Fight Aging!

Fight Aging! publishes news and commentary relevant to the goal of ending all age-related disease, to be achieved by bringing the mechanisms of aging under the control of modern medicine. This weekly newsletter is sent to thousands of interested subscribers. To subscribe or unsubscribe from the newsletter, please visit: https://www.fightaging.org/newsletter/

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Contents

• An Example of In Silico Drug Screening for Senolytic Compounds
• Evidence For Autophagy to be Important to Microglial Dysfunction in the Aged Brain
• Towards Small Molecules that Induce Expression of Reprogramming Factor OCT4
• The Promise of Regenerative Medicine
• Looking Back at the Growth and Maturation of the Field of Aging Research
• Aptamer to Enhance Vitamin C Antioxidant Function Improves Neurovascular Function in Aged Mice
• SENS Research Foundation's Senotherapeutic Screening Project is Now Crowdfunding at Experiment
• Reviewing a Role for the Gut Microbiome in Degenerative Aging
• Pathogenic Tau Drives Cellular Senescence in the Aging Brain
• The Gut Microbiome Differs in Characteristic Ways in Patients with Precancerous Colon Polyps
• Investigating the Gut Microbiome of Centenarians
• Alzheimer's Disease as a Consequence of Vascular Endothelial Dysfunction
• Chronic Inflammation in Age-Related Anemia
• Senescent Cells Appear Involved in Graft-Versus-Host Disease
• Intermittent Senolytic Treatment with Dasatinib and Quercetin Produces Benefits in Non-Human Primates

An Example of In Silico Drug Screening for Senolytic Compounds
https://www.fightaging.org/archives/2023/06/an-example-of-in-silico-drug-screening-for-senolytic-compounds/

The average small molecule drug development program starts with a mechanism, an intended outcome such as inhibition, and then screening of as many molecules as possible from the libraries. Sometimes it is possible to make educated guesses as to what types of molecule are more likely to be useful, but often screening must be very broad and with little direction. In principle, low cost computation makes it possible to dramatically reduce the cost of discovery of useful molecules given a specific target mechanism. This shift from physical to in silico screening has been underway for a while, for example at Insilico Medicine, but is still a work in progress.

Small molecule medicine has its limitations, and in the future it seems likely that much of its present portfolio will be overtaken by gene therapies that can act precisely on target mechanisms: greater efficacy, far fewer side-effects, no expensive initial screening needed. Extending the life span of small molecule development into that era will require a dramatic reduction in its costs. At the end of the day the whole industry revolves around how much time and effort is needed to produce the prospect of a given benefit to patients.

The materials here are an example of the present state of the art when it comes to the use of in silico initial screening of small molecules. It needs something like the senolytics field to spur the development of better infrastructure for small molecule development. Small molecules can work well here, as demonstrated by animal data for dasatinib and quercetin, among others; there are many clear mechanistic targets for the clearance of senescent cells; there is a very large market, meaning the entire elderly population impacted by the burden of senescent cells in aged tissues; and the field is still young enough for an end to end development program to run for years and nonetheless find sizable profit at the end of it, if successful.

Artificial intelligence identifies anti-aging drug candidates targeting 'zombie' cells

Senolytics are compounds that selectively induce apoptosis, or programmed cell death, in senescent cells that are no longer dividing. A hallmark of aging, senescent cells have been implicated in a broad spectrum of age-related diseases and conditions including cancer, diabetes, cardiovascular disease, and Alzheimer's disease. In their new study, researchers trained deep neural networks on experimentally generated data to predict the senolytic activity of any molecule. Using this model, they discovered three highly selective and potent senolytic compounds from a chemical space of over 800,000 molecules.

All three displayed chemical properties suggestive of high oral bioavailability and were found to have favorable toxicity profiles in hemolysis and genotoxicity tests. Structural and biochemical analyses indicate that all three compounds bind Bcl-2, a protein that regulates apoptosis and is also a chemotherapy target. Experiments testing one of the compounds in 80-week-old mice, roughly corresponding to 80-year-old humans, found that it cleared senescent cells and reduced expression of senescence-associated genes in the kidneys.

Discovering small-molecule senolytics with deep neural networks

The accumulation of senescent cells is associated with aging, inflammation, and cellular dysfunction. Senolytic drugs can alleviate age-related comorbidities by selectively killing senescent cells. Here we screened 2,352 compounds for senolytic activity in a model of etoposide-induced senescence and trained graph neural networks to predict the senolytic activities of more than 800,000 molecules.

Our approach enriched for structurally diverse compounds with senolytic activity; of these, three drug-like compounds selectively target senescent cells across different senescence models, with more favorable medicinal chemistry properties than, and selectivity comparable to, those of a known senolytic, ABT-737. Molecular docking simulations of compound binding to several senolytic protein targets, combined with time-resolved fluorescence energy transfer experiments, indicate that these compounds act in part by inhibiting Bcl-2, a regulator of cellular apoptosis. We tested one compound, BRD-K56819078, in aged mice and found that it significantly decreased senescent cell burden and mRNA expression of senescence-associated genes in the kidneys. Our findings underscore the promise of leveraging deep learning to discover senotherapeutics.

