Fight Aging!

Well, here we are again, at the end of another pandemic year, a year older and - hopefully - a year wiser and more knowledgeable. I said all that really needs to be said on the topic of COVID-19 as an age-related condition at the end of last year. We might hope that, given widespread vaccination, the pandemic will become a topic of diminishing importance as the year ahead progresses, even given the present round of variants, fears, and reintroduction of restrictions.

Advocacy for Aging Research

Have we finally made significant progress in convincing the world that aging is the cause of age-related disease, that greater longevity is highly desirable, and that the treatment of aging should long have been a priority? The war on cancer is 50 years old; we can learn from it, and we must, as the war on aging had better move faster than that.

Treating aging as a medical condition is no longer the fringe idea it once was, yet the anti-aging marketplace remains a pit of snake oil and a ball and chain holding back progress, too many people are talking about only modest gains rather than the goal of radical life extension, and the majority of medicine for late life conditions still attempts the impossible of extending life without extending health. Further, all too many people think of late life disability as unavoidable, and this causes them to doubt approaches to extend life span. Still, treating aging is now explicitly the goal of research into aging. While the popular media continues to do a terrible job in explaining in the field, and governments, despite lobbying efforts, are still stuck in yesteryear, this may well be a whole new era. People are asking: should we work to end aging?

There are more patient advocates and more scientists talking about this concept, and soon there will be many physicians focused on longevity. Perhaps at some point soon the first rejuvenation technologies, such as senolytics, become so obviously beneficial that people will stop talking about ethics and just get on with preventing the suffering caused by aging and age-related disease. Priorities in research and the world at large are still not appropriate for the harms done by aging, but at least some people think that we should be aiming high, running moonshot projects to produce new therapies that will make a real difference. There is a strong economic argument for major investment in aging research and the development of therapies. The cost of failing to aggressive pursue rejuvenation therapies, both financial and measured in suffering and death, is huge.

Longevity Industry

It is interesting to look back at a January post on what to expect in the longevity industry in 2021. Investment in the industry is certainly growing, and many funds are actively creating companies rather than waiting for companies to arise. There will likely be a range of longevity industry specific SPACs soon enough, given the popularity of that approach to taking companies public. Michael Greve launched a $300M expansion of his Kizoo fund, specifically aimed at rejuvenation biotechnology after the SENS model. Apollo Ventures launched a new $180M fund, and Korify Capital launched a $100M fund a couple of months later. Cambrian Biopharma raised another $100M for their efforts. An industry advocacy group has formed, the Longevity Biotech Association.

The number of biotech startups is growing, and in Europe as well as the US. Some are very well capitalized, such as NewLimit, launched with a sizable warchest to develop in vivo reprogramming therapies. Numerous companies are now working on approaches to treat mitochondrial aging. While more funding and more biotech startups are good things, many of these companies are working on less ambitious approaches, relating to stress response upregulation or similar alterations to metabolism, or unguided drug discovery that will most likely discover more metabolic tweaks that modestly slow aging in mice. Others intend to target only skin aging to use the less costly cosmetics regulatory pathway, or work in the supplement space for similar reasons. Examples include Gerostate Alpha, Genflow Biosciences, Yuva Biosciences, Elysium Health, and the Maximon companies. Would that more groups come to choose better projects to focus on!

Various updates were noted from other companies that have been working on their projects for the past few years: Calico, Lygenesis; Selphagy; BioViva announced results from a small gene therapy trial; IntraClear Biologics; Repair Biotechnologies (a few times); Cellvie; Elastrin Therapeutics; Oisin Biotechnologies; Insilico Medicine; Revel Pharmaceuticals; Rejuvenate Bio; Leucadia Therapeutics (a few times); UNITY Biotechnology.

The Community

I have been paying less attention to events this past year, given that so many were virtual only, and virtual events offer little in the way of networking opportunities. Still, a few notes from various sources: the Aging, Geroscience and Longevity Symposium; the 7th annual AARD and 8th annual AARD meetings, as that conference series forged ahead bravely, pandemic or no pandemic; and the 2021 Longevity Week in London.

There are plenty of interviews and profile pieces to be found out there, many in video form given the Foresight Insitute salons, Live Longer World podcasts, and OnDeck Longevity community. A few that I noted: investor Ronjon Nag; James Peyer of Cambrian Bio; Aubrey de Grey, formerly of SENS Research Foundation; George Church on his broad portfolio of ventures; some notes on Jim Mellon; a profile of Michael Greve; epigenetic clocks with Morgan Levine, Steve Horvath, and Vadim Gladyshev. Also a couple of book reviews to add to that list: Ageless and Lifespan.

The SENS Research Foundation continues to do well in year end fundraisers - don't forget to donate this year! The foundation conducts important work in the field of rejuvenation, advancing neglected but important projects needed to repair the damage of aging. Earlier this year they were the recipient of more than $20M in charitable donations in connection with a cryptocurrency launch, and are hiring more scientists. The Methuselah Foundation, meanwhile, literally finds itself with more resources than it can easily access or spend, hundreds of millions of dollars at the time of writing, a result of strange machinations in the cryptocurrency space. The foundation also announced a winner for their Vascular Challange competition. Lifespan.io has extended their crowdfunding efforts to running small human trials of simple therapies, starting with mTOR inhibitors. Hopefully more to come as this approach to moving the field forward gains support.

The Forever Healthy Foundation continues to turn out great analyses of available therapies as a resource for all interested parties. The Astera Institute's Rejuvenome project launched this year, a sizable philanthropic effort to perform useful life span studies in mice that academia and industry will not get to on their own. Another new organization offers the Impetus Grants for high risk high reward aging research. The Radical Life Extension Group are performing small human trials of simple potential therapies such as plasma dilution. The Longevity Science Foundation launched in Europe with a sizable committment to research funding. Last but not least, VitaDAO is applying a distributed organization structure to funding aging research and development, and seems off to a good start.

Senolytics and Other Senotherapeutics

Senescent cells are influential enough on aging that models of aging based solely on senescent cell accumulation produce decent predictions. Accumulation of senescent cells has a bidirectional relationship with immune aging: the immune system clears senescent cells, but is harmed by their presence and inflammatory secretions. Cellular senescence spreads through tissues once established in any one location, a phenomenon possibly mediated by neutrophils. Bcl-xL is one of many senolytic drug targets, and it is found to correlate with aspects of aging in late life, also a sign of the relative importance of cellular senescence in aging. Senescent cells may explain the inverse relationship between cancer and neurodegeneration. Researchers are beginning to put numbers to senescent cell counts by age, such as in the immune system.

The number of companies working on senolytic and other senotherapeutic therapies continues to increase, as does the variety of approaches to the selective destruction of senescent cells, or the suppression of their activities, or the prevention of senescence. Those approaches include: the use of silica nanoparticles; GLS1 inhibition; activation of invariant natural killer T cells; identifying and then targeting surface markers selective for the senescent state, with candidates such as B2M; activation of the NRF2 pathway; supplementation with procyanidin C1; fisetin, still overdue for confirmation of its senolytic capacity in humans; supplementation with dihomo-γ-linoleic acid; NANOG overexpression; acid ceramidase inhibition; inhibiting IKK/NF-κB activation; piperlongumine, which continues to be comparatively poorly researched. The research and development communities are still far too slow to start clinical trials for the many age-related conditions that might be successfully treated via elimination of senescent cells from aged tissues. Nonetheless, there are some signs of progress here, such as calls for trials in cancer patients, though not everyone in the cancer research community is wholehearted enthused. Senescent cells are both helpful and harmful in the context of shutting down cancer.

Data continues to roll in to support the use of senolytics in a very wide range of conditions, even though senescent cells are likely different by tissue, and early drugs variably effective by tissue. Just in the past year, and only those that I happened to notice and discuss, by no means a comprehensive list: vascular senescence in atherosclerosis (a number of groups are looking at this), and in general as a component of vascular dysfunction; neurodegenerative conditions, as senescent microglia are found in greater numbers in the brains of patients with neurodegenerative conditions such as Alzheimer's disease, and there is a good deal of supporting evidence for senolytics to be a useful treatment for Alzheimer's; senescent cells play an important role in chronic kidney disease and loss of kidney regeneration with age; several lines of work show that senescent cells harm the sympathetic nervous system; they contribute to fatty liver disease; COVID-19 severity in the aged is mediated in part by senescent cell burden, and a trial of fisetin is underway in this context; vulnerability to inflammatory conditions is in general increased by senescent cells, not just in the case of COVID-19; senescent cells are found in skin, and thus contribute to skin aging; cartilage damage in osteoarthritis is caused in part by senescent cells; cancer severity is mediated by the relationship between cancer cells and senescent cells, and senolytics may reduce precancerous lesions; liver aging is clearly caused in part by senescent cells, as is kidney aging; also diabetic retinopathy and pulmonary fibrosis, the subject of human trials and ongoing work by several research groups; fibrosis in general can be treated with senolytic strategies; the contribution of visceral fat to insulin resistance is mediated by senescent cells; retinal aging; senescent cells may slow bone fracture repair; age-related metabolic dysfunction; disc degeneration is slowed by senolytic treatment; cellular senescence may be the mechanism linking psychological stress with cognitive decline; temporomandibular joint degeneration is caused in large part by senescent cells; type 2 diabetes accelerates degeneration via an increased burden of cellular senescence; brain aging and neurodegeneration; osteoporosis; the higher risk of failure of transplantation of old organs; the age-related decline in neurogenesis; poor outcomes in stem cell therapies due to senescence in cultured cell populations; prevention of scarring in nerve injury; gliosis and tau aggregation in tauopathies such as Alzheimer's disease.

All this said, continual clearance of senescent cells, as opposed to intermittent clearance, is probably a bad idea, as these cells do serve useful purposes when present for the short term. Thus senolytic vaccines that encourage immune destruction of senescent cells are an interesting option, but may not the right path forward. Early life use of senolytics may also be harmful over the long term. A pleasant surprise is that senolytic therapy does in fact improve muscle regeneration following injury in old mice, indicating that the negative effects of slow clearance of senescent cells in old age outweigh the negative effects of clearing those cells during the regenerative process.

Surprisingly little progress has been made on cheap, simple ways to assess the burden of senescent cells. Many different approaches have been proposed, but none are yet easily available for clinical use. Measuring extracellular vesicles from senescent cells in urine is one such proposed assay, assessing ANGPTL2 levels in blood is another. Researchers have also suggested measuring certain fatty acids that enter the blood and urine when senescent cells die.

The NIH has launched SenNet, a major research initiative in the biochemistry of cellular senescence. There is more evidence these days for mTOR inhibitors as senotherapeutics, not killing senescent cells but preventing senescence via upregulated autophagy. Naked mole-rats apparently employ cholesterol metabolism to enable cells to resist senescence, though it remains to be seen as to what can be achieved with this knowledge. It turns out that all senescent cells have genomic damage, produced on the transition into the senescent state. A last thought for this section: is exercise a mild senotherapeutic, given the evidence for a reduced burden of cellular senescence, and how about similar data for calorie restriction? Color me dubious as to the usefulness of this designation. If we start describing exercise as a rejuvenation therapy, then our bar is set far too low.

Inflammation and Other Immune Aging

The adaptive immune system ages in its own way distinct from the aging of the innate immune system, including excessive T cell expansion, disruption of naive T cell quiescence, and detrimental interactions between T cells and fat tissue that produce inflammation. Thymic involution is a noteworthy component of adaptive immune aging, and the activities of dendritic cells in response to infection may be important in this process. Persistent infection with cytomegalovirus is also important in the decline of the adaptive immune system. Researchers see CD4+/CD8+ cell ratio as a useful biomarker of immune aging.

Every aspect of immune aging should be a high priority target for intervention. Some groups are looking at ways to suppress macrophage inflammatory signaling, such via upregulation of mitochondrial uncoupling in these cells. Age-associated B cells also contribute to chronic inflammation, and might be productively cleared from the body. Memory B cells, on the other hand, decline in number and should be restored. Researchers are investigating the cGAS-STING pathway, microRNA-92a inhibition, CD40L, TLR4, MG53, and CXCL9 as targets for the suppression of unwanted inflammation in connection with various conditions.

Regrowth of the thymus is an important goal, and a step towards a small molecule approach has been made with the identification of Rac1 inhibition as a possible target. Naked mole rats undergo little thymic involution with age, and actually have three thymi rather than just one; as with many aspects of this long-lived, slowly aging species, it is a question mark as to whether there is anything useful that can be accomplished in the near term with this information. The aging of lymph nodes, coordination sites for the immune response, may turn out to be similarly important in later stages of life, limiting the degree to which a restored supply of immune cells could increase immune function.

The aging of the immune system ties into most other issues in aging. Immunosenescence is clearly important in Alzheimer's disease, as noted by numerous sources, as is chronic inflammation in the brain, also the subject of numerous discussions. This is also true of vascular inflammation in the brain. Loss of neurogenesis in the aging brain is partly mediated by inflammatory signaling. Inflammation drives osteoarthritis. It also involves and negatively affects the behavior of macrophage cells, disrupting their normal function, is the major cause of pituitary gland aging, and contributes to osteoporosis. Further, it harms proteostasis throughout the body. Chronic kidney disease has a bidirectional relationship with inflammatory immune aging.

When it comes to treating immunosenescence, exercise has been shown to at least modestly improve matters, as it does for most aspects of aging.

Changes in hematopoiesis, and damage to hematopoietic stem cell populations, are critical parts of immune aging. The bone marrow niche is responsible for much of these harmful changes, and chronic infection some of the rest. Researchers have considered autophagy upregulation as an approach to improving hematopoiesis. Further, CDC42 inhibition continues to look like a promising approach to improve hematopoietic function in older individuals, with more results published this year on the use of CASIN as one of the candidate drugs - it also works to promote function in other aging stem cell populations. On a related note, researchers have shown that old hematopoitic stem cells do not regain their function in a young environment, which should steer thoughts on what sort of therapies might work.

Regenerative Medicine

For tissue engineering: esearchers have built thyroid organoids that can improve function in mice; early intervention with thin cartilage sheets can turn back osteoarthritis in animal models. The research community is working towards ways to produce universal cells that can be introduced safely into any patient, thereby greatly reducing the cost of cell therapies and tissue engineering.

Cell therapies for Parkinson's disease are moving forward only slowly. Cell reprogramming is being combined with prior scaffold techniques to produce muscle tissue regeneration. Muscle stem cell populations appear largely intact in old age, just inactive. Delivery of astrocyte progenitor cells helps with stroke recovery in mice. Autologous cell therapy improves outcomes in heart failure. Interestingly, stem cell therapy improves mitochondrial quality control. Transplanted retinal cells have been shown to integrate into a damaged retina. Stem cell therapy produces tendon regeneration. Stem cell therapies might be used to treat skin aging. It is by now well known that first generation mesenchymal stem cell therapies suppress age-related inflammation, and this is under consideration as a way to treat frailty, a condition strongly associated with chronic inflammation. A clinical trial of stem cell therapy for frailty was conducted successfully this year. It is possible that the death of transplanted cells is in fact the mechanism by which inflammation is suppressed in stem cell therapies.

Exosomes derived from stem cells offer a logistically simpler approach to therapy than the delivery of stem cells themselves. Exosome treatments have been showed to work in animal models: slowing aging in progeroid mice; treating disc degeneration; producing heart tissue regeneration; acting to reduce frailty in old mice.

Cardiovascular Aging

Atherosclerosis kills a quarter of humanity via heart attack, stroke, and consequences of narrowed arteries. Preclinical atherosclerosis is widespread by age 50. At root, it is a condition caused by dysfunction in the macrophage cells responsible for clearing molecular waste from blood vessel walls. Atherosclerosis cannot yet be meaningfully reversed. Could selectively targeting the right inflammatory processes achieve that goal? Hypertension is also a contributing factor, altering arterial structure to accelerate atherosclerosis, illustrated by the point that successful control of blood pressure in later life produces a meaningful reduction in mortality. Mitochondrial dysfunction can also be argued to contribute, as can clonal hematopoiesis.

In other research into atherosclerosis and its consequences, heart attacks are more severe in sedentary individuals, and one of the consequence of a heart attack is raised harmful inflammation. Incidence of stroke is declining in later life, an outcome of the slow lengthening of life span year over year. Researchers achieved reversal of atherosclerotic plaques in mice by targeting antioxidants to the cell lysosome to clear oxidized LDL, an interesting result. Unfortunately, earlier research indicating that nattokinase supplementation can reverse plaque was not replicated in a more rigorous trial, though a lower dose was used. More work is yet needed on this topic. Hunter-gatherer populations with high levels of exercise exhibit low levels of cardiovascular disease and dementia; exercise certainly helps to reduce risk in other populations, which in turn means that a substantial fraction of cardiovascular disease is self-inflicted, the result of a sedentary lifestyle. A few other interesting research results: inflammatory macrophages contribute to the formation of aneurysms; autophagy is protective in heart aging, and perhaps a useful target for therapies to slow heart aging; adjusting the production of elastic proteins in the heart may compensate somewhat for the damage of aging.

The Human Microbiome

The gut microbiome becomes uniquely dysfunctional from person to person over the course of aging, though that process is slowed by calorie restriction. Similarly there is no one universal beneficial configuration of the microbiome. Mapping the age-related changes in the gut microbiome is an ongoing process, but still in its early stages. Does reduced tryptophan intake contribute to these age-related changes? The aging gut microbiome may contribute to age-related anabolic resistance and immune system dysfunction, and thus the onset of frailty. It may also cause problems in innate immunity. Equally, the immune system helps to garden the microbiome, and its age-related decline allows for pathological microbes to grow in number. Numerous other age-related conditions and detrimental changes are influenced by the gut microbiome, including loss of neurogenesis.

Restoration of a youthful microbiome is a field in its infancy. Fecal microbiota transplantation looks like a compelling, simple approach that may work well to restore a youthful microbiome, and thereby improve function. That includes its use as a treatment for neurodegeneration. Probiotics may also work, but there is some work yet to be accomplished in order for this to be the case. Intermittent fasting helps to beneficially alter the gut microbiome to some degree; it can reduce the contribution of the aging microbiome to hypertension, for example. Icariin supplementation improves the gut microbiome in old mice, and produces consequent health and functional benefits.

The gut microbiome recieves a lot of attention in the context of aging, but how important is the skin microbiome? That is a new question, in search of an answer. Meanwhile, the oral microbiome is thought to spread inflammation into the body via damaged gums, increasing risk of Alzheimer's disease and other conditions.

Mitochondrial Aging

There is plenty of evidence for mitochondrial aging to contribute to age related conditions. Recent research that I noted this year covered a few such conditions: sarcopenia; Alzheimer's disease (mitochondrial dysfunction in Alzheimer's is a popular topic); atrial fibrillation; and immunosenescence. Much of mitochondrial dysfunction with age may stem from a loss of mitophagy, the quality control mechanism responsible for culling damaged mitochondria. There is some question over which of mitophagy or oxidative stress is the first cause, however. Loss of mitophagy can contribute to stem cell dysfunction and the aging of the brain, among many other issues.

A variety of approaches to improving mitochondrial function, some compensatory, some not, are under consideration: inhibiting complex I activity; delivery of mitochondrially targeted peptides such as elamipretide; telomerase gene therapy; D-glyceric acid supplementation; glutathione precursor supplementation; targeting prohibitins to promote mitophagy; mitochondrial transplantation is presently a hot topic and the goal of numerous initiatives, perhaps even with the goal of transplanting entirely artificial mitochondrial-like structures; targeting the mitochondrial permeability transition pore; and upregulation of mitochondrial uncoupling, if it can be achieved in a safe way.

Cancer

I pay less attention to cancer research than I used to. I am mostly interested in approaches that can produce very broad anti-cancer therapies, those capable of being applied to most or all types of cancer without much new development per type. Reprogramming of cancer cells into normal somatic cells has been suggested as a path to cancer therapies. The most promising path to a universal cancer therapy is, I think, interference in telomere lengthening. Chimeric antigen receptor immunotherapies are performing well in comparison to the prior generation of chemotherapies and radiotherapies, but still require too much work to adapt to specific types of cancer. Nonetheless, researchers are now adding chimeric antigen receptors to immune cells other than T cells, such as natural killer cells, and making other improvements, such as triggered activation. The engineering of B cells to attack cancer cells is another, similar approach. Other approaches that caught my eye: YAP upregulation; manipulation of "don't eat me" markers abused by cancers, such as CD47; targeting TRIM28 as a way to inhibiting alternative lengthening of telomeres; finding ways to make cancer cells die rather than become senescent in response to cytotoxic therapies.

Cancer survivors have a shortened life expectancy, which may be due to an increased burden of cellular senescence as a result of cell-killing therapies.

Neurodegeneration and Damage to the Brain

There are a lot of interesting correlations in aging and neurodegeneration: visual decline correlates with Parkinson's disease, for example, as does loss of kidney function, and leakage of mitochondrial DNA into the cell cytosol. Hearing loss correlates with dementia - but also with physical impairment. Aortic stiffness correlates with cognitive decline, as does any degree of raised blood pressure. Increased activation of monocytes and macrophages appears in Alzheimer's disease patients. Gum disease correlates with neurodegenerative conditions and all-cause mortality. Reduced oxygen supply to the brain also correlates with dementia. In many cases it remains unclear as to whether causation is involved, or this is a case of underlying causes of aging producing multiple pathologies at the same time. Intriguingly, cataract surgery correlates with lower risk of dementia, which indicates that the mechanism must be that reduced sensory input due to blindness accelerates brain aging.

Neurodegeneration is linked with vascular dysfunction and reduced capillary density, a feature of aging receiving more attention these days. Amyloid may contribute to this reduction in capillary density. Loss of capillary density is in effect a hallmark of aging. The hippocampus operates at the very edge of capacity, and any reduction in the supply of oxygen and nutrients will cause loss of function. The lymphatic system of the brain is also a new point of focus in Alzheimer's disease. Separately, arterial stiffening correlates with structural damage to the brain, and particularly so in diabetic patients, as one might expect. There is an ongoing debate over whether persistent viral infections contribute to Alzheimer's disease - expect more years of this back and forth over the data. Viral proteins can assist in the spread of protein aggregates, making it more than a matter of raised inflammation.

The amyloid cascade hypothesis remains at the center of research and development for Alzheimer's disease, just as α-synuclein is central to Parkinson's disease, though a lot of effort is going into adjusting it of late. Is Alzheimer's a lifestyle disease? Perhaps, though likely not as much so as is the case for type 2 diabetes. Researchers are considering splitting Alzheimer's into four subtypes based on differences in pathology and progression. There was a sizable debate over the approval of the immunotherapy aducanumab, given the poor outcomes in patients despite effective clearance of amyloid-β. Improved approaches to this sort of immunotherapy are beneficial in animal models but will they do any better in humans? Is amyloid-β pathology due to the fact that the aggregates associated with Alzheimer's disease deplete soluble amyloid-β? Or is it that misfolded amyloid-β spreads within cells, and the aggregates outside cells are less important? Amyloid-β aggregation can degrade synaptic connections. Does the amyloidosis of Alzheimer's disease actually start in the liver in some cases, in the same way as Parkinson's synucleinopathy can start in the intestinal tissues? Researchers are now suggesting that there is a tipping point in amyloid-β aggregation after which Alzheimer's is inevitable.

Loss of myelin maintenance is important in cognitive decline, as is blood-brain barrier dysfunction, allowing harmful cells into the brain. The supporting glial cells of the brain can both help and harm the blood-brain barrier in aging. Cholesterol metabolism might be important in Alzheimer's disease, but exactly how this is the case is up for debate. A great deal of evidence points to microglial dysfunction in the development of neurodegenerative conditions; these cells become more inflammatory with age, but also lose beneficial functions. They may also be important in the spread of tau aggregates. This may be aggravated by persistent viral infection. In synucleinopathies, α-synuclein pathology may be spread via lysosomal transfer between glial cells.

Assays for the early stages of neurodegenerative conditions will likely soon improve greatly. Detecting misfolded amyloid-β in blood, for example. Functioning of the glymphatic system in clearing molecular waste from the brain is coming to be seen as important in brain aging.

When it comes to discussion of therapies: tau knockdown gene therapy does well in mice, and tau immunotherapy is so far performing somewhat better in human patients than is the case for amyloid immunotherapy; telomerase gene therapy has seen one small trial, and awaits more; B cell depletion produces benefits in Alzheimer's mouse models; similarly clearance of microglia appears beneficial, as does CD22 inhibition to improve the behavior of microglia; adding new photosensitive proteins to the retina to replace the function of lost photoreceptor cells; delivery of klotho is neuroprotective; ultrasound treatment can improve mouse memory; a plagl2 / dyrk1a gene therapy restored youthful neurogenesis in mice; amyloid-clearing immunotherapies continue to be a major focus of the clinical development community even though they are failing to improve patient outcomes following successful clearance; chondroitin 6-sulphate gene therapy restored memory function in old mice; transcranial direct current stimulation has the most consistent evidence of the many approaches to electromagnetic stimulation of the brain.

Lastly, exercise does help to improve function and slow neurodegeneration, a conclusion based on extensive data. Since exercise is essentially free, even modest results are cost-effective. Recent research suggests, however, that in mice at least there is a narrow therapeutic window for exercise to improve neurogenesis. This doesn't conform to the broader findings of increased neurogenesis and benefits to function, so it will be interesting to see how this area of research proceeds. As a final thought, some high functioning older people retain good memory and functional connections in the aging brain. Why? More work is needed on this topic.

Other Age-Related Molecular Waste

Much of the world on amyloid is focused on amyloid-β and Alzheimer's disease, but there are numerous other sorts of amyloid in the aging body. Treatment of transthyretin amyloidosis is a going concern these days, though there is definitely room for improvement on the first therapies that focus more on destabilizing the problematic transthyretin forms than on actively removing them. Transthyretin amyloidosis contributes to numerous issues in aging, with growing evidence for it to be important in heart disease. in other news, amyloid contributes to muscle aging. Transient AGEs are important in the chronic inflammation attendant to metabolic diseases such as diabetes because they trigger the receptor RAGE and consequent inflammatory signaling. This can contribute to disc degeneration.

Epigenetics and Cellular Reprogramming

Epigenetic changes in aging are a hot topic these days, particularly since the rise of partial reprogramming as a way to reset epigenetic changes characteristic of aging. The present consensus is that this is a promising path to therapies to treat aging and age-related degeneration. Reprogramming is the adaptation of the process that naturally takes place during embryogenesis to clear out damage and form the embryonic stem cells that give rise to a young body. One important unanswered question is whether the epigenetic reset can be separated from dedifferentiation into stem cells; it is highly desirable to only achieve the former of those two outcomes. Reprogramming has slowed aging in progeroid mice, and was also shown to improve muscle regeneration. A range of other interesting demonstrations have been produced in recent years, such as regeneration of damaged heart muscle.

Many different projects, some with sizable funding, are attempting to build rejuvenation therapies based on reprogramming. If the cancer risk can be controlled, this could be a beneficial therapy for older people. There is clearly a great deal of work ahead in moving from early animal studies to widespread clinical use, and many challenges to solve. Related to the concept of reprogramming is the idea of introducing developmental signaling into adults in order to spur greater regeneration, an approach still at an early stage.

