma and glaucoma suspect patients exposed to at least one senolytic drug and conducted several analyses of visual data.

Senolytic exposure was not associated with decreased visual acuity, elevated intraocular pressure, or documentation of senolytic-related adverse ocular effects by treating ophthalmologists. Additionally, patients exposed to senolytics (n = 9) did not exhibit faster progression of glaucomatous visual field damage compared to matched glaucoma patients (n = 26) without senolytic exposure. These results suggest that senolytic drugs do not carry significant ocular toxicity and provide further support for additional evaluation of the potential neuroprotective effects of senolytics on glaucoma and other neurodegenerative diseases.

Resveratrol and derived molecules were for a time excessively hyped as a means to trigger some of the beneficial metabolic response produced by calorie restriction, by acting on sirtuins, and thus have a positive impact on aging. The company Sirtris was founded to develop this area of research into a therapeutic, its backers did a great deal to promote the aforementioned excessive hype, the company sold to Big Pharma for a sizable sum, and then the program was later dropped because the effect sizes were small and unreliable. The years following this sort of hype cycle tend to see a great deal of independent investigation of mechanisms, just in case there is gold in those hills. That is followed by review papers such as the one noted here, when it turns out in the end that there wasn't much of practical application to be found in this line of research.

Caloric restriction (CR) has been shown repeatedly to prolong the lifespan in laboratory animals, with its benefits dependent on molecular targets forming part of the nutrient signaling network, including the NAD-dependent deacetylase silent mating type information regulation 2 homologue 1 (SIRT1). It has been hypothesized that the stilbene resveratrol (RSV) may counteract age- and obesity-related diseases similarly to CR. In yeast and worms, RSV-promoted longevity also depended on SIRT1.

While it remains unclear whether RSV can prolong lifespans in mammals, some studies in rodents supplemented with RSV have reported lowered body weight (BW) and fat mass, improved insulin sensitivity, lowered cholesterol levels, increased fitness, and mitochondrial biogenesis. Molecular mechanisms possibly leading to such changes include altered gene transcription and activation of SIRT1, AMP-activated kinase (AMPK), and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PPARGC1A). However, some mouse models did not benefit from RSV treatment to the same extent as others.

We conducted a literature search for trials directly comparing RSV application to CR feeding in mice. In most studies retrieved by this systematic search, mice supplemented with RSV did not show significant reductions of BW, glucose, or insulin. Moreover, in some of these studies, RSV and CR treatments affected molecular targets differently and/or findings on RSV and CR impacts varied between trials. Although there may be a moderate effect of RSV supplementation on parameters such as insulin sensitivity toward a more CR-like profile in mice, data are inconsistent. Likewise, RSV supplementation trials in humans report controversial findings. While we consider that RSV may, under certain circumstances, moderately mimic some aspects of CR, current evidence does not fully support its use to prevent or treat age- or obesity-related diseases.

Link: https://doi.org/10.1093/advances/nmaa148

Here is a reminder that the increased blood pressure of hypertension, or even more modestly raised blood pressure, is an important downstream mechanism in aging. Higher blood pressure over time results in greater tissue damage to the brain, kidneys, and other organs, greater vulnerability to atherosclerosis, and many more issues. Raised blood pressure is one of the more important ways in which the underlying molecular damage of aging is converted into structural and physical damage that leads to death.

High blood pressure appears to accelerate a decline in cognitive performance in middle-aged and older adults. Nearly half of American adults have high blood pressure or hypertension. Having high blood pressure is a risk factor for cognitive decline, which includes such things as memory, verbal fluency, attention and concentration. Blood pressure of 120 mmHg - 129 mmHg systolic (the top number in a reading) or higher is considered elevated. Systolic pressure above 130 mmHg, or diastolic pressure (the bottom number) of 80 mmHg or higher is considered hypertension.

Researchers analyzed findings from an existing study that included blood pressure and cognitive health information for more than 7,000 adults in Brazil, whose average age was about 59 years old at the study's start. The study participants were followed for an average of nearly 4 years; testing included analysis of memory, verbal fluency, and executive function, which includes attention, concentration, and other factors associated with thinking and reasoning.

Systolic blood pressure between 121 and 139 mmHg or diastolic blood pressure between 81 and 89 mmHg with no antihypertensive medication use was associated with accelerated cognitive performance decline among middle-aged and older individuals. The speed of decline in cognition happened regardless of hypertension duration, meaning high blood pressure for any length of time, even a short duration, might impact a person's speed of cognitive decline. Adults with uncontrolled hypertension tended to experience notably faster declines in memory and global cognitive function than adults who had controlled hypertension.

"In addition to other proven benefits of blood pressure control, our results highlight the importance of diagnosing and controlling hypertension in patients of any age to prevent or slow down cognitive decline. Our results also reinforce the need to maintain lower blood pressure levels throughout life, since even prehypertension levels were associated with cognitive decline."

Link: https://newsroom.heart.org/news/high-blood-pressure-at-any-age-no-matter-how-long-you-have-it-may-speed-cognitive-decline

Decellularization followed by recellularization is a well explored approach to tissue engineering. Researchers take a donor organ or tissue section, decellularize it to leave the intricate extracellular matrix and all of its chemical cues, and then recellularize with with the desired mix of cells. When those cells are derived from a patient, it is possible to generate tissue that can be transplanted into that patient with minimal risk of rejection. There are also groups working on enabling cross-species transplantation from pigs to humans via this strategy of replacing all of the cells in an organ with patient-matched cells.

Further, recellularization can bypass the major challenge of vascular network creation in tissue engineering. Natural tissues contain extensive capillary networks, hundreds of tiny blood vessels passing through every square millimeter of tissue cross-section. Without capillaries, tissue cannot be more than a millimeter or two in thickness, as cells will not be able to receive nutrients. Capillary networks have so far proven challenging to produce at the fine scale needed via bioprinting of entirely artificial tissue structures, though some inroads have been made in recent years. A decellularized extracellular matrix contains those capillaries already.

This is not to say that recellularization of a decelluralized tissue is straightforward. Just like the production of organoids, small functional organ tissue sections grown from cells, a recipe must be established, the right cell populations derived and introduced into the right places, in the right order, provided with the right supporting cues and nutrients, and so forth. This is different for each different type of organ tissue, and there are a great many organs worthy of interest.

Today's example is the production of a recellularized organ important to the immune system, the thymus. The thymus atrophies with age, but active thymic tissue is required for thymocytes created in the bone marrow to mature into T cells of the adaptive immune system. As the supply of new T cells diminishes with age, the adaptive immune system becomes ever more dysfunctional and damaged. The thymus is unfortunately deep within chest, and a straightforward transplantation is a more extensive surgery than would be desirable in later life. The researchers behind Lygenesis have demonstrated in animal models that thymic organoid tissue placed into much more accessible lymph nodes can function correctly, however. Since thymocytes already migrate to the thymus, moving (or even distributing) the thymus to other locations in the body is a possibility. It remains to be seen as to how the tissue engineering approaches to the challenge of thymic atrophy - and consequent immune dysfunction - will evolve in the years ahead, but producing functional thymic tissue is a necessary starting point.

Scientists build whole functioning thymus from human cells

Researchers have rebuilt a human thymus, an essential organ in the immune system, using human stem cells and a bioengineered scaffold. To rebuild this organ, the researchers collected thymi from patients and in the laboratory, grew thymic epithelial cells and thymic interstitial cells from the donated tissue into many colonies of billions of cells. The next step for the researchers was to obtain a structural scaffold of thymi, which they could repopulate with the thymic cells they had cultured. For this, researchers developed a new approach to remove all the cells from rat thymi, so only the structural scaffolds remained. They had to use a new microvascular surgical approach for this, as conventional methods are not effective for the thymus.

The researchers then injected the organ scaffolds with up to six million human thymic epithelial cells as well as interstitial cells from the colonies they had grown in the lab. The cells grew onto the scaffolds and after only five days, the organs had developed to a similar stage as those seen in nine-week old foetuses. Finally, the team implanted these thymi into mice. They found that in over 75% of cases, the thymi were able to support the development of human lymphocytes. The researchers are continuing their work rebuilding thymi to refine and scale up the process.

Reconstitution of a functional human thymus by postnatal stromal progenitor cells and natural whole-organ scaffolds

The thymus is a primary lymphoid organ, essential for T cell maturation and selection. There has been long-standing interest in processes underpinning thymus generation and the potential to manipulate it clinically, because alterations of thymus development or function can result in severe immunodeficiency and autoimmunity. Here, we identify epithelial-mesenchymal hybrid cells, capable of long-term expansion in vitro, and able to reconstitute an anatomic phenocopy of the native thymus, when combined with thymic interstitial cells and a natural decellularised extracellular matrix (ECM) obtained by whole thymus perfusion. This anatomical human thymus reconstruction is functional, as judged by its capacity to support mature T cell development in vivo after transplantation into humanised immunodeficient mice.

This open access paper provides an overview of Cisd2, one of many genes for which upregulation extends life and improves health in mice. This is potentially mediated by its effects on the cellular maintenance processes of autophagy and on mitochondrial function. It reduces the loss of mitochondrial function that occurs in aging, perhaps through improved removal of damaged mitochondria via mitophagy, but perhaps through other mechanisms. The researchers show that Cisd2 expression is upregulated as a result of exercise, making it plausibly a part of the regulatory system by which the response to exercise can improve health and slow the progression of aging.

Cisd2 (CDGSH Iron Sulfur Domain 2) is an oxidative stress-sensitive gene, the expression of which is able to prolong the lifespan in mice. Cisd2 loss-of-function mice exhibit premature aging phenotypes and have a shortened lifespan. Conversely, Cisd2 transgenic mice not only are longer lived (both males and females), they also have a healthier physical condition, such as better fur function, increased muscle strength and improved cardiac function. The Cisd2 protein has been localized to mitochondria, mitochondria-associated membrane (MAM) and the endoplasmic reticulum (ER), and is involved in calcium homeostasis. We have demonstrated using aged mice that maintenance of the expression level of Cisd2 sustains metabolic activity, ameliorates aging-associated mitochondrial dysregulation, reduces DNA damages and improves the calcium imbalance within skeletal muscles, liver, and heart. Taken together, Cisd2 is a lifespan regulator and its expression level seems to be a critical factor in relation to prolong healthspan.

Cisd2 and exercise have both been reported to contribute to an extended lifespan and to improve healthspan. A recent report has shown that the protein levels of Cisd1 and Cisd2 in skeletal muscle and white adipose tissue are increased approximately 1.5-fold and 1.2-fold after 4 weeks of voluntary excise in mice. The authors also observed that there were significant increases in the levels of multiple mitochondrial proteins, which agrees with our previous discovery of increased mitochondrial number in the muscle of Cisd2 transgenic mice compared to their wild type cohorts. To examine the transcription of Cisd2 in real-time, here we have generated a Cisd2 reporter transgenic mouse that carries luciferase as the reporter. The Cisd2-Luciferase reporter mice were trained on a treadmill for 56 days. It was found that a drastic enhancement in Cisd2 transcription was able to be observed. The most intense signal was observed at the abdomen, with the thymus showing the next largest increase in signal. A moderately increase in signal was also observed in forelimbs and hindlimbs.

Link: https://doi.org/10.3390/ijms21239059

The later, "wet" stages of macular degeneration involve the inappropriate formation of leaky blood vessels under the retina, destroying its integrity and function. This is in large part driven by chronic inflammation and the altered cell behavior that it causes. Researchers here focus on one specific class of regulators of inflammation and its role in the progression of macular degeneration.

Inflammasomes are multiprotein complexes that lead to the proteolytic activation of proinflammatory IL-1β and IL-18 through the catalytic activity of caspase-1. Canonical inflammasome activation is initiated by cytosolic pattern recognition receptors (PRRs) when exposed to specific triggers, either microbe-derived pathogen-associated molecular patterns (PAMPs) or host-derived danger-associated molecular patterns (DAMPs). These PRRs include the family of NOD-like receptors, to which NLRP3 belongs.

Recent studies implicated canonical inflammasome activation in age-related macular degeneration (AMD) pathogenesis. However, these studies have focused on the NLRP3 inflammasome and did not consider a potential contribution of other PRRs for inflammasome activation in AMD. The reason for this very narrow focus on NLRP3 as a PRR that initiates inflammasome activation in AMD is that various stimuli that are well-established risk factors for AMD, including increased oxidative stress or lipid accumulations, are known activators of the NLRP3 inflammasome. This has led to the assumption that AMD risk factors promote NLRP3 inflammasome activation, which further exacerbates AMD pathologies through activation of proinflammatory cytokines, such as IL-1β that is known to stimulate inflammatory angiogenesis.

Key open questions are (1) whether NLRP3 inflammasome activation mainly in retinal pigment epithelium (RPE) or rather in non-RPE cells promotes choroidal neovascularization (CNV), (2) whether inflammasome activation in CNV occurs via NLRP3 or also through NLRP3-independent mechanisms, and (3) whether complement activation induces inflammasome activation in CNV.

Here we show in a neovascular AMD mouse model that NLRP3 inflammasome activation in non-RPE cells but not in RPE cells promotes CNV. We demonstrate that both NLRP3-dependent and NLRP3-independent inflammasome activation mechanisms induce CNV. Finally, we find that complement and inflammasomes promote CNV through independent mechanisms. Our findings uncover an unexpected role of non-NLRP3 inflammasomes for CNV and suggest that combination therapies targeting inflammasomes and complement may offer synergistic benefits to inhibit CNV.

Link: https://doi.org/10.7554/eLife.60194

The researchers involved in today's research have been investigating the role of prostaglandin E2 (PGE2) in muscle stem cell function for some years. PGE2 levels decline with age, and this appears to be sufficient to cause a sizable fraction of the characteristic loss of muscle mass and strength that accompanies aging, a condition known as sarcopenia. Other lines of evidence point to loss of stem cell function in muscle tissue as the most important proximate cause of sarcopenia.

The best way to establish whether or not a mechanism is important in aging and loss of function is to block, remove, or reverse it and see what happens. Thus researchers identified 15-PGDH as a regulator of PGE2; forcing a reduction in 15-PGDH levels in old mice causes an increase in PGE2 to youthful levels, and a corresponding improvement in muscle function. This may be mediated in part by improved stem cell function, but the data from treated mice, such as the improved mitochondrial function observed in muscle cells, shows that other mechanisms are involved as well.

Small molecule restores muscle strength, boosts endurance in old mice, study finds

Previously, researchers found that a molecule called prostaglandin E2 can activate muscle stem cells that spring into action to repair damaged muscle fibers. "We wondered whether this same pathway might also be important in aging. We were surprised to find that PGE2 not only augments the function of stem cells in regeneration, but also acts on mature muscle fibers. It has a potent dual role." Prostaglandin E2 levels are regulated by 15-PGDH, which breaks down prostaglandin E2. The researchers used a highly sensitive version of mass spectrometry, a method for differentiating closely related molecules, to determine that compared with young mice, the 15-PGDH levels are elevated in the muscles of older animals, and the levels of prostaglandin E2 are lower. They found a similar pattern of 15-PGDH expression in human muscle tissues, as those from people in their 70s and early 80s expressed higher levels than those from people in their mid-20s.

The researchers administered a small molecule that blocks the activity of 15-PGDH to the mice daily for one month and assessed the effect of the treatment on the old and young animals. "We found that, in old mice, even just partially inhibiting 15-PGDH restored prostaglandin E2 to physiological levels found in younger mice. The muscle fibers in these mice grew larger, and were stronger, than before the treatment. The mitochondria were more numerous, and looked and functioned like mitochondria in young muscle." Treated animals were also able to run longer on a treadmill than untreated animals. When researchers performed the reverse experiment - overexpressing 15-PGDH in young mice - the opposite occurred. The animals lost muscle tone and strength, and their muscle fibers shrank and became weaker, like those of old animals.