Evidence For Autophagy to be Important to Microglial Dysfunction in the Aged Brain
https://www.fightaging.org/archives/2023/06/evidence-for-autophagy-to-be-important-to-microglial-dysfunction-in-the-aged-brain/

A number of lines of evidence implicate senescent microglia in the development of neurodegenerative conditions. Microglia are innate immune cells of the central nervous system, analogous to macrophages elsewhere in the body. Microglia appear to become more inflammatory with age, but this isn't just an amplification of inflammatory signaling that arises due to age-related dysfunctions such as mislocalization of mitochondrial DNA. Some microglia become senescent, and like other types of senescent cell, they energetically produce inflammatory signaling. Clearing such cells from the brain has produced benefits in animal models of neurodegeneration, but it remains to be seen as to whether that works well in humans.

The materials here summarize the work of researchers who suggest that failing autophagy is an important cause of microglial senescence in the aging brain. Autophagy is a collection of cell maintenance processes responsible for recycling damaged and worn proteins and cell components, sending them to a lysosome for disassembly by enzymes. It is well known that autophagy falters with advancing age, though a full accounting of why this is the case remains to be established. Inefficient autophagy leads to a greater burden of dysfunction in a cell, and, in principle, more cells tipped over the edge into a state of senescence.

The one caution here is that researchers essentially disabled autophagy rather than dialing it back to a lesser degree of efficiency. This produces a more obvious result, more easily measured, but the outright breakage of major mechanisms in a cell can lead to outcomes that are not reflective of what takes place inside the body as a result of a mere decline in efficiency. Still, one can look at this work in the context of other avenues of research that also implicate microglia and autophagy in the onset of neurodegeneration.

When Autophagy Stops, Microglia Sour into Senescence

When deprived of their ability to dispose of detritus via autophagy, microglia become annoyed, transitioning into a senescent, dysfunctional state. That was the upshot of a recent study in which researchers used conditional knockout mice to disable the "self-eating" pathway in microglia. Some of the cells shut down their cell cycle and revved up secretion of cytokines - behavior typical of senescent cells. In amyloid-laden mice, these autophagy-deficient microglia refused to transition into a bona fide disease-associated microglia (DAM) state, failing to properly contain plaques or to protect nearby synapses from shriveling. The findings further raise the profile of microglial autophagy as an essential part of the brain's response to proteopathic insults.

Neurons suffer dramatic impairments in autophagy both in the Alzheimer's disease (AD) brain and in mouse models of amyloidosis. While neurons need autophagy to clean up their own waste, microglia need this pathway for an additional purpose, that is, to help them mop up protein aggregates and detritus spewed by sickly neurons. Recent studies have cast microglial autophagy - a bioenergetically demanding process - as quelling amyloid-β (Aβ) plaques, tau pathology, and neuroinflammation.

Researchers conditionally deleted, from wild-type mice, the Atg7 gene, which encodes a protein critical for autophagosome biogenesis, only from microglia. They knocked out Atg7 in 2-month-old mice, then examined their brains six months later. Using single-cell transcriptomics, the scientists detected eight gene-expression clusters of microglia in wild-type and Atg7-cKO mice. Zeroing in on one that was far more abundant in the conditional knockouts, they found a cadre of microglia that appeared to have transitioned into a senescent state.

In 5xFAD AD model mice given these conditional Atg7 knockouts, microglia also did not assume a DAM state, opting instead for a senescence-associated profile. "SAMs" expressing S100a4, a marker of this senescent profile, appeared disinterested in amyloid. As a result, Aβ sprawled into diffuse plaques, which were surrounded by hyperphosphorylated tau and dystrophic neurites. This suggests that, without autophagy available to them, microglia became recalcitrant and no longer contained Aβ plaque formation, allowing the aggregates to become more of a hazard to nearby neurons.

Finally, the researchers treated the double-transgenic mice with dasatinib and quercetin, a combination therapy with proposed senolytic effects. The treatment reduced the number of microglia that were clogged with a backlog of autophagy substrates and expressed senescence markers. The findings place autophagy upstream of the microglial transition to a beneficial, disease-associated state, the authors proposed. Considering reports that autophagy declines with age while senescent cells become more numerous, the authors blame this combination for the dearth of DAM-like cells detected in human AD brains.

Towards Small Molecules that Induce Expression of Reprogramming Factor OCT4
https://www.fightaging.org/archives/2023/06/towards-small-molecules-that-induce-expression-of-reprogramming-factor-oct4/

Reprogramming involves inducing expression of reprogramming factors, canonically OSKM (OCT4, SOX2, KLF4, and MYC), the Yamanaka factors. When expressed for a sufficiently long time, a period of days to weeks, some fraction of OSKM-expressing cells dedifferentiate into induced pluripotent stem cells (iPSCs). Before that happens, however, beneficial epigenetic changes occur, resetting a cell to a more youthful pattern of gene expression, resulting in improvements such as restored mitophagy and mitochondrial function. The present focus of the industry is to find a way to safely apply transient exposure to reprogramming factors as a therapy, producing epigenetic rejuvenation without dedifferentiation. Initial results in animal models are promising, but a great deal of work yet lies ahead.

Because the bulk of medical research and development is focused on small molecule development rather than gene therapy, the excitement surrounding therapeutic reprogramming as a whole translates to a strong interest in finding ways to use small molecules to induce reprogramming factor expression. This idea that reprogramming can be applied directly as a therapy, rather than being a way to produce iPSCs for regenerative medicine, is still in the comparatively early stages, however. There is a great deal of funding, and new information is arriving at a fast pace, but it still takes time to make meaningful progress.