Work on epigenetic clocks continues apace, with the number of different clocks expanding rapidly. Some researchers argue that more attention should be given to traditional measures of frailty. For preference, more of this effort and funding directed to the relentless development of new clocks should be directed towards validating and understanding the clocks that exist. Understanding how age-related damage and dysfunction maps to specific epigenetic changes is important. It will be hard to use the clocks to assess therapies without that, and there are already too many studies publishing clock data with no accompanying health data, a trend that is detrimental to progress. Elsewhere, researchers proposed the basis for a universal mammalian clock. The GrimAge clock continues to produce good results to show it is much improved over earlier clocks. Cardiovascular health correlate with a lesser epigenetic age acceleration as measured by clocks. Epigenetic age acceleration also correlates with loss of kidney function.

Diet and exercise can be used to reduce epigenetic age by a few years, and the effects of diet are distinct from those of exercise. Heterochronic parabiosis also reduces epigenetic age in mice. Lastly, epigenetic clocks are being used with some success to establish chronological age in species where that is challenging via other means, such as lobsters.

Fasting and Calorie Restriction

Intermittent fasting as a way to modestly slow the progression of aging is a popular topic these days, and more rigor is being applied to testing fasting as a form of therapy. For Parkinson's disease, for example. Short term fasting can improve numerous measures of immune function, and this is a basis for its use in cancer patients. There is some work underway to directly compare the results of intermittent fasting versus calorie restriction in humans, an exercise long overdue. Researchers are questioning the once-daily feeding pattern in mouse studies of calorie restriction, suggesting that it may be allowing fasting-like mechanisms to operate significantly. On a related note, dogs have been found to benefit from time-restricted feeding.

That aside, calorie restriction is well known to slow aging in numerous species, and every year the research community produces more examples of specific manifestations of aging that are beneficially affected by a lower calorie intake. Calorie restriction slows cognitive decline, muscle atrophy, and lowers blood pressure and cardiovascular disease risk. Calorie restriction is proposed as an adjuvant therapy for cancer patients, and may impact cancer and cancer risk through reduced growth signaling. Calorie restriction is better than intermittent fasting at slowing cancer in mice. Methionine restriction, triggering just one of the nutrient sensing pathways, improves cognitive function in mice. It also improves the microenvironment of the aging brain. Calorie restriction slows renal artery aging. It also improves stem cell function.

An intriguing question: how much of the benefit of a healthy, non-restricted diet is due to the effects of natural calorie restriction mimetic compounds? This could be answered by suitable studies, but that work has yet to be done. In general, calorie restriction mimetic compounds assessed to date compare poorly to the practice of calorie restriction.

Parabiosis and Plasma Dilution

Plasma dilution emerged from parabiosis studies, is being tested in formal and informal trials, and there is some reason to think that it may be worth persuing as a modestly effective way to reduce the impact of aging on inflammatory signaling and other aspects of metabolism. That said, there is evidence to suggest that it isn't the dilution, but rather the albumin that must be provided when blood is diluted. Meanwhile, work on parabiosis itself continues apace, as does work on transfusion based therapies. Researchers have found that transfusions from fit mice to sedentary mice produce benefits to health, in large part mediated by clusterin levels, while serum from young mice improves muscle regeneration in old mice.

Self Experimentation

This year, I published some results from a self-experiment with flagellin immunization to adjust the gut microbiome, and a protocol for running a self-experiment with Khavinson peptides for thymic regrowth. In other news, a paper was recently published on a self-experiment with a growth hormone releasing hormone gene therapy; adventurous and risky, given the side-effects of upregulating growth hormone. It makes for an interest read, given that reducing growth hormone is the common strategy to slow aging and extend life in animal studies.

Short Essays

I write short essay posts here at Fight Aging! less often than I used to; the pressures of time loom large. Here are a few from the past year, however.

• Request for Startups in the Rejuvenation Biotechnology Space, 2021 Edition
• In the Best of Plausible Futures, We Will All Be Occasional Cancer Patients
• Wanted: A Non-Profit to Run as Many Low-Cost Trials of Promising Treatments for Aging as Possible

Odds and Ends

As ever, some items resist easy categorization, but are nonetheless interesting enough to mention. There is prehaps less agreement on a definition of aging than one might think. The children of the 21st century will largely live to be 100 or more if present longevity trends continue, despite the fact that 7.2% of the world's deaths can be attributed to the spread of sedentary lifestyles, and little further gain in human life span is possible via environmental improvement. Yet we should remember that 95% of present centenarians are frail: rejuvenation therapies are much needed. The correlation between wealth and longevity likely does not have cultural or genetic causes.

Radiation hormesis continues to be a topic of interest. Does gum disease speed other aspects of aging via inflammation, as thought, or by oxidative stress, as recently proposed? Historical gains in life expectancy were not just a matter of reduced child mortality, but occurred at all ages. Only a subset of cells in visceral fat are responsible for the harms that it causes to health and metabolism. Age-related vision impairment correlates with all cause mortality in later life. There is a growing portfolio of projects targeting myostatin as a basis for muscle growth. That fullerenes might extend life in mammals has quite comprehensively failed to replicate, as many of us expected would be the case. Some researchers are working on a gene therapy platform specifically for skin rejuvenation. The Hallmarks of Aging are now so ubiquitous in the literature that it is possible to find people willing to critique them rather than just cite them.

ENH1 inhibition allows scarless healing of skin injuries in mice. Flies raised in a germ-free environment have some aspects of aging slowed. Disruption of elastin structures in skin is a big problem, as there is no good approach queued up at an advanced stage of research. It will likely require carefully programmed cells in order to produce the right structures for youthful function. Telomerase and follistatin gene therapies extend life in mice. Most small molecules shown to slow aging change the expression of extracellular matrix genes; is there anything to be learned from this? VEFG gene therapy slows the loss of capillary density and extends life in mice, which is interesting given that one might expect this to produce damaged vessels, as that is what happens in wet macular degeneration in the retina. Ribosomal improvements lower errors in protein synthesis and modestly extend life in short-lived species.

There is continued progress towards reversible cryopreservation of organs, and on balance cryopreservation has a bright future - the question is how long it will take for that future to arrive.

While it is worth remembering that the demographic data on aging at very advanced ages is shaky at best, any number of novel views and models of aging are being put forward these day: the role of rate-limiting processes; a proposed staging system for aging in the clinic; aging as an emergent phenomenon; borrowing particle physics concepts to model aging; the tumor suppressor theory of aging; the adaptive-hitchhike model of the evolution of long-lived species; aging as a consequence of the colonization of land; a tripartite view of aging; the evolutionary layering of the hallmarks of aging; that compression of morbidity is in part the result of a failure to adequately treat the oldest people; the importance of the exponential mortality curve and what it tells us about aging; half of the gains in longevity since the 1960s are the result of technological progress rather than public health measures such as suppression of smoking; the expectation that the upward trend in life expectancy will increase in the future. Is thinking of aging as a contagious process in the body a good model for the way in which failing systems interact? Lastly, the hyperfunction theory of aging remains an at times confusing model, in need of clarification from those who argue for it.

Last Thoughts

People sometimes ask me why I am enthused by senolytics, and very bullish on accelerating the path to further trials and widespread use of the existing senolytic treatments like the dasatinib and quercetin combination. Just take a look at the year of references earlier in this post, linking senescent cells to pathology and their clearance to reversal of that pathology, dozens of papers and studies that I just happened to notice in passing this year. Or look at a similar wall of links to promising results from the end of last year. They are by no means comprehesive lists, only the work that caught my eye. The clearance of senescent cells produces results in animal studies that are far and away superior to any other approach tried to date when it comes to the rapid reversal of age-related disease.

More research into aging and the gut microbiome is taking place these days. A greater investment into this line of research will, as illustrated here, likely lead to a greater knowledge of the mechanisms underlying the known correlations between diet and age-related conditions. That red meat consumption increases cardiovascular risk is quite well established from epidemiological data, and here researchers outline their view of why this happens. One might contrast this with the present consensus, which is that red meat consumption increases lipid levels in the bloodstream, thereby accelerating atherosclerosis and consequent cardiovascular mortality.

In a previous series of studies, researchers found that a byproduct that forms when gut bacteria digest certain nutrients abundant in red meat and other animal products - called TMAO (trimethylamine N-oxide) - increases the risk of heart disease and stroke. The latest findings offer a more comprehensive understanding of the two-step process by which gut microbes convert the nutrient carnitine into TMAO, an atherosclerosis- and blood clot-promoting molecule, following the ingestion of a red meat-rich diet.

Dietary carnitine is converted into TMAO in the gut through a two-step, two microbe process. An intermediary metabolite in this process is a molecule called γBB (gamma-butyrobetaine). Multiple gut microbes can convert dietary carnitine to γBB, but very few can transform the molecule to TMA, the precursor to TMAO. "In omnivores, Emergencia timonensis is the primary human gut microbe involved in the transformation of γBB to TMA/TMAO. Conversely, long-term vegetarians and vegans have very low levels of this microbe in their gut and therefore have minimal to no capacity to convert carnitine into TMAO."

The researchers studied the relationship between fasting plasma γBB levels and disease outcomes using samples and clinical data collected from nearly 3,000 patients. Higher γBB levels were associated with cardiovascular disease and major adverse events including death, non-fatal heart attack or stroke. To understand the mechanistic link between γBB and the observed outcomes in patients, the researchers studied fecal samples collected from mice and patients, as well as preclinical models of arterial injury. They found that introducing E. timonensis completes the transformation of carnitine to TMAO, elevates TMAO levels, and enhances blot clot potential.

Link: https://www.eurekalert.org/news-releases/938807

Myelin sheathing of the axons connecting neurons is essential to the correct function of the nervous system. It is maintained by oligodendrocyte cells, but as noted in this open access paper, the maintenance of myelin is disrupted by the growing inflammation that accompanies aging. In the brain, microglia are innate immune cells that are responsible for a great deal of this inflammation. Some become senescent while others are overactive, made aggressive and inflammatory by the presence of damage and molecular waste in brain tissue. Removing senescent cells in the brain is a promising strategy to reduce the scope of age-related neuroinflammation, but other approaches will be needed as well to reduce inflammatory activity to youthful levels.

Extensive brain atrophy is a characteristic manifestation of aged brain. White matter degeneration is accompanied by encephalatrophy, leading to irreversible neurological and cognitive impairments. Remyelination is a natural protective and regenerative process that will be initiated in response to the degeneration of white matter. It is a complex process involving oligodendrocyte precursor cell (OPC) activation, migration, differentiation, and maturation to be oligodendrocytes (OLGs). Accumulating evidence indicates that remyelination is disturbed in the aged brain. However, a clear understanding of the effect of brain aging on the process of remyelination is still lacking.

Brain aging heightened the neuroinflammatory profile of the cerebral microenvironment, which activated microglia by attributing it to aging-related changes in remyelination. Previous studies have reported that activated microglia secrete a heterogeneity array of signaling molecules, including nitric oxide, reactive oxygen species, Il-6, Il-1β, and tumor necrosis factor (TNF), contributing to myelin damage and hindering proliferation or differentiation of OPCs. However, other studies indicated that activated microglia could promote OLG survival or OPC differentiation by releasing several regenerative factors including Igf-1, Igf-2, galectin-3, activin-A, and Il-1β, and clearing myelin debris.

These diverse results may be driven by the heterogeneous subpopulation of microglia, OLGs, and OPCs. Specific subgroups of OLGs and OPCs in different states may respond inconsistently to the stimulus of activated microglia. In addition, our previous study revealed that there were six subgroups of microglia with divergent functions in aged brain. A unique type of highly activated microglia was observed in aged mice only, with functional implications in immuno-inflammatory response. It remains poorly understood how this specific age-related subgroup of microglia effect on remyelination in aged brain. The exact mechanism of aged microglia in regulation of distinct subgroups of OLGs and OPCs needs to be determined.

In the present study, we aimed to explore the subclusters of OLGs and OPCs by analyzing the single-cell RNA sequence (scRNAseq) data of both young and aged brains. Oligodendrocytes were observed to up-regulate several senescence associated genes in aged brain. Four clusters of oligodendrocyte precursor cells (OPCs) were identified in both young and aged brains. The number of those OPCs in basal state was significantly increased, while the OPCs in the procedure of differentiation were immensely decreased in aged brain. Furthermore, it was identified that activated microglia in the aged brain released inflammatory factors to suppress OPC differentiation. Stat1 might be a potential target to transform senescent microglia into tissue repair type to promote oligodendrocyte generation.

Link: https://doi.org/10.2147/JIR.S338242

Might it be possible to develop a vaccine that works on every strain of influenza, rather than going through a seasonal exercise of vaccination every year? Or at least many strains, rather than just a few? In today's research materials, scientists discuss a possible approach, identifying a novel part of the influenza virus to target, a part of the viral structure that may mutate less readily than the usual vaccine targets. Viruses mutate aggressively when they infect large population, a challenge to both vaccination and natural immunity. The immune system recognizes small parts of a virus, epitopes, and the epitopes most readily recognized are those that mutate to form new strains. This is why we are presently stuck with (a) the yearly death toll inflicted by influenza variants, and (b) the small chance of a much worse variant showing up at some point to produce an outcome to rival the 1918 pandemic.

The burden of infectious disease falls most heavily on the old. An age-damaged immune system responds poorly to many types of vaccination, and is in any case far less capable of mounting a defense against pathogens of all varieties, even given vaccination. Vaccination clearly helps in the case of influenza, but old people are remain vulnerable and exhibit the highest mortality as a result of infection. Arguably far greater effort in research and development should be directed towards the rejuvenation of the immune system rather than better vaccines: regrowing the thymus; regeneration of lymph nodes; restoring youthful hematopoietic function; and clearing damaged and misconfigured immune cells.

No more annual flu shot? Researchers find new target for universal influenza vaccine

In a typical year, influenza affects more than 20 million people in the United States and leads to more than 20,000 deaths. Vaccines against influenza typically coax the immune system to generate antibodies that recognize the head of hemagglutinin (HA), a protein that extends outward from the surface of the flu virus. The head is the most accessible regions of HA, making it a good target for the immune system; unfortunately, it is also one of the most variable. From year to year, the head of HA often mutates, necessitating new vaccines.

Researchers have designed experimental influenza vaccines to be more universal, spurring the body to create antibodies against the less-variable stalk region of HA. In the new study, a collaborative team of scientists characterized 358 different antibodies present in the blood of people who had either been given a seasonal influenza vaccine, were in a phase I trial for an experimental, universal influenza vaccine, or had been naturally infected with influenza. Many of the antibodies present in the blood of participants were antibodies already known to recognize either the HA head or stalk. But a collection of new antibodies stood out; the antibodies bound to the very bottom of the stalk, near where each HA molecule is attached to the membrane of the flu virion.

Researchers named this section of HA the anchor, and began studying it further. In all, the scientists identified 50 different antibodies to the HA anchor, from a total of 21 individuals. The antibodies, they discovered, recognized a variety of H1 influenza viruses, which account for many seasonal flu strains. Some of the antibodies were also able to recognize pandemic H2 and H5 strains of influenza in lab tests. And in mice, the antibodies successfully protected against infection by three different H1 influenza viruses.

Broadly neutralizing antibodies target a hemagglutinin anchor epitope

Broadly neutralizing antibodies (bnAbs) targeting epitopes of the influenza virus hemagglutinin (HA) have the potential to provide near universal protection against influenza virus infection. However, viral mutants that escape bnAbs have been reported. The identification of bnAb classes that can neutralize viral escape mutants is critical for universal influenza virus vaccine design. Here, we report a distinct class of bnAbs targeting a discrete membrane-proximal anchor epitope of the HA stalk domain. Anchor epitope-targeting antibodies are broadly neutralizing across H1 viruses and can cross-react with pandemic-threat H2 and H5 viruses. To maximize protection against seasonal and pandemic influenza viruses, vaccines should aim to boost this previously untapped source of bnAbs that are widespread in humans.

Researchers here discuss some of the details of the disruption of muscle metabolism caused by inflammation in aging. With advancing age, the immune system becomes ever more overactive and dysfunctional, reacting to signs of cellular damage and the pro-inflammatory signals of senescent cells. This immune activity is harmful to tissue function throughout the body. In the case of muscle tissue it speeds the loss of muscle mass and strength that occurs with age, contributing to sarcopenia and frailty.

Aging is associated with the development of chronic low-grade systemic inflammation (LGSI) characterized by increased circulating levels of proinflammatory cytokines and acute phase proteins such as C-reactive protein (CRP). Collective evidence suggests that elevated levels of inflammatory mediators such as CRP, interleukin-6 (IL-6), and tumor necrosis factor α (TNF-α) are correlated with deteriorated skeletal muscle mass and function, though the molecular footprint of this observation in the aged human skeletal muscle remains obscure.

Based on animal models showing impaired protein synthesis and enhanced degradation in response to LGSI, we compared here the response of proteolysis- and protein synthesis-related signaling proteins as well as the satellite cell and amino acid transporter protein content between healthy older adults with increased versus physiological blood hs-CRP levels in the fasted (basal) state and after an anabolic stimulus comprised of acute resistance exercise (RE) and protein feeding.

Our main findings indicate that older adults with increased hs-CRP levels demonstrate (i) increased proteasome activity, accompanied by increased protein carbonylation and IKKα/β phosphorylation; (ii) reduced Pax7+ satellite cells; (iii) increased insulin resistance, at the basal state; and (iv) impaired S6 ribosomal protein phosphorylation accompanied by hyperinsulinemia following an acute RE bout combined with protein ingestion. Collectively, these data provide support to the concept that age-related chronic LGSI may upregulate proteasome activity via induction of the NF-κB signaling and protein oxidation and impair the insulin-dependent anabolic potential of human skeletal muscle.

Link: https://doi.org/10.1155/2021/8376915

The authors of this open access paper take an interesting position on the use of lifestyle choices to slow aging. In their view the most important outcome is an increase in the efficiency of autophagy, and since we know very little about the thresholds required to stimulate autophagy effectively, we in fact know very little about how to make optimal lifestyle choices. Autophagy is the name given to the collection of cellular maintenance processes responsible for removing damaged proteins and structures in the cell, recycling them into raw materials for other uses. Research into the biochemistry of the beneficial calorie restriction response suggests that upregulation of autophagy is required for improved health and extended lifespan. Additionally, improved autophagy is a feature of many of the interventions that slow aging in laboratory species.

This narrative review highlights the studies that explain regular physical exercise and sleep patterns, as well as fasting, and autophagy as a strategy for healthy longevity and well-being. Currently, any of these methods have been used for achieving healthy longevity and well-being within different stage of life from childhood to old-age; however, focusing on combination of all four methods instead of using just one should be the primary aim in the process of reaching healthy longevity and well-being in full capacity. Despite all the advances that have been made to create adequate physical exercise programs, sleep patterns, or nutritional protocols, the relation between different types of fasting, nutritional supplementation and regular physical exercise and sleep patterns have not yet been satisfactorily resolved to cause the best effects of autophagy and, therefore, healthy longevity and well-being.

Previous research gave some guides how to create adequate protocols to reach the best effects of autophagy, but no studies answered the most important questions how to recognize the autophagy threshold and how to use various factors such as fasting and calorie restriction as well as regular physical activity and regular sleeping to stimulate autophagy and decrease the autophagy threshold. In this way, since there are no previous studies, the first future study should create a theory of autophagy threshold, while the rest of future studies should be clinical trials that would confirm independent and joint positive effects of regular physical exercises and sleep patterns, as well as fasting and autophagy on healthy longevity and well-being.

Link: https://doi.org/10.3389/fpsyg.2021.803421

Today's open access paper discusses recent data on age-related changes in brain structure, assessed in older people with varying degrees of physical fitness, though all were described as inactive. Brain atrophy is characteristic of aging; loss of volume proceeds steadily year after year in the latter half of life, accompanied by chances in structure and distribution of tissues. This is one part of the processes that lead to loss of cognitive function and dementia. It is known that physical fitness, and the exercise needed to maintain that fitness, slows this progression.

Many different mechanisms are likely involved in the ways in which fitness can slow the aging of the brain. For example, exercise boosts BDNF levels, which encourage neurogenesis, the production of new neurons in the brain. Further, both exercise and the state of fitness improve blood flow to the brain, in the short term and the long term. Brain tissue requires a great deal of energy to perform its functions, and a flow of nutrients and oxygen is essential. That exercise can improve cognitive function very quickly, on the same timeframe as increased cerebral blood flow, suggests that the brain has evolved to operate at the upper limit of its energy supply. Any loss from the peak will affect tissue over the long term.

Investigating impact of cardiorespiratory fitness in reducing brain tissue loss caused by ageing

Late adulthood is marked by a host of physical changes and brain atrophy is one of the most ubiquitous. Specifically, after the age of forty, brain volume declines at a rate of about 5% per decade. Furthermore, ageing-related shifts in brain morphology are associated with concomitant declines in cognitive performance. As our population ages, there is paramount interest in strategies to potentially mitigate the brain tissue loss that occurs with ageing. In recent research, cardiorespiratory fitness (CRF) has been described to be neuroprotective in older adults. As CRF can be influenced through exercise intervention, there may be future potential for these therapies in mitigating neurodegeneration.

However, the influence of CRF on brain tissue has not been fully characterized quantitatively. Tissue atrophies in the ageing brain non-uniformly across multiple regions. Multiple studies have demonstrated that both ageing and decreased CRF are associated with non-uniform declines. Yet, prior studies investigating associations with CRF have not characterized differential atrophy and degeneration across the brain. First, conventional statistical methods comparing regional volumes and voxelwise metrics are insufficiently sensitive to the spatial interdependence in brain tissue, and its nonlinearity. Indeed, regional volumes have led to varying reports of the degree to which tissue shifts dependent on age and those dependent on CRF overlap. In contrast, new techniques that measure spatial variation in brain tissue as mathematical distributions can directly measure these diffuse, non-linear processes. Second, while regional volumes and voxelwise metrics are basic statistical descriptors, they do not correspond to any biophysical properties of brain tissue.

In recent work, the authors developed an automated approach to discover discriminant phenotypic patterns from brain images by directly measuring the spatial tissue distribution. This approach enabled biophysical properties of the brain to be modelled as mass transport. The technique is called 3D transport-based morphometry (TBM). This paper applies the novel TBM approach to extract the perturbations in brain phenotype statistically explainable by CRF. The goal of this research is to discover and visualize the shifts in brain tissue distribution that are most strongly associated with CRF in an automated manner using the TBM technique. Furthermore, this study aims to determine the degree to which the pattern of tissue distribution with higher CRF overlaps with the distribution of ageing-related losses.

In this study of 172 inactive older adults aged 58-81 (66.5 ± 5.7) years, cardiorespiratory fitness was determined by VO2 peak (ml/kg/min) during graded exercise and brain morphology was assessed through structural magnetic resonance imaging. After correcting for covariates including age (in the fitness model), gender, and level of education, we compared dependent tissue shifts with age to those due to VO2 peak. We found a significant association between cardiorespiratory fitness and brain tissue distribution. A strong statistical correlation was found between brain tissue changes related to ageing and those associated with lower cardiorespiratory fitness. In both cases, frontotemporal regions shifted the most while basal ganglia shifted the least. Our results highlight the importance of cardiorespiratory fitness in maintaining brain health later in life.

A sizable amount of venture capital has emerged to support the longevity industry over the last year. The Korify Capital fund noted here is the latest of a series of longevity-focused funds to be announced. Whether or not this fund will invest in a sizable number of useful efforts remains to be seen, though their first investment is on the better end of the small molecule discovery space. There is all too much investment in the development of supplements, calorie restriction mimetics, and other line items that may be a part of the longevity industry, and may well produce a return on investment, but which at the end of the day will do little to change the shape and length of a human life span. That is the nature of the beast; even for funds in which the principals are very interested in the outcome of greatly extending the healthy human life span, the limited partners that provide the funding care little for anything other than a safe return on investment. It is their interests that ensure that unambitious, incremental, lower risk projects are pursued to a greater extent than is merited.

Longevity and mental health biotechs take note: Korify Capital is putting together a $100 million venture fund targeting your space and is looking to build a portfolio of 15 to 20 companies across Europe, the U.S. and Israel. The targeted $100 million investment vehicle, which is expected to close around the middle of next year, is the first fund of Korify, the international venture arm of Swiss family office Infinitas Capital. Infinitas is active in multiple areas outside of biotech, notably real estate, but has been tracking advances in aging and mental health research and has decided the time is right to enter the space.

The Korify principals identify COVID-19 as an accelerant, both because it has increased the interest of generalist investors in longevity and because it could spur innovation in the historically moribund mental health sector. With large biopharma companies pulling back from central nervous system research, Korify sees room for smaller biotechs to build on academic progress, creating investment opportunities for the new VC fund. "There's not like a couple of dominant companies that just own the space. Rather, there's a lot of disruption happening at the smaller scale, in smaller biotech companies, that are very lucrative to invest in and very interesting from an investor's perspective."

Korify plans to invest in 15 to 20 such biotechs, with a focus on later-stage platform companies. That focus is evident in Korify's decision to make Cambrian Biopharma its first investment. Cambrian, which exited stealth in February, has disclosed $160 million in financing this year to advance a pipeline of 14 drug candidates designed to target biological drivers of aging. "We like their approach of being very diversified, with multiple shots on multiple targets. They also are very aware of the current regulatory systems that are in place. We don't really have any solid longevity biomarkers, so their strategy is set up in a way that they can get there with the current FDA framework."

Link: https://www.fiercebiotech.com/biotech/aiming-to-make-70-new-50-korify-rolls-out-100m-longevity-and-mental-health-venture-fund

Age-related frailty is characterized by physical weakness and chronic inflammation, but this is the visible tip of the iceberg. Chronic inflammation accelerates much of the dysfunction of aging. As researchers note here, this includes neurodegenerative processes that lead to dementia. Reducing frailty in the population will therefore likely lead to a reduction in dementia incidence. The most plausibly useful lines of work on frailty therapies at present focus on ways to reduce the chronic inflammation of aging, from elimination of senescent cells and their pro-inflammatory secretions to ways to selectively suppress inflammatory signaling.

Researchers worked with data from more than 196,000 adults aged over 60 in the UK Biobank. They calculated participants' genetic risk and used a previously-developed score for frailty, which reflects the accumulation of age-related symptoms, signs, disabilities and diseases. They analysed this alongside a score on healthy lifestyle behaviours, and who went on to develop dementia. "We're seeing increasing evidence that taking meaningful action during life can significantly reduce dementia risk. Our research is a major step forward in understanding how reducing frailty could help to dramatically improve a person's chances of avoiding dementia, regardless of their genetic predisposition to the condition. This is exciting because we believe that some of the underlying causes of frailty are in themselves preventable. In our study, this looked to be possible partly through engaging in healthy lifestyle behaviours."

Over the 10-year UK Biobank study period, dementia was detected via hospital admission records in 1,762 of the participants - and these people were much more likely to have a high degree of frailty before their diagnosis compared with those who did not develop dementia. The importance of preventing or reducing frailty was highlighted when the researchers examined the impact of genetic risk in people with different degrees of frailty. Genetic risk factors exerted their expected effect on risk of dementia in study participants who were healthy, but genes were progressively less important in study participants who were the most frail. In those frail study participants, risk of dementia was high regardless of their genes.

