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

• The Clinical Trial Abundance Proposals Seem Too Little to Lead to Meaningful Change
• A Look Back at 2024: Progress Towards the Treatment of Aging as a Medical Condition
• The Integrated Stress Response Marks Dysfunctional Microglia in Alzheimer's Disease
• Does Low Socioeconomic Status Literally Accelerate Aging?
• Why Do Oocytes Not Accumulate Mitochondrial DNA Mutations?
• Developing a Cell Model of Aging-Like Mitochondrial Mutational Damage
• Urolithin A Derivatives Targeting Mitophagy in Clinical Trials
• Lithocholic Acid in Calorie Restriction
• A CpG Oligodeoxynucleotide Promotes Bone Formation
• Reprogramming Colon Cancer Cells into Normal Cells
• Extracellular Vesicle Therapy as a Treatment for Osteoarthritis
• More Whales May be Long Lived than Previously Suspected
• Brown Adipose Tissue is Beneficial to Metabolism and Improves Exercise Performance
• Reviewing What is Known of Age-Related Changes in Transcriptional Elongation
• Assessing Mitochondrial Decline with Age Using Frozen Tissue Samples

The Clinical Trial Abundance Proposals Seem Too Little to Lead to Meaningful Change
https://www.fightaging.org/archives/2024/12/the-clinical-trial-abundance-proposals-seem-too-little-to-lead-to-meaningful-change/

Regular readers will know that I'm not in favor of the present state of medical regulation. In this I am not alone. Many people think that some fraction of the cost of obtaining regulatory approval of new therapies is entirely unnecessary, some fraction of the degree of rigor imposed on manufacture and clinical trials is entirely unnecessary. Clinical trials conducted in Australia cost half of those conducted in the US or Europe, because the Australian community has declared that full Good Manufacturing Practice (GMP) procedures mandated by the FDA in the US and EMA in the EU are in fact unnecessary. Something like 10% of all early stage clinical trials worldwide take place in Australia. In that country the government has delegated ethics and assessment of risk to their equivalent of competing institutional review boards, each associated with a specific clinical trial center. It is a good example of the way in which centralization and diminished competition penalizes progress.

Do you think that the right number for the degree of waste currently imposed by regulators is half? More than half? Less than half? It is a huge cost in a world in which $30M to $40M is needed to move from preclinical proof to completing a phase 1 safety trial in a small number of volunteers in the US or EU. That cost means that a sizable fraction of potential medicines are never developed. Halve that cost and more medicines will be developed. Yet those within the system are very quick to defend the excess: regulatory capture rules, and the established pharma industry uses the regulatory system in order to reduce competition from upstate therapeutic developers. None of this is to the benefit of humanity as a whole.

Since the turn of the century, the cost of developing new therapies has more than doubled. The regulators ask for ever more proof, ever more tests, ever more rigor, never strongly penalized for the invisible graveyard of therapies and patients that results. This is how complex systems trapped in the later stages of regulatory capture move forward. The dominant players retain their dominance by becoming a part of the system that suppresses the potential for progress. This is widely recognized, and numerous patient advocacy groups have come, tried to change the system from within, largely failed, and vanished. The Clinical Trials Abundance project is one such, and by no means the most radical. I think their proposals change too little to make a difference even if implemented. I believe that the only path likely to lead to radical change is the development of a robust clinical development ecosystem outside the FDA, EMA, and related regulatory systems, built atop the present medical tourism infrastructure. Something to compete at a much lower price point.

The Case for Clinical Trial Abundance

The need to make drug development more efficient has become increasingly pressing. US healthcare spending growth is predicted to reach nearly 20% of GDP by 2032 and exceed GDP growth itself for structural reasons, like an aging society. Meanwhile, given high medication prices and little political appetite to cut Medicare spending, there is mounting pressure to reduce drug development costs. In the face of these cross-pressures, the best policy approach is a supply-side innovation agenda, aimed at lowering the costs of trials.

We have several reasons to be optimistic about our ability to cut clinical trial costs and timelines. One proof-of-concept is the RECOVERY trial, which cost about 1/80th of a traditional randomized controlled trial (RCT) and likely saved hundreds of thousands of lives by demonstrating the efficacy of steroids for COVID-19. RECOVERY showed the enormous cost and time savings possible if trials are kept tightly focused on important questions and trial enrollment/organization is made as easy as possible. We can also look at historic examples of large trials (e.g., the polio vaccine field trials) that ran on time and answered important questions, by avoiding cumbersome and unnecessary administrative delays.

Many stakeholders agree on the urgency of the problem, often framed as clinical trial modernization. Reducing the cost and difficulty of generating high-quality medical evidence is a rare area where most experts agree on the goals. Beyond these specifics, many of our memos follow the guiding question: "What would a permanent, US-scale RECOVERY trial look like and accomplish?" With dramatically cheaper trials, we would more quickly sift through poorly evidenced clinical practice. New therapies would cost less to test in humans, and we would have answers and innovation sooner. Beyond speeding up the approval of new drugs, cheaper and faster trials would also allow more kinds of questions to be asked. When a large trial costs $100 million to carry out, some questions simply don't get asked.

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A Look Back at 2024: Progress Towards the Treatment of Aging as a Medical Condition
https://www.fightaging.org/archives/2024/12/a-look-back-at-2024-progress-towards-the-treatment-of-aging-as-a-medical-condition/

Another year has passed, and here we find ourselves once again another twelve months deeper into the 21st century and all of its promised wonders. The Golden Age science fiction authors were gloriously wrong in their extrapolation of trends of energy use, computation, and medicine, predicting a 21st century of slide-rules, ubiquitous heavy lift capacity into orbit and beyond, and a world in which 60-year olds still had bad hearts and little could be done about it. Instead, energy turned out to be hard, while computation enabled the biotechnology revolution and the prospect of longer, healthier lives through radical advances in medicine. Expansion into space awaits while we focus instead on the small-scale of our cellular biochemistry.

The trend in human life expectancy over the long term continues upwards, despite the short term negative impacts of obesity. Yet there remains a strong need for advocacy for aging research and the development of novel therapies to target the mechanisms of aging, even as this field grows apace. The progression of aging remains incompletely understood and much debated even given the more extensive knowledge of fundamental forms of damage that cause aging. The mainstream of our culture has yet to adopt a war on aging as it adopted the war on cancer. The advocacy of the first two decades of this century continues, but changing over time. Noted advocacy organizations SENS Research Foundation and Lifespan.io announced that they would merge; the book "The Death of Death" is now available in English, finally.

In part there is change because, unlike the early 2000s, there is now a longevity industry worthy of the name. It is a part of the broader biotech industry, and subject to the same perverse incentives, direct costs of regulation, and other issues that ensure a very long, slow development cycle. The pace of progress is nowhere as fast as we'd like it to be, even setting aside the terrible biotech investment market of the past two years, and some advocates have shifted their focus to this problem. Nonetheless, the wheel turns. Some of us are even optimistic about the next few decades. Meanwhile, the more adventurous arms of various governments are starting to come to the table to support areas of development, such as better measurement of biological age via clocks and other means, that are well underway. Typically one should expect to see government support arrive late to the table, in low-risk, high-attention areas that are already a foregone conclusion and well on their way to that conclusion. Thus ARPA-H is now entering the field of measurement and clock development.

A growing list of therapies are in preclinical development, a few programs reaching into clinical trials. Even if too many of the therapies under development aim only to modestly slow the progression of aging, there are still a good many potential rejuvenation therapies focused on repair of damage. This year, Fight Aging! noted updates from Cyclarity and Repair Biotechnologies (a few times, including at the Rejuvenation Startup Summit 2024) on atherosclerosis, Mitrix Bio on mitochondrial transplantation, Kimer Med on their implementation of the DRACO antiviral technology, Lygenesis on human trials of liver organoid implants. If you're looking for a broad view of the longevity industry and its progress, Aging Biotech Info continues to be a great resource; see an early 2024 interview with the maintainer for some of the background.