Development of a next-generation endogenous OCT4 inducer and its anti-aging effect in vivo

Octamer-binding transcription factor 4 (OCT4) is a member of the POU transcription factor family and functions as one of the master regulators in initiating reprogramming and maintaining pluripotency. Independent groups have observed rejuvenation in partially reprogrammed mice, characterized by the reversal of aging marks and improved tissue regeneration. Consequently, chemicals capable of (partially) activating endogenous reprogramming-associated transcription factors hold promise as potential candidates in anti-aging therapy.

Several studies have reported small molecule inducers of endogenous OCT4, including forskolin (a cAMP agonist), and pyrrolo[2,3-b]pyridine based OCT-activating compound 1 (OAC1). However, to date, a small molecule capable of completely replacing or reactivating OCT4 or its analogues in the reprogramming of somatic cells, has not yet been reported.

Recently, we conducted high-throughput screening and identified a series of compounds called OCT4-inducing compounds (O4Is). These compounds have the ability to sustain the maintenance of human iPSCs by promoting the expression of endogenous OCT4, including 4-(benzyloxy)phenyl derivatives (O4I1s), 2-aminothiazoles (O4I2s) and imidazopyrimidines (O4I3s).

In this work, analysis of cellular metabolic products revealed that hydrolysis, especially in pluripotent cells, ablated the activity of O4I2-ester derivatives, which led us to design a second generation of O4I2 derivatives with improved metabolic stability, including a compound called O4I4. By combining O4I4 with the ectopic expression of SOX2, KLF4, L-MYC and LIN28 (collectively designated as "CSKML"), we successfully reprogrammed human fibroblasts into iPSCs. In C. elegans and Drosophila O4I4 extended their lifespans, suggesting the potential application of O4I4 and other reprogramming-associated chemicals in regenerative medicine and anti-aging therapy.

The Promise of Regenerative Medicine
https://www.fightaging.org/archives/2023/06/the-promise-of-regenerative-medicine/

Is is now going on three decades since the first flush of excitement for regenerative medicine in the form of stem cell therapies. Unfortunately, producing meaningful, reliable regeneration with cell therapies turned out to be a great deal harder then hoped. It is still not a solved problem, outside a few narrow applications. In the intervening time, the field of regenerative medicine has expanded considerably beyond cell therapies, now of many varieties, to encompass approaches such as immune modulation and reprogramming native cell behavior. As today's commentary notes, there is still no magic button to turn on regeneration, but progress continues on what turned out to be a far harder challenge than first thought.

Emerging frontiers in regenerative medicine

Nearly every human malady, be it injury, infection, chronic disease, or degenerative disease, damages tissues. Moreover, 45% of all deaths can be traced to inflammation- and fibrosis-related regenerative failures. Restoring health after damage requires the answer to a key question: How can human tissues be coaxed to regenerate? Identifying instructive cues that direct refractory tissues down a regenerative path remains a critical yet elusive goal. Nonetheless, approaches to target roadblocks that impede regeneration, including insufficient and/or functionally inadequate progenitor cells, fibrosis, and chronic inflammation, are continuing to progress from bench to bedside. Pivotal advances have been made to overcome these hurdles using cell therapy, in vivo reprogramming, synthetic biology, and antifibrotic and anti-inflammatory therapies, but many challenges remain and knowledge gaps must be addressed to make regeneration a mainstay of modern medicine

The most conspicuous requirement for regenerative therapies is to replace the components of tissues that were lost or compromised by disease. Invigorating endogenous stem cells is an appealing strategy, but, to date, the greatest benefits have emerged from cell therapies. Adult stem cell-based regenerative therapies have shown clinical benefit to treat hematological malignancies, burn wounds, and ocular degeneration. Human pluripotent stem cell (hPSC)-based therapies have also shown promise and have entered clinical trials in the United States for type 1 diabetes, Parkinson's disease, and age-related macular degeneration. These three diseases are particularly amenable to stem cell-based therapies because they are associated with deficiency of a defined cell type.

Despite these early glimpses of success, cell therapies are hampered by many biological and technical hurdles. Autologous hPSC-based therapies derived from induced pluripotent stem cells (iPSCs) avoid immune aggravation, but this cost- and labor-intensive strategy requires safety testing for each use. A major concern with nonautologous cell therapy is immune rejection of the graft. Thus, "off-the-shelf" allogeneic therapies must be coupled to strategies that allow them to avoid rejection. Producing sufficient numbers of cells for engraftment has been successful in the skin but poses a major challenge for regenerating tissue in other organs, particularly if only a small proportion of cells survive after transplant.

An alternative approach to overcome the challenge of directing and integrating grafts in hard-to-reach internal organs is to repurpose cells that are present at the damage site by reprogramming them in situ with specific transcription factors. Reprogramming has been a particularly attractive strategy for the adult heart, which, unlike the embryonic heart, lacks bona fide progenitors. A subset of in vivo cellular reprogramming efforts are aimed at converting fibroblasts into cardiomyocytes to maintain cardiac function. Alternatively, transient expression of pluripotent transcription factors in adult cardiomyocytes induced proliferation, resulting in improved outcomes in adult mice after myocardial infarction.

In addition to replacing lost tissue with cell therapies and in vivo reprogramming, many injurious and complex disease states evoke inflammatory responses that must also be suppressed (see the figure). The state of the recipient tissue, often diseased, remains a challenging facet of applying cell therapies. New approaches to modulate inflammation include engineering stem cells with bioresponsive gene circuits that can sense inflammatory factors such as cytokines or reactive oxygen species and, in turn, induce the production of anti-inflammatory factors, allowing endogenous progenitors or transplanted cells to repair damage.

