Fight Aging!

The authors of today's open access paper present an interesting and novel way in which visceral fat tissue provokes chronic inflammation. It has been noted that dysfunctional B cells accumulate with age. Here, dysfunctional B cells of a specific subtype are shown to accumulate in aged visceral fat tissue, acting to provoke other immune cells in visceral fat tissue, such as macrophages, into a more pro-inflammatory state. The researchers demonstrate that removing the B cell population helps to reduce the age-related inflammation generated by visceral fat by removing the contribution to inflammatory macrophage behavior.

Of note, B cells regenerate quite rapidly following clearance, and it seems that using pharmacological means or gene therapies to clear out B cells in aged individuals would improve a number of issues. Targeted clearance of specific immune cells (such as microglia in the brain), or indeed the immune system as a whole, is an underdeveloped area of medical research, and one that could in principle produce therapies capable of reversing a number of aspects of immune aging.

Age-associated accumulation of B cells promotes macrophage inflammation and inhibits lipolysis in adipose tissue during sepsis

Aging is accompanied by an increase in visceral adiposity, immune cell activation, and decreased ability of visceral white adipose tissue (vWAT) to maintain homeostatic functions such as lipolysis that is required for the generation of free fatty acids. Lipolysis is activated via canonical (catecholamine) or non-canonical pathways (bacteria or inflammatory cytokines). The chronic inflammatory activation of macrophages and B cells seen during aging suppresses catecholamine-stimulated lipolysis by limiting the bioavailability of catecholamines, but it is unclear whether these vWAT immune cells from older organisms would enhance or suppress the stimulated lipolysis in the context of sepsis and inflammation.

Canonical lipolysis induced by catecholamines declines during aging due to factors including an expansion of lymphocytes, pro-inflammatory macrophage polarization, and an increase in chronic low-grade inflammation; however, the extent to which the non-canonical pathway of lipolysis is active and impacted by immune cells during aging remains unclear.

Therefore, we aimed to define the extent to which immune cells from old mice influence non-canonical lipolysis during sepsis. We identified age-associated impairments of non-canonical lipolysis and an accumulation of dysfunctional B1 B cells in the visceral white adipose tissue (vWAT) of old mice. B cells can be classified as innate-like B1 B cells that acutely produce non-specific natural antibodies during bacterial infections or adaptive B2 B cells that become memory B cells and produce high-affinity antibodies. These subsets expand equally with age and can be distinguished by the expression of CD11b on the B1 subset but not the B2 subset.

Lifelong deficiency of B cells in mice results in restored non-canonical lipolysis and reductions in pro-inflammatory macrophage populations. This data indicates that age-related accumulation of B cells promotes a pro-inflammatory macrophage phenotype including the upregulation of NLRP3 inflammasome activation, supporting a model in which B cells indirectly suppress non-canonical lipolysis by promoting macrophage inflammation.

Researchers here report that life-long tristetraprolin (TTP) upregulation leads to reduced frailty and improved bone mineral density in aged mice. One of the functions of TTP is that it suppresses expression of the pro-inflammatory TNF-α cytokine, so a reduced degree of age-related inflammation would be the first place to look for an explanation of the outcome noted here. It is an open question as to whether TTP upregulation produces a more nuanced and reactive reduction of TNF-α signaling than is the case for the blunt, across the board inhibition achieved by present anti-TNF-α therapies, and is thus a mechanism that interferes less in the necessary immune response to injury and infection.

Researchers have presented results from a study aiming to use a novel transgenic mouse model (TTP knock-in - TTPKI) that has a moderate elevation of tristetraprolin (TTP) systemically to understand if there is a long-term benefit for bone health. The study performed body composition, physical performance assessments, and frailty assessments on the 6-month-old and 22-month-old TTPKI and C57BL/6N wild-type male and female mice.

Microcomputed tomography (µCT) and decalcified sections of the tibia were used to determine static bone histomorphometric parameters and bone histomorphometry, respectively. Immunophenotypic analysis of bone marrow (BM), spleen, and mesenteric lymph nodes were analyzed by flow cytometry for myeloid and lymphocyte populations. Myeloid population BM osteoclastogenic potential was assessed.

Body composition with aged control and TTPKI mice revealed significant sex and genotype differences. Aged TTPKI mice displayed decreased frailty scores and increased quality of life compared to control similarly aged mice. The tibia from aged TTPKI mice exhibited higher bone mineral density (BMD) than aged control mice. Age-related decline in immune cell composition was partially reversed in aged TTPKI mice. In an osteoclast differentiation assay, BM myeloid progenitors from TTPKI mice exhibited fewer osteoclasts with reduced eroded bone surface area. Improved functional capacity, BMD, and immune cell composition indicate that enhanced expression of TTP can promote a healthier phenotype during aging.

Link: https://www.iadr.org/about/news-reports/press-releases/enhanced-stability-tristetraprolin-promotes-bone-health-and

Myelin surrounds the axons that connect neurons to one another, and is required for the transmission of electrical impulses. This myelin sheath is maintained by oligodendrocytes. These cells do not carry out their work in isolation; a great many factors are involved in determining the size and capabilities of the oligodendrocyte population. Aging is disruptive to the myelination carried out by oligodendrocytes. The consequences are not as bad as the profound loss of myelin that takes place in demyelinating diseases such as multiple sclerosis, but age-related loss of myelination does appear to degrade cognitive function. Researchers are thus interested in understanding the mechanisms involved, in search of ways to restore a youthful capacity for myelination in the aging brain.

Myelin regeneration (remyelination) is essential to prevent neurodegeneration in demyelinating diseases such as Multiple Sclerosis, however, its efficiency declines with age. Regulatory T cells (Treg) recently emerged as critical players in tissue regeneration, including remyelination. However, the effect of ageing on Treg-mediated regenerative processes is poorly understood.

Here, we show that expansion of aged Treg does not rescue age-associated remyelination impairment due to an intrinsically diminished capacity of aged Treg to promote oligodendrocyte differentiation and myelination in male and female mice. This decline in regenerative Treg functions can be rescued by a young environment. We identified Melanoma Cell Adhesion Molecule 1 (MCAM1) and Integrin alpha 2 (ITGA2) as candidates of Treg-mediated oligodendrocyte differentiation that decrease with age.

Our findings demonstrate that ageing limits the neuroregenerative capacity of Treg, likely limiting their remyelinating therapeutic potential in aged patients, and describe two mechanisms implicated in Treg-driven remyelination that may be targetable to overcome this limitation.

Link: https://doi.org/10.1038/s41467-024-45742-w

It is evident and settled that stochastic nuclear DNA damage contributes to cancer. The more of it that you have, the worse your risk. What is still very much debated is whether nuclear DNA damage contributes meaningfully to degenerative aging, and how it does so. Most mutational damage to DNA occurs in regions that are inactive, in cells that have comparatively few divisions remaining before reaching the Hayflick limit. Even if damage alters the function of such a cell, in some non-cancerous way, it is unclear as to how this could amount to a meaningful contribution to loss of tissue function.

The one school of thought is focused on somatic mosaicism, the spread of mutations throughout a tissue when mutational damage occurs in stem cells. In this case subtle dysfunctions could accumulate and interact with the spread of mutated cells over time. While there is evidence for somatic mosaicism to contribute to the risk of some forms of cancer, evidence is still lacking for it to meaningfully affect tissue function to the degree that aging does.

A second school of thought is focused on unexpected consequences of the repeated operation of DNA repair machinery. Double strand break repair can apparently deplete factors needed for maintaining the correct structure and epigenetic control of nuclear DNA, leading to age-related changes in epigenetics and gene expression. This is a comparatively recent discovery, and not yet fully digested, replicated, and risen to the status of consensus. It is an attractive proposition, however, a way to explain how stochastic mutational damage to inactive regions of the genome can somehow produce a consistent, systemic outcome throughout tissue, while forms of mutational damage other than double strand breaks can occur in greater amounts without strongly impacting age-related degeneration.

Somatic mutations in human ageing: New insights from DNA sequencing and inherited mutations

Taken together, recent DNA sequencing experiments focused on quantifying mutations with age reveal a gradual increase in mutations, and widespread evidence of clonal expansion of rapidly dividing mutant clones. These observations are consistent with the age-related increase in cancer observed in most tissues. However, the levels of mutations reported so far are difficult to reconcile with most ageing phenotypes. Whether and how somatic mutations in ageing tissues, affecting mostly non-coding regions and overwhelmingly different genes in different cells, can cause dysfunction is unclear. Likewise, while clonal expansion may be a factor in ageing and result in tissue dysfunction, so far this is not directly supported by experimental data and remains an open question.

As such, there is a stark contrast between cancer and ageing: while cancer can originate from mutations in a single cell and subsequent clonal expansion, shown empirically to occur, age-related dysfunction would need, we suggest, many mutations in a very large number of cells in a tissue. Evolutionarily this has led others to suggest that the evolutionary pressure to prevent cancer will result in levels of somatic mutations in tissues across the lifespan that will be lower than the number of mutations needed to cause most other age-related conditions.

Recent evidence from inherited mutations in patients with increased somatic mutation burden and no symptoms of accelerated ageing also cast doubt on the role of somatic mutations in most ageing phenotypes - even if it is not well understood why hypermutator phenotypes sometimes do and sometimes do not result in progeroid phenotypes. Perhaps other forms of DNA damage and/or genome instability may accumulate at much greater rates in human tissues, but these have not been studied in detail and have thus far limited empirical support. The impact of clonal expansion, somatic copy-number alteration (SCNAs), and structural variations (SVs) on ageing phenotypes, in fact, remains to be further investigated. Advances in genome sequencing technology together with the development of computational methods to reliably detect large-scale structural alterations at a single-cell level should shed light on the potential role of SVs and SCNAs on human ageing.

After the idea that somatic mutations could be the main cause of ageing was first proposed in the late 1950's, Maynard-Smith questioned it by arguing that the number of mutations necessary would be too high to be consistent with the data available at the time. Decades and numerous technological advances in genetics and genomics later, which have produced quantitative data on mutation load in aged tissues, and yet we are no closer to empirically showing a role for somatic mutations in ageing and, in fact, have grounds to question it.

The machinery of gene expression changes with age. In recent years, it has been noted that the length of gene sequences correlates with the degree to which transcription of gene sequences into RNA molecules changes over the course of aging. Later work has started to examine the proximate causes of these changes, various fine detail mechanisms buried in the depths of transcription. The research community is not yet at the point of being able to conclusively demonstrate that altered transcription of longer genes produces meaningful downstream consequences in degenerative aging, as interventions specifically targeting just this process of transcriptional change have yet to be established. This is worth keeping an eye on, however.

Recent studies of aging organisms have identified a systematic phenomenon, characterized by a negative correlation between gene length and their expression in various cell types, species, and diseases. We term this phenomenon gene-length-dependent transcription decline (GLTD) and suggest that it may represent a bottleneck in the transcription machinery and thereby significantly contribute to aging as an etiological factor.

Currently, it is yet to be understood whether GLTD is only a marker of aging or whether it also actively plays a role in the aging process itself. We consider this to be the greatest outstanding question on GLTD. To measure the potential impact of GLTD on aging, it would be necessary to identify interventions or experimental schemes that only affect GLTD. However, no such intervention or experimental scheme is currently known.

To quantify the magnitude of impact of any such intervention, we may further need to first apply them to animal models. Even in such studies, it would remain challenging to attribute effects toward aging to GLTD rather than any single subsets of genes that change their transcription as part of GLTD. Nevertheless, we cautiously suspect a causal contribution.

Link: https://doi.org/10.1016/j.tig.2024.01.009

Researchers here show that targeting microglia in a mouse model of Alzheimer's disease to suppress p16 expression can reduce amyloid-β plaques. This appears to be a way to interfere in a maladaptive reaction to amyloid-β on the part of microglia, innate immune cells responsible for clearing molecular debris from brain tissue. P16 is a marker of cellular senescence, though may also be characteristic of non-senescent but still problematic, pro-inflammatory microglia. There is a good amount of evidence to suggest that both senescent and overly active microglia are important to the progression of neurodegenerative conditions such as Alzheimer's disease. Senescent cells can be cleared by senolytic therapies, and evidence in animal studies suggests that this should help Alzheimer's patients. Dealing with non-senescent, activated and problematic microglia will require a different strategy, however.

Age-dependent accumulation of amyloid plaques in patients with sporadic Alzheimer's disease (AD) is associated with reduced amyloid clearance. Older microglia have a reduced ability to phagocytose amyloid, so phagocytosis of amyloid plaques by microglia could be regulated to prevent amyloid accumulation. Furthermore, considering the aging-related disruption of cell cycle machinery in old microglia, we hypothesize that regulating their cell cycle could rejuvenate them and enhance their ability to promote more efficient amyloid clearance.

First, we used gene ontology analysis of microglia from young and old mice to identify differential expression of cyclin-dependent kinase inhibitor 2A (p16ink4a), a cell cycle factor related to aging. We found that p16ink4a expression was increased in microglia near amyloid plaques in brain tissue from patients with AD and 5XFAD mice, a model of AD. In the BV2 microglia cell line, small interfering RNA (siRNA)-mediated p16ink4a downregulation transformed microglia with enhanced amyloid phagocytic capacity through regulated the cell cycle and increased cell proliferation.

To regulate microglial phagocytosis by gene transduction, we used poly (D,L-lactic-co-glycolic acid) (PLGA) nanoparticles, which predominantly target microglia, to deliver the siRNA and to control microglial reactivity. Nanoparticle-based delivery of p16ink4a siRNA reduced amyloid plaque formation and the number of aged microglia surrounding the plaque and reversed learning deterioration and spatial memory deficits. We propose that downregulation of p16ink4a in microglia is a promising strategy for the treatment of Alzheimer's disease.

Link: https://doi.org/10.1186/s13024-024-00715-x

The balance of microbial populations making up the gut microbiome changes with age in ways that are damaging to long-term health. Firstly the proportion of pro-inflammatory microbes grows, provoking the immune system into greater degrees of unresolved inflammation. This state of inflammaging observed in older individuals is disruptive to tissue structure and function throughout the body, and contributes meaningfully to the onset and progression of many age-related conditions. Secondly, the proportion of microbes generating beneficial metabolites decreases, leading to other forms of dysfunction. For example, butyrate production leads to BDNF expression, regulating important mechanisms such as neurogenesis in the brain. This production of butyrate by the gut microbiome diminishes with age.

Why does the population of the gut microbiome shift with aging? It is widely thought that immune system aging is important, in that (a) the immune system is responsible for gardening the gut microbiome, suppressing problem species, and (b) the immune system becomes less effective with age. In today's open access paper, researchers explore one of the less frequently considered aspects of innate immunity, the production of antimicrobial peptides, small molecules that can kill many types of microbe. Working in mice, the researchers show that decreased production of these peptides in intestinal tissues correlates directly with the increase of harmful bacterial species in the gut microbiome. This points the way to novel classes of therapy that might beneficially adjust the gut microbiome, restoring it to a more youthful balance of microbial populations.

Evidence that the loss of colonic anti-microbial peptides may promote dysbiotic Gram-negative inflammaging-associated bacteria in aging mice

Aging studies in humans and mice have played a key role in understanding the intestinal microbiome and an increased abundance of "inflammaging" Gram-negative (Gn) bacteria. The mechanisms underlying this inflammatory profile in the aging microbiome are unknown. We tested the hypothesis that an aging-related decrease in colonic crypt epithelial cell anti-microbial peptide (AMP) gene expression could promote colonic microbiome inflammatory Gn dysbiosis and inflammaging.

As a model of aging, C57BL/6J mice fecal (colonic) microbiota and isolated colonic crypt epithelial cell gene expression were assessed at 2 months, 15 months, and 25 months. Fecal microbiota exhibited significantly increased relative abundances of pro-inflammatory Gn bacteria with aging. Colonic crypt epithelial cell gene expression analysis showed significant age-related downregulation of key AMP genes that repress the growth of Gn bacteria. The aging-related decrease in AMP gene expressions is significantly correlated with an increased abundance in Gn bacteria (dysbiosis), loss of colonic barrier gene expression, and senescence- and inflammation-related gene expression.

This study supports the proposed model that aging-related loss of colonic crypt epithelial cell AMP gene expression promotes increased relative abundances of Gn inflammaging-associated bacteria and gene expression markers of colonic inflammaging. These data may support new targets for aging-related therapies based on intestinal genes and microbiomes.

Microglia are innate immune cells resident in the central nervous system. Microglial dysfunction is clearly a contributing factor in the onset and progression of age-related neurodegenerative conditions, including Alzheimer's disease, as well as the accompanying chronic inflammation of brain tissue. As to why microglia become problematic and inflammatory, there are any number of possible contributing mechanisms to consider. Cellular senescence, mitochondrial dysfunction, reactions to cell debris or the presence of persistent viral infections, and more. In this vein, researchers here discuss excessive lipid accumulation in microglia as a possible contributing cause of Alzheimer's disease.

Several genetic risk factors for Alzheimer's disease implicate genes involved in lipid metabolism and many of these lipid genes are highly expressed in glial cells. However, the relationship between lipid metabolism in glia and Alzheimer's disease pathology remains poorly understood. Through single-nucleus RNA sequencing of brain tissue in Alzheimer's disease, we have identified a microglial state defined by the expression of the lipid droplet-associated enzyme ACSL1 with ACSL1-positive microglia being most abundant in patients with Alzheimer's disease having the APOE4/4 genotype.

In human induced pluripotent stem cell-derived microglia, fibrillar amyloid-β induces ACSL1 expression, triglyceride synthesis, and lipid droplet accumulation in an APOE-dependent manner. Additionally, conditioned media from lipid droplet-containing microglia lead to Tau phosphorylation and neurotoxicity in an APOE-dependent manner. Our findings suggest a link between genetic risk factors for Alzheimer's disease with microglial lipid droplet accumulation and neurotoxic microglia-derived factors, potentially providing therapeutic strategies for Alzheimer's disease.

Link: https://doi.org/10.1038/s41586-024-07185-7

Platelets in the blood are not just involved in clotting. Near every aspect of our biology has evolved many different functions, and the complexity of our biochemistry is still far from fully explored. Increased platelet factor 4 (PF4) shows up as a feature in a number of different interventions known to reduce inflammation in the aging brain. Researchers are now moving in the direction of developing therapies for neurodegenerative conditions based on the upregulation of PF4 or the delivery of recombinant PF4.

Platelets are a component of blood best known for their role in clotting, but research in recent years has illuminated other functions beyond the traditional part they play in healing wounds. Each platelet contains more than 1,000 bioactive molecules, known as platelet factors, that get released in different combinations when platelets are activated.

Several years ago, researchers discovered some of the first hints that one of those hundreds of molecules, PF4, might be particularly important. The group was trying to explain why exercise increases neurogenesis in the hippocampus, a brain region important for learning and memory. Hypothesizing that something happens in the blood after exercise that affects the brain, researchers first screened the blood of adult mice after they started running on running wheels placed in their cages. They found about 80 factors whose abundance in the blood changed significantly after exercise, and PF4 was among those that rose the most.

When the researchers injected PF4 into the bloodstream of older mice through their tails on a schedule of one injection every third day for 24 days, the old mice behaved much more like young mice in the avoidance task and other memory tests. The findings echoed the cognitive benefits researchers have seen with exercise, which included increased neurogenesis in the brains of the older mice treated with PF4.

While this group was conducting its research linking exercise to PF4 and PF4 to cognition, another team of researchers was trying to identify individual components in young blood that might explain its rejuvenating effects. Inflammation is known to increase with age. In the brain, inflammation activates a type of immune cells called microglia, ultimately leading to neuronal dysfunction and neurodegeneration. Previous studies have shown that injecting old blood into young mice increases inflammation in the young hippocampus. The new study was the first to show that young blood attenuates neuroinflammation and, in turn, reduces the activity of microglia. The injection of platelets alone was enough to have these effects. And the most common protein in the platelet solution, analysis showed, was PF4.

Although PF4 didn't appear to cross the blood-brain barrier, data showed that PF4 affects the peripheral immune system, reducing the number of pro-aging immune factors in circulation, decreasing neuroinflammation and enhancing cognitive function. That sequence of events suggests that both circulating immune factors and the peripheral immune system could be targets of future therapeutics.

Link: https://www.simonsfoundation.org/2024/03/19/research-converging-on-how-young-blood-improves-old-brains/

Epidemiology is prone to difficulties that arise when attempting to interpret limited data sets, packed with information, but never quite all of the information that would be necessary to see the real story. Try to look at the health differences between people who drink and people who don't, and the sample of those who don't is polluted by former problem drinkers with problematic lives. Try to look at the health differences between obese and non-obese patients, and the non-obese cohort will be polluted by formerly obese people who have lost weight due to poor health and advanced disease. Try to base considerations on body mass index (BMI), and the high BMI groups are polluted by heavily muscled former athletes. And so forth.

Some of these problems are now evident in hindsight and sufficiently debated for researchers to have come to a resolution. No-one uses BMI when height and waist circumference are available. Researchers seek weight history rather than looking only at snapshots in time. But each of these advances can require ten to fifteen years to percolate through the epidemiological community. Even after that point, the old data sets remain the old data sets, lacking modern conveniences. Further, there are always new ways to provoke debate in the framing of data, and provoking debate is a great way to have people cite your paper. So the incentives tend to line up for more of the same in the future.

So to today's epidemiological results, which fly in the face of everything that is known about intermittent fasting and calorie restriction. To grossly oversimplify decades of research, it is starting to look like time spent hungry is beneficial regardless of calorie intake, and all mild forms of calorie restriction, fasting, and time-restricted feeding appear both beneficial and safe. So what might be happening here? How does one find a correlation between time-restricted feeding and greatly increased risk of cardiovascular mortality? If one looks at what the researchers say about the data, it occurs to me that selecting for time-restricted feeding habits in the general population is selecting for people who have been prompted into that course by the perception of needing to lose weight or having received physician guidance to lose weight. Both of those options correlate with being overweight or obese. Thus selecting for unusual dietary habits in this study population may be a good proxy for excess weight.

8-hour time-restricted eating linked to a 91% higher risk of cardiovascular death

Time-restricted eating, a type of intermittent fasting, involves limiting the hours for eating to a specific number of hours each day, which may range from a 4- to 12-hour time window in 24 hours. Many people who follow a time-restricted eating diet follow a 16:8 eating schedule, where they eat all their foods in an 8-hour window and fast for the remaining 16 hours each day, the researchers noted. Previous research has found that time-restricted eating improves several cardiometabolic health measures, such as blood pressure, blood glucose, and cholesterol levels.

In this study, researchers investigated the potential long-term health impact of following an 8-hour time-restricted eating plan. They reviewed information about dietary patterns for participants in the annual 2003-2018 National Health and Nutrition Examination Surveys (NHANES) in comparison to data about people who died in the U.S., from 2003 through December 2019, from the Centers for Disease Control and Prevention's National Death Index database.