Last year's retrospective focused on categories of age-related disease rather than the forms of age-related damage outlined in the Strategies for Engineered Negligible Senescence (SENS) proposals, and was both less helpful and much more onerous to assemble as a result, I feel. So this year it is back to the fundamental causative mechanisms of aging, plus a couple of extra categories to cover some areas of personal interest.

Cell Loss / Atrophy

One of the most evident, early examples of cell loss leading to atrophy is the aging of the thymus, and the consequent loss of immune function that follows. Efforts to produce regeneration of the thymus lapsed for some years in the mid to late 2010s, but are now a going concern once more - multiple biotechnology companies are working on thymic regrowth. Replacement of cells via transplantation is one of the plausible paths forward to comprehensive therapy addressing cell loss and tissue atrophy, even where these cell therapies are really just ways to deliver signal molecules that adjust the behavior of native cells to increase regeneration. Cost-effective cell therapies will need universal cells, however. Progress is occurring on this front, but it is slow. Cell therapy examples from recent years include the ongoing efforts to provide new motor neurons to Parkinson's patients, delivery of cardiomyocytes to the aging heart, and cell therapy to restore the aged and atrophied thymus.

Beyond cell therapy lies tissue engineering and transplantation of that engineered tissue. This is a field with great promise, but which continues to struggle with goals such as creating the vasculature needed to support tissues larger than a few millimeters in size and speeding up the process of bioprinting. Cells survive transplantation better when introduced as tissue or in artificial tissue-like structures; it is even possible to provide those structures alone without the cells. A liver patch of only extracellular matrix produces benefits, for example. Recent work on tissue transplants include: efforts to replace portions of the neocortex; a clinical trial using sheets of corneal cells to replace a damaged cornea.

The alternative is to provoke replication in existing populations, such as by increasing stem cell function, or reactivation of developmental processes for replication in cell populations that normally do not replicate all that much in adults. A better understanding of how aged stem cells become dysfunctional than is presently the case will almost certainly be needed. Inroads are made in model organisms, but this area of research has the look of a long way to go yet. Changes in the stem cell niche, the supporting cells surrounding stem cells, are likely important. From the past year, a few examples of producing new cells in situ: gene therapy to promote cardiomyocyte replication in a damaged heart; more gene therapy to promote regeneration of lost sensory hair cells; yet more gene therapy to trigger muscle growth via MYC-1 expression; upregulation of cyclophilin A and increased PF4 both improve hematopoietic stem cell function; efforts to discover regulators of stem cell exhaustion; a similar search for regulators of neural stem cell function.

Mutation and Other Damage to Nuclear DNA

Stochastic DNA damage is mostly harmless, taking place in cells with few replications left, or in unusued regions of the genome. But mutations to stem cells and progenitor cells can spread throughout a tissue, producing somatic mosaicism. It remains unclear as to how important this is to aging, but most of the evidence for some role emerges from clonal hematopoiesis of indeterminate potential, somatic mosaicism in immune cells. This may contribute to kidney disease and risk of stroke, for example. What can be done about DNA damage? This seems a tough problem, but some paths forward have been suggested. Recently, it was discovered that natural examples of very efficient DNA damage response mechanisms can feasibly be transferred between species.

Damage in the structure of nuclear DNA and its surrounding machinery may be more subtle overall than simply mutational alterations to DNA sequences. For example, DNA damage and the repair response to that damage can indirectly cause RNA polymerase II to stall more often in reading DNA, altering gene expression for the worse. A fair number of researchers remain skeptics as to whether random mutation contributes meaningfully to aging. But research in recent years now suggests that random DNA double strand breaks and the resulting repair processes may alter the epigenetic regulation of nuclear DNA structure to cause many of the characterisitc changes in gene expression observed in aged tissues. To the extent that this is the case, we might think of partial reprogramming, a way to reset epigenetic expression by exposing cells to the Yamanaka factors, as a rejuvenation therapy. Certainly, a steady flow of animal studies of targeted reprogramming appear to demonstrate benefits. In the vasculature, for example, reducing hypertension. Or in the brain, where it reverses loss of cognitive function and is protective in models of neurodegeneration.

Another interesting field of study involves transposons, DNA sequences left behind by ancient viral infections that are repressed in youth, but run amok in later life to copy themselves across the genome, causing mutational damage. It remains unclear as to what degree this mechanism contributes to aging, but the research community is in search of the causes of transposon activation in later life. Perhaps the most intriguing evidence supports an important role for degree of transposon activity to determine the differences in life span between breeds of dog.

Mitochondrial Dysfunction

The pure SENS view of mitochondrial dysfunction is that the important component of it arises from damage to mitochondrial DNA. Researchers recently built a new cell model to better assess this mechanism. This is distinct from a more general malaise of impaired mitochondrial function that arises from gene expression changes with age, impairing mitochondrial dynamics, function, and the quality control process of mitophagy. It also results in mislocalized mitochondrial DNA fragments that provoke a maladaptive inflammatory response. These changes may result from cycles of DNA double strand break repair and their effects on nuclear DNA structure, and thus are downstream of damage to nuclear DNA. It remains clear as to how far one can go in restoring lost mitochondrial function by only restoring youthful gene expression, or improving mitophagy. Improvement in mitophagy is actually quite hard to measure, and there is much debate over the existing data for age-related mitophagy decline. Mitophagy interacts with the fusion and fission of mitochondria, and researchers have shown that adjusting the balance of fusion and fission in either direction can extend life in nematode worms. Equally, greater fragmentation of mitochondria due to excessive fission appears pathological in mammalian tissue.

Mitochondrial dysfunction is known to be important in muscle aging, in the heart and elsewhere in the body, and may interact with chronic inflammation to produce sarcopenia. Failing mitophagy is implicated in neurodegeneration, as is the consequent loss of mitochondrial function, an important mechanism in the aging of the brain. Mitochondrial dysfunction is also implicated in atherosclerosis, making the vascular cell dysfunction characteristic of the condition that much worse. Mitochondrial dysfunction has a role in ovarian aging, and in dry eye disease.

Approaches to address age-related mitochondrial dysfunction include allotopic expression of mitochondrial genes in the cell nucleus, less vulnerable to damage, and a backup source of mitochondrial proteins to prevent mutational damage to mitochondrial DNA from affecting mitochondrial function. Progress on this is taking place, but slowly; most recently researchers have produced a mouse lineage to demonstrate that ATP8 allotopic expression safely rescues function in loss of function ATP8 mutants. Then there is also the prospect of transplantation of functional mitochondria harvested from cultured cells or donor cells, shown to improve muscle function. Partial reprogramming of cells from aged tissues via short-term exposure to the Yamanaka factors has also been shown to improve mitochondrial function in the course of resetting epigenetic patterns. In terms of more targeted approaches to upregulate mitophagy, researchers have looked for targets in the function of HKDC1 and TFEB, but most of the mitophagy-related effort is focused on supplement-like molecules and their derivatives, such as the various groups working on urolithin A. While there are potential ways to increase the manufacture of new mitochondria, it isn't clear that this sort of enhancement will help in the aged environment.

Extracellular Matrix Damage

Changes in the physical properties of tissue due to age-related damage to the molecules of the extracellular matrix can produce cascading consequences. This is particularly true of stiffening of blood vessel walls, a contributing cause of hypertension, which in turn damages the delicate tissues of the kidney. Relatively little work takes place on this aspect of aging, and this line item in the SENS list of forms of molecular damage that drive aging includes more than just changes in physical properties. Any change in the extracellular matrix might change cell behavior for the worse in some way. There is every reason to think that a lot of this sort of thing takes place in the aging body, and that we have only scratched the surface of an understanding of it.

Senescent Cells

Senescent cells accumulate with age. They produce inflammatory signaling that is harmful to cell and tissue function, and encourages other cells to become senescent. Replication stress in cell populations may be an underappreciated source of senescence in later life. It is possible to correlate mortality to circulating levels of some of those signal molecules. Researchers have connected this signaling to the cells's response to the mutational damage that occurs as cells enter the senescent state. The consensus in the research community is that senescence is a complex state, or collection of states, and we remain far from a complete understanding of senescence. There are debates over whether everything presently classed as a senescent cell is in fact a senescent cell, or whether most of what are currently thought to be senescent tissue cells are in fact senescent tissue resident immune cells.