Finally, the researchers observed the effect of prostaglandin E2 on human myotubes -immature muscle fibers - growing in a lab dish. They found that treating the myotubes with prostaglandin E2 caused them to increase in diameter, and protein synthesis in the myotubes was increased - evidence that prostaglandin E2 worked directly on the muscle cells, not on other cells in the tissue microenvironment. "It's clear that this one regulator, 15-PGDH, has a profound effect on muscle function. We're hopeful that these findings may lead to new ways to improve human health and impact the quality of life for many people. That's one of my main goals."

Advanced-glycation end products (AGEs) cause issues in two major ways. Firstly a few species of persistent AGE can cross-link molecules of the extracellular matrix, changing tissue properties in harmful ways, such as loss of elasticity in blood vessels and skin. Secondly, more prevalent short-lived AGEs can provoke chronic inflammation through their interaction with the receptor for AGEs, RAGE. This is thought to be an important contributing cause of chronic inflammation in metabolic conditions such as diabetes, but also shows up as a concern in a number of other conditions. As illustrated in this review, the research community is interested in finding ways to reduce or interfere in inflammatory AGE-RAGE signaling. There is a great deal more work taking place in this part of the field than in the search for ways to break persistent AGE cross-links.

Advanced-glycation end products (AGEs) are heterogeneous molecules derived from post-translational nonenzymatic modifications of macromolecules including proteins, lipids, and nucleic acids by glucose or other saccharides (fructose and pentose). AGEs are deleterious molecules and are found to be increased in the plasma of physiological aging and age-related diseases, diabetes mellitus, and autoimmune/inflammatory rheumatic diseases.

AGEs, by binding to receptors for AGE (RAGEs), alter innate and adaptive immune responses to induce inflammation and immunosuppression via the generation of proinflammatory cytokines, reactive oxygen species (ROS), and reactive nitrogen intermediates (RNI). These pathological molecules cause damage to vascular endothelial, smooth muscular, and connective tissue cells and renal mesangial, endothelial, and podocytic cells in AGE-related diseases. In this context, oxidative stress can disturb intracellular signals to become pathological states, particularly insulin-mediated metabolic responses and insulin resistance.

AGEs contribute to the development of physiological aging and many major chronic diseases, including diabetic pathology, and neurodegenerative, autoimmune/inflammatory, and metabolic cardiovascular diseases. Accordingly, it is valuable to search for novel therapeutic interventions for AGE-related diseases. The underlying modes of action of different AGE inhibitors are based on the attenuation of glycosylation, antioxidative stress, metal ion chelating, and scavengers of reactive 1,2-dicarbonyl compounds or ROS/RNI. Arbitrarily, these novel therapeutic AGE inhibitors can be classified into 4 categories: (1) inhibitors of AGE formation; (2) breakers of preformed AGEs; (3) blockades of AGE-RAGE axis signaling; and (4) inducers of intracellular glyoxalase, ubiquitin-proteasome, and autophagy pathways.

Link: https://doi.org/10.3390/molecules25235591

This open access paper argues for the importance of mitochondrial dysfunction in the brain to the onset of neurodegenerative conditions. The primary function of mitochondria, a herd of these bacteria-like organelles found in every cell, is the production of adenosine triphosphate (ATP), a chemical energy store molecule. The energy stored in ATP is used to power cellular operations. It is thus vital in every tissue, but particularly so in the most energy-hungry tissues, such as brain and muscle.

With advancing age, mitochondria become dysfunctional throughout the body, and ATP production falters as a consequence. A network of interacting contributing causes is involved, such as loss of NAD, changes in gene expression that cause quality control mechanism of mitophagy responsible for removing worn and damaged mitochondria, and damage to mitochondrial DNA. Effective means of addressing age-related mitochondrial dysfunction is an important topic in rejuvenation research.

There is a growing body of evidence that indicates that the aging of the brain results from the decline of energy metabolism. In particular, the neuronal metabolism of glucose declines steadily, resulting in a growing deficit of adenosine triphosphate (ATP) production - which, in turn, limits glucose access. This vicious circle of energy metabolism at the cellular level is evoked by a rising deficiency of nicotinamide adenine dinucleotide (NAD) in the mitochondrial salvage pathway and subsequent impairment of the Krebs cycle. A decreasing NAD level also impoverishes the activity of NAD-dependent enzymes that augments genetic errors and initiate processes of neuronal degeneration and death.

This sequence of events is characteristic of several brain structures in which neurons have the highest energy metabolism. Neurons of the cerebral cortex and basal ganglia with long unmyelinated axons and these with numerous synaptic junctions are particularly prone to senescence and neurodegeneration. Unfortunately, functional deficits of neurodegeneration are initially well-compensated, therefore, clinical symptoms are recognized too late when the damages to the brain structures are already irreversible. Therefore, future treatment strategies in neurodegenerative disorders should focus on energy metabolism and compensation age-related NAD deficit in neurons.

Link: https://doi.org/10.3390/metabo10110450

Hypothetically, if one could prevent all of the detrimental reactions a cell undergoes in response to a specific disease-causing agent, would that cure the resulting disease? Clearly some disease causing agents are just plain destructive, and further detrimental cellular reactions to that destruction are not the important component of the condition. Are there categories of condition in which the problem is largely a matter of inappropriate cellular reactions to an otherwise innocuous agent, however? In those cases, preventing that reaction could be a viable approach to therapy - with the caveat that a truly innocuous agent is an unlikely circumstance. All aspects of cellular biochemistry act in multiple ways, and that includes pathogens, persistent metabolic waste, excessive inflammatory signaling, and so forth. Blocking one detrimental reaction to an agent still leaves all of the other reactions in place, known and unknown.

Cell behavior is governed by epigenetic mechanisms that determine which proteins are produced and in what quantity. This is a complex, dynamic system of feedback between protein production, environment, and cell activity. Is it possible in principle and practice to adjust specific parts of the epigenetic system in order to steer cells away from a detrimental reaction involved in disease progression? Yes, as today's research materials illustrate. We will likely see much more of this class of approach in the future. It is analogous to widely used strategies such as blocking specific cell surface receptors or suppressing production of specific proteins. All attempt to interfere beneficially in the downstream effects of disease causing agents, in the reactions of cells, without addressing the agents themselves.

Memory deficits resulting from epigenetic changes in Alzheimer's can be reversed

Memory loss associated with Alzheimer's disease (AD) may be able to be restored by inhibiting certain enzymes involved in abnormal gene transcription, according to a preclinical study. Alzheimer's disease alters the expression of genes in the prefrontal cortex, a key region of the brain controlling cognitive processes and executive functions. By focusing on gene changes caused by epigenetic processes (those that are not related to changes in DNA sequences) such as aging, the UB researchers were able to reverse elevated levels of harmful genes that cause memory deficits in AD.

Transcription of genes is regulated by an important process called histone modification, where histones, the proteins that help package DNA into chromosomes, are modified to make that packaging looser or tighter. The nature of the packaging, in turn, controls how genetic material gains access to a cell's transcriptional machinery, which can result in the activation or suppression of certain genes. Researchers found that H3K4me3, a histone modification called histone trimethylation at the amino acid lysine 4, which is linked to the activation of gene transcription, is significantly elevated in the prefrontal cortex of people with AD and mouse models of the disease. That epigenetic change is linked to the abnormally high level of histone-modifying enzymes that catalyze the modification known as H3K4me3. Researchers found that when the AD mouse models were treated with a compound that inhibits those enzymes, they exhibited significantly improved cognitive function.

In making that discovery, the UB team also identified a number of new target genes, including Sgk1 as a top-ranking target gene of the epigenetic alteration in AD. Sgk1 transcription is significantly elevated in the prefrontal cortex of people with AD and in animal models with the disorder. Researchers found that abnormal histone methylation at Sgk1 contributes to its elevated expression in AD. Sgk1 encodes an enzyme activated by cell stress, which plays a key role in numerous processes, such as regulating ion channels, enzyme activity, gene transcription, hormone release, neuroexcitability, and cell death. The researchers found it is highly connected to other altered genes in AD, suggesting it may function as a kind of hub that interacts with many molecular components to control disease progress.

"In this study, we have found that administration of a specific Sgk1 inhibitor significantly reduces the dysregulated form of tau protein that is a pathological hallmark of AD, restores prefrontal cortical synaptic function, and mitigates memory deficits in an AD model. These results have identified Sgk1 as a potential key target for therapeutic intervention of AD, which may have specific and precise effects."

Targeting histone K4 trimethylation for treatment of cognitive and synaptic deficits in mouse models of Alzheimer's disease

Epigenetic aberration is implicated in aging and neurodegeneration. Using postmortem tissues from patients with Alzheimer's disease (AD) and AD mouse models, we have found that the permissive histone mark H3K4me3 and its catalyzing enzymes are significantly elevated in the prefrontal cortex (PFC). Inhibiting H3K4-specific methyltransferases with the compound WDR5-0103 leads to the substantial recovery of PFC synaptic function and memory-related behaviors in AD mice. Among the up-regulated genes reversed by WDR5-0103 treatment in PFC of AD mice, many have the increased H3K4me3 enrichment at their promoters. One of the identified top-ranking target genes, Sgk1 is also significantly elevated in PFC of patients with AD. Administration of a specific Sgk1 inhibitor reduces hyperphosphorylated tau protein, restores PFC glutamatergic synaptic function, and ameliorates memory deficits in AD mice. These results have found a novel epigenetic mechanism and a potential therapeutic strategy for AD and related neurodegenerative disorders.

The presence and function of circular RNAs in cells is comparatively poorly understood. The expression levels of at least some circular RNAs appear to change with age. This suggests that, even without a full understanding of function, it might be possible to use this data as the basis for a biomarker of aging. It is already the case that other biomarkers of aging have been constructed from weighted combinations of age-related changes in the broader transcriptome of RNA expression. These join aging clocks built from epigenetic and proteomic data, all of which exhibit changes that are characteristic of age.

The commonality between all of these approaches is that it remains very unclear as to exactly how the causes of aging, the underlying forms of molecular damage, lead to specific changes in the epigenome, transcriptome, or proteome. These measures of biological age are black boxes at present, and thus hard to use as assessments for the effectiveness of any given approach to rejuvenation. Perhaps they reflect only a few of the mechanisms of aging, or give a great deal of weight to one over another, for example. We just don't know yet.

Circular RNAs (circRNAs), a novel type of universal and diverse endogenous transcripts that has been a recent focus in the transcriptomics field, were first observed through an electron microscope in the cytoplasm of eukaryotic cells in 1979. CircRNAs form covalently closed loop structures and are more stable than linear RNAs, insusceptible to degradation by RNA exonuclease or RNase R. Subsequent reports revealed that circRNAs can act as miRNA sponges, transcriptional regulators, binding partners of proteins, or even translated into functional proteins. Furthermore, circRNAs are abundant, relatively stable, specifically expressed in tissues, and evolutionary conserved among species, affording them the potential to be biomarkers for human diseases.

Recent studies have identified several circRNAs as regulators of various pathways that are involved in aging and cellular senescence. In particular, dysregulated circRNAs were implicated in the pathophysiology of age-related diseases, including cerebrovascular disease, neurodegenerative disease, cancer, diabetes, rheumatoid arthritis, and osteoporosis.

In recent years, circRNAs have gradually become one of the most prominent targets in the field of transcriptomics because of their critical roles in the regulation of gene expression and development of several diseases. The characteristic stability, abundance, and tissue-specific expression of circRNAs confer them great potential for use as biomarkers of various diseases. Notably, circRNAs can exist in the exosomes and plasma due to their excellent stability, thus, providing a more convenient way for diagnosing pathologies. Further investigations regarding the function and mechanism underlying the associations between circRNAs and age-related diseases are required.

Link: https://doi.org/10.14336/AD.2020.0309

There is at present a diverse exploration of clocks that assess biological age, these clocks constructed as weighted combinations of data picked from the epigenome, transcriptome, or proteome, all of which change in characteristic ways with age. Many different clocks are at various stages of development and refinement. The goal is the production of a robust, low-cost, rapid way to assess the efficacy of potential rejuvenation therapies: if one can use a blood test ten days before and ten days after a treatment, that would be a great deal easier than having to wait and see over the course of a life span.

Unfortunately, this goal remains a future phase of development for this class of technology. Given that there is no good understanding of exactly which processes of molecular damage cause specific changes in the epigenome, transcriptome, and proteome, every algorithm must be calibrated against a potential treatment before it can be used to assess that treatment. Which somewhat defeats the point, as the only way to calibrate it is to run the slow, expensive life span studies that we'd all like to avoid. Still, the research community is presently energetically engaged in improving on present approaches to the production of clock algorithms, as illustrated by the example here.

Researchers have produced DeepMAge, a novel aging clock that was trained to predict human age on more than 6000 DNA methylation profiles. By analyzing the methylation patterns it can estimate human age within a 3-year error margin, which is more accurate than any other human aging clock. Aging clocks boom started in 2013 when the first DNA methylation aging clocks by Horvath and Hannum were published. They have proven to be an indispensable tool in aging research, letting scientists understand its mechanisms and develop longevity interventions.

Unlike its predecessors, DeepMAge is a neural network that may prove to be more efficient in some other ways apart from prediction accuracy. In the original paper, DeepMAge deems people with certain conditions to be older, which may be useful for the development of early diagnostics tools. For example, women with ovarian cancer are on average predicted 1.7 years older than healthy women of the same chronological age, and likewise, multiple sclerosis patients are predicted 2.1 years older. Similar results have been obtained for several other conditions: irritable bowel diseases, dementia, obesity.

Higher age predictions indicate a faster pace of aging in these conditions, which begs the question: is a higher aging rate a precondition to them or is it just an epigenetic footprint of the harm they cause? The authors plan to further investigate the links between epigenetics and longevity using DeepMAge. "Aging clocks have come a long way since the first works by Horvath and Hannum in 2013. We are happy to contribute to this research field. Now, we are going to explore how epigenetic aging can be slowed down with the interventions available to consumers."

Link: https://www.eurekalert.org/pub_releases/2020-12/dll-dlp120720.php

Today's open access research reports a sizable effect on sarcopenia in aged mice via blockade of TNFα, an inflammatory signal molecule associated with cellular senescence and generated by senescent cells. Sarcopenia is the progressive loss of muscle mass and strength that takes place with age, more severely in some individuals than in others, but everyone is affected. The drug used in the study is Etanercept, already widely employed to treat autoimmune conditions. It functions as a decoy receptor, binding circulating TNFα to prevent it from interacting with cell receptors to trigger detrimental changes in cell behavior. The outcome of note is that treated mice maintain muscle volume from 12 to 22 months of age, while controls lose ~20% of muscle volume over the same period.

Etanercept is not a drug that one would take for the long term on a whim. Like most existing approaches to suppressing immune overactivation in autoimmune conditions, it is a blunt tool. It suppresses immune signaling and activity across the board, both necessary and inappropriate, and the side effects thus include a potentially dangerous weakening of the immune response to infection. In this case the drug is a tool for the purposes of research, not a potential treatment. It is used to produce what looks a lot like a confirmation of the role of senescent cell accumulation and consequent chronic inflammatory signaling in the onset of sarcopenia with age. One possible way to remove a sizable portion of the harmful TNFα signaling, without disrupting the beneficial TNFα signaling, is to get rid of senescent cells.

Senescent cells accumulate with age, lingering where they should be destroyed, either by programmed cell death or by the immune system. These errant cells generate the senescence-associated secretory phenotype (SASP), a mix of inflammatory, pro-growth, and other signals. When sustained over the long term, the SASP is very disruptive of tissue and immune function, a sizable contributing factor in age-related degeneration. TNFα features prominently in the SASP, so while that connection isn't called out in this paper, it seems likely that one could use senolytic therapies that selectively destroy senescent cells in order to prevent sarcopenia.