Compared with study participants with a low degree of frailty, risk of dementia was more than 2.5 times higher (268 per cent) among study participants who had a high degree of frailty - even after controlling for numerous genetic determinants of dementia. Study participants who reported more engagement in healthy lifestyle behaviours were less likely to develop dementia, partly because they had a lower degree of frailty.

Link: https://www.exeter.ac.uk/news/homepage/title_890854_en.html

In today's open access paper, the authors report on a successful effort to restore youthful behavior in neural stem cell populations in aged mice. A lentiviral gene therapy to upregulate plagl2 and downregulate dyrk1a resulted in increased production of new neurons, to a pace normally seen in young animals, and cognitive function improved as a consequence. Like all stem cell populations, the activity of neural stem cells declines with age. A supply of new neurons that will integrate with existing neural circuits is necessary to maintain the function of the brain, particularly learning and recovery from the sort of small-scale damage that is inflicted on brain tissue over time, such as through the rupture of capillaries.

Thus the research community is very interested in finding ways to safely increase neurogenesis, the production of new neurons, in the aging brain. Beyond functional gains and resilience, it is hoped that increased neurogenesis can help in the recovery from serious brain injury, such as that caused by stroke. Another approach to this challenge is the reprogramming of supporting glial cells in the brain, turning them into neurons, though recent work in that part of the field has proven disappointing. It remains to be seen as to which of the various approaches will reach the clinic and use in human patients, and how long it will take to achieve that goal.

Functional rejuvenation of aged neural stem cells by Plagl2 and anti-Dyrk1a activity

Aged neural stem cells (NSCs) are mostly dormant, and even when they are activated, they primarily produce astrocytes. Thus, aged NSCs lose their proliferative and neurogenic potential, leading to the cessation of neurogenesis. In this study, we showed that the iPaD (inducing Plagl2 and anti-Dyrk1a) lentivirus substantially rejuvenated the proliferative and neurogenic potential of NSCs in the aged brain. Clonal analysis by a sparse labeling approach as well as transcriptome analysis indicated that iPaD can rejuvenate aged NSCs (19-21 mo of age) to a level comparable with those at 1 or 2 months of age and successfully improved cognition of aged mice.

Once rejuvenated and activated by iPaD, aged dormant NSCs can generate, on average, 4.9 neurons but very few astrocytes in 3-week tracing. Furthermore, these activated NSCs were maintained for as long as 3 months in the aged brain, suggesting that active neurogenesis continues for an extended period of time after iPaD treatment. Nevertheless, iPaD-activated neurogenesis gradually declined. Furthermore, clonal analyses showed that 78.1% (9-month-old) and 81.7% (19-month-old) of iPaD-activated clones maintained RGL cells 4 week after activation, suggesting that ∼20% of activated NSCs are exhausted during this period. However, it is unknown whether this exhaustion is due to limitation of iPaD or loss of iPaD activity, and further analyses are requited to answer this question.

A recent study showed that resting NSCs, those once proliferated but returned to quiescence, are the major origin of active NSCs in the aged brain. This population comprises only 3%-5% of the total NSCs, while the other major population is dormant NSCs, which have never proliferated. Because the iPaD is able to activate 70%-80% of NSCs in the aged brain, it is likely that it mostly targets dormant NSCs, raising the possibility that the higher the infection efficiency of the iPaD virus, the more NSCs are activated to produce new neurons.

During aging, the gene expression and accessible chromatin landscapes change dynamically in NSCs. Transcriptome analysis showed that there are eight clusters of genes showing different expression patterns. Among them, clusters 2, 3, and 6 are of particular interest: In clusters 2 and 3, gene expression is down-regulated in aged NSCs compared with embryonic NSCs but up-regulated by iPaD, while in cluster 6, gene expression is up-regulated in aged NSCs but repressed by iPaD. Genes involved in cell proliferation are enriched in clusters 2 and 3, while genes involved in aging are enriched in cluster 6. In addition, chromatin-modifying genes are also enriched in clusters 2 and 3. These results suggest that iPaD can rejuvenate aged NSCs by up-regulating embryonic-high genes and repressing age-associated genes via modulation of chromatin accessibility. The detailed mechanism by which iPaD differentially regulates the chromatin structures remains to be analyzed.

Here, researchers discuss the role of mitochondrial quality control in sarcopenia. Sarcopenia is the name given to the later stages of the loss of muscle mass and strength characteristic of aging. Muscle is an energy-hungry tissue, and the age-related decline in mitochondrial activity is therefore likely a contributing factor in this progressive loss of function. Mitochondria are the power plants of the cell, responsible for generating the ATP molecules that store chemical energy needed to power cellular processes. Every cell contains a herd of hundreds of mitochondria, which are removed and recycled when they become worn or broken by the quality control process of mitophagy. Unfortunately mitophagy becomes less efficient with age, for reasons yet to be fully explored, but which are likely connected to changes in mitochondrial dynamics.

Mitochondria have strong impacts on the maintenance of cellular viability, including ATP production, oxidative phosphorylation (OXPHOX) homeostasis, calcium buffering, and apoptosis. Therefore, healthy quality control is crucial for the preservation of intracellular homeostasis of muscle cells with aging. The mitochondrial quality control (MQC) includes mitochondrial proteostasis, biogenesis, dynamics and autophagy. Orchestrated mechanisms contain several cellular factors and signaling pathways to ensure the integrity of mitochondria. Mitochondrial biogenesis is responsible for the generation of new mitochondria through the synergistic interaction of the nuclear and mitochondrial genes; mitochondrial dynamics is achieved by continual transformation between fusion and fission to eliminate the accumulation of unhealthy mitochondria; mitochondrial autophagy (mitophagy) is a process of selective removal of the hypofunctional and damaged mitochondria. Adverse alternations in the quality control mechanisms may lead to mitochondrial dysfunction, which can further contribute to muscle wasting and even sarcopenia.

The incidence rate of sarcopenia in the mid-life and elderly population varies according to different age, operational definitions, regions and ethnicities. A number of epidemiological studies have shown that the prevalence of sarcopenia gradually increases with age. It is conservatively estimated that 5%-13% of elderly individuals aged 60-70 years are suffering from sarcopenia. The numbers increase to 11%-50% among those aged 80 or above. Since the number and proportion of the global aging population is rapidly growing, the socio-economic burden of individuals and society may increase due to higher prevalence of sarcopenia. Sarcopenia was formally recognized as a disease in 2016, which attracted additional attention for this degenerative disease. Physical activity is recommended as the primary treatment for sarcopenia to improve muscle strength and mass, although no specific drugs have been developed with therapeutic effects in sarcopenia. In this review, we summarize the potential mechanisms of mitochondrial dysfunction with an emphasis on promising therapeutic interventions to prevent and ameliorate sarcopenia during aging.

Link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8612607/

Researchers here discuss potential approaches to protect the heart from scarring and loss of function following a heart attack: senolytics to clear senescent cells; restoration of mitochondrial function; induction of telomerase activity; and inhibition of inflammatory signaling. Removing the cause of heart attacks by finding a cure for atherosclerosis, a way to reverse the fatty lesions that narrow blood vessels and weaken blood vessel walls, would be preferable to finding better ways to fixing the damage after the fact. But there will always be some call for ways to improve the regenerative capacity of an injured heart.

The hallmarks of myocardial aging may account for the reduced tolerance against myocardial ischemia/reperfusion injury in preclinical studies and thus, understanding mechanisms of myocardial aging may enable the development of new and effective therapies to reduce cardiac damage after myocardial infarction (MI) in the context of aging.

Senescent cells increase in aged tissues, which has been associated with the progression of age-related diseases. In this context, senescence markers are augmented in aged cardiomyocytes, which has been linked to higher risk of cardiovascular diseases. Senolytics are agents that can selectively target pro-survival proteins of senescent cells, inducing cell death. Regarding the heart, there are three major senolytics that have been widely studied in vivo and in vitro; Dasatinib, Quercetin, and Navitoclax. These senolytics have been shown to improve vascular function. Importantly, a study showed that oral administration of navitoclax to aged mice before in vivo myocardial infarction reduced mortality, as well as age-related myocardial remodeling and improved left ventricular function.

The mitochondria have been identified as an important target to reduce myocardial ischemia/reperfusion injury in the aged heart. The mitochondria in aging cardiomyocytes shows elevated ROS production, higher fragmentation and reduced biogenesis, thus producing mitochondrial dysfunction, which can contribute to the increased susceptibility of the aged heart to ischemic injury. Therefore, therapies targeting the mitochondria are an attractive area of research in cardioprotection.

During MI, a pathogen/antigen-independent inflammatory response, known as sterile inflammation, takes place. Due to the rupture in the cellular structure that occurs during MI, damage-associated molecular patterns (DAMPS) mediators are released and are recognized by pattern recognition receptors (PRRs), which in turn mediate the initiation of the inflammatory response. NLPR3 inflammasome is a multiprotein complex formed by the activation of PRRs, thereby increasing the production and release of proinflammatory cytokines via activation of caspase-1. Interestingly, pharmacological inhibition of caspase-1 reduced the infarct size in isolated rat hearts. Also, caspase-1 inhibition was also shown to provide additional protection when combined with remote ischemic preconditioning in rats subjected to in vivo myocardial infarction.

Telomeres are repeated hexanucleotide sequences at the end of eukaryotic chromosomes. Their presence is associated with DNA protection during cell division. Division of the cell as well as oxidative stress shortens these structures, leading the cell to a senescent state or apoptosis. Telomere length has been associated with coronary artery disease and therefore, it has been proposed as a biomarker for cardiovascular diseases. Telomerase is a key regulator of telomere length and integrity and as such, has gained attention for its potential benefits in age-related cardiovascular diseases. For instance, absence of telomerase has been associated with increased susceptibility to ischemic injury. By the same token, overexpression of telomerase can confer cardioprotection in mice hearts.

Link: https://doi.org/10.3389/fcvm.2021.770421

Senescent cells accumulate with age. Researchers here provide evidence for yet another age-related decline to be added to the long list of issues in which this accumulation of senescent cells is an important contributing cause. In this case, the problem is the loss of regenerative capacity in muscle tissue that occurs with age. Can this be due to loss of stem cell activity? Past research has indicated that muscle stem cell populations are largely intact in old individuals, but increasingly quiescent and inactive. Removing senescent cells removes some portion of the inflammatory signaling characteristic of old age, and this signaling may be influential in the loss of stem cell function in many tissue types.

Equally, the loss of regenerative capacity may have more to do with changes in the timing of clearance of senescent cells during the process of tissue regrowth following injury. The immune system becomes less able to rapidly clear senescent cells in later life. There has been some concern that intermittent removal of senescent cells via senolytic treatment would impair wound healing, given that the short-term presence of senescent cells is involved in the intricate coordination of different cell types that is needed for regeneration. As this study shows, the benefits of removing senescent cells in this way outweigh the downsides, at least in the old mice. In young mice, removal of senescent cells is disruptive to wound healing.

The evidence here suggests that issues in aged muscle regeneration are caused in part by (a) the inability of the immune system to rapidly clear the senescent cells created during the healing process, and (b) senescent immune cells that enter the injured area. The aged environment may be forcing immune cells into senescence rather than allowing them to perform the usual pro-regenerative activities.

Deletion of SA β-Gal+ cells using senolytics improves muscle regeneration in old mice

Systemic deletion of senescent cells leads to robust improvements in cognitive, cardiovascular, and whole-body metabolism, but their role in tissue reparative processes is incompletely understood. We hypothesized that senolytic drugs would enhance regeneration in aged skeletal muscle. Young (3 months) and old (20 months) male C57Bl/6J mice were administered the senolytics dasatinib (5 mg/kg) and quercetin (50 mg/kg) or vehicle bi-weekly for 4 months. Tibialis anterior (TA) was then injected with 1.2% BaCl2 or PBS 7 days or 28 days prior to euthanization. Senescence-associated β-Galactosidase positive (SA β-Gal+) cell abundance was low in muscle from both young and old mice and increased similarly 7 days following injury in both age groups, with no effect of D+Q. Most SA β-Gal+ cells were also CD11b+ in young and old mice 7 days and 14 days following injury, suggesting they are infiltrating immune cells.

By 14 days, SA β-Gal+/CD11b+ cells from old mice expressed senescence genes, whereas those from young mice expressed higher levels of genes characteristic of anti-inflammatory macrophages. SA β-Gal+ cells remained elevated in old compared to young mice 28 days following injury, which were reduced by D+Q only in the old mice. In D+Q-treated old mice, muscle regenerated following injury to a greater extent compared to vehicle-treated old mice, having larger fiber cross-sectional area after 28 days. Conversely, D+Q blunted regeneration in young mice. In vitro experiments suggested D+Q directly improve myogenic progenitor cell proliferation. Enhanced physical function and improved muscle regeneration demonstrate that senolytics have beneficial effects only in old mice.

Declining stem cell function is undoubtedly an important contribution to degenerative aging and age-related mortality. Tissues require the supply of new somatic cells that is generated by stem cells in order to replace losses, repair damage, and maintain function. Unlike stem cells, somatic cells are limited in the number of times they can divide. Turnover of somatic cell populations is a central aspect of near all multicellular life, and the small populations of tissue-specific stem cells are vital to continued function in an environment in which somatic cells must be periodically replaced. The goal of human rejuvenation will require the restoration of youthful stem cell function, through some combination of replacement, alteration of cell behavior, or repair of damage.

Stem cell exhaustion is the result of multiple types of aging-associated damages and it is one of the phenomena responsible for tissue and organismal aging. Many mammalian tissue-resident stem cells display a substantial decline in replicative function as they mature. The renewal ability of human tissues declines with aging of stem cells altering their capacity to differentiate in different types of cells. Moreover, age-related loss of self-renewal in stem cells leads to a reduction in stem cell number. Nevertheless, it may be possible to generate therapeutic approaches to age-related diseases based on interventions to delay, prevent, or even reverse stem cell aging.

Understanding how stem cells age may help understanding the normal aging process at the organ level, specifically in tissues with continuous regeneration. These processes are influenced by various cell-intrinsic and cell-extrinsic pathways. Indeed, recent discoveries have revealed a complex interaction among cell-intrinsic, environmental, and systemic signals linked to stem cell function loss during aging.

Researchers have worked to understand the main mechanisms with in vitro and in vivo experiments. The principal causes of stem cells aging are accumulation of toxic metabolites, DNA damage, proteostasis, mitochondrial dysfunction, proliferative exhaustion, extracellular signaling, epigenetic remodeling, and loss of quiescence. Many of these aging mechanisms are in common with differentiated cells but stem cell exhaustion, or the quantitative and qualitative loss in stem cell function with time, has a more important impact on tissue aging compared to differentiated cells and has been postulated as one of the aging causes. Adult stem cells perform a critical function in tissue homeostasis by repairing and regenerating tissues throughout life. They maintain practically all tissues and organs, including the forebrain, bone, and muscle, and stem cell exhaustion, defined as a drop in stem cell number and function, is documented in essentially all tissues and organs maintained by adult stem cells. Furthermore, age-related alterations in hematopoietic stem cell differentiation result in fewer adaptive immune cells being produced.

Understanding how stem cell aging affects distant tissues and overall health span is just the tip of the iceberg. This line of research is important because it lays the groundwork for stem cell-based treatments to help people live longer lives. Stem cell rejuvenation may reverse the aging phenotype and the discovery of effective methods for inducing and differentiating pluripotent stem cells for cell replacement therapies could open up new possibilities for treating age-related diseases.

Link: http://dx.doi.org/10.4252/wjsc.v13.i11.1714

Anemia is a lowered level of red blood cells and hemoglobin, leading to a diminished supply of oxygen to tissues and thus degraded function throughout the body. The anemia of aging, like all issues in later life, is a gradual onset, a sliding scale of dysfunction with an arbitrary line in the sand as how low hemoglobin must fall for it to be formally considered a medical condition. There are consequences prior to that point of course, as the study data here illustrates. The relationship between lower hemoglobin levels and higher mortality is linear. It is, however, an open question as to how much of this relates to downstream consequences of lower hemoglobin levels and how much is a case of individuals with a greater burden of molecular damage and dysfunction tending to have lower hemoglobin levels.

An increase in life expectancy has emphasized anemia as a public health concern because of the associated healthcare needs and financial burden it incurs. Anemia is common among older adults with the estimated prevalence of 17% among individuals aged ≥65 years. A large cohort study has found that the prevalence of anemia increased with age from 4 to 6% in those aged 65-69 years to 13-14% in those aged ≥85 years. Anemia has been associated with a range of adverse events including falls, cognitive deficits, hospitalization, and mortality among older adults.

Anemia has been defined as hemoglobin (HB) concentrations of less than 12.0 g/dL and 13.0 g/dL in women and men, respectively. Some studies have reported that relatively lower HB concentrations were predictors of increased risk of mortality, which were due to decreased oxygen carrying capacity causing left ventricular hypertrophy and ischemia. More recently, several prospective cohort studies have indicated that a non-linear association exists between HB concentrations and all-cause mortality. Anemia may be prevalent in the general population, particularly in older adults. The effect of HB concentrations is associated with infection, autoimmune disease, and chronic kidney disease. In the current study, we aimed to evaluate the relationship between HB concentrations and all-cause mortality among 1,785 older adults aged ≥65 years form Chinese longevity regions, using community-based cohort data from the Chinese Longitudinal Healthy Longevity Survey (CLHLS).

In total, 999 deaths occurred during a median follow-up of 5.4 years from 2011 to 2017. Analysis found no non-linear association between HB concentrations and all-cause mortality after a full adjustment for covariates among the older adults form longevity regions. The risk for all-cause mortality was significantly higher in the groups with HB concentration of less than 11.0 g/dL (hazard ratio: 1.37) and 11.0-12.0 g/dL (hazard ratio: 1.25); the risk of all-cause mortality was significantly lower in the groups with HB concentration greater than 14.0 g/dL (hazard ratio: 0.76) compared with the reference group (13.0-13.9 g/dL). This HB concentrations were found to be inversely and linearly associated with all-cause mortality.

Link: https://doi.org/10.3389/fpubh.2021.787935

In today's open access paper, the authors report on their investigation of the effects of nicotinamide mononucleotide (NMN) supplementation on the gut microbiome in mice. The gut microbiome changes with age, exhibiting a loss of helpful populations that produce metabolites necessary to health, and the growth in harmful populations that provoke chronic inflammation. Rejuvenating the aged gut microbiome via fecal microbiota transplantation from a young individual has been shown to improve health and extend life in short-lived species. Thus there is some interest in evaluating the effects on the gut microbiome produced by interventions thought to improve late-life health.

I should say that I think much of the current enthusiasm for vitamin B3 derivatives such as NMN and nicotinamide riboside (NR) is probably misplaced. The clinical evidence from human trials is just not that compelling, and exercise appears to produce better outcomes in NAD metabolism and mitochondrial function. The point of interest to take away from the study here is that there may be both beneficial and harmful changes produced in the gut microbiome by NMN supplementation (and thus likely also by NR, niacin, and similar approaches). It isn't only the helpful microbial populations that are boosted in numbers and diversity by a supply of NMN.

The researchers also looked at telomere length in mice and humans, and found it lengthened by NMN supplementation, but this data is not very interesting. Telomere length is measured in a blood sample, and is thus an assessment of only white blood cells. Average telomere length is a blurred measure of cell replication pace and cell replacement pace; telomeres shorten with each cell division in somatic cells, and newly created somatic cells, the daughters of stem cells, have long telomeres. White blood cells replicate aggressively in response to stress, infection, and similar prompts. Their telomere status isn't necessarily all that representative of the body as a whole, and varies widely on short time frames. Correlations between white blood cell telomere length, health, and aging, only emerge in large populations, and even then the correlations are poor or non-existent in many studies.

The Impacts of Short-Term NMN Supplementation on Serum Metabolism, Fecal Microbiota, and Telomere Length in Pre-Aging Phase

We probed the changes in the fecal microbiota and metabolomes of pre-aging male mice (C57BL/6, age: 16 months) following the oral short-term administration of nicotinamide mononucleotide (NMN). The complex interplay between age and the microbiota is well-described in several studies. The changes in the composition, diversity, and functional characters of the microbiota were observed over time. It was reported that the abundance of Proteobacteria is positively linked with aging. Proteobacteria include pathogenic representatives, such as Enterobacter spp., which may cause infection and disease. In the present study, the reduced abundance of fecal Proteobacteria in the NMN-supplemented mice suggests that NMN might have perturbed certain harmful microbes.

Surprisingly, a widely accepted probiotic strain Akkermansia (Verrucomicrobiota phylum) was lowered in the fecal microbiota of NMN-supplemented mice. In contrast, a previous study has reported that NMN administration enriches the abundance of Akkermansia muciniphila. We conjecture that the observed differences in the outcomes may be attributed to the difference in the age of the mice used in the experiments. We clearly observed that the Akkermansia abundance was negatively correlated to nicotinamide, tryptophan, and indole as well as their derivatives, which might have inhibited its growth.

Nicotinamide mononucleotide increases the abundance of butyric acid-producing Turicibacter which exhibits anti-fatigue activity, implying that NMN administration might reinforce vitality by promoting the growth of Turicibacter. Unexpectedly, in this study, oral NMN administration increased Helicobacter abundance in pre-aging mice. Some Helicobacter spp. are known as pathogenic bacteria that can cause gastric diseases, its enrichment with NMN administration should be deeply and carefully confirmed further.

In addition to these top dominant genera, the correlation analysis demonstrated that Mucispirillum was greatly associated with the altered serum metabolites. Mucispirillum was positively correlated with the metabolites relevant to purine, nicotinate, and nicotinamide metabolism, as well as arginine and proline metabolism. Mucispirillum schaedleri showed a protective effect against Salmonella enterica ser. Typhimurium colitis by interfering with the invasion gene expression. These upregulated metabolites might have beneficial effects on the inhibition of pathogenic adhesion in the gut mucus.

It is not yet fully understood how these metabolites change with the varied microbial composition in response to the NMN supplementation. Further validation of specific metabolite changes corresponding to specific microbial genera coupled with their downstream biological effects will be important to the effects of NMN supplementation on the host.

Sirtuins are connected to the upregulation of cellular stress response mechanisms triggered by, for example, calorie restriction. Given the failure of past attempts to intervene in aging at the point of sirtuin 1, it may be that the influence of sirtuins on the pace of aging simply isn't large enough to be useful. That said, work on other sirtuins, such as sirtuin 6 and to a lesser degree sirtuin 3, have produced somewhat better results in mice. Still, stress response upregulation as a whole is demonstrably far more influential on life span in short-lived species such as mice than it is in long-lived species such as humans. Calorie restriction can extend maximum life span in mice by 40%, but certainly does no such thing in humans. This should tell us that we must look elsewhere for means of extending the healthy human life span by decades.

Sirtuins may counteract organismal aging by altering the pattern of cellular stress response to generate much less disruption of tissue homeostasis. The alteration of cellular stress response pattern by sirtuins comprises (1) inhibition of apoptosis, (2) promoting DNA damage repair instead of apoptosis or induction of cellular senescence, (3) antioxidative action through activation of MnSOD, (4) preventing carcinogenesis through acting as tumor suppressor proteins, (5) inhibition of unnecessary inflammatory response/inflammaging through inactivation of NF-kB, and (6) preventing cellular senescence and senescence-associated secretory phenotype (SASP) through mitochondrial protection and promoting DNA damage repair.

All the effects listed above combined may prevent disruption of tissue homeostasis - directly responsible for organismal aging in vertebrates while being itself a distant derivative of a prolonged, inappropriate pattern of cellular response to accidental damage of the biostructure. The mechanisms discussed in this review describe how exactly sirtuin-dependent modifications of the cellular stress response can slow down aging at the tissue level. Thus, sirtuins, especially SIRT1, SIRT3, and SIRT6, can modify cellular stress response to promote maintenance of tissue homeostasis and thus slow down phenotypic aging at the organismal level.

Link: https://doi.org/10.3389/fphys.2021.724506

Researchers here show that signaling related to inflammatory regulation within a cell, undertaken in response to stress, can induce cellular senescence. Preventing the onset of the senescent state in response to some forms of stress may be beneficial, and indeed may be a part of the way in which therapies such as low dose mTOR inhibition can lower the burden of cellular senescence over time. A blanket prevention of senescence is probably a bad idea, as some cells become senescent for good reasons: they are damaged in ways that can produce cancer, or they are assisting in wound healing, for example. But more discriminating sabotage of pro-senescent mechanisms may help to prevent some of the consequences of an aged tissue environment by reducing the pace at which otherwise viable cells become senescent.

Cellular senescence is a cell state characterized by a proliferative cellular arrest, a secretory phenotype, macromolecular damage, and altered metabolism that can be triggered by several different stress mechanisms. Senescent cells produce and secrete a myriad of soluble and insoluble factors, including cytokines, chemokines, proteases, and growth factors, collectively known as the senescence-associated secretory phenotype (SASP). More recent evidence proposes that different triggers might induce distinctive SASP subsets with concrete functions. Nonetheless, the SASP has started to incite interest as a potential therapeutic target in disease. Therefore, a better understanding of the molecular machinery regulating the SASP is needed.

Pattern recognition receptors (PRRs) of the innate immune system are molecular sensors that are activated by microbial-derived pathogen-associated molecular patterns (PAMPs) or by damage-associated molecular patterns (DAMPs or alarmins) generated endogenously in cells under certain conditions of stress and damage. Emerging data indicate a close relationship between these PRRs and cellular senescence.

We have previously shown that inflammasomes are critical for the SASP. Inflammasomes are multiprotein platforms that induce the proteolytic activity of the inflammatory protease caspase-1, which activates by proteolytic cleavage the proinflammatory cytokines IL-1β and interleukin-18 (IL-18). The canonical inflammasomes are assembled by PRRs. Alternatively, the related inflammatory caspase-4 and caspase-5 (caspase-11 in mice) function as independent PRRs for cytoplasmic microbial lipopolysaccharide (LPS) activating a noncanonical inflammasome.

Because the mechanism of SASP regulation by inflammasomes remains ill-defined, we decided to define the role of these inflammatory caspases in senescence. We show here that caspase-4 activation by cytoplasmic LPS triggers a senescence phenotype. Moreover, we show here that the caspase-4 noncanonical inflammasome contributes critically to the establishment of the SASP and the reinforcement of the cell cycle arrest program during oncogene-induced senescence. In all, we describe a new and critical function for cytoplasmic sensing by the caspase-4 noncanonical inflammasome in cellular senescence.

Link: https://doi.org/10.1038/s41418-021-00917-6

Myelin is an insulator that sheaths the axons forming nervous system connections. It is essential to the correct electrochemical function of the nervous system. Severe conditions such as multiple sclerosis result when myelin is lost, degrading nervous system function to the point of disability and death. In normal aging, myelin is also lost, though to a lesser degree. It is reasonable to think that this contributes to neurodegeneration and cognitive decline, but the only straightforward way to determine the relative importance of demyelination versus the many other mechanisms at work in the aging brain is to fix the problem in isolation and observe the results.