The analysis found: (a) people who followed a pattern of eating all of their food across less than 8 hours per day had a 91% higher risk of death due to cardiovascular disease; (b) the increased risk of cardiovascular death was also seen in people living with heart disease or cancer; (c) among people with existing cardiovascular disease, an eating duration of no less than 8 but less than 10 hours per day was also associated with a 66% higher risk of death from heart disease or stroke; (d) time-restricted eating did not reduce the overall risk of death from any cause; (e) An eating duration of more than 16 hours per day was associated with a lower risk of cancer mortality among people with cancer.

For those following research into efforts to upregulate NAD+ levels to improve mitochondrial function, this paper is an interesting sidebar. Some degree of loss of NAD+ emerges from increased activity of CD38. Apigenin is a dietary supplement that can modestly influence both sleep and pace of aging, the latter in short-lived laboratory species at least. Apigenin can increase NAD+ levels by inhibiting CD38 activity. Like much of metabolism, this is all very interesting, but the effect sizes are nothing to write home about. If upregulating NAD+ levels is the goal, you'll do better by exercising. The fundamental flaw in so much of medical development, particularly in the supplement industry, is that few of the people involved seem to pay any attention to effect size. It is crazy! Effect size should be the first thing anyone looks for. Then side-effects. So much effort is, to my eyes, wasted on development programs for products with effects that are significantly worse than the results of exercise.

NAD+, a pivotal coenzyme central to metabolism, exhibits a characteristic decline with age. In mice, NAD+ levels can be elevated via treatment with apigenin, a natural flavonoid that inhibits the NAD+-consuming glycoprotein CD38. In animal models, apigenin positively impacts both sleep and longevity. For example, apigenin improves learning and memory in older mice, reduces tumor proliferation in a mouse xenograft model of triple-negative breast cancer, and induces sedative effects in mice and rats. Moreover, apigenin elongates survival in fly models of neurodegenerative disease and apigenin glycosides increase lifespan in worms.

Apigenin's therapeutic potential is underscored by human clinical studies using chamomile extract, which contains apigenin as an active ingredient. Collectively, chamomile extract has been reported to alleviate anxiety, improve mood, and relieve pain. Furthermore, dietary apigenin intake positively correlates with sleep quality in a large cohort of adults. Apigenin's electron-rich flavonoid structure gives it strong bonding capacity to diverse molecular structures across receptors and enzymes. The effects of apigenin extend beyond CD38 inhibition, encompassing agonistic and antagonistic modulation of various targets, including GABA and inflammatory pathways. Cumulatively, a large body of evidence positions apigenin as a unique molecule capable of influencing both aging and sleep. Further studies are warranted to better understand apigenin's nuanced mechanisms and clinical potential.

Link: https://doi.org/10.3389/fnut.2024.1359176

Researchers here report on an approach to meaningfully stimulate the regenerative capacity of the liver. The liver is one of the few organs capable of significant regrowth in mammals, and the way in which it does so is quite different from the regenerative response found in other tissues. Thus while the results here are quite impressive, they don't apply to other organs. This is purely a way to manipulate the regulation of liver regeneration.

One key feature of acute and chronic liver diseases, and after extended liver resections, is the inability of hepatocytes to sufficiently regenerate and restore or maintain a critical functional liver mass. Although healthy livers harbor a nearly unlimited regenerative potential, damage-associated changes in the hepatic microenvironment of acutely or chronically injured livers diminish the hepatocytes' regenerative capacity. Unfortunately, the underlying molecular mechanisms are poorly understood.

We recently reported on the discovery of the dual specific kinase MKK4 as a master regulator of hepatocyte regeneration. MKK4 is a MAP2 kinase and part of the stress-activated protein kinase (SAPK)/mitogen-activated protein kinase (MAPK) signaling networks. MKK4 can be activated upon a cell's exposure to different stress stimuli. Short hairpin RNA (shRNA) mediated silencing of MKK4 was found to unlock endogenous regenerative capacity of hepatocytes in acutely or chronically injured livers via derouting SAPK signaling predominantly through MKK7 and JNK1 toward a downstream pro-regenerative transcriptional program mediated by ATF2 and ELK1. Unfortunately, no small molecule inhibitors for selective MKK4 inhibition are available.

We here report on the development and in vitro and in vivo characterization of first-in-class small molecule inhibitors of the dual specific kinase MKK4 (MKK4i). MKK4i increased liver regeneration upon hepatectomy in murine and porcine models. Strikingly, treatment with the clinical candidate HRX215 prevented post-hepatectomy-liver-failure (PHLF) and allowed for the survival of pigs in a lethal 85% hepatectomy model, suggesting that boosted liver regeneration by HRX215 might represent a viable treatment option for human PHLF and the pathogenetically related small for-size syndrome (SFSS) after liver transplantation. Testing of HRX215 in a phase I trial in 48 healthy volunteers revealed excellent safety, tolerability, and pharmacokinetics (PKs) of HRX215. Clinical trials to probe HRX215 as a therapeutic option to prevent/treat liver failure after extensive oncological liver resections or after transplantation of small liver grafts are warranted.

Link: https://doi.org/10.1016/j.cell.2024.02.023

It has been going on eight years since I last speculated on the order of arrival of the first rejuvenation therapies. Tempus fugit, and time for an updated version! Eight years is a long enough span of time for the first of those rejuvenation therapies to now exist, albeit in a prototypical form, arguably proven in principle but not concretely. The world progresses but my biases remain much the same: the first rejuvenation therapies to work well enough to merit the name will be based on the SENS vision, that aging is at root caused by a few classes of accumulated cell and tissue damage, and biotechnologies that either repair that damage or render it irrelevant will as a result produce rejuvenation. The number of groups aiming to produce these therapies has grown considerably. A longevity industry now exists, scores of biotech and pharmaceutical companies where eight years ago there were only a handful. We are eight years further into the grand transition across decades that is taking place in the medical life sciences, in which the treatment of aging will grow to become the majority of medicine.

Age-related diseases are age-related precisely because they are caused by the same processes of damage that cause aging. The only distinctions between aging and disease are the names given to various collections of symptoms. All of frailty, disease, weakness, pain, and suffering in aging is the result of accumulated damage and consequent dysfunction at the level of cells and protein machinery inside those cells. Once the medical community becomes firmly set on the goal of repairing that damage, humanity will be well on its way to controlling and managing aging as a chronic condition, preventing it from causing harm to the patient by periodically repairing and removing the causes of aging before they rise to the level of producing symptoms and dysfunction. The therapies of the increasingly near future will be very different from those of the past. The full rejuvenation toolkit of the next few decades will consist of a range of different treatments, each targeting a different type of molecular damage in cells and tissues. What follows is a list of potential (and existing!) rejuvenation therapies in a speculative order of arrival.

1) Clearance of Senescent Cells

A good number of companies are presently developing a wide range of senolytic approaches to selectively destroying senescent cells, thereby removing their contribution to degenerative aging. A wide range of small molecules provoke apoptosis in senescent cells in a wide range of different ways, while other approaches train the immune system to better destroy lingering senescent cells. Studies in mice continue to demonstrate rapid, sizable reversal of aspects of aging and many different age-related diseases following the use of senolytic therapies. The most advanced of the first generation senolytic therapies are in phase 2 clinical trials. Given another decade there will be multiple novel senolytic drugs approved for use in the clinic, and no doubt increasingly used off-label by older individuals.

I'll make the argument that the first effective senolytic therapy to be tested in animals, the dasatinib and quercetin combination, is both legitimately a rejuvenation therapy and also readily available to anyone who wants to undergo the treatment. The use of dasatinib and quercetin in combination has been demonstrated to clear senescent cells from some human tissues to a similar degree as it does in mice. It is prescribed off-label by more adventurous physicians and anti-aging practices. It will likely be decades before we know the degree to which any senolytic affects human life expectancy - no-one seems much incentivized to run the sort of long-term human trial that would be required. Nonetheless, the burden of senescent cells is in principle a component of aging, supported by a great deal of animal data. Dasatinib and quercetin removes some of that burden, and this is rejuvenation to my eyes, even if broader benefits to health remain to be demonstrated comprehensively in human trials.

2) Restoration of a Youthful Gut Microbiome

The gut microbiome ages in the sense that the distribution of microbial populations changes in harmful ways: more pro-inflammatory microbes and fewer microbes capable of generating beneficial metabolites. Animal studies suggest that the state of the gut microbiome is at least as consequential to long-term health as diet and exercise. As is the case for senolytics, proven ways to reverse age-related changes in gut microbiome exist, but are not widely used, and it will most likely remain unclear for decades to come as to exactly how much of an effect such a rejuvenation has on human long-term health and life span.

The most obvious and cost-effective intervention for rejuvenation of the aged gut microbiome, the results demonstrated in animal studies and a few small human trials, is fecal microbiota transplant from a young individual. This produces a lasting reset of the gut microbe, and can be readily carried out by anyone willing to put in the work. There are even services that sell screened fecal material from young donors. A second approach is immunization with flagellin to encourage the immune system to clear unwanted microbes, those equipped with flagellae. These microbes are largely harmful, causing chronic inflammation, as well as diminishing the populate size of beneficial species by outcompeting them.

Unlike senolytics, there is no rush to commercialize forms of fecal microbiota transplant for the treatment of age-related conditions. There is one FDA-approved fecal microbiota transplantation therapy, for a condition in which the intestine is overrun with pathological bacteria, but that is about it. Thus it seems unlikely that concrete data will emerge any time soon on the degree to which gut microbime rejuvenation improves health and life span. While we can say that it is evidently rejuvenation, and animal data supports that assertion, whether it is rejuvenation to a practical degree in humans remains to be proven.

3) Clearance of the First Few Types of Amyloid

There are about twenty different types of amyloid in the human body, misfolded proteins that form solid deposits. Not all are robustly associated with age-related dysfunction, but of those that are, some progress has been made towards effective therapies based on either direct clearance or interfering in the pace of creation of altered proteins. In the matter of the amyloid-β associated with Alzheimer's disease, there are now several immunotherapies that have demonstrated effective clearance of amyloid-β from the brain. The side-effect profile leaves much to be desired, and it has become clear that late stage Alzheimer's is past the point at which clearing amyloid-β helps all that much. It may well be a useful preventative strategy, however, assuming that the treatments for clearance can be made more benign.

Transthyretin amyloid is associated with heart disease, and is thought to be the primary cause of death in supercentenarians. There are now FDA-approved therapies based on interfering in the creation of altered transthyretin. Some are applicable to the wild-type rather than genetic condition of transthyretin amyloidosis. Arguably every older person should be using these intermittently, assuming a mild side-effect profile, but it will take some time for costs to fall to the point at which this is practical.

This sentiment applies to any therapy targeting forms of amyloid - and there are many more forms to be addressed. To the degree that these treatments are effective and safe, everyone much over the age of 40 should be undergoing a course of treatment every few years. Should we expect more such treatments to emerge over the next decade? Perhaps. More attention is being given to the amyloid called medin, for example, drawing attention to its contributions to the pathology of degenerative aging. It may be that developers will turn their attention to this and other amyloids, but it is hard to predict how fashion and happenstance steers the choice of investment into specific avenues of medical development.

4) A Robust Cure for Cancer

If asked a decade ago, a universal cure for cancer looked fairly distant. There was clearly work on telomeres and telomerase relevant to cancer, but it didn't have the look of programs ready to make the leap to the clinic. All cancers depend absolutely on the ability to continually lengthen telomeres, and so avoid the Hayflick limit on cell replication. Telomere lengthening occurs through the activity of telomerase or the less well understood alternative lengthening of telomeres (ALT) mechanisms. If telomerase and ALT can both be blocked, temporarily and either globally throughout the body or selectively in cancerous tissue, then cancer will wither and become controllable. This is too fundamental a part of cellular biochemistry for the rapid mutational evolution of cancer cells to work around. Stem cell populations will suffer while telomerase activity is blocked, as they require telomere lengthening for self-renewal, but that is a lesser problem when compared to cancer and one that the stem cell research community will become increasingly able to address in the years ahead.

So a decade ago the fundamental research was progressing, but not all that rapidly. Still, all it takes is one innovative approach to produce good enough animal data, and a clinical program will rapidly arise. At present the drug called THIO is in clinical trials after an accelerated program of development at Maia Biotechnology. THIO is metabolized and utilized by telomerase, then incorporated into telomeres to cause disruptive consequences leading to cell death. Since near all cancer cells aggressively utilize telomerase, these are the cells that die when THIO is introduced. It should work for the 90% of cancers that do not evolve to make use of ALT, and will be widely used off-label following clinical approval for any one type of cancer. From this starting point, we might expect a great deal more effort in the decades to come to focus on telomere lengthening as a primary target in cancer - and at some point a group with a novel approach will swoop in to deal with the remaining ALT part of the problem.

5) Thymic Rejuvenation to Increase the Supply of Immune Cells

Another possible approach to partially restore lost function in the aging immune system is to increase the pace at which new immune cells are created. This is a very slow pace indeed in older people, due in large part to the age-related decline of the thymus. The thymus acts as a nursery for the maturation of T cells, and its atrophy thus restricts the rate at which new cells enter circulation. Over the 2010s, there was some progress towards engineering of replacement active thymus tissue, as well as methods of providing signal proteins that instruct the old thymus to regenerate and begin to act in a more youthful manner. Transplants of young thymus organs into old mice demonstrated that this class of approach can produce a meaningful improvement in immune function, and thereby extend healthy life.

A decade ago, this was one of a number of regenerative approaches that were on the verge, just waiting for someone to join the final two dots together, found a biotech company, and get moving. That now seems to be happening. The approach of providing signal proteins has proven to be hard, but there are now a few biotech companies, some quite well funded and connected, focused on either (a) cell therapies using cell types that naturally home to the thymus, such as Thymmune Therapeutics, or (b) looking for small molecules that cleverly interfere in the regulation of thymus growth while avoiding the pitfalls associated with past efforts, such as Thymofox.

Further, Intervene Immune has run clinical trials of a growth hormone approach, producing data to suggest a modest degree of thymic regrowth over a year or more of treatment; interestingly data from the CALERIE trial of calorie restriction indicates a similar gain from a few years of slight calorie restriction, implying thymic involution to be perhaps a more dynamic process than suspected. Meanwhile, some interesting advances are taking place in the research community, such as the possibility of gene therapy delivery system that can in fact effectively target the thymus following intravenous delivery. Exciting times! The state of the field looks promising for some form of effective thymus rejuvenation strategy to emerge in the decade ahead.

6) Mitochondrial Repair

Mitochondria, the power plants of the cell, are herds of bacteria-like organelles that bear their own DNA. This DNA becomes damaged in the course of normal cellular processes, and certain forms of mitochondrial DNA damage - to the thirteen genes needed for oxidative phosphorylation - produce malfunctioning mitochondria that can overtake their cells. Further, epigenetic changes characteristic of aging disrupt the dynamics of mitochondria, disrupting the quality control process of mitophagy. This also allows poorly functioning mitochondria to replicate and prosper, but occurs in cells throughout the body.

There are numerous possible approaches to the problem of dysfunctional mitochondrial in aged tissues: upregulation of existing repair mechanisms of mitophagy; delivery of replacement mitochondrial DNA or whole mitochondria; partial reprogramming of cells to restore normal gene expression relating to mitochondrial dynamics and mitophagy; and so forth. Of these, the closest to the clinic are mitochondrial transfusion therapies and the various approaches to adjusting repair and propagation of damaged states in mitochondria, trying to tilt the balance to favor better function. The development of partial reprogramming therapies has enormous funding at present, but arguably much larger challenges must be solved before it can be broadly applied to tissues across the body. It remains hard to say how effective these approaches will be relevative to one another. How long will they last before fading in an aged tissue environment? Also unknown.

In the case of mitochondrial transfusion, two companies (cellvie and Mitrix Bio) are working towards clinical programs. Their challenge is near entirely the development of the processes by which enough mitochondria for human use can be manufactured. From the present starting point that is a tough scaling problem. In the case of altering mitochondrial dynamics or the regulation of mitophagy, there are range of possibilities already sold in the supplement market, such as SkQ1 and MitoQ, none of which are all that impressive when compared to the effects of exercise. Will companies like Stealth Bio do any better than this? That remains to be seen. There is a market for small molecule and supplement-like products that are not as good as exercise, but it is probably not a market that should interest us.

The SENS approach is somewhat more radical, involving gene therapy to introduce copies of the thirteen genes into the cell nucleus, altered to ensure that the proteins produced can migrate back to the mitochondria where they are needed. Mitochondria will thus have the necessary protein machinery for correct function regardless of the state of their DNA. This has been demonstrated for three of the thirteen genes of interest, numbers two and three in 2016, and getting that far took the better part of ten years at a low level of funding. A company, Gensight Biologics has championed this approach in clinical trials for one of the genes, in the treatment of a rare genetic disorder, but little further or broader development has taken place outside of academia. Will it be useful to have therapies that fix half the problem, moving six or seven genes to the cell nucleus? Will that reduce the impact on aging by half? It is hard to say until that is possible and demonstrated in mice. A decade ago, it seemed plausible that researchers would get there by now - but this has not happened. There is still too little funding and support for this approach, and one might well argue that backing mitochondrial transfusion seems a better wager at this point, even given the unknowns.

7) Reversing Stem Cell Aging

The stem cell industry remains massively funded, and is ultimately on a collision course with stem cell aging. Most of the conditions that one would want to use stem cell therapies to treat are age-related conditions. Researchers must thus work towards ensuring that the altered cellular environment, the damage of aging, doesn't prevent these treatments from working - that pristine cells can integrate and work well, not immediately die or decline in response to an age-damaged stem cell niche. Despite some progress over the past decade, particularly around the question of whether cellular senescence is degrading cell therapy outcomes, it is fair to say that the research community isn't engaging aggressively with this goal, however. Possible reasons for this include the fact that most stem cell treatments, even without addressing issues of the aged tissue environment, represent a considerable improvement in the scope of what is possible to achieve through modern medicine. So the incentive to go further is perhaps not as strong as it might otherwise be.

Stem cell populations become damaged by age, falling into quiescence or declining in overall numbers. They should be replaced with new populations, but while simple in concept, and even achieved for some cell types, such as the blood stem cells that produce immune cells, this is easier said than done for the body as a whole. Every tissue type is its own special case. There are hundreds of types of cell in the body. Each supporting stem cell population has so far required specific methodologies to be developed, and specific behaviors and biochemistry to be laboriously mapped. It isn't even entirely clear that researchers have found all of the stem cell or stem-like cell populations of interest. There is an enormous amount of work to be done here, and at the moment the field is still largely in the phase of getting the basics, the maps, and the reliable therapeutic methods sorted out for a few of the better understood tissue types, bone marrow and muscles in particular. All in all this has the look of a long-term, incremental prospect, despite the high levels of funding for this line of medical research and development.

Are there ways other than complete replacement of cell populations that might enable reinvigoration of aged stem cell populations? It seems that there might be, though we can argue about the degree to which these approaches are in any way affecting aging per se. There are ways to adjust the regulation of stem cell behavior that improve tissue function even given that one is working with aged stem cell populations. To pick one example, Ship of Theseus develops an approach based on Hox family transcription factors that appears to provoke greater muscle stem cell activity. As another example, look at the work of Mogling Bio, building on demonstrations showing CASIN to improve stem cell function in a number of populations, particularly the hematopoietic stem cells of the bone marrow. These and other, analogous approaches will find their way to clinic long before replacement of stem cell populations is a going concern.

8) Clearance of Cross-Links, Glucosepane-Based and Others

Clearance of cross-links in the extracellular matrix of tissues is, like senescent cell destruction, one of the most exciting of early rejuvenation therapies. It is a single target that influences a great many aspects of aging: if we look at just the cross-link-induced loss of elasticity in blood vessels alone, that has a major influence on mortality through hypertension and consequent impact on cardiovascular health. It is also a single target in the sense that near all persistent cross-links important to aging in humans so far appear to be based on one compound, glucosepane. Thus all that is needed is one drug candidate.

The attention given to glucosepane cross-link clearance remains anemic, despite considerable efforts to create a toolkit and unblock the research community conducted by the SENS Research Foundation and their allies in the research community, including a method of cheaply and reliably synthesizing glucosepane. Work in the mid-2010s conducted in the Spiegel Lab, as well as other parallel lines of research, led to the formation of Revel Pharmaceuticals to commercialize glucosepane cross-link breakers. Unfortunately, little further progress has occurred - while still being a sizable step forward over the state of the field a decade ago, this remains a narrow effort pioneered by few researchers.

A small number of other narrow programs have emerged focused on the lens of the eye, where different forms of cross-linking are involved in stiffening the lens to the point at which muscle strength is inadequate to focus correctly. A lipoic acid choline ester approach looked promising, but failed in Phase 2 trials. Another company, Lento Bio, is now in the early stages of working on another approach to the cross-links that stiffen the lens. Again, there are few groups in this space, and more are needed to ensure a good chance of progress towards the clinic in the near future.

9) Partial Reprogramming

Ten years ago, one could mount a good argument for the epigenetic change characteristic of aging to be distant from the root causes of aging, a downstream effect. Since then, evidence has mounted for some of this epigenetic change to be a direct result of forms of DNA damage and repair, tying it directly to one of the root causes of aging, the stochastic DNA damage that takes place constantly in all cells. At the same time, researchers have demonstrated that the reprogramming techniques based on exposure to Yamanaka factors, initially used in efforts to produce induced pluripotent stem cells for research and cell therapy development, reversed epigenetic aging long before they started to change cell fate. Short-term exposure to reprogramming, now known as partial reprogramming, is potentially a way to reset the epigenetic changes characteristic of aging and restore many forms of cell function. Clearly partial reprgramming cannot help with existing mutational damage to nuclear DNA, nor with the presence of persistent molecules that even youthful cells cannot effectively break down. But it is demonstrated to restore lost mitochondrial function, to pick one example.

When might we expect the first therapies based on partial reprogramming to reach the clinic? This part of the field has become enormously well funded in recent years. Given the the $3 billion investment in Altos Labs alone, never mind the other few biotech startup companies with more than $100M in initial funding each, such as Retro Biosciences and NewLimit, there will be no shortage of effort put into preclinical and clinical development. Nonetheless, the challenges are sizable. Different cell types and tissues require different exposures and balances of reprogramming factors for best effect. Too much reprogramming produces cancer via induced pluripotency. Too much reprogramming in the liver and intestines seems very detrimental to health in animal studies. The most likely path to near term therapies is to restrict them to isolated organs, such as the retina and optic nerve. Another possibility is for the groups working on small molecules capable of triggering expression of reprogramming factors to land on something that is more useful for systemic delivery than the gene therapy approaches, but development of small molecule reprogramming is still in the very early stages.

So it remains to be seen as to how matters will unfold in the years ahead. The advent of reprogramming as the leading, widely recognized approach to rejuvenation, and the degree to which funding poured into this project, caught a lot of people by surprise. It seems likely that the surprises will continue, given that we are only a few years into the development of this part of the field.