Nonetheless, senescent cells are linked to many age-related conditions and declines, and a selection of research from just the last year is extensive: skin aging is always a popular topic, and worthy of many mentions in the context of the burden of senescent cells; osteoporosis, particularly following menopause; macrophage signaling induces senescence in aging bone tissues; the onset of Alzheimer's disease and, for different reasons, Parkinson's disease; neurodegeneration more generally, such as via an increase in senescent T cells, increase in dysfunctional microglia, or aged neurons re-entering the cell cycle to become senescent; the relevance to neurodegeneration is worth emphasizing twice, as there is considerable enthusiasm in the research community for the development of therapies targeting senescent cells in the brain; moving on, there is the impairment of chemotherapy effectiveness by senescent cells; loss of capillary density in aged tissues; endothelial dysfunction in the vasculature; impairment of macrophage tissue maintenance functions; disruption of adrenal gland function; declining kidney function; excess cholesterol inside macrophages in atherosclerotic plaque provokes their senescence, contributing to the formation of unstable plaques prone to rupture; macular degeneration of retinal tissue; the aging of the heart and vasculature leading to cardiovascular disease; the role of senescent cells in cancer is both positive and negative for the patient, making the use of senolytic therapies more challenging than in other contexts; senescent B cells affect the ability of the immune system to garden the body's microbiomes; the aging of the ovaries; liver aging; loss of capacity for hair regrowth; the development of osteoarthritis; the secondary harms that follow stroke.

The first senolytic therapy combining dasatinib and quercertin continues to produce mostly promising results in clinical trials, most recently in older women with osteoporosis. The variety of senolytic therapies under development continues to grow at a fair pace year over year. Senolytic CAR-T therapies and adoptive transfer of other immune cells will likely be too expensive to be practical in the broader aging population, but continue to demonstrate promise in animal models. The cancer field may adopt these immunotherapy approaches to target senescent cancer cells, however. Topical applications of senolytics for skin aging continue to be developed, including a topical formulation of navitoclax shown to clear senescent cells from skin in mice. Novel biochemistry potentially relevant to therapies targeting senescence continues to be uncovered: PKM2 aggregation; that senescent cells use immune checkpoints to evade attention from immune cells; further, high mobility group proteins may turn out to be good targets to suppress senescence; and PAI-1 appears important in the creation of senescent cells.

A range of flavonoids are senolytic to varying degrees, and new ones are discovered on a regular basis, such as 4,4′-dimethoxychalcone. Researchers would like to improve the efficiency of flavonoid senolytics via delivery in nanocarriers, or by engineering better versions of molecules such as fisetin. Further, attempts are underway to find other natural compounds that can replace the chemotherapeutic drug dasatinib in the dasatinib and quecertin senolytic combination. The class of PI3K inhibitors continues to produce senolytic compounds. More diligent mapping of the surface features of senescent cells also continues to yield new targets for new selective ways to kill these errant cells. Researchers have proposed searching for senolytic lipids, and discovered a few that kill senescent cells via ferroptosis. Antidiabetic SGLT2 inhibitors are senolytic in overweight mice, but this seems likely to have little effect outside the context of obesity and the pathological diabetic metabolism. High intensity exercise is technically senolytic, but at the point at which we are calling lifestyle interventions senolytic, I feel the word begins to lose its meaning. At the end of the day, senolytics are just one part of a greater toolkit of rejuvenation therapies that will have to be used in combination.

An alternative approach to senolytics, less well developed, is to find ways to shut down the inflammatory signaling produced by senescent cells. It isn't clear that this is going to be as useful or progress as rapidly, given the incompletely understood complexity of the mechanisms by which senescent cells generate inflammation - but people are certainly working on it! Approaches to this end from the past year include CISD2 upregulation and selective sabotage of citrate metabolism.

Intracellular and Extracellular Waste, Including Amyloids

The amyloid-β that accumulates with age in the brain is an antimicrobial protein. This may explain associations between persistent viral infection and Alzheimer's disease, in that greater production of amyloid-β allows more of it to misfold and aggregate to contribute to Alzheimer's pathology. Other causes of amyloid-β aggregation may include the metabolic disruption produced by excess visceral fat. Amyloid-β may cause blood-brain barrier leakage, and this might be as important as other aspects of its pathology, such as provoking chronic inflammation and inhibiting synaptic proteasome function. While the amyloid cascade hypothesis remains firmly in the driver's seat of research strategy in the matter of Alzheimer's disease, one still finds fundamental debates taking place, such as whether it is the amyloid-β or other proteins that coincide with amyloid-β causing pathology, and the degree to which significant harms precede evident symptoms. More positively, it seems that loss of brain volume resulting from anti-amyloid therapies is not actually harmful, but results from clearance of amyloid. After amyloid-β in the progression of Alzheimer's disease comes tau aggregation and more severe harm to brain tissue. Tau aggregation induces inflammatory dysfunction in supporting cells in the brain, and consequent damage to synapses.

TDP-43 aggregation is a more recently discovered form of proteopathy relevant to neurodegeneration, and is more common than previously thought. It may also contribute to Huntington's disease pathology. Researchers continue to delve into the mechanisms of TDP-43 pathology. Attention has been given to NPTX2 as a link between TDP-43 aggregates and cell death. Like amyloid aggregation, TDP-43 aggregation may extend beyond brain tissue into the vasculature. Harm resulting from TDP-43 is not the only recent discovery! DDX5 also appears capable of forming prion-like aggregates.

The misfolding and aggregation of α-synuclein causes Parkinson's disease. α-synuclein pathology appears to interact with lipid metabolism in the brain, a bidirectional relationship shaping the spread of a synucleinopathy such as Parkinson's disease. As is the case for other protein aggregates associated with neurodegenerative conditions, α-synuclein aggregates can be found outside the brain - in skin, for example, or in exosomes in blood, opening the possibility of early detection. Outside the brain, researchers also see amyloid aggregates encouraging calcification in the heart. While thinking of the whole body, I should also note what would in a better world be a large area of research, into clearing out the various forms of lingering molecular waste, some of it altered proteins, that accumulate in the lysosomes of long-lived cells to cause dysfunction in normal recycling processes. Very little work takes place here, however; a few research teams, a few preclinical programs. In some years nothing comes to notice. This was one of those years.

In terms of approaches to clear protein aggregates, manipulating the behavior of microglia in the brain seems promising. Inhibition of p16 works, for example, perhaps by reducing the degree of senescence in this cell population. Also interfering in the LILRB4-APOE interaction, or upregulation of CCT2 to promote aggrephagy. Alternatively, there is the approach of preventing astrocytes from crowding out microglia and blocking access to amyloid plaques. Amyloid-targeting anticalins have been suggested as a strategy. Amyloid-β clearance via immunotherapy (with meaningful risk of unpleasant side-effects) is now a going concern, with enough data for meaningful commentary on what it might imply. It continues to appear that the amyloid cascade hypothesis is correct, and clearing amyloid in late disease stages doesn't help all that much. There, the target protein aggregate is hyperphosphorylated tau, and numerous approaches are under development. A more recent example is a clever evolution of proteolysis targeting chimera (PROTAC) technology that encourages the dephosphorylation of hyperphosphorylated tau, reducing the pace of aggregration. Another approach is delivery of anti-tau intrabodies via mRNA therapies. Others are investigating TYK2 inhibition as a way to slow the pace of pathological tau phosphorylation. For α-synuclein pathology, researchers are exploring use of a bacterial peptide that inhibits aggregate formation and antisense oligonucleotides to inhibit α-synuclein protein expression.