Like all structures in the body, myelin must be constantly maintained by a dedicated hierarchy of specialized cells. In this case, this means oligodendrocytes and their precursors. Significant disruption of this population results in demyelination. There is a good deal of evidence to suggest that oligodendrocytes are negatively affected by mechanisms of aging, such as the growing chronic inflammation provoked by the secretions of senescent cells. The population diminishes in size and undergoes changes in behavior. Thus strategies focused on restoration of oligodendrocyte populations via cell therapy, or at least the restoration of their youthful behavior via suitable delivery of signals, may be a good approach to restoring lost myelin and evaluating contribution of demyelination to cognitive aging.

Replenishing the Aged Brains: Targeting Oligodendrocytes and Myelination?

Age-related neurofunctional decline may negatively impact the daily life for the elderly, and no effective strategies are available so far in the clinic. This present review mainly focuses on myelin degeneration, decreased myelinogenesis during aging and the possible mechanisms. Admittedly, a lot of questions remain unanswered. For instance, are there spatial or temporal differences in the degeneration process in the central nervous system (CNS)? What is the deciding point for one oligodendrocyte (OL) or one myelin segment to initiate degeneration and could we inhibit this bad process through modulating one key factor? Is the newly generated myelin more stable compared to preexisting myelin in the aged brain? If this is the case, we may find some clues about repressing myelin degeneration in the aged. The decreased myelinogenesis during aging is likely a result of arrested differentiation of oligodendroglia precursor cells (OPCs), thus it is plausible that promoting adult OPCs maturation may be a feasible and realistic approach to improve age-related neuronal function decline for the elderly. Meanwhile, rejuvenating subventricular zone (SVZ) stem cells may also help with myelinogenesis ability in the aged. More efforts are needed to further confirm those effects in human.

Moreover, oligodendroglial lineage cells display more behaviors than differentiation and forming new myelin sheaths. For example, OPCs may form synaptic connections with neighboring neurons, and that regulates neuronal signals in the CNS. In addition, the expression of connexin channel proteins in oligodendroglial lineage cells is an intriguing feature and the connexins could function either as hemichannels or gap junctions. The gap junction enables OLs to be connected as a glial network with astrocytes, allowing transportation of small molecules such as calcium and energy metabolites, which may be important for homeostasis of the CNS. Recent studies even showed that OPCs could exert immunomodulatory functions, which are particularly relevant in the context of neurodegeneration and demyelinating diseases. Besides, OLs are found to be heterogenetic in the mouse juvenile and adult CNS, the response of different subtypes to aging remains unknown. It is not clear whether the functions mentioned above and their correspondent molecules are altered during aging. Future works are needed to give us a more comprehensive understanding of the role oligodendroglial lineage cells played in aged brains, which could shed light on the clinical therapeutic strategies considering age-related neuronal functional diseases.

Enforced retirement is a great iniquity, in those countries where it exists. This is true of any attempt by the powers that be to thrust their idea of how a life should be lived onto tens of millions of people, all capable of making their own choices. Progress in medicine has for decades created longer, healthy lives, a slow upward trend that will accelerate now that the research community is earnestly attempting to treat the causes of aging. Those parts of the state concerned with ordering society, work, and finance at scale move far less rapidly. Much of the ink spilled on the topics of demographic aging, retirement, pensions, and economic consequences is a witness to the collision between (a) the reality of progress, the attempt to build a better world, and (b) the static vision of central planners who have no such beneficial goal in mind.

Although there is much debate about the age of retirement, already retirement itself is a decreasingly shared key labour market transition whereby work comes to a sudden stop at a specific age. As people work longer, the age at which they stop work varies, unretiring (ie, returning to the labour force after retirement) becomes increasingly common, people switch to part-time rather than full-time work, or engage in caring or broader social activities. As a result, older workers are characterised by increased diversity. This variety applies not only to employment, but also to health, education, and a broad range of socioeconomic factors. As a consequence, chronological age plays a declining role in defining a common set of problems among older workers; labour market policies need to focus less on age and more on worker characteristics, as is already the case for younger groups.

A focus on retirement age distracts from the importance of maintaining employment from age 50 years or older. In the UK, labour force participation is 85% for people aged 50-54 years, but falls to 58% at age 60-64 years and to 23% at age 65-69 years. Withdrawal from the labour market starts well before state pension age. If a longevity economy is to be achieved, supporting employment among people aged 50 years or older will be key.

Although improving the health and education of older workers will boost their productivity, this will count for little if employers believe that older workers are not productive. Evidence about the productivity of older workers is varied and often ambiguous, and varies substantially between sectors. Put simply, age does not seem to be as important a determinant of productivity as employers assume. This corporate ageism is a problem because it makes older workers more likely to lose their jobs and less likely to be hired than their younger counterparts, which contributes to the decline in employment before retirement age. In the face of such corporate ageism, there is a growing trend of older workers moving into the contingent economy (eg, part-time, gig economy, or contract work) and entrepreneurship. In the UK, over 40% of working people aged 65 years or older are self-employed, which is much higher than for any other age group.

Supporting a longevity economy will require legislation to tackle age discrimination, but social shifts and economic incentives will also be important. For instance, social perceptions about the productivity of older workers will change in response to new cohorts of older workers who have more education and better health than in previous waves. Also, shrinking populations will result in fewer younger workers, which will persuade some employers to be increasingly interested in older workers. Similarly, an ageing consumer base and the ability of technology and robotics to sustain people's productivity will increase the appeal of older workers.

Link: https://doi.org/10.1016/S2666-7568(21)00250-6

Why hasn't the research and development community achieved greater progress towards solving the problem of hair loss with age, given the sizable interest in achieving this goal? One possible answer is that a hair follicle is a very complicated structure that undertakes a shifting pattern of behaviors over time. It remains comparatively poorly understood as to why the various forms of hair loss occur, the fine details of the important mechanisms in each case. Efforts to intervene are challenging given the lack of a firm set of target mechanisms.

With stem cells that can be activated and silenced cyclically, hair follicle experiences multiple rounds of growth phase (anagen), regression phase (catagen), and resting phase (telogen) during lifespan. Hair cycling is initiated by cyclic renewal or physiological cyclic regeneration of stem cells. However, tissues and organs undergo structural and functional declines in the aging process, with physiological and pathological changes regulated by intrinsic and extrinsic factors that dictate the cell fate. As one of the important appendages of the skin, the hair follicle is a complex mini-organ with visible signs, such as decreased regenerative ability that leads to alopecia, and hair graying due to less melanin production by melanocyte stem cells during aging.

Hair regenerative ability is gradually decreased because hair follicle stem cells enter a long quiescent state, or differentiate into other skin epithelial lineages, or escape from the hair follicle niche during aging. These features promote hair follicle to become a widely used model for studying regeneration. As over 30% of the population all over the world suffer from partial or complete hair loss, particularly most people undergo alopecia during aging, understanding the mechanism by which hair follicle changes during aging is of great interest in regenerative biology and is essential for regenerative medicine.

Link: https://doi.org/10.3389/fcell.2021.799268

A good deal of evidence points to declining kidney function as a cause of declining cognitive function in aging. There are strong correlations between loss of kidney function and risk of dementia, for example. Correlation isn't a smoking gun in matters of aging, however: it is possible for any one of the underlying forms of molecular damage that cause aging, or for intermediate consequences of that damage, to give rise to otherwise unrelated pathologies in different parts of the body. Those pathologies appear more often in people with greater amounts of that form of damage, and thus appear correlated.

Nonetheless, there are good reasons to think that kidney failure and its downstream consequences contribute meaningful to neurodegeneration, perhaps largely by degrading the function of the vascular system. Vascular aging can cause damage and dysfunction in brain tissue via numerous mechanisms, including the pressure damage of hypertension, similar damage resulting from an acceleration of atherosclerosis, failing to delivery sufficient nutrients and oxygen to the energy-hungry brain, and disruption of the blood-brain barrier, allowing inflammatory cells and molecules into the brain.

Interactions Between Kidney Function and Cerebrovascular Disease: Vessel Pathology That Fires Together Wires Together

The kidney and the brain, as high-flow end organs relying on autoregulatory mechanisms, have unique anatomic and physiological hemodynamic properties. Similarly, the two organs share a common pattern of microvascular dysfunction as a result of aging and exposure to vascular risk factors (e.g., hypertension, diabetes, and smoking) and therefore progress in parallel into a systemic condition known as small vessel disease (SVD). Many epidemiological studies have shown that even mild renal dysfunction is robustly associated with acute and chronic forms of cerebrovascular disease.

Beyond ischemic SVD, kidney impairment increases the risk of acute cerebrovascular events related to different underlying pathologies, notably large artery stroke and intracerebral hemorrhage. Other chronic cerebral manifestations of SVD are variably associated with kidney disease. Observational data have suggested the hypothesis that kidney function influences cerebrovascular disease independently and adjunctively to the effect of known vascular risk factors, which affect both renal and cerebral microvasculature. In addition to confirming this independent association, recent large-scale human genetic studies have contributed to disentangling potentially causal associations from shared genetic predisposition and resolving the uncertainty around the direction of causality between kidney and cerebrovascular disease.

Accelerated atherosclerosis, impaired cerebral autoregulation, remodeling of the cerebral vasculature, chronic inflammation, and endothelial dysfunction can be proposed to explain the additive mechanisms through which renal dysfunction leads to cerebral SVD and other cerebrovascular events. Genetic epidemiology also can help identify new pathological pathways which wire kidney dysfunction and cerebral vascular pathology together. The need for identifying additional pathological mechanisms underlying kidney and cerebrovascular disease is attested to by the limited effect of current therapeutic options in preventing cerebrovascular disease in patients with kidney impairment.

The practice of calorie restriction improves long-term health and slows near all aspects of aging assessed to date. In humans, the beneficial effects of calorie restriction on healthy people are larger than any enhancement technology is yet proven to supply; it remains to be seen as to how the first rejuvenation therapies such as senolytics perform in larger populations of old individuals. Here, researchers focus on the effects of calorie restriction on the function of aging brain tissue. They take a conservative viewpoint on the widespread implementation of calorie restriction, despite the comprehensive animal data, as the sort of stringent dose-response studies and other evaluations required for the approval of pharmaceutical treatments have yet to be carried out in human patients for the practice of calorie restriction in the context of brain health.

The extracellular microenvironment is critical for maintaining normal physiological functions of cells because of its role in the homeostatic regulation of various components. Various factors, such as inflammation, metabolic waste, and the blood-brain barrier, can disrupt normal brain microenvironments. Thus, the maintenance of the extracellular environment is vital for brain health. Current studies have suggested that lifestyle interventions, such as regular exercise training, a healthy diet, and sufficient sleep, protect the brain by improving the microenvironment balance under pathological conditions.

Caloric restriction effectively protects the brain microenvironment via multiple mechanisms at molecular, cellular, and tissue levels. Major benefits obtained by CR are based on recent findings in aging and neuropathological models. However, there is currently no consensus on a unified protocol for CR because the duration or starting age of CR has not been clarified in animals. Reports have shown that the initiation age and duration of CR are critical factors that influence overall efficiency. Specifically, CR started at middle-age has the most potent neuroprotective effect.

Current studies on the neuroprotective effects of CR have various weaknesses, which include the lack of a precise description of the dosage curve (i.e., the relationship between CR duration and overall efficiency of neuroprotection), the lack of systematic observations of the additive effect of CR and drugs in counteracting neurodegeneration, and the absence of a neural circuit-specific effect of dietary interventions. These factors limit the large-scale promotion of CR in aging and high-risk populations with neurodegenerative diseases. Therefore, future explorations are required to understand the neuroprotective mechanisms underlying CR to develop alternative pharmaceutical or non-drug interventions for brain aging and neurodegeneration.

Link: https://doi.org/10.3389/fphys.2021.715443

Mutations affecting growth hormone metabolism and insulin metabolism, and that lead to extended life, are comparatively well studied in mammals. The longest lived mice are those in which growth hormone receptor is knocked out. Unfortunately this, like many interventions related to growth, nutrient sensing, and the like, produces a much greater effect on life span in short-lived species than in long-lived species. Humans with analogous loss-of-function mutations in growth hormone receptor may be resistant to some common age-related diseases, but do not live meaningfully longer than the rest of us.

In 1996, a report of extended longevity in mice homozygous for a mutation producing growth hormone (GH) deficiency was quickly followed by the demonstration of extensive homology between one of the key longevity genes in a worm, Caenorhabditis elegans, and genes coding for insulin receptor and insulin-like growth factor-1 (IGF-1) receptor in mammals. Since GH is the key determinant of hepatic IGF-1 expression and circulating IGF-1 levels, and has major impact on insulin signaling, these findings led to an exciting conclusion that the insulin/insulin-like growth factor signaling (IIS) is an evolutionarily conserved mechanism which controls aging in organisms ranging from yeast and worms to insects and mammals.

Subsequent work provided much evidence in support of this exciting realization, and this has led to a focus on IIS, rather than GH signaling, in analyzing genetic control of mammalian aging. This is an important distinction. Although biosynthesis and blood plasma levels of GH and IGF-1 are closely linked, the actions of these hormones are not identical and, in some cases, opposite. For example, IGF-1 mimics some of the insulin actions and promotes insulin sensitivity, while GH is anti-insulinemic and promotes insulin resistance; IGF-1 promotes fat deposition, while GH is lipolytic. Actions of GH not shared with IGF-1 include other effects relevant to aging such as impact on reactive radicals production and anti-oxidative defenses, DNA damage and repair, macrophage reprogramming, ovarian primordial follicle reserve, bone resorption and turnover, kidney dysfunction, and cognitive functioning.

In contrast to the remarkable extension of longevity in female and male mice lacking GH or GH receptors, the impact of reduced IGF-1 signaling on longevity of IGF1R ± mice and mice treated with an antibody to IGF-1 receptor is modest and seen only in one sex. This difference between the effects of reduced IGF-1 and GH signaling is likely related to IGF-1 exerting both beneficial and detrimental effects on aging and age-related disease (including opposite effects on the risk of type 2 diabetes vs cardiovascular disease and cognitive decline) and GH having primarily "pro-aging" effects. Both hormones impact growth, but the metabolic effects of GH are significantly greater.

Link: https://doi.org/10.3389/fgene.2021.667355

Sepsis is a state of runaway inflammation in response to infection, a condition that is more serious and more often fatal in older individuals. With age, the immune system becomes every more overactive and inflammatory, reacting to signals created by the damaged environment of the body. This background of chronic inflammation makes it ever less likely that any given incident of greatly raised inflammatory signaling will successfully resolve. Instead inflammation can rage to the point of causing serious harm and organ failure.

At present, treatments for sepsis are largely palliative, or focus on removing the infectious agent that caused the underlying immune reaction. This can be too little, too late. Sepsis has a high mortality rate. Some present research and development work goes towards sabotaging the feedback loop of runaway inflammatory signaling, such as by delivering cells that will work to resolve inflammation. This seems promising.

Today's open access paper discusses a different approach, however, suppression of oxidative signaling by delivering a natural antioxidant, modified to achieve a greater stability and cell uptake. Oxidative stress, the excessive production of oxidant molecules, goes hand in hand with inflammation in aging tissue, and numerous mechanisms connect oxidative stress to the inflammatory response. It is interesting to see that a suitable antioxidant therapy can make a difference in sepsis.

An Antioxidant Enzyme Therapeutic for Sepsis

Sepsis is a life-threatening organ dysfunction caused by the host's unbalanced response to infection. Septic shock is a type of sepsis in which the changes in metabolism, cells, and hemodynamics significantly increase the likelihood of fatality. Relevant studies have shown that there are more than 19 million sepsis patients worldwide each year, of which 6 million patients die, and the case fatality rate is greater than 25%. About 3 millions of those who survived had cognitive impairments that severely affected their quality of life. Septic shock is also one of the common clinical manifestations of severe patients with COVID-19. People over 65 years of age, infants, immunocompromised patients, and patients with autoimmune diseases, tumors, kidney diseases, and lung diseases are the most susceptible to sepsis. At present, treatments for sepsis mainly include fluid therapy (crystal fluid and albumin), antibacterial drugs, vasoactive drugs (norepinephrine), glucocorticoids, injection immunoglobulin, etc. Due to factors such as individual difference, aging, and antimicrobial resistance, the morbidity and mortality of sepsis remain high.

It has been documented that cytokines and reactive oxygen species (ROS) play essential roles in sepsis. ROS mainly come from cell respiration, protein folding, or various by-products of metabolism. Under pathological conditions, an unbalance of the generation and elimination of ROS results in oxidative stress with excess ROS. Since H2O2 is chemically stable and able to diffuse through cells and tissues, it may accumulate locally or systematically and activate the inflammatory response.

Upon the occurrence of infection, leukocytes are attracted to affected sites and release cytokines and ROS. An excessive level of ROS may damage the biological macromolecules such as DNA, proteins, and lipids, which may cause dysfunction of cells and tissues and further exacerbate the immune response. Uncontrolled production of ROS and cytokines may eventually lead to excessive inflammatory response and cytokine storm. Therefore, eliminating the excessively produced H2O2 helps to reduce the oxidative stress and to regulate the expression of pro-inflammatory cytokines, which is beneficial for the treatment of sepsis.

Organisms can effectively regulate their H2O2 levels through efficient enzymatic reactions. Catalase is the most abundant antioxidant enzyme commonly found in the liver, erythrocytes, and alveolar epithelial cells, and is the most effective catalyst for the decomposition of H2O2. Catalase has attracted much attention in maintaining normal physiological functions and relieving pathological processes. However, exogenous catalase generally exhibits poor in vivo stability and short plasma half-life, which preclude its broad use as therapeutics. Conjugation of therapeutic proteins with poly (ethylene glycol) (PEG) is the golden standard to improve their pharmacokinetics and immunogenicity. Herein, we explore the use of PEG-conjugated catalase as a therapeutic treatment for sepsis. Our results suggest that PEGylated catalase can effectively regulate cytokine production by activated leukocytes, suppress the elevated level of AST, ALT, TNF-α, and IL-6 in mice with induced sepsis, and significantly improve the survival rate of the mice.

Age-related frailty is accompanied by marked chronic inflammation, and indeed much of the physical weakness of frailty is likely caused by long-term inflammation and the ways in which it disrupts muscle tissue maintenance. The tools presently available to suppress inflammation are somewhat blunt, interfering in the necessary signaling needed to maintain a normal immune response, as well as in the unwanted overactivation of the immune system found in older people. Nonetheless, such tools are slowly becoming better and more selective over time, and some are now being tested as treatments for frailty.

Earlier this year, MyMD Pharmaceuticals merged with Akers Biosciences to form a new company focused on developing and commercialising novel immunotherapy therapies. The company's lead compound is MYMD-1, an indirect inhibitor of TNF alpha. The company CSO refers to the trial in January as a "sarcopenia/longevity" study, because "the FDA isn't accepting longevity or aging as an indication." There's also the fact that a true longevity study would require following people for many years, so it makes sense to focus on "markers like muscle loss, weakness, frailty, increased predisposition for age-related pathology, and the like."

The key proposition behind MyMD-1 is its ability to reduce chronic inflammation through the inhibition of several key cytokines, including the oft-cited TNF alpha. "TNF alpha is the star of the show. It's the first proinflammatory cytokine to go up when you get an infection or any type of inflammatory illness, and it turns on IL-6 and IL-1. It is the innate immune response, but it also gets out of control in autoimmune diseases. MyMD-1 is also selective, meaning that it doesn't take out innate immunity, but it does affect adaptive immunity, so we have selectivity there and we think that's going to make a big difference."

A mouse study conducted over the past couple of years and now submitted for publication has produced what sounds like some pretty exciting results. The study looked at the effect on lifespan on older mice (19 months old) treated with either MyMD-1, rapamycin, or a combination of rapamycin and metformin over a period of 13 months. "They saw that MyMD-1 resulted in a much more dramatic, fourfold-increased, highly statistically significant survival time. In addition, they saw absolutely no loss of muscle strength in male mice compared to those on the other compounds. Females had some loss, but nothing like they did in the other groups. What we're all looking for is a chance to slow aging and extend healthspan, and we think that this is happening both because of the anti-inflammatory effects of MyMD-1 and because it also blocks oxidative stress and things like fibrosis. We think it's the combination that really does the heavy lifting."

Link: https://www.longevity.technology/mymd-to-commence-phase-2-trial-in-frailty/

The blood-brain barrier wraps blood vessels where they pass through the central nervous system, controlling the passage of cells and molecules into and out of the brain. The blood-brain barrier becomes disrupted with age, allowing unwanted molecules into the brain, where they can spur chronic inflammation and dysfunction contributing to neurodegeneration. Researchers here investigate the response of astrocytes and microglia, supporting cells of the brain, to the age-related leakage of the blood-brain barrier, in search of points of intervention.

Blood-brain barrier (BBB) breakdown facilitates entry into the brain of neurotoxic blood-derived products and pathogens and has been linked to inflammatory and immune responses that can induce neuronal injury, synaptic dysfunction, and loss of neuronal connectivity. BBB disruption also facilitates leukocyte infiltration, which leads to glial cell death, axonal damage, lesion development, and therefore cerebrovascular dysfunction results in memory impairment, acceleration of neurovascular damage, and exacerbation of the progression of neuropathology in the central nervous system (CNS). Thus, critical demand exists for new therapies that minimize peripheral immune factors and limit the infiltration of peripheral immune cells into the brain.

The neurovascular unit, which comprises brain endothelial cells, pericytes, astrocytes, and microglia, primarily confers the low paracellular permeability of the BBB. The tight cell-to-cell contacts that these cell types establish with each other restrict the entry of red blood cells, leukocytes, and plasma components into the brain parenchyma and ensure the export of potentially neurotoxic molecules from the brain to the blood. The site of the anatomical BBB is composed of a continuous monolayer of endothelial cells that are connected by tight junctions (TJs) and adherens junctions. The interactions among the endothelial cells, pericytes, and glial cells are crucial for the formation and maintenance of the highly regulated CNS internal milieu.

Astrocytes play a dual role in limiting the entry of peripheral substances into the CNS: permeability factors secreted by reactive astrocytes open the BBB by disrupting endothelial TJs, but reactive astrocytes also perform a protective function by upregulating classical TJ proteins and using TJ proteins to corral activated T lymphocytes into distinct clusters. Microglia have also recently been shown to contribute to BBB induction, and studies have indicated that microglia also play a dual role in BBB repair. Initially, microglia maintain BBB integrity by expressing the TJ protein Claudin-5 and establishing physical contacts with endothelial cells, but during persistent inflammation, microglia engulf astrocytic endfeet and endothelial cells and impair BBB function.

Here, we investigated the transcriptional changes that occur in microglia and astrocytes by performing RNA sequencing on samples from five time points across the BBB permeability change during aging in mice. We report that whereas microglia are characterized by marked gene-level alterations related to negative regulation of protein phosphorylation and phagocytic vesicles, astrocytes show activation of enzyme- or peptidase-inhibitor signaling after detectable changes in BBB permeability. We also identify several genes enriched in these pathways that are notably altered after BBB breakdown. Our data reveal that microglia and astrocytes play an active role in maintaining BBB stabilization and corralling infiltrating cells, and thus might potentially function in ameliorating the lesions and neurologic disabilities in CNS diseases.

Link: https://doi.org/10.1016/j.omtn.2021.08.030

Far too little work in the medical research and development communities is focused on prevention or early intervention. It should always be easier to fix the early stages of a developing problem, medical or otherwise, and age-related diseases are no exception. Yet much of the development of therapies is focused on late stage disease rather than earlier, or even preclinical stages of the path to suffering and dysfunction. We might blame some of this on regulation that insists on treating only clearly defined disease, or on the tendency of researchers to study the end results of disease rather than the initial path to disease.

Regardless, the work described in today's research materials is an example of the sort of research and development that I'd like to see more of. The scientists involved aim to intervene in osteoarthritis by repairing damaged cartilage, but at earlier stages in the condition than is normally attempted, a point at which repair is an easier prospect for today's capabilities in cartilage tissue engineering. The less tissue that must be replaced, the more likely a tissue engineering strategy is to work.

Stopping arthritis before it starts

Osteoarthritis occurs when the protective cartilage that coats the ends of the bones breaks down over time, resulting in bone-on-bone friction. The disorder, which is often painful, can affect any joint, but most commonly affects those in our knees, hips, hands, and spine. To prevent the development of arthritis and alleviate the need for invasive joint replacement surgeries, the researchers are intervening earlier in the disease. "In some patients joint degeneration starts with posttraumatic focal lesions, which are lesions in the articular (joint) cartilage ranging from 1 to 8 cm2 in diameter. Since these can be detected by imaging techniques such as MRI, this opens up the possibility of early intervention therapies that limit the progression of these lesions so we can avoid the need for total joint replacement."

That joint preservation technology is a therapeutic bio-implant, called Plurocart, composed of a scaffold membrane seeded with stem cell-derived chondrocytes - the cells responsible for producing and maintaining healthy articular cartilage tissue. Building on previous research to develop and characterize the implant, the current study involved implantation of the Plurocart membrane into a pig model of osteoarthritis. This is the first time an orthopaedic implant composed of a living cell type was able to fully integrate in the damaged articular cartilage tissue and survive in vivo for up to six months. Molecular characterization studies showed the bio-implant mimicked natural articular cartilage, with more than 95 percent of implanted cells being identified as articular chondrocytes. The cartilage tissue generated was also biomechanically functional - both strong enough to withstand compression and elastic enough to accommodate movement without breaking.

Long-term repair of porcine articular cartilage using cryopreservable, clinically compatible human embryonic stem cell-derived chondrocytes

Generation of articular chondrocytes from pluripotent stem cells (PSCs) has been challenging as most chondrogenic cells during development are fated to undergo hypertrophy and endochondral ossification rather than adopt an articular chondrocyte identity. We and others have generated articular-like chondrocytes from human pluripotent stem cells; we have subsequently shown that stable articular chondrocytes produced from GFP-labelled PSCs can engraft, integrate into and repair osteochondral defects in small animal models. Moreover, these human cells produce all layers of hyaline cartilage after 4 weeks in vivo, including a PRG4+ superficial zone. However, production scaling and assessment of long-term, clinically relevant functionality has so far limited the development of these protocols.

The Yucatan minipig presents an excellent model for pre-clinical assessment of potential orthopedic therapies due to structural similarities, comparable thickness of articular cartilage, and the ability to create defects of substantial volume; in addition, their size allows for cost-efficient care and observation for extended periods of time. Here we present data demonstrating long-term functional repair of porcine full-thickness articular cartilage defects with hyaline-like cartilage by scalable production of clinical grade human embryonic stem cell-derived immature articular chondrocytes.

Growth hormone is not to be taken lightly; the side effects of tinkering with growth hormone metabolism can be highly problematic. Lowered levels of growth hormone or disruption of growth hormone metabolism via, say, growth hormone receptor knockout extends life in short lived mammals, and models show that it is beneficial even if started in adulthood. Nonetheless, most use of growth hormone involves adding more of it, which may not be a good idea. Here, a self-experimenter performs a quality self-experiment with growth hormone releasing hormone gene therapy, an approach to provoke upregulation of growth hormone. There was copious measurement, and the outcome was published in a journal - which should be something to aspire to for anyone in the self-experimentation community. Like all single subject studies, it should be treated as an interesting anecdote rather than as data, but it might inspire some thought and further research on what one might be able to do usefully with growth hormone metabolism in humans.