What was once considered the future of medicine is now becoming reality. But there is no magic pill for regeneration (yet). In addition to scientific and technological innovation, there are also practical considerations of cost and production. Achieving regeneration in humans will require a rapid transition from rodent models to clinically relevant large animal and human studies. Ascending the summit of human regeneration demands an interdisciplinary effort that brings together biologists, biomedical engineers, and clinicians. The view from the top will reveal a transformed medical landscape that is able to seamlessly rejuvenate organs, ultimately extending human life span and health span.

Looking Back at the Growth and Maturation of the Field of Aging Research
https://www.fightaging.org/archives/2023/06/looking-back-at-the-growth-and-maturation-of-the-field-of-aging-research/

A great deal has changed in these last few decades in the field of aging research. From the 60s onward to the 90s, aging research was increasingly characterized by a philosophy of "look but don't touch", an effort to distance academia from the growing anti-aging industry and its hype. It made itself a backwater science in which talk of intervention was aggressively discouraged by leaders in the field. Starting in the 90s, with studies showing significant life extension in lower animals following single gene mutations, it became impossible to ignore the potential to treat aging as a medical condition in humans.

Nonetheless, change comes only slowly in the scientific community. It was still a battle following the turn of the century to dismantle the old scientific culture and replace it with one in which researchers and funding institutions were enthusiastic about intervention in aging. That required a great deal of advocacy and philanthropic funding, accompanied by incremental advances in the science, a matter of bootstrapping progress. Ultimately it worked, of course, and now the research community is openly focused on producing therapies to slow and reverse aging, targeting the underlying mechanisms of aging. An industry has arisen, applying a great deal more funding to the challenge than is available to academia, and a wave of clinical trials will take place over the next five years.

Aging research: A field grows up

When I joined the longevity field, there had already been a shift from simply observing animals as they age to instead identifying regulators that could greatly alter lifespan, thanks to pioneering invertebrate genetic studies in the 1990s and early 2000s that discovered most well-conserved longevity pathways, particularly caloric restriction and the insulin/IGF-1 and TOR signaling pathways. What has changed in the past two decades? There have been at least three major shifts the aging/longevity research that will shape the field in the years to come.

The first shift is in the perspective of regulation: the concept that aging is indeed regulated, and not simply the result of accumulated damage. Once the regulators of longevity were found, there was still a general notion that these pathways primarily determine levels of cell autonomous damage repair. As molecular regulators of longevity and their networks have been identified, it has become clear that non-cell autonomous signaling coordinates rates of aging and response to damage across cells and tissues. In the future, the acknowledgment that these signals are integrated and can affect the body systemically will shape the types of therapeutics we develop, focusing on whole-body versus tissue-specific approaches, depending on the problem being solved.

A second large shift is in the aims of the field, from lifespan to healthspan. While maximum lifespan is still often the focus of the popular press, there is growing recognition that treating aging and age-related diseases are not mutually exclusive goals. Therefore, better understanding of how metabolic disorders, frailty, cardiovascular diseases, cognitive decline, reproductive aging, and other age-related changes are regulated might not only yield treatments for those disorders, but might ultimately increase lifespan as well. Maintaining functions with age may not only have a great impact on quality of life, but also may help us find treatments that generally slow aging.

A third shift is the translational focus of the longevity field, from an almost entirely academic endeavor to one that is being taken up by industry and clinics - that is, the findings we have made in academic labs are on the verge of becoming actual aging treatments. In the most immediate future, large-scale clinical trials of some of the best-studied longevity drugs (e.g., rapamycin and metformin) and testing of dietary interventions and mimetics may lead to aging treatments. New biotech companies have sprung up with a wide range of goals, from repurposing already-approved drugs for new aging treatments and exploring how the pathways we have discovered over the past 20 years might be harnessed to treat aging, to high-throughput and AI-driven approaches to search for new candidate aging drugs. Circulating blood factors first identified in parabiosis experiments, drugs that target senescent cells, and cell reprogramming and regeneration approaches have moved from concepts to testing, while molecular clocks are beginning to be used as diagnostics.

Luckily, we have finally matured beyond asking whether it is right to study aging, as it is being increasingly recognized that efforts to slow aging will be broadly beneficial; in fact, some of those approaches will help those with other disorders (e.g., muscle diseases, menopause and mid-life issues, and neurodegenerative diseases). Instead, we can ask, which of the multiple approaches being tested now will have the greatest impacts on our lives in the foreseeable future, and how can we all benefit?

Aptamer to Enhance Vitamin C Antioxidant Function Improves Neurovascular Function in Aged Mice
https://www.fightaging.org/archives/2023/06/aptamer-to-enhance-vitamin-c-antioxidant-function-improves-neurovascular-function-in-aged-mice/

Oxidative stress increases with age, the result of a number of age-related dysfunctions that give rise to excessive levels of oxidative molecules. Increasing levels of commonly available antioxidants does not do any good, however, as illustrated by the failure of supplements such as the antioxidant vitamin C to improve health in anything other than cases of vitamin C deficiency. In the case of vitamin C some of this failure may be due to the fact that vitamin C becomes oxidized and loses its function. Here researchers employ an aptamer that binds to vitamin C to provent oxidation, and show that it improves some measures of function in aged mice by allowing vitamin C to become a much more potent antioxidant.