Gut Microbiome

Age-related alterations to the gut microbiome might arguably be added to the existing categories of SENS as another form of damage. This could occur independently of other mechanisms of aging, existing as a fundamental form of damage, even given that it is likely largely downstream of immune aging when it does occur over time. Loss of anti-microbial peptides may be important in reducing the ability of the immune system to garden the gut microbiome, for example. The gut microbiome is noted to be distinct in long-lived individuals. Harmful changes to the microbiome can be catalogued, but are far from fully understood. Nonetheless, these changes can be reversed independently of other aspects of aging by fecal microbiota transplantation from young donors to old recipients, producing benefits such as extended life span in animal models - or the reverse when transplanting an old microbiome into a young animal. Icariin is another approach to improving the composition of the gut microbiome. Flagellin immunization also works, demonstrated to extend life in mice. Sustained calorie restriction and intermittent fasting may improve the gut microbiome, or at least slow its aging. It is possible that delivery of genetically engineered microbes may also achieve useful goals, but this is far from proven in practice.

Restoration of a youthful gut microbiome may treat neurodegenerative conditions such as Parkinson's disease, and mechanisms to explain that outcome include its effects on astrocytes in the brain. Importantly, a clinical trial showed no benefits of fecal microbiota transplantation to patient's with Parkinson's disease. While the misfolding of α-synuclein characteristic of the condition may start in the gut in many patients, induced by a dysfunctional microbiome before spreading to the brain, addressing the gut contribution is likely too little, too late once evident symptoms have started. Despite this data point, the limited clinical trial data in humans for modification the gut microbiome, even transiently, is generally supportive of greater efforts in this direction.

Evidence exists for the gut microbiome to contribute to life span and numerous specific aspects of aging via mechanisms such as increased chronic inflammation: longevity in rabbits correlates with the gut microbiome composition, as do physiological changes in aged mice; aging of the ovaries; aging of the musculoskeletal system; increased risk of arrhythmia; Alzheimer's disease, where a fair amount of effort is devoted to trying to identify distinct microbial populations in patients, which may include infectious pathogens; reduced grip strength indicative of sarcopenia and frailty; loss of hematopoietic stem cell function; old individuals exhibit a distinct fungal gut microbiome; aging of bone leading to osteoporosis, and identification of specific features of the microbiome that correlate with this aspect of aging; the lymphatic system likely plays an important role in trafficking microbes and microbial metabolites from the intestine to the brain to cause harm; a novel way in which the aging microbiome may cause harm is by increasing intestinal permeability, allowing digestive enzymes to leak into tissues; it may also promote thymic involution, accelerating immune aging; rheumatoid arthritis may be driven by a distinct gut microbiome; menopause and the composition of the gut microbiome have a bidirectional relationship.

Cryonics

At the present pace of development of rejuvenation therapies, every older adult is going to age to death. Cryonics, the low temperature preservation of the structure of the mind following clinical death, remains a necessary industry in waiting. It has yet to exist in any way meaningful to the vast majority of people. Yes, one can be cryopreserved. No, the protocols are nowhere near as robust as we'd like them to be, and there are too few cryopreservation organizations to save more than a tiny handful of people.

There is a clear and well-defined roadmap for the technological capabilities needed to reach the fully developed, vast cryonics industry of the future. The road to turning the present small non-profit cryonics organizations into a full-fledged industry to compete with the grave and oblivion most likely starts with reversible cryopreservation of organs for the transplant industry. Solve that problem, and there is an engine to bring funds and interest into tissue preservation more generally. We will find ourselves half-way to convincing the world that the same can and should be done for people on the verge of death, to preserve them for a future in which both the technology and the will exist to safely restore a body and brain from both crypreservation and the damage of aging.

Aging Clocks

While not under the SENS heading, it is interesting to keep an eye on the development of clocks to assess biological age - or at least which are claimed to assess biological age. It may be fair to say that meaningful progress towards rejuvenation therapies can only occur to the degree to which we can effectively measure aging. This, at least, is a consensus sentiment in the research community. That community produces new clocks at quite the pace. In just the last year: a novel proteomic clock; an aging clock built from the senescence-associated secretory phenotype of senescent monocytes; a clock built from the metabolome called MileAge; a clock built from cheek swab DNA methylation data; a clock built from brain MRI imaging data; more novel transcriptomic clocks; the development of organ-specific proteomic clocks; a clock based on retrotransposon DNA methylation; aging clocks built from retinal imaging data; a clock based on protein aggregation; a physiological aging clock using clinical biomarker data.

A growing body of clinical trial data includes clock measures, enough now to start to say something about how useful the mainstream clocks are in practice. Some would argue it is time to stop building new clocks and standardize on the best of the established clocks. While epigenetic age acceleration in many clocks correlates well with age-related disease and mortality, a fair number of issues remain to be overcome. Existing clocks have many quirks, such as being responsive to psychological stress or time of day. Clock data is obtained from immune cells in a blood sample, and different immune cell populations exhibit different patterns of epigenetic aging, biasing results. This is also true when considering differences between mammalian species. Work on correcting this issue has led to the concept of intrinsic epigenetic age. Nonetheless, blood sample clocks do not generalize well to other tissues. The greatest challenge, however, is how to understand how the measured changes making up the clock actually relate to underlying processes of aging and disease. Some inroads are being made, such as separating harmful from adaptive changes and understanding how much of what is measured is epigenetic drift.

Other novel work on clocks this past year included: improvements to the Pace of Aging clock; advocacy for clocks built on clinical biomarkers and risk factors; a better grasp as to how lifestyle choices affect epigenetic age; demonstrating that modern clocks do show a slowing of aging for people exhibiting greater physical fitness; continued research into glycosylation clocks; quantifying the level of uncertainty we should expect from clocks that assess biological age; noting that chronic liver disease accelerates epigenetic aging in other organs; the negligibly senescent axoltl exhibits little alteration in the methylome over its lifespan, making it hard to construct something resembling the epigenetic clocks established for mammals; relating the existence of epigenetic clocks to theories of programmed aging; demonstrating that acccelerated aging correlates with cardiometabolic disease; Olympic medal winners exhibit slower expigenetic aging in comparison to other competitors; a demonstration that more recent epigenetic clocks do correlate with Alzheimer's disease risk.

Articles

Every year I note that I am not writing as much as I used to, or at least not directing said writing in the direction of the Fight Aging! audience as much used to be the case. There are more demands on my time than there used to be, or so it seems. Still, a few items from the past year are noted below.

• Predicting the Order of Arrival of the First Rejuvenation Therapies
• Reporting on a Nine Month Self-Experiment in Taurine Supplementation
• Request for Startups in the Rejuvenation Biotechnology Space, 2024 Edition
• Notes from the Rejuvenation Startup Summit in Berlin, May 2024

At the End, the Wheel Turns

The more involved one is in the field of aging and longevity, the more one feels that the tremendously important work of building therapies to treat aging as a medical condition is crawling along at a very slow pace indeed. But step back, look in only every five years or so, and change is rapid. Progress is made. The wheel turns. It can never be fast enough in a world in which so very many people suffer and die from age-related disease each and every day, but this is a very different environment when compared to the state of affairs twenty years past. The 2040s will be amazing.

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The Integrated Stress Response Marks Dysfunctional Microglia in Alzheimer's Disease
https://www.fightaging.org/archives/2025/01/the-integrated-stress-response-marks-dysfunctional-microglia-in-alzheimers-disease/

Microglia are innate immune cells resident in the brain, analogous in function and behavior to macrophages found elsewhere in the body. They are responsible for clearing debris, aiding in regeneration, destroying pathogens and problem cells, and additionally appear to be involved in maintaining and changing the networks of connections between neurons. An aging brain is characterized by increasing numbers of inflammatory, reactive microglia, representative of the shift to constant inflammatory signaling that takes place throughout the body with advancing age. It is a maladaptive reaction to growing levels of molecular damage, from protein aggregates to mislocalized mitochondrial DNA to the signaling of senescent cells.

Inflammatory microglia are implicated in the development and progression of neurodegenerative conditions. Clearance of microglia, allowing a fresh population to emerge from progenitor cells, appears to improve matters in animal studies of neurodegenerative conditions. Beyond pointing to inflammatory signaling, what exactly are problem microglia doing to provoke neurodegeneration, however? In today's research materials, scientists report the identification of one subset of harmful microglia that are characterized by an active integrated stress response (ISR), leading to secretion of toxic lipids that harm surrounding neurons. In this context, it is worth noting that past animal studies of therapies targeting the ISR have produced interesting results in the context of neurodegeneration.