Here presented for the first time, are results showing persistence over a 5+ year period, in a human who had a hormone gene therapy administered to muscle. This growth hormone releasing hormone (GHRH) therapy was administered in 2 doses, a year apart, with a mean after the second dose of 195 ng/ml (13 times normal). This level of GHRH therapy appears to be safe for the subject, although there were some adverse events. IGF-1 levels were little affected, nor were growth hormone test results, showing no indications of acromegaly for the hormone homolog used. Heart rate declined 8 to 13 bpm, persistent over 5 years. Testosterone rose by 52%. HDL/LDL ratio dropped from 3.61 to mean 2.81, triglycerides declined from 196 mg/dL to mean 94.4 mg/dL.

White blood cell counts increased, however the baseline was not strong. CD4+ and CD8+ white blood cell mean count increased 11.7% and 12.0% respectively. Ancillary observations comprise an early period of euphoria, and dramatic improvement in visual correction after the first dose, spherical correction from baseline (L/R) -2.25/-2.75 to -0.25/-0.5. Over the next 5 years correction drifted back to -1.25/-1.75. Horvath phenoage was cut 44.1% post-treatment. At completion, epigenetic age was -6 years (-9.3%), and telomere age was +7 months (+0.9%).

Link: https://doi.org/10.1089/rej.2021.0036

In recent years, researchers have produced what looked like promising results in reprogramming supporting cells in the brain into neurons via neuroD1 gene therapy. A way to do this, to produce new neurons that can integrate into existing neural circuits, would provide a road to regeneration of the brain. Unfortunately, and as sometimes happens, this may all be a dead end, and the early promise was based on misinterpretation of the data. This will likely be hashed out further in the next few years; science often proceeds in this way, and this is one of the many reasons as to why independent replication is vital to scientific progress.

In 2019, researchers in Japan published breakthrough results detailing how NeuroD1, a protein involved in cell differentiation, could coax microglia into new neurons. Now, researchers in China have found that not only does NeuroD1 not induce microglia-to-neuron conversion, but also that the protein induces microglia death. The team set out to investigate the molecular mechanisms underpinning the original finding, since microglia and neurons descend from different cellular lineages.

The researchers applied a rigid lineage tracing protocol to follow the cellular differentiation progression in mice, as well as to monitor the effect of lentiviral vectors - an inert virus package used to carry NeuroD1 to the central nervous system - on the process. They validated their observations through live cell imaging and pharmacological approaches. "Disappointingly, our results do not support the 'microglia-to-neuron conversion. Instead, our data strongly indicate that the previously observed conversion was actually due to the experimental artifacts from viral leakage."

The assumed finding was likely due to NeuroD1's actual role: triggering microglial cell death. Neurons are unaffected by NeuroD1 so their numbers will stay the same, while microglia cell numbers decrease. However, due to the low purity of the microglia and the viral leakage, it could appear that while microglia cells were decreasing, non-microglia cells were increasing, leading to the conclusion in vitro that microglia were converting to neurons.

"The 'microglia-to-neuron' conversion should be verified following three principles: 1) unambiguous microglial-based lineage tracing and lack of lentiviral leakage, along with well-designed controls; 2) unambiguous live cell imaging to show how an individual microglial cell converts to a neuron; and 3) upon microglial depletion, there should be no or few microglia-converted neurons." The last point appeared to be supported in the original paper, but when researchers replicated the experiment, they found that even when 98.9% of microglia cells were killed, numerous "microglia-converted neurons" were still observed. Such a finding suggests that the converted neurons were mislabeled cells rather than the desired neurons.

Link: https://www.eurekalert.org/news-releases/936970

Arguably the primary reason why the number of senescent cells increases with age throughout the body is the growing failure of the immune system to clear these errant cells. The reasons for that failure are not well understood in detail, though some inroads have been made into that area of research. Both the innate and adaptive immune system are involved in clearance of senescent cells, so in principle there should be a plethora of mechanisms that could be targeted in order to create immunotherapies that increase the pace at which the immune system clears senescent cells. Both SIWA Therapeutics and Deciduous Therapeutics are working on approaches to this goal.

Today's research materials discuss a different way forward. If senescent cells have surface features that are distinctive enough, not shared to a large degree with other cells, then it should be possible to immunize against one of those features, and have the adaptive immune system vigorously attack senescent cells for an extended period of time, perhaps years or more. Such surface features should exist, because the immune system does in fact recognize and clear senescent cells. The work of SIWA Therapeutics is based on use of a specific set of surface features, but it seems likely that there will be variance in such features from tissue to tissue. The paper I point out today focuses on one tissue only, the vascular endothelium, as the researchers involved are interested in the role of cellular senescence in the progression of atherosclerosis. Their findings may or may not generalize to any other tissues.

Senolytic vaccination improves normal and pathological age-related phenotypes and increases lifespan in progeroid mice

Elimination of senescent cells (senolysis) was recently reported to improve normal and pathological changes associated with aging in mice. However, most senolytic agents inhibit antiapoptotic pathways, raising the possibility of off-target effects in normal tissues. Identification of alternative senolytic approaches is therefore warranted. Here we identify glycoprotein nonmetastatic melanoma protein B (GPNMB) as a molecular target for senolytic therapy. Analysis of transcriptome data from senescent vascular endothelial cells revealed that GPNMB was a molecule with a transmembrane domain that was enriched in senescent cells (seno-antigen). GPNMB expression was upregulated in vascular endothelial cells and/or leukocytes of patients and mice with atherosclerosis.

Genetic ablation of Gpnmb-positive cells attenuated senescence in adipose tissue and improved systemic metabolic abnormalities in mice fed a high-fat diet, and reduced atherosclerotic burden in apolipoprotein E knockout mice on a high-fat diet. We then immunized mice against Gpnmb and found a reduction in Gpnmb-positive cells. Senolytic vaccination also improved normal and pathological phenotypes associated with aging, and extended the male lifespan of progeroid mice. Our results suggest that vaccination targeting seno-antigens could be a potential strategy for new senolytic therapies.

Exercise improves cognitive function, both in the short term immediately following exercise, and in the long term as a result of increased physical fitness. These effects appear to be mediated by increased neurogenesis in the brain, the production of new neurons and their incorporation into neural circuits. This is particularly important in learning and memory, with most research focused on the hippocampus. Here, researchers dig in deeper to better understand how neurogenesis improves these aspects of cognitive function following exercise.

The incidence of cognitive decline increases with age, especially for impairments in episodic memory and spatial memory, which are typically associated with the hippocampus. Deterioration in the morphometry of the hippocampus, as well as the integrity of its circuitry, are thought to be critical in the progression of these deficits. There is increasing evidence that some forms of physical exercise protect against spatial memory decline; however, the results have been inconsistent in both humans and animals. Although several explanations have been proposed, the precise mechanisms by which exercise improves brain health remain unclear. We recently demonstrated that an optimal period of exercise in aged mice is required to activate neurogenesis in a growth hormone-dependent manner, resulting in the restoration of hippocampal-dependent spatial learning. What remains elusive, however, is how the structure and functional circuitry of the hippocampus is remodeled and what drives these connectivity changes following exercise in the aged brain.

In studies showing that adult hippocampal neurogenesis (AHN) leads to cognitive changes during aging, little has been reported about how exercise affects the structure and functional circuitry responsible for behavioral changes, and whether any circuitry changes are dependent on the level of neurogenesis. Magnetic resonance imaging (MRI) studies in humans have revealed that older adults show significant increases in hippocampal volume and functional connectivity after aerobic exercise intervention. Similarly, rodent MRI studies have demonstrated that running increases hippocampal volume and blood flow. However, the specific circuitry related to improved cognition and whether this is directly regulated by neurogenesis remain unknown.

To address these issues, we applied structural, diffusion, and functional MRI (fMRI) longitudinally following different periods of exercise in mouse models. We hypothesized that behavioral performance in aged mice depends on dentate gyrus (DG) connectivity driven by exercise-induced neurogenesis. To determine the contribution of AHN to this process, we specifically ablated doublecortin (DCX)-positive newborn neurons using our novel knockin DCXDTR mouse line. Our results reveal that improved spatial learning in aged mice after exercise is due to enhanced DG connectivity, particularly the strengthening of the DG-Cornu Ammonis 3 (CA3) and the DG-medial entorhinal cortex (MEC) connections in the dorsal hippocampus. Moreover, we provide evidence that this change in circuitry is dependent on the activation of neurogenesis.

Link: https://doi.org/10.1016/j.isci.2021.103450

Autophagy is a collection of processes that remove damaged and unwanted molecules and structures from a cell, delivering them to a lysosome where they are broken down into raw materials for further protein synthesis. Many of the approaches shown to slow aging in short-lived species are characterized by improved autophagy, and evidence from research into calorie restriction suggests that autophagy may be the most important of the many mechanisms linking the operation of cellular metabolism to the pace of aging. Autophagy is known to falter with age, and the research community has identified numerous specific defects that arise in older individuals. So far progress has been slow when it comes to the development of therapies that specifically target and improve autophagy, though most calorie restriction mimetic drugs, such as mTOR inhibitors, do so to some degree as a part of their broad effects on metabolism.

We know that the world's population is currently living longer. This is especially problematic, given the increase in the prevalence of chronic conditions resulting from an increased aging population, thus negatively affecting the healthspan and quality of life of the affected individuals. This review discussed the effects of aging on the cardiovascular system and established an increased predisposition of cardiovascular pathologies in the geriatric population due to molecular, structural, and functional changes in both the cardiac and vascular systems. Longevity molecular pathways exist to maintain the homeostasis of the cardiovascular system and promote health. Autophagy is at the interlink of these pathways.

Although autophagy is downregulated as people age, stimulation of this pathway through caloric restriction, intermittent fasting, and supplementation of pharmacologic agents can reinstate autophagy in older individuals. Induced autophagy promotes the longevity of cardiovascular health, thereby instigating the role of autophagy in the prevention of chronic conditions such as cardiovascular ailments. Strong evidence for this notion has emerged from studies using genetically modified mice defective in genes, transcription factors, and proteins essential for autophagy and as such failed to show improvements in cardiovascular health when caloric restriction, intermittent fasting, and pharmacologic agents are implemented.

To summarize, future research should be directed toward human studies or human tissues in vitro. This will allow for a clearer understanding of the role of autophagy on the longevity pathways and cardiovascular disease prevention in humans. In addition, future research should evaluate how the beneficial effects of autophagy can be implemented reproducibly and on large scales in the population.

Link: https://doi.org/10.7759/cureus.20042

Neurodegenerative diseases are strongly associated with the buildup of protein aggregates, misfolded or altered amyloid-β, tau, α-synuclein, and so forth, wherein one altered molecule can encourage others to also alter, leading to solid deposits in brain tissue and a surrounding halo of toxic biochemistry that degrades cell function and kills cells. Much of the Alzheimer's research and development to date has focused on how to clear those aggregates; unfortunately success in clearance of amyloid-β in Alzheimer's disease has failed to produce meaningful benefits to patients.

It is possible that protein aggregates are a relevant target in the very early stages of neurodegeneration, but after the point at which the immune system becomes roused, and significant numbers of cells become senescent in response to a toxic environment rich the molecular waste of aggregated proteins, it no long matters whether aggregates are present or not. Senescent cells drive inflammation which drives further senescence and tissue dysfunction, in a feedback loop that leads to major loss of neurons and death.

Researchers have shown that the use of senolytic treatments capable of bypassing the blood-brain barrier and destroying senescent cells in the brain, such as the dasatinib and quercetin combination, reduces neuroinflammation and late-stage pathology in mouse models of tau aggregation. This strongly implicates senescent cells in the progression of inflammation in neurodegenerative diseases. The caveat in this sort of study is that the mouse models are highly artificial, as mice do not normally develop this sort of condition, but nonetheless: more senescent cells in the brain is demonstrably a bad thing, and removing them improves matters. A human trial of senolytics for Alzheimer's patients has started, but it will likely be some years before results are announced.

Today's research materials provide supporting evidence for the relevance of senescent cells in the brain to neurodegenerative disease. Along the way it touches on a debate that is ongoing: senescence is a state of growth arrest, so what does senescence look like in non-replicating cells such as neurons? Is it also a relevant, harmful process, or are the supporting cells in the brain more of a problem when they become senescent? Certainly there is good evidence for senescent microglia and astrocytes to be a major issue in older animals. Further, is it a good idea to be destroying senescent neurons, and do senolytic treatments that work in other cell types in fact achieve that goal? These and other questions remain to be answered. The mice end up better off, destruction of neurons or no destruction of neurons, but I'd imagine that a more definitive understanding will be sought for broader human use of senolytics.

Scientists Identify Malfunctioning Brain Cells as Potential Target for Alzheimer's Treatment

Research conducted 2018 found that senescent cells accumulated in mouse models of Alzheimer's disease where they contributed to brain cell loss, inflammation, and memory impairment. When the researchers used a therapy to clear the senescent cells, they halted disease progression and cell death. "However, until now, we didn't know to what extent senescent cells accumulated in the human brain, and what they actually looked like. It was somewhat like looking for the proverbial needle in a haystack except we weren't sure what the needle looked like."

Using sophisticated statistical analyses, the research team was able to evaluate large amounts of data. In total, they profiled tens of thousands of cells from the postmortem brains of people who had died with Alzheimer's disease. The researchers' plan was to first determine if senescent cells were there, then how many there were and what types of cells they were. They succeeded. The team found that approximately 2% of the brain cells were senescent and that the senescent cells were neurons, which are the fundamental units in the brain that process information and are the workhorses of memory. They also are the primary cells that are lost in Alzheimer's disease.

Next, the team sought to determine if the senescent neurons had tangles - abnormal accumulations of a protein called tau that can collect inside neurons in Alzheimer's disease. These tangles closely correlate with disease severity, meaning that the more tangles individuals have in their brains, the worse their memory. The researchers found that the senescent neurons not only had tangles but that they overlapped to the point that it was hard to distinguish between them.

Profiling senescent cells in human brains reveals neurons with CDKN2D/p19 and tau neuropathology

Senescent cells contribute to pathology and dysfunction in animal models. Their sparse distribution and heterogenous phenotype have presented challenges to their detection in human tissues. We developed a senescence eigengene approach to identify these rare cells within large, diverse populations of postmortem human brain cells. Eigengenes are useful when no single gene reliably captures a phenotype, like senescence. They also help to reduce noise, which is important in large transcriptomic datasets where subtle signals from low-expressing genes can be lost. Each of our eigengenes detected ∼2% senescent cells from a population of ∼140,000 single nuclei derived from 76 postmortem human brains with various levels of Alzheimer's disease (AD) pathology.

More than 97% of the senescent cells were excitatory neurons and overlapped with neurons containing neurofibrillary tangle (NFT) tau pathology. Cyclin-dependent kinase inhibitor 2D (CDKN2D/p19) was predicted as the most significant contributor to the primary senescence eigengene. RNAscope and immunofluorescence confirmed its elevated expression in AD brain tissue. The p19-expressing neuron population had 1.8-fold larger nuclei and significantly more cells with lipofuscin than p19-negative neurons. These hallmark senescence phenotypes were further elevated in the presence of NFTs. Collectively, CDKN2D/p19-expressing neurons with NFTs represent a unique cellular population in human AD with a senescence-like phenotype.

The accumulation of senescent cells is an important contributing cause of degenerative aging. Since these cells can be specifically targeted via a range of mechanisms, and selective destruction of senescent cells produces significant and rapid rejuvenation in animal studies, there is considerable interest in the research community in finding novel ways to measure the burden of cellular senescence. Senescent cells secrete a mix of pro-growth, inflammatory molecules into circulation, and so it is possible that some of those molecules can form the basis for low-cost assays conducted on blood samples.

Cellular senescence is a cell fate primarily induced by DNA damage, characterized by irreversible growth arrest in an attempt to stop the damage. Senescence is a cellular response to a stressor and is observed with aging, but also during wound healing and in embryogenic developmental processes. Senescent cells are metabolically active and secrete a multitude of molecules gathered in the senescence-associated secretory phenotype (SASP). The SASP includes inflammatory cytokines, chemokines, growth factors, and metalloproteinases, with autocrine and paracrine activities.

Among hundreds of molecules, angiopoietin-like 2 (angptl2) is an interesting, although understudied, SASP member identified in various types of senescent cells. Angptl2 is a circulatory protein, and plasma angptl2 levels increase with age and with various chronic inflammatory diseases such as cancer, atherosclerosis, diabetes, heart failure and a multitude of age-related diseases. In this review, we will examine in which context angptl2 was identified as a SASP factor, describe the experimental evidence showing that angptl2 is a marker of senescence in vitro and in vivo, and discuss the impact of angptl2-related senescence in both physiological and pathological conditions. Future work is needed to demonstrate whether the senescence marker angptl2 is a potential clinical biomarker of age-related diseases.

Link: https://doi.org/10.3390/ijms222212232

It is widely appreciated in the research community that the general age-related decline in mitochondrial function (and in mitophagy, the quality control mechanism responsible for culling broken mitochondria) is important to the progression of degenerative aging and onset of age-related disease. A great many research groups are looking into ways to boost mitophagy and mitochondrial function, some purely compensatory and unrelated to age-related changes, while others attempt to address some part of the poorly mapped chain of cause and consequence that leads from the underlying molecular damage of aging to mitochondrial dysfunction. So one will see a variety of papers such as this one, evaluating what is known of one potential target by which mitochondrial function might be improved.

A decline in mitochondrial function has long been associated with age-related health decline. Several lines of evidence suggest that interventions that stimulate mitochondrial autophagy (mitophagy) can slow aging and prolong healthy lifespan. Prohibitins (PHB1 and PHB2) assemble at the mitochondrial inner membrane and are critical for mitochondrial homeostasis. In addition, prohibitins (PHBs) have diverse roles in cell and organismal biology.

Mitophagy is the breakdown of damaged mitochondria via autophagy. Mitophagy and mitochondrial dynamics (fission/fusion) are linked in maintaining mitochondrial quality control. Excessive mitochondrial fusion or impaired mitochondrial fission is an underlying factor in the age-related decline in mitophagy, which is associated with senescence and aging. PHB2 binds to microtubule-associated protein 1A/1B-light chain 3 (LC3) to promote degradation of the mitochondria by an autophagosome. A second study found further support that PHBs can promote mitophagy. This study found a new axis for mitophagy by PHB2: loss of PHB2 prevented mitophagy by destabilizing PINK1, which inhibited recruitment of Parkin, optineurin, and ubiquitin. Conversely, increasing PHB2 levels was found to increase mitophagy by promoting Parkin recruitment.

In conclusion, PHBs have therapeutic potential in a variety of age-related diseases. Targeting PHBs may represent an attractive therapeutic target to counteract aging and age-onset disease.

Link: https://doi.org/10.3389/fgene.2021.714228

Plasma transfusions haven't performed well in either mouse or human studies when it comes to attempts to transfer youthful benefits to older individuals. This may be because dilution of harmful factors in old blood is more important than the provision of beneficial factors present in young blood, and a transfusion just doesn't provide enough dilution. In today's research materials, the goal is instead to transfer some of the benefits of exercise via factors present in the bloodstream of fit individuals that is absent in sedentary individuals. The initial results seem somewhat more positive.

Exercise is well established to improve cognitive function. This happens both in the short term, immediately following exercise, and over the long term as a consequence of improved fitness. One of the identified mechanisms involves upregulation of BDNF, which in turn boosts the pace of neurogenesis in brain regions responsible for memory. In the research here, scientists identify another beneficial signal molecule, clusterin. In this case the beneficial effect is a reduction in inflammation in brain tissue.

Blood from marathoner mice boosts brain function in their couch-potato counterparts

Investigators put either functional or locked running wheels into the cages of 3-month-old lab mice, which are metabolically equivalent to 25-year-old humans. A month of steady running was enough to substantially increase the quantity of neurons and other cells in the brains of marathoner mice when compared with those of sedentary mice. Next, the researchers collected blood from marathoner and, as controls, sedentary mice. Then, every three days, they injected other sedentary mice with plasma (the cell-free fraction of blood) from either marathoner or couch-potato mice. Each injection equaled 7% to 8% of the recipient mouse's total blood volume. (An equivalent amount in humans would be about 1/2 to 3/4 of a pint).

On two different lab tests of memory, sedentary mice injected with marathoner plasma outperformed their equally sedentary peers who received couch-potato plasma. In addition, sedentary mice receiving plasma from marathoner mice had more cells that give rise to new neurons in the hippocampus (a brain structure associated with memory and navigation) than those given couch-potato plasma transfusions.

Turning to an examination of proteins in the marathoner mice's blood, the team identified 235 distinct proteins, of which 23 were scarcer and 26 more abundant in marathoner compared with couch-potato mice. Several of these differentially expressed proteins were associated with the complement cascade - a set of about 30 blood-borne proteins that interact with one another to kick-start the immune response to pathogens. Removing a single protein, clusterin, from marathoner mice's plasma largely negated its anti-inflammatory effect on sedentary mice's brains. No other protein the scientists similarly tested had the same effect. Clusterin, an inhibitor of the complement cascade, was significantly more abundant in the marathoners' blood than in the couch potatoes' blood.

Further experiments showed that clusterin binds to receptors that abound on brain endothelial cells, the cells that line the blood vessels of the brain. These cells are inflamed in the majority of Alzheimer's patients, and research has shown that blood endothelial cells are capable of transducing chemical signals from circulating blood, including inflammatory signals, into the brain. Clusterin by itself, even though administered outside the brain, was able to reduce brain inflammation in two different strains of lab mice in which either acute bodywide inflammation or Alzheimer's-related chronic neuroinflammation had been induced.

Exercise plasma boosts memory and dampens brain inflammation via clusterin

Physical exercise is generally beneficial to all aspects of human and animal health, slowing cognitive ageing and neurodegeneration. The cognitive benefits of physical exercise are tied to an increased plasticity and reduced inflammation within the hippocampu, yet little is known about the factors and mechanisms that mediate these effects. Here we show that 'runner plasma', collected from voluntarily running mice and infused into sedentary mice, reduces baseline neuroinflammatory gene expression and experimentally induced brain inflammation.

Plasma proteomic analysis revealed a concerted increase in complement cascade inhibitors including clusterin (CLU). Intravenously injected CLU binds to brain endothelial cells and reduces neuroinflammatory gene expression in a mouse model of acute brain inflammation and a mouse model of Alzheimer's disease. Patients with cognitive impairment who participated in structured exercise for 6 months had higher plasma levels of CLU. These findings demonstrate the existence of anti-inflammatory exercise factors that are transferrable, target the cerebrovasculature and benefit the brain, and are present in humans who engage in exercise.

Researchers here report on their investigation of the role of the long noncoding RNA CYTOR, involved in muscle function, and which declines in expression with age. As a class, long noncoding RNAs are comparatively poorly explored, and many, such as CYTOR, appear to participate in numerous critical cell functions, touching on structure, growth, and migration. Concretely, however, it seems that CYTOR is a potential target to improve muscle function in later life, and the work here shows that it can be upregulated to beneficial effect in mice via gene therapy strategies without immediately obvious side-effects.

Skeletal muscle displays remarkable plasticity upon exercise and is also one of the organs most affected by aging. Despite robust evidence that aging is associated with loss of fast-twitch (type II) muscle fibers, the underlying mechanisms remain to be elucidated. Here, we identified an exercise-induced long noncoding RNA, CYTOR, whose exercise responsiveness was conserved in human and rodents. Cytor overexpression in mouse myogenic progenitor cells enhanced myogenic differentiation by promoting fast-twitch cell fate, whereas Cytor knockdown deteriorated expression of mature type II myotubes. Skeletal muscle Cytor expression was reduced upon mouse aging, and Cytor expression in young mice was required to maintain proper muscle morphology and function.

In aged mice, rescuing endogenous Cytor expression using adeno-associated virus serotype 9 delivery of CRISPR activation reversed the age-related decrease in type II fibers and improved muscle mass and function. In humans, CYTOR expression correlated with type II isoform expression and was decreased in aged myoblasts. Increased CYTOR expression, mediated by a causal cis-expression quantitative trait locus located within a CYTOR skeletal muscle enhancer element, was associated with improved 6-minute walk performance in aged individuals from the Helsinki Birth Cohort Study. Direct CYTOR overexpression using CRISPRa in aged human donor myoblasts enhanced expression of type II myosin isoforms.

In conclusion, the long noncoding RNA Cytor was found to be a regulator of fast-twitch myogenesis in aging. These findings may lead to the future development of interventions to improve myogenesis.

Link: https://doi.org/10.1126/scitranslmed.abc7367

Angiotensin II is used in many mouse models to induce hypertension and tissue damage, thereby accelerating the progression of a range of age-related conditions, including atherosclerosis. Researchers here show that an increased burden of senescent cells mediates these effects of angiotensin II, and that clearing senescent cells prevents the harms caused by increased angiotensin II levels. The near ubiquity of cellular senescence as an important mechanism linking forms of lower level molecular damage and dysregulation of metabolism to the development of disease continues to be surprising, even now.

Angiotensin II can cause oxidative stress and increased blood pressure that result in long term cardiovascular pathologies. Here we evaluated the contribution of cellular senescence to the effect of chronic exposure to low dose angiotensin II in a model that mimics long term tissue damage. We utilized the INK-ATTAC (p16Ink4a-Apoptosis Through Targeted Activation of Caspase 8) transgenic mouse model that allows for conditional elimination of p16Ink4a-dependent senescent cells by administration of AP20187.

Angiotensin II treatment for 3 weeks induced ATTAC transgene expression in kidneys but not in lung, spleen, and brain tissues. In the kidneys increased expression of ATM, p15, and p21 matched with angiotensin II induction of senescence-associated secretory phenotype genes MMP3, FGF2, IGFBP2, and tPA. Senescent cells in the kidneys were identified as endothelial cells by detection of GFP expressed from the ATTAC transgene and increased expression of angiopoietin 2 and von Willebrand Factor, indicative of endothelial cell damage. Furthermore, angiotensin II induced expression of the inflammation-related glycoprotein versican and immune cell recruitment to the kidneys.

AP20187-mediated elimination of p16-dependent senescent cells prevented physiologic, cellular, and molecular responses to angiotensin II and provides mechanistic evidence of cellular senescence as a driver of angiotensin II effects. In conclusion, the low dose, prolonged angiotensin II exposure is associated with the induction of senescence in kidneys and the promotion of an inflammatory microenvironment through both secreted factors and immune cells. Endothelial cells appear to be a major cell type impacted. The elimination of senescent cells in the INK-ATTAC transgenic model prevents these effects of angiotensin II and reveals a novel pathophysiologic mechanism amenable to targeting by senolytic drugs in development.

Link: https://doi.org/10.3389/fcell.2021.782841

The author of this commentary is entirely too enthusiastic about mTOR inhibitors as a tool to slow the aging process, but here he is largely focused on a different question. He argues (a) the sensible point that limits to aging and longevity are entirely determined by medical technology, and (b) the more debatable point that old people do not receive sufficient application of present forms of medical technology, and this is life-limiting. How much of the observed compression of morbidity of recent decades, meaning that people are living more healthy, functional years without an increase in overall life expectancy, is the rest of uneven application of incremental advances in medicine, where the younger old are treated but the older old are not?