We have developed Aptamin C320, a DNA aptamer that specifically binds to vitamin C and inhibits its oxidation. Aptamers are single-stranded DNA-based oligonucleotides, and Aptamin C320 inhibits the oxidation of vitamin C and preserves its antioxidant activity in the body. NXP032, a complex of vitamin C and Aptamin C320, effectively removes reactive oxygen species (ROS) and increases antioxidant enzyme activity. It maintains a stable antioxidant effect by inhibiting oxidative stress induced by the activation of the antioxidant response element (ARE) pathway in aged mice.

In this study, we investigated the effect of NXP032 on neurovascular stabilization through the changes of PECAM-1, PDGFR-β, ZO-1, laminin, and glial cells involved in maintaining the integrity of the blood-brain barrier (BBB) in aged mice. NXP032 was orally administered daily for 8 weeks. Compared to young mice and NXP032-treated mice, 20-month-old mice displayed cognitive impairments in Y-maze and passive avoidance tests. NXP032 treatment contributed to reducing the BBB damage by attenuating the fragmentation of microvessels and reducing PDGFR-β, ZO-1, and laminin expression, thereby mitigating astrocytes and microglia activation during normal aging. Based on the results, we suggest that NXP032 reduces vascular aging and may be a novel intervention for aging-induced cognitive impairment.

SENS Research Foundation's Senotherapeutic Screening Project is Now Crowdfunding at Experiment
https://www.fightaging.org/archives/2023/06/sens-research-foundations-senotherapeutic-screening-project-is-now-crowdfunding-at-experiment/

Experiment is a crowdfunding platform for small scientific projects. It has been running for quite a few years now, one of the few survivors from the first wave of attempts to make crowdfunding platforms to fund scientific research. It is a challenging goal, the motivations and incentives are completely different from those operating in commercial product crowdfunding. SENS Research Foundation is now using Experiment to raise a modest amount of funds for a senotherapeutic screening program. The Foundation does good work, and I donated.

That part of the industry presently seeking approaches to clear senescent cells, or prevent their formation in order to let the immune system catch up on clearance, is still in the comparatively early stages at this point. It is becoming clear that senescent cells have many different states and origins, and react quite differently to given small molecule drugs. There will be many different senotherapeutics at the end of the day, and more targets and options are needed.

As we become old, the number of senescent cells in our body increases, as well as their harmful effects. Approaches aimed at eliminating senescent cells as they accumulate may not be enough since these cells are continuously produced in our body. We reasoned that preventing healthy cells from becoming senescent in the first place may represent a viable option for treating aging. We have developed a cell model that will allow us to identify candidate therapeutics that prevent cells from becoming senescent. Candidate therapies will then be used either alone or in combination with senolytics for comprehensive targeting of senescence, a strategy that is expected to have superior effects at improving health at older age.

As a model to study senescence in a dish, we will use mouse embryonic fibroblasts that we have isolated from the p16 3MR mouse model. These cells express luciferase driven by the promoter of the senescence related gene p16. Therefore, they become luminescent when they are induced into senescence. This assay will allow us to assess relatively quickly the efficacy of therapeutic candidates that inhibit senescence. Using this cellular model, we will screen a large library of FDA approved drugs for their ability to delay senescence. The cells will be forced into senescence, and drugs applied appropriately. We will be able to measure the efficacy of each drug by measuring luminescence.

Reviewing a Role for the Gut Microbiome in Degenerative Aging
https://www.fightaging.org/archives/2023/06/reviewing-a-role-for-the-gut-microbiome-in-degenerative-aging/

There is a growing interest in the manipulation of the gut microbiome. Changes in the balance of microbial populations occur with age, leading to an increase in harmful, inflammatory species at the expense of species that produce beneficial metabolites. Animal studies have demonstrated that even radical changes in the microbiome from a one-time procedure, such as that produced by fecal microbiota transplant from a young individual, can be sustained over time, rejuvenating the balance of microbial populations and improving health as a result. As yet there seems to be little enthusiasm or funding to run clinical trials in older people, however, despite the sizable benefits produced in animal models.

Far from being a static entity, the gut microbiome (GM) suffers various modifications during different life stages of the individual. The transformation of these biocommunities in older adults is particularly evident after considering that when a person reaches an advanced age, they have been exposed to different environmental factors over an extended period. Multiple studies that analysed GM compositions from people of advanced age concluded that there is a general decrease in microorganism diversity and probiotics, together with an increase in opportunistic agents that could be related to age-related chronic diseases. Although the modifications vary according to the specific age group, numerous studies that found differences in the GM composition of elderly groups (ages 99-80 and 79-60) agree on the predominance of the phyla Bacteriodetes and Firmicutes, the first one being more prevalent in the elderly than in younger adults where the phylum Firmicutes is more abundant.

Similarly, studies have also found decreases in several bacterial groups, including Actinobacteria, certain Ruminococcaceae and Bacteroidaceae members, and Bifidobacterium, Faecalibacterium, Eubacterium, Bacteroides, Clostridium, and Oscillospiraceae genera. In addition, numerous microorganisms, mainly opportunistic pathogens and those related to chronic inflammation, increase during ageing.

In recent years, scientific evidence has shown the possibility of delaying ageing by manipulating the regulatory pathways involved in its bidirectional relationship with the GM. It is known that there is a relationship between intestinal dysbiosis and multiple age-related diseases, such as inflammatory bowel disease and musculoskeletal diseases and neurological conditions. Nevertheless, there are beneficial bacteria that, rather than deleterious consequences of ageing, may contribute to homeostasis maintenance and healthy ageing. In this respect, prebiotics, probiotics, a healthy diet, regular physical activity, and drugs have gained scientific interest in microbial activity regulation.