Pharmacological blockade of TNFα prevents sarcopenia and prolongs survival in aging mice

Aging is accompanied by chronic low-grade inflammation ("inflammaging"), which could have a causal role in sarcopenia. Tumor necrosis factor-α (TNFα), interleukin-6 (IL-6), interleukin-10, and interleukin-15 might contribute to the loss of muscle mass. TNFα is a particularly interesting candidate, being a non-redundant target in inflammatory human diseases associated to complex multi-cytokine inflammatory responses. In addition, TNFα is known to promote muscle wasting and cachexia by promoting protein degradation while decreasing protein synthesis and by inhibiting muscle regeneration by blocking proliferation and differentiation of muscle stem cells. In aged muscle, this inhibition seems to be preferentially mediated by TNFα released by bone marrow-derived leukocytes and TNFα genetic knockdown protects against aging-induced fiber loss and reduction of stem cell regenerative capacity. TNFα also promotes apoptosis of both type I and type II muscle fibers.

Etanercept is a dimeric fusion protein that acts as soluble receptor interfering with TNFα binding to tissue receptors and has been employed for the treatment of autoimmune diseases for over two decades, with excellent efficacy and safety profiles. We evaluated the effects of TNFα blockade on spontaneous aging in wild type mice aged 16 to 28 months (corresponding to 50-90 years of human age). This treatment quenched age-associated spontaneous muscle loss, reduced fiber type shift, improved muscle function, and modestly increased animal life span.

We found that spontaneous aging in mice reflects many features of human aging at the skeletal muscle level. Specifically, we observed that between 12 and 28 months of age, corresponding to 40-90 years of age in humans, aging mice lost weight and muscle mass. This was accompanied by progressive reduction of fiber cross-sectional area and of mouse endurance during exercise. Fiber size decline from 12 to 22 months was severe and further worsened at 28 months. Accordingly, MRI-measured muscle volume and body weight decreased starting from month 22 of age. The cells of innate and acquired immunity were consistently detectable in skeletal muscle at 22 months of age and remained stable thereafter. The concentration of circulating cytokines followed comparable kinetics. This suggests that inflammation could start early in aged mice, reaching a "steady state" at a low level for an extended period.

Cells in aged tissue are characterized by a state of oxidative stress, the presence of excessive numbers of oxidizing molecules that damage cell structures by reacting with them. Oxidative stress goes hand in hand with chronic inflammation and mitochondrial dysfunction, both of which are also features of aged tissues. For any universal state of this nature, one can then link it to many varied conditions, even those that might initially appear to have very little to do with one another. That is the case here in this consideration of commonalities between depression and stroke.

A significant percentage of older individuals develop one or more age-related diseases, which may include two leading diseases characterized by high incidence and disability: stroke and depression. Between 2006 and 2016, the actual number of stroke deaths increased 3.7%, although the age-adjusted mortality rate decreased 16.7% due to the large increase in the number of elderly people. Like stroke, another disease that affects a significant proportion of the population is depression. The 12-month prevalence of major depressive disorder (MDD) is about 6%, while the lifetime risk of MDD is nearly 15-18%. Moreover, older age is identified as a consistent and important risk factor for a worse prognosis. This phenomenon may be associated with the effect of cognitive impairment.

Over the past two decades, studies have identified the role of oxidative stress (OS) in these two diseases. Recently, preclinical experiments and clinical trials have focused on studying the efficacy of antioxidants and combined therapy with antidepressants in stroke or depressed patients. OS describes a state in which the body produces excessive reactive oxygen species (ROS) and reactive nitrogen species (RNS) in response to deleterious substances. Under physiological conditions, moderate OS activity is necessary for body health. Toxic effects derived from ROS and RNS can be ameliorated or neutralized by free radical (FR) scavengers and the antioxidant system. However, when a large number of ROS and RNS are generated, excessive FR then induce molecular oxidation, cell membrane modification, and enzyme inactivation, resulting in cellular damage and functional decline.

There is a close link between oxidative stress and aging, and this link can be proven through many related mechanisms. Firstly, age-related cognitive decline is a consequence of increased OS and neuroinflammation activity in the the aging hippocampus, and a consequence of reduced neurogenesis and synaptic plasticity. Furthermore, mutual effects of inflammation and OS are observed to exacerbate the aging brain. Inflammation stimulates both macrophages and microglia to generate mitochondrial ROS to cause cognitive decline, whereas OS-damaged cells produce inflammatory mediators to promote microglial aging. Secondly, aging and OS can damage the brain by negatively affecting neuroplasticity, brain homeostasis, and cognitive function.

OS lies in the center of the "aging-stroke-depression" network. First, when stroke occurs in animals or patients, excessive generation of ROS follows, leading to cellular damage and brain injury. Second, OS mediates inflammation, apoptosis, and the microbiota-gut-brain axis to increase the accumulation of ROS, followed by brain deterioration. Third, aging acts as a risk factor and aggravates the development of stroke and depression via OS and OS-induced pathways. Due to the central role of OS in this network, administration of antioxidants seems to provide therapeutic ways for stroke and depression.

Link: https://doi.org/10.14336/AD.2020.0225

Here find a perspective on the great importance of a functional immune system to health in later life. Many of the declines of aging appear strongly influenced, at the very least, by the progressive disarray of the immune system. It becomes less competent in destroying pathogens and malfunctioning cells, but at the same time ever more active in response to the molecular damage and cellular dysfunction accompanying aging. That inappropriate activity takes the form of chronic inflammation that disrupts tissue function and accelerates the onset and progression of all of the common age-related conditions.

The interrelation of the processes of immunity and senescence now receives an unprecedented emphasis during the COVID-19 pandemic, which brings to the fore the critical need to combat immunosenescence and improve the immune function and resilience of older persons. Here we review the historical origins and the current state of the science of innate and adaptive immunity in aging and longevity. Following a century of study, at the present time, natural immunity is understood to consist of three interrelated parts: physiological barriers, innate immunity, and adaptive immunity. All of these are affected by aging. Immunosenescence results in increased susceptibility and severity of infectious diseases and non-communicable age-associated diseases, among them cancer, cardiovascular disease, and autoimmunity.

Excessive levels or activity of antimicrobial peptides, C-reactive protein, complement system, TLR/NF-κB, cGAS/STING/IFN and AGEs/RAGE pathways, myeloid cells and NLRP3 inflammasome, declined levels of NK cells in innate immunity, thymus involution and decreased amount of naive T-cells in adaptive immunity, are biomarkers of aging and predisposition factors for cellular senescence and aging-related pathologies. Long-living species, human centenarians, and women are characterized by less inflammaging and decelerated immunosenescence. Despite recent progress in understanding, a harmonious theory of immunosenescence is still developing. Geroprotectors targeting these mechanisms are just emerging, including rapamycin, senolytics, metformin, acarbose, spermidine, NAD+ enhancers, and lithium.

Link: https://doi.org/10.14336/AD.2020.0603

Replacing Aging is a forthcoming book on the treatment of aging as a medical condition. It is presented as putting forward a similar point of view to that found in Ending Aging by Aubrey de Grey and Michael Rae, meaning that the research and medical communities should place a relentless focus on damage and repair of damage. Aging is caused by an accumulation of molecular damage of a few distinct classes in and around cells, that damage spiraling out into a complex network of interacting downstream consequences.

Fully understanding that network, fully understanding the progression of aging, will take the rest of this century, or longer. The root causes of aging, these forms of damage that arise from the normal operation of a youthful metabolism, are much less complex in comparison, and, at this time, are far better understood. Therapies resulting in large benefits, such as significant extension of healthy life and significant reversal of age-related disease, are more likely to arise from work on the causes of aging than from work on understanding the complicated progression of aging. That much is in the process of being demonstrated by senolytics that destroy senescent cells.

Unfortunately, the research community is still largely focused on understanding the intricacies of aging, picking apart the details of the complex, damaged disarray of an aged metabolism, and aiming at no more than a modest slowing of aging. There is comparatively little interest in applying what is already known of the causes of aging. That must change.

Replacing Aging

Replacing Aging outlines how aging will soon be reversible as a result of the advances that are being made in regenerative medicine. The book explains the enormous complexity of aging and how the accumulation of myriad types of macromolecular damage in the body essentially precludes a pharmacological solution to the problem of aging. Nevertheless drugs remain the primary focus of the anti-aging field. Instead of drugs, a decisive way to erase all forms of age-related macromolecular damage at once would be by replacing old worn-out tissues with new young ones. As the book describes, an ability to replace all body parts seems more and more likely, if not inevitable.

Regenerative medicine is developing increasingly functional lab-grown cells, tissues, and organs that are being transplanted into patients today to treat diseases or repair damage. With continued improvements, cells and organs could be used in a more comprehensive manner to replace all body parts and reset the aging clock to near zero. Even the brain can be progressively replaced at a cellular level over time without a loss of self-identity. Existing examples demonstrate that complex brain functions can if given enough time change their neural substrates. And new brain cells added to old brains can form remarkably normal connection patterns. These findings together suggest protocols for brain rejuvenation. Thus, this book heralds the day in the near future when, if we choose to, we will be able to live much longer healthier lives as a result of replacements made possible by regenerative medicine.

Is Longevity actually just Replacing Aging?

"I was a bit of a weird kid growing up. I realized at a young age, in early elementary school in fact, that we are biological machines and that even if we stay healthy, we will eventually break down with time. I didn't like this and wanted to do something about it, so I knew I wanted to be a molecular biologist working on longevity before I even knew that the words "molecular biology" and "longevity" existed. Then in high school, I started reading on my own everything I could about how we function at a molecular level."

"Macromolecular damage is aging, at least from a biologist's perspective. Any other definition such as motor, immune, cognitive performance, for example can lead to claims of rejuvenation while the actual process of macromolecular and cellular decay proceeds without hinderance. This is an important point in the book because many in the aging field use only indirect markers of aging and are open to misinterpretation and false claims."

Aubrey de Grey's Review of "Replacing Aging"

The key to understanding that aging is not a mystery is to understand that it is not a phenomenon of biology, but of physics: it is fundamentally the same thing in a living organism as it is in a car, or an aeroplane, or any man-made machine. Once one realises that, it is a small step to realising that the approach we take - with dramatic success, when we try - to preserving the function of a car is sure to work just as well on the human body, once we develop the corresponding techniques to a level that matches the greater complexity of living organisms.

The author wastes no time in highlighting this key point - not merely in the abstract, but by getting down to specifics. He notes that the way we keep a car going is by preventative maintenance - damage repair. In other words, by maintaining the overall structure and composition of the car as it was initially. And that, of course, what inspires the title of the book, because preventative maintenance is largely about replacing worn or damaged parts.

The world needs far more books like Replacing Aging. In the past year or so, a few other gerontologists have published general-audience books explaining what this field is about and why it is so promising right now - and they all have different styles and will benefit different audiences to different degrees. In my view, Replacing Aging stands out as a shining example of how to get the public to break free of the fatalistic shackles that are so impeding the crusade to create a post-aging world.

One of the more intriguing findings to emerge from study of the relationship between stress response mechanisms in cellular metabolism and the pace of degenerative aging is that evolution has not optimized for life span. Many aspects of metabolism can be adjusted in small ways - in mice, worms, flies, and so forth - in order to modestly slow aging. Yet these small changes are well within the bounds of what one would expect evolution to have already produced. Why didn't that happen? A long life and lasting health are just not high in the list of important pressures on evolutionary selection, it seems. Thus we have autophagy, an important collection of cellular maintenance mechanisms that run suboptimally in near every species. Make autophagy somewhat more efficient, up to a point, and health and life span improve.

The increasing number of people living with age-related diseases underscores the importance of ageing research to improve healthspan. Two well-studied evolutionary conserved interventions that extend lifespan and improve health are dietary restriction and down-regulation of nutrient sensing pathways, such as glucose sensing by insulin and amino acid sensing by the target-of-rapamycin signalling pathway. One common characteristic of these anti-ageing interventions is an increase in autophagy, a cellular pathway that degrades damaged proteins and organelles to supply essential building blocks and energy.

To help provide a more direct link between autophagy and healthy ageing, we fine-tuned overexpression of Atg1 kinase, which is critical for autophagy induction, and measured its effect on longevity in the fruit fly Drosophila. Interestingly, we observed that a moderate increase in autophagy is beneficial in extending healthy lifespan, whereas strong autophagy up-regulation is detrimental and leads to progressive lipid loss and decreased lifespan. Moderate and stronger Atg1 overexpression displayed opposing transcriptional profiles of mitochondrial genes, being upregulated in long-lived and down-regulated in short-lived Atg1 over-expressing animals. Overall, we provide a detailed description of the phenotypes associated with varying degrees of autophagy up-regulation in vivo, demonstrating that autophagy enhancement delays ageing only when applied in moderation.

Link: https://doi.org/10.1371/journal.pgen.1009083

It is thought that the burden of senescent cells is likely correlated with survival in many cancers. Senescent cells cease to replicate and begin to secrete pro-growth, pro-inflammation signals. Most senescent cells are rapidly destroyed by the immune system, but this process slows with age and thus senescent cells accumulate. Cellular senescence does act to suppress cancer in its earliest stages, by removing those cells most likely to become cancerous. Once a significant number of senescent cells are present, however, their signaling begins to aid cancer growth. Thus we might expect to see that the application of senolytic therapies, capable of selectively destroying senescent cells, will slow down the progression of cancer in many cases. The standard classes of cancer therapy, those that work by damaging cells quite aggressively, have the side-effect of inducing greater levels of cellular senescence throughout the body. They may all become more effective when paired with senolytics.

How well women with cervical cancer respond to treatment and survive correlates with the level of 10 proteins in their blood that also are associated with a cell state called senescence. Researchers looked at pretreatment levels of these proteins in the blood of 565 women with stage 2 and 3 cervical cancer, who received standard treatments of internal radiation, called brachytherapy, external radiation, or both. They found that women with low levels of the proteins secreted by senescent cells had higher survival rates than those with high levels of these senescence-associated secreted phenotypes, or SASPs.

Additionally researchers found that brachytherapy, which implants a radiation source close to the cervix, greatly improved survival of patients who had high levels of these SASPs but had little impact on those with low levels. "These results demonstrate that cellular senescence is a major determining factor for survival and therapeutic response in cervical cancer, and suggest that senescence reduction therapy may be an efficacious strategy to improve the therapeutic outcome of cervical cancer." In women with moderate to high blood levels of SASPs, use of a class of drugs called senolytics - which target these cells for elimination and are under study to improve age-related problems and disease - as an adjunct therapy could help.

While cancer cells more typically are associated with rapid reproduction that enables cancer's growth, senescent cells cannot divide and reproduce. The proteins these senescent cancer cells are secreting helps create an inflammatory state in which cancer thrives and helps lay the groundwork for cancer spread. It also provides some protection from radiation therapy, which like chemotherapy, works in part by killing off typically rapidly dividing cancer cells. "The senescent proteins really change how cancer cells may respond to therapy."

Link: https://jagwire.augusta.edu/cervical-cancer-survival-may-improve-by-targeting-senescent-zombie-cells/

Neurodegenerative conditions are characterized by increasing amounts of molecular waste in the brain, such as amyloid-β, α-synuclein, tau, and a few others. In the case of Alzheimer's disease, evidence suggests that the condition starts because the drainage of cerebrospinal fluid (CSF) out of the brain through the cribriform plate declines with age. The plate becomes ossified and less porous as the inflammatory, altered biochemistry of aging changes cell behavior for the worse. This loss of drainage allows many varied forms of molecular waste to build up to harmful levels in at least some parts of the brain.

The cribriform plate isn't the only path by which CSF drains from the brain, but it is the one that drains the area of the brain, the olfactory bulb, where Alzheimer's pathology and amyloid-β aggregation first develops. The biotech startup Leucadia Theraputics was founded to develop assays and therapies based on this view of the origin of Alzheimer's disease. The staff there have demonstrated - in ferrets rather than mice, because mice don't normally exhibit any of the biochemistry of Alzheimer's disease - that artificially blocking drainage through the cribriform plate causes an accelerated buildup of molecular waste and cognitive impairment.