10) Immune System Destruction and Restoration

The destruction and recreation of the immune system is not a widespread technique, but it has been demonstrated successfully in human clinical trials and animal studies in a variety of contexts over the past twenty years. Researchers and clinicians have used chemotherapy to destroy immune cells and the hematopoietic cells that create them, followed by hematopoietic stem cell transplant (HSCT) to reconstruct the immune system. This approach has resulted in effective cures for multiple sclerosis patients, and has been attempted with varying degrees of success for a number of other autoimmune conditions. The catch here is that chemotherapy and HSCT are not trivial undertakings. The costs and risks are significant, both immediately and in terms of impact on later health and life expectancy. It only makes sense for people who are otherwise on their way to an early death or disability, as is the case for multiple sclerosis patients. However, there are a number of approaches on the way to practical realization that will make chemotherapy obsolete for the selective destruction of immune cells and stem cells - approaches with minimal or no side-effects. See a combined approach targeting c-kit and CD47, for example. Sophisticated cell targeting systems such as the gene therapy approach developed for senescent cell clearance by Oisin Biotechnologies could also be turned to stem cell or immune cell destruction, given suitable markers of cell chemistry. There are quite a few of these, any one of which would be good enough.

Replacing the taxing procedures of chemotherapy and HSCT with a safe, side-effect-free treatment would mean that the field of immune system restoration could immediately expand to assess its merits as a treatment for immunosenescence, the age-related failure of the immune system. This decay is in part a problem of configuration: a lifetime of exposure to persistent pathogens such as herpesviruses leaves too much of the immune system uselessly devoted to specific targets that it cannot effectively clear from the body, and too little left ready to fight new threats and destroy malfunctioning cells. Then there are various forms of autoimmunity that become prevalent in older people, not all of which are in any way fully understood - consider the comparatively recent discovery of type 4 diabetes, for example. Clearing out the entire immune system, all of its memory and quirks, and restarting it fresh with a new supply of stem cells is a good approach to many of the issues in the aged immune system. Not all of them, but many of them, and considering the broad influence immune function has over many other aspects of health and tissue function, it seems a worthwhile goal.

That said, has there been much meaningful progress in this part of the field over the past ten years? Not really. Some research has moved forward incrementally, such as on the topic of age-associated B cells and their depletion, or clearance of microglia in the brain. In the broader field, good number of immunomodulatory approaches to therapy are under development at various stages, some even explicitly aimed at restoring better immune function in the old, but very few target clearance of immune cell populations. The only one that springs to mind is related to the aforementioned clearance of microglia in the brain, since there are existing drugs and a simple mechanism - CSF1R inhibition - by which this can be achieved. The early stage venture Glionics would like to use this clearance and recovery as a way to delivery drugs throughout the brain, rather than specifically to achieve benefits resulting from clearance.

11) Clearance of Other Amyloids, Aggregates, and Sundry Lysosomal Garbage

A good portion of aging is driven by the accumulation of waste products, either because they are hard for our biochemistry to break down, is the case for glucosepane cross-links and many of the components of lipofuscin that degrade lysosomal function in long-lived cells, or because clearance systems fail over time, as appears likely to be the case for the amyloid-β involved in Alzheimer's disease. There are a lot of these compounds: a score of amyloids, any number of lipofuscin constituents, the altered tau that shows up in tauopathies, and so on and so forth. In many cases there isn't even a good defensible link between a specific waste compound and specific age-related diseases: the waste is one contribution buried in many contributions, and the research community won't start putting numbers to relative importance until it is possible to clear out these contributions one by one and observe the results.

A range of research groups are picking away at individual forms of waste, some with large amounts of funding, some with very little funding, but this is a similar situation to that I outlined above for stem cell aging. There is a huge amount of work to accomplish because there are many targets to address, and with few exceptions, such as amyloid-β, it is unclear which of the targets are the most important. They will all have to be addressed, in some order, but there are only so many researchers and only so much funding. We can hope that as the first effective therapies spread into wider clinical use, treatments for the clearance of forms of amyloid, there will be a growing enthusiasm for work on ways to remove other types of metabolic waste.

Despite the considerable attention given to calorie restriction and intermittent fasting in the research community, there is very little formalism applied to the practice in humans. The few clinical trials conducted to date have had to pick their own protocols, and it is only comparatively recently that the fasting mimicking diet was developed to plant a flag on one specific implementation. The challenge here is that it is difficult to monetize calorie restriction and fasting, and thus there is no push towards standardization or more detailed assessment of variant protocols from any of the usual parties who might otherwise be doing so. It is unlikely that the fasting mimicking diet or any of the existing fasting and calorie restriction trial protocols happen to be the best approach, and also unlikely that much work will be done to improve on this situation.

Caloric restriction (CR) or energy restriction, when carefully designed, monitored, and implemented in self-motivated and compliant individuals, proves to be a viable non-pharmacologic strategy for human weight control and obesity management. Beyond its role in weight management, CR has the potential to impede responses involved not only in the pathogenesis of various diseases but also in the aging process in adults, thereby being proposed to promote a healthier and longer life. The core objective of implementing caloric restriction is to establish a balance between energy intake and expenditure, typically involving a reduction in intake and an increase in expenditure - a negative balance at least initially. It may transition toward and maintain a more desired equilibrium over time.

However, it is essential to note that CR may lead to a proportional reduction in micronutrient intake unless corresponding supplementation is provided. Historical human case reports on CR have consistently maintained adequate intakes (AI) or recommended dietary allowances (RDA) for essential micronutrients, including vitamins and minerals. Similarly, longevity studies involving non-human primates have upheld micronutrient consumption levels comparable to control groups or baseline measures. Recent randomized controlled trials (RCTs) have also endorsed daily supplementation of multivitamins and minerals to meet micronutrient needs. However, aside from these human case reports, limited human trials, and primate experiments, there remains a notable gap in human research specifically addressing precise micronutrient requirements during CR.

While adhering to AI or RDA for minerals and vitamins appears sensible in the current practice, it's important to recognize that these guidelines are formulated for generally healthy populations under standard circumstances. The adequacy of these guidelines in the setting of prolonged and profound negative energy balance remains unclear. From perspectives of evidence-based medicine and precision nutrition, this field necessitates comprehensive exploration to uncover the intricacies of absorption, utilization, and metabolism and the requirement of each hydrophilic and lipophilic vitamin and mineral during these special periods. Such investigations are crucial to determine whether existing daily dietary recommendations for micronutrients are quantitatively inadequate, excessive, or appropriate when energy balance remains negative over extended durations.

Link: https://doi.org/10.3389/fnut.2024.1363181

Just as the research community is interested in finding pharmaceutical ways to provoke some the beneficial reactions to calorie restriction, there is also considerable effort devoted to the search for drug candidates that can mimic some of the benefits of exercise. If the history of calorie restriction mimetic drug development is any guide, this will be a slow process, and the resulting compounds will produce lesser benefits than actual exercise, as they will only touch on a small subset of the processes involved. Still, there is no shortage of programs in this space, and here is one example.

Exercise benefits both mind and body. A drug that can mimic these effects could offset the muscle atrophy and weakness that can occur as people age or are affected by cancer, certain genetic conditions, or other reasons they are unable to carry out regular physical activity. The metabolic changes associated with exercise kick off with the activation of specialized proteins, known as estrogen-related receptors (ERRs), which come in three forms: ERRα, ERRβ, and ERRγ. After about a decade of work, researchers developed a compound named SLU-PP-332, which activates all three forms, including the most challenging target, ERRα. This type of ERR regulates exercise-induced stress adaptation and other important physiological processes in muscle. In experiments with mice, the team found this compound increased a fatigue-resistant type of muscle fiber while also improving the animals' endurance when they ran on a rodent treadmill.

To identify SLU-PP-332, the researchers scrutinized the structure of the ERRs and how they bind to molecules that activate them. Then, to improve upon their discovery and develop variations that could be patented, the team designed new molecules to strengthen the interaction with the receptors and thus provoke a stronger response than SLU-PP-332 can provide. When developing the new compounds, the team also optimized the molecules for other desirable characteristics, such as stability and low potential for toxicity. Research using SLU-PP-332 suggests targeting ERRs could be useful against specific diseases. Studies in animals with this preliminary compound indicate that it could have a benefit against obesity, heart failure, or a decline in kidney function with age.

Link: https://www.eurekalert.org/news-releases/1037097

Exosomes are a class of extracellular vesicle, membrane-wrapped packages of molecules that carry a sizable fraction of the chemical communications that takes place between cells. The various types of extracellular vesicle are presently ordered in a taxonomy by their size rather than any more subtle combination of features. Those subtle features definitely exist; exosomes from different cell types and different environmental circumstances are quite different from one another in any number of ways. The present taxonomy of extracellular vesicles is indicative of a lack of detailed understanding regarding (a) the mechanisms determining formation of extracellular vesicles, as well as (b) the factors determining the contents of extracellular vesicles.

The stem cell therapies that have long been available via medical tourism, and were later approved by regulators, are slowly morphing into exosome therapies. Extracellular vesicles are more easily harvested, stored, and delivered than is the case for cells. Since transplanted cells die quickly, the benefits of first generation stem cell therapies, such as months-long reductions in chronic inflammation, are mediated by cell signaling, such as the release and uptake of extracellular vesicles. Exosome therapies are now broadly available in overseas clinics, and are working their way into the more heavily regulated medical system. It is even possible to purchase amniotic fluid derived exosomes from providers in the US, provided one has a physician who agrees to accept delivery and make use of them.

The approach to exosome therapy noted in today's open access paper is an interesting one. The source of cells is those that are shed into urine. When humans are the donors, this is a good way to obtain enough material for a mouse study, but a scaling process would have to be put in place for use in human patients. That means either a great deal of harvesting from many donors, or the more challenging approach of developing a well-managed cell line that can produce exosomes in bulk.

Extracellular vesicles from human urine-derived stem cells delay aging through the transfer of PLAU and TIMP1

Transplantation of young and healthy stem cells has been shown to increase health and lifespan in aged mice. A study has reported that the intraperitoneal injection of muscle stem/progenitor cells from young mice can extend healthspan and lifespan in progeroid mice. Interestingly, the transplanted cells are not detected in many rejuvenated tissues, suggesting that their anti-aging effects are mainly mediated by activating endogenous cells in the host through paracrine factors.

Secretion of extracellular vesicles (EVs) is a part of normal physiology in both prokaryotes and eukaryotes. EVs are selectively enriched with various molecules such as proteins and nucleic acids from their parent cells and serve as a key mediator of cell paracrine action by transferring these molecules to their recipient cells. Stem cells-derived EVs have become an attractive option for therapeutic uses because these nanoparticles have fewer safety concerns and are easy to store, transport, and use compared with stem cells themselves. Recent studies have reported that EVs from embryonic stem cells, induced pluripotent stem cells, adipose stem cells, hypothalamic stem/progenitor cells, and umbilical cord- or umbilical cord blood-derived mesenchymal stem cells (MSCs) can alleviate aging-related phenotypes in aged mice, indicating the promising potential of EVs as an anti-aging agent. Nevertheless, the use of these stem cells as the "factory" to harvest EV are limited by many problems, such as the ethical issue for cell use, the lack of enough source to obtain cells, or/and the requirement of fast, convenient, and invasive procedures for cell isolation.

As compared with stem cells from other sources, urine-derived stem cells (USCs) can be collected by a low-cost, simple, and safe method without ethical concerns. We have previously demonstrated that the local injection of USC-derived EVs (USC-EVs) can accelerate wound repair in diabetic mice by enhancing angiogenesis. We have also found that the intravenous injection of USC-EVs can reduce bone loss and enhance bone strength in osteoporotic mice. Moreover, these nanovesicles can exert protective effects against glucocorticoid-induced osteonecrosis by promoting angiogenesis, and suppress cell apoptosis after systemic administration. In our previous study, we obtained proteomic data regarding the differentially expressed proteins between USC-EVs and USCs. In this study, we further analyzed these data and found that a class of USC-EVs-enriched proteins have been previously shown to possess anti-aging function, such as tissue inhibitor of metalloproteinases 1 (TIMP1), plasminogen activator urokinase (PLAU), insulin-like growth factor binding protein 5, senescence marker protein-30, and connective tissue growth factor. Thus, we hypothesized that USC-EVs might be capable of rejuvenating old organs from aging via transferring of anti-aging proteins.

Here, we tested the effects of USC-EVs on cellular senescence in vitro and on the aging-related phenotypes in different organs of both senescence-accelerated mice and natural aging mice. The intravenous injection of USC-EVs improves cognitive function, increases physical fitness and bone quality, and alleviates aging-related structural changes in different organs of senescence-accelerated mice and natural aging mice. The anti-aging effects of USC-EVs are not obviously affected by the USC donors' ages, genders, or health status. Proteomic analysis reveals that USC-EVs are enriched with PLAU and TIMP1. These two proteins contribute importantly to the anti-senescent effects of USC-EVs associated with the inhibition of matrix metalloproteinases, cyclin-dependent kinase inhibitor 2A (P16INK4a), and cyclin-dependent kinase inhibitor 1A (P21cip1). These findings suggest a great potential of autologous USC-EVs as a promising anti-aging agent by transferring PLAU and TIMP1 proteins.

There are now several immunotherapies capable of clearing amyloid-β aggregates from the aging brain, and a sizable amount of clinical trial data to look through. Sadly, this approach doesn't much help patients in the later stages of Alzheimer's disease, but the evidence to date suggests that it may be useful in prevention if the clearance is conducted early enough. Amyloid-β aggregation causes mild cognitive impairment in and of itself, but really just sets the stage for a set of different processes, inflammation and tau aggregation, that drive the late stage of Alzheimer's disease. At that point, clearing amyloid-β makes little difference to the outcome. It is worth noting that these immunotherapies bear a meaningful risk of serious side-effects. That side-effect profile will have to improve if anti-amyloid-β therapies are to become widely used as a preventative treatment in patients prior to evident cognitive impairment.

Clinical trials have proven that the anti-amyloid therapies donanemab and lecanemab slow the terrible fall into neurodegenerative aging of the Alzheimer's type (AD). As we noted, one key reason these trials succeeded where many promising antibodies had failed is that they started giving people these treatments earlier in the course of the disease. The reason why early treatment is critical is not primarily because there's less beta-amyloid in the brain earlier on in the course of AD. Instead, the benefit of acting early comes from the greater opportunity for beta-amyloid clearance to hold off other kinds of aging damage that occur downstream of it in the brain.

In the original Phase III trial for donanemab, the researchers didn't just compare all the subjects who received the antibody to those who received the placebo, but also compared people who received the treatment and who had "moderate" levels of tau aggregates in their brains to all the treated subjects combined (that is, those with moderate levels plus those with high levels together). Donanemab slowed the downward drag of the disease in all groups, but it was more effective in people who were less burdened by brain tau aggregates. When scientists used the integrated Alzheimer Disease Rating Scale (iADRS) to test donanemab's effectiveness in preserving the ability of people in the trial to carry on the day-to-day business of life and social interaction, they found that it slowed the fall by 35% in people with a medium tau burden, but by only 22% in the combined population. And on top of all that, early donanemab treatment yielded a significantly greater reduction in the number of cells called astrocytes in the brain that had abandoned their normal housekeeping activities and become "reactive."

These trials provide robust evidence supporting the classical "Amyloid Cascade" - the idea that neurodegenerative aging of the Alzheimer's type is a domino-tumble of destruction that starts as beta-amyloid drives tau aggregates to invade additional regions of the brain, leading to neurons first failing to interact with each other and eventually dying, all culminating in dementia. Following this logic, it seems increasingly likely that clearing out beta-amyloid early enough might forestall AD for decades - intervene in outwardly healthy middle-aged people with seemingly intact brains, and keep treating them indefinitely to save their minds.

Link: https://www.sens.org/amylosens-alzheimers-marathon-decathlon/

A variant in the gene BPIFB4 has been found to correlate with longevity in humans. In these matters it is worth noting that even small effects on mortality risk result in noticeable correlations with sustained over decades, and indeed all of the known human associations between longevity and genetic variation identified in large study populations are thought to have only modest effect sizes. What are the underlying mechanisms for BPIFB4, however? Researchers here make an argument for suppression of the chronic inflammation of aging as the reason for the association between BPIFB4 and longevity. Certainly chronic inflammatory signaling is disruptive to tissue function, and a major issue in aging.

Increased levels of pro-inflammatory proteins in plasma can be detected in older individuals and associate with the so called chronic low-grade inflammation, which contributes to a faster progression of aged-related cardiovascular (CV) diseases, including frailty, neurodegeneration, gastrointestinal diseases, and disorders reflected by alterations in the composition of gut microbiota. However, successful genetic programme of long-living individuals alters the trajectory of the ageing process, by promoting an efficient immune response that can counterbalance deleterious effects of inflammation and the CV complications. This is the case of BPIFB4 gene in which, homozygosity for a four single-nucleotide polymorphism (SNP) haplotype, the Longevity-Associated Variant (LAV) correlates with prolonged health span and reduced risk of CV complications and inflammation.

The relation between LAV-BPIFB4 and inflammation has been proven in different experimental models, here we hypothesized that also human homozygous carriers of LAV-BPIFB4 gene may experience a lower inflammatory burden as detected by plasma proteomics that could explain their favourable CV risk trajectory over time. We used high-throughput proteomic approach to explore the profiles of circulating proteins from 591 baseline participants selected from the Progressione delle Lesioni Intimali Carotidee (PLIC) cohort according to the BPIFB4 genotype to identify the signatures and differences of BPIFB4 genotypes useful for health and disease management. The observational analysis identified a panel of differentially expressed circulating proteins between the homozygous LAV-BPIFB4 carriers and the other alternative BPIFB4 genotypes highlighting in the latter ones a higher grade of immune-inflammatory markers.

Link: https://doi.org/10.1186/s12979-024-00424-5

TDP-43 is one of a small number of proteins that can become altered in ways that lead to the formation of solid aggregates that, directly and indirectly, cause cell dysfunction and death in the brain. In the case of TDP-43, this proteopathy contributes to amyotrophic lateral sclerosis (ALS), frontotemporal lobar degeneration (FTLD), and what is now called limbic predominant age-related TDP-43 encephalopathy (LATE). This was a more recent discovery than other aggregates involved in neurodegenerative conditions, such as amyloid-β, tau, and α-synuclein, and so the pace of discovery for TDP-43 is a little faster; more remains to be uncovered of the biochemistry of TDP-43 pathology than is the cost for the other problematic proteins.

In today's research materials, the scientists involved report on a potential role for TDP-43 in dysfunction of the vasculature and blood-brain barrier in the aging brain. Unmodified TDP-43 appears necessary for a number of processes, and depletion may be a contributing cause of some of the vascular issues seen in neurodegenerative conditions associated with TDP-43 aggregation. An important vascular issue is leakage of the blood-brain barrier, allowing unwanted cells and molecules to enter the brain to cause inflammatory reactions or other damage. That said, the usual challenges apply to the finds here, in that knowing that a mechanism exists doesn't tell us how important it is versus other mechanisms known to contribute to this problem.

The integrity of the blood-brain barrier depends on a protein that is altered in some neurodegenerative diseases

The TDP-43 protein is a key factor in nervous system function and neuronal plasticity. It is a DNA- and RNA-binding protein that regulates gene expression, and its dysfunction has been associated with various neurodegenerative disorders. Although much progress has been made recently in understanding the functions of TDP-43 in neurons, its exact role in the endothelial cells that make up the circulatory system, the formation of new blood vessels (angiogenesis), and vascular function was not yet known.

The vascularization of the central nervous system and the formation of the blood-brain barrier are regulated by different signalling pathways. For example, the integrin signalling pathway that regulates the interaction of cells with the extracellular matrix and the signalling carried out by the transcription factor β-catenin. "In the study, we found that TDP-43 deficiency alters the extracellular matrix that surrounds blood vessels and reduces β-catenin signalling in endothelial cells. Thus, mice without endothelial TDP-43 protein show multiple haemorrhages and vascular degeneration in the brain and spinal cord."

The authors also identify TDP-43 in endothelial cells as a potential contributing factor to the vascular defects that trigger the inflammatory response observed in patients diagnosed with TDP-43-associated diseases. "Some alterations in the blood vessels of the central nervous system - defects in the integrity of the blood-brain barrier or degeneration of endothelial cells - are associated with inflammatory and immune responses that can cause neuronal loss. This process of neuronal degeneration underlies the origin or progression of various neurological disorders - stroke, diabetic retinopathy - and some neurodegenerative diseases such as Alzheimer's disease, ALS, or LATE (Limbic-predominant age-related TDP-43 encephalopathy)."

Endothelial TDP-43 controls sprouting angiogenesis and vascular barrier integrity, and its deletion triggers neuroinflammation

TAR DNA-binding protein 43 (TDP-43) is a DNA/RNA-binding protein that regulates gene expression, and its malfunction in neurons has been causally associated with multiple neurodegenerative disorders. Although progress has been made in understanding the functions of TDP-43 in neurons, little is known about its roles in endothelial cells (ECs), angiogenesis, and vascular function. Using inducible EC-specific TDP-43-knockout mice, we showed that TDP-43 is required for sprouting angiogenesis, vascular barrier integrity, and blood vessel stability.

Postnatal EC-specific deletion of TDP-43 led to retinal hypovascularization due to defects in vessel sprouting associated with reduced EC proliferation and migration. In mature blood vessels, loss of TDP-43 disrupted the blood-brain barrier and triggered vascular degeneration. These vascular defects were associated with an inflammatory response in the CNS with activation of microglia and astrocytes. Mechanistically, deletion of TDP-43 disrupted the fibronectin matrix around sprouting vessels and reduced β-catenin signaling in ECs. Together, our results indicate that TDP-43 is essential for the formation of a stable and mature vasculature.

It is well known that low socioeconomic status correlates with a raised risk of age-related disease and mortality, though it is challenging to determine which of the possible causes are in fact more or less important. A web of correlations are linked to socioeconomic status: intelligence, access to medical services, education, personality traits, lifestyle choices, and more. Here the focus of the study is on location of residence as a marker of socioeconomic status, and in this context it is interesting to note the studies that have compared the differences in particulate air pollution versus mortality in wealthier versus poorer neighborhoods in US metropolitan areas. Higher particulate air pollution is by now a noted contribution to age-related disease and mortality, though clearly only part of the story when it comes to how wealth, status, and life expectancy are related.

Dementia risk may be elevated in socioeconomically disadvantaged neighborhoods. Reasons for this remain unclear, and this elevation has yet to be shown at a national population level. We tested whether dementia was more prevalent in disadvantaged neighborhoods across the New Zealand population (N = 1.41 million analytic sample) over a 20-year observation. We then tested whether premorbid dementia risk factors and MRI-measured brain-structure antecedents were more prevalent among midlife residents of disadvantaged neighborhoods in a population-representative NZ-birth-cohort (N = 938 analytic sample).