My view of the existence of compression of morbidity has long been that some processes of aging must be largely unaffected by everything achieved to date in the field of medicine, while also only contributing greatly to mortality in very late life. So a process that is of little influence up to age 70, say, but which becomes increasingly harmful after that age. Transthyretin amyloidosis might be a candidate for that process, given the findings that it is a major cause of death in supercentenarians. Equally, more recent data is implicating it in heart disease in younger demographics, so perhaps it isn't.

As to the bigger picture: we are complex machines, and the more effort put into maintaining a machine, the longer it will remain in a good state, working and functional. There is nothing magical about aging, it is just damage and dysfunction. That we cannot sufficiently repair that damage or greatly influence the consequent dysfunction today does not mean that there is a limit to life span, set in stone. That limit will be changed tomorrow. Indeed, I would it expect to make a sizable leap upward as a result of the use of senolytic drugs in conjunction with other SENS-style approaches to rejuvenation, as they emerge from the labs and into clinical practice. If compression of morbidity continues in that environment, then it will mean that the research community has not yet targeted the most important forms of damage and dysfunction in the oldest of people.

No limit to maximal lifespan in humans: how to beat a 122-year-old record

Life expectancy is constantly rising and median lifespan is increasing but maximum lifespan is not. Although the number of centenarians (100 years old or older) is doubling every ten years, maximum longevity remains the same. The longest living person died in 1997 at the age of 122 and this record has not been beaten. It was suggested that longevity records cannot be overcome unless a scientific breakthrough in delaying aging would happen. First, such scientific breakthroughs are happening now and drugs that slow down aging are becoming available. Yet, these drugs have not yet been employed in a sufficient number of humans for a sufficiently long period of time to make demographic impact. This breakthrough will eventually break the lifespan record. However, such a breakthrough is not even necessary. A mere application of standard medical care to centenarians, as rigorously as to younger adults, would probably extend lifespan beyond 122, even without the need of a scientific breakthrough.

We will discuss here that an increase of average lifespan without maximal lifespan is happening because advanced medical interventions are available for everyone except the oldest old, exactly those who may live longer than 122, if treated. While a thirty-year old patient with heart disease may become a candidate for heart transplantation, it would be ridiculous even to mention heart transplantation for a supercentenarian. In other words, life-extending care is not available (usually with best intentions; in many cases, patients themselves do not want aggressive medical interventions) exclusively and specifically to those who can beat the 122 lifespan record. Furthermore, since their death certificates state "old age" instead of a specific disease, most centenarians do not receive treatment but even a diagnosis. As we will discuss, this explains why the 122 year record is not broken despite the absence of any biological constraints.

The lifespan of slowly aging centenarians can be extended by providing them adequate medical care. But can an average person beat the 122-year-old record? Currently, medical interventions extend lifespan mostly by extending morbidity span. By now several interventions were shown to increase healthspan and lifespan in animals. Hypothetically, these interventions may transform an average person into a slowly aging centenarian.

Rapamycin and everolimus are available to delay age-related diseases and increase health span in pets and humans. Rapamycin-based therapy may include medications such as metformin, aspirin, angiotensin-2 antagonists, PDE5 inhibitors, DHEA, melatonin and several others as well as fasting or low carb diets. In theory, anti-aging therapy may make an average human resemble centenarians, aging slower and developing diseases later. Due to anti-aging treatment, these centenarians will reach 100 in good health, just as genetic centenarians. These centenarians should seek thorough medical care, according to their lower biological age, not according to their chronological age. This, however, will require the revolution of policies, ethical standards and legal issues to ensure maximum longevity.

This open access paper runs through a range of data for the assessment of procyanidin C1 as a senolytic compound capable of selectively destroying senescent cells, both in cell studies and in animal studies. Procyanidin C1 clearly isn't as good as dasatinib and quercetin (or fisetin alone) in mice, but it does extend mouse life span by a little under 10%. The mechanism of action appears to involve induction of mitochondrial dysfunction in senescent cells, leading to programmed cell death, but there is a good deal of work remaining in order to fully understand how procyanidin C1 achieves this outcome, and whether or not it is synergistic with other senolytics.

Ageing-associated functional decline of organs and increased risk for age-related chronic pathologies is driven in part by the accumulation of senescent cells, which develop the senescence-associated secretory phenotype (SASP). Here we show that procyanidin C1 (PCC1), a polyphenolic component of grape seed extract (GSE), increases the healthspan and lifespan of mice through its action on senescent cells. By screening a library of natural products, we find that GSE, and PCC1 as one of its active components, have specific effects on senescent cells. At low concentrations, PCC1 appears to inhibit SASP formation, whereas it selectively kills senescent cells at higher concentrations, possibly by promoting production of reactive oxygen species and mitochondrial dysfunction.

In rodent models, PCC1 depletes senescent cells in a treatment-damaged tumour microenvironment and enhances therapeutic efficacy when co-administered with chemotherapy. Intermittent administration of PCC1 to either irradiated, senescent cell-implanted, or naturally aged old mice alleviates physical dysfunction and prolongs survival. We identify PCC1 as a natural senotherapeutic agent with in vivo activity and high potential for further development as a clinical intervention to delay, alleviate, or prevent age-related pathologies.

Link: https://doi.org/10.1038/s42255-021-00491-8

Atherosclerosis, the formation of fatty plaques that weaken and narrow blood vessels, is in part driven by inflammation. Inflammatory signaling in atherosclerotic plaque attracts circulating monocytes that enter tissue from the bloodstream, become dysfunctional macrophages, and die. It also biases those macrophages away from useful behavior related to repairing the plaque, even as the toxicity of the plaque environment destroys them. Blunt approaches to suppressing inflammation have been shown to modestly reverse plaques, but nowhere near as much as is needed to produce a cure. These blunt approaches also have significant long-term negative side-effects as a result of degrading immune function where it is needed and useful. There is always the possibility that more selective ways can be found to reduce only the problematic inflammatory signaling, however, such as the example here. It remains to be seen as to whether this will be more effective in reversing plaque burden.

In vascular diseases like atherosclerosis, arterial walls thicken and harden, disturbing blood flow. That leads to a buildup of plaque, which could ultimately lead to blocked arteries. Studies have linked microRNA-92a (miR-92a) to dysfunction of the endothelial cells that line the inside of blood vessels, which means miR-92a is considered a biomarker of the disease.

While a miR-92a inhibitor treatment exists (and has been tested in animals and humans), it cannot yet be delivered directly to the blood vessel site, and therefore is not as effective as it could be. Several years ago, researchers developed a nanoparticle - a polyelectrolyte complex micelle - to deliver the inhibitor directly to inflamed blood vessel cells. This nanoparticle uses a peptide to target the vascular cell adhesion molecule 1 (VCAM-1), which is found in high levels in inflamed endothelial cells but remains low in healthy cells. Once the peptide finds the molecule, it delivers the miR-92a inhibitor directly to the damaged cells.

The team has tested the nanomedicine in a mouse model and found that it reduces the size of vascular lesions. They also found that the treatment inhibited stenosis, the remodeling of vascular tissue that causes it to close off.

Link: https://www.eurekalert.org/news-releases/937040

Today's research materials report on a solid correlation between cataract surgery to restore vision and lower risk of later dementia. This provides support for the view that a reduced flow of sensory information to the brain accelerates the onset of neurodegeneration and loss of function with age. This is quite distinct from the usual set of underlying biochemical processes that are investigation in connection with cognitive decline and dementia: the accumulation of molecular waste in the brain; the chronic inflammation of brain tissue; the loss of mitochondrial function; the dysfunction of the vascular system leading to lesser delivery of oxygen and nutrients to an energy-hungry tissue; and so forth. In addition to all of these, laid atop the foundation of a failing biology, there is good evidence for a "use it or lose it" view of the aging brain.

In the past, researchers have found correlation between age-related retinal degeneration (and consequent vision loss) and dementia, and between and age-related deafness and dementia. There is considerable discussion in the research community regarding the causes of the latter association. Is it that brain networks thrive on input, and deafness reduces that input, or is it that common processes of aging damage both the brain and the sensory hair cells of the inner ear? Looking at the surgical reversal of cataracts sidesteps the question of common age-related mechanisms, and supports the view that there is a causal relationship between lack of input to the brain and the pace of progression towards neurodegeneration and loss of cognitive function.

Study: Cataract surgery linked with lessened dementia risk

The Adult Changes in Thought (ACT) study is a long-standing, Seattle-based observational study of more than 5,000 participants older than 65. Based on the longitudinal data of over 3,000 ACT study participants, researchers have now found that subjects who underwent cataract surgery had nearly 30% lower risk of developing dementia from any cause compared with those who did not. This lowered risk persisted for at least a decade after surgery. Cataract surgery was also associated with lower risk of Alzheimer disease dementia specifically. The mechanisms by which cataract surgery and lessened dementia risk are associated was not determined in this study. Researchers hypothesize that people may be getting higher quality sensory input after cataract surgery, which might have a beneficial effect in reducing the risk of dementia.

Association Between Cataract Extraction and Development of Dementia

Twenty percent of adults older than 65 years in the United States experience significant sensory impairment, such as vision or hearing loss, even with correction. Addressing sensory loss that affects a substantial portion of older adults may be a potentially modifiable risk factor for dementia in late life. Because sensory impairments and dementia are both strongly associated with aging, more knowledge about the association between sensory impairment and dementia may have important implications for individual and global public health, particularly if interventions to improve sensory function reduce dementia risk.

Visual impairment is an important dementia risk. Cataract is a leading cause of blindness worldwide, affecting more than 35 million people globally and causing blindness in approximately 20 million. Cataract affects most older adults at risk of dementia. However, there are conflicting results regarding the association between cataract extraction and cognitive impairment or dementia.

We hypothesized that older adults with cataract who undergo cataract extraction may have a lower risk of developing dementia compared with participants who do not undergo cataract surgery or participants who undergo other eye procedures that do not restore vision, such as glaucoma surgery. Previous studies exploring this association have been limited by small sample sizes, cross-sectional designs, and varying qualities of dementia assessment. More importantly, these studies have failed to account for healthy patient bias (i.e. when surgery is more likely in healthier individuals with the same cataract severity).

In total, 3038 participants were included, with mean age at first cataract diagnosis of 74.4 years. Based on 23,554 person-years of follow-up, cataract extraction was associated with significantly reduced risk (hazard ratio, 0.71) of dementia compared with participants without surgery after controlling for years of education, self-reported White race, and smoking history and stratifying by apolipoprotein E genotype, sex, and age group at cataract diagnosis. Similar results were obtained in marginal structural models after adjusting for an extensive list of potential confounders. Glaucoma surgery did not have a significant association with dementia risk. Similar results were found with the development of Alzheimer's disease dementia.

The consensus on heterochronic parabiosis, in which the circulatory systems of an old animal and young animal are joined, is that the old mouse exhibits reduced measures of age because harmful factors in old blood are diluted, not because beneficial factors are present in young blood. Nonetheless, there may still be some beneficial factors in young blood. Researchers here provide evidence for serum from young mice to improve muscle regeneration when injected into old mice, and argue that this is based on levels of klotho present in extracellular vesicles. Since the use of extracellular vesicles in the development of therapies is quite advanced, and several companies are developing therapies based on delivery of recombinant klotho, there are obvious paths forward to further assess this approach.

The new study builds on decades of research showing that when old mice are given blood from young mice, youthful features are restored to many cells and tissues. But until now, it was unclear which components of young blood confer these rejuvenating effects. Researchers collected serum, the fraction of blood that remains after removing blood cells and clotting factors, from young mice and injected it into aged mice with injured muscle. Mice that received young serum showed enhanced muscle regeneration and functional recovery compared to those that received a placebo treatment, but the serum's restorative properties were lost when extracellular vesicles (EVs) were removed, indicating that these vesicles mediate the beneficial effects of young blood.

Delving deeper, the researchers found that EVs deliver genetic instructions, or mRNA, encoding the anti-aging protein Klotho to muscle progenitor cells, a type of stem cell that is important for regeneration of skeletal muscle. EVs collected from old mice carried fewer copies of the instructions for Klotho than those from young mice, prompting muscle progenitor cells to produce less of this protein. With increasing age, muscle doesn't heal as well after damage because scar tissue is deposited instead of restoring original muscle structure. In earlier work, the team showed that Klotho is an important regulator of regenerative capacity in muscle progenitor cells and that this protein declines with age.

The new study shows for the first time that age-related shifts in EV cargo contribute to depleted Klotho in aged stem cells, suggesting that EVs could be developed into novel therapies for healing damaged muscle tissue.

Link: https://www.eurekalert.org/news-releases/936590

Following on the heels of the formation of Altos Labs, NewLimit is another well capitalized project focusing on in vivo reprogramming as a path to rejuvenation therapies. Given the sizable funding involved, it seems that reprogramming will be quite extensively explored in the decade ahead. Most of the questions we have now will likely be answered: can the risk of cancer be managed; how will reprogramming be conducted safely and efficiently in tissues consisting of different cell types with different reactions to the Yamanaka factors; will rejuvenation be largely limited to mitochondrial function, or will other sizable changes emerge as a result of resetting epigenetic marks; and so forth. I don't think that there is any expectation that reprogramming will do well with metabolic waste, and localized excesses of metabolic waste are a major component of degenerative aging. But we shall see.

NewLimit will start by deeply interrogating epigenetic drivers of aging and developing products that can regenerate tissues to treat specific patient populations. We will start by using primary human cells and reference species to develop machine learning models on what chromatid features change with age, which of these changes may be causal to the aging process, and finally develop therapies that could slow, halt, or reverse this process.

You can take a skin cell from an old mouse and clonally turn it into a newborn mouse with an entire life ahead of it. Remarkably, to accomplish this magic, you only treat the cells with four types of proteins. In a system as complex as mammalian biology, with billions of DNA base pairs and tens of thousands of proteins, all it takes is dosing four proteins for a couple weeks to completely change what the cell "is". NewLimit plans to initially focus on this mechanism: epigenetic reprogramming. Put simply, we want to figure out a way to restore the regenerative potential we all had when we were younger, but somehow lost.

We've raised $105 million initially from the founders to help get the company off the ground, with additional funding available upon reasonable progress. We expect capital will not be the limiting factor for the next few years. We may raise external funding as well down the road.

Link: https://blog.newlimit.com/p/announcing-newlimit-a-company-built

Something to bear in mind about aging is that while there is a good catalog of mechanisms and processes, it is rarely clear as to how much of any specific manifestation of degenerative aging is due to process A versus process B. The only way to find out is to remove or repair one of the mechanisms of aging in isolation, and see what results. Until quite recently, the only tools that could change the pace of aging involved upregulation of stress response mechanisms, such as via calorie restriction. These approaches produce sweeping changes in metabolism and all processes related to aging. Now, however, senolytic drugs allow researchers to remove only the contribution of senescent cells to aging, and that such a technology exists is the only reason that we know anything about the relative importance of senescent cells to various diseases of aging.

There is no particular reason that the relative importance of a process of aging should stay the same throughout the aging process. Most of the study of aging in animals involves looking at late life outcomes, where damage and dysfunction is extensive. Early adult aging remains more of a mystery, particularly since the effects are in most cases comparatively small, and thus harder to measure. Skin aging is one of the more noticeable early manifestations of aging, but there is all too little that can be said concretely about how the measurable aspects of skin aging from 20 through to 50 connect to the underlying molecular damage of aging, much of which is only accumulating quite slowly in that first half of adult life. Senescent cells in particular are not expected to be present in large enough numbers to produce strikingly harmful effects until quite late in life.

How good is the evidence that cellular senescence causes skin ageing?

Research in recent years has convincingly proven that cell senescence is a pathophysiologically relevant cause of age-associated multimorbidity and functional losses. There is good evidence that senescent cells accumulate in essentially all compartments of the skin during ageing, not only in sun-exposed skin but also during intrinsic ageing of sun-protected skin. A recent systematic review finds a significant association between senescent cell abundance in skin and donor age. However, the present knowledge about senescence accumulation during ageing in important cell types in the skin is incomplete and, for some cell types, non-existent.

A study with 9 patients with diabetic kidney disease recently showed that a short systemic intervention with the senolytic combination of Dasatinib and Quercetin can reduce frequencies of senescent cells (assessed as p16INK4a- and p21WAF1/CIP1-positive cells) not only in adipose tissue but also in the epidermis, together with a reduction in circulating senescence-associated secretory phenotype (SASP) factors. However, effects on skin function or quality were not reported.

Interventions aimed at improving aged skin function in humans so far relied on more indirect measures to reduce skin cell senescence. Dermabrasion is known to promote collagen remodeling and re-epithelialisation. In a small study with geriatric volunteers, it reduced frequencies of senescent fibroblasts in the upper dermis, increased papillary thickness, upregulated IGF1 expression and improved the UVB response in sun-protected aged skin. Senescent fibroblasts in the upper dermis were shown to enhance melanin production and drive skin hyperpigmentation in vitro and ex vivo. Accordingly, 10 volunteers with senile lentigo were treated with microneedle radiofrequency for 6 weeks, which reduced both frequencies of p16INK4a-positive cells in the upper dermis and epidermal pigmentation in the treated area.

More recently, a small randomized prospective clinical trial was performed to test whether topical application of rapamycin in low concentration could reduce senescence markers and improve function and appearance of photoaged skin. Topical rapamycin reduced the expression of p16INK4a consistent with a reduction in cellular senescence. This change was accompanied by an improvement in clinical appearance of the skin and histological markers of aging and by an increase in collagen VII, which is critical to the integrity of the basement membrane.

In conclusion, there is a good amount of pre-clinical and clinical data showing a strong positive correlation between reduction of senescent cells frequencies and functional improvement of skin. Whether senescence of skin cells makes a significant causal contribution to skin ageing can still not be conclusively decided, however. Nonetheless, there is strong evidence existing today to assume that better understanding of cell senescence in skin may lead to a breakthrough in interventions into skin ageing.

As researchers note here, there is evidence for exercise to slow retinal aging and the progression of conditions involving retinal degeneration. Exercise affects many aspects of aging, not to the same degree as the practice of calorie restriction, but likely through an overlapping set of mechanisms related to cellular stress response upregulation, including increased autophagy and mitochondrial quality control. There is is a vast forest of interacting metabolic changes to explore, however, and the research community has yet to come to a solid grasp of which of the effects of exercise are the most relevant in any given tissue type in the body.

Physical activity and exercise have long been known to be beneficial to the human body. The benefits of exercise range from being critical for maintaining health and wellbeing, to ameliorating and preventing disease pathogenesis. Exercise has been demonstrated to improve the pathology of several chronic diseases including cardiovascular disease, type 2 diabetes, obesity, and cancer. Regular exercise is now also being "prescribed" at a clinical level as a non-pharmacological therapeutic intervention for complex neurodegenerative diseases such as Alzheimer's disease (AD) and Parkinson's disease (PD). Ultimately this begs the question: Is exercise actually beneficial, or is mammalian physiology not evolutionarily suited to lead a sedentary lifestyle?

Given the broad beneficial effects of exercise observed across disorders of the central nervous system (CNS), it is assumed that exercise provides similar non-pharmacological benefits to retinal degenerative diseases including, but not limited to, diabetic retinopathy (DR), retinitis pigmentosa (RP), glaucoma, and age-related macular degeneration (AMD). These complex neurodegenerative diseases all have varying pathophysiological properties and given these and the limited therapeutic options available, the benefits of exercise in potentially mitigating retinal disease pathologies may be of considerable interest in the field of ophthalmology.

There has been some clinical data that demonstrates both the preventative and rehabilitative effects of exercise to retinal health. Physical activity has been shown to both lower the risk of AMD development and improved visual outcomes. Further, fundamental research into exercise using pre-clinical animal models has demonstrated protection against retinal degeneration including in glaucoma, DR, RP, and AMD. A major question is what is happening at the molecular level in exercise to provide this protection to retinal degeneration? Although the evidence for exercise being of benefit to human physiology is clear, the underlying molecular mechanisms underpinning its benefit, particularly in the CNS, remain largely unknown.

Link: https://doi.org/10.1111/ceo.14023

Researchers here analyze epidemiological data to find that cardiovascular disease patients have a better prognosis the more that they exercise. In terms of improved health, cardiovascular disease patients can achieve greater relative mortality reductions from higher levels of exercise than is the case for healthy individuals, which is an interesting finding. As always, it is worth remembering that this data shows correlation rather than causation. Animal studies make it clear that exercise is beneficial, but in human data there is room to argue that other factors are at work, such as the possibility that people with less severe cardiovascular disease (and thus lower mortality risk) will tend to exercise more than those with worse cardiovascular disease (and thus worse mortality risk).

There is debate to whether cardiovascular health status affects the dose-response association between physical activity (PA) and health outcomes. Studies among patients with cardiovascular diseases (CVDs) found different associations between PA and mortality reductions, which were described as linear, J shaped, or U shaped.

A cohort study (median follow-up 6.8 years) was performed comparing the association between moderate to vigorous physical activity (MVPA) and incident major adverse cardiovascular events (MACE) and all-cause mortality between healthy individuals (n = 112,018), individuals with cardiovascular risk factors (CVRF) (n = 27,982), and CVD (n = 2,493). The shape of dose-response association between MVPA and cardiovascular events and death is curvilinear for healthy individuals and those with CVRF, whereas a linear relationship was found in individuals with CVDs. The association between MVPA and the risk of CVD or mortality is domain specific as leisure activities were associated with the most benefits, nonleisure activities with little benefits, and occupational activities with no benefits.

In conclusion, MVPA is associated with risk reductions in all groups, but, especially, CVD patients should be encouraged that "more is better" regarding PA. PA recommendations could be optimized by taking cardiovascular health status and the domain of MVPA into account.

Link: https://doi.org/10.1371/journal.pmed.1003845

David Sinclair works on areas of mitochondrial metabolism relevant to aging, sirtuins and NAD, and of late is involved in research into a novel understanding of the relationship between DNA repair and age-related epigenetic change, as well as the use of in vivo reprogramming as a way to reverse age-related epigenetic change. He is first and foremost an excellent self-promoter, however, a job that has come to includes authoring books such as Lifespan.

On balance, self-promotion seems a useful trait for people who work on projects of merit. It is a tough job to raise funds and build the necessary networks of allies to push forward the bounds of any field; every advantage helps. It is not such a good trait when the projects themselves are not useful. Self-promoters have a way of cluttering the road to clear debate and understanding, and Sinclair's work is a mixed bag when it comes to utility as the basis for treatments for aging. That said, I think it unlikely that Altos Labs would exist in its present form, devoting a sizable budget - hundreds of millions initially - towards in vivo reprogramming as an approach to the treatment of aging, absent Sinclair spending the last few years aggressively publicizing his work on reprogramming to everyone who would listen. Fortunately, and unlike everything else Sinclair has worked on and relentlessly publicized to date, in vivo reprogramming is an area of research that might turn out to produce a meaningful degree of rejuvenation in old people.

Unfortunately, this still means that one should take everything Sinclair says outside a peer reviewed scientific paper as propaganda, a matter of talking up his position and enabling the companies he is involved in to raise funds and find exits. Self-promotion is a game in which one can win every battle and still lose the war, as people come to filter everything one says through the lens of self-interest and then disregard it. Perhaps Sinclair believes in the position he puts forward in the book Lifespan, perhaps not, but to present epigenetic change as the whole of aging - which it is most certainly not, and may not even be that close to the root causes - is just too convenient given his portfolio of interests. Maybe he is a true believer in his own work, and that explains it all, but this is also the person who talked up the dead end of sirtuins and resveratrol in exactly the same way fifteen years ago. He overhypes everything that he is earnestly involved in.

I have no horse in this race, beyond a desire to see meaningful progress towards rejuvenation in my lifetime. I've never met the man. It is good that Sinclair is now putting earnest effort into a potential road to therapies - in vivo reprogramming - that might actually have some promise when it comes to human rejuvenation, and has persuaded others with significant resources to do the same. I do wish he would temper the way in which he publicizes and promotes his work, however. It think that it harms long-term prospects for the field more than it helps.

Separately, and to the content of the review here, it is always interesting to see people coming in from the outside the field and describing their confusion on encountering the various competing views of aging and possible paths to the treatment of aging. The confusion is only exacerbated by the degree to which various parties present narrow views of aging, or present their narrow view of aging as the whole of the picture, or leave out inconvenient points that undermine their position. This sort of thing is rife in the scientific literature, and worse in popular science materials.

Book Review: Lifespan

David Sinclair - Harvard professor, celebrity biologist, and author of Lifespan - thinks solving aging will be easy. "Aging is going to be remarkably easy to tackle. Easier than cancer" are his exact words, which is maybe less encouraging than he thinks. Sinclair thinks aging is epigenetic damage. As time goes on, cells lose or garble the epigenetic markers telling them what cells to be. Kidney cells go from definitely-kidney-cells to mostly kidney cells but also a little lung cell and maybe some heart cell in there too. It's hard to run a kidney off of cells that aren't entirely sure whether they're supposed to be kidney cells or something else, and so your kidneys (and all your other organs) break down as you age. He doesn't come out and say this is literally 100% of aging. But everyone else thinks aging is probably a combination of many complicated processes, and I think Sinclair thinks it's mostly epigenetic damage and then a few other odds and ends that matter much less.

Epigenetic damage could potentially still be unfixable: how do you convince the thousands of different intermixed cell types in the body to all be the right type again? But Sinclair thinks the body already has a mechanism for doing this: epigenetic repair proteins called sirtuins. Sirtuin activity seems to be regulated by a protein called mTOR, which can be influenced by treatments such as rapamycin, an mTOR inhibitor. The other pill is nicotinamide riboside aka NR (and its close cousin nicotinamide mononucleotide aka NMN). The reactions catalyzed by sirtuins involve nicotinamides, and the more nicotinamides you have, the more effective sirtuins are.

People who are not David Sinclair generally don't expect conquering aging to be this easy. The anti-aging SENS Research Foundation has a list of seven different programs to address what they consider to be seven different causes of age-related damage. This seems more like the "humans are like cars" scenario where you have to fix every part individually and it's really hard. People who are not David Sinclair don't think that nicotinamides are a miracle drug. A well-regarded research center ran a big study on nicotinamides in mice and found that they lived no longer than usual, although they did seem to be healthier in various ways. And people who are not David Sinclair are less enthusiastic about sirtuins, mTOR, and calorie restriction.

My impression of the consensus in anti-aging research is that many people are excited for the same reasons Sinclair is excited, that people are much more optimistic than they were five or ten years ago - but that their level of optimism hasn't quite caught up to Sinclair's level yet.

Researches here identify an interesting component of the detrimental changes that take place in heart tissue with age and dysfunction, leading to heart failure. Elastic proteins in the heart are produced in stiffer forms, leading to reduced function, and rebalancing the regulation of this system can improve the pumping of the failing heart. AS an intervention, this appears to be some way downstream from deeper causes, such as the accumulation of senescent cells in heart tissue. As is often the case, it is hard to draw a line of cause and effect leading from the fundamental underlying damage of aging to this alteration in the production of elastic proteins. Researchers tend to work backwards from the end state of an aged tissue, and stop at the first approach they find that might work, which is why most research does not lead to therapies that target root causes.