Today's open access materials, from another team, provide good supporting evidence for the CSF drainage view of Alzheimer's disease. The researchers show that the ossification of the cribriform plate with age in mice clearly reduces CSF drainage. We'd expect to see much the same in other mammalian species. Given a model like this, it would be interesting to see whether or not cognitive decline in normal aged mice correlates in any way with CSF flow through the cribriform plate. Given the lack of naturally occurring Alzheimer's mechanisms in mice, and the presence of other drainage pathways that are less impacted by age, that could go either way.

Cerebrospinal fluid drainage kinetics across the cribriform plate are reduced with aging

Continuous circulation and drainage of cerebrospinal fluid (CSF) are essential for the elimination of CSF-borne metabolic products and neuronal function. While multiple CSF drainage pathways have been identified, the significance of each to normal drainage and whether there are differential changes at CSF outflow regions in the aging brain are unclear.

Here, dynamic in vivo imaging of near infrared fluorescently-labeled albumin was used to simultaneously visualize the flow of CSF at outflow regions on the dorsal side (transcranial and -spinal) of the central nervous system. This was followed by kinetic analysis, which included the elimination rate constants for these regions. In addition, tracer distribution in ex vivo tissues were assessed, including the nasal/cribriform region, dorsal and ventral surfaces of the brain, spinal cord, cranial dura, skull base, optic and trigeminal nerves and cervical lymph nodes.

Based on the in vivo data, there was evidence of CSF elimination, as determined by the rate of clearance, from the nasal route across the cribriform plate and spinal subarachnoid space, but not from the dorsal dural regions. Using ex vivo tissue samples, the presence of tracer was confirmed in the cribriform area and olfactory regions, around pial blood vessels, spinal subarachnoid space, spinal cord and cervical lymph nodes, but not for the dorsal dura, skull base, or the other cranial nerves. Also, ex vivo tissues showed retention of tracer along brain fissures and regions associated with cisterns on the brain surfaces, but not in the brain parenchyma. Aging reduced CSF elimination across the cribriform plate but not that from the spinal SAS nor retention on the brain surfaces.

Collectively, these data show that the main CSF outflow sites were the nasal region across the cribriform plate and from the spinal regions in mice. In young adult mice, the contribution of the nasal and cribriform route to outflow was much higher than from the spinal regions. In older mice, the contribution of the nasal route to CSF outflow was reduced significantly but not for the spinal routes. This kinetic approach may have significance in determining early changes in CSF drainage in neurological disorder, age-related cognitive decline, and brain diseases.

Researchers here show that upregulation of HAND2 in sympathetic neurons has the effect of slowing sarcopenia in late life, the loss of muscle mass and strength that leads to frailty. One contributing cause of sarcopenia is the deterioration of the neuromuscular junctions that link the nervous system with muscle tissue. This approach slows that deterioration, with a corresponding slowing of loss of muscle function, and thus puts some numbers to the importance of that causes versus, say, loss of stem cell function.

Sarcopenia, or age-dependent decline in muscle force and power, impairs mobility, increasing the risk of falls, institutionalization, co-morbidity, and premature death. The discovery of adrenoceptors, which mediate the effects of the sympathetic nervous system (SNS) neurotransmitter norepinephrine on specific tissues, sparked the development of sympathomimetics that have profound influence on skeletal muscle mass. However, chronic administration has serious side effects that preclude their use for muscle-wasting conditions. Interventions that can adjust neurotransmitter release to changing physiological demands depend on understanding how the SNS affects neuromuscular transmission, muscle motor innervation, and muscle mass.

We examined age-dependent expression of the heart and neural crest derivative 2 (Hand2), a critical transcription factor for SN maintenance, and we tested the possibility that inducing its expression exclusively in sympathetic neurons (SN) will prevent (i) motor denervation, (ii) impaired neuromuscular junction (NMJ) transmission, and (iii) loss of muscle mass and function in old mice. To test this hypothesis, we delivered a viral vector carrying Hand2 expression or an empty vector exclusively in SNs by vein injection in 16-month-old C57BL/6 mice that were sacrificed 6 months later.

Hand2 expression declines throughout life, but inducing its expression increased (i) the number and size of SNs, (ii) muscle sympathetic innervation, (iii) muscle weight and force and whole-body strength, (iv) myofiber size but not muscle fibre-type composition, (v) NMJ transmission and nerve-evoked muscle force, and (vi) motor innervation in old mice. Additionally, the SN controls a set of genes to reduce inflammation and to promote transcription factor activity, cell signalling, and synapse in the skeletal muscle. Hand2 DNA methylation may contribute, at least partially, to gene silencing.

Further, selective expression of Hand2 in the mouse SNs from middle age through old age increases muscle mass and force by (i) regulating skeletal muscle sympathetic and motor innervation; (ii) improving acetylcholine receptor stability and NMJ transmission; (iii) preventing inflammation and myofibrillar protein degradation; (iv) increasing autophagy; and (v) probably enhancing protein synthesis.

Link: https://doi.org/10.1002/jcsm.12644

Here, researchers note some of the challenges inherent in trying to analyze data on human inheritance of longevity; it isn't as easy as it sounds. Considerable effort has gone into analysis of long-lived families to try to identify genetic variants that might explain why some lineages exhibit greater longevity than others. Nonetheless, so far only a small number of gene variants have been robustly demonstrated to influence human longevity. This poor yield is not for lack of searching, but because it seems likely that individual genetic contributions to longevity are both very small and very specific to environmental circumstances. Every study finds novel variants that correlate within that study population, but no other study is able to replicate that finding. This ultimately leads to a growing consensus that familial longevity is more a matter of transmission of culture and environment than transmission of genes: exercise, diet, exposure to persistent pathogens, and so forth.

The study of such exceptionally old individuals (longevity) is important as they likely harbor gene-environment interactions which beneficially regulate molecular pathways involved in longevity, resistance to disease, resilience to negative side-effects of treatment and therefore healthy aging. It has been estimated that age at death (lifespan) attributes for ~25% to genetic variation and this number rises for long-lived individuals as shown by its strong familial clustering. Nevertheless, two decades of genetic research to understand the mechanisms of longevity and healthy aging had limited robust results. Amongst a number of potential determinants, only the APOE and FOXO3A genes have been consistently identified.

One of the main reasons for the difficulty of identifying genes promoting longevity and healthy aging is the lack of a consistent definition for heritable longevity, which resulted in a mix of sporadically long-lived cases with those descending from a long-lived family and a large variation of longevity definitions used in longevity research. The presence of sporadically long-lived cases is illustrated by the increase of centenarians in the United States between 1994 and 2012 from 1 in 10,000 to 2 in 10,000. Secondly, Genome Wide Association (GWA) analysis, the leading method in complex disease mapping, relies on comparing living long-lived individuals (cases) with averagely living individuals (controls). These averagely lived individuals can in fact become long-lived over time, thus potentially confusing cases and controls.

In addition, recent research revealed the importance of rare and structural variants in addition to the common single nucleotide polymorphisms (SNPs) studied in GWAS. Thirdly, socio-behavioral and environmental factors, such as lifestyle, socioeconomic status, social network, and the living environment shaped the aging process of long-lived persons in interaction with their genes. However, these factors are rarely included in genetic longevity studies and surprisingly little is known about how they cluster in long-lived families.

The issue of unintentionally including sporadically long-lived cases has recently been addressed in two studies, using multiple large scale family tree databases; the Utah Population Database (UPDB), the LINKing System for historical family reconstruction (LINKS), and the Historical Sample of the Netherlands Long Lives (HSN-LL) which contain thousands of families. The studies showed that longevity is only transmitted across generations if at least 30% of the ancestors of a person belonged to the top 10% survivors of their birth cohort and the persons themselves also belong to the 10% longest lived. Importantly, 27% of the HSN-LL research persons showed a survival pattern similar to the general population even though they had at least one long-lived parent. Based on these results, the Longevity Relatives Count (LRC) score was developed as an instrument to identify genetically enriched long-lived persons for case inclusion in genetic studies and thus avoid the inclusion of sporadically long-lived persons.

Link: https://doi.org/10.18632/aging.104218

The dominant view of Alzheimer's disease remains the amyloid cascade hypothesis: amyloid-β accumulates over time in the brain, which generates immune dysfunction, inflammation, and finally tau aggregation that kills large numbers of brain cells. After a great deal of work and expense, the research and development community has produced a number of immunotherapies capable of reducing levels of amyloid-β in the brain. Unfortunately, these treatments don't appear to do all that much to improve the symptoms of Alzheimer's disease in patients. There is certainly no clear and evident gain in function across the board, and even where clinical trial data is sliced finely to try to uncover a subpopulation in which benefits do occur, these benefits are not large.

One hypothesis on this lack of efficacy is that only early intervention will work, given that Alzheimer's develops over years of growing levels of amyloid-β, while in the later stages it is the case that chronic inflammation and tau aggregation become the driving mechanisms causing neurological dysfunction and cell death. An alternative hypothesis is that amyloid-β aggregation is a side-effect, of little importance to outcomes, while some combination of persistent infection, cellular senescence, and chronic inflammation are the primary mechanisms of Alzheimer's disease.

Given therapies that can reduce amyloid-β levels in the brain, and given a huge sunk cost to date in targeting amyloid-β, it is certainly the case that the early intervention hypothesis is going to be tested aggressively. Big Pharma entities are in search of some way to recoup the costs incurred to date, by demonstrating a beneficial use for these treatments. Today's research materials are one illustrative example selected from a broad range of efforts to find viable points of intervention in the very early development of Alzheimer's disease, with an eye to preventing the condition from progressing.

The Long Road to Dementia

Alzheimer's disease develops over decades. It begins with a fatal chain reaction in which masses of misfolded beta-amyloid proteins are produced that in the end literally flood the brain. Researchers have found that this chain reaction starts much earlier in mice than commonly assumed. This means that in addition to the well-known early phase of the disease with protein deposits but without symptoms of dementia, there is an even earlier phase in which the chain reaction is triggered by invisible tiny seeds of aggregation.

searched among the already known antibodies directed against misfolded beta-amyloid proteins for antibodies that can recognize and possibly also eliminate these early seeds of aggregation that currently escape biochemical detection. Of the six antibodies investigated, only aducanumab had an effect: Transgenic mice that were treated for only 5 days before the first protein deposits manifested, later on in life showed only half of the usual amount of deposits in their brains. "This acute antibody treatment obviously removes seeds of aggregation, and the generation of new seeds takes quite some time, so that much less deposits are formed in the weeks and months after the treatment. Indeed, the mice had only half the brain damage six months after this acute treatment."

Acute targeting of pre-amyloid seeds in transgenic mice reduces Alzheimer-like pathology later in life

Amyloid-β (Aβ) deposits are a relatively late consequence of Aβ aggregation in Alzheimer's disease. When pathogenic Aβ seeds begin to form, propagate and spread is not known, nor are they biochemically defined. We tested various antibodies for their ability to neutralize Aβ seeds before Aβ deposition becomes detectable in Aβ precursor protein-transgenic mice. We also characterized the different antibody recognition profiles using immunoprecipitation of size-fractionated, native, mouse and human brain-derived Aβ assemblies. At least one antibody, aducanumab, after acute administration at the pre-amyloid stage, led to a significant reduction of Aβ deposition and downstream pathologies 6 months later. This demonstrates that therapeutically targetable pathogenic Aβ seeds already exist during the lag phase of protein aggregation in the brain. Thus, the preclinical phase of Alzheimer's disease - currently defined as Aβ deposition without clinical symptoms - may be a relatively late manifestation of a much earlier pathogenic seed formation and propagation that currently escapes detection in vivo.

Alex Zhavoronkov founded Insilico Medicine, an early company in the young longevity industry, and the first of many to focus on machine learning as a way to improve research infrastructure in drug discovery. Here he offers a selection of opinions on the longevity industry, the approaches he thinks are most interesting. It is worth bearing in mind that his bias is very much towards the use of machine learning and small molecule therapeutics, which is far from a full list of everything that is taking place.

Can you give our listeners a quick overview of the longevity and aging field.

It will be difficult to make a short intro into the longevity industry because it is broad and encompasses many fields that also relate to general biotechnology, pharmaceutical, and healthcare. I would define longevity medicine as a field of AI powered preventative medicine focused on biomarkers of aging. Recently, the longevity industry has advanced quite dramatically. Just in the last ten years, we have seen convergences that integrate soft sciences like information technology with biotechnology. This union resulted in the discovery and rapid adoption of a technology called aging clocks or biomarkers of aging.

Aging clocks were originally developed on methylation data, so epigenetic data by Steve Horvath and the Hannum group from 2011-2013. Our group picked up the trend and converged it with artificial intelligence and developed a range of deep biomarkers of aging or deep aging clocks. We have a variety of aging clocks built on blood tests, transcriptomic data, proteomic data, methylation data and aging data. Pretty much any data that changes in time. This allows us to tangibly measure aging. I believe that this introduction will be the next-generation of the longevity industry.

How about the therapeutic side? What are some drug candidates targeting aging?

I like to break therapeutics down into 5 areas. 1) Rapalogs, derivatives or analogues of rapamycin. 2) Senolytics, drugs that target senescent cells and allow for cells to be replenished, to be recycled. 3) NAD boosters. Multiple groups worldwide discovered that elevating the level of NAD+ molecule at the cellular level results in increases in health and lifespan in model organisms. 4) Metformin, an old diabetic and pre-diabetic drug and now people of all ages are also taking it for longevity. There is a clinical trial on the way called TAME that targets aging. 5) Alpha-ketogluterate (or AKG). AKG is off patent and thus difficult to get intellectual property protection, but it looks like it holds a lot of promise in aging and age-related diseases as well.

What are your expectations for the aging field in the next decade?

We are starting to see companies and even clinical centres combining diagnostics and therapeutics. Unfortunately, we do not see this industry being perceived as credible by the insurance industry and by large pharmaceutic industries, yet at least. We're getting there but we still have a long way to go. I think that in general, the longevity industry is pretty early in its development, so we don't see the hype in longevity yet. We do see the venture capital industry getting into the field. They are funding all kinds of projects, credible and uncredible, and it is great. This investment reminds me of the social networking era, or the era of computing where people were betting on all kinds of projects during the dotcom boom. I think that we are going to see a major boom in aging within the next decade or two. So, if you are a young pharmaceutical executive or if you are a medical student, I would take this industry as a priority for career development.

Link: https://lifescite.com/aging-expert-dr-alex-zhavoronkov-discusses-future-of-the-longevity-space/

Given the newfound consensus in the research community regarding the importance of senescent cells to degenerative aging, it isn't surprising to see a great deal more fundamental research into the biochemistry of cellular senescence now taking place than was previously the case. In many cases it isn't all that clear as to whether an incrementally greater understanding of mechanism A or mechanism B will at any point be helpful to the development of senolytic therapies to selectively destroy senescent cells, but that is the way of fundamental research. It is hard to say in advance what will turn out to be a big deal at the end of the day.

Proteostasis collapse, the diminished ability to maintain protein homeostasis, has been established as a hallmark of nematode aging. However, whether proteostasis collapse occurs in humans has remained unclear. Here, we demonstrate that proteostasis decline is intrinsic to human senescence. Using transcriptome-wide characterization of gene expression, splicing, and translation, we found a significant deterioration in the transcriptional activation of the heat shock response in stressed senescent cells. Furthermore, phosphorylated HSF1 nuclear localization and distribution were impaired in senescence.