People residing in disadvantaged neighborhoods were at greater risk of dementia (hazard ratio, HR, per-quintile-disadvantage-increase = 1.09) and, decades before clinical endpoints typically emerge, evidenced elevated dementia-risk scores (CAIDE, LIBRA, Lancet, ANU-ADRI, DunedinARB; β 0.31-0.39) and displayed dementia-associated brain structural deficits and cognitive difficulties/decline. Disadvantaged neighborhoods have more residents with dementia, and decades before dementia is diagnosed, residents have more dementia-risk factors and brain-structure antecedents. Whether or not neighborhoods causally influence risk, they may offer scalable opportunities for primary dementia prevention.

Link: https://doi.org/10.1002/alz.13727

The growth of atherosclerotic plaques in blood vessels is harmful, not least because it restricts blood flow, even blocking entire vessels in the worst cases. The vast majority of cardiovascular mortality results from the rupture of fatty, unstable plaques, however, leading to stroke and heart attack when the fragments block downstream vessels. If the development of plaque instability could be slowed or reversed, this would have a sizable impact on cardiovascular mortality - even given that this goal is a step down from reversal of plaque in general. Thus researchers are interested in finding the mechanisms that determine whether a plaque is more fatty and less fibrous, and thus more prone to rupture.

Atherosclerosis is a chronic disease of the vascular wall driven by lipid accumulation and inflammation in the intimal layer of arteries, and its main complications - myocardial infarction and stroke - are the leading cause of mortality worldwide. Recent studies have identified triggering receptor expressed on myeloid cells 2 (TREM2), a lipid-sensing receptor regulating myeloid cell functions, to be highly expressed in macrophage foam cells in experimental and human atherosclerosis. However, the role of TREM2 in atherosclerosis is not fully known.

Here we show that hematopoietic or global TREM2 deficiency increased, whereas TREM2 agonism decreased, necrotic core formation in early atherosclerosis. We demonstrate that TREM2 is essential for the efferocytosis capacities of macrophages and to the survival of lipid-laden macrophages, indicating a crucial role of TREM2 in maintaining the balance between foam cell death and clearance of dead cells in atherosclerotic lesions, thereby controlling plaque necrosis.

Link: https://doi.org/10.1038/s44161-024-00429-9

Today's open access paper presents an interesting discussion of the apparent lack of age-related autoimmunity in centenarians. The immune system becomes ever more dysfunctional with age, and some of that dysfunction can take the form of maladaptive changes that either (a) allow the immune system to direct attack tissues or (b) disrupt important relationships between immune cells and the rest of a tissue. Far from all of these issues are well understood or even well identified as discrete problems distinct from the rest of degenerative aging. A potential type 4 diabetes was only comparatively recently discovered, for example.

The oldest of old people tend to be robust in comparison to age-matched peers who die at younger ages. In one sense this is self-evident, as they would have to be robust in order to avoid a higher risk of mortality that would lead to an earlier death. In another sense, it is interesting to examine the physiological and biochemical details of this robustness. That said, centenarians are rare survivors from a very large birth cohort, and it doesn't take much of a change in the odds of survival over decades of later life to tilt the characteristics of centenarians in one direction or another. Thus it isn't clear that discoveries made in long-lived people actually have much practical application to medicine; they may largely represent only small gains.

Still, as asked by the authors of today's paper, why is it the case that age-related autoimmunity seems absent from the oldest segment of the population? Is this actually an absence, or a case of too little examination of the fine medical details in these usually frail individuals? If it is an absence, what does that say about the function of the immune system in late life, and the details of the role of immune system alterations, damage, and adapative and maladaptive changes in age-related mortality?

Autoimmunity in centenarians. A paradox

Autoimmune diseases (ADs) constitute one of the most prevalent chronic conditions. During the aging process and through continuous exposure to various stressors, pathogens, and other environmental factors throughout life (i.e., exposome), accompanied by the aging of the immune system (i.e., immunosenescence) and the onset of age-related chronic diseases, a persistent proinflammatory systemic environment theoretically increases the probability of developing an AD. This is because the immune system's responsiveness would be lower and irregular when exposed to a greater number of stressors and causes of cellular dysregulation. For this reason, age has been considered to be an important risk factor for autoimmunity.

Aging implies a complex array of changes and remodeling in homeostatic mechanisms that control the immune system, both in terms of numbers and functions of the different cellular subsets. Rather than being a mere process of immunosenescence, age-related transformations redesign the immune architecture and the balance between proinflammatory and anti-inflammatory protective factors. Cellular senescence occurs in response to endogenous and exogenous stresses, including telomere dysfunction, oncogene activation, and persistent DNA damage. Immunosenescence includes three events: a reduction in immune response, an increase in the inflammatory and oxidation background (inflammaging and oxiinflammaging), and a production of autoantibodies.

However, there is a group of humans, increasingly observed, that contradicts this paradigmatic view, and whose health phenotype raises numerous questions for which there are currently no answers. Centenarians represent the most successful model of biological aging in humans. These individuals, who have a chronological age equal to or greater than 100 years, have special health characteristics, mostly partially known, that contradict the previously described theoretical concept of autoimmunity in the elderly.

Unfortunately, there is a lack of robust evidence describing or discussing autoimmunity in centenarians. Even studies describing the health phenotypes of centenarians worldwide report that the prevalence of ADs in this population is practically nil, except for some series mentioning imprecise data and methodology. Therefore, this field represents a niche of original, novel, and relevant knowledge for the in-depth understanding of new pathophysiological mechanisms, protective and risk factors for autoimmunity, based on the identification of new markers, signaling pathways, and targets related to aging, adaptation, or remodeling of the immune system. Herein we discuss current questions and gaps regarding the understanding of autoimmunity in centenarians, proposing possible hypotheses that would explain this scenario.

Stem cell therapies are one of the approaches to treating progressive loss of blood flow to tissues, such as results from severe atherosclerosis, in which important blood vessels are narrowed or even blocked. Unfortunately first generation stem cell therapies are variable in outcome, cellular senescence in cell cultures prior to transplantation is poorly controlled, and the transplanted cells die quite quickly. Thus even though the benefits of treatment arise from signaling generated by transplanted cells, rather than cell integrating into tissues, there is much that can be improved. One of the ways in which researchers are producing that improvement is via the use of scaffold materials to extend the lifespan of transplanted cells and better steer their behavior, as illustrated here.

Critical limb ischemia is a condition in which the main blood vessels supplying blood to the legs are blocked, causing blood flow to gradually decrease as atherosclerosis progresses in the peripheral arteries. Current treatments include angioplasty procedures such as stent implantation and anti-thrombotic drugs, but there is a risk of blood vessel damage and recurrence of blood clots, which is why there is a strong interest in developing a treatment using stem cells.

Stem cell therapies have high tissue regeneration capabilities, but when stem cells are transplanted alone, hypoxia at the site of injury, immune responses, and other factors can reduce cell viability and prevent the desired therapeutic effect. Therefore, it is necessary to develop a material that delivers stem cells using biodegradable polymers or components of extracellular matrix as a support to increase cell viability.

Researchers processed collagen hydrogels to micro-scale to create porous, three-dimensional scaffolds that are easy to inject in the body and have a uniform cell distribution. Collagen, a component of the extracellular matrix, has excellent biocompatibility and cellular activity, which can induce cell self-assembly by promoting interactions between the microgel particles and collagen receptors on stem cells. In addition, the spacing between microgel particles increased the porosity of the three-dimensional constructs, improving delivery efficiency and cell survival.

The microgel-cell constructs developed by the researchers expressed more pro-angiogenic factors and exhibited higher angiogenic potential than cell-only constructs. When microgel-cell constructs were injected into the muscle tissue of mice with critical limb ischemia, blood perfusion rate increased by about 40% and limb salvage ratio increased by 60% compared to the cell-only constructs, confirming their effectiveness in increasing blood flow and preventing necrosis in the ischemic limb.

Link: https://www.eurekalert.org/news-releases/1036996

Researchers here make an interesting discovery in rats, finding an age-related change in the structure of specific neurons that encourages greater intake of calories and dysfunctional metabolism by suppressing satiation feedback. In rats this mechanism can be manipulated by diet and genetics to alter the pace at which older rats become overweight and metabolically abnormal. As is often the case in research, this discovery is a proximate cause to the problem of metabolic regulation, and it is entirely unclear as to how the deeper mechanisms of aging, such as chronic inflammation, mitochondrial dysfunction, and so forth, are causing it or otherwise relate to it.

As we get older, we become more prone to being overweight and obesity. Obese people are more susceptible to diabetes, hyperlipidemia, and other chronic diseases. Previous studies have suggested that middle-age weight gain is caused by a decline in overall metabolism due to aging, but the mechanism was unclear. A protein called melanocortin-4 receptor (MC4R) detects overnutrition and regulates metabolism and appetite to prevent obesity. MC4Rs stimulate metabolism and suppress food intake in response to an overeating signal from melanocortin.

Initially, a research team examined the distribution of MC4Rs in the rat brain by utilizing an antibody they had developed specifically to make MC4Rs visible. They found that MC4Rs are present exclusively in primary cilia of specific groups of hypothalamic neurons. The team next investigated the length of the primary cilia that had MC4Rs (MC4R+ cilia) in the brains of 9-week-old (young) rats and 6-month-old (middle-age) rats. The team found that MC4R+ cilia in middle-aged rats were significantly shorter than those in young rats. Accordingly, the metabolism and the fat-burning capacity of middle-aged rats were much lower than those of young rats.

The team next analyzed MC4R+ cilia in rats under different dietary conditions. The results showed that MC4R+ cilia in rats on a normal diet gradually shortened with age. On the other hand, MC4R+ cilia in rats on a high-fat diet shortened at a faster pace, while those in rats on a restricted diet shortened at a slower pace. Interestingly, the team also found that MC4R+ cilia that once disappeared with age were regenerated in rats raised under two months of dietary restriction. In the study, the team also used genetic technologies (knockdown of CILK1) to make MC4R+ cilia shorter in young rats. These rats showed increased food intake and decreased metabolism, leading to weight gain.

Link: https://www.eurekalert.org/news-releases/1037463

Mitochondria are the power plants of the cell, primarily responsible for packaging adenosine triphosphate (ATP) molecules as chemical energy stores for use throughout the cell. Hundreds of mitochondria swarm inside every cell, the descendants of ancient symbiotic bacteria. These organelles retain many features characteristic of bacteria. For example, mitochondria contain a small circular genome, depleted of genes that have moved into the cell nucleus over evolutionary time. Mitochondria also constantly divide, fuse together, and swap component parts. Mitochondrial quality is controlled by the processes of mitophagy that recycle worn or damaged mitochondria, delivering them to a lysosome to be engulfed and then dismantled into raw materials.

Dysfunction of mitochondria is characteristic of aging. Cells in aged tissues exhibit changes in mitochondrial dynamics, failure of mitophagy, damage to mitochondrial DNA, increased oxidative stress as the result of changes in the way mitochondria produce ATP, and reduced ATP production. When taking place in all cells throughout a tissue, this has a profoundly harmful effect on tissue function. This is particularly true in energy-hungry tissues such as muscle and the brain. The latter is the subject of today's open access review paper, a look at what is known of the role of age-related mitochondrial dysfunction in the aging of the brain.

Mitochondrial Dysfunction: A Key Player in Brain Aging and Diseases

Despite the human brain weighing only 2% of the total body weight, almost 20% of the basal oxygen is consumed by this organ in order to produce enough energy for the approximately 86 billion neurons and 85 billion glial cells that comprise it. Glucose is the main source of energy in the adult brain and its oxidation produces ATP almost entirely through oxidative phosphorylation (OXPHOS) in the mitochondria, thus underpinning the importance of this organelle for brain homeostasis. Energy is constantly required to sustain the synthesis of neurotransmitters as well as to maintain the membrane potential needed for action potential propagation and synaptic transmission, including the re-uptake of neurotransmitters from the synaptic cleft.

A large body of evidence demonstrates that bioenergetic impairments as well as disturbances in the OXPHOS machinery of mitochondria occur in the brain during aging. Although efficient, OXPHOS produces reactive oxygen species (ROS) as a byproduct, and the brain is especially susceptible to oxidative damage because it contains a plethora of oxidizable substrates, such as fatty acids, an abundance of catalytic transition metals, and a high rate of oxygen consumption per gram of tissue. Several studies have demonstrated an association between the oxidative damage of DNA (8-OH-dG), lipids (MDA and 4-HNE), and proteins (carbonyls and protein 3-nitrotyrosine) with brain aging.

It has been proposed that the impairment of brain mitochondrial function during aging might be the result of the decreased electron transfer rate of Complex I and Complex IV. Interestingly, gene expression of mitochondrial subunits for Complexes I, III, IV, and V have been found to be down-regulated in old TG2576 mice and Ndufs4 knock-out mice, models of Alzheimer's disease pathology and of Complex I deficiency, respectively.

Importantly, the effects of neuronal oxidative stress are normally counteracted by a well-developed antioxidant system; however, during aging the antioxidant defense system may become overwhelmed. A shift to a pro-oxidized state, determined by a decrease in the GSH/GSSG ratio, with GSH serving as the body's "master" antioxidant and GSSG as the oxidized form of GSH, was found in forebrain and cerebellum from 21 month-old mice, as compared to 3 month-old controls. As the brain ages, the effects of oxidative stress on mtDNA may lead to mutations and deletions and subsequently impair the OXPHOS complexes, increase ROS production, and further exasperate oxidative stress levels. This vicious cycle may lead to decreased energy supply, increased susceptibility to apoptosis, and a progressive decline in tissue function. A 10-fold increase in mtDNA levels of 8-OHdG as well as elevated mtDNA point mutations and deletions in frontal cortex, substantia nigra, and putamen from elderly individuals above the age of 67 have been reported.

Mitochondrial quality control mechanisms, such as fusion, fission, and mitophagy, are important processes used to preserve cells against damage; however, reports indicate that as the mtDNA mutation load increases during aging these processes may begin to lose their efficiency. For example, Drp1, a protein essential for mitochondrial fission, has been shown to be down-regulated in old C57BL/6 mice, and its removal in adult mouse forebrain resulted in altered mitochondrial morphology and mitochondrial transport to the synapse, as well as decreased oxygen consumption and ATP production. Importantly, these findings suggest that mitochondrial dynamics, mitophagy, and biogenesis become impaired during aging, and may be involved in the pathogenesis of various neurodegenerative diseases.

The cost of obtaining transcriptomic and proteomic data, and then using machine learning techniques to develop insights based on that data, has fallen dramatically over the past decade. As a result there is a proliferation of signatures of aging and longevity, as many different research groups analyze many different large transcriptomic and proteomic databases. The example here is one of a number of such signatures created with the idea of finding potential targets for therapy. It is far from clear that one can alter any of the various protein levels related to aging and longevity and obtain meaningful benefits, however. A change can be a side-effect of aging, and end-stage consequence that causes few downstream consequences in and of itself, and will achieve little if reversed.

The identification of protein targets that exhibit anti-aging clinical potential could inform interventions to lengthen the human health span. Most previous proteomics research has been focused on chronological age instead of longevity. We leveraged two large population-based prospective cohorts with long follow-ups to evaluate the proteomic signature of longevity defined by survival to 90 years of age. Plasma proteomics was measured using a SOMAscan assay in 3,067 participants from the Cardiovascular Health Study (CHS) and 4,690 participants from the Age Gene/Environment Susceptibility-Reykjavik Study (AGES-Reykjavik). Logistic regression identified 211 significant proteins in the CHS cohort using a Bonferroni-adjusted threshold, of which 168 were available in the AGES-Reykjavik replication cohort and 105 were replicated.

The strongest associations in CHS that were replicated in AGES-Reykjavik were for GDF-15, NT-pro-BNP, b2-microglobulin, RNase 1, and HE4, providing confidence in such previously identified proteins in aging research. Less-established markers of mortality in the general population, such as angiopoietin-2, and PXDN, also had support in both cohorts. Our study design leveraging a longevity outcome, as opposed to overall survival only, paired with long follow-up time revealed that nearly half (269 out of 471) of proteins associated with overall survival were not associated with exceptional longevity in the CHS, though the strongest associations remained consistent between the two outcomes.

A larger share of significant proteins was associated with both overall survival and longevity in AGES-Reykjavik, which may have occurred due to increased power to detect significant associations in AGES-Reykjavik. This observation suggests that extrapolating findings from associations with overall survival to longevity might be inappropriate. Moreover, we demonstrate for the first time in proteomics studies of longevity that physical and cognitive function may partially mediate associations between proteins and longevity, and that the amount of mediation may depend in part on which particular functional measures are used in the analysis.

Link: https://doi.org/10.1111/acel.14136

There are many ways in which the aging of tissue makes cancer both more likely to occur and more aggressive once it does occur. Here researchers focus in on specific changes in aged skin tissue that make melanoma cancers more likely to become metastatic and spread to other organs. Interestingly, it is an indirect effect on cell signaling that is mediated by increased stiffness of the skin extracellular matrix, an issue in many aging tissues that has many root causes, not just the one noted here. Nonetheless, if metastasis could be shut down, then cancer would become a much more tractable problem, particularly if control of metastasis were to be combined with improved approaches to the early detection of cancer.

Previous research has shown that a protein called HAPLN1 helps maintain the structure of the extracellular matrix, a network of molecules and minerals that provide structural support, to keep the skin supple. As people age, they release less HAPLN1, which causes the skin to stiffen. A new study shows that reduced HAPLN1 indirectly increases ICAM1 levels by causing stiffening, which alters cellular signaling. The increase in ICAM1 contributes to angiogenesis, or the growth of new blood vessels that supply the tumors with nutrients and help them grow. The blood vessels are also leakier, making it easier for tumor cells to escape from the initial tumor site and spread to distant areas of the body.

Treating older mice with melanoma with drugs that block ICAM1, however, prevents these changes, shrinking their tumors and reducing metastasis, researchers demonstrated. The researchers are now studying ICAM1's activities to develop more precise ways of targeting it with drugs, which might lead to new approaches to treating older people with melanoma. The discoveries might also lead to new approaches to treating other age-related cancers. Previous therapies targeting growth factors that contribute to angiogenesis have failed in many tumor types, including melanoma. But ICAM1 provides a promising new target.

Link: https://www.eurekalert.org/news-releases/1037180

Today's post is a report from the community on the impact of taurine supplementation on a few biomarkers of interest. Taurine is a dietary amino acid, and circulating levels of taurine influence any number of biological processes. Taurine levels decrease with age in a variety of species; in humans circulating taurine is halved by age 50. You might recall that supplementation with taurine was demonstrated to modestly extend life in mice and improve health in old non-human primates. This may be largely due to enhanced performance of the antioxidant glutathione, and you might recall that other approaches to upregulation of glutathione activity have been shown to produce benefits in old humans, dampening oxidative stress and associated inflammation.

A few human clinical trials of taurine supplementation have been conducted, but the results are not all that conclusive, other than to demonstrate that this form of intervention is very safe. So why not give it a try, and see what results? If you look back in the Fight Aging! archives, you'll find an outline for a self-experiment with taurine supplementation. Taurine is cheap and readily available as as a supplement, and inexpensive blood tests can be used to assess outcomes. Here, the self-experimenter chose to focus on phenotypic age and the biomarkers used to construct this assessment of phenotypic age. Only one marker of oxidative stress was used, an assessment of circulating oxidized LDL particles.

• The self-experimenter was a vegetarian in his 50s.
• 3 grams per day of taurine was taken orally for 9 months.
• Diet and lifestyle was kept consistent, as much as possible in a busy life.

• Phenotypic age acceleration: -9.00 to -10.85 years
• Albumin: 4.1 to 4.3 g/dL (reference range is 3.6-5.1 g/dL)
• Creatine: 0.72 to 0.65 mg/dL (desired range is 0.70-1.30 mg/dL)
• Fasting Glucose: 93 to 90 mg/dL (desired range: 65-99 mg/dL)
• C-Reactive Protein: 0.30 to 0.34 mg/L (considered low risk under 1.00 mg/L)
• Alkaline Phosphatase (ALP) 53 to 50 U/L (reference range is 35-144 U/L)
• Lymphocyte Percentage 33.1% to 40.7% (normal range is 20% to 40%)
• Mean Cell Volume (MCV): 87.8 to 88.6 fL (desired range is 80.0-100.0 fL)
• Red Cell Dist Width (RDW): 13.3% to 13.5% (desired range is 11.0-15.0%)
• White Blood Cells (WBC): 4.8 to 3.9 Thousand/uL (reference range is 3.8-10.8 Thousand/uL)

• Taurine: 43.6 to 114.9 umol/L (reference range is 29.2-132.3 umol/L)
• Oxidized LDL: 105 to 82 ng/mL (reference range is 10-170 ng/mL)
• LDL and HDL cholesterol levels were largely unchanged.
• Absolute Lymphocytes: 1589 to 1587 cells/uL (desired range is 850-3900 cells/uL)
• Absolute Monocytes: 312 to 269 cells/uL (desired range is 200-950 cells/uL)
• Absolute Neutrophils: 2832 to 1981 cells/uL (desired range is 1500-7800 cells/uL)
• Lymphocyte: Monocyte Ratio: 5.1 to 5.9
• Other complete blood count statistics were largely unchanged.

Going from the data provided, the supplementation successfully increased a low circulating taurine level to a high circulating taurine level as intended, and modestly reduced phenotypic age. The most interesting change seen in the biomarkers making up the phenotypic age metric is the increased lymphocyte percentage. This change was entirely due to the absolute neutrophil count decreasing from 2832 to 1981 cells/uL, while other absolute counts for white blood cell types remained much the same. Neutrophil counts can be raised temporarily by transient infection or inflammation, but per the self-experimenter, ~2800 had been a fairly consistent level for absolute neutrophil count for some years prior to this self-experiment. The observed reduction is thus a novel change, and likely due to the taurine supplementation.

A second interesting point is the reduction in oxidized LDL, a marker of oxidative stress and also a contributing factor in the development of atherosclerosis. As a sidebar, also note the low creatine levels, characteristic of vegetarians since dietary creatine is mostly found in meat.

The modestly favorable results shown here form only a single data point and should be taken as an anecdote, of course. It would be interesting to see the results of a few hundred participant clinical trial of taurine supplementation that focused on the various modern approaches to measuring biological age, such as epigenetic clocks. One shouldn't expect there to be a rush to do this, however. Trials are expensive, and there is little spare funding to be found in the business of selling well-established supplement compounds. At the end of the day modest effect sizes are modest effect sizes, and we'd like to focus on better approaches to the problem of aging - but if the intervention is both very cheap and very safe, then it may well be worth the effort to further establish the degree to which it can be useful.