New Research Identifies Key Cellular Mechanism Driving Alzheimer's Disease

Microglia, often dubbed the brain's first responders, are now recognized as a significant causal cell type in Alzheimer's pathology. However, these cells play a double-edged role: some protect brain health, while others worsen neurodegeneration. Understanding the functional differences between these microglial populations has been a research focus. Researchers have now discovered that activation of a stress pathway known as the integrated stress response (ISR) prompts microglia to produce and release toxic lipids. These lipids damage neurons and oligodendrocyte progenitor cells - two cell types essential for brain function and most impacted in Alzheimer's disease. Blocking this stress response or the lipid synthesis pathway reversed symptoms of Alzheimer's disease in preclinical models.

A neurodegenerative cellular stress response linked to dark microglia and toxic lipid secretion

The brain's primary immune cells, microglia, are a leading causal cell type in Alzheimer's disease (AD). Yet, the mechanisms by which microglia can drive neurodegeneration remain unresolved. Here, we discover that a conserved stress signaling pathway, the integrated stress response (ISR), characterizes a microglia subset with neurodegenerative outcomes. Autonomous activation of ISR in microglia is sufficient to induce early features of the ultrastructurally distinct "dark microglia" linked to pathological synapse loss. In AD models, microglial ISR activation exacerbates neurodegenerative pathologies and synapse loss while its inhibition ameliorates them. Mechanistically, we present evidence that ISR activation promotes the secretion of toxic lipids by microglia, impairing neuron homeostasis and survival in vitro. Accordingly, pharmacological inhibition of ISR or lipid synthesis mitigates synapse loss in AD models. Our results demonstrate that microglial ISR activation represents a neurodegenerative phenotype, which may be sustained, at least in part, by the secretion of toxic lipids.

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Does Low Socioeconomic Status Literally Accelerate Aging?
https://www.fightaging.org/archives/2025/01/does-low-socioeconomic-status-literally-accelerate-aging/

Correlations exist between health, life expectancy, lifestyle choices and the web of connections between intelligence, educational achievement, wealth, and status. Higher socioeconomic status and greater intelligence both correlate with a longer life expectancy, but it remains a challenge to move from correlational data to an understanding of the causes and their relative importance. Is it all down to obesity and exercise? Are there genetic factors that link intelligence and the physical robustness needed for greater longevity? Does wealth buy better access to medicine in ways that matter for life expectancy?

It is interesting to ask whether specific choices or life status factors literally accelerate degenerative aging. In the case of being overweight, there is a body of evidence to suggest that, yes, at least some of the known underlying causes of aging are accelerated. The accumulation of senescent cells, for example. For low socioeconomic status it is a little harder to theorize on why there would be a direct mechanistic link to life expectancy and pace of aging. Given present proxy measures for biological age, the accumulated burden of damage and dysfunction, one can show that biological age proceeds faster in people of low socioeconomic status, but that still leaves open the question of why this is the case.

The Pace of Biological Aging Partially Explains the Relationship Between Socioeconomic Status and Chronic Low Back Pain Outcomes

Socioeconomic status (SES) disparities in healthcare have been well documented for decades and have severe implications. Individuals classified as having a lower SES have a shorter life expectancy and are at increased risk for age-related chronic conditions such as chronic pain. Among individuals with chronic low back pain (cLBP), those with a lower SES have greater pain intensity and pain-related disability. This is relevant because low back pain is a leading cause of years lived with disability. Emerging evidence has linked worse pain outcomes to epigenetically induced alterations in pathways involved in neuroinflammation, hormonal dysregulation, impaired immune function, allostatic loads, and poor metabolic control. Interestingly, these major biological pathways overlap with processes that control aging.

We used the Dunedin Pace of Aging Calculated from the Epigenome (DunedinPACE) software to determine the pace of biological aging in adults ages 18 to 85 years with no cLBP (n = 74), low-impact pain (n = 56), and high-impact pain (n = 77). The mean chronological age of the participants was 40.9 years. On average, the pace of biological aging was 5% faster (DunedinPACE = 1.05 ± 0.14) in the sample. Individuals with higher levels of education had a significantly slower pace of biological aging than those with lower education levels (F = 5.546). After adjusting for sex and race, household income level significantly correlated with the pace of biological aging (r = - 0.17), pain intensity (r = - 0.21), pain interference (r = - 0.21), and physical performance (r = 0.20). In mediation analyses adjusting for sex, race, and body mass index (BMI), the pace of biological aging mediates the relationship between household income (but not education) level and cLBP intensity, interference, as well as physical performance.

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Why Do Oocytes Not Accumulate Mitochondrial DNA Mutations?
https://www.fightaging.org/archives/2025/01/why-do-oocytes-not-accumulate-mitochondrial-dna-mutations/

Mitochondria are the power plants of the cell, vital organelles evolved from symbiotic bacteria that merged with early cellular life to form the first eukaryotes. Every cell contains hundreds of mitochondria, capable of replicating to make up their numbers, as well as fusing together and swapping component parts. Each mitochondrion bears at least one mitochondrial DNA copy, a remnant genome that contains a small number of genes necessary for mitochondrial function. Mitochondrial DNA is more vulnerable to mutational damage and less capable of repair than is the case for DNA in the cell nucleus. It is thought that the accumulation of mitochondrial DNA damage in cells throughout the body contributes to aging via loss of mitochondrial function, but the situation is complicated by selection effects in the mitochondrial population and the operation of mitophagy, a recycling process to clear damaged and dysfunctional mitochondria.

Oocytes are female germline cells, a population that gives rise to egg cells. Oocytes and the cells of their supporting niche have evolved a variety of mechanisms to protect oocyte nuclear DNA from damage; this is fairly well studied. Less well studied is damage that occurs to mitochondrial DNA in oocytes, but it is reasonable to think that oocytes could have evolved the means to minimize mitochondrial DNA damage for all the same reasons that they have evolved ways to better protect nuclear DNA - at least in longer-lived species such as our own. The interesting question is whether any of these evolved mechanisms could usefully be applied to other cells in the body to better maintain their mitochondrial DNA. The first step is to identify these mechanisms, and that is still a work in progress.

Mitochondrial DNA mutations in human oocytes undergo frequency-dependent selection but do not increase with age

Whereas mitochondrial DNA (mtDNA) mutations have been analyzed in human somatic tissues in detail, the direct examination of mtDNA mutations in human oocytes has been challenging due to methodological limitations. Most previous studies either focused on particular mtDNA sites or used sequencing methods with high error rates. Using a low-error duplex sequencing approach, we have recently shown that mutations across the whole mtDNA increase with age in mouse oocytes. Using the same approach, we have demonstrated that mtDNA mutations increase in macaque oocytes until ∼9 years of age and do not increase afterward. Importantly, we still do not know definitively whether the frequency of de novo mtDNA mutations increases with age in human oocytes.

To address this knowledge gap, we analyzed mtDNA substitution mutations in single oocytes, blood, and saliva from women of ages 20 to 42. We used the highly accurate duplex sequencing method, which we had previously modified to generate high-quality mtDNA sequences directly from single oocytes. We obtained a comprehensive set of mutations to study the impact of age on frequencies of germline and somatic mutations, as well as on their distribution across mtDNA.

We found that, with age, mutations increased in blood and saliva but not in oocytes. In oocytes, mutations with high allele frequencies (≥1%) were less prevalent in coding than non-coding regions, whereas mutations with low allele frequencies (less than 1%) were more uniformly distributed along mtDNA, suggesting frequency-dependent purifying selection. In somatic tissues, mutations caused elevated amino acid changes in protein-coding regions, suggesting positive or destructive selection. Thus, mtDNA in human oocytes is protected against accumulation of mutations having functional consequences and with aging. These findings are particularly timely as humans tend to reproduce later in life.