Patients with heart failure often have shortness of breath and become fatigued quickly. As people age the number of adverse factors increase, so heart failure primarily affects older people, especially women. Although the symptoms are similar, there are various causes. In one form of the condition the pumping function of the heart is impaired. This can however be improved with widely available medication. In the other form, the heart pumps with adequate force, but the chambers of the heart - the ventricles - fail to fill properly because the ventricular walls become thickened or stiff. There is currently no effective therapy for this form of heart failure.

The mechanics of the heart depend on an elastic giant protein called titin. It is produced by heart muscle cells in distinct variants or isoforms that differ in their flexibility. While very elastic titin proteins predominate in infants, later when growth and remodeling are completed, stiffer titin isoforms are produced to increase pumping efficiency. In heart failure with preserved ejection fraction, thickened heart walls, intercalated connective tissue, and stiffer titin filaments may lead to impaired filling of the ventricles.

"The mechanical properties of titin proteins are difficult to adjust. But we can now intervene in the process preceding protein synthesis - that is alternative splicing. Alternative splicing is a clever trick that nature has devised to create a variety of similar proteins based on a single gene - including the different forms of titin. This process is controlled by splicing factors. One of these, the master regulator RBM20, is a suitable target that we can address therapeutically."

Researcher have found a way to influence RBM20 with antisense oligonucleotides (ASOs). These are short chains of single-stranded nucleic acids that are synthetically produced. They bind specifically to the complementary RNA sequence, the blueprint of the targeted protein, thereby blocking its synthesis. Researchers successfully tested the ASOs in mice with stiffer heart walls. Researchers were able to stabilize the ASOs in such a way that they reach the striated muscles in the mouse model and are not already degraded in the blood, liver, or eliminated by the kidneys. Most of the therapeutic winds up in the heart, with some entering the skeletal muscle. Heart failure is a chronic disease that requires long-term treatment. "So we treated our mice over a longer period of time and were able to see lasting treatment effects."

Link: https://www.mdc-berlin.de/news/press/how-fill-heart

Venture funds dedicated to the longevity industry are growing in size and number. While all too much of the industry is focused on approaches, such as the development of calorie restriction mimetic drugs, that cannot possible produce sizable effects on human life span, and which are unlikely to even be as beneficial as regular exercise, a rising tide lifts all boats. Seed funding is easy to find for most ventures, given the broad support for slowing and reversing aging present in many wealthy circles, but it remains the case that raising a series A round of $10M or more is more challenging than it should be. It requires talking to biotech and pharma funds that (a) do not yet understand the treatment of aging as a field and (b) are notoriously conservative, unwilling to step outside their comfort zones. Filling that gap would accelerate progress over the next decade.

Apollo Health Ventures announces the final closing of its second venture fund to build a portfolio of data-driven biotechnology and health tech ventures aimed at extending human healthspan. The oversubscribed Apollo Health Ventures Fund II successfully raised $180 million to invest in both venture creation as well as externally sourced deals.

Advances in understanding the biology of aging coupled with emerging technologies have significantly increased pre-symptomatic detection of age-related damage and dysfunction, paving the way for novel interventions. Apollo Health Ventures' investments focus on companies targeting well-validated aging pathways with the aim of, for example, maintaining overall cellular health and fitness, reducing tissue damage caused by chronic inflammation, or restoring a healthy immune system to provide more resilience and protection against diseases.

Apollo Health's predecessor fund has successfully built and invested in companies developing differentiated therapeutics against age-related disorders demonstrating the firm's leadership and understanding of this therapeutic area. Portfolio companies from the fund include Aeovian Pharmaceuticals, a company developing a safer version of rapamycin, a drug which has been shown to extend healthspan as well as lifespan in several animal models. Apollo has also co-founded Samsara Therapeutics, the world's largest discovery platform developing autophagy-enhancing molecules covering a broad range of therapeutic indications.

Link: https://www.apollo.vc/post/apollo-health-ventures-closes-180-million-fund

You'll recall that a collection of research groups and companies are working to assess the benefits of alpha-ketoglutarate supplementation. The results reported to date focus exclusively on outcomes in epigenetic age assessment, using a proprietary clock algorithm that is not yet open to inspection or analysis. The open access paper I'll point out today is the formal publication of the results announced earlier this year. Since no other information on patient outcomes beyond epigenetic age is provided - such as, for example, measures of inflammation, immune health, and so forth - this data is essentially of no value whatsoever. The earlier mouse studies were more informative! We cannot even speculate as to what this particular epigenetic clock is measuring. Not that we could do much better given the clock algorithm, once it is published: it is presently impossible to make more than sketchy reasoned guesses at what fully described epigenetic clocks such as GrimAge are actually measuring.

Since epigenetic clocks are discovered in epigenetic data via machine learning processes, at present no-one knows how or why the identified characteristic epigenetic changes arise with age. Thus no-one can guess in advance as to how a specific epigenetic clock will react to any given intervention that affects only a subset of the processes of aging. To be useful as a means of rapidly assessing whether or not a given intervention is actually producing rejuvenation, an epigenetic clock must be first calibrated against that intervention by running life span studies in mice. Alternatively it must be established as to exactly how these epigenetic marks relate to underlying processes and consequences of aging. The former is an easier task, but still an expensive one.

Cynically, it is clear that people in the marketing-dependent supplement space are going to skip the question of understanding in favor of simply shopping for large numbers. They are going to run different clocks against all of the cheap, low-yield approaches known to upregulate cellular stress responses or reduce inflammation and publicize the largest reduction in epigenetic age regardless of the merits of the approach and the clock. There will be a lot of this sort of thing going on in parallel to more responsible work that is focused on gathering enough data to start to say something useful about how these epigenetic clocks work. The mark of a responsible study is, I think, the presence of a lot of other comparison data from study participants, such as measures of frailty, inflammation, and other markers of aging and age-related disease. That is clearly not the case in this paper.

Rejuvant, a potential life-extending compound formulation with alpha-ketoglutarate and vitamins, conferred an average 8 year reduction in biological aging, after an average of 7 months of use, in the TruAge DNA methylation test

The epigenetic clock is an attractive biomarker of aging because it applies to most human tissues, capturing aspects of biological age such as frailty, cognitive/physical fitness in the elderly, age-acceleration in obesity, and lifetime stress. Markers of biological aging represent an important tool to clinically validate the effects of longevity-based interventions. For the first time, these biomarkers of aging give scientists the opportunity to study the effects of anti-aging compounds in real-time and directly in humans. We utilized the TruAge prediction model with Sanger sequencing for DNA methylation analysis. In total, 3 genes including 9 CpG sites were analyzed by the Sanger sequencing. The DNA methylation values obtained for all CpG sites were included in the TruMe age-prediction model (pending publication).

Alpha-ketoglutarate (AKG) is an endogenous intermediary metabolite in the Krebs cycle whose levels naturally decline during aging. AKG is involved in multiple metabolic and cellular pathways. These include functioning as a signaling molecule, energy donor, precursor in the amino acid biosynthesis, and a regulator of epigenetic processes and cellular signaling via protein binding. AKG deficiency in stem cells and progenitor cells increases with age. As animals age, mitochondrial function is progressively impaired and cellular metabolic flux in the mitochondria declines, which exacerbates AKG deficiency. It was reported that AKG increased the lifespan of C. elegans.

Building on these results, AKG (and calcium salt) combined with other Generally Recognized as Safe (GRAS) compounds were studied in mice. The non-genetically altered mouse is the preferred mammalian model to study aging, since the biochemical processes involved in mice aging may apply to other mammals, including humans. In a recent study, sponsored by Ponce de Leon Health and performed at the Buck Institute for Research on Aging, the effect of alpha-ketoglutarate (delivered in the form of a calcium salt - CaAKG) on healthspan and lifespan in C57BL/6 mice was reported. The authors showed that in the mice, AKG reduced frailty and enhanced longevity, indicating a compression of morbidity. These and other discoveries suggest that AKG may be an ideal candidate for pro-longevity human studies.

Herein we report a retrospective analysis of DNA methylation age in 42 individuals taking Rejuvant, an alpha-ketoglutarate based formulation, for an average period of 7 months. DNA methylation testing was performed at baseline and by the end of treatment with Rejuvant supplementation. Remarkably, individuals showed an average decrease in biological aging of 8 years using the TruMe age-prediction model. Furthermore, the supplementation with Rejuvant is robust to individual differences, as indicated by the fact that a large majority of participants decreased their biological age. Moreover, we found that Rejuvant is of additional benefit to chronologically and biologically older individuals. While continued testing, particularly in a placebo-controlled design, is required, the nearly 8-year reversal in the biological age of individuals taking Rejuvant for 4 to 10 months is noteworthy, making the natural product cocktail an intriguing candidate to affect human aging.

It is plausible that the mitochondrial dysfunction characteristic of aging increases the pace at which cells become senescent, and harms the efforts of immune cells to remove senescent cells. With age, the burden of senescent cells rises in tissues throughout the body. This is likely an imbalance between the pace of creation and pace of destruction. Regardless, when even a small fraction of the cells in a tissue are senescent, the inflammatory signals they produce become disruptive of tissue function and structure. The open access review here is more focused on the question of how mitochondrial function is changed as a result of the senescent state, however, and whether targeting mitochondrial function can be of benefit, such as by suppressing some of the more harmful aspects of senescence.

Mitochondria are one of organelles that undergo significant changes associated with senescence. An increase in mitochondrial size is observed in senescent cells, and this increase is ascribed to the accumulation of dysfunctional mitochondria that generate excessive reactive oxygen species (ROS). Such dysfunctional mitochondria are prime targets for ROS-induced damage, which leads to the deterioration of oxidative phosphorylation and increased dependence on glycolysis as an energy source. Based on findings indicating that senescent cells exhibit mitochondrial metabolic alterations, a strategy to induce mitochondrial metabolic reprogramming has been proposed to treat aging and age-related diseases.

In this review, we discuss senescence-related mitochondrial changes and consequent mitochondrial metabolic alterations. We assess the significance of mitochondrial metabolic reprogramming for senescence regulation and propose the appropriate control of mitochondrial metabolism to ameliorate senescence. Learning how to regulate mitochondrial metabolism will provide knowledge for the control of aging and age-related pathologies. Further research focusing on mitochondrial metabolic reprogramming will be an important guide for the development of anti-aging therapies, and will provide novel strategies for anti-aging interventions.

Link: https://doi.org/10.3390/cells10113003

Delivery is the largest challenge in the ongoing development of gene therapy: how to put enough of a vector into the target tissues without sending too much of it elsewhere in the body, particularly the liver, which is where much of every injected substance tends to end up. This is a big issue for systemic administration of gene therapies intended to affect much of the body, given severe side-effect and deaths that have occurred in human trials at high doses of viral vectors. A greater ability to target specific tissues means that a lower dose can be used, and thus off-target effects produced by the vector itself are minimized. The AAV approach noted here is an order of magnitude better than the standard serotypes when it comes to preferentially targeting muscle tissue. That seems to me a big deal, enough to enable systemic delivery of AAV-based therapies at doses far below those at which toxicity and deaths have occurred in human trials.

Recombinant adeno-associated viruses (rAAVs) are the most commonly used vehicles for in vivo gene replacement therapy and gene editing in preclinical and clinical studies, yet selective transduction of specific tissues after systemic delivery remains a challenge. Recombinant AAVs generated using naturally occurring capsids are predominantly sequestered in the liver after systemic injection. This sequestration limits the efficiency of transduction in other organs and poses a particular challenge for gene delivery to skeletal muscle. Because muscle comprises up to 40% of total body mass, achieving therapeutic thresholds in muscle with natural capsid variants requires extremely high virus doses (~2E+14 vg/kg), which creates a formidable hurdle for vector manufacturing and can result in therapy-limiting toxicity, as observed in some recent clinical trials.

Here, we developed the DELIVER (directed evolution of AAV capsids leveraging in vivo expression of transgene RNA) strategy to combine diverse capsid library generation with stringent transcript-based in vivo selection and to enable directed evolution followed by identification of functional capsid variants in any tissue of interest and any animal model. We apply DELIVER to develop muscle-tropic capsids (MyoAAV) in mice and non-human primates (NHPs) and compare our results to AAV9 and AAVrh74, both of which are naturally occurring AAV capsids currently used in gene replacement trials for Duchenne muscular dystrophy (DMD).

Quantification of in different skeletal muscles of male and female C57BL/6J mice revealed 10 to 29 times higher transgene expression in muscles of MyoAAV-injected compared to AAV9-injected mice. Expression was 6.3 times higher in the heart and 2.8 times lower in the liver of MyoAAV injected animals. Notably, improved transduction efficiency by MyoAAV was restricted to striated muscle tissues, and this engineered capsid variant transduced the lung, kidney, spleen, and brain of injected animals with similar or lower efficiency compared to AAV9. We anticipate that adoption of DELIVER to additional tissue and organ systems will have a far-reaching impact in accelerating the development and translation of gene therapy and other genomic medicine approaches for a variety of human diseases.

Link: https://doi.org/10.1016/j.cell.2021.08.028

An overly simplistic view of the lymphatic system is that it is network of highways and collaboration centers for the cells of the immune system. Immune cells use lymphatic vessels to travel about the body, while the hundreds of lymph nodes scattered throughout the lymphatic system are important locations at which immune cells exchange information about signatures of infection and damage, managing the immune response. Like all tissues, lymph nodes are structured in certain ways, and that structure is degraded by the processes of aging. Lymph nodes become fibrotic, for example, and these changes impede the activities of immune cells.

There is evidence to suggest that the degenerative aging of lymph nodes places limits on the ability of the immune system to respond effectively to threats, distinctly from other causes of immune aging. For example, a study of thymic regrowth in very old animals showed that the additional T cells produced in a regrown thymus did not lead to an improved immune response to infectious disease. That work implicated lymph node dysfunction as the cause of this undesirable outcome. Interestingly, cellular senescence is implicated in the fibrosis found disrupting the structure of aged lymph nodes; a study on whether senolytic treatments, aimed at removing those senescent cells, could help to reverse some of the detrimental changes that take place in lymph nodes might produce interesting results.

Aging-Related Cellular, Structural and Functional Changes in the Lymph Nodes: A Significant Component of Immunosenescence? An Overview

Even during healthy aging, the functions of the immune system may be weakened by a process known as immunosenescence. Immunosenescence and inflammaging are responsible for the increasing incidence of infections, autoimmune diseases, and neoplasms in the population over 65. Older adults also show weaker responses to vaccination than younger ones. Aging causes adverse changes in the innate and adaptive parts of the immune system, the microenvironment of lymphoid organs where immune cells develop and reside, and the equilibrium of soluble chemokines and cytokines, all responsible for the functioning and homeostasis of the immune system. Aging-associated changes in the primary lymphoid organs, i.e., bone marrow and thymus, have been thoroughly characterized; however, data on aging of the secondary lymphoid organs, e.g., lymph nodes, is still incomplete and requires extensive discussion.

Lymph nodes play a pivotal role in the innate and adaptive immune response to natural antigens and vaccines. Lymphatic vessels direct lymph from the tissues to the lymph nodes scattered throughout the body. As lymph passes through the lymph node parenchyma, antigens come into contact with the effector cells of the adaptive immune system, initiating a cascade of immune processes that enable the recognition and neutralization of foreign antigens and pathogens. Immune cell migration to the lymph node in response to self or foreign antigens exposure relies on the coordinated functioning of adhesion molecules on the surface of leukocytes and venule endothelial cells. Such migration plays a fundamental role in regulating physiological processes, e.g., wound healing and angiogenesis, and pathological phenomena, e.g., inflammation and tumor cell filtration.

The number of lymph nodes in the human body ranges from 300 to 500, and their total weight is about 100 grams. Studies have shown that the number of nodes decreases with age, and aging-associated degenerative features emerge in the lymph nodes, such as fibrosis, lipomatosis, a reduction in the number of postcapillary vessels, and changes in the morphology and function of the specialized endothelial cells lining the venous capillaries. Consequently, the amount of lymphoid tissue in the cortical and medullary zones of lymph nodes is reduced, as is the number and size of germinal centers in lymphoid follicles. These changes result in a reduced reactivity to antigen challenge. The number of follicular dendritic cells also decreases, and the ability to uptake and retain immune complexes is significantly impaired. These deficits result in decreased humoral immunity associated with impaired antibody production in the elderly and an increased susceptibility to infections, one of the leading causes of morbidity and mortality in people over 65

The aging of lymph nodes results in decreased cell transport to and within the nodes, a disturbance in the structure and organization of nodal zones, incorrect location of individual immune cell types and impaired intercellular interactions, as well as changes in the production of adequate amounts of chemokines and cytokines necessary for immune cell proliferation, survival and function, impaired naïve T-cell and B-cell homeostasis, and a diminished long-term humoral response. Understanding the causes of these stromal and lymphoid microenvironment changes in the lymph nodes that cause the aging-related dysfunction of the immune system can help to improve long-term immune responses and the effectiveness of vaccines in the elderly.

This is old news for most of the audience here, but COVID-19 mortality is suffered largely by the old. An aged immune system greatly raises the odds of suffering the cytokine storm of runaway inflammation that leads to mortality. One of the characteristics of an aged immune system is a heightened level of chronic inflammatory signaling, a reaction to the damaged environment of aged tissue. As researcher here note, the presence of age-related chronic inflammation creates a vulnerability to the risk of much greater, excessive and unrestrained inflammation in response to infection.

Aging is characterized by the dynamic remodeling of the immune system designated "immunosenescence," and is associated with altered hematopoiesis, thymic involution, and lifelong immune stimulation by multitudinous chronic stressors, including the cytomegalovirus (CMV). Such alterations may contribute to a lowered proportion of naïve T-cells and to reduced diversity of the T-cell repertoire. In the peripheral circulation, a shift occurs towards accumulations of T-cell and B-cell populations with memory phenotypes, and to accumulation of putatively senescent and exhausted immune cells.

The aging-related accumulations of functionally exhausted memory T lymphocytes, commonly secreting pro-inflammatory cytokines, together with mediators and factors of the innate immune system, are considered to contribute to the low-grade inflammation (inflammaging) often observed in elderly people. These senescent immune cells not only secrete inflammatory mediators, but are also able to negatively modulate their environments. In this review, we give a short summary of the ways that immunosenescence, inflammaging, and CMV infection may cause insufficient immune responses, contribute to the establishment of the hyperinflammatory syndrome and impact the severity of the coronavirus disease 2019 (COVID-19) in elderly people.

Link: https://doi.org/10.3390/ijms222212539

This paper provide an interesting discussion of the interplay between oxidative stress, immune cell behavior, and raised inflammatory signaling in aging. Chronic inflammation is an important aspect of aging, disruptive of tissue and organ function throughout the body. Oxidative stress is the name given to a raised level of oxidative molecules present in and around cells, reacting with important proteins and other molecules to produce toxicity and disrupted function of cell components. This is also a noteworthy feature of aging. All aspects of aging interact with one another, and it is usually interesting to look into what is known of the details of any given interaction, as is done here.

The aging process can have multiple definitions depending on the perspective from which it is considered. From a biological point of view, the aging process may be defined as the progressive and general deterioration of the functions of the organism that leads to a lower ability to react to changes and preserve homeostasis adaptively. Homeostasis includes all processes that organisms use to actively maintain or adjust to appropriate conditions necessary for survival. Thus, although aging should not be considered a disease (it would be absurd to think of an illness that affects 100% of people), it is the main risk factor for the occurrence of chronic age-related diseases.

There are three physiological systems, the nervous, endocrine, and immune systems, in charge of maintaining body homeostasis. Moreover, these systems are in continuous communication, constituting a neuroimmunoendocrine system, which allows the preservation of homeostasis and, therefore, of health. With aging, there is a functional decline of these homeostatic systems and an impairment in the communication between them, which translates into a worse capacity to mount an adequate response to a variety of stressors. The decay of this capacity, which has also been referred to as decreased homeodynamic space or decreased homeostatic resilience, is what results in higher morbidity and mortality. Nevertheless, the age-related changes in these homeostatic systems are established at different rates in each subject, which translates into a different rate of aging or biological age of individuals with identical chronological age.

We believe that the rate at which these homeostatic systems decline relies on the establishment of a chronic oxidative and inflammatory stress situation. Thus, we describe how the oxidation inflammation theory of aging (oxi-inflamm-aging) is one of the most complete to describe how the process of aging occurs. Even though we are aware that the aging process is multifactorial, we propose mitochondrial reactive oxygen species (ROS) production as the first event involved in this process. In addition, we provide molecular mechanisms that link oxidation and inflammation and demonstrate how immune cells play an essential role in interconnecting both processes and, consequently, modulating the rate of aging. Accordingly, we show how the function and redox state of immune cells can be used as markers of the rate of aging of an individual allowing the prediction of lifespan. Moreover, to further confirm the role of immune cells in the aging process, we show, by modulating the redox and inflammatory state of immune cells and the production of oxidant and pro-inflammatory compounds by these cells, how different situations or conditions, such as the social environment, nutrition, and exercise, can have an impact on the lifespan of the organism.

Link: https://doi.org/10.3390/cells10112974

The aging of the immune system isn't just a matter of becoming vulnerable to commonplace infectious diseases, such as influenza. The immune system also removes senescent cells and cancerous cells, both of which present sizable risks to health in later life. Additionally, immune cells participate in normal tissue maintenance in a variety of ways. Further, the chronic inflammation characteristic of an aged immune system disrupts the normal function of many types of cell and tissue, contributing to a diverse range of age-related conditions.

For most people, cytomegalovirus (CMV) is an apparently innocuous persistent herpesvirus infection, one that presents no obvious symptoms. A good deal of evidence supports a sizable role for CMV in the age-related decline of the immune system into inflammatory overactivation (inflammaging) and incapacity (immunosenescence), however. Most people are exposed to CMV at some point during their lives, and the immune system is incapable of clearing this persistent virus. Over time, ever more T cells of the adaptive immune system become devoted to targeting CMV rather than taking on other threats, and may even become harmful themselves as result of too much replication in response to the presence of CMV In effect, CMV actively corrodes the ability of the adaptive immune system to defend the body from other threats.

In today's open access paper, researchers provide more supporting evidence for potentially detrimental changes in T cell populations to occur due to CMV infection in older individuals rather than due to aging per se. The specific change that is the focus of the paper is likely also protective, an attempt to contain CMV, that nonetheless results in pathology. It is unclear as to whether an approach to effectively clear CMV from the body would undo this damage naturally, or whether some way of removing the unwanted T-cells would be required to restore balance to the aged immune system. Both of these types of therapy are prospects for the foreseeable future, but it is fair to say that much more attention is given to the development of antivirals for persistent infections than is given to the targeted destruction of immune cells.

Functional Changes of T-Cell Subsets with Age and CMV Infection

T-cells are a major component of adaptive immunity, with a high degree of specificity in response to a pathogen challenge, enabling the host to mount a specific immune response and generate immunological memory. Therefore, for effective immune protection against the primary and subsequent challenges, these cells must be maintained in a unimpaired state and appropriately regulated. However, on aging, the immune system undergoes profound changes, loosely termed immunosenescence, that can affect the outcome of the immune response. The impact of these age-related changes on the immune system has been associated clinically with decreased efficacy of vaccines, an increase in the frequency and severity of infectious diseases, and an increased incidence of chronic inflammatory disorders. These alterations are associated with phenotypical and functional changes affecting a variety of immune cells, especially T-cells. It has been shown that chronic stimulation of the immune system, such as by persistent viral infections, associates with age-related alterations in the peripheral T-cell pool. Chronic infection especially by cytomegalovirus (CMV) has a dramatic influence on the T-cell compartment, both on CD8+ and CD4+ T-cells.

In humans, repetitive replication of T-cells is associated with the loss of CD28 and the acquisition of CD57. Thus, CD28- and CD57+ T-cells are considered to be late- or terminally differentiated T-cells characterized by low telomerase activity and shorter telomeres compared with CD28+CD57- T-cells. At least some of these CD28-CD57+ T-cells may be senescent. It has been shown that besides age, persistent CMV infection is also associated with the accumulation of these highly differentiated T-cells. Accumulating evidence supports a detrimental role of senescent T-cells in several chronic inflammatory clinical conditions, including cardiovascular diseases such as atherosclerosis and myocardial infarction.

Our results show that in middle-aged and older overtly healthy individuals, the main factor driving the expansion of CD57+ T-cells is CMV infection. However, from the fourth decade onwards, these cells do not accumulate further with age. In previous work, we showed that the percentage of CD8+CD57+ T-cells was similar between young and middle-aged CMV-seropositive individuals. Therefore, here, we extend our previous findings to show that CD57 expression by T-cells is not only a hallmark of CMV infection in young individuals but also at older ages. Accordingly, once CMV infection takes place, CD57+ T-cells will expand, and after that, their percentage will remain rather stable over time. Thus, our results argue against the consensus that the expansion of these cells is a sign of chronological aging.

Our results regarding CD4+CD57+ T-cell expansions with CMV infection are also in agreement with the observation that CMV, but not aging, has a significant effect on the expansion of pro-atherogenic CD4+CD28- T-cells. These cells (that also express CD57) are cytotoxic, capable of causing vascular damage, and their expansion is associated with autoimmune and cardiovascular disease. Higher frequencies of CD4+CD57+ T-cells have been associated with poorer prognosis in several diseases. In acute heart failure patients, high percentages of these cells are associated with the development of cardiovascular events (defined as heart failure-associated mortality, transplantation, or rehospitalization). In end-stage renal disease patients, the frequency of CD4+CD57+ T-cells is associated with atherosclerotic changes, and in multiple sclerosis, their frequency is associated with disease severity and poorer prognosis.

Therefore, immunological treatments should consider both age and CMV infection as a major factor. This strengthens the need for validation studies with not only the aim to present something novel but also to confirm findings in different populations. The association of these T-cell expansions with CMV infection and disease underlines the necessity of considering CMV serology in any study regarding immunosenescence and emphasizes that the price of immune protection is always some degree of immunopathology.

BDNF levels decline with age. Much of the focus on BDNF has been its role in neurogenesis in the brain. Interventions such as exercise and reversing (or compensating for) the aging of the gut microbiome can boost BDNF levels and cognitive function in animal studies. For a different view on the relevance of BDNF, researchers here report on their investigations of the role of BDNF in muscle tissue, finding that it can upregulate the mitochondrial quality control mechanism of mitophagy, improving muscle function. They also note that obesity can harm muscle tissue function by reducing BDNF levels and thereby causing a loss of mitochondrial function. This work is perhaps a good reason to pay more attention to some of the known ways to upregulate BDNF as a basis for therapies.

A decline in metabolism and endurance of skeletal muscle is commonly observed in obese patients, but the underlying mechanism is not well-understood. Researchers developed a special obesified mouse model by removing the gene of brain-derived neurotrophic factor (BDNF) exclusively in their skeletal muscle. BDNF is originally identified as an important growth factor for maintaining the survival and activities of neurons. Recent studies have proposed that BDNF is also a muscle-secreted protein (i.e., myokine), but its physiological significance is unknown.