Telomeres are repeated sequences at the end of chromosomes. A little of that length is lost with each cell division, and in this way telomere length acts as a countdown. Somatic cells become senescent or self-destruct when telomere length becomes too short, thanks in large part to the activity of TP53. This is a protective mechanism, removing cells that can become cancerous or otherwise harmful. Stem cells employ telomerase to maintain long telomeres, and supply a tissue with new daughter somatic cells to take the place of those lost to telomere shortening. Thus a tissue has some turnover of cells, allowing a degree of protection from the most harmful cell malfunctions. This study provides some insight into how these relationships play out in practice by sabotaging telomerase and p53, and observing the results.

Telomerase activity is restricted in humans and telomere attrition occurs in several tissues accompanying natural aging. Critically short telomeres trigger DNA damage responses and activate p53 which leads to apoptosis or replicative senescence. These processes reduce cell proliferation and disrupt tissue homeostasis, thus contributing to systemic aging. Similarly, zebrafish have restricted telomerase expression, and telomeres shorten to critical length during their lifespan.

Telomerase-deficient zebrafish (tert -/-) is a model of premature aging that anticipates aging phenotypes due to early telomere shortening. tert -/- zebrafish have impaired cell proliferation, accumulation of DNA damage markers and p53 response. These cellular defects lead to disruption of tissue homeostasis, resulting in premature infertility, gastrointestinal atrophy, sarcopenia, and kyphosis. Such consequences contribute to its premature death.

Here we reveal a genetic interdependence between tp53 and telomerase function. Mutation of tp53 abrogates premature aging of tert -/- zebrafish, prolonging male fertility and lifespan. However, it does not fully rescue healthspan. tp53mut tert -/- zebrafish retain high levels of inflammation and increased spontaneous cancer incidence. Conversely, loss of telomerase prolongs the lifespan of tp53mut single mutants. Lack of telomerase reduces two-fold the cancer incidence in double mutants and increases lifetime survival. Thus, we observe a reciprocal rescue of tp53mut and tert -/- that ameliorates lifespan but not spontaneous cancer incidence of tp53mut, likely due to higher levels of inflammation.

Link: https://doi.org/10.1038/s41598-024-56153-8

Researchers here identify a mechanism by which the practice of calorie restriction promotes muscle stem cell function, and thus repair and maintenance of muscle tissue. In animal studies calorie restriction is shown to produce both (a) a short-term effect associated with improved regeneration, and (b) a long-term effect in the sense of slowing the progressive loss of muscle mass and strength leading to sarcopenia. The research community will no doubt build on the findings here to suggest pharmaceutical approaches to mimic this aspect of calorie restriction.

Using an unbiased proteomics approach, we report here that calorie restriction (CR) promotes a hypersecretion of proteins from the liver, including those involved in coagulation and fibrinolysis. We also demonstrated the role of liver-derived plasminogen in mediating satellite cell expansion and enhanced muscle regeneration during CR. We showed that the mediation was accomplished by an upregulation of the plasminogen receptor Plg-RKT specifically on muscle satellite cells, promoting downstream ERK signaling and subsequent proliferation. We therefore propose that CR induces a distinct crosstalk between liver and muscle that increases muscle resilience.

Using the MetRSL274G/bio-orthogonal non-canonical amino acid tagging (BONCAT) model to characterize an organ-specific secretome in vivo, our study aimed to investigate the systemic and extracellular effects of CR and how this could alter tissue resilience. We chose to investigate metabolic tissues with known effects of CR, including liver, skeletal muscle, and adipose tissue. We were intrigued by the induction of secreted proteins from the liver with CR, which was not evident in proteins secreted by either adipose or muscle tissues. The induction of the secretome was observed just 2 weeks after CR and continued throughout the 3-month CR period.

Interestingly, CR increased secretion of proteins associated with the resolution of both coagulation and hemostasis. Although not the focus of this paper, these findings suggest increased secretion of fibrinolytic factors from the liver as a possible mechanism to improve cardiovascular health with CR, given that elevated hemostatic factor levels are typically associated with worsened clinical cardiovascular outcomes, such as increased risk of cardiovascular death. Conversely, CR dampened secretion of proteins associated with increased inflammation, which is consistent with known anti-inflammatory effects of CR and further validates our proteomics approach.

To demonstrate the relevance of our findings to human biology, we analyzed tissues from the CALERIE trial of human CR. We observed replication of many of the mouse phenotypes, including increased circulating plasminogen, decreased PAI-1, satellite cell expansion, and increased Plg-RKT expression on the satellite cells of human CALERIE study participants. This study also reports the expansion of satellite cells in human muscle with CR. This finding is critical to suggest translational relevance to the rodent data observed for more than a decade. Moreover, the increased expression of the plasminogen receptor Plg-RKT observed on human satellite cells during CR provided additional support for the theory that our rodent model is relevant to human biology.

Link: https://doi.org/10.1016/j.celrep.2024.113881

The balance of microbial populations making up the gut microbiome changes with age in ways that provoke chronic inflammation, as well as reduce production of beneficial metabolites. In recent years, researchers have shown that Alzheimer's patients exhibit a distinctly dysregulated gut microbiome in comparison to other older individuals. This raises the question of whether there is a significant contribution to risk of Alzheimer's resulting from specific changes in microbial populations of the intestinal tract. Alternatively, since the immune system is responsible for gardening the gut microbiome, eliminating undesirable microbes, does the Alzheimer's gut microbiome reflect a specific or greater incapacity of the immune system that independently drives both changes in the gut microbiome and the development of neurodegeneration?

In today's open access paper, researchers discuss the path towards a better understanding of the role of the gut microbiome in Alzheimer's disease. At present a correlation is established, but how to move beyond that to identify specific mechanisms and microbial populations? One possible approach to the question of causation is to attempt to reverse age-related or disease-related changes in the gut microbiome via fecal microbiota transplant from a young, healthy individual. Finding out whether this improves Alzheimer's patient outcomes, and to what degree, would be an important step forward. If the problem is that microbes make their way from a leaky gut to the brain and there causing issues, changing the gut microbiome may not help in later stages of the condition, however. If the problem is altered inflammatory signaling and metabolite production in the intestines, then changing the microbiome may be more helpful.

New approaches for understanding the potential role of microbes in Alzheimer's disease

This article summarizes research presented at the virtual symposium and workshop, "New Approaches for Understanding the Potential Role of Microbes in Alzheimer's Disease." The objective of these events was to review the evidence base and catalyze research to address knowledge gaps in the hypothesis that infections or microbes play some causative role in the development or progression of Alzheimer's disease. Alzheimer's disease is a complex disease; this symposium was rooted in an understanding that its pathogenesis could be triggered by both microbe-dependent and microbe-independent pathways and the two are not mutually exclusive.

The symposium was introduced with a keynote lecture describing the origins and accumulating evidence for the theory around amyloid-β (Aβ) as an antimicrobial protein that protects the brain against infection. The next session highlighted epidemiological and mechanistic data for a potential link between COVID-19 and Alzheimer's disease. The program then featured brief lectures that explored these topics: single-cell genomic studies in Alzheimer's disease that may suggest immune response to microbes, a potential role for antiviral vaccines in Alzheimer's disease, investigations into which microbes could cause Alzheimer's, activation of endogenous retroviruses in tauopathy, and gut-microbe brain communications.

Speakers presented emerging evidence that COVID-19 infection confers increased risk of dementia and discussed how COVID-19 may promote AD pathology. Although no definitive evidence exists to prove or disprove the direct involvement of any specific microbe in human AD, speakers agreed that there are multiple plausible ways that microbes could be implicated. One model that has been extensively investigated that has direct relevance to central nervous system (CNS)/microbiome interactions are the effects of lipopolysaccharide (LPS) on blood-brain barrier (BBB) functions. LPS is derived from gram negative bacteria and is a powerful activator of the innate immune system. LPS's actions either directly on BBB functions or indirectly through the induction of the release of cytokines and other immune-related substances affect the CNS.

Data also shows that some microbes appear to be overabundant in Alzheimer's brains, sometimes by large margins. These microbes are species typically encountered in human infections - for example, Streptococcus and Staphylococcus, as well as several Aspergillus-like, Candida-like, and Cryptococcus-like fungi, of interest because Cryptococcus in particular is a known cause of dementia 'masquerading' as Alzheimer's disease. Infections appeared to be locally restricted - some samples with a heavy microbial burden were adjacent to tissues largely lacking microbes. Conversely, some atypical microbes were seen in more than one brain region, indicative of in vivo spreading. However, whether microbes cause Alzheimer's remains an open question. One way to evaluate this would be to determine which brain microbes are present in each individual (perhaps through analysis of cerebrospinal fluid), and then to explore whether appropriate therapy might mitigate or slow Alzheimer's disease.

Researchers here report on a way to reverse some of the age-related dysfunction observed in the hematopoietic stem cell population resident in bone marrow. These cells are responsible for generating red blood cells and immune cells. Some fraction of the age-related decline in immune function derives from issues in the hematopoietic cell populations originating with hematopoietic stem cells. It seems that hematopoietic stem cells have a distinct iron metabolism, and iron accumulation produces dysregulation in these cells. Reducing the presence of iron in hematopoietic stem cells reverses some of these changes. In the bigger picture, iron is connected to aging, and global reductions in iron levels achieved via a variety of methods have been demonstrated to modestly slow life in short-lived laboratory species such as flies and worms. Just how much of that effect derives from improved hematopoietic and immune function is an open question.

Mechanisms governing the maintenance of blood-producing hematopoietic stem and multipotent progenitor cells (HSPCs) are incompletely understood, particularly those regulating cell fate, ensuring long-term maintenance, and preventing aging-associated stem cell dysfunction. We uncovered a role for transitory free cytoplasmic iron as a rheostat for adult stem cell fate control. We found that HSPCs harbor comparatively small amounts of free iron and show the activation of a conserved molecular response to limited iron - particularly during mitosis.

To study the functional and molecular consequences of iron restriction, we developed models allowing for transient iron bioavailability limitation and combined single-molecule RNA quantification, metabolomics, and single-cell transcriptomic analyses with functional studies. Our data reveal that the activation of the limited iron response triggers coordinated metabolic and epigenetic events, establishing stemness-conferring gene regulation. Notably, we find that aging-associated cytoplasmic iron loading reversibly attenuates iron-dependent cell fate control, explicating intervention strategies for dysfunctional aged stem cells.

Link: https://doi.org/10.1016/j.stem.2024.01.011

This popular science article is a reminder that all too little in this world happens for entirely rational reasons. Drugs aimed at slowing or reversing the age-related loss of muscle mass leading to sarcopenia are presently under development by a number of companies, though none of the candidates discussed are producing effect sizes that look very favorable in comparison to the effects of resistance exercise. These efforts will likely benefit from the present manufactured hype that attends the use of antidiabetic GLP1 receptor agonists for weight loss, as one of the side-effects of this drug is modest loss of muscle mass. To the extent that this aids in the development of meaningful ways to treat sarcopenia, fair enough. But one is left with the lingering feeling that perhaps this is not the best way to make progress. Will these companies continue to work on age-related disease, or will they just get shunted into the non-aging-related hype of the day? The latter is not a small risk.

Even as obesity treatments Ozempic and Mounjaro continue their surge in popularity, drug hunters are asking whether it is possible for people to lose weight on these glucagon-like peptide-1 (GLP-1) agonists without losing muscle. Drug candidates originally designed to build, preserve or regenerate skeletal muscle for treating muscle atrophy in degenerative conditions or ageing are now being tested in combination with GLP-1 agonists used for obesity to spare lean muscle.

One such biotech is BioAge Labs. In February, the company announced a $170-million series D financing, which will allow it to combine its apelin receptor agonist azelaprag (BGE-105) with Eli Lilly's GLP-1 agonist Mounjaro (tirzepatide) in phase 2 studies. The combination preserved lean body tissue in phase 1 studies and animal models and boosted weight loss by 10-15% compared with Mounjaro alone. The news came on the heels of Regeneron's intention to launch a phase 2 trial pairing the company's muscle-preservation monoclonal antibodies (the anti-myostatin trevogrumab and the anti-activin A garetosmab) alongside Novo Nordisk's Ozempic (semaglutide).

Immunis and Juvena Therapeutics are zooming in on the muscle stem cell secretome - the collection of proteins, including growth factors, cytokines, chemokines, and extracellular matrix components, secreted by muscle cells. The secretome kicks in to boost proliferation in response to exercise or to enhance cellular interactions to accelerate wound healing, for example, and it declines markedly with age. For Paris-based Biophytis, the focus is on the shared pathways between age-related sarcopenia and neuromuscular disease such as Duchenne muscular dystrophy. Its lead candidate is ruvembri (BIO101), a small molecule that targets the MAS receptor, which is present in cardiorespiratory and skeletal muscles. MAS activates the AKT and AMPK kinase pathways downstream, stimulating protein synthesis and energy production, respectively.

Companies with muscle-building drugs are now blazing a trail in obesity studies to counter the skeletal muscle atrophy that accompanies fat-loss treatments. The often dramatic weight loss experienced by people who have undergone bariatric surgery or are taking GLP-1 agonists such as Mounjaro and Ozempic leads to the loss of muscle as well as fat. As a consequence, biopharma companies are on the lookout for drugs to use alongside GLP-1 agonists to preserve lean muscle mass.

Link: https://doi.org/10.1038/s41587-024-02176-5

Reprogramming using overexpression of the Yamanaka factors captures a portion of the changes that take place in early embryonic development, in the creation of youthful embryonic stem cells from old germline cells. Reprogramming can erase cell state, slowly turning adult somatic cells into what are known as induced pluripotent stem cells, analogous to embryonic stem cells. But researchers have realized that the potentially far more interesting outcome is that prior to transformation, cells shift their epigenetic patterns towards a more youthful configuration. This reverses age-related mitochondrial dysfunction, and likely many other detrimental changes in cell behavior.

Thus the focus of reprogramming in academia and industry is shifting from the production of pluripotent cells for research and cell therapies to the rejuvenation of cells in aged living tissue. Researchers are earnestly seeking therapeutic modalities that can strike the balance between enough exposure to reprogramming factors to produce epigenetic rejuvenation, but not so much as to cause cells in tissue to become pluripotent and cancerous. This partial reprogramming is a challenge, but serious efforts to reach this goal are underway.

It has long seemed that the first rejuvenation therapies to reach the clinic and be demonstrated to slow aging in humans would be forms of senolytic drug capable of selectively clearing senescent cells. Groups working on partial reprogramming appear to be catching up rapidly, however. Efforts to build therapies atop the present understanding of partial reprogramming are now backed by massively greater funding than senolytic research and development. The field is moving rapidly as a consequence. With this as a background, the authors of today's open access review paper cast an eye over the present state of partial reprogramming as a basis for rejuvenation. It is an interesting read.

The long and winding road of reprogramming-induced rejuvenation

Epigenetic biomarkers of aging (aging clocks) can predict biological age through a variety of training approaches, even when based only on the variance of DNA methylation during aging. Interestingly, reacquisition of the lost epigenetic information may be observed during the natural rejuvenation process that occurs during early embryogenesis as well as during cell reprogramming. These strategies are in line with the notion of reprogramming-induced rejuvenation (RIR), a recent discovery wherein old cells can revert to a younger state upon transcription factor or chemical treatments. RIR is commonly accomplished through partial cell reprogramming, a method in which cells transiently undergo an induced pluripotent stem cell (iPSC) reprogramming. In this perspective, we discuss recent advances in this area, offer insights how they are related to the nature of aging and rejuvenation, and highlight potential advantages and drawbacks of this RIR and its translational potential.

It was shown that partial cell reprogramming can enhance the physiological function of human muscle stem cells, ameliorate the aging mouse transcriptome and metabolome in vivo, rejuvenate human dermal fibroblasts on a multi-omics level, and reverse the epigenetic clock in vitro. Furthermore, partial reprogramming can restore visual function in mice, prevent age-related physiological changes, and extend the remaining lifespan in wild-type mice. Present evidence suggests that pluripotency is not inherently linked to the rejuvenation process. However, it remains unclear whether pluripotency or certain transitionary cell states can be completely uncoupled from rejuvenation. A key question to be investigated is whether certain components contributing to biological age reversal can rejuvenate the entire epigenome or only certain loci.

There are legitimate concerns about the safety of Yamanaka factor-mediated partial reprogramming. To translate research in the field into clinical therapies, more research on the roadmap of partial reprogramming needs to be conducted. Furthermore, to better evaluate the results of in vivo cyclic reprogramming studies, in vitro cyclic reprogramming must be performed, and the difference between cyclic and continuous partial reprogramming must be identified. In conclusion, while partial reprogramming holds great therapeutic potential, the real focus should be on rejuvenation research, defining its nature and ways to quantify it. Another critical issue is the ability to quantify biological age as reprogrammed older cells acquire younger states. Understanding rejuvenation is also key to translational success, as benefits of age reversal must be considered against risks. More research into safety and tissue-specific responses of this technique are required.

Researchers here report on work that identifies SOX17 inhibition as a potential way to attack colon cancer in its early stages. Any successful cancer must have adopted one or more ways to suppress the immune system in order to grow past the earliest stages of a few cancerous cells. Interfering in those suppression mechanisms is a potential basis for therapy, as the researchers demonstrated here. Whether or not this line of work will make much further depends on whether an economically viable approach to SOX17 inhibition can be found, and whether or not it is a good target for many other forms of cancer.

Colon cancer usually arises in long-lived cells called intestinal stem cells, whose job is to continually regenerate the lining of the intestines. To learn more about how these precancerous growths evade the immune system, the researchers used a technique they had previously developed for growing mini colon tumors in a lab dish and then implanting them into mice. In this case, the researchers engineered the tumors to express mutated versions of cancer-linked genes Kras, p53, and APC, which are often found in human colon cancers.

Once these tumors were implanted in mice, the researchers observed a dramatic increase in the tumors' expression of SOX17. This gene encodes a transcription factor that is normally active only during embryonic development, when it helps to control development of the intestines and the formation of blood vessels. The researchers' experiments revealed that when SOX17 is turned on in cancer cells, it helps the cells to create an immunosuppressive environment. Among its effects, SOX17 prevents cells from synthesizing the receptor that normally detects interferon gamma/en.wikipedia.org/wiki/Interferon_gamma">interferon gamma, a molecule that is one of the immune system's primary weapons against cancer cells.

Without those interferon gamma receptors, cancerous and precancerous cells can simply ignore messages from the immune system, which would normally direct them to undergo programmed cell death. Without interferon gamma signaling, cancer cells also minimize their production of molecules called MHC proteins, which are responsible for displaying cancerous antigens to the immune system. The cells' insensitivity to interferon gamma also prevents them from producing immune molecules called chemokines, which normally recruit T cells that would help destroy the cancerous cells.

When the researchers generated colon tumor organoids with SOX17 knocked out, and implanted those into mice, the immune system was able to attack those tumors much more effectively. This suggests that preventing cancer cells from turning off SOX17 could offer a way to treat colon cancer in its earliest stages. As part of their study, the researchers also analyzed gene expression data from patients with colon cancer and found that SOX17 tended to be highly expressed in early-stage colon cancers but dropped off as the tumors became more invasive and metastatic.

Link: https://news.mit.edu/2024/how-early-stage-cancer-cells-hide-immune-system-0228

In recent years, researchers have attempted to provoke the regeneration of lost sensory hair cells in the inner ear, a potential treatment for forms of deafness. Various genes related to the creation of these cells during development have been identified, and gene therapy interventions attempted in animal models. Progress has been made, but it is incremental, and the results not yet satisfactory. Noted here is a recent example of this sort of work, in which a cocktail of genes is employed rather than focusing on single gene interventions.

The transcription factors (genes) Gfi1, Atoh1, Pou4f3, and Six1 (known collectively as GAPS) are important for the development and survival of hair cells. Previous research trying to regenerate hair cells in mature damaged ears by using a single transcription factor, Atoh1, produced very few cells. It also failed to produce new hair cells in severely injured organs of Corti, especially those with flat epithelium, a condition where sensory hair cells and supporting cells in the cochlea are lost and the organ of Corti turns into a simple flat layer of cells.

Studies in vitro suggested using combinations of transcription factors could be more effective than any single factor. We looked at the effects of overexpressing the GAPS genes in the ears of mature guinea pigs that were deafened and had flat epithelium. Seven days after deafening, adenovirus vectors carrying GAPS were injected into the inner ear scala media (cochlear duct) and successfully expressed in the flat epithelium. One or two months later, we observed cells expressing the protein Myosin VIIa, which marks hair cells. Surprisingly, most of these cells were in regions under the flat epithelium, not within it. Two months after treatment, we saw that some GAPS-treated guinea pigs had a statistically significant increase in new hair cell-like cells compared with controls.

In summary, our results showed that overexpression of GAPS enhances the potential for generating new hair cell-like cells in a severe inner ear lesion model characterized by flat epithelium in the guinea pig, compared with using Atoh1 alone. The new hair cells need to connect with nerve fibers to potentially restore hearing. We saw some promising signs of nerve regrowth, but more research is needed to determine if the new cells can signal to auditory nerves, even in their unusual location.

Link: https://hearinghealthfoundation.org/blogs/combination-of-four-genes-may-help-regrow-new-auditory-hair-cells-in-mammals

The hippocampus in the brain is vital to cognitive functions involving learning and memory. In today's open access paper, researchers review the evidence for the hippocampus to be particularly vulnerable to damaging mechanisms, including those involved in aging. It is tentatively suggested that physiological and biochemical differences in the hippocampus point to a greater fragility of the hippocampal blood-brain barrier as a common thread underlying pathological changes observed in aging and Alzheimer's disease. The blood-brain barrier is a specialized layer of cells that wrap blood vessels passing through the central nervous system. Its purpose is to restrict traffic of molecules and cells between the bloodstream and the brain, to maintain the brain's comparative isolation from much of the biochemistry of the rest of the body.

It is well established that the blood-brain barrier becomes dysfunctional in later life, as is the case for all other complex structures in the body. It leaks, allowing cells and molecules into the brain to cause local inflammatory reactions and other damage. The causes of this leakage are a complex web of interactions stretching from fundamental mechanisms of aging through changes in gene expression and altered cell behavior. As for the rest of aging, there is no good map to link what is known of the root causes of aging to what is known of the way in which cells in the blood-brain barrier become dysfunctional. This is why many in the community argue for a greater focus on addressing the root causes rather than on continued efforts to understand how exactly those root causes produce degenerative aging, in detail. If so much time and funding is going to be expended on the problem of aging, let it be on projects that have the hope of producing rejuvenation therapies rather than merely greater understanding.

Vulnerability of the Hippocampus to Insults: Links to Blood-Brain Barrier Dysfunction

The hippocampus, a medial temporal lobe structure that is a critical substrate (i.e., central nervous system component) that underlies learning and memory functions, can be adversely affected by a wide range of pathogens, neurotoxins, diseases, injuries, and environmental insults. It has often been suggested that the harmful effects of these insults may be greater on the hippocampus compared to other brain areas. However, there has been no systematic examination of this claim. An important reason to conduct this examination is that Alzheimer's disease and the severe dementia it causes are characterized by extensive hippocampal pathophysiology. It may be that insults that impair hippocampal functioning earlier in life may accelerate the emergence of more extensive hippocampal pathologies that could increase the risk of serious late-life cognitive decline.