Pathogenic Tau Drives Cellular Senescence in the Aging Brain
https://www.fightaging.org/archives/2023/06/pathogenic-tau-drives-cellular-senescence-in-the-aging-brain/

Evidence suggests a multidirectional relationship between cellular senescence, chronic inflammation, and toxic tau aggregation in the aging brain. Inflammation is well known to be associated with the onset and progression of neurodegenerative conditions, and lingering senescent cells present throughout the aging body provide a significant contribution to chronic, unresolved inflammatory signaling. Clearing senescent cells in animal models of neurogeneration has been shown to reduce both inflammation and tau aggregation. Here, researchers show that the presence of pathogenic forms of tau protein can provoke cellular senescence and forms of vascular dysfunction in the brain. It is rarely the case that a damaging mechanism of aging stands on its own; it usually makes other damaging mechanisms worse in addition to causing its own direct consequences.

Vascular mechanisms of Alzheimer's disease (AD) may constitute a therapeutically addressable biological pathway underlying dementia. We previously demonstrated that soluble pathogenic forms of tau (tau oligomers) accumulate in brain microvasculature of AD and other tauopathies, including prominently in microvascular endothelial cells. Here we show that soluble pathogenic tau accumulates in brain microvascular endothelial cells of P301S(PS19) mice modeling tauopathy and drives AD-like brain microvascular deficits.

Microvascular impairments in P301S(PS19) mice were partially negated by selective removal of pathogenic soluble tau aggregates from the brain. We found that similar to trans-neuronal transmission of pathogenic forms of tau, soluble tau aggregates are internalized by brain microvascular endothelial cells in a heparin-sensitive manner and induce microtubule destabilization, block endothelial nitric oxide synthase (eNOS) activation, and potently induce endothelial cell senescence that was recapitulated in vivo in microvasculature of P301S(PS19) mice.

Our studies suggest that soluble pathogenic tau aggregates mediate AD-like brain microvascular deficits in a mouse model of tauopathy, which may arise from endothelial cell senescence and eNOS dysfunction triggered by internalization of soluble tau aggregates.

The Gut Microbiome Differs in Characteristic Ways in Patients with Precancerous Colon Polyps
https://www.fightaging.org/archives/2023/06/the-gut-microbiome-differs-in-characteristic-ways-in-patients-with-precancerous-colon-polyps/

The gut microbiome changes with age, the relative abundance of microbial populations shifting in ways that appear connected to chronic inflammation and dysfunction of the intestinal epithelium and intestinal barrier function. Cancer of the colon is an important cause of human mortality, and there is some hope that finding ways to prevent or reverse gut microbiome aging, such as via fecal microbiota transplant from young individuals, will go some way to minimizing colon cancer incidence.

Colorectal cancer is the second leading cause of cancer-related death in the U.S., and rates of colorectal cancer are rising among young adults. Nearly all colorectal cancers arise from a precancerous polyp. One of the best ways to reduce the incidence of colorectal cancer is to stop the growth at the polyp stage. There's more than one way for a polyp to develop. The two main types of polyps are tubular adenomas and sessile serrated polyps. Risk factors for colorectal cancer and polyps include lifestyle factors like being overweight or obese, low physical activity levels, a diet high in red and processed meats, smoking, and alcohol use. These factors also influence the bacteria that live in our intestines, collectively known as the gut microbiome.

Researchers took data from 1,200 people getting routine screening colonoscopies. They gathered information on their health, diet, medications, and lifestyle, as well as analyzed stool samples to determine the bacterial makeup of their gut microbiome. he new research is the biggest study from an extensive collaborative research program, the GI Disease and Endoscopy Registry (GIDER). This registry remains active and ongoing data collection will enable longitudinal follow-up.

The new study is the largest of its kind and analyzed the differences in the gut microbial signature of people without colon polyps, with tubular adenomas, or with sessile serrated adenomas. They also correlated this data with the patient's health and family histories. Bacterial signatures clustered into three groups based on the type and presence of polyps in the colon. Nineteen bacterial species were significantly different in patients with tubular adenomas than in other populations. In patients with sessile serrated adenomas, eight species were significantly different. "The hope is that by changing specific aspects of the diet or the microbiome, we can alter the natural history of these polyps. Interventions to prevent polyp formation or alter their growth patterns may ultimately prevent colorectal cancer."

Investigating the Gut Microbiome of Centenarians
https://www.fightaging.org/archives/2023/06/investigating-the-gut-microbiome-of-centenarians/

The extensive, well-funded search for genetic differences in long-lived individuals has found little: small effect sizes, and only a few genetic variants that replicate in multiple studies. Will the search for gut microbiome differences characteristic of long-lived individuals do any better? This remains to be seen, as the research community is only a few studies into this exercise, and it takes more than a few studies to build a consensus. The evidence to date suggests cautiously optimism, as researchers do see differences in microbial species abundance in exceptionally old individuals versus merely old individuals. As noted here, viral diversity may also be important.

Studying 176 healthy Japanese centenarians, the researchers learned that the combination of intestinal bacteria and bacterial viruses of these people is quite unique. Among other things, the new study shows that specific viruses in the intestines can have a beneficial effect on the intestinal flora and thus on our health. "We found great biological diversity in both bacteria and bacterial viruses in the centenarians. High microbial diversity is usually associated with a healthy gut microbiome. And we expect people with a healthy gut microbiome to be better protected against aging related diseases."