Interestingly, alternative splicing regulation was also dampened. Surprisingly, we found a decoupling between different unfolded protein response (UPR) branches in stressed senescent cells. While young cells initiated UPR-related translational and transcriptional regulatory responses, senescent cells showed enhanced translational regulation and endoplasmic reticulum (ER) stress sensing; however, they were unable to trigger UPR-related transcriptional responses. This was accompanied by diminished ATF6 nuclear localization in stressed senescent cells. Finally, we found that proteasome function was impaired following heat stress in senescent cells, and did not recover upon return to normal temperature.

Together, our data unraveled a deterioration in the ability to mount dynamic stress transcriptional programs upon human senescence with broad implications on proteostasis control and connected proteostasis decline to human aging.

Link: https://doi.org/10.1073/pnas.2018138117

Researchers here note a study population in which glucosamine use correlates with a reduction in mortality risk that is of a similar size to that associated with exercise. One always has the suspicion that, even after controlling for such things, the use of less common supplements is just a marker for the small number of people who really care about their health, and who are putting in more effort across the board to maintain themselves. To become convinced that this is not the case, many studies producing similar results would have to exist, with many more participants taking glucosamine.

Consider the level of evidence for exercise to be similarly beneficial: dozens of studies, and hundreds of thousands of participants. Currently there are only a few such studies for glucosamine, and the one here is much less convincing than the other example published earlier this year, in which there were many more participants taking glucoseamine.

If we are to speculate on why glucosamine might have any sizable beneficial effect on health and mortality, then the first mechanism to consider is some form of reduction in the chronic inflammation that accompanies aging. Continual, unresolved inflammation is very disruptive to tissue function, and drives the onset and progression of all of the common age-related conditions. Glucosamine is used in connection with arthritis and other inflammatory conditions, but the evidence is very mixed for it to have any meaningful benefit there. This is another reason to be skeptical. If there were a sizable, reliable reduction in inflammation accompanying the supplementation of glucosamine, then it would show up in that data. And it doesn't.

https://wvutoday.wvu.edu/stories/2020/12/01/glucosamine-may-reduce-overall-death-rates-as-effectively-as-regular-exercise-says-wvu-study

Glucosamine supplements may reduce overall mortality about as well as regular exercise does, according to a new epidemiological study. Researchers assessed data from 16,686 adults who completed the National Health and Nutrition Examination Survey from 1999 to 2010. All of the participants were at least 40 years old. Researchers merged this data with 2015 mortality figures. After controlling for various factors - such as participants' age, sex, smoking status and activity level - the researchers found that taking glucosamine/chondroitin every day for a year or longer was associated with a 39 percent reduction in all-cause mortality. It was also linked to a 65 percent reduction in cardiovascular-related deaths. That's a category that includes deaths from stroke, coronary artery disease, and heart disease, the United States' biggest killer.

Glucosamine/Chondroitin and Mortality in a US NHANES Cohort

Limited previous studies in the United Kingdom or a single US state have demonstrated an association between intake of glucosamine/chondroitin and mortality. This study sought to investigate the association between regular consumption of glucosamine/chondroitin and overall and cardiovascular (CVD) mortality in a national sample of US adults. Combined data from 16,686 participants in National Health and Nutrition Examination Survey 1999 to 2010, merged with the 2015 Public-use Linked Mortality File. Cox proportional hazards models were conducted for both CVD and all-cause mortality.

In the study sample, there were 658 (3.94%) participants who had been taking glucosamine/chondroitin for a year or longer. During followup (median, 107 months), there were 3366 total deaths (20.17%); 674 (20.02%) were due to CVD. Respondents taking glucosamine/chondroitin were less likely to have CVD mortality (hazard ratio [HR] = 0.51). After controlling for age, use was associated with a 39% reduction in all-cause (HR = 0.61) and 65% reduction (HR = 0.35) in CVD mortality. Multivariable-adjusted HR showed that the association was maintained after adjustment for age, sex, race, education, smoking status, and physical activity (all-cause mortality, HR = 0.73; CVD mortality, HR = 0.42).

Chronic inflammation grows with age throughout the body, characterized by increased levels of numerous inflammatory signal molecules, among which is IL-6. One contributing factor to the chronic inflammation of aging is the accumulation of lingering senescent cells, which rouse the immune system via secreted molecules that include, prominently, IL-6. Researchers here home in on one narrow consequence of this changed environment, finding that IL-6 signaling in cerebral vasculature impairs mitochondrial function and the maintenance process of mitophagy responsible for clearing out damaged mitochondria. Loss of mitochondrial function is, in general, a feature of aging, and implicated in many age-related conditions. It is interesting to see an example of a very direct connection between the presence of senescent cells, now well established as a cause of aging, and age-related mitochondrial dysfunction.

The blood-brain barrier (BBB) is critical for cerebrovascular health. Although aging impairs the integrity of the BBB, the mechanisms behind this phenomenon are not clear. As mitochondrial components activate inflammation as mitochondria become dysfunctional, we examined how aging impacts cerebrovascular mitochondrial function, mitophagy, and inflammatory signaling; and whether any alterations correlate with BBB function.

We isolated cerebral vessels from young (2-3 months of age) and aged (18-19 months of age) mice and found that aging led to increases in the cyclin-dependent kinase inhibitor 1 senescence marker with impaired mitochondrial function, which correlated with aged mice exhibiting increased BBB leak compared with young mice. Cerebral vessels also exhibited increased expression of mitophagy proteins Parkin and Nix with aging. Using mitophagy reporter (mtKeima) mice, we found that the capacity to increase mitophagy from baseline within the cerebral vessels on rotenone treatment was reduced with aging. Aging within the cerebral vessels also led to the upregulation of the stimulator of interferon genes and increased interleukin 6 (IL-6), a cytokine that alters mitochondrial function.

Importantly, exogenous IL-6 treatment of young cerebral vessels upregulated mitophagy and Parkin and impaired mitochondrial function; whereas inhibiting IL-6 in aged cerebral vessels reduced Parkin expression and increased mitochondrial function. Furthermore, treating cerebral vessels of young mice with mitochondrial N-formyl peptides upregulated IL-6, increased Parkin, and reduced Claudin-5, a tight junction protein integral to BBB integrity. In conclusion, aging alters the cerebral vasculature to impair mitochondrial function and mitophagy and increase IL-6 levels. These alterations may impair BBB integrity and potentially reduce cerebrovascular health with aging.

Link: https://doi.org/10.1161/JAHA.120.017820

Decades ago, the pineal gland was the focus of a great deal of ignorant hype regarding research into aging and the prospects for treating aging. The paper here is an interesting overview of what is known about possible connections between the thymus and the pineal gland, both of which atrophy with age, and both of which have sweeping effects on the immune system. It is perhaps of greatest interest as a catalog of things yet to be discovered - roads leading into the dark forest from the starting point of lists of molecules secreted by thymus and pineal gland, added to what is known of what goes on inside these two organs, and what those molecules are known to do elsewhere in the body. There is the suspicion that some of these roads may cross somewhere in the great expanse of metabolism that is yet to be well mapped, but a much work has yet to be accomplished in order to find out whether or not this is the case.

Mutual influences and bidirectional networks among the nervous system, endocrine system, and immune systems are mediated by hormones, cytokines/chemokines and their binding sites, contributing, in turn, to body homeostasis. Many interactions are mediated by the highly regulated release of several hormones and peptides into the vessels, which have direct effects on the immune system. In particular, many studies have reported interactions between the pineal gland (PG), thymus gland (TG), and other parts of the immune system owing to the widespread expression of receptors that detect the respective humoral signals.

The impairment of TG and PG functions, mainly related to neuroendocrine and immune systems, is associated with ageing, and unfortunately, the physiological deterioration is a precursor to pathologies. Moreover, the alterations of the TG-PG axis during ageing are already indicative of a close relationship between these two glands. In fact, the PG, certainly via melatonin, but perhaps also via additional factors such as thyroid-stimulating hormone (TSH) and other peptides, influences humoral and cellular immunity, immune cell proliferation and immune mediator production. The TG is central to many immunological functions, which are mediated by peptides. Moreover, these glands play an important role as a functional unit because they constitute a bidirectional system in which PG acts on TG and vice versa. Thus, they have a mutual complementarity in the maintenance of a normal immune and endocrine status, which becomes especially evident in ageing.

Researchers have reported an influence of thymic peptides on PG and pineal peptides on TG. Importantly, removal of the PG induces decreases in thymus weight, the number of thymic cells, and TG secretory functions. The blockage of PG, induced by pharmacological treatments, also resulted in a decrease of the thymic hormone, thymulin, in the blood. Moreover, thymectomy caused changes in biorhythms for several immune indicators of glucocorticoid synthesis by the adrenal cortex. The bidirectional communication between TG and PG is also due to the release of some cytokines that are secreted by these glands. One of them is tumour necrosis factor-α (TNF-α) which is produced, apart from other immune cells, in the thymic medulla.

According to our current knowledge, the mutual functional relationship of the TG-PG axis during the phases of life and, particularly, in ageing would benefit from and be worth of increasing research efforts. To date, the literature is still somewhat scanty and does not easily reveal the entire complexity of their relationships, in part because many findings are relatively old and often published in languages rarely used in science. The histological and functional losses of both the PG and TG are salient features of ageing. The message of this article is that they seem to be interrelated.

Link: https://doi.org/10.3390/ijms21228806

Senescent cell accumulation is an important cause of degenerative aging. Senescent cells cease replication and begin to secrete an inflammatory mix of signals that disrupt tissue structure and function. These cells are created constantly, largely as a result of somatic cells hitting the Hayflick limit on cellular replication, but also as a result of injury, molecular damage, inflammation, and the like. Near all senescent cells are rapidly destroyed, either via programmed cell death mechanisms, or via the immune system. This clearance falters with age, however, slowing down, becoming less efficient, and allowing senescent cells to accumulate, disrupt tissue function, and provoke chronic inflammation.

The targeted destruction of senescent cells has been shown - in animal models - to reverse the progression of many age-related conditions and extend healthy life span. It is easy to demonstrate such results, and many research groups have used many different methods to destroy senescent cells. To the extent that these errant cells are removed, benefits follow. As these demonstrations have accumulated over the years, researchers have broadened their investigations of the biochemistry of senescent cells.

One class of outcome of this work is represented by today's open access paper. Researchers have identified a gene that affects the burden of cellular senescence, and find that adjusting expression levels down or up also adjusts lifespan as well, due to there being greater or lesser numbers of senescent cells present in older individuals. This is a good secondary demonstration of the importance of senescent cells to aging and longevity, but not really a good basis for building interventions. Senolytic therapies that destroy senescent cells are just too good a class of treatment to see much competition from this front. In the case of senolytics: large beneficial effects are achieved very quickly; treatment is only needed intermittently, such as once every few months at most; the first generation drugs cost very little. That compares very favorably with a senescence suppression treatment that would have to be taken continuously across a lifetime, with only small benefits in the short term, particularly given that senescent cells are actually beneficial for wound healing and cancer suppression when present in small numbers, and briefly.

MYSM1 Suppresses Cellular Senescence and the Aging Process to Prolong Lifespan

Aging is characterized by a functional decline across multiple organ systems and is a risk factor for many human diseases. Substantial evidence has demonstrated that senescence is a key hallmark of the aging process and plays a critical roles in controlling aging and aging-associated diseases. Senescence is a cellular response that acts to restrict the proliferation of aged and damaged cells, and is also a state of growth arrest and pro-inflammatory cytokine release in response to stresses. One hallmark of cellular senescence is the secretion of excessive proinflammatory cytokines, chemokines, extracellular matrix proteins, growth factors, and proteases termed the senescence-associated secretory phenotype (SASP). Senescence constitutes a stress response triggered by insults associated with aging including genomic instability and telomere attrition.

DNA damage is a causal factor in the aging process that drives cells into senescence or apoptosis as results of the DNA damage response (DDR) controlled by DNA repair processes. DNA double-strand break (DSB) repair is known to decline age, leading to the accumulation of genomic rearrangements. Mutations in DNA DSB repair genes reduce lifespan, indicating that DNA repair pathways play a critical roles in the aging process.

The Myb-like, SWIRM, and MPN domains-containing protein 1 (MYSM1) is a histone 2A (H2A) deubiquitinase that specifically deubiquitinates H2A. It is a key functional regulator of hematopoietic stem cells, lymphocytes, and blood cells, and serves as an important regulator of tissue differentiation. MYSM1 is also linked to heritable bone marrow failure syndromes, plays a role in regulating skin development in mice, and impedes antiviral signaling. Loss of Mysm1 has been shown to promote activation of the p53 stress response and induced abnormal cell development and tissue differentiation. More recently, a study revealed that Mysm1 levels increase in response to etoposide-induced DNA damage and that mice lacking Mysm1 show a shorter lifespan. These important roles of MYSM1 implicate that it may be involved in the regulation of cellular senescence and the aging process.

The present study showed that MYSM1 is a key suppressor of senescence and aging. Functionally, MYSM1 functionally represses DDR-associated SASP and the aging process. Mechanistically, MYSM1 represses the aging process by promoting homologous recombination (HR) mediated DNA repair. Mysm1 deficiency promotes aging and aging-related pathologies and reduces lifespan in mice. AAV9-Mysm1 was shown to attenuate the aging process to prolong the lifespan of mice. Our data suggest that Mysm1 is a potential agent for the prevention of aging and aging-related diseases.

Here, researchers explore the mechanisms governing changes in cell behavior during reprogramming. Many of the aspects of aging found in cells taken from old tissues can be reversed via the process of reprogramming these cells into induced pluripotent stem cells. Mitochondrial function is restored to youthful levels, for example, as well as much of the epigenetic signature that determines protein production and cell function. There are issues that are not addressed, such as mutations, but this effect of reprogramming is sufficiently interesting to have given rise to several research programs and the company Turn.bio, seeking to build a therapy on the basis of partially reprogramming cells to the point at which rejuvenation occurs.

Scientists know that cellular reprogramming can reverse the process of cellular aging that leads to a decline in the activities and functions of mesenchymal stem/stromal cells (MSCs), but the underlying mechanisms haven't been clear. Newly reported research has identified a key role for a protein known as GATA6, in this reversal process. Researchers used cellular reprogramming to establish a genetically identical young and old cell model. They began by isolating MSCs from human synovial fluid (SF-MSCs), and reprogrammed them into induced pluripotent stem cells (iPSCs) using the Yamanaka transcription factors. Then they differentiated these iPSCs back to MSCs, in effect rejuvenating the MSCs.

The scientists next conducted an analysis of the cells to determine if there were any changes in global gene expression resulting from the reprogramming. They found that the expression of GATA6, a protein that plays an important role in gut, lung, and heart development, was repressed in the reprogrammed cells compared with the control cells. This repression led to increased activity of a protein called sonic hedgehog (SHH) that is essential to embryonic development, as well as the expression level of another protein, FOXP1, which is necessary for proper development of the brain, heart, and lung.

To determine which of the Yamanaka transcription factors were involved in repressing GATA6 in the iPSCs, the team analyzed GATA6 expression in response to the knockdown of each factor. The results indicated that only OCT4 and KLF4 were able to regulate GATA6 activity, a finding that is consistent with that of several previous studies.

Link: https://www.genengnews.com/news/gene-responsible-for-cellular-aging-in-human-cells-identified/

Demonstrations in which researchers adjust cell state or signaling to reverse cognitive decline in old mice suggest that a meaningfully large fraction of this age-related cognitive decline is actively maintained via dysfunctions in cell signaling and cell activity. Senescent cells and their inflammatory signaling are a likely culprit, though it is challenging to join the dots between signaling and specific mechanisms inside cells in the highly complex environment of cellular biochemistry. The important point is that much of the decline in cognitive function could be quickly reversed if specific signals and mechanisms can be addressed. The work here is hopeful evidence on that front, though we should not forget that there remain the late stages of neurodegenerative conditions in which too much damage has been done, too many cells have died in the brain, for there to be a solution of this nature.