One purpose of this review is to assess the vulnerability of the hippocampus to the most prevalent types of insults in multiple biomedical domains (i.e., neuroactive pathogens, neurotoxins, neurological conditions, trauma, aging, neurodegenerative disease, acquired brain injury, mental health conditions, endocrine disorders, developmental disabilities, nutrition) and to evaluate whether these insults affect the hippocampus first and more prominently compared to other brain loci. A second purpose is to consider the role of hippocampal blood-brain barrier (BBB) breakdown in either causing or worsening the harmful effects of each insult. Recent research suggests that the hippocampal BBB is more fragile compared to other brain areas and may also be more prone to the disruption of the transport mechanisms that act to maintain the internal milieu. Moreover, a compromised BBB could be a factor that is common to many different types of insults.

Our analysis indicates that the hippocampus is more vulnerable to insults compared to other parts of the brain. Our findings also indicate that hippocampal vulnerability to many of these insults is accompanied by a loss of BBB integrity in this region. For some of these insults, there was evidence that weakening of the hippocampal BBB occurred before and was more pronounced compared to the BBBs of other brain areas. These conclusions are limited, especially when considering the hippocampal BBB, by a lack of relevant data or by equivocal findings, with respect to the effects of some insults. In addition to the need to more rigorously test the notion of unique hippocampal vulnerability, we conclude that addressing the questions of how the protections afforded by the hippocampal BBB are compromised and how that weakening impairs hippocampal functioning are research goals of major significance, given the wide range of insults to which the hippocampus is vulnerable.

Therapies that reuse existing drugs with sizable bodies of human data tend to move more rapidly to the clinic than is the case for better, more ambitious approaches that break new ground. Greater speed in reaching the clinic means a lower cost of development, and this economic incentive is why so much of clinical development consists of drug reuse and only modestly effective therapies. In the case of sarcopenia, the age-related loss of muscle mass and strength, sizable funding is presently devoted to the development of small molecule therapies that do not produce greater gains than resistance exercise. A good deal of what we might think of as muscle aging is in fact disuse. More generally, and not just in the matter of sarcopenia, it would be good to see greater ambition, more development of first in class therapies in the research and development community - but people follow incentives, particularly when a great deal of funding is involved.

Rejuvenate Biomed, a pioneering clinical-stage platform and pipeline company committed to enhancing lifelong health through innovative therapeutics, today announces breakthrough functional outcome results from its Phase 1b trial of lead candidate RJx-01 for the treatment of sarcopenia. RJx-01 is a proprietary combination of metformin and galantamine that was identified by the company's in-house drug discovery platform and has shown to have beneficial effects on various preclinical models of sarcopenia. The recent exploratory clinical trial results, which follow earlier confirmation of safety, tolerability, and pharmacokinetics, highlight the potential of RJx-01 in addressing the unmet need for effective sarcopenia treatments.

Participants with disuse-induced sarcopenia treated with RJx-01 exhibited a promising improvement in muscle strength recovery compared to the placebo group. This beneficial effect, assessed through isometric dynamometry, underscores the ability of RJx-01 to promote muscle strength improvement. Treatment with RJx-01 led to an important improvement of leg acceleration, assessed through isokinetic dynamometry. The ability to accelerate the limb rapidly is important for functional movement in daily activities and is pivotal in mitigating fall risks. Neuromuscular fatigue was assessed by monitoring muscle parameters during a series of leg exercises. Participants receiving RJx-01 showed a reduced propensity for fatigue indicating that RJx-01 can promote physical activities such as walking.

Link: https://www.rejuvenatebiomed.com/en/news/clinical-trial-demonstrates-the-therapeutic-potential-of-rjx-01-in-sarcopenia

The development of drugs to force blood vessels into greater dilation, thereby lowering blood pressure, remains a popular ongoing concern despite the large number of such drugs already in use. Raised blood pressure causes significant downstream harm to the vasculature and surrounding delicate tissues in the body, enough that reductions in mortality can be achieved by forcing blood pressure reductions even without addressing the underlying mechanisms of aging that cause vascular stiffness. The materials here are a good example of the way in which early stage drug discovery takes place these days. Researchers start with a protein or protein interaction, then look for small molecules that (a) stimulate or interfere in that interaction in some way and (b) manage to do so with minimal side-effects and few to no other interactions.

The TRPV2 ion channel is formed by proteins in the membrane of some cells. When activated, they allow the entry of positive ions from the extracellular environment, changing the state of the cell and temporarily modifying aspects such as its ability to replicate, contract (in the case of a muscle cell) or even causing its death.

In a first study, the mechanisms involved in the contraction and relaxation of blood vessels by TRPV2 activation were analyzed in male mice. The researchers saw that TRPV2 produces multiple effects in different layers of the blood vessel, resulting in vasodilation. "This is important because it is the first time that the processes triggered by the activation of TRPV2 in blood vessels have been identified and have been described as leading to their dilation. This study represents a very important starting point for using this TRPV2 activation as a therapeutic strategy against diseases that cause excessive vasoconstriction, such as hypertension."

In a second study, the research group used computational techniques to identify a set of 270 molecules that, due to their physical and chemical characteristics, could interact with TRPV2, and grouped them by families according to how each of these molecules would bind to TRPV2. Then, by expressing the TRPV2 protein in yeast, a screening system was designed to test its effects. This made it possible to find a molecule (4-piperidin-1-sulfonyl-benzoic acid) capable of activating this protein more powerfully than the only drug known so far to do so: probenecid. "The activation of TRPV2 produced by the new molecule identified in this study has a very interesting vasodilator effect that could be used in the future as an antihypertensive therapy."

Link: https://www.uab.cat/web/newsroom/news-detail/new-therapeutic-approaches-for-hypertension-through-trpv2-proteins-1345830290613.html?detid=1345911637048

The primary problems with drug development are self-evident from the data. Firstly the process of drug development has become enormously more expensive over the past seventy years, a period in in which rapid technological progress has diminished the cost and effort required for any task in pharmacology and biotechnology by orders of magnitude. Secondly, the pace at which useful new medicines emerge in the clinic has diminished considerably, over the same period of technological progress in which the bounds of the possible have opened up enormously. The article I'll point out today is well worth reading, a lengthy treatment of these problems and the various viewpoints on what has caused the present dismal state of drug development. I am not sympathetic to the argument that drug development has become inherently harder for technical reasons. I am sympathetic to the viewpoint that regulation and the inherent waste and misaligned incentives present in governments and other large organizations are to blame.

Given that the pace of drug development in the longevity industry is an existential question for all of us, determining how long and in what state of health we will live, it becomes ever more important to ask how the present dismal state of drug development can be changed for the better. How can it be made faster and cheaper to produce new medical technologies? Or to put it another way, how can we get rid of the ball and chain that has been applied to the process of producing new medical technologies? Working within the system has failed dramatically. Some well-funded groups in the US have tried over the past twenty years, a period of time in which the regulatory cost imposed on medical development by the FDA has doubled. Consider the past efforts of FasterCures for example. Given this, and the many other examples of failure to change bad institutions from the inside, I believe that the only viable way forward to create meaningful change in medical regulation in the wealthier regions of the world is to produce competition through medical tourism.

This means more than just a larger medical tourism industry as it presently exists, because while that industry managed to accelerate the acceptance and regulatory approval of first generation stem cell therapies, that change was still too little and too slow. Forms of organization are lacking in the medical tourism industry, which remains small and disorganized. For example, there is a lack of hybrid organizations that combine aspects of venture capital, clinical business, preclinical development, and respected reviewer of data. The Longevitytech.fund (venture capital and clinical business) and the biotech side of the Próspera project (real estate investment, clinical business, clinical trial infrastructure) are examples of steps in this direction. The part that remains missing is a robust way for the medical tourism industry to produce reputable human data, via the existence of organizations that provide reputation, trust, and value for the industry without turning into just another mini-FDA, beholden to its own interests above those of the field.

The pharma industry from Paul Janssen to today: why drugs got harder to develop and what we can do about it

In 1953, aged 27, Paul Janssen set up the research laboratory on the third floor of his parents' Belgian drug import firm from where he would grow his eponymous pharmaceutical company. In the years between the 50s and 90s when he was most active, Janssen and his team developed over 70 new medicines, many of which are still in use today. Such prolificacy is unlikely to be repeated any time soon; if current trends hold, a drug discovery scientist starting their career today is likely to retire without ever having worked on a single drug that makes it to market.

The cost to discover and develop a drug today is orders of magnitude higher than in the 1950s. Despite this, the probability that a drug entering clinical trials will eventually reach the market has hardly improved in the intervening years. If Janssen were born today, there's little chance he would be able to repeat his success. He would probably not even get the chance to start.

What changed? Some lay the blame for these deteriorating conditions on regulators like the FDA, claiming that if we were to abolish regulators we would release the stranglehold on industry and unleash a deluge of stalled medicines. Others blame 'big pharma', claiming the industry is suppressing cures - more interested in price gouging on old drugs than investing in R&D. These explanations lack nuance. In reality, the productivity crisis in the pharmaceutical industry is the culmination of decades of just about every aspect of drug discovery and development getting gradually harder and more expensive.

So how did one man and his start-up manage to achieve a level of output that would be the envy of today's pharmaceutical giants?

The article starts out with the premise that it is an increased expense of discovery and development, resulting from structural shifts in the way these processes are conducted, that is the major factor in the problems facing the drug development industry. The author still includes a good, long view of issues on regulatory side of the house. I would argue that those issues are the major factor, both in direct and indirect ways: not just by directly imposing costs, but also by indirectly steering researchers and industry into poor, inefficient strategies. I encourage you to read the whole article.

Researchers here report that a small trial in humans showed that modulation of the aged gut microbiome via dietary supplementation with a prebiotic produced modest benefits to cognitive function. It is interesting that a prebiotic strategy, generally a weak form of intervention characterized by short duration of effect and small effect size, managed this outcome. There was no improvement in physical performance in the study group, only cognitive function. One might contrast this with what is known of the effects of fecal microbiota transplant from a young individual or flagellin immunization on the gut microbiome, meaning much larger and essentially permanent changes, and larger health benefits, at least going by the animal study data.

Studies suggest that inducing gut microbiota changes may alter both muscle physiology and cognitive behaviour. Gut microbiota may play a role in both anabolic resistance of older muscle, and cognition. In this placebo controlled double blinded randomised controlled trial of 36 twin pairs (72 individuals), aged ≥60, each twin pair are block randomised to receive either placebo or prebiotic daily for 12 weeks. Resistance exercise and branched chain amino acid (BCAA) supplementation is prescribed to all participants. Outcomes are physical function and cognition. The trial is carried out remotely using video visits, online questionnaires and cognitive testing, and posting of equipment and biological samples.

The prebiotic supplement is well tolerated and results in a changed gut microbiome, e.g. increased relative Bifidobacterium abundance. There is no significant difference between prebiotic and placebo for the primary outcome of chair rise time (β = 0.579). The prebiotic improves cognition (factor score versus placebo (β = -0.482). Our results demonstrate that cheap and readily available gut microbiome interventions may improve cognition in our ageing population. We illustrate the feasibility of remotely delivered trials for older people, which could reduce under-representation of older people in clinical trials.

Link: https://doi.org/10.1038/s41467-024-46116-y

Skin is a complex organ of many distinct layers, in which different cell types and structures interact to maintain function and ability to regenerate. Creating a skin-like structure is one thing, but introducing sweat glands, hair follicles, and other complex features is quite another. Still, the accessibility of skin and the frequency of serious injuries that remove large sections of skin makes the skin a good testbed for the development of improved bioprinting techniques that are capable of inserting complex small-scale structures, manufacturing the different layers of skin, and that can be used in situ, directly printing into the injured area. If complex features of skin can be assembled via 3D printing and proven in the clinic, then it is the hope that the techniques involved can be adapted for the regeneration of other organs.

"Reconstructive surgery to correct trauma to the face or head from injury or disease is usually imperfect, resulting in scarring or permanent hair loss. With this work, we demonstrate bioprinted, full thickness skin with the potential to grow hair in rats. That's a step closer to being able to achieve more natural-looking and aesthetically pleasing head and face reconstruction in humans." While scientists have previously 3D bioprinted thin layers of skin, this team is the first to intraoperatively print a full, living system of multiple skin layers, including the bottom-most layer or hypodermis. Intraoperatively refers to the ability to print the tissue during surgery, meaning the approach may be used to more immediately and seamlessly repair damaged skin. The top layer - the epidermis that serves as visible skin - forms with support from the middle layer on its own, so it doesn't require printing.

The hypodermis, made of connective tissue and fat, provides structure and support over the skull. "The hypodermis is directly involved in the process by which stem cells become fat. This process is critical to several vital processes, including wound-healing. It also has a role in hair follicle cycling, specifically in facilitating hair growth."

The researchers started with human adipose, or fat, tissue obtained from patients undergoing surgery. The team extracted the extracellular matrix - the network of molecules and proteins that provides structure and stability to the tissue - to make one component of the bioink. The team also obtained stem cells, which have the potential to mature into several different cell types if provided the correct environment, from the adipose tissue to make another bioink component. Each component was loaded into one of three compartments in the bioprinter. The third compartment was filled with a clotting solution that helps the other components properly bind onto the injured site. "The three compartments allow us to co-print the matrix-fibrinogen mixture along with the stem cells with precise control. We printed directly into the injury site with the target of forming the hypodermis, which helps with wound healing, hair follicle generation, temperature regulation, and more."

Link: https://www.psu.edu/news/research/story/3d-printed-skin-closes-wounds-and-contains-hair-follicle-precursors/

In the interview noted here, Aubrey de Grey of the Longevity Escape Velocity (LEV) Foundation makes a bold prediction of 12-15 years as to when we might see the advent of the first therapies capable of extending the healthy human life span by a few decades, allowing older people to live long enough to benefit from following improvements to further extend their healthy life spans. It is worth bearing in mind that the creation of novel therapies doesn't mean widespread use or even easy availability of those therapies. Further, it is unlikely that we'll know the effects on human life span of any given combination of novel rejuvenation therapies until at least ten to twenty years have passed, particularly if the therapies are not widely used.

As they say, it is hard to make predictions, particularly about the future. Is 12-15 years an unreasonable prediction? If we think that senolytics are going to be effective rejuvenation therapies in humans, and we believe that one or two of the other more advanced lines of work will be equally effective, then maybe this will pan out, subject to the caveats above. Those other lines of work might include partial epigenetic reprogramming, mitochondrial transplantation, telomerase gene therapies, that sort of thing. But expect surprises and delay! Biotech as a field tends to excel in the production of those two line items. We'll have to look back 30-40 years from now to see where the first rejuvenation therapies worthy of the name actually came into being.

One might think that there would be a rush to use any rejuvenation therapy with compelling data in mice and good safety data in humans, but that hasn't happened for the senolytic therapy of dasatinib and quercetin. Some unknown number of people are in fact using this therapy, given that numerous anti-aging clinical practices now offer it to their patients, but beyond that only a few slow-moving and small clinical trials have taken place. One might also consider the use of rapamycin as a point of comparison, where it is possible to find a few hundred self-experimenters to report on by asking for respondents, but there is no good human data on effects on life span, and nor is there likely to be in the near future. At the present pace of adoption another few decades could pass and we'll still not have access to good data that will tell us anything about effects of early therapies on late life mortality and life span.

Ambrosia Path Interview with Aubrey de Grey

Can you explain the concept of "longevity escape velocity" and its significance in the pursuit of extending human lifespan? When do you think we will reach longevity escape velocity?

LEV is defined as the minimum rate at which medicines need to be improved in order that people receiving the latest medicines can avoid age-related chronic conditions indefinitely. The reason why that rate is finite is that these medicines will be ones that reduce biological age, rather than just slowing the rate at which biological age rises - in other words, each incremental advance will buy time to develop the next one. LEV becomes initially achievable when we have medicines that postpone aging by around 20 years, and I currently think we have a 50% chance of reaching that point within about 12-15 years from now.

Do you see anything being commercially available for longevity/treating aging in the next 5-10 years?

Yes and no. Because aging is not one process but a bunch of only loosely communicating processes, we will address some parts of it sooner than others. So at this point, treatments for some of the easier parts are already in clinical trials and will very probably hit the streets in only a couple of years. But it will probably take a decade longer for enough of the parts of aging to be addressed that we see bona fide postponement of all chronic conditions of old age, which is what most people mean by treatments for aging.

Are there any developments (research, startups etc) that have excited you recently? Any potential up and coming therapies that you find interesting/think more people should know about?

Of course! The field is exploding right now. I'll just pick one: THIO, which is a new anti-cancer drug that kills cells which are making large amounts of telomerase, which means 90% of all human cancers and basically no non-cancer cells. It's in a phase 2 clinical trial being run by MAIA Biotechnology.

It is fair to say that the diversity of academia brings downsides in addition to upsides. A monolithic culture tends to mean slow progress: too little is explored at the borders of what is known when one viewpoint prevails at the expense of all others. A diverse culture produces such a variety of standards that it becomes challenging to compare any two studies. The paper-length complaint here is outlines the problems facing any scientist who is engaged in an analysis of published animal study data on the topic of intervening to slow or reverse aging, with a particular focus on the harms produced by a diversity of strategies for scientific controls in life span studies.

The search for interventions to slow down and even reverse aging is a burgeoning field. The literature cites hundreds of supposedly beneficial pharmacological and genetic interventions in model organisms: mice, rats, flies and worms, where research into physiology is routinely accompanied by lifespan data. However, when experimental animals from one article live as long as controls from another article, comparing the results of interventions across studies can yield misleading outcomes. Theoretically, all lifespan data are ripe for re-analysis: we could contrast the molecular targets and pathways across studies and help focus the further search for interventions. Alas, the results of most longevity studies are difficult to compare.

This is in part because there are no clear, universally accepted standards for conducting such experiments or even for reporting such data. The situation is worsened by the fact that the authors often do not describe experimental conditions completely. As a result, works on longevity make up a set of precedents, each of which might be interesting in its own right, yet incoherent and incomparable at least for the reason that in a general context, it may indicate, for example, not prolonging the life of an average organism, but compensating for any genetic abnormalities of a particular sample or inappropriate living conditions. Here we point out specific issues and propose solutions for quality control by checking both inter- and intra-study consistency of lifespan data.

Link: https://doi.org/10.18632/aging.205604

It is comparatively easy to find correlations in human epidemiological data, but much harder to determine causation. A web of correlations exist between socioeconomic status, education, intelligence, and life expectancy. We can even draw in environmental factors such as degree of exposure to particulate air pollution, which tends to correlate with the wealth of individuals living in a given area. In the matter of education, the effect size is small but the correlation is robust in large data sets. Why this is the case remains a topic for discussion.

To measure the pace of aging, the researchers applied an algorithm known as the DunedinPACE epigenetic clock to genomic data collected by the Framingham Heart Study. The latest findings showed that, according to the yardstick of the DunedinPACE epigenetic clock, two years of additional schooling translated to a 2-3% slower pace of aging. This slowing in the pace of aging corresponds to a roughly 10 percent reduction in risk of mortality in the Framingham Heart Study, according to previous research on the association of DunedinPACE with risk of death.

The researchers used data from 14,106 Framingham Heart Study spanning three generations to link children's educational attainment data with that of their parents. They then used data from a subset of participants who provided blood samples during data collection to calculate the pace of biological aging using the DunedinPACE epigenetic clock. In primary analysis, the researchers tested associations between educational mobility, aging, and mortality in a subset of 3,101 participants for whom educational mobility and pace of aging measures could be calculated. For 2,437 participants with a sibling, the researchers also tested whether differences in educational attainment between siblings were associated with a difference in the pace of aging.

"A key confounder in studies like these is that people with different levels of education tend to come from families with different educational backgrounds and different levels of other resources. To address these confounds, we focused on educational mobility, how much more (or less) education a person completed relative to their parents, and sibling differences in educational attainment - how much more (or less) education a person completed relative to their siblings. These study designs control for differences between families and allow us to isolate the effects of education."

By combining these study designs with the new DunedinPACE epigenetic clock, the researchers were able to test how education affects the pace of aging. Then, by linking the education and pace of aging data with longitudinal records of how long participants lived, the team was able to determine if a slower pace of aging accounted for increased longevity in people with more education. "We found that upward educational mobility was associated both with a slower pace of aging and decreased risk of death. In fact, up to half of the educational gradient in mortality we observed was explained by healthier aging trajectories among better-educated participants." This pattern of association was similar across generations and held within family sibling comparisons: siblings with higher educational mobility tended to have a slower pace of aging as compared with their less educated siblings.

Link: https://www.publichealth.columbia.edu/news/more-schooling-linked-slowed-aging-increased-longevity

Investors focused on funding biotechnology startups tend to exhibit herd behavior, much like investors everywhere these days. Funding is primarily deployed towards fads and popular trends, not necessarily towards what makes the most sense, even if sometimes the sensible manages to align with the popular. These days that means drug discovery platforms with a strong computational component and partial epigenetic reprogramming. But even in this environment, the path to true success is to work on important projects that few other people are touching. Be the champion for a potential solution to a tough, high-value, comparatively neglected problem.

Considering those tough, high-value problems, we can look at the world as it stands today and count how many people die from this age-related condition or that age-related condition. We could start at the top and work down: atherosclerosis, cancer, viral infection, dementia, kidney disease. All of these categories are vast, worldwide, with room for a sizable number of companies to all achieve significant success. For each of the categories of mortality mentioned above, there is room for many different therapies that address some part of the complex web of mechanisms of aging that lead to disease and death.

More First in Class Treatments for Atherosclerosis

The present state of therapy and development for the treatment of atherosclerosis is dismal. Industry and regulators are fixated on lowering LDL-cholesterol in the bloodstream, an approach that has demonstrably and comprehensively failed to reverse established atherosclerotic plaque, only slowing the progression of the condition modestly. The still-standard small molecule therapies, statins, have meaningful unpleasant, dose-limiting side-effects for a sizable fraction of patients. New development remains near entirely focused on novel ways of lowering LDL-cholesterol, none of which are shown to do any better than statins when it comes to the most important outcome, which is to say reversing the growth of atherosclerotic plaque. Outsider biotech startups like Cyclarity Therapeutics and Repair Biotechnologies cannot continue to be the only groups developing novel, different, ambitious therapies aimed at reversal of atherosclerosis. There is a vast gap in the market, an enormous unmet need in the 26% of humanity that is killed by stroke and heart attack, the direct consequences of unstable atherosclerotic plaques. This ongoing toll takes place in a world in which everyone who can use statins is using statins. We must do better.