Once we know what the intestinal flora of centenarians looks like, we can get closer to understanding how we can increase the life expectancy of other people. Using an algorithm designed by the researchers, they managed to map the intestinal bacteria and bacterial viruses of the centenarians.

"We have learned that if a virus pays a bacterium a visit, it may actually strengthen the bacterium. The viruses we found in the healthy Japanese centenarians contained extra genes that could boost the bacteria. We learned that they were able to boost the transformation of specific molecules in the intestines, which might serve to stabilise the intestinal flora and counteract inflammation. If you discover bacteria and viruses that have a positive effect on the human intestinal flora, the obvious next step is to find out whether only some or all of us have them. If we are able to get these bacteria and their viruses to move in with the people who do not have them, more people could benefit from them."

Alzheimer's Disease as a Consequence of Vascular Endothelial Dysfunction
https://www.fightaging.org/archives/2023/06/alzheimers-disease-as-a-consequence-of-vascular-endothelial-dysfunction/

Continued efforts to clear amyloid-β in the brain have failed produce significant benefits in Alzheimer's disease patients. This has led to a great deal of theorizing, researchers proposing other disease mechanisms, or different interpretations of the relevance of amyloid-β to the development of neurodegeneration. Most of these hypotheses will be wrong, but that doesn't prevent them from being interesting reading. One class of alternative views of Alzheimer's disease involves placing an increased emphasis on vascular dysfunction in the development of the condition, and the paper here is an example of the type.

Alzheimer's disease (AD) is the most common cause of dementia, accounting for over 70% of dementia cases in individuals above the age of 65 years. The two main pathological hallmarks of AD are extracellular deposits of the amyloid-β (Aβ) protein in the form of amyloid plaques and intracellular aggregates of hyperphosphorylated tau protein in the form of neurofibrillary tangles. Current disease models are based on the notion that abnormal protein aggregation is the primary event in AD, which begins a decade or longer prior to symptom onset, and ultimately leads to synaptic injury and neurodegeneration.

Vascular disease, including arteriolosclerosis, atherosclerosis, microinfarcts, and cerebral amyloid angiopathy (CAA), is a common co-pathology which is observed in 20-80% of AD brains at autopsy. Furthermore, almost all AD brains display evidence of endothelial and capillary degeneration even in the absence of other forms of macrovascular pathology. Significant and bidirectional interactions between AD and various forms of vascular pathology have been well documented; amyloid and tau toxicity disrupts the blood-brain barrier (BBB) and alters vascular permeability, and structural or functional damage to cerebral vasculature impairs amyloid clearance and promotes tau aggregation.

Previous neuropathological studies examining vascular pathology in AD have focused primarily on pathology within the small- and medium-sized arteries and arterioles; however, there is growing evidence to suggest that "micro"-vascular disease (i.e., at the capillary level) and alterations to specific vascular constituents, such as endothelium and pericytes, play an important role in AD pathogenesis. Impaired cerebral blood flow (CBF) is a common and early predictor of AD pathology, which possibly precedes abnormal protein aggregation and directly contributes to neuronal and synaptic loss in even the earliest pre-symptomatic stages of the disease. These observations support the notion that the onset of AD may be primarily influenced by vascular, rather than neurodegenerative, mechanisms and emphasize the importance of further investigations into the vascular hypothesis of AD.

Chronic Inflammation in Age-Related Anemia
https://www.fightaging.org/archives/2023/06/chronic-inflammation-in-age-related-anemia/

Chronic inflammation is a feature of aging, driven by mechanisms such as an increased burden of senescent cells and overactivation of the innate immune system in response to cellular stress. Researchers here present data to suggest that chronic inflammation contributes to age-related anemia, a reduced production of red blood cells that perhaps occurs via an indirect disruption of iron metabolism by inflammatory signaling, and that in turn lowers the available levels of iron needed for the creation of red blood cells.

Anemia is a common hematological disorder that affects 17% of persons older than 65 years. The World Health Organization (WHO) defines anemia as a decreased number of erythrocytes and/or decreased hemoglobin (Hb) levels of less than 12.0 g/dL in women and 13.0 g/dL in men. In older adults, anemia can be divided into nutritional deficiency anemia, bleeding anemia, and unexplained anemia that might be caused by the reduced erythropoietin (EPO) activity, the progressive erythropoietin resistance of bone marrow erythroid progenitors and the chronic subclinical pro-inflammatory state. Overall, one-third of older patients with anemia have a nutritional deficiency which mainly includes iron, folate or vitamin B12 deficiency, one-third have a chronic subclinical pro-inflammatory state and a chronic kidney disease, and one-third suffer from anemia of an unknown cause.

Understanding the pathophysiology of anemia in this population is crucial because it contributes to frailty syndrome and falls, cognitive decline, depression, functional ability deterioration, and early mortality. A prospective cohort analysis of 3758 patients aged 65 years and older showed that a new-onset anemia was associated with an increased mortality risk with a drop in Hb of 1 g/dL.

The pro-inflammatory state in older age, called inflammaging, is manifested by the release of a large number of inflammatory mediators that are produced to repair damage at the tissue level. Inflammaging is a result of changes in the immune system also known as immunosenescence. The inflammatory molecules produce adverse effects on the cells of the hematological system, and these include iron deficiency, reduced EPO production and elevated phagocytosis of erythrocytes by hepatic and splenic macrophages, and also enhanced eryptosis by oxidative stress in the circulation.