Researchers found that obesity reduced the amount of BDNF in the skeletal muscle of mice. They also observed that the mice without BDNF in their muscle, called 'MBKO' (Muscle-specific BDNF Knockout), gained more body weight and developed worse insulin resistance when the animals were fed with a high-fat diet. In addition, the research team found that MBKO mice have less energy expenditure than their control cohort. The research team further demonstrated that the mitochondria in the muscle of MBKO mice were unable to recycle, leading to the accumulation of damaged mitochondria in the tissues.

Researchers also utilized cultured cell models to pinpoint the molecular mechanism for the defective mitochondrial turnover in BDNF-deficient muscle cells. They found that muscle-secreted BDNF used AMP-activated protein kinase, the well-known energy sensor in cells, to trigger the Parkin/PINK1 pathway for inducing mitophagy (a highly regulated mechanism to recycle the materials in cells in response to various challenges) in skeletal muscle. To extend these findings to therapeutic application, the research team further tested if restoring the BDNF signaling in muscle would rescue the obesity-induced mitochondrial damage. They fed the obese mice with 7,8-dihydroxyflavone, a natural bioavailable BDNF mimetic in plants currently used in the clinical trials of Alzheimer's disease, and found that obesity-induced mitochondrial dysfunction was alleviated.

Link: https://www.hku.hk/press/press-releases/detail/23625.html

Why do only some people develop Alzheimer's disease? Why do only some people with evidence of amyloid and tau protein aggregation in brain tissue also exhibit dementia? These are important questions. Researchers here provide evidence to suggest that whether or not tau protein is isomerized is relevant to the onset and progression of Alzheimer's disease. Isomers of the same molecule have the same molecular weight but a different structure and chemistry. Whether or not isomers of important proteins are present in significant numbers is not well studied in the context of neurodegenerative conditions; perhaps it should be. The researchers here suggest that reduced protein quality control due to faltering autophagy may be to blame for increased isomerization; where this fits into the bigger picture of Alzheimer's pathology is an open question.

Recent work has posited a connection between Alzheimer's disease (AD) and isomerization of amino acids in long-lived proteins, which may interfere with lysosomal digestion. Herein, we reanalyzed data originally recorded for global proteomic analysis to look for isomerized peptides, which occur as a result of spontaneous chemical modifications to long-lived proteins. Examination of a large set of human brain samples revealed a striking relationship between Alzheimer's disease (AD) status and isomerization of aspartic acid in a peptide from tau. Relative to controls, a surprising increase in isomer abundance was found in both AD samples.

To explore potential mechanisms that might account for these observations, quantitative analysis of proteins related to isomerization repair and autophagy was performed. Differences consistent with reduced autophagic flux in AD-related samples relative to controls were found for numerous proteins, including most notably p62, a recognized indicator of autophagic inhibition. These results suggest, but do not conclusively demonstrate, that lower autophagic flux may be strongly associated with loss of function in AD brains.

Link: https://doi.org/10.1021/acs.jproteome.1c00558

The fasting mimicking diet is, in essence, a clever strategy to pull in significant funding for the rigorous study of the use of forms of calorie restriction as a therapy. A fasting mimicking diet involves taking in just few enough calories to trigger most of the benefits of fasting. There must exist a dividing line in calorie intake at which nutrient sensor mechanisms determine that the body is in a state of fasting. Early research into fasting mimicking found that dividing line to be somewhere in the vicinity of 500 to 750 calories daily, but later studies use lower calorie levels. Another important point of calibration is to determine how long a fast must continue in order to produce the optimal, lasting benefits to metabolism. At this point, standard fasting mimicking is a five day exercise, with significant changes to the immune system occurring after the third day.

The real trick here, when it comes to enlisting the support of large entities in the world of regulation and medical development, is that while there is no good way to monetize the practice of fasting, there are very definitely ways to monetize a specific diet. An entire industry is focused on medical diets and the regulation thereof. Thus a specific fasting mimicking diet was created, patented, and fed into the regulatory approval process - and in the process pulled in funding and interest for this line of research and development. For those of us with little interest in these machinations, it is worth noting that the specifics of the diet are unimportant. Any sensible dietary composition that hits the calorie targets and duration should have the desired outcome.

In recent years, the primary focus for clinical trials of fasting mimicking has been its use in the treatment of cancer. It has long been known, as a matter of common wisdom in the medical community, that cancer patients tend do better as a result of forms of calorie restriction. Cancer is unfettered growth, and lowered calorie intake works against that growth in many different ways. Now much more robust data is emerging; today's research materials are an example of the results of that ongoing work.

Fasting-Mimicking Diet Is Safe, May Modulate Metabolism and Boost Antitumor Immunity in Cancer Patients

A diet involving short-term, severe calorie restriction was safe, feasible, and resulted in a decrease of blood glucose and growth factor concentration, reduction in peripheral blood immunosuppressive cells, and enhanced intratumor T-cell infiltration in cancer patients receiving standard-of-care therapy, according to the results of a clinical trial. Researchers enrolled 101 patients in the study with various tumor types treated with different standard anticancer therapies.

The researchers administered a fasting mimicking diet (FMD) regimen to the study participants that consisted of a five-day, low-carbohydrate, low-protein, plant-derived diet, which provided up to 600 Kcal on day 1 and up to 300 Kcal on days 2, 3, 4, and 5, for a total amount of up to 1,800 Kcal in five days. The cycle was repeated every three or four weeks for up to a maximum of eight consecutive cycles. Calorie restriction was followed by a refeeding period of 16 to 23 days, during which patients were not subjected to specific dietary restrictions but were recommended to adhere to international guidelines for a healthy diet and lifestyle.

In 99 evaluable patients, the FMD regimen reduced the median plasma glucose concentration by 18.6 percent, serum insulin by 50.7 percent, and serum IGF-1 by 30.3 percent, with these modifications remaining stable over the course of eight consecutive cycles. In an analysis conducted on 38 patients at the end of a five-day FMD cycle, the researchers found a significant decrease of circulating immunosuppressive myeloid subpopulations and an increase of activated CD8+ T cells. Both of these effects occurred independently of concomitant antitumor therapies and were also observed in a small group of healthy volunteers.

To investigate the effects of the FMD diet on intratumor immunity, researchers performed an interim analysis of another ongoing trial testing a five-day FMD cycle seven to 10 days before surgery in early-stage breast cancer and melanoma patients. Specifically, they evaluated the tumor-infiltrating immune cells and transcriptomic immune profiles in 22 breast cancer patients for whom enough tumor tissue had been collected before and after the FMD. This analysis revealed a significant increase in tumor-infiltrating CD8+ T cells and other changes, indicating a functional switch toward an antitumor immune microenvironment following FMD.

Fasting-mimicking diet is safe and reshapes metabolism and antitumor immunity in cancer patients

In tumor-bearing mice, cyclic fasting or fasting-mimicking diets (FMDs) enhance the activity of antineoplastic treatments by modulating systemic metabolism and boosting antitumor immunity. Here we conducted a clinical trial to investigate the safety and biological effects of cyclic, five-day FMD in combination with standard antitumor therapies. In 101 patients, the FMD was safe, feasible, and resulted in a consistent decrease of blood glucose and growth factor concentration, thus recapitulating metabolic changes that mediate fasting/FMD anticancer effects in preclinical experiments.

Integrated transcriptomic and deep-phenotyping analyses revealed that FMD profoundly reshapes anticancer immunity by inducing the contraction of peripheral blood immunosuppressive myeloid and regulatory T-cell compartments, paralleled by enhanced intratumor T-helper 1/cytotoxic responses and an enrichment of interferon-gamma and other immune signatures associated with better clinical outcomes in cancer patients. Our findings lay the foundations for phase II/III clinical trials aimed at investigating FMD antitumor efficacy in combination with standard antineoplastic treatments.

Cisd2 is one of the few genes shown to regulate life span in both directions in animal models; less of it shortens life span, while overexpression extends life. Researches here focus on the effects of cisd2 on liver function in mice, showing that maintaining high levels of cisd2 expression into old age beneficially impacts a number of processes implicated in degenerative aging and liver disease. This isn't the only organ in which cisd2 expression has measurable effects; other groups have studied cisd2 in the heart, for example.

The liver plays a pivotal role in mammalian aging. However, the mechanisms underlying liver aging remain unclear. Cisd2 is a pro-longevity gene in mice. Cisd2 mediates lifespan and healthspan via regulation of calcium homeostasis and mitochondrial functioning. Intriguingly, the protein level of Cisd2 is significantly decreased by about 50% in the livers of old male mice. This down-regulation of Cisd2 may result in the aging liver exhibiting non-alcoholic fatty liver disease (NAFLD) phenotype. Here, we use Cisd2 transgenic mice to investigate whether maintaining Cisd2 protein at a persistently high level is able to slow down liver aging.

Our study identifies four major discoveries. Firstly, that Cisd2 expression attenuates age-related dysregulation of lipid metabolism and other pathological abnormalities. Secondly, revealed by RNA sequencing analysis, the livers of old male mice undergo extensive transcriptomic alterations, and these are associated with steatosis, hepatitis, fibrosis, and xenobiotic detoxification. Intriguingly, a youthful transcriptomic profile, like that of young 3-month-old mice, was found in old Cisd2 transgenic male mice at 26 months old. Thirdly, Cisd2 suppresses the age-associated dysregulation of various transcription regulators (Nrf2, IL-6, and Hnf4a), which keeps the transcriptional network in a normal pattern. Finally, a high level of Cisd2 protein protects the liver from oxidative stress, and this is associated with a reduction in mitochondrial DNA deletions.

These findings demonstrate that Cisd2 is a promising target for the development of therapeutic agents that, by bringing about an effective enhancement of Cisd2 expression, will slow down liver aging.

Link: https://doi.org/10.1111/acel.13523

Researchers here note that the presence of α-synuclein protein aggregates, a characteristic feature of Parkinson's disease, contributes to the dysfunction of microglia. Microglia are innate immune cells of the brain, responsible not just for attacking pathogens and clearing debris, but also involved in maintaining the synaptic connections between neurons. Increasing attention is placed upon the age-related dysfunction of microglia as an important contribution to the progression of neurodegenerative diseases such as Parkinson's. Chronic inflammation in brain tissue is a feature of neurodegeneration, and much of that may be caused or amplified by changes that take place in the microglial population in response to the age-damaged tissue environment.

Parkinson's disease (PD) is an age-related neurodegenerative disorder, affecting about 2% of the population over 60. Pathologically, it is characterized by dopamine (DA) neuron losses and α-synuclein (α-Syn)-abundant Lewy body or neurites formation in the substantia nigra (SN). Additionally, microglia activation, along with excessive generation of inflammatory cytokines, is reported in the brains of PD patients and animal models.

α-Syn misfolding and aggregation are linked to PD pathology. Under pathological conditions, this synaptic protein can be released from neurons, propagating and spreading in the nervous system via cell autonomous and non-autonomous machinery. The natural state (monomer vs. tetramer) and the structure of neuron-released α-Syn is controversial. But it is well demonstrated that extracellular α-Syn activates microglia and inflammatory response, contributing to PD progression.

In this study, we reported an impairment of microglial autophagy caused by extracellular α-Syn via toll-like receptor 4 (Tlr4) and downstream p38 and Akt-mTOR signaling pathways and provided the evidence that conditional knockout of microglial autophagy-related gene 5 (Atg5) in mice enhanced the neuroinflammation and DA neuron losses in the midbrain and exacerbated the locomotor deficits in a viral-based α-Syn overexpression mouse model.

In sum, our findings demonstrate that α-Syn disrupts microglial autophagy initiation via Tlr4-dependent p38 and Akt-mTOR signaling and reveal that microglial autophagy impairment contributes to neuroinflammation and other PD pathogenesis. Therefore, the pharmacologic and genetic strategies that aim to modulate autophagy activity in the brain may become a potential venue for PD therapy.

Link: https://doi.org/10.1111/acel.13522

Genetic engineering of mouse lineages to produce life-long disruption of growth hormone metabolism, either growth hormone itself or growth hormone receptor, extends life. Animals are smaller, more challenged in maintaining body temperature, have more fat tissue, yet enhanced insulin sensitivity, and exhibit as much as a 70% longer life span. The present record for engineered mouse longevity has been held since 2003 by growth hormone receptor knockout (GHRKO) mice. That this record still stands in 2021 might be taken as a sign that the research and development community are not yet trying hard enough to produce therapies capable of meaningful rejuvenation and extension of healthy life span.

It is an interesting question as to how much of the longevity of GHRKO and similar mice results from the disruption of growth hormone metabolism during development. To pick just one example, a smaller body size can produce a broad range of effects, such as lowered risk of cancer. In today's open access paper, researchers report on their use of an inducible gene knockout mouse lineage to remove growth hormone receptor expression at six months of age, roughly equivalent to a mid-30s human. The mice thus had a normal development, allowing for a better assessment of growth hormone metabolism as a target for therapies intended to slow the progression of aging.

I am not that optimistic that meaningful therapies will result from this line of work. Changes in metabolism that operate for short periods of time have smaller effects than those that operate for longer periods of time. Further, the usual approach of small molecule treatments that interfere in growth hormone metabolism will likely do so only partially, not producing the full effect of a gene knockout. Further, alterations to growth hormone metabolism have much smaller effects on aging in long-lived mammals than is the case for short-lived mammals. The human Laron syndrome population has loss of function mutations in growth hormone receptor, and they do not appear to live significantly longer than the rest of us.

Growth hormone receptor gene disruption in mature-adult mice improves male insulin sensitivity and extends female lifespan

Several mouse lines with germline growth hormone (GH) axis disruptions have shown extensions in lifespan. As a result, it has been proposed that targeted inhibition of the GH axis could be a promising pharmacological intervention to extend healthy aging. Notably, except for the GHRKO mice, the aforementioned mouse lines have reduced action of at least one additional hormone such as prolactin, thyroid-stimulating hormone, or GHRH, that may contribute to their extended longevity phenotype. Therefore, the GHRKO mouse line was established as a model to study the specific effects of reduced GH action in vivo.

Importantly, due to their exceptional longevity, the GHRKO mice hold the Methuselah mouse prize for the world's longest-lived laboratory mouse with a lifespan a week short of 5 years of age. The GHRKO mice also exhibit improved healthspan, showing improved cognition and insulin sensitivity, resistance to diabetes, reduced neoplasia, and decreased markers of aging such as adipose tissue (AT) senescence and mTORC1 signaling in liver, kidney, heart, and muscle.

Our laboratory recently reported that some of the benefits of congenital GH deficiency, such as enhanced insulin sensitivity and extended lifespan in females could be achieved if GHR is disrupted during puberty at 1.5 months of age. In light of such promising results, the present study sought to answer if it is possible to attenuate GH action further in life and attain the benefits obtained in mice with congenital GHR ablation. Clinically relevant interventions to extend healthy lifespan should be given at an adult age. Therefore, here, we disrupted the GHR at 6 months of age in mice.

In the present study, we tested how adult-onset reductions in GH action affect health and lifespan, using a mouse line of inducible ablation of the GHR starting at 6 months of age (6mGHRKO). These mice exhibited GH resistance (reduced IGF-1 and elevated GH serum levels), increased body adiposity, reduced lean mass, and minimal effects on body length. Importantly, 6mGHRKO males have enhanced insulin sensitivity and reduced neoplasms while females exhibited increased median and maximal lifespan. Furthermore, fasting glucose and oxidative damage was reduced in females compared to males irrespective of Ghr deletion. Overall, disrupted GH action in adult mice resulted in sexual dimorphic effects suggesting that GH reduction at older ages may have gerotherapeutic effects.

Like other neurodegenerative conditions, Parkinson's disease is accompanied by the growing presence of a protein aggregate in the brain. The α-synuclein associated with Parkinson's disease is one of the few proteins in the body that can misfold in ways that encourage other molecules of the same protein to also misfold, this dysfunction spreading through tissue over time, creating solid protein aggregates that are toxic to cells or provoke inflammatory reactions in brain tissue. Targeting these aggregates is at present an active area of research, albeit not as far advanced towards the clinic as is the case for targeting the different forms of protein aggregates found in Alzheimer's disease.

Parkinson's disease (PD) is the second most common neurodegenerative disorder that falls under the category of synucleinopathy. PD is characterized by distinct aging-independent loss of dopaminergic neurons in substantia nigra pars compacta (SNpc) region and the decrease in dopamine levels. Possibly, PD leads to the loss of terminal ends of striatum, which occurs before the neuronal loss in SNpc and; it seems to be more significant in disease pathogenesis. About 95% of PD cases are sporadic with no genetic linkage. Mostly, PD has its mean age of onset at 55 years with increased incidences with aging.

The most pathological hallmark of PD is Lewy bodies (LB). Lewy bodies are intraneuronal inclusions that contain immunoreactive alpha-synuclein aggregates which may also contain various neurofilament proteins as well as proteins involved in proteolysis such as ubiquitin. Predominantly, the cell death is caused by disruption of nuclear membrane integrity and release of alpha synuclein aggregation promoting nuclear factors like histones. Alpha synuclein may spread to other cells by direct or indirect means once aggregation starts. When compared with unaffected normal individuals, around 50-70% of neurons are lost in this region, at the time of death in patients with PD. Some studies suggest that LBs are the cell's defensive mechanism to prevent intracellular protein aggregate accumulation, while other studies suggest LBs to have a pathogenic role in PD.

Presently, there are no effective therapeutics contrived for PD. A prudent way to effectively alleviate PD would be to target one of its crucial causatives, alpha-synuclein. Recently, various therapeutic strategies have been formulated, to encumber alpha-synuclein's toxic effect. One such strategy would be to control transmission by blocking alpha-synuclein receptors. LAG3-directed antibodies were reported to substantially regulate aberrant alpha-synuclein induced toxicity. Concurrently, silencing alpha-synuclein expression in mouse and rat brain models through shRNA and siRNA was also reported. Further, the oligomer regulator Anle138b was able to hinder the synthesis and accumulation of alpha-synuclein oligomers. Additionally, numerous small molecule-based inhibitors have been elucidated to impede alpha-synuclein aggregation.

Link: https://doi.org/10.3389/fmed.2021.736978

This open access paper reports on a small study of D-glyceric acid supplementation in older adults. A few weeks of supplementation produced modest gains in mitochondrial function and reductions in measures of inflammation. As is usually the case, it is worth comparing this with the effects of regular exercise, which remains somewhat better at improving mitochondrial function and reducing inflammation in comparison to most of the other available approaches to manipulation of mitochondrial metabolism.

D-glyceric acid (DGA) is a natural organic acid present in very small amounts in vertebrates and plants. Nevertheless, there are only a few scientific studies on this small metabolite. Due to its small size and low, varying, concentrations even the measurement of exact DGA concentration from fluids, and tissues at physiological levels is somewhat challenging. The aim of the present study was to find out direct and indirect indications of the activation of mitochondrial metabolism by the use of DGA.

The main target in the present study with 27 healthy 50-60-year-old human volunteers was to find out whether an "acute" 4-days and a longer 21-days exogenous DGA regimen caused moderate activation of the mitochondrial energy metabolism. The results revealed the following statistically significant findings: 1) plasma concentrations of metabolites related to aerobic energy production, especially lactate, were strongly reduced, 2) systemic inflammation was lowered both in 4- and 21-days, 3) mitochondria-related mRNA expressions in circulating immune cells were noticeably modulated at Day 4, 4) cellular membrane integrity seemed to be sharply enhanced, and 5) cellular NADH/NAD+ ratio was upregulated.

Mitochondrial metabolism was clearly upregulated at the whole-body level in both 4 and 21 days. At the same time, the effect of DGA was very well tolerated. Based on received solid results, the DGA regimen may alleviate acute and chronic energy metabolic challenges in main organs like the liver, central nervous system, and skeletal muscles. Enhanced membrane integrity combined with lower systemic inflammation and activated metabolic flows by the DGA regimen may be beneficial especially for the aging population.

Link: https://doi.org/10.3389/fragi.2021.752636

The Leucadia Therapeutics principals and staff are working towards the prevention of Alzheimer's disease. Unlike most other initiatives in the space, their work is based on a novel understanding of the way in which reduced drainage of cerebrospinal fluid gives rise to Alzheimer's disease and potentially other neurodegenerative conditions. These conditions are characterized by rising levels of protein aggregates and other forms of molecular waste in the brain. This leads to toxicity to neurons, as well as to chronic inflammation due to the reactions of immune cells and other cells in brain tissue.

Cerebrospinal fluid drainage from the brain into the body is one of the ways in which these forms of waste are removed from the brain, keeping levels more manageable. As drainage falters due to age-related changes to the tissues involved, ever more molecular waste is trapped in the brain. Alzheimer's disease is one of the results. Leucadia researchers have in recent years used ferrets to show that surgically blocking cerebrospinal fluid drainage paths provokes early increases in protein aggregation, and then consequent neurodegeneration and cognitive decline.

Leucadia is one of the many stories in the anti-aging research and development community that in some way involves the Methuselah Foundation. Early work at Leucadia was funded by the foundation, and it was a conversation with Dave Gobel of the Methuselah Foundation at a scientific conference that convinced Doug Ethell, the Leucadia founder, to take his work out of academia and start down the road to human clinical trials. The company will in the next few years implant valve devices into patients to restore a measured flow of cerebrospinal fluid through the most important drainage pathway, and hopefully thereby definitely proof that Alzheimer's disease can be indefinitely postponed via this approach.

Scientists Develop AI Algorithms To Analyze Enormous Datasets In Alzheimer's Research

For the past 25 years, Alzheimer's disease researchers have viewed plaques and tangles pathology as the cause of Alzheimer's, which has led to an unbroken string of failed clinical trials. In 2014, neuroscientist Doug Ethell published a new hypothesis about the trigger for Alzheimer's and related dementias. In 2015, he founded Leucadia Therapeutics to develop a therapy based on his hypothesis. Leucadia's research has shown that plaques and tangles are effects of a more serious underlying condition that triggers the formation of those pathological features.

The cribriform plate is a porous bony structure located in the roof of the nasal cavity. The plate contains two deep pockets called fossa and many holes called olfactory foramina. Olfactory nerves that transmit the sense of smell pass through these holes. The cribriform plate is an outflow route the brain uses to clear out waste in cerebrospinal fluid (CSF). About half a liter of CSF is produced by the brain each day, but only about 1/20 of it drains through the cribriform plate. However, that small amount of CSF is responsible for clearing brain regions that are critical for making new memories and orienting us in the world. As humans age, the cribriform plate becomes ossified and less porous. The small holes close up and restrict the flow of cerebrospinal fluid. As less and less of this fluid is drained out of the brain, waste and toxins accumulate in the upstream brain regions responsible for memory. These waste-products form a slough (an area of dead tissue) where plaques form and neurons form tangles - two key hallmarks of Alzheimer's disease. Ethell's research indicates that Alzheimer's disease pathology result from reductions in cerebrospinal fluid drainage across the cribriform plate.

Leucadia Therapeutics is preparing for a clinical trial in 2022 that will use an implantable device to restore CSF drainage across the cribriform plate. With increasing life-expectancy, Dr. Ethell believes his device will become as common as a pacemaker. This well-founded approach should reverse early mild cognitive impairment and prevent Alzheimer's disease from occurring at all.

Psychological stress appears to modestly accelerate some measures of aging, though most of the evidence for this correlation comes from animal studies. Evidence points to chronic inflammation, and the immune system in general, as an important factor in this correlation. Separately, chronic inflammation in brain tissue is known to be important in neurodegenerative conditions, and the behavior of innate immune cells known as microglia are of late receiving increased attention in this context. Researchers here join the dots to discuss whether microglia may be a primary link between stress and accelerated aging.

The relationship between the central nervous system (CNS) and microglia is lifelong. Microglia originate in the embryonic yolk sac during development and populate the CNS before the blood-brain barrier forms. In the CNS, they constitute a self-renewing population. Although they represent up to 10% of all brain cells, we are only beginning to understand how much brain homeostasis relies on their physiological functions. Often compared to a double-edged sword, microglia hold the potential to exert neuroprotective roles that can also exacerbate neurodegeneration once compromised.

Microglia can promote synaptic growth in addition to eliminating synapses that are less active. Synaptic loss, which is considered one of the best pathological correlates of cognitive decline, is a distinctive feature of major depressive disorder (MDD) and cognitive aging. Long-term psychological stress accelerates cellular aging and predisposes to various diseases, including MDD, and cognitive decline. Among the underlying mechanisms, stress-induced neuroinflammation alters microglial interactions with the surrounding parenchymal cells and exacerbates oxidative burden and cellular damage, hence inducing changes in microglia and neurons typical of cognitive aging.

Focusing on microglial interactions with neurons and their synapses, this review discusses the disrupted communication between these cells, notably involving fractalkine signaling and the triggering receptor expressed on myeloid cells (TREM). Overall, chronic stress emerges as a key player in cellular aging by altering the microglial sensome, notably via fractalkine signaling deficiency. To study cellular aging, novel positron emission tomography radiotracers for TREM and the purinergic family of receptors show interest for human study.

Link: https://doi.org/10.3389/fnmol.2021.749737

Does the adult mammalian body contain naturally pluripotent stem cells, capable for forming any other cell type, given the right stimuli? Over the past twenty years various groups have argued that it does, but none of those scientists have produced evidence that is both compelling and easily replicated. If they had, the entire research community would have quickly jumped onto that bandwagon, just as they did after the discovery of reprogramming as a way to produce induced pluripotent stem cells. Patient-specific pluripotent cells are a highly desirable item, and a cost-effect source would enable many applications in regenerative medicine and tissue engineering. Given this history, I think it appropriate to treat the material here with a healthy degree of skepticism.

A certain cell type can be isolated from different organs in the adult body (i.e., adipose tissue, heart, skin, bone marrow, or skeletal muscle) that can differentiate into ectoderm, mesoderm, and endoderm, providing significant support for the existence of a certain type of small, ubiquitously distributed, universal, vascular-associated, pluripotent stem cell in the adult body (vaPS cells). These vaPS cells fundamentally differ from embryonic stem cells and induced pluripotent stem cells in that the latter possess the necessary genetic guidance that makes them intrinsically pluripotent. In contrast, vaPS cells do not have this intrinsic genetic guidance. Nevertheless, they are able to differentiate into somatic cells of all three lineages under guidance of the microenvironment they are located in, independent from the original tissue or organ that they are derived from.

These vaPS cells are of high relevance for clinical application because they are contained in unmodified, autologous, adipose-derived regenerative cells (UA-ADRCs). The latter can be obtained from and re-applied to the same patient at the point of care, without the need for further processing, manipulation, and culturing. These findings as well as various clinical examples presented in this paper demonstrate the potential of UA-ADRCs for enabling an entirely new generation of medicine for the benefit of patients and healthcare systems.

As with any medical innovation, the scientific and medical community interested in these novel therapies needs to develop sound clinical evidence to further show safety and efficacy of cell-based therapies. Our understanding of the mechanism of actions and potential benefit of stem cell therapy has increased enormously over the past decade and we hope that there is now enough data to convince others to embark on scientifically designed clinical studies that will provide the necessary objective evidence.

Link: https://doi.org/10.3390/cells10092303