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Developing a Cell Model of Aging-Like Mitochondrial Mutational Damage
https://www.fightaging.org/archives/2024/12/developing-a-cell-model-of-aging-like-mitochondrial-mutational-damage/

Mitochondria are the power plants of the cell, the distant descendants of symbiotic bacteria that carry their own small circular genome, distinct from that of the cell nucleus. The mitochondrial genome is more prone to damage and less well repaired than the nuclear genome, and mitochondrial DNA mutations are thought to be important in aging. Deletion mutations can create broken mitochondria that outcompete undamaged peers to take over a cell, creating a small number of harmfully dysfunctional cells. Less severe point mutations are more commonplace, but evidence is contradictory regarding the degree to which this form of damage contributes to mitochondrial dysfunction in aging. Hence the value of generating a cell model of aging-like mitochondrial damage, to better enable studies of the dysfunction it generates.

The consequences of heteroplasmic mitochondrial mutations have been challenging to study as genome editing for mitochondrial DNA (mtDNA) is limited and there are few established tools to alter heteroplasmy in vitro. Model systems such as the "mtDNA mutator" mouse containing a mutant polymerase gamma implicate mtDNA changes in many aging phenotypes. However, this mouse model induces a large mix of genome alterations often with mtDNA depletion in cells, yielding much more disruption than the clonally expanded heteroplasmic mutation events that occur in usual aging in vivo. Much of our current knowledge regarding heteroplasmy comes from comparisons of primary cells from patients with mtDNA mutations to controls, often with low mutant heteroplasmy and unmatched nuclear genetics, or from immortal "cybrid" cells, which have a malignant pathophysiology and limit the capacity to study the impact of heteroplasmy on cell fate and viability.

Reprogramming somatic cells to pluripotency has been shown to reverse some markers of aging, and expression of reprogramming factors is proposed as a potential rejuvenating therapy. However, the impact of mtDNA heteroplasmy on this process has not been queried. Although heteroplasmy of pathogenic mtDNA variants is typically stable for differentiated cells in culture, multiple recent studies established that heteroplasmy shifts significantly with reprogramming of primary cells to induced pluripotent stem cells (iPSCs). However, beyond this single-measure characterization, the impact of altered heteroplasmy on cell function, and particularly on the capacity for rejuvenation remains unexplored. This is a key area to understand as critical roles are rapidly evolving for mitochondrial metabolism in both maintenance of pluripotency and stem cell differentiation.

We note that the differential segregation of mtDNA heteroplasmy following iPSC generation offers a novel opportunity to understand the impact of clonal increases or decreases in mtDNA heteroplasmy on cellular function. We hypothesize that iPSCs with increased mtDNA heteroplasmy have functional adaptations consistent with cellular aging. Thus, we generated iPSC colonies from three primary fibroblast lines with known heteroplasmy of deleterious mtDNA mutations and quantified heteroplasmy of these mutations in resultant clones. We report that resultant clones displayed a primary bimodal distribution of mutation heteroplasmy. We determined that high-level mtDNA deletion mutant iPSCs exhibit distinct growth properties, metabolic profiles, and altered differentiation capacity, with growth and metabolic shifts mirroring a key subset of changes observed in aging-induced cell and tissue dysfunction.

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Urolithin A Derivatives Targeting Mitophagy in Clinical Trials
https://www.fightaging.org/archives/2024/12/urolithin-a-derivatives-targeting-mitophagy-in-clinical-trials/

While there seems to be no firmly established mechanism by which urolithin A acts to modestly improve mitochondrial function, it seems presumed that this (and a number of other compounds, such as mitoQ) largely function via improving the operation of mitophagy. Mitophagy, mitochondrially targeted autophagy, is a maintenance process that removes damaged and worn mitochondria. Too little of that and the mitochondrial population in a cell become incrementally more dysfunctional. Impaired mitophagy and mitochondrial dysfunction are features of aging, while improved autophagy is a feature of cell stress responses and many interventions known to modestly slow aging in animal studies.

Vandria is one of a number of companies attempting to make therapies for age-related conditions based on novel modifications of established autophagy or mitophagy promoting compounds. Here, Vandria is noted to have started an initial clinical trial for a urolithin A derivative. So far, efforts in this direction have failed to improve on calorie restriction, and only the rapalogs have done better in some aspects than exercise. It remains to be seen as to how this line of work will fare. Certainly, the original urolithin A compound isn't all that impressive in animal studies.

Vandria SA, a company at the vanguard of mitochondrial therapeutics developing first-in-class small molecule mitophagy inducers, today announces that the first subjects have been dosed in its first-in-human clinical trial of its lead Central Nervous System (CNS) compound VNA-318. Readout of this combined single and multiple ascending dose trial is expected in the summer of 2025.

VNA-318 is an orally available first-in-class small molecule against a novel target to rejuvenate cells and treat age-related diseases through the induction of mitophagy. The target has strong genetic links to several human diseases including Alzheimer's disease. It has a dual mode of action with an immediate improvement of memory, learning, and cognitive function, paired with long-term disease-modifying effects such as reduced neuroinflammation, less toxic protein aggregation, and improved mitochondrial function, as shown in pre-clinical models of Alzheimer's and Parkinson's disease. Toxicity studies have demonstrated VNA-318 has a wide safety window. A composition of matter patent covering VNA-318 and other compounds has been issued by the US Patent Office.

This Phase 1 randomized, double-blind trial is a combined single and multiple ascending dose trial of VNA-318, designed to assess safety, tolerability, pharmacokinetic, and pharmacodynamic parameters in healthy male subjects.

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Lithocholic Acid in Calorie Restriction
https://www.fightaging.org/archives/2024/12/lithocholic-acid-in-calorie-restriction/

Researchers here argue for lithocholic acid, a bile acid produced when the gut microbiome processes bile, to be a player in the ability of calorie restriction to slow aging and extend life in short-lived species. Researchers have in the past noted that providing lithocholic acid to yeast slows cell aging, while centenarians exhibit a gut microbiome that produces more lithocholic acid. While reading this, it is worth remembering that while the mechanisms described exist, it is ever challenging to determine how much of the benefits of calorie restriction or an altered gut microbiome derive from pathways involving lithocholic acid. Therapies that target this could be interesting, or could be poor options. It is hard to tell without trying.

Generally speaking, bile is less interesting than is longevity, but that might soon change. Consisting mainly of water, bilirubin (a breakdown product of haemoglobin), cholesterol, and bile acids, this yellow-green fluid is synthesized in the liver, stored in the gallbladder and released into the small intestine to emulsify dietary fats and increase the absorption of fat-soluble vitamins. Gut-resident bacteria, such as species of Clostridium and Lactobacillus, convert primary bile acids into the secondary bile acids deoxycholic acid and LCA, some of which is reabsorbed into the bloodstream.

Previous work has identified bile acids as health-promoting compounds. Dafachronic acids, which are structurally related to LCA, extend the lifespans of nematode worms (Caenorhabditis elegans) and LCA extends the lifespans of yeast (Saccharomyces cerevisiae) and fruit flies. In mammals, LCA is not known to extend lifespan, but it does alter physiology in ways that are consistent with improved health, such as lowering levels of liver triglycerides, blood glucose, and systemic inflammation - in part, by activating the bile-acid receptor TGR5. LCA is also implicated in the lifespan-extending effects of transplanting gut microbiota from young mice into old mice, but how the bile acid might impart health benefits is unclear.

In a recent study researchers gave LCA to old mice for a month. These mice experienced health benefits reminiscent of those induced by calorie restriction, including improved muscle regeneration, grip strength, and sensitivity to insulin. These effects were dependent on AMPK. Interestingly, LCA raised levels of the hormone GLP-1 without causing muscle loss, unlike today's popular weight-loss drugs that bind to the GLP-1 receptor. In nematodes and flies, LCA activated AMPK, increased stress resistance and extended lifespan - benefits that were negated when the gene encoding AMPK was deleted in the animals.

After ruling out TGR5 as the mediator of LCA's effects, the researchers turned their attention to the enzyme SIRT1. They demonstrated that LCA stimulates SIRT1 to upregulate AMPK. The involvement of gut microbiota in the production of LCA and the benefits of calorie restriction might explain why faecal transplants from young animals improve the health and increase the lifespans of older animals, and why some mice do not respond to calorie restriction.