More Attempts at a Universal Cancer Therapy

A good number of mechanisms involved in cancer are, if not completely universal to all cancer cells, at least common across a sizable fraction of all cancers. Far too little work is focused on influencing these mechanisms. Finding ways to interfere in alternative lengthening of telomeres (ALT), for example, continues to languish despite being an excellent target for small molecule development, given that ALT only operates in cancerous cells. As the rapid progress of Maia Biotechnology demonstrates, a broadly applicable cancer therapy (targeting telomere extension in their case) will quickly draw the attention of well-funded backers in an industry that has hobbled itself by focusing discovery on uncovering per-cancer and per-cancer-subtype mechanisms without broad application.

Far Better Antiviral Therapies

Present antiviral therapies are a mixed bag, all too few of which are truly effective. Herpesviruses and similar viral infections that persist over years and decades are implicated in the decline of the immune system and development of age-related diseases. The failing immune system also allows influenza and similar respiratory viruses to transiently infect and kill immense numbers of older people every year. There are too few approaches under development, such as the successor to the DRACO methology at Kimer Med, aimed at the production of improved antiviral therapies that are not just more effective for some viral infections, but can also target many different viruses with minimal alteration to the therapy itself.

Means to More Selectively Suppress Excessive Inflammation

The chronic inflammation of aging is highly disruptive to tissue function and drives the progression of many of the common fatal age-related conditions. This maladaptive, unresolved inflammatory response derives from a wide range of processes, everything from the persistent viral infections mentioned above through to a growing burden of senescent cells, bad behavior on the part of visceral fat cells, innate immune reactions to mitochondrial stress and mislocated mitochondrial DNA, and much more besides. So far, research into the biochemistry of inflammatory signaling suggests that both useful, short-term inflammatory reactions and harmful, excessive, unresolved inflammatory reactions run through the same signaling pathways. This is not a certain conclusion, however. If it is the case, then the only way to dampen the chronic inflammation of aging without also suppressing necessary immune function is to fix every dysfunction of aging. Are there short-cuts, however, ways to interfere in only the unwanted inflammatory signaling? Perhaps.

Infrastructure for Faster, Cheaper, Responsible Clinical Trials

There is a huge gap in the options available for clinical development of therapies. Moving forward within the established FDA or EMA system, requiring expensive GMP manufacturing processes and trial infrastructure is excessively costly and far too cautious for near all therapies entering this process. Options such as holding formal clinical trials outside the US, with Australia being a popular location, do not reduce the cost by anywhere near enough. Alternatively one can deploy therapies in clinics outside the US and offer services via medical tourism, suffering all of the consequences thereof, such as lack of public trust and low numbers of patients.

Where is the middle ground between these two points? Sadly, there is no established middle ground whereby responsible clinical trials can be conducted within a system with a good reputation, outside the FDA and EMA systems, making full use of the low cost options of sites such as Próspera in Honduras. Not all medical therapies need GMP manufacture for reasonable degrees of safety. Not all medical therapies need heavy-duty trial infrastructure to provide sufficient proof of safety and efficacy to convince physicians to use them. If we want faster progress, then the costs of medical development must be greatly reduced. Groups associated with the Próspera project are among the few presently attempting to build this middle ground - but there is a great deal of room for competition in the production of a low-cost, responsible, trusted alternative to the FDA and EMA.

Gero is one of a number of longevity industry biotech companies that put a strong focus on computational analysis of data to steer small molecule drug development and repurposing efforts. One of the interesting themes in their papers and presentations is the decomposition of signatures of aging into different distinct components, both in mice and in humans. When one can identify different overlapping trends in age-related changes in omics data, there is something to be said in that about the way in which aging progresses. The usual challenges apply, however, in that it is difficult to take this sort of analysis and link it back to fundamental mechanisms of aging. The research community as a whole struggles to identify concrete links between specific forms of molecular damage and consequential dysfunction on the one hand versus specific changes in biomarkers on the other. There is an enormous body of data, and data has become cheap to manufacture, but obtaining a deeper understanding of the meaning of that data remains a slow and expensive process.

Aging across most species, including mice and humans, is characterized by an exponential acceleration of mortality rates. In search for the molecular basis of this phenomenon, we analyzed DNA methylation (DNAm) changes in aging mice. Utilizing principal component analysis (PCA) on DNAm profiles, we identified a primary aging signature with an exponential age dependency, closely reflecting the Gompertz law's description of mortality acceleration.

This signature is the manifestation of the dynamic instability in the organism's state that drives the aging process in mice. It aligns closely with regression-based aging clocks and responds to interventions such as caloric restriction and parabiosis. Additionally, we identified a linear DNAm signature, indicative of a global demethylation level. Through single-cell DNAm (scDNAm) data from aging animals, we demonstrate that this signature captures the exponential expansion of the state space volume spanned by individual cells within an aging organism, and thus quantifying linearly increasing configuration entropy, likely an irreversible process. Consistent with this interpretation, we found that neither caloric restriction (CR) nor parabiosis significantly impacts the entropic feature, reinforcing its link to irreversible damage.

Link: https://doi.org/10.1101/2024.02.25.581928

Cells respond to the presence of DNA in the cytoplasm with inflammatory signaling, an evolved innate immune response that serves to protect against viral and bacterial infection. This becomes a problem when mitochondria become dysfunctional, as mitochondria contain their own small genome, the mitochondrial DNA. In the context of age-related mitochondrial dysfunction, and a number of other circumstances, fragments of mitochondrial DNA can find their way into the cell cytoplasm. The result is a link between mitochondrial dysfunction and the chronic inflammation of aging, though it remains unclear as to how much of this characteristic unresolved inflammatory signaling is the result of mislocated DNA versus, say, the presence of senescent cells, or other contributions. Is there something that can be done to block this unwanted inflammatory signaling, short of repairing or replacing dysfunctional mitochondria throughout the body? Perhaps, perhaps not, but further research is the only way to find out.

Mitochondrial DNA (mtDNA) encodes essential subunits of the oxidative phosphorylation system, but is also a major damage-associated molecular pattern (DAMP) that engages innate immune sensors when released into the cytoplasm, outside of cells or into circulation. As a DAMP, mtDNA not only contributes to anti-viral resistance, but also causes pathogenic inflammation in many disease contexts. Cells experiencing mtDNA stress caused by depletion of the mtDNA-packaging protein, mitochondrial transcription factor A (TFAM) or during herpes simplex virus-1 infection exhibit elongated mitochondria, enlargement of nucleoids (mtDNA-protein complexes) and activation of cGAS-STING innate immune signalling via mtDNA released into the cytoplasm. However, the relationship among aberrant mitochondria and nucleoid dynamics, mtDNA release, and cGAS-STING activation remains unclear.

Here we show that, under a variety of mtDNA replication stress conditions and during herpes simplex virus-1 infection, enlarged nucleoids that remain bound to TFAM exit mitochondria. Enlarged nucleoids arise from mtDNA experiencing replication stress, which causes nucleoid clustering via a block in mitochondrial fission at a stage when endoplasmic reticulum actin polymerization would normally commence, defining a fission checkpoint that ensures mtDNA has completed replication and is competent for segregation into daughter mitochondria. Chronic engagement of this checkpoint results in enlarged nucleoids trafficking into early and then late endosomes for disposal. Endosomal rupture during transit through this endosomal pathway ultimately causes mtDNA-mediated cGAS-STING activation. Thus, we propose that replication-incompetent nucleoids are selectively eliminated by an adaptive mitochondria-endosomal quality control pathway that is prone to innate immune system activation, which might represent a therapeutic target to prevent mtDNA-mediated inflammation during viral infection and other pathogenic states.

Link: https://doi.org/10.1038/s41556-023-01343-1

Glutathione is one of the more important cellular antioxidants. Delivery of glutathione via a range of mechanisms has been tested as a way to improve function in older individuals, with intriguing results in small clinical trials. The benefits include improved mitochondrial function and reduced inflammation. Delivery of antioxidants to mitochondria, where they can suppress the production of reactive oxygen species that takes place as a side-effect of the normal operation of these organelles, has been demonstrated to improve health and modestly slow aging in animal models. Unfortunately glutathione isn't orally bioavailable; one can't just take it as a supplement. Intravenous injection works, but the most interesting of the tested delivery methods are iontophoresis patches and daily supplementation with large amounts of the gluthathione precursors glycine and N-acetylcysteine.

In this context, one might take a look at today's open access paper. It is interesting to see the evidence presented for low glutathione levels to contribute to the development of Parkinson's disease. The most evident symptoms of the condition derive from cell death in the small but vital population of dopamine-generating neurons. These neurons are evidently more vulnerable to stresses, including oxidative stress deriving from mitochondrial dysfunction, than is the case for other cells in the brain. Glutathione is protective, and the less of it there is, the greater the risk of losing enough dopamine-generating neurons to tip over into the symptoms of Parkinson's disease.

Natural Variation in Age-Related Dopamine Neuron Degeneration is Glutathione-Dependent and Linked to Life Span

Aging is the biggest risk factor for Parkinson's disease (PD), suggesting that age-related changes in the brain promote dopamine neuron vulnerability. It is unclear, however, whether aging alone is sufficient to cause significant dopamine neuron loss and if so, how this intersects with PD-related neurodegeneration. Here, through examining a large collection of naturally varying Drosophila strains, we find a strong relationship between life span and age-related dopamine neuron loss. Strains with naturally short-lived animals exhibit a loss of dopamine neurons but not generalized neurodegeneration, while animals from long-lived strains retain dopamine neurons across age.

Metabolomic profiling reveals lower glutathione levels in short-lived strains which is associated with elevated levels of reactive oxygen species (ROS), sensitivity to oxidative stress and vulnerability to silencing the familial PD gene parkin. Strikingly, boosting neuronal glutathione levels via glutamate-cysteine ligase (Gcl) overexpression is sufficient to normalize ROS levels, extend life span, and block dopamine neurons loss in short-lived backgrounds, demonstrating that glutathione deficiencies are central to neurodegenerative phenotypes associated with short longevity.

These findings may be relevant to human PD pathogenesis, where glutathione depletion is reported to occur in idiopathic PD patient brain through unknown mechanisms. Building on this, we find reduced expression of the Gcl catalytic subunit in both Drosophila strains vulnerable to age-related dopamine neuron loss and in human brain from familial PD patients harboring the common LRRK2 G2019S mutation. Our study across Drosophila and human PD systems suggests that glutathione synthesis and levels play a conserved role in regulating age-related dopamine neuron health.

You might recall a number of epidemiological studies from the past fifteen years that examined correlations between time spent sitting and late life mortality. Some demonstrated that regardless of degree of physical activity sitting time still correlated with mortality - not the most intuitive of outcomes. As is the case for all such epidemiological questions of lifestyle and mortality, the general thrust of the data was disputed by a few large opposing studies. One in particular argued that the focus on sitting was misplaced, early studies misinterpreted their data, and that the focus should be on immobility. In support of that idea, accelerometer studies have consistently shown that low levels of activity, such as gentle walking, gardening, moving around in the house, are significantly better for long-term health than being entirely sedentary. Still, the debate on sitting continues, as shown here.

Sedentary behavior is a recognized mortality risk factor. The novel and validated convolutional neural network hip accelerometer posture algorithm highly accurately classifies sitting and postural changes compared with accelerometer count cut points. We examined the prospective associations of convolutional neural network hip accelerometer posture-classified total sitting time and mean sitting bout duration with all-cause and cardiovascular disease (CVD) death.

Women (n=5,856; 79±7 years old) in the Women's Health Initiative Objective Physical Activity and Cardiovascular Health (OPACH) Study wore the ActiGraph GT3X+ for ~7 days from May 2012 to April 2014 and were followed through February 19, 2022 for all-cause and CVD death. The convolutional neural network hip accelerometer posture algorithm classified total sitting time and mean sitting bout duration from GT3X+ output. Over a median follow-up of 8.4 years there were 1,733 deaths, 632 of which were from CVD. Adjusted Cox regression hazard ratios (HRs) comparing women in the highest total sitting time quartile (more than 696 minutes per day) to those in the lowest (less than 556 minutes per day) were 1.57 for all-cause death and 1.78 for CVD death. HRs comparing women in the longest mean sitting bout duration quartile (more than 15 minutes) to the shortest (less than 9.3 minutes) were 1.43 for all-cause death and 1.52 for CVD death. Apparent nonlinear associations for total sitting time suggested higher all-cause death and CVD death risk after ~660 to 700 minutes per day.

Higher total sitting time and longer mean sitting bout duration are associated with higher all-cause and CVD mortality risk among older women. These data support interventions aimed at reducing both total sitting time and interrupting prolonged sitting.

Link: https://doi.org/10.1161/JAHA.123.031156

Decreased S6K expression is one of the downstream consequences of treatment with the mTOR inhibitor rapamycin, and is essential for mTOR inhibition to extend life in mice and other laboratory species. It is thought that the slowing of aging resulting from mTOR inhibition largely works via improved operation of the complex cell maintenance processes of autophagy, wherein damaged proteins are flagged, wrapped in membranes, and conveyed to a lysosome for recycling. Researchers here investigate the role of S6K, and note that it appears to reduce the excessive inflammatory signaling characteristic of old age in addition to improving lysosomal function, and thus autophagy.

Although S6K is a key downstream effector of mTOR signaling and has been implicated in determination of lifespan in invertebrates and mammals, the molecular and cellular mechanisms are still elusive. Here we show that, in Drosophila, lowered activity of S6K in the fat body is essential for mTOR-dependent longevity, and that it regulates endolysosomal morphology, inflammaging, and immunosenescence in the aging fat body.

Modifying endosome formation, but not autophagy, affected inflammaging by degrading rPGRP-LC, suggesting a causal link between endolysosome and inflammaging. We identified Syx13 as a molecular link that regulates endosome formation, inflammaging, and lifespan downstream of TORC1-S6K signaling. We uncovered a considerable sexual dimorphism in fat body inflammaging, potentially explaining the different lifespan impacts of S6K observed in males and females. Furthermore, repression of the NF-κB-like IMD pathway in the fly fat body enhanced clearance of bacteria and extended lifespan.

Importantly, long-term treatment with rapamycin increased Stx12 levels in mouse liver, and alleviation of immune processes was a common denominator of TORC1-S6K inhibition in RNA and proteomics profiles from the liver of old rapamycin-treated and S6K1 knockout mice. Furthermore, Rapa lowered age-associated activation of noncanonical NF-κB pathway in mouse liver, indicating that the effects of TORC1-S6K-Stx12 on immunoaging may be evolutionarily conserved from flies to mice. In summary, our findings highlight an important role for the TORC1-S6K-Syx13 signaling axis in inflammaging, immunosenescence and longevity.

Link: https://doi.org/10.1038/s43587-024-00578-3

Research has shown that many forms of mild, transient stress result in lasting changes to cell behavior and modestly slowed aging in short-lived animal species. This is the case whether the stress involves heat, cold, or lack of nutrients. This is hormesis, that overall benefit can result from suffering mild stress and low levels of molecular damage. While researchers have identified improved activity of the cell maintenance processes of autophagy as an important mechanism in the beneficial response to mild stressors, it remains a work in progress to understand all of the details of the lasting hormetic response to transient stress.

In today's open access paper, researchers discover a novel way in which cells maintain a memory of their exposure to heat stress. The protein TSP-1 is a tetraspanin, and this type of protein is known to form arrangements known as webs in the cell membrane. When generated in response to heat stress these tetraspanin webs can be long-lasting, and thus provide the cell with a form of memory distinct from epigenetic marks or other changes affecting gene expression in the cell nucleus. In general, one might argue that complex structures that form in the cell membrane (such as lipid rafts) are understudied and poorly understood in comparison to the biochemistry of the cell nucleus.

Early-life stress triggers long-lasting organismal resilience and longevity via tetraspanin

Epidemiological and clinical studies in humans show that life stress of various forms can exert profound lasting impacts on mental and physical health outcomes and life spans. Milder physiological stresses, such as fasting with adequate nutrition or thermal stimuli via sauna exposure, are associated with long-lasting health benefits. Transient periods of stress can induce persistent changes in the endocrine response, epigenetic regulation of gene expression, and plasticity changes in various organs. However, the underlying molecular and cellular mechanisms by which transient early-life stress can produce memory-like physiological effects remain poorly understood.

The free-living nematode Caenorhabditis elegans has emerged as a tractable model system to study how early-life stress may affect adult phenotypes. Adults that have undergone the dauer stage preserve a memory of their early-life starvation experience, resulting in alterations in gene expression, extended life span, and decreased reproductive capacity. In addition, a 1-day shift from 20° to 25°C during early adulthood in C. elegans appears to improve stress resistance and extend life span through known stress-responding transcription factors: Forkhead box transcription factor (DAF-1), heat shock transcription factor (HSF-1), and hypoxia inducible transcription factor (HIF-1). It remains unclear how specific effectors of these transcription factors, or other epigenetic mechanisms independent of these factors, may elicit long-lasting impacts on adult stress resilience and longevity.

In this study, we use a robust thermal stress paradigm in C. elegans to uncover causal mechanisms by which transient stress may exert lasting impacts on organismal resilience and longevity. We show that transient heat exposure at 28°C during late larval development activates the gene tsp-1, which encodes a C. elegans homolog of the evolutionarily conserved tetraspanin protein family. Tetraspanin 1 (TSP-1) proteins form tetraspanin web-like structures and are essential for maintaining membrane permeability, barrier functions, and heat-induced organismal resilience and longevity. Initial induction of tsp-1 by heat requires the histone acetyltransferase CBP/p300 homolog (CPB-1); however, unexpectedly, this results in sustained up-regulation of TSP-1 protein without a corresponding increase in mRNA abundance.

Our data suggest that tsp-1 expression leads to TSP-1 protein multimerization and the formation of stable tetraspanin web structures, which persist even in the absence of initial stimuli and tsp-1 transcript up-regulation. This tetraspanin web-based stable protein structure formation represents an intriguing mechanism of cellular memory, distinct from previously known modes of epigenetic regulation primarily occurring in the nucleus, such as DNA and histone modifications.

It is well known that muscle function can be sustained into late life to a greater degree than most people manage. Much of what is presently considered by most people to be normal loss of strength and muscle mass with aging is the result of a combination of a lack of exercise combined with lifestyle choices, such as becoming overweight, that generate chronic inflammation. Researchers here illustrate the point in a study of gene expression changes that take place in muscle tissue with age and other factors. The researchers compared age versus exercise and inflammatory status. At least by looking at the number of changes, chronological age has less of an effect on gene expression in muscle tissue than is the case for exercise and inflammation.

Evaluation of the influence of primary and secondary aging on the manifestation of molecular and cellular hallmarks of aging is a challenging and currently unresolved issue. Our study represents the first demonstration of the distinct role of primary aging and chronic inflammation/physical inactivity - the most important drivers of secondary aging, in the regulation of transcriptomic and proteomic profiles in human skeletal muscle. To achieve this purpose, young healthy people (n = 15), young (n = 8) and older (n = 37) patients with knee/hip osteoarthritis, a model to study the effect of long-term inactivity and chronic inflammation on the vastus lateralis muscle, were included in the study.

It was revealed that widespread and substantial age-related changes in gene expression in older patients relative to young healthy people (~4000 genes regulating mitochondrial function, proteostasis, cell membrane, secretory and immune response) were related to the long-term physical inactivity and chronic inflammation rather than primary aging. Primary aging contributed mainly to the regulation of genes (~200) encoding nuclear proteins (regulators of DNA repair, RNA processing, and transcription), mitochondrial proteins (genes encoding respiratory enzymes, mitochondrial complex assembly factors, regulators of cristae formation and mitochondrial reactive oxygen species production), as well as regulators of proteostasis. It was found that proteins associated with aging were regulated mainly at the post-transcriptional level.

Link: https://doi.org/10.1111/acel.14098

In recent years, data has shown correlations between specific blood biomarkers and Alzheimer's disease pathology in the brain, such as the burden of misfolded, aggregated amyloid-β. This has led to the development of a variety of blood tests for Alzheimer's disease, intended to replace the presently onerous testing that requires either expensive imaging or invasive analysis of cerebrospinal fluid. Alzheimer's disease develops slowly over time, a long period of raised amyloid-β levels in the brain setting the stage for later dysfunction. Early testing for the risk of later Alzheimer's disease enabled attempts to slow or evade the condition, such as via lifestyle changes, use of antiviral therapies, or at worst undergoing immunotherapies to reduce the burden of amyloid-β in the brain.

Accurate and expeditious detection of Alzheimer's disease (AD) pathology continues to be a major hurdle in advancing AD-modifying clinical research. A robust screening process that can identify patients with a high probability to randomize into AD therapeutic research trials would greatly enhance the ability to conduct and reduce the time needed to complete clinical trials. AD is characterized by the accumulation of two protein aggregates in the brain: extracellular deposits of amyloid beta (Aβ)-containing plaques and intraneuronal aggregates of misfolded tau protein. Numerous AD clinical trials, particularly those targeting either Aβ or amyloid plaques have used amyloid PET scans and/or cerebrospinal fluid (CSF) measures as an inclusion criterion for enrollment. While amyloid PET tracers have been shown to be very accurate in detecting brain amyloid deposits, these scans are costly and impose a significant patient burden.

Blood-based measures that are associated with the presence of brain amyloid plaques have recently been developed. Additionally, there is substantial interest in blood-based biomarkers reflecting two other critical aspects of AD pathology: tau tangles and neurodegeneration. Several clinical studies have been conducted evaluating the ability of various blood-based biomarkers to identify AD. These studies have identified Aβ40, Aβ42, the Aβ42/Aβ40 ratio (Aβ42/Aβ40), tau, and several species of phosphorylated tau (p-tau) as good candidates.

The primary objective of the Bio-Hermes Study was to evaluate the ability of several promising blood-based and digital biomarkers to reflect the presence of brain amyloid in participants enrolled at clinical trial sites using recruitment procedures similar to those used in AD therapeutic drug studies. Participants in the Bio-Hermes Study had clinical characteristics similar to those enrolled in clinical trials of disease-modifying treatments and, because multiple biomarkers were obtained, the predictive value of biomarkers alone or in combination can be evaluated. Results indicate that Aβ42/Aβ40 ratio, p-tau181, and p-tau217 are good predictors of brain amyloid positivity in this clinical trial-ready population.

Link: https://doi.org/10.1002/alz.13722

Every cell contains hundreds of mitochondria, the descendants of ancient symbiotic bacteria now integrated into the cell. Mitochondria generate oxidative molecules as a consequence of the processes that generate the chemical energy store molecule adenosine triphosphate (ATP), used to power the cell. Those oxidative molecules cause damage, near all rapidly repaired. They also serve as signals, such as in the beneficial response to exercise. With aging, however, mitochondrial function becomes impaired and the degree of oxidative stress generated by the operation of mitochondria becomes harmful.

Researchers have in the past produced modestly extended life in short-lived model organisms by overexpression of natural mitochondrial antioxidants such as catalase or via use of engineered antioxidant molecules targeted to mitochondria like SkQ1. This approach of dampening excessive mitochondrial generation of oxidative molecules seems generally beneficial, but the effects on life span in mice are small in more recent, more rigorously conducted studies. Today's open access paper provides a further data point, in that the scientists involved demonstrate that catalase upregulation fails to reduce the burden of cellular senescence in old mice. As they point out, this somewhat complicates present thinking on the interactions between age-related mitochondrial dysfunction and burden of cellular senescence.