Just a few doses of an experimental drug can reverse age-related declines in memory and mental flexibility in mice, according to a new study. The drug, called integrated stress response inhibitor (ISRIB), targeting eIF2α phosphorylation, has already been shown in laboratory studies to restore memory function months after traumatic brain injury (TBI), reverse cognitive impairments in Down Syndrome, prevent noise-related hearing loss, fight certain types of prostate cancer and even enhance cognition in healthy animals. In the new study, researchers showed rapid restoration of youthful cognitive abilities in aged mice, accompanied by a rejuvenation of brain and immune cells that could help explain improvements in brain function.

"ISRIB's extremely rapid effects show for the first time that a significant component of age-related cognitive losses may be caused by a kind of reversible physiological "blockage" rather than more permanent degradation. The data suggest that the aged brain has not permanently lost essential cognitive capacities, as was commonly assumed, but rather that these cognitive resources are still there but have been somehow blocked, trapped by a vicious cycle of cellular stress. Our work with ISRIB demonstrates a way to break that cycle and restore cognitive abilities that had become walled off over time."

Link: https://www.eurekalert.org/pub_releases/2020-12/uoc--dra120120.php

Calcification of blood vessel walls progresses with age, an issue that sees cells behave as through they are in bone tissue, a maladaptive reaction to the altered signaling environment and damage of aged tissue. The resulting deposition of calcium makes normally flexible cardiovascular tissue stiff and dysfunctional, ultimately contributing to disease and death. Evidence has accumulated in recent years for the accumulation of senescent cells to be an important contributing factor to calcification. Senescent cells grow in number with age and secrete the senescence-associated secretory phenotype (SASP), signals that rouse the immune system to inflammation and cause harmful alterations in the behavior of other cells.

There is an established body of work regarding factors that affect the progression of calcification, such as chronic use of the anticoagulant warfarin (unfavorable) and vitamin K intake (favorable). Given the better and broader understanding lately emerged in the research community of the relevance of cellular senescence to aging, a great deal of retrofitting of old theories and data is presently taking place. Today's open access paper is an example of this sort of work, in which links are established between the SASP and long-established risk factors for calcification revolving around the role of vitamin K and treatments like warfarin that reduce vitamin K levels.

Warfarin Accelerates Aortic Calcification by Upregulating Senescence-Associated Secretory Phenotype Maker Expression

Aortic calcification (AC) is a pathological condition with increasing prevalence of morbidity and mortality. AC is a process of osteoblast-like cell accumulation in the muscular layer of arteries. Enhanced stiffness of the arteries in AC might lead to severe vascular complications in the brain, heart, and kidneys. AC is a strong, independent predictor of cardiovascular disease (CVD) and cardiac adverse events. The present study demonstrated that the association of warfarin use with AC differs in different age groups of patients. Specifically, warfarin adversely affects younger (<65 years) patients more than older (≥65 years) patients, and this is possibly due to the fact that warfarin-associated senescence was more sensitive in younger patients. In vitro study also revealed that young VSMC are more sensitive to warfarin-induced low-grade calcification.

It has been observed that there is a systemic increase level of secreted proteins with aging, which contain several proinflammatory cytokines, chemokines, tissue-damaging proteases, and growth factors. These secreted factors affect the microenvironment of tissue, in which they could propagate the stress response and regulate neighboring cells. These phenotypes are termed the senescence-associated secretory phenotype (SASP). The SASP is a critical intrinsic characteristic of cellular senescence resulting in a chronic low-grade state of inflammation that has been implicated in the development of several chronic diseases of aging including AC. Among SASP, cytokines and growth factors are important in the differentiation of senescent VSMC into calcified cells.

we conducted a case-cohort study within the Multi-Ethnic Study of Atherosclerosis (MESA); 6,655 participants were included. From MESA data, we found that AC was related to both age and vitamin K; furthermore, the score of AC increased with SASP marker including interlukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α) rising. Next, a total of 79 warfarin users in our center developed significantly more calcified coronary plaques as compared to non-warfarin users. We investigated the role of warfarin in phosphate-induced AC in different ages by in vitro experimental study. Furthermore, dose-time-response of warfarin was positively correlated with AC score distribution and plasma levels of the SASP maker IL-6 among patients younger than 65 years, but not among patients older than 65 years. In addition, in vitro research suggested that warfarin treatment tended to deteriorate calcification in young VSMC at the early stage of calcification. Our results suggested that aging and warfarin-treatment were independently related to increased AC. Younger patients were more sensitive to warfarin-related AC than older patients, which was possibly due to accumulated warfarin-induced cellular senescence.

In the MESA, we discovered that the accumulated intake of vitamin K was negatively related to AC, which demonstrated that warfarin may aggravate AC by downregulating the level of vitamin K in plasma. In addition, IL-6 and TNF-α levels were positively correlated with AC. When we divided individuals depending on vitamin K intake and analyzed the relationship among vitamin K, AC, and SASP, results showed that Agatston score (a measure of AC) and SASP level decreased with the increase of vitamin K intake.

The first wave of longevity industry companies to reach clinical trials and large funding rounds are those that focus on the well established methodology of small molecule development. Many are also platform companies that have developed approaches to speed up the expensive and time-consuming tasks of screening and designing small molecules. With the exception of the small molecule senolytics companies, these treatments presently tend to epitomize what the SENS Research Foundation folk would call "messing with metabolism," a poor alternative to actually targeting and fixing underlying causes of aging. This messing with metabolism usually means finding a molecule that can provoke cells into undertaking some of the same repair and maintenance mechanisms that occur in response to exercise, calorie restriction, heat, cold, toxins, and other stresses. The outcomes in mice are usually no better than the benefits resulting from exercise or calorie restriction.

We live in a world conditioned to expect very little from medicine to treat diseases of aging - no great surprise given that, historically, no-one tried to target the causes of aging. There is only so much you can do to keep a damaged machine running if you persist in not repairing the damage. We have a regulatory system that is geared up to the task of picking out marginally successful therapies from those that do nothing. In this world, turning up with a therapy that is 25% or 50% as good as the results of structured exercise in old people, small improvements across the board for all aspects of aging, is a real step forward from the status quo. But it is still a very poor strategy in comparison to that of the SENS program. We should be repairing the causes of aging, not tinkering with the broken metabolism of older people to try to make it a little more resilient to the burden of damage. Repair is the only way that we humans are going to gain additional decades and more of healthy life.

BioAge Labs, Inc., a biotechnology company developing medicines to treat aging and aging-related diseases, today announced that it has raised $90 million in an oversubscribed Series C financing. The raise was co-led by Andreessen Horowitz and serial entrepreneur, Elad Gil, and included new investors Kaiser Foundation Hospitals, AARP Foundation (through the RockCreek Impact Fund) and Phi-X Capital, the fund of genomics entrepreneur Mostafa Ronaghi, among others. Current investors including Caffeinated Capital, Redpoint Ventures, PEAR Ventures, AME Cloud Ventures, Felicis Ventures, and others also participated.

Proceeds from the financing will be used to build and develop a diversified portfolio of therapies that increase healthspan and lifespan, augment BioAge's artificial intelligence (AI)-driven approach to map the molecular pathways that impact human longevity, and further expand capabilities to test drug candidates in predictive models of human diseases of aging. "These additional funds will support advancement of our pipeline of medicines that target these pathways to reverse or eradicate diseases and extend healthspan. We look forward to advancing our first platform-derived therapies, BGE-117 and BGE-175 into clinical trials in the first half of 2021."

"Drugs that target aging have potential to treat several morbid diseases and improve the lives of older adults. BioAge has built a proprietary engine to analyze molecular signatures in aging populations, and to advance data-driven hypotheses to identify existing clinical-stage drugs that are ready for Phase 2 efficacy trials in age-related diseases. I'm excited to work with them as they scale their platform and develop multiple therapies to improve the health of older individuals."

Link: https://apnews.com/press-release/globe-newswire/science-business-technology-small-business-aging-6e21dde774ba40d263674c4cc2d1372b

Thymocytes created in the bone marrow travel to the thymus, and there mature into T cells of the adaptive immune system. The thymus, unfortunately, atrophies with age, a process known as thymic involution. By age 50 it is largely fat tissue, and the supply of new T cells diminishes to a trickle. In old age, the total number of T cells remains much the same as in youth, but absent regular reinforcements, all too many of these vital cells are worn, damaged, exhausted, senescent, and often pathologically misconfigured. Too few competent T cells remain to carry out the vital tasks of killing pathogens and errant, potentially cancerous cells. This is a major cause of immune system aging and the frailty and vulnerability that follows.

The thymus, which exists in nearly all vertebrates, is a primary lymphoid organ essential for the maturation of bone marrow (BM)-derived T lymphoid precursors. The maturation and selection processes of T cells in the thymus generate a pool of circulating naïve CD4 and CD8 T cells. Such a pool allows the generation of immunity, on the one hand, and the ability to maintain tolerance to self-antigens, on the other hand. A proper thymic output may thus be considered a crucial first stage that generates a highly diverse T-cell repertoire, which is required to maintain plasticity, protection, and repair, while minimizing the risk of pathogenic autoimmunity. Since CD4 T cells evolved to play a key role in orchestrating these functions, they may be considered keystone in the ecosystem of properly regulated immunity.

Regardless of the seemingly crucial role of the thymus in preserving homeostasis, its involution begins in childhood and peaks up around puberty, resulting in an almost completely non-functional organ in aging. Thymus involution gradually reduces the output of naïve T cells with age. Dynamic changes in the thymic T lymphocytes include a reduced number of undifferentiated T cells and an increase in terminally differentiated cells (e.g., T cells with memory phenotypes). A hint to the effect of thymus involution can be found in the context of early life (before puberty) thymectomy. In young humans, thymectomy results in T-cell changes that are similar to those related to immunosenescence. Specifically, it was shown that the number of both CD4 and CD8 naïve T cells decreases while the number of memory and exhausted phenotypes increases.

These studies may imply a causal link between thymus involution and accumulating defects in the immune system with aging. The overall process that leads to immune failure in old age is apparently the sum of parallel processes, namely, thymus involution, intrinsic T-cell defects, chronic inflammation, and cell senescence. Targeting these components may shed light on the impact of each process and its therapeutic potential for the restoration of immunity and its repair in elderly.

Link: https://doi.org/10.1016/j.arr.2020.101231

The practice of calorie restriction is well documented to slow the progression of aging in mammals. In humans, there is comprehensive evidence for it to improve measures of health and reduce the risk of age-related disease. The mechanisms by which calorie restriction produces benefits are essentially the same across species, an upregulation of various stress response mechanisms that maintain and repair cell function. The short-term health benefits, the specific outcomes resulting from this favorable alteration in the operation of cellular metabolism, are also very similar. However, the extension of life span produced by calorie restriction diminishes as species life span increases. Calorie restriction can extend life in mice by up to 40%, but is thought to only add a few years to human life span.

Nonetheless, improved health is improved health, and calorie restriction does more for long-term health in humans than near any other available intervention. Perhaps only senolytic drugs that clear lingering senescent cells from old tissues will improve upon the benefits for older people, but a head to head comparison has yet to take place.

Today's open access paper offers a narrow focus on the interaction between calorie restriction and one specific age-related condition. It is a review of what is known of the mechanisms by which calorie restriction slows the onset of sarcopenia, the widespread loss of muscle mass and strength that takes place with advancing age. There are many contributing causes of sarcopenia, all of which interact with one another, though the most important are likely (a) a decline in muscle stem cell activity, leading to a reduced supply of new muscle cells to maintain this tissue, (b) damage and loss of function in neuromuscular junctions that link the nervous system to muscles.

Caloric restriction: implications for sarcopenia and potential mechanisms

Epidemiological investigations have indicated that the muscle mass of the human body decreases by approximately 1.5% yearly after the age of 50 and by 2.5-3.0% yearly after the age of 60. The incidence rate of sarcopenia among individuals over 80 years old is as high as 50%. Studies have shown that a 10% decrease in muscle mass leads to a decrease in immune function and an increase in the risk of infection. A 20% reduction in muscle mass results in muscle weakness, a decreased ability to participate in activities of daily living, and an increased risk of falling. A 30% reduction in muscle mass results in disability, loss of independent living ability, and failure of wound and pressure ulcer healing. A 40% reduction in muscle mass results in a markedly increased risk of death from pneumonia, respiratory dysfunction, etc.

The main manifestations of sarcopenia in elderly individuals are a decreased cross-sectional area of muscle fibers and reduced muscle strength and function. Clinical studies have shown that the reduction in muscle mass is much greater in the lower limbs than in the upper limbs. Gait speed or the short physical performance battery (SPPB) are commonly used to assess muscle function. Muscle strength tends to decrease with age, as manifested by reduced grip strength and knee joint extension, weakened hip joint bending activity, decreased pace, and increased time to maximal muscle contraction compared with those of young individuals. Additionally, the number and the proliferation and differentiation abilities of muscle stem cells (MuSCs), which play an important role in muscle cell regeneration, are reduced. The number of MuSCs in aged mice is 50% lower than that in young mice.

A recent study found that CR can improve the function of adult stem cells, including the regeneration ability of skeletal MuSCs. To study whether CR can affect the rhythmic activity of stem cells during aging, researchers conducted a 25-week comparative observation of aged mice that consumed a control diet or a diet with 30% fewer calories than the control diet. In this study, except for the reduction in body weight, the aging characteristics related to epidermal and muscle tissue in mice were significantly ameliorated in the CR group compared with the control group. Additional studies have indicated that not stem cells themselves but the stem cell microenvironment is the key factor mediating stem cell activation, proliferation and differentiation.

Mitochondrial dysfunction is an important factor leading to age-related muscular atrophy. Considering the dependence of skeletal muscle on ATP, loss of mitochondrial function, which can lead to a decrease in strength and endurance, is especially obvious in skeletal muscle. CR can preserve the integrity and function of mitochondrial structure via reducing oxidative damage. Previous studies have shown that CR reduces proton leakage and ROS generation in mitochondria in skeletal muscle while enhancing the expression of ROS scavenging-related genes. In addition, CR may alter the fatty acid composition of the mitochondrial membrane, reduce lipid oxidation, and reduce proton leakage.

Accumulating evidence suggests that apoptosis may constitute a fundamental mechanism driving the onset and progression of sarcopenia. There are two main pathways of apoptosis: activation of the apoptotic enzyme caspase through extracellular signaling and activation of caspases through the release of mitochondrial apoptosis activators. These activated caspases can degrade important proteins in cells and induce apoptosis. The gene expression and cleavage of pre-caspase-3 in the gastrocnemius muscle were significantly reduced in CR mice compared with control mice. In addition, CR increased the content of apoptosis inhibitors in the cytoplasm.

Experimental data strongly suggest that mTOR activity increases during aging, beginning in middle age and resulting in progressively altered mitochondria, in turn leading to mitochondrial oxidative stress and thus the induction of catabolic processes, including protein degradation, apoptosis, and necrosis. This elevated catabolic activity results in muscle fiber loss, atrophy, and damage. Recent evidence has shown that CR downregulates mTORC1 signaling in skeletal muscle independent of dietary protein intake. Moreover, a paper published in 2019 indicated that the effects of CR on mTOR signaling in skeletal muscles are age-dependent. CR altered mTOR signaling in the soleus muscles in middle-aged rats but not in young and adult rats.

Autophagy is essential for overall cellular health because in some residual tissues, the lack of an autophagic response gradually results in the accumulation of damage within the cells, eventually leading to cell death and loss of tissue function. In vivo studies have demonstrated that CR can increase autophagic responses in skeletal muscle. Additional studies have shown that CR regulates the transcription factor Forkhead box O3 (FOXO3), which is associated with human longevity, and recent studies have shown that muscle atrophy is associated with the expression of the transcription factor FOXO3 and other downstream target skeletal muscle atrophy-related proteins.