In this study, low Hb concentration was observed to be associated with subclinical, chronic inflammation, exhibited by high levels of IL-1β and TNFα. In the large InCHIANTI study, the unexplained anemia cohort (36% of all the anemic population) was found to have higher levels of pro-inflammatory markers and higher resistance of bone marrow erythroid progenitors to erythropoietin compared to non-anemic controls. The mechanisms underlying low Hb levels in older adults are multifactorial and complex. Our study suggested that the underlying mechanisms involve subclinical chronic low-grade inflammation, bone marrow resistance to EPO, and changes in hepcidin levels, ultimately affecting iron metabolism and resulting in lower serum iron levels.

Senescent Cells Appear Involved in Graft-Versus-Host Disease
https://www.fightaging.org/archives/2023/06/senescent-cells-appear-involved-in-graft-versus-host-disease/

Now that increasing attention is given to senescent cells in the biology of aging, their involvement in a wide range of conditions has been uncovered. The transient creation of senescent cells is a part of wound healing, a process that is harmed by the growing burden of lingering senescent cells that occurs with advancing age, and the inability of the aged immune system to remove these cells in a timely fashion. Given the role in wound healing, is perhaps not surprising to find senescent cells involved in graft-versus-host disease following surgical transplantation of tissue. Senolytic therapies may prove to be useful here, as they have in animal studies of many other conditions.

Graft-versus-host disease (GVHD) is a life-threatening systemic complication of allogeneic hematopoietic stem cell transplantation (HSCT) characterized by dysregulation of T cell and B cell activation and function, scleroderma-like features, and multi-organ pathology. The treatment of cGVHD is limited to the management of symptoms and long-term use of immunosuppressive therapy, which underscores the need for developing novel treatment approaches.

Notably, there is a striking similarity between cytokines/chemokines responsible for multi-organ damage in cGVHD and pro-inflammatory factors, immune modulators, and growth factors secreted by senescent cells upon the acquisition of senescence-associated secretory phenotype (SASP). In this pilot study, we questioned the involvement of senescent cell-derived factors in the pathogenesis of cGVHD triggered upon allogeneic transplantation in an irradiated host. Using a murine model that recapitulates sclerodermatous cGVHD, we investigated the therapeutic efficacy of a senolytic combination of dasatinib and quercetin (DQ) administered after 10 days of allogeneic transplantation and given every 7 days for 35 days.

Treatment with DQ resulted in a significant improvement in several physical and tissue-specific features, such as alopecia and earlobe thickness, associated with cGVHD pathogenesis in allograft recipients. DQ also mitigated cGVHD-associated changes in the peripheral T cell pool and serum levels of SASP-like cytokines, such as IL-4, IL-6, and IL-8Rα. Our results support the involvement of senescent cells in the pathogenesis of cGVHD and provide a rationale for the use of DQ, a clinically approved senolytic approach, as a potential therapeutic strategy.

Intermittent Senolytic Treatment with Dasatinib and Quercetin Produces Benefits in Non-Human Primates
https://www.fightaging.org/archives/2023/06/intermittent-senolytic-treatment-with-dasatinib-and-quercetin-produces-benefits-in-non-human-primates/

Researchers here report on the outcome of six months of monthly senolytic therapy in cynomolgus macaques. The results are broadly positive, as one might expect from the established human data. Dasatinib is a chemotherapeutic drug, but senolytic dosing is not sustained as is the case in the treatment of cancer, and side-effects are much reduced as a result. It remains to be seen as to what the optimal dose and dose schedule for this treatment will be. Researchers are trying a range of options, and arguably the human trials conducted by the Mayo Clinic are using too low a dose. Time will tell, but there is a need for more clinical trials, and an opportunity for philanthropists to step in and run few-hundred individual, affordable, safe clinical trials of this cheap senolytic treatment to provide support for physicians to use the therapy off-label for many age-related conditions.

Cellular senescence increases with aging and results in secretion of pro-inflammatory factors that induce local and systemic tissue dysfunction. We conducted the first preclinical trial in a relevant middle-aged nonhuman primate (NHP) model to allow estimation of the main translatable effects of the senolytic combination dasatinib (D) and quercetin (Q), with and without caloric restriction (CR). A multi-systemic survey of age-related changes, including those on immune cells, adipose tissue, the microbiome, and biomarkers of systemic organ and metabolic health are reported.

Age-, weight-, sex-, and glycemic control-matched NHPs (D+Q, n=9; vehicle [VEH] n=7) received two consecutive days of D+Q (5 mg/kg+50 mg/kg) monthly for 6 months, where in month six, a 10% CR was implemented in both D+Q and VEH NHPs to induce equal weight reductions. D+Q reduced senescence marker gene expressions in adipose tissue and circulating PAI-1 and MMP-9. Improvements were observed in immune cell types with significant anti-inflammatory shifts and reductions in microbial translocation biomarkers, despite stable microbiomes. Blood urea nitrogen showed robust improvements with D+Q. CR resulted in significant positive body composition changes in both groups with further improvement in immune cell profiles and decreased GDF15, and the interaction of D+Q and CR dramatically reduced glycosylated hemoglobin A1c.

This work indicates that 6 months of intermittent D+Q exposure is safe and may combat inflammaging via immune benefits and improved intestinal barrier function. We also saw renal benefits, and with CR, improved metabolic health. These data are intended to provide direction for the design of larger controlled intervention trials in older patients.