Mitochondria-Targeted Catalase Does Not Suppress Development of Cellular Senescence during Aging

The loss of mitochondrial function is a potentially important driver of aging and can limit the life and health span of mammals. One aspect of this loss is an increase in mitochondrial reactive oxygen species (ROS) as these organelles are a major site for ROS generation. Murine knockouts of antioxidant enzymes such as superoxide dismutases 1 and 2 (SOD1 and SOD2) and catalase (CAT) are short-lived, indicating that cellular antioxidant defenses are required for normal life and health spans. Furthermore, increasing antioxidant proteins or treatment with antioxidants can extend the life span of invertebrate models. Despite these data, the overexpression of most antioxidant enzymes does not extend the life span of mice, suggesting that antioxidant defenses in these animals are already sufficient for geroprotection under unstressed conditions.

A notable exception to this occurs in the case of a mitochondrially targeted catalase (mCAT) transgene. In this model, catalase-which converts hydrogen peroxide into O2 and water-specifically targets mitochondria, providing these organelles with an added layer of protection from a common source of ROS-mediated damage. These mice live 10-20% longer than wild-type (WT) mice and are protected from the age-related loss of mitochondrial function, but it remains unclear if mCAT can attenuate the development of other aspects of aging, such as cellular senescence.

Cellular senescence is a stress or damage response characterized by a proliferative growth arrest accompanied by the release of various cytokines, chemokines, growth factors, proteases, oxylipins, and other signaling molecules collectively known as the senescence-associated secretory phenotype (SASP). Senescent cells have been linked to a number of age-related diseases and can limit both life and health spans, as the elimination of these cells protects against the development of several age-related pathologies. Importantly, mitochondrial dysfunction and ROS can drive cellular senescence in culture, as well as in the skin and adipose tissue of mice.

We previously demonstrated that mitochondrial dysfunction can result in a senescent phenotype that lacks multiple proinflammatory features found in the SASP. This mitochondrial-dysfunction-associated senescence (MiDAS) occurs in response to alterations in the cytosolic NAD+/NADH ratio, regardless of ROS status, indicating that mitochondrial dysfunction may drive senescence independent of ROS production; however, other models suggest that mitochondrial ROS may drive nuclear DNA damage or downstream signaling events that result in senescence and the SASP. It is therefore unclear if reducing mitochondrial ROS is effective in reducing the burden of senescent cells or the SASP during natural aging.

Here, we show that transgenic mCAT has no effect on senescent phenotypes in cultured human fibroblasts. Furthermore, gonadal adipose tissue from aged WT and mCAT mice shows increases in many markers of senescence both at 17 and after 25 months, but mCAT has no discernable effect on these markers. Together, these data support a model in which mitochondrial ROS are not universally required for senescence or the SASP during natural aging.

Harmful calcification of structures in the cardiovascular system proceeds alongside the development of the fatty lesions of atherosclerosis. Both disease processes are accelerated by chronic inflammation, but derive from very different, distinct underlying mechanisms. There is presently little that can be done to reverse calcification effectively; EDTA chelation therapy is the best option on the table at present, but isn't well regarded in the medical community. Other treatments are more focused on slowing the progression of calcification, and can achieve that goal to some degree.

The primary cause of worldwide mortality and morbidity stems from complications in the cardiovascular system resulting from accelerated atherosclerosis and arterial stiffening. Frequently, both pathologies are associated with the pathological calcification of cardiovascular structures, present in areas such as cardiac valves or blood vessels (vascular calcification). The accumulation of hydroxyapatite, the predominant form of calcium phosphate crystals, is a distinctive feature of vascular calcification. This phenomenon is commonly observed as a result of aging and is also linked to various diseases such as diabetes, chronic kidney disease, and several genetic disorders.

A substantial body of evidence indicates that vascular calcification involves two primary processes: a passive process and an active process. The physicochemical process of hydroxyapatite formation and deposition (a passive process) is influenced significantly by hyperphosphatemia. However, the active synthesis of calcification inhibitors, including proteins and low-molecular-weight inhibitors such as pyrophosphate, is crucial. Excessive calcification occurs when there is a loss of function in enzymes and transporters responsible for extracellular pyrophosphate metabolism.

In clinical practice, it is crucial to assess phosphate and pyrophosphate homeostasis by evaluating both plasma phosphate and pyrophosphate levels. When elevated phosphate levels are detected in the blood, the initial therapeutic strategies to prevent vascular calcification should include the administration of phosphate binders to reduce circulating phosphate levels and address any dysregulated phosphate homeostasis if present. Furthermore, in cases of low pyrophosphate levels, therapeutic strategies should involve the administration of exogenous pyrophosphate and interventions to enhance the availability of endogenous pyrophosphate.

Link: https://doi.org/10.3390/biology13020111

Mendelian randomization is a strategy for using genetic variants associated with specific phenotypes and outcomes to produce data supportive of a causal relationship between phenotype to outcome. Here, researchers aim to find evidence that larger populations of specific microbial species in the gut microbiome can speed up or slow down the process of degenerative aging, as assessed by aging clocks derived from simple health measures. The relative sizes of the microbial populations making up the gut microbiome shift with age, and research to date has demonstrated that the overall effects of these changes are negative: more pro-inflammatory microbes, fewer microbes producing beneficial metabolites. There are proven ways to produce lasting rejuvenation of the aged gut microbe, resetting the balance of populations, such as via fecal microbiota transplant from a young individual, but these interventions are not yet widely used.

Increasing evidence suggests that gut microbiota play an important role in the aging process. The gut microbiome, the collection of microorganisms inhabiting the human gastrointestinal tract, emerged as a key player in regulating host physiology and health. The gut microbiota begin to colonize the body from birth and develop together with the individual, playing a role in different stages of an individual's life. Accumulating evidence indicates that alterations in the gut microbiota composition and function, collectively referred to as dysbiosis, are associated with age-related diseases and may contribute to the aging process.

Observational studies cannot infer causal relationships between exposure and outcomes, and randomized controlled trial (RCT) studies often require a lot of research funding and costs and are constrained by experimental design limitations. Mendelian randomization (MR) uses genetic variation as an instrumental variable to infer causal relationships between exposures and outcomes from non-experimental data. Using MR has identified causal relationships between gut microbiota and aging-related diseases such as cardiovascular diseases and neurodegenerative diseases. MR studies also found causal relationships between gut microbiota and longevity. However, no MR studies have yet demonstrated a causal relationship between gut microbiota and biological aging.

In this study, two-sample MR was used to analyze the causal relationship between gut microbiota and biological aging in order to explore whether specific gut microbiota accelerate or decelerate the biological aging process and to provide new insights into promoting healthy aging through the modulation of gut microbiota. Streptococcus (β = 0.16) was causally associated with Bioage acceleration. Eubacterium (β = 0.20), Sellimonas (β = 0.06), and Lachnospira (β = -0.18) were suggestive of causal associations with Bioage acceleration, with the latter being protective. Actinomyces (β = 0.26), Butyricimonas (β = 0.21), and Lachnospiraceae (β = 0.24,) were suggestive of causal associations with Phenoage acceleration.

In conclusion, this Mendelian randomization study found that Streptococcus was causally associated with Bioage acceleration. Further randomized controlled trials are needed to investigate its role in the aging process.

Link: https://doi.org/10.3390/microorganisms12020370

In today's open access paper, researchers report on the results of a small clinical trial of senolytic treatments to clear senescent cells in human patients. The treatment produced a short term increase in epigenetic age as measured via immune cells in a blood sample, not the hoped-for result. Bear in mind that one of the senolytic treatments used in this small study, dasatinib and quercetin, has been shown to clear senescent cells in at least some tissues in earlier human studies. Given the well-established role of lingering senescent cells in degenerative aging, at least in mice, why the treatment produced no lasting decrease in epigenetic age in this study is an interesting question.

Firstly, it is entirely possible that current epigenetic clocks are insensitive to the contribution of senescent cells to degenerative aging. Some clocks have demonstrated insensitivity to other factors in the past, such as physical fitness or chronic inflammation. The results may also reflect changes in immune cell population sizes and behaviors rather than anything more significant about aging; this is ever the challenge when looking at epigenetic age in blood samples. It is also possible that the limited data on whether established senolytic treatments clear senescent cells in humans as well as they do in mice is in error, and we'll have to wait for different therapies, those currently under development, to reach clinical trials in order to learn more.

Lastly, it is possible that many of the patients used in the study may not have been old enough to have sizable burdens of senescent cells. With an average age of ~60 and lowest age of 40-something in the study group, it is reasonably to think that something like half of the participants may not have exhibited a sizable burden of senescent cells. Research is never simple!

Exploring the effects of Dasatinib, Quercetin, and Fisetin on DNA methylation clocks: a longitudinal study on senolytic interventions

Given the potential role of senescence in aging, senolytic drugs have emerged as promising candidates for extending lifespan. Some initially identified senolytics were Dasatinib, Quercetin, and Fisetin. These molecules were drugs or natural products already used for other indications in humans, including anti-cancer therapies.

Dasatinib is a tyrosine kinase inhibitor approved by the FDA to treat myeloid leukemia. Quercetin is a flavonoid compound that induces apoptosis in senescent endothelial cells. Combined treatment with Dasatinib and Quercetin (DQ) has been demonstrated to decrease senescent cell burden in humans in multiple tissues; improve pulmonary and physical function along with survival in mice while lessening their age-dependent intervertebral disc degeneration; and reduce senescence and inflammatory markers in non-human primates. In human studies, patients with idiopathic pulmonary fibrosis, a senescence associated disease, improved 6-minute walk distance, walking speed, chair rise ability and short physical performance battery after 9 doses of oral DQ over 3 weeks.

Fisetin is another flavonoid compound that has gained recognition for its anti-proliferative, anti-inflammatory, and anti-metastatic properties. Fisetin has the potential to reduce senescence markers in multiple tissues in murine and human subjects. Administration of Fisetin to old mice restored tissue homeostasis, reduced age-related pathology, and extended median and maximum lifespan. Notably, a comparative study has highlighted Fisetin as the safest and most potent natural senolytic among the tested compounds.

This study aimed to assess the effects of Dasatinib and Quercetin (DQ) senolytic treatment on DNA methylation (DNAm), epigenetic age, and immune cell subsets. In a Phase I pilot study, 19 participants received DQ for 6 months, with DNAm measured at baseline, 3 months, and 6 months. The age range of these individuals that were considered in the first study analyses were between 43.0 and 86.6.

Significant increases in epigenetic age acceleration were observed in first-generation epigenetic clocks and mitotic clocks at 3 and 6 months, along with a notable decrease in telomere length. However, no significant differences were observed in second and third-generation clocks. Building upon these findings, a subsequent investigation evaluated the combination of DQ with Fisetin (DQF), a well-known antioxidant and antiaging senolytic molecule. After one year, 19 participants (including 10 from the initial study) received DQF for 6 months, with DNAm assessed at baseline and 6 months. Remarkably, the addition of Fisetin to the treatment resulted in non-significant increases in epigenetic age acceleration, suggesting a potential mitigating effect of Fisetin on the impact of DQ on epigenetic aging.

Furthermore, our analyses unveiled notable differences in immune cell proportions between the DQ and DQF treatment groups, providing a biological basis for the divergent patterns observed in the evolution of epigenetic clocks. These findings warrant further research to validate and comprehensively understand the implications of these combined interventions.

Researchers here use Mendelian randomization to attempt to better understand the relationship between sleep duration and later life mortality. As is well established, a short sleep duration correlates with raised mortality. The point of performing this sort of study of genetic variants and their relationship with specific outcomes is to try to tease out evidence for causation. Epidemiological studies can only provide correlations between sleep duration and increased mortality risk, but genetic studies can provide at least some support for the idea that short sleep duration actually causes a meaningful degree of that increased mortality risk, and isn't just a side-effect of some sort.

Poor sleep health is associated with a wide array of increased risk for cardiovascular, metabolic, and mental health problems as well as all-cause mortality in observational studies, suggesting potential links between sleep health and lifespan. However, it has yet to be determined whether sleep health is genetically or/and causally associated with lifespan.

In this study, we firstly studied the genome-wide genetic association between four sleep behaviors (short sleep duration, long sleep duration, insomnia, and sleep chronotype) and lifespan using GWAS summary statistics, and both sleep duration time and insomnia were negatively correlated with lifespan. Then, two-sample Mendelian randomization (MR) and multivariable MR analyses were applied to explore the causal effects between sleep behaviors and lifespan.

We found that genetically predicted short sleep duration was causally and negatively associated with lifespan in univariable and multivariable MR analyses, and this effect was partially mediated by coronary artery disease (CAD), type 2 diabetes (T2D), and depression. In contrast, we found that insomnia had no causal effects on lifespan. Our results further confirmed the negative effects of short sleep duration on lifespan and suggested that extension of sleep may benefit the physical health of individuals with sleep loss. Further attention should be given to such public health issues.

Link: https://doi.org/10.1038/s41398-024-02826-x

RNA Polymerase I (Pol I) is prominent in the regulatory systems managing the nutrient-driven tradeoff between growth and longevity. It is responsible for producing a sizable fraction of RNA, reading from gene sequences and assembling corresponding RNA molecules. As such, it is responsible for initiating some of the most energetically expensive processes in the cell, including translation of messenger RNA into proteins. Suppression of the production of proteins is a consequence of low calorie intake, an intervention known to slow aging, and researchers have shown that interfering in RNA synthesis can also extend life in short-lived species. Here, researchers dig further into the connection between Pol I activity and aging, showing that reduced Pol I activity extends life in nematode worms.

The insulin/insulin-like growth factor signaling (IIS) and the mechanistic target of rapamycin (mTOR) promote anabolic reactions upon nutrient availability, whereas in a fasted state the adenosine monophosphate-activated protein kinase (AMPK) and the sirtuin family of nicotinamide adenine dinucleotide (NAD+)-dependent protein deacetylases trigger catabolic processes. Shifting the balance from IIS and mTOR signaling towards AMPK and sirtuin activity by diverse interventions promotes longevity in short-lived species.

The IIS, mTOR, AMPK, and sirtuin pathways impinge on Pol I-mediated transcription of ribosomal RNA (rRNA) genes (rDNA) into pre-rRNA, a precursor transcript comprising the three largest rRNAs. Notably, Pol I activity accounts for the major part of cells' transcription and, together with pre-rRNA processing and synthesis of ribosomal proteins, consumes a large portion of the cellular biosynthetic and energetic capacity. Moreover, ribosome biogenesis is required for mRNA translation, placing pre-rRNA synthesis at the origin of the most energy-demanding cellular activities.

Two recent studies reported that perturbation of rRNA synthesis entails pro-longevity effects in C. elegans and D. melanogaster, either by inducing structural changes in the nucleolus, the organelle implicated in ribosome biogenesis, or by limiting protein synthesis, respectively. However, the interplay between metabolic costs of Pol I activity and aging has not been explored in these studies.

Here we use multi-omics and functional tests to show that curtailment of Pol I activity remodels the lipidome and preserves mitochondrial function to promote longevity in C. elegans. Reduced pre-rRNA synthesis improves energy homeostasis and metabolic plasticity also in human primary cells. Conversely, the enhancement of pre-rRNA synthesis boosts growth and neuromuscular performance of young nematodes at the cost of accelerated metabolic decline, mitochondrial stress, and premature aging. Moreover, restriction of Pol I activity extends lifespan more potently than direct repression of protein synthesis, and confers geroprotection even when initiated late in life, showcasing this intervention as an effective longevity and metabolic health treatment not limited by aging.

Link: https://doi.org/10.1038/s41467-024-46037-w

The vast majority of senescent cells are produced when somatic cells reach the Hayflick limit to cell division, their telomeres shortened to a point at which they either self-destruct or enter the senescent state. Damage due to mutation or cytotoxic compounds can also induce senescence, as can the regenerative processes following injury. Senescent cells cease replication, become larger, and change their behavior in many other ways. Senescent cells secrete a pro-growth, pro-inflammatory mix of signals, the senescence-associated secretory phenotype (SASP), that attracts the attention of immune cells capable of destroying senescent cells, but also encourages nearby cells to become senescent.

Throughout much of life, senescence serves as a way to remove damaged cells and suppress the risk of cancer, but this is only the case because these cells are promptly cleared as they arise. Unfortunately, the immune system becomes ever less capable with advancing age, and senescent cells accumulate as the pace of create outstrips the pace of destruction. When senescent cells are constantly present, the SASP turns from helpful to harmful. It induces chronic inflammation, disrupts tissue structure and function, and contributes meaningfully to the onset and progression of all of the common age-related conditions. One of those conditions is osteoporosis, the age-related loss of bone density and the subject of today's open access paper.

Recent advances in senescence-associated secretory phenotype and osteoporosis

Although aging is an uncontrollable process, it is possible to mitigate age-related disorders by modifying the fundamental aging mechanisms. Cellular senescence is one of the mechanisms that can manifest in various biological processes via senescence-associated secretory phenotypes, SASPs. SASPs contribute to releasing cytokines and chemokines that promote local and systemic inflammatory responses, immune system activation, tissue damage, fibrosis, apoptosis, and malfunction. In addition, SASP can cause amplification of localized and systemic senescence via paracrine or endocrine pathways.

Osteoporosis (OP) has emerged as a significant health risk for individuals aged 50 and beyond. As the population ages, there are more instances of osteoporosis and fragility fractures, which puts an increasing strain on the health system. Osteoporosis formation and occurrence in aging are associated with deficient hormone levels, imbalanced bone remodeling, and a restricted number of osteoblasts, osteocytes, and their progenitor cells. Connecting the dots directly to osteoporosis, it is clear that the build-up of senescent cells (SCs) and the overexpression of SASPs in the bone microenvironment are closely linked to the etiology of this illness. In addition, senescent cells have also been shown to be present in the setting of radiotherapy-induced bone loss, and bone biopsy samples from elderly postmenopausal women. Current studies have found that targeting senescent bone cells in the bone and modulating SASP activity can promote bone remodeling and alleviate the symptoms of OP.

Many studies indicate that anti-senescence therapy drugs may have a role in treating osteoporosis associated with aging, radiation, diabetes, estrogen shortage. Nowadays, essential senescence treatment drugs can be categorized into two groups. One is the senolytic approach, which eliminates senescent cells by targeting the apoptotic pathway of senescent cells. The other one is senomorphic technique that targets SASP without influencing cell death. Senolytic medicines such as Dasatinib (D), quercetin (Q), D + Q, Navitoclax (ABT263), BCL-XL inhibitor, HSP90 inhibitor, and ABT-737 are utilized in animal studies to decrease the number of senescent bone marrow stromal cells and preosteoblasts and to increase the osteogenic capacity. Neutralizing antibodies can also inhibit senescence by targeting specific SASP components, such as TNF-α, TGF-β, IL-1β, IL-6, and IL-8. These drugs effectively ameliorate bone loss in inflammation-related diseases. Unfortunately, the efficiency of these anti-SASP agents in clinical OP is obscure.

Researchers here report on an assessment of epigenetic clocks (and PhenoAge). The study is one of a fair number of attempts to quantify just how effective these aging clocks are when it comes to predicting age-related disease and death. The interesting conclusion here is that epigenetic age acceleration, as determined using the present leading epigenetic clocks, isn't yet a meaningful improvement over the established, traditional, very low-tech correlations with age-related disease and death, such as socioeconomic status. This suggests that we should expect some years of further evolution of aging clocks of various forms before they become truly useful. That evolution will certainly take place: clocks are not going away, are a popular area of research and development, and significant effort is being devoted to their improvement.

Biomarkers developed from DNA methylation (DNAm) data are of growing interest as predictors of health outcomes and mortality in older populations. However, it is unknown how epigenetic aging fits within the context of known socioeconomic and behavioral associations with aging-related health outcomes in a large, population-based, and diverse sample. This study uses data from 3,581 Health and Retirement Study (HRS) participants to examine the relationship between DNAm-based age acceleration measures in the prediction of cross-sectional and longitudinal health outcomes and mortality.

We examine whether recent improvements to these scores, using principal component (PC)-based measures designed to remove some of the technical noise and unreliability in measurement, improve the predictive capability of these measures. We also examine how well DNAm-based measures perform against well-known predictors of health outcomes such as demographics, socioeconomic status (SES), and health behaviors.

In our sample, age acceleration calculated using "second and third generation clocks," PhenoAge, GrimAge, and DunedinPACE, is consistently a significant predictor of health outcomes including cross-sectional cognitive dysfunction, functional limitations and chronic conditions assessed 2 years after DNAm measurement, and 4-year mortality. PC-based epigenetic age acceleration measures do not significantly change the relationship of DNAm-based age acceleration measures to health outcomes or mortality compared to earlier versions of these measures. While the usefulness of DNAm-based age acceleration as a predictor of later life health outcomes is quite clear, other factors such as demographics, SES, mental health, and health behaviors remain equally, if not more robust, predictors of later life outcomes.

Link: https://doi.org/10.1073/pnas.2215840120

Lifestyle choices related to physical fitness have an impact on many aspects of degenerative aging. As noted here, the pace at which atherosclerosis develops is one of these aspects. Atherosclerosis is the buildup of fatty deposits in blood vessel wall tissue. Those deposits grow into atheromas that ultimately rupture to produce stroke and heart attack. It is the largest single cause of human mortality. Atherosclerosis is a dysfunction of cholesterol transport and the innate immune cells known as macrophages that are responsible for clearing excess cholesterol from blood vessel walls. Over a full lifetime of exposure, lifestyle choice that affect level of inflammation, immune function, and amount of cholesterol in the bloodstream can adjust the risk of later atherosclerosis. Choosing to maintain physical fitness is influential when maintained over decades.

It is well-known that being physically unfit at a young age is linked to an increased risk of cardiovascular disease much later in life. In the study, the researchers linked information from the Swedish Military Conscription Register to SCAPIS (the Swedish Cardiopulmonary Bioimage Study), a large population study on heart and lung health in individuals aged 50 to 64 years. For almost 9,000 men who participated in SCAPIS, data on them at conscription at age 18 from 1972 to 1987 were also available. One of the strengths of the study is that it is based on the general population and that the men have been followed for a long time, an average of 38 years.

The researchers examined the coronary arteries, which supply blood to the heart muscle, using coronary CT angiography, CCTA. The study is the first to use this state-of-the-art technology to examine plaques in the coronary arteries in relation to physical fitness at a young age. In addition, the researchers studied two different types of plaques in the coronary arteries. Plaques with calcium deposits are easy to measure and have long been the focus. "We see in our study that both good cardiorespiratory fitness and good muscle strength in youth are associated with a lower risk of atherosclerosis in the coronary arteries almost 40 years later."

Link: https://liu.se/en/news-item/fysisk-form-i-tonaren-och-mindre-aderforfettning