In summary, the protective effects of CR on sarcopenia are manifested as improved protein quality, maintenance of muscle strength, and enhanced muscle function, and these effects may be achieved via mitigation of cellular oxidative stress, promotion of mitochondrial function, alleviation of the inflammatory response, inhibition of apoptosis, activation of autophagy, and other mechanisms.

Cells become senescent in response to damage, signaling of other senescent cells, or on reaching the Hayflick limit to cell replication. Senescent cells cease to replicate, secrete a potent mix of inflammatory signals, and near all self-destruct or are destroyed by the immune system. Unfortunately, some escape this fate, and so senescent cells accumulate with age to cause chronic inflammation, tissue remodeling, and age-related disease. A few years ago, researchers discovered a way to adjust splicing factors to reverse cellular senescence, allowing cells to replicate once again. Here, another approach is outlined, which may or may not work via similar underlying mechanisms. I remain of the mind that this isn't a useful path to therapy, as a significant fraction of senescent cells become senescent for a good reason, in that they are damaged and potentially cancerous. It is better, I think, to focus on selective destruction via senolytic therapies rather than attempts to rehabilitate senescent cells.

Cells respond to a variety of factors, such as oxidative stress, DNA damage, and shortening of the telomeres capping the ends of chromosomes, by entering a stable and persistent exit from the cell cycle. This process, called cellular senescence, is important, as it prevents damaged cells from proliferating and turning into cancer cells. But it is also a natural process that contributes to aging and age-related diseases. Recent research has shown that cellular senescence can be reversed. But the laboratory approaches used thus far also impair tissue regeneration or have the potential to trigger malignant transformations.

Researchers used an innovative strategy to identify molecules that could be targeted for reversing cellular senescence. The team pooled together information from the literature and databases about the molecular processes involved in cellular senescence. To this, they added results from their own research on the molecular processes involved in the proliferation, quiescence (a non-dividing cell that can re-enter the cell cycle), and senescence of skin fibroblasts, a cell type well known for repairing wounds. Using algorithms, they developed a model that simulates the interactions between these molecules. Their analyses allowed them to predict which molecules could be targeted to reverse cell senescence.

They then investigated one of the molecules, an enzyme called PDK1, in incubated senescent skin fibroblasts and three-dimensional skin equivalent tissue models. They found that blocking PDK1 led to the inhibition of two downstream signalling molecules, which in turn restored the cells' ability to enter back into the cell cycle. Notably, the cells retained their capacity to regenerate wounded skin without proliferating in a way that could lead to malignant transformation. The scientists recommend investigations are next carried out in organs and organisms to determine the full effect of PDK1 inhibition. Since the gene that codes for PDK1 is overexpressed in some cancers, the scientists expect that inhibiting it will have both anti-aging and anti-cancer effects.

Link: https://news.kaist.ac.kr/newsen/html/news/?mode=V&mng_no=11111

Aging has a number of distinct root causes, but they do not proceed in isolation. Cell and tissue damage of one sort interacts with cell and tissue damage of other sorts, and so too do all of the downstream consequences of that damage. Aging is a web of connected issues, all making each other worse as they progress. Degenerative aging accelerates in pace over time precisely because of this behavior, in which damage and dysfunction speeds up the accumulation of more damage and dysfunction. The authors of the open access paper here illustrate this principle by taking mitochondrial dysfunction as a starting point and examining how it interacts with other known mechanisms of aging.

The role of mitochondrial dysfunction in aging is well documented. The primary hallmarks of aging are defined as unequivocally deleterious to the cell. This means that proper functioning of these processes is important for the viability of the cell and the dysfunction that occurs with age leads to cellular damage. Mitochondrial dysfunction interacts with each of these primary hallmarks, thus leading to progression of the aging process.

The nine cellular and molecular hallmarks of aging are divided into three groups; (a) the primary hallmarks, (b) antagonistic hallmarks, and (c) integrative hallmarks. The primary hallmarks, which are unequivocally deleterious to the cell, include genomic instability, telomere attrition, epigenetic alterations, and loss of proteostasis. The antagonistic hallmarks, which are beneficial at low levels but at high levels become deleterious, are deregulated nutrient sensing, cellular senescence, and mitochondrial dysfunction. Finally, the integrative hallmarks, affecting tissue homeostasis and function, are stem cell exhaustion and altered intercellular communication. These hallmarks of aging have been presented throughout various research disciplines as nine separate hallmarks, and, while possessing crosstalk, are still considered largely independent. In this review, we provide evidence of the interplay between hallmarks, by highlighting one, mitochondrial dysfunction, and how it interacts with all others.

The hallmarks of aging connect to and influence one another. For instance, cellular senescence can be induced by genomic instability or telomere attrition and epigenetic alternations can lead to genomic instability. It is hence evident that the hallmarks of aging are not discrete entities as how are often presented, but instead operate in a large and tightly connected network. Targeting one factor of this network can result in affecting other hallmarks and thus influence the whole network of aging.

Although this complicates our interpretation of anti-aging interventions and requires a more holistic approach, it also opens opportunities for treatment options that not only target one hallmark but in fact act on the entire, or at least a large section of the network. In relation to the phylogenetic tree of life, while the exact details of the hallmarks of aging may differ, the main commonality that unifies aging across all species is the fact that all their hallmarks interconnect. Taking the entirety of this network into account will benefit the aging research community, and ultimately allow for a greater understanding of the aging processes and the progression of age-related disease.

Link: https://doi.org/10.3389/fcell.2020.594416

Several research groups and companies are working on in vivo applications of cellular reprogramming. Today's research materials cover recent work from David Sinclair's team showing off the use of reprogramming to produce regeneration of damaged nervous system tissue in the eye and optic nerve. Glaucoma is a condition in which rising pressure in the eyeball progressively harms the retina and optic nerve. Since nerve tissue doesn't regenerate well in mammals, loss of vision is irreversible. This is one of many conditions for which the ability to regenerate nerve tissue would be a great benefit.

Since its discovery, reprogramming has been used to produce induced pluripotent stem cells from any other type of cell. That process has been found to reverse age-related changes in epigenetic patterns and mitochondrial function characteristic of cells in old tissues. Introducing the factors capable of reprogramming cells into a living animal may produce effects akin to stem cell therapy by converting a small number of cells into induced pluripotent stem cells, followed by stem cell signaling that beneficially affects tissue health more broadly. Alternatively, many cells may have their epigenetic markers reset to a more youthful state without losing their identity to become induced pluripotent stem cells. Or both. Beyond this, there is certainly the threat of cancer or structural damage to tissue through the conversion of too many cells, and this class of therapy will require careful development to ensure safety, even as the mouse data continues to look quite interesting.

David Sinclair has been pushing an epigenetic-centric view of aging of late, with analogies to information systems and computing. The most interesting part of the the supporting work suggests that DNA repair of double strand breaks has the side-effect of driving alteration of the epigenome in characteristic ways with age. That will be an important connection between stochastic nuclear DNA damage and deterministic global effects throughout the body, should the evidence continue to hold up.

As this illustrates, however, epigenetic change is a downstream issue in aging, a reaction to events and a changing environment, not a first cause. Fixing it may or may not turn out to be particularly useful in the broader picture of aging, depending on exactly where it sits in the web of cause and consequence. As a comparable example, hypertension is a major downstream issue in aging. It is far removed from root causes such as cross-link formation and inflammation, but is also a proximate cause of many forms of further dysfunction, such as pressure damage to delicate tissues in the brain. Controlling hypertension without addressing its causes is both possible and beneficial - but the benefits are limited by the fact that those root causes are still there, chewing away at the body in a thousand other ways.

Scientists reverse age-related vision loss, glaucoma damage in mice

Scientists have successfully restored vision in mice by turning back the clock on aged eye cells in the retina to recapture youthful gene function. The team used an adeno-associated virus (AAV) as a vehicle to deliver into the retinas of mice three youth-restoring genes - Oct4, Sox2, and Klf4 - that are normally switched on during embryonic development. The three genes, together with a fourth one, which was not used in this work, are collectively known as Yamanaka factors. The treatment had multiple beneficial effects on the eye. First, it promoted nerve regeneration following optic-nerve injury in mice with damaged optic nerves. Second, it reversed vision loss in animals with a condition mimicking human glaucoma. And third, it reversed vision loss in aging animals without glaucoma.

The team's approach is based on a new theory about why we age. Most cells in the body contain the same DNA molecules but have widely diverse functions. To achieve this degree of specialization, these cells must read only genes specific to their type. This regulatory function is the purview of the epigenome, a system of turning genes on and off in specific patterns without altering the basic underlying DNA sequence of the gene.

This theory postulates that changes to the epigenome over time cause cells to read the wrong genes and malfunction - giving rise to diseases of aging. One of the most important changes to the epigenome is DNA methylation, a process by which methyl groups are tacked onto DNA. Patterns of DNA methylation are laid down during embryonic development to produce the various cell types. Over time, youthful patterns of DNA methylation are lost, and genes inside cells that should be switched on get turned off and vice versa, resulting in impaired cellular function. Some of these DNA methylation changes are predictable and have been used to determine the biologic age of a cell or tissue. Yet, whether DNA methylation drives age-related changes inside cells has remained unclear. In the current study, the researchers hypothesized that if DNA methylation does, indeed, control aging, then erasing some of its footprints might reverse the age of cells inside living organisms and restore them to their earlier, more youthful state.

Reprogramming to recover youthful epigenetic information and restore vision

Ageing is a degenerative process that leads to tissue dysfunction and death. A proposed cause of ageing is the accumulation of epigenetic noise that disrupts gene expression patterns, leading to decreases in tissue function and regenerative capacity. Changes to DNA methylation patterns over time form the basis of ageing clocks, but whether older individuals retain the information needed to restore these patterns - and, if so, whether this could improve tissue function - is not known. Over time, the central nervous system (CNS) loses function and regenerative capacity. Using the eye as a model CNS tissue, here we show that ectopic expression of Oct4, Sox2, and Klf4 genes (OSK) in mouse retinal ganglion cells restores youthful DNA methylation patterns and transcriptomes, promotes axon regeneration after injury, and reverses vision loss in a mouse model of glaucoma and in aged mice. The beneficial effects of OSK-induced reprogramming in axon regeneration and vision require the DNA demethylases TET1 and TET2. These data indicate that mammalian tissues retain a record of youthful epigenetic information - encoded in part by DNA methylation - that can be accessed to improve tissue function and promote regeneration in vivo.

The Longevity.International group has for the past few years been turning out sizable documents on a regular basis as a part of an attempt to exhaustively catalog groups in academia, industry, government, and venture capital that are either working on or supporting the development of treatments that have the potential to slow or reverse aging. A perspective and digest of this work has now emerged in book form, and seems worth a look for those already passingly familiar with the community.

In "Longevity Industry 1.0 - Defining the Biggest and Most Complex Industry in Human History", seasoned Longevity industry professionals Dmitry Kaminskiy and Margaretta Colangelo distill the complex assembly of deep market intelligence and industry knowledge that they have developed over the past 5 years into a full-scope understanding of the global Longevity Industry, showing the public exactly how they managed to define the overwhelmingly complex and multidimensional Longevity Industry for the first time, and how they created tangible framework for its systematization and forecasting.

The book features first of its kind coverage of entirely new segments and sectors of the rising Longevity Industry, including Longevity Politics and Governance, the Longevity Financial Industry (including coverage of AgeTech, WealthTech, FinTech, and the coming rise of new financial instruments and derivatives), the current state and forecasts on the Global Industrialization of Longevity to Scale, and an overview of the near-future trajectory of the Longevity Industry's evolution 2020-2025.

Link: https://www.longevity-book.com/

Osteoporosis is the name given to the loss of bone density with age, producing severe consequences in the later stages. The proximate cause is a growing imbalance between the constant activity of osteoblast cells that that create bone and osteoclast cells that break down bone. Researchers here delve into the regulation of osteoclast function, and find a lineage of cells that might be targeted to reduce osteoclast activity in later life. This is a compensatory potential class of therapy, rather than an approach that addresses the root causes of the issue, but nonetheless interesting.

New research has discovered a cell type that governs the way bones form and maintain themselves, opening up a potential target for future therapies for bone disorders like osteoporosis. A rodent study showed that bone marrow adipogenic lineage precursors (MALPs) play a distinct role in the way bones remodel themselves. Defects in this process are the key issue at play in osteoporosis, so a therapy using these MALP cells to better regulate bone remodeling could result in better treatments.

Healthy bone maintenance is a balance between osteoblasts, which secrete the materials necessary to form new bone, and osteoclasts, which absorb old bone material to make way for the new. A disruption in this balance one way or the other can result in unhealthy bone. In the case of osteoporosis, overactive osteoclasts eat away at bone faster than it can be reformed, resulting in bones that are less dense and more susceptible to fracture. The general consensus among scientists was that osteoblasts and osteocytes, the cells within fully-formed bone, were the ones that kicked off the production of osteoclasts to begin the remodeling of bone. On the other hand, the role of adipocyte lineage cells, such as MALPs, in regulating the resorption of bone was not known.

MALPs are the precursors for adipocytes that carry fats, called lipids, inside bone marrow. Recent studies better cleared up how MALPs appear to factor in bone turnover. They showed that MALPs, but not osteoblast or osteocytes, have cell-to-cell contact with osteoclasts. Additionally, using advanced sequencing techniques at a single cell level, researchers found that MALPs secrete RANKL, a protein essential for forming osteoclasts, at a high level.

With that information, researchers studied mice with RANKL deficiencies in their MALPs. From the point those mice turned a month old, the researchers saw 60 to 100 percent higher density of the spongy components of long bones (like the femur) and vertebrae, something the researchers qualified as "a drastic increase" compared to typical mouse bone mass. Since the osteoblasts and osteocytes continued to work as they always do, it would seem that MALPs and their RANKL secretions have been pinpointed as the main driver of osteoclast function and the absorption of existing bone.

Link: https://www.pennmedicine.org/news/news-releases/2020/november/potential-cellular-target-for-eliminating-bone-breakdown-in-osteoporosis-found

Bone loses mass and strength with age, leading to the condition called osteoporosis. The extracellular matrix of bone is dynamically remodeled throughout life, built up osteoblast cells and broken down by osteoclast cells. Osteoporosis is the result of a growing imbalance in cell activity and cell creation that favors osteoclasts. There are many contributing causes, and some uncertainty of which of these causes are more or less important. The chronic inflammation that accompanies aging does appear to be important, particularly that connected to the senescence-associated secretory phenotype (SASP) of senescent cells.

Given that osteoporosis is an imbalance, there are many potential ways to treat the condition, only some of which address the root causes. Any methodology that enhances osteoblast activity to a suitable degree or suppresses osteoclast activity to a suitable degree should be compensatory and beneficial, all other things remaining equal. That said, one would expect targeting the root causes of the imbalance to be a better approach, more likely to produce a larger effect size, and likely to have other beneficial effects elsewhere in the body. For example, the use of senolytic drugs to remove senescent cells is beneficial in many ways beyond the plausibly beneficial impact of a reduced SASP on processes of bone maintenance.

Current advances in regulation of bone homeostasis

Bone homeostasis in the adult skeleton is complex processes. Human skeletal tissue is a constant state of remodelling. The three main bone cells involve in this remodelling process - osteoblasts, osteoclasts and osteocytes via regulation of molecular signalling pathways. In bone remodelling, the discrete zones of bone are resorbed by osteoclasts and substituted by fresh bone by osteoblasts, allowing for repair of bone micro-injury and adapting of bone niche for control of mechanical strengths.

Osteoblast cells are energetic in protein synthesis and matrix secretion to preserve and form new healthy bones. Following mineralization of bone matrix, fully differentiated and matured osteoblasts become osteocytes and are implanted in the bone matrix. During bone remodelling process, mechanosensory cells, osteocytes act as bone orchestrators. This remodelling process is regulated by several local (e.g., growth factors, cytokines, chemokines) and systemic (e.g., estrogens) factors that all together subscribe for bone homeostasis.