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A CpG Oligodeoxynucleotide Promotes Bone Formation
https://www.fightaging.org/archives/2024/12/a-cpg-oligodeoxynucleotide-promotes-bone-formation/

Bone is constantly remodeled by the activities of osteoclasts and osteoblasts. Osteoclasts break down the extracellular matrix of bone, while osteoblasts create it. These activities are balanced in youth, but with advancing age a range of mechanisms operate to create a growing imbalance favoring osteoclasts. This steadily reduces bone density leading to osteoporosis and eventually life-threatening fracture risk. In principle any compensatory therapy should be beneficial, any way to suppress osteoclast or enhance osteoblast populations and activity regardless of whether or not underlying causes are targeted. In practice, finding good paths forward has been challenging, but researchers here report on their investigation of one potential new approach.

A CpG oligodeoxynucleotide (CpG-ODN), iSN40, was originally identified as promoting the mineralization and differentiation of osteoblasts, independent of Toll-like receptor 9 (TLR9). Since CpG ODNs are often recognized by TLR9 and inhibit osteoclastogenesis, this study investigated the TLR9 dependence and anti-osteoclastogenic effect of iSN40 to validate its potential as an osteoporosis drug.

The murine monocyte/macrophage cell line RAW264.7 was treated with the receptor activator of nuclear factor-κB ligand (RANKL) to induce osteoclast differentiation, then the effect of iSN40 on was quantified by tartrate-resistant acid phosphatase (TRAP) staining and real-time RT-PCR. iSN40 completely inhibited RANKL-induced differentiation into TRAP+ multinucleated osteoclasts by suppressing osteoclastogenic genes and inducing anti-/non-osteoclastogenic genes. Treatment with a TLR9 inhibitor or a mutation in the CpG motif of iSN40 abolished the intracellular uptake and anti-osteoclastogenic effect of iSN40.

These results demonstrate that iSN40 is subcellularly internalized and is recognized by TLR9 via its CpG motif, modulates RANKL-dependent osteoclastogenic gene expression, and ultimately inhibits osteoclastogenesis. Finally, iSN40 was confirmed to inhibit the osteoclastogenesis of RAW264.7 cells cocultured with the murine osteoblast cell line MC3T3-E1, presenting a model of bone remodeling. This study demonstrates that iSN40, which exerts both pro-osteogenic and anti-osteoclastogenic effects, may be a promising nucleic acid drug for osteoporosis.

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Reprogramming Colon Cancer Cells into Normal Cells
https://www.fightaging.org/archives/2025/01/reprogramming-colon-cancer-cells-into-normal-cells/

A cell is just a state machine; control its gene expression, control over the production of proteins, implies control of its behavior and activity. Given sufficient knowledge and ability to make specific changes in gene expression, there is no such thing as an irreversible cell state - except in the case that nuclear DNA damage has removed the ability to express correct proteins, one would think. So while reversing cellular senescence is one thing, it is interesting to find that at least some cancerous cell types can be reverted to essentially normal cells. Is this a safe and useful approach to cancer therapy, or will it just create a sizable population of cells that retain the mutational damage that will predispose them to becoming cancerous again?

Researchers have developed a groundbreaking technology that can treat colon cancer by converting cancer cells into a state resembling normal colon cells without killing them, thus avoiding side effects. The research team focused on the observation that during the oncogenesis process, normal cells regress along their differentiation trajectory. Building on this insight, they developed a technology to create a digital twin of the gene network associated with the differentiation trajectory of normal cells.

Through simulation analysis, the team systematically identified master molecular switches that induce normal cell differentiation. Three genes, HDAC2, FOXA2, and MYB, were discovered as key control factors that induce differentiation of normal colon cells. When these three genes were knocked down the cancer cells reverted to a normal-like state, a result confirmed through molecular and cellular experiments as well as animal studies. This research demonstrates that cancer cell reversion can be systematically achieved by analyzing and utilizing the digital twin of the cancer cell gene network, rather than relying on serendipitous discoveries. The findings hold significant promise for developing reversible cancer therapies that can be applied to various types of cancer.

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Extracellular Vesicle Therapy as a Treatment for Osteoarthritis
https://www.fightaging.org/archives/2025/01/extracellular-vesicle-therapy-as-a-treatment-for-osteoarthritis/

The clinical community practicing first generation stem cell therapies is slowly shifting away from cell transplants towards harvesting extracellular vesicles from cell in culture and transplanting the vesicles instead. In most cases near all transplanted stem cells die, and that the majority of the effects of such therapies in age-related disease - largely reliable suppression of chronic inflammation rather than improved regeneration of tissues - are mediated by the signaling produced by those cells in the short time that they survive in the recipient. Much of cell signaling is carried within vesicles, and to date the evidence suggests that vesicle therapies produce similar results to stem cell therapies, while being an easier proposition from the logistics perspective.

Age is the most important risk factor for degenerative diseases such as osteoarthritis (OA). It is associated with the accumulation of senescent cells in joint tissues that contribute to the pathogenesis of OA, in particular through the release of senescence-associated secretory phenotype (SASP) factors. Mesenchymal stromal cells (MSCs) and their derived extracellular vesicles (EVs) are promising treatments for OA. However, the senoprotective effects of MSC-derived EVs in OA have been poorly investigated.

Here, we used EVs from human adipose tissue-derived MSCs (ASC-EVs) in two models of inflammaging (IL1β)- and DNA damage (etoposide)-induced senescence in OA chondrocytes. We showed that the addition of ASC-EVs was effective in reducing senescence parameters, including the number of SA-β-Gal-positive cells, the accumulation of γH2AX foci in nuclei and the secretion of SASP factors. In addition, ASC-EVs demonstrated therapeutic efficacy when injected into a murine model of OA. Several markers of senescence, inflammation, and oxidative stress were decreased shortly after injection likely explaining the therapeutic efficacy. In conclusion, ASC-EVs exert a senoprotective function both in vitro, in two models of induced senescence in OA chondrocytes and, in vivo, in the murine model of collagenase-induced OA.

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More Whales May be Long Lived than Previously Suspected
https://www.fightaging.org/archives/2025/01/more-whales-may-be-long-lived-than-previously-suspected/

A better understanding of the biochemistry of long-lived, large species may in the near term lead to ways to better prevent cancer: more cells means more cancer risk, so every species larger and more long-lived than humans must have evolved better than human cancer suppression mechanisms. Elephants evolved many copies of tumor suppressor TP53, for example, while some whales appear to make use of other mechanisms to maintain cancer risk at a low enough level to ensure long lives and evolutionary success. That said, as for all of areas of interest arising from studies of the comparative biology of aging, it remains unclear as to the practical costs and feasibility of adapting cellular mechanisms from species A for use in species B. On a case by case basis this may be a prospect for the next twenty years, or it could require a century or more of progress towards reliable engineering of the human genome and cell biochemistry.

The first observations documenting the extraordinary longevity of whales were from the counts of annual ear plug lamina of fin whales (Balaenoptera physalus) and blue whales (Balaenoptera musculus) taken by Japanese whalers. Although most individuals had fewer than 20 lamina, a few specimens had more than 100 annual growth layers. From these data, the oldest blue and fin whales were documented to be at least 110 and 114 years, respectively. At the time, these were the oldest documented nonhuman mammals. Corroborating these ages is more recent evidence of great longevity in bowhead whales (Balaena mysticetus). Archaeological artifacts recovered from the blubber of bowheads taken in the modern Indigenous subsistence hunt include several stone or metal and ivory harpoon points last used in the 1880s. In 2007, a whale was taken in the traditional hunt and found to have an explosive Yankee Whaler harpoon tip embedded in its blubber last manufactured in 1885. These artifacts suggested that bowhead whales lived at least 130 years.