In bone modelling process, i.e., during bone development and bone resorption stages, osteocytes act autonomously to fine-tune bone structure. Interestingly, in bone remodelling process, these cells act recycler to restore and keep skeletal health. After osteoclast-mediated bone resorption sequence, the eroded surface of trabecular bone is engaged by osteoblasts that make bone matrix and then undertake mineralization. Under normal physiological conditions of bone homeostasis, osteoclastic action is closely associated with osteoblastic action in such a way that the eroded bone is completely exchanged by fresh bone. Definitively, fluctuating this homeostatic equilibrium in favour of excessive osteoclast activity turns to bone pathological conditions such as osteoporosis, Paget's disease, rheumatoid arthritis (RA), osteoarthritis, and autoimmune arthritis.

Osteoporosis can be prevented and improved musculoskeletal health by using numerous pharmacotherapies such as biphosphonates; selective estrogen receptor modulators (SERMs); hormone therapies; strontium ranelate; denosumab (a human monoclonal antibody with specificity for RANKL); romosozumab (a monoclonal antibody that binds to and inhibits sclerostin) or stimulating bone formation called anabolic medications e.g., PTH preparations and calcitonin therapy have been verified the effects of increased bone mineral density and decreased risk of skeletal fractures.

However, these treatments have some side effects, such as oily skin, fluid retention, nausea, long-term toxicity, and even prostate cancer in males and thus natural therapies that incur better therapeutic activities and fewer side effects are hunted. Therefore, searching for small molecules that precisely suppress osteoclastic action is a favourable approach of the drug discovery for the treatment and management of bone-related diseases including osteoporosis.

Senescent cells accumulate with age in all tissues, and contribute to aging via secreted signals that provoke inflammation and tissue restructuring. This portion of aging is a malfunction of a system that normally aids in regeneration and resistance to cancer. Senescent cell signaling is beneficial in the short term, attracting immune cells to areas of damage that should be policed for potentially cancerous cells, or coordinating the interactions of cells needed to efficiently heal an injury. In these cases, in a young individual, the senescent cells involved are quickly destroyed once their task is complete. It is when this needed destruction falters with age, and signaling becomes constantly present, that the problems start. As researchers examine the changing presence of factors in blood and tissue samples, many of these age-related alterations are traced back to the activity of senescent cells.

Extracellular vesicles (EVs) are membrane bound vesicles which vary from nanometer to micrometer in size and carry a diverse set of factors. Recently, our group investigated how circulating EVs change with age, the cell types responsible, and the response of these factors to rejuvenation therapies. Profiling of EV cargo revealed greater expression of inflammation-associated microRNAs such as miR-146a, miR-21, let-7a, and miR-223 in old plasma EVs compared with young. These microRNAs are predicted to target multiple intracellular signaling cascades which regulate cellular responses to external stimuli.

To determine the cell types responsible for changes in circulating EV microRNAs, we assessed EVs secreted by young and old peripheral blood mononuclear cells (PBMCs) in-vitro as well as plasma EVs isolated from old mice reconstituted with young or old bone marrow. However, EV microRNAs were similar in both models, suggesting that circulating cells have a minor contribution to the microRNAs identified this study. Further investigation into potential cell sources revealed that induction of senescence in-vitro and in-vivo, using gamma irradiation, mimicked the changes observed in old mice such as increased levels of circulating EVs and increased expression of EV associated miR-146a, mIR-21, and let-7a.

Interestingly, senolytic therapy using dasatinib + quercetin (D+Q) reduced the expression of these microRNAs in the plasma of old mice, supporting that senescent cells or the pathways targeted by these compounds contribute to increased expression in the circulation. Collectively, this data demonstrates that aging and cellular senescence leads to increased levels of circulating EVs, and that these EVs impair cellular responses to activation. Pharmacological targeting of senescent cells partially rejuvenated the microRNA profile and functional effects of old plasma EVs.

Senescent cells secrete cytokines, growth factors, and proteases which alter neighboring cell function. This secretome is collectively referred to as the senescent associated secretory profile (SASP) and the adverse effects of senescent cells are largely attributed to this profile. More recent definitions of the SASP have been expanded to include EVs. Secretion of EVs by senescent cells into the circulation could be one mechanism by which senescent cells promote cell dysfunction, as persistent uptake of senescent-EVs may lead to sustained changes in cellular function. Therefore, approaches aimed at targeting senescent cells may help reduce circulating senescent-EV levels and limit the impact senescent cells have on cells throughout the body.

Link: https://doi.org/10.18632/aging.104213

The practice of calorie restriction reliably improves health and extends life span in near all species tested to date. Many of the pharmacological and genetic approaches to slowing aging have emerged from studies of the cellular maintenance mechanisms triggered into greater activity by calorie restriction, or the nutrient sensing mechanisms that govern initiation of the calorie restriction response. None of these approaches have yet demonstrated themselves to be any better than the actual practice of calorie restriction, and thus while scientifically interesting, are perhaps not a good point of focus for the growing longevity industry.

The health benefits of dietary restriction have long been known. Recently, it has become clear that restriction of certain food components, especially proteins and their individual building blocks, the amino acids, is more important for the organism's response to dietary restriction than general calorie reduction. On the molecular level, one particular well-known signalling pathway, named TOR pathway, is important for longevity. "We wanted to know which factor is responsible for measuring nutrients in the cell, especially amino acids, and how this factor affects the TOR pathway. We focused on a protein called Sestrin, which was suggested to sense amino acids. However, no one has ever demonstrated amino acid sensing function of Sestrin in a living being."

"Our results in flies revealed Sestrin as a novel potential anti-ageing factor. We could show that the Sestrin protein binds certain amino acids. When we inhibited this binding, the TOR signalling pathway in the flies was less active and the flies lived longer. Flies with a mutated Sestrin protein unable to bind amino acids showed improved health in the presence of a protein-rich diet."

If the researchers increased the amount of Sestrin protein in stem cells located in the fly gut, these flies lived about ten percent longer than control flies. In addition, the increased Sestrin amounts only in the gut stem cells also protected against the negative effect of a protein-rich diet. "We are curious whether the function of Sestrin in humans is similar as in flies. Experiments with mice already showed that Sestrin is required for the beneficial effects of exercise on the health of the animal. A drug that increases the activity of the Sestrin protein might therefore be in future a novel approach to slow down the ageing process."

Link: https://www.mpg.de/16053584/1124-balt-x-positive-effector-behind-reduced-food-intake-identified

The longevity industry is presently still quite young, a hundred and something companies that are largely still at the preclinical stage of development, most founded in the last couple of years. Even if we want to be broadly generous as to which companies and projects are to be included in our definition of the industry, no newly developed therapies to treat the mechanisms of aging have yet been approved by the FDA, although a few have made it to phase 3 clinical trials. This is just a matter of time, however; it can take a decade of hard work to go from an idea to an approved therapy, and very few longevity industry companies are even half that age.

Of perhaps more immediate interest are existing approved drugs that appear to have a meaningful effect on mechanisms of aging. The most important of these are widely used chemotherapeutics that have been found to selectively kill senescent cells, and thereby produce rejuvenation in mice. No-one noticed this potential for intervention in the aging process while such drugs were being developed in animal models of cancer and used in cancer patients, for all the obvious reasons. The dosing was quite different, the lifespans of the animals and patients largely quite short, and the disruptions of cancer and high dose chemotherapy masked the benefits that can be obtained via a different approach to usage.

Back to the new therapies under development and the rapidly growing longevity industry, there is more than enough work taking place at present for a community of speculators and spectators to emerge, of various degrees of organization, professionalism, and commercial inclinations. I'll point out one of the more market-focused examples today, with a couple of posts that tour the handful of longevity industry clinical trials underway or recently conducted. Not all are targeting aging, such as the work of Gensight on allotopic expression of mitochondrial genes to treat inherited mitochondrial disease, and these are only relevant because they exercise approaches that can later be turned to address aging.

#015: A Review of Every Single Longevity Therapy in Clinical Trial Today. (PART 1)

Currently there are 28+ anti-aging therapies in human clinical trials spanning a variety of strategies, targets, indications, companies, and modalities. The trials are conducted by companies - private and public - but also universities and non-profit groups. There are also perhaps 100 more pre-clinical companies working on aging in addition to this effort. If any one of the therapies in the first volley on the problem of aging achieve success - even if modest - it could trigger investor hype rivaling the biggest bubbles in history. The zero to one moment in human life extension will change everything.

With the exception of maybe Nir Barzilai's TAME metformin trial (not yet registered), none of the anti-aging therapies currently being tried directly use aging as their clinical endpoint. Most trials instead measure a therapy's efficacy with respect to a specific age-related disease rather than aging itself. Or sometimes the indication is a disease that can be treated with a tool developed from an aging perspective. This is because: (1) The FDA does not recognize aging as an indication (yet). (2) It is expensive to run trials that measure lifespan in humans. (3) We don't have have robust surrogate biomarkers for aging (yet). (4) It is easier to demonstrate clinical significance in an age-related disease than aging itself.

#016: Every Single Longevity Therapy in Clinical Trial Today (PART 2)

Aging is a malleable biological process. Scientists have been precisely turning the knobs of aging in model organisms since the 1990s. Presently we have reached an inflection point: Therapies developed in the context of longevity science are being tested in human patients today.

LYG-LIV0001 - LyGenesis

Perhaps one of the more ambitious clinical trials. LyGenesis is a Juvenescence-backed startup spun out of research at the University of Pittsburgh. The company is attempting to regrow livers by injecting allogenic liver cells into patient lymph nodes. The lymph nodes act as bioreactors and slowly regrow into functional livers - at least in the pre-clinical experiments done on pigs. Their Phase 2 trial includes patients with end-stage liver disease. If successful the company plans to also use the same strategy to regrow the thymus (reversing immunosenescence) and also pancreatic islet cells (reversing diabetes).

SkQ1 - Mitotech

Mitotech is an anti-aging company that develops therapies that protect the mitochondria from reactive oxygen species (ROS). SkQ1 is an anti-oxidant that can easily penetrate the mitochondrial membrane where it can inhibit ROS. In particular, SkQ1 protects cardiolipin, an important protein found in the inner mitochondrial membrane. Dry eye might not sound like a very sexy anti-aging therapy. But this trial is just one small step in the journey of treating mitochondrial diseases, many of which are age-related.

Nicotinamide riboside - ChromaDex

NAD+ levels decrease with age so the hypothesis is that boosting NAD+ levels can have potential anti-aging benefits. There are several chemical precursors to NAD+ but the two most popular are nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN). ChromaDex is the patent holder of NR and sponsors a number of clinical trials to support the case for its potential anti-aging properties. This time they are measuring hospitalization duration for patients with tissue damage. Given the small size of the study (84 participants) and probable heterogeneity in the illnesses, I have a hard time seeing how anything definitive will be elucidated. This is just one trial of many exploring the benefits of NAD+ precursors / booster. These NAD+ precursor compounds are generally considered safe so I'm excited to see what can benefits can be demonstrated in trials.

Researchers here report on their efforts to improve stem cell therapies by steering the cells to migrate to areas of damage in the body. These cells travel through the body towards regions of inflammatory signaling. The researchers adapted one of these signal molecules to make it unlikely to significantly provoke cells into an inflammatory response, while still being attractive to stem cells. Using this molecule to steer stem cell migration to specific locations results in an improved efficacy of stem cell therapy in animal models, a good demonstration of the potential utility of this approach.

Nearly 15 years ago, researchers discovered that stem cells are drawn to inflammation, a biological "fire alarm" that signals damage has occurred. However, using inflammation as a therapeutic lure isn't feasible because an inflammatory environment can be harmful to the body. Thus, scientists have been on the hunt for tools to help stem cells migrate to desired places in the body. This tool would be helpful for disorders in which initial inflammatory signals fade over time - such as chronic spinal cord injury or stroke - and conditions where the role of inflammation is not clearly understood, such as heart disease.

In the study, the scientists modified CXCL12 - an inflammatory molecule which the team previously discovered could guide healing stem cells to sites in need of repair - to create a drug called SDV1a. The new drug works by enhancing stem cell binding and minimizing inflammatory signaling, and can be injected anywhere to lure stem cells to a specific location without causing inflammation.

To demonstrate that the new drug is able to improve the efficacy of a stem cell treatment, the researchers implanted SDV1a and human neural stem cells into the brains of mice with a neurodegenerative disease called Sandhoff disease. This experiment showed SDV1a helped the human neural stem cells migrate and perform healing functions, which included extending lifespan, delaying symptom onset, and preserving motor function for much longer than the mice that didn't receive the drug. Importantly, inflammation was not activated, and the stem cells were able to suppress any pre-existing inflammation.

The researchers have already begun testing SDV1a's ability to improve stem cell therapy in a mouse model of ALS, which is caused by progressive loss of motor neurons in the brain. Previous studies indicated that broadening the spread of neural stem cells helps more motor neurons survive, so the scientists are hopeful that strategic placement of SDV1a will expand the terrain covered by neuroprotective stem cells and help slow the onset and progressive of the disease.

Link: https://www.sbpdiscovery.org/news/worlds-first-drug-guides-stem-cells-to-desired-location-improving-their-ability-to-heal

The immune system ages along with everything else in the body, entering the states of immunosenescence and inflammaging. Immunosenescence is a growing ineffectiveness of the immune response, while inflammaging is a constant and inappropriate activation of the immune response. Researchers here make the point that immune aging might be thought of as being only loosely coupled to the rest of aging, as it is possible, for example, for chronic infections such as HIV to bring on aspects of immunosenescence and inflammaging far earlier in life than would otherwise be the case.

Aging has been associated with a myriad of both acute and chronic diseases. At the core of these diseases, the change in the host immune system with age could either have contributed to the cause as it is the host main defence mechanism against foreign pathogens or its functionality being impacted by these diseases and conditions. However, the change in the immune system with age could also be seen as an adaptation process to save resources for the host rather than it being detrimental.

This is because developing competent naïve T cells has only about 1-2% success rate due to the various stringent selection processes. Therefore, biological processes such as thymic involution could be seen as advantageous to the host from an energetic or evolutionary point of view. One of the main arguments that thymic involution is detrimental to the host is due to the reduction of naïve T cells being produced, leading to a narrower repertoire for new antigens and perhaps reduced vaccine efficacy often observed in the elderly, while this may have been a successful programmed process for the shorter-lived humans in the past centuries and before the extended human lifespan has revealed the probable need to reverse this adaptation.

Chronic low-grade inflammation is a commonality between individuals that exhibit chronic stress, obesity, aging, sleep loss, gut dysbiosis, CMV infection, dysregulated immune cell functions, and accumulation of SASP cells such as fibroblasts. Chronic low-grade inflammation is defined as a higher baseline of pro-inflammatory cytokines in the circulation though the source and specific cytokines might differ slightly between these "diseases" in the absence of foreign pathogen infection. In terms of impaired immunity, both human and animal studies have shown that chronic stress reduces various immune functional capacities. The presence of impaired immunity and low-grade chronic inflammation could be the underlying factors that exacerbate pathology in various disease contexts.

Thus, it is important that we redefine and stress that the definition of immunosenescence is the dysfunctionality of the immune system and should encompass some features of low-grade chronic inflammation. Though this phenomenon is often seen in aged individuals, it is also possible in younger adults as it could be "accelerated immunosenescence", especially for T cells, as shown in CMV and HIV seropositive young patients. Even early in life, the impact of CMV can be observed. This highlights that other factors other than chronological age could determine this level of senescence of the immune system, especially for T cells which are prone to proliferation. Overall, rethinking the causing agents and implications of immunosenescence will help shift the perspective that this phenomenon is not attributed to age alone, especially with the global rising rate of obesity and chronic stress of modern-day life in the young.

Link: https://doi.org/10.1007/s00281-020-00824-x