After the recovery of these artifacts, researchers used aspartic acid racemization (AAR) of the eye lens and then a new aging method to estimate the ages of whales taken in the subsistence hunt. In one instance, an individual's AAR-estimated age of 133 years corresponded closely to the 120-year-old whaling artifact recovered from its blubber, validating extraordinary AAR-estimated ages. AAR estimated ages of several individuals exceeded 150 years, and one individual, otherwise healthy, was estimated to be 211 years old. This was older than the documented ages of fin and blue whales by a century and would have likely been considered a laboratory error in the absence of the corroborating archaeological evidence.

From the standpoint of physiological scaling, these superannuated ages should not be unexpected. Whales are the largest living animals, and body size is highly correlated with longevity. There are three confounding issues in current whale age estimation, and all likely result in considerable downward bias on expected life span at the species level. First, although most toothed whales and some baleen whales have tissues with countable annular growth layers, many do not or, if they do, the archives are incomplete or difficult to count in very old individuals because of tissue remodeling, tooth wear, and/or thinning of the oldest annual layers. Second, it is unclear whether we could detect superannuated individuals in most whale populations today. Industrial whaling, which for most species ended only 60 years ago, would have required any individuals now aged over 100 years to have survived at least 40 years of intense whaling, and any individual over 150 would have had to survive 90 years of that same intense hunt. Last and closely related to the previous point, most methods of aging whales require lethal sampling.

Most whale populations have recovered or are recovering from industrial whaling, and although the populations are healthy, they have been growing for the past 60 years and are thus composed almost exclusively of individuals born after 1965. To detect very old individuals today using laminated tissues, AAR, or new molecular clock aging methods would still require an extremely large sample size before detecting a single superannuated individual. Consequently, we believe that it is reasonable to hypothesize that now estimated baleen whale life spans are biased low.

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Brown Adipose Tissue is Beneficial to Metabolism and Improves Exercise Performance
https://www.fightaging.org/archives/2025/01/brown-adipose-tissue-is-beneficial-to-metabolism-and-improves-exercise-performance/

There is a fair amount of literature on the benefits of brown adipose tissue, involved in thermogenesis, weight loss mechanisms, and most likely a variety of forms of beneficial metabolic signaling. Some interventions known to improve long-term health may act in part by converting a fraction of white adipose tissue to brown adipose tissue. Here, researchers use the blunt but useful approach of transplanting brown fat tissue between mice to observe the outcome, demonstrating that the addition of more brown fat appears beneficial to measures of health.

Brown adipose tissue (BAT), a major subtypes of adipose tissues, is known for thermogenesis and promoting healthful longevity. Our hypothesis is that BAT protects against impaired healthful longevity, i.e., obesity, diabetes, cardiovascular disorders, cancer, Alzheimer's disease, and reduced exercise tolerance. While most prior studies have shown that exercise regulates BAT activation and improves BAT density, relatively few have shown that BAT increases exercise performance. In contrast, our recent studies with the regulator of G protein signaling 14 (RGS14) knockout (KO) model of extended longevity showed that it enhances exercise performance, mediated by its more potent BAT, compared with BAT from wild type mice.

Multiple mechanisms mediated the enhanced exercise capacity in RGS14 KO mice. The most important mechanism is BAT, which mediates SIRT3, MnSOD, MEK/ERK and VEGF pathways. These mechanisms regulate exercise capacity by improved mitochondrial function, protection against oxidative stress, and improved blood flow/angiogenesis. For example, when the BAT from RGS14 KO mice is transplanted to WT mice, their exercise capacity is enhanced at 3 days after BAT transplantation, whereas BAT transplantation from WT to WT mice increased exercise performance, but only at 8 weeks after transplantation. In view of the ability of BAT to mediate healthful longevity and enhance exercise performance, it is likely that a pharmaceutical analog of BAT will become a novel therapeutic modality.

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Reviewing What is Known of Age-Related Changes in Transcriptional Elongation
https://www.fightaging.org/archives/2025/01/reviewing-what-is-known-of-age-related-changes-in-transcriptional-elongation/

Transcriptional elongation is the name given to the complex process by which nucleotides are added to the end of an RNA molecule as it is being constructed in the cell nucleus, replicating the blueprint for that molecule encoded in a DNA sequence. The RNA polymerase II complex is the protein machinery that accomplishes this work. In recent years researchers have identified age-related changes in the operation of this machinery that give rise to a greater incidence of errors and other changes in gene expression thought to detrimentally alter cell behavior.

Aging results in a major impairment of RNA and protein biosynthesis that contributes to aging-associated phenotypes. Research over the past two decades has mostly focused on quantitative changes of RNA and protein levels. However, recent work has shown that the quality of molecular processes involved in RNA and protein biosynthesis also declines with age, impacting not only the quantity but critically also the quality of the synthesized molecules. For example, errors during transcription and splicing can result in mRNAs carrying incorrect primary sequences, which can in turn lead to the production of toxic proteins that fuel aging-associated disease. Indeed, recent unbiased screens for factors causal to age-dependent retinal degeneration in flies or for new senescence regulators, identified transcriptional initiation and elongation factors as among the top hits.

It remains largely elusive how individual processes are affected during aging and what their specific contribution to age-related functional decline is. This review discusses a series of recent publications that has shown that transcription elongation is compromised during aging due to increasing DNA damage, stalling of RNA polymerase II, erroneous transcription initiation in gene bodies, and accelerated RNA polymerase II elongation. Importantly, several of these perturbations likely arise from changes in chromatin organization with age. Thus, taken together, this work establishes a network of interlinked processes contributing to age-related decline in the quantity and quality of RNA production.

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Assessing Mitochondrial Decline with Age Using Frozen Tissue Samples
https://www.fightaging.org/archives/2025/01/assessing-mitochondrial-decline-with-age-using-frozen-tissue-samples/

It is almost always the case that measurement in biology is not as straightforward as the high level summaries make it out to be, and there is almost always some debate over whether the measurements are good enough, robust enough, and actually correct. Mitochondria are the power plants of the cell, conducting energetic reactions to produce the chemical energy store molecule adenosine triphosphate (ATP) needed to power the the cell. It is well established that mitochondrial function declines with age, but until quite recently measuring mitochondrial function required live mitochondria, which opened up all sorts of opportunities for cost, rework, bias, and error in the process of getting those mitochondria out of an animal (or person) and into a device in large enough numbers and good enough condition. Now, however a robust method for assessment in frozen samples exists, and researchers are putting it to good use, to double-check the present consensus on age-related mitochondrial decline.

It is generally accepted that mitochondria become less active in aging animals and that their dysfunction is a key contributor to the aging process. A device called a 'respirometer' can be used to measure mitochondrial activity by detecting how much oxygen these organelles are consuming. However, until recently, this approach could only be applied to freshly isolated mitochondria obtained from mammalian tissues through a long and laborious process, making them difficult to study in large numbers. This limitation has prevented comprehensive analyses of mitochondrial respiration in mammalian tissues.

Using a recently developed protocol for respiratory analysis of frozen tissue samples researchers have now measured a proxy of mitochondrial respiration in over 1,000 samples from a large cohort of young and old mice of both sexes. This included tissues with reportedly high mitochondrial activity, such as certain brain regions, several skeletal muscles, the heart, and the kidneys. The samples also included metabolic tissues like the liver or pancreas, as well as sections of the gastrointestinal tract, the skin, and the eyes.

Due to the process of freezing and thawing, the mitochondria in the samples were not intact and therefore could not be isolated. Researchers measured mitochondrial respiration at three different sites on the electron transport chain in cellular extracts enriched with mitochondrial membranes. The proteins making up this chain are likely to remain relatively stable in mitochondria whose membrane integrity has been lost, which allows measurements that indicate the maximum capacity of the mitochondria to produce ATP to be taken.

Analyzing the differences between old and young animals revealed a net decline in mitochondrial activity in most tissues with age, most notably in samples from the brain and metabolic tissues. These results are consistent with our current understanding of the energetic demands of various tissues and how they decline over time. Intriguingly, in older animals, respiration increased in some tissues with high-energy demand, such as the heart and skeletal muscles, which is potentially at odds with the observation that these organs perform less well with age. Analyzing differences between samples from males and females also revealed that age has a much larger effect on mitochondrial activity across all tissues than sex.

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