Fight Aging!

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Contents

• Wanted: A Non-Profit to Run as Many Low-Cost Trials of Promising Treatments for Aging as Possible
• Dysfunctional Mitophagy in the Aging Brain
• Cellular Senescence Promotes Metabolic Dysfunction, in Turn Promoting Cellular Senescence
• The Cellular Senescence Network (SenNet) Program
• MicroRNA-181b in Age-Related Arterial Stiffness
• Analysis of Human Mortality Data at Extreme Old Age from the International Database on Longevity
• Extracellular Vesicles in Aging and Rejuvenation
• The U-Shaped Association Between Physical Activity and Cardiovascular Mortality
• How Much of the Benefit of Calorie Restriction in Mice is Due to Incidental Fasting?
• Suggesting that Viral Infection Can Promote the Spread of Protein Aggregates in the Brain
• Journalistic Balance Run Amok in the Matter of Aging
• Organoids in the Study of Aging
• Animal Size and Force on Cells in the Evolution of Proficient Regeneration
• Calorie Restriction Mimetics in the Context of Cardiovascular Disease
• Fat Cells in Cognitive Decline and Neurodegeneration

Wanted: A Non-Profit to Run as Many Low-Cost Trials of Promising Treatments for Aging as Possible
https://www.fightaging.org/archives/2021/10/wanted-a-non-profit-to-run-as-many-low-cost-trials-of-promising-treatments-for-aging-as-possible/

A major gap exists in the present spectrum of efforts to develop the means to treat aging, rejuvenate the old, and turn back age-related conditions. An the one hand, a small number of promising potential therapies to treat the mechanisms of aging can at present be applied by physicians off-label, or otherwise without the need for a great deal of interaction with the FDA. On the other hand, there are a good hundred or more clinical indications, specific age-related conditions recognized by regulatory authorities, that might be improved by these therapies. Several hundred small, informal trials could be run, starting now, given approaches that presently exist, in order to determine whether or not these forms of therapy are in fact effective.

Let us only consider the senolytic combination of dasatinib and quercetin, for example, a low-cost treatment that can be given off-label and that has been demonstrated to clear senescent cells in human patients. Clearance of senescent cells in mice produces profound and rapid rejuvenation. Senolytics as a class of therapy are at present in human trials for only a few indications: osteoarthritis, idiopathic pulmonary fibrosis, COVID-19, chronic kidney disease, and recently Alzheimer's disease. The whole senolytic industry, and associated academic trial groups, after nearly ten years of development, has done no more than initiate a few formal human trials, at great expense, and which are very slow to answer the question of whether this actually works well. Senescent cells are involved in some way in near every age-related condition, disrupting tissue function throughout the body, provoking chronic inflammation. Effects on the full panoply of age-related conditions could be assessed. This is not being done.

If considering small informal trials, let us say that one aims for 100 to 200 people per trial, more than enough to produce meaningful evidence for efficacy when the effect size is significant. With volunteer efforts, cheap off-label treatments and low-cost assays for suitable endpoints, this sort of informal trial can be conducted for 200,000 - which is exactly what Lifespan.io is doing for their PEARL trial of mTOR inhibition. The model works. Even if the cost were 500,000 or 1,000,000, then that would still be vastly cheaper than the full, formal FDA IND process. A single non-profit with significant funding could run many such trials in a year, generating human evidence at a much greater rate than the scientific community and biotech industry combined are managing at the moment.

That evidence is much needed. There is an enormous amount of funding sitting on the sidelines. Funding that could be supporting the deployment of senolytic drugs to the population, or could be running large-scale formal clinical trials to validate the use of senolytics. The organizations capable of deploying that funding are very conservative. They will only start in on such project after there is already proof, after the debate is already won. Which is why we need the results of many low-cost trials - in order demonstrate that dasatinib and quercetin is a meaningful and useful approach to the treatment of aging.

Everything said above about the dasatinib and quercetin senolytic combination also applies to, say: fecal microbiota transplantation; or periodic blood plasma dilution; or the Khavinson peptides for thymic regrowth; or the Intervene Immune approach to thymic regrowth; or CASIN for CDC42 inhibition and restored immune function; or injection of stem cell derived exosomes; and forth into a growing list of approaches that may well be capable of achieving good results in old people. Many of these are already being used by self-experimenters, but that will never generate the sort of data that is convincing to the powers that be. There is tremendous potential to demonstrate benefits in older individuals via addressing one or more of the underlying mechanisms of aging, and the world is instead largely squandering time as the clock keeps on ticking on all of our lives.

Dysfunctional Mitophagy in the Aging Brain
https://www.fightaging.org/archives/2021/10/dysfunctional-mitophagy-in-the-aging-brain/

Every cell in the body contains hundreds of mitochondria, the evolved descendants of ancient symbiotic bacteria. Their primary purpose is to produce adenosine triphosphate (ATP), an energy store molecule used to power cellular operations. They are also involved in a great many other aspects of cell function, however. Mitochondria are dynamic organelles, capable of fusing together, passing component parts between one another, and replicating like bacteria. A cell regulates mitochondrial function in part through mitophagy, an autophagy process that breaks down and recycles mitochondria when they become worn and damaged.

Mitochondrial function is understandably vital to cell function. With age, however, mitochondria change and falter. Their dynamics alter, making it harder for mitophagy to function correctly, and components of the broader autophagic process themselves exhibit dysfunction. The result is an accumulation of broken, malfunctioning mitochondria. An alternative, less common path is the generation of mutations in mitochondrial DNA that both cause dysfunction and protect the broken mitochondria from mitophagy, allowing them to take over a cell via replication.

Cells containing dysfunctional mitochondria behave poorly. Organ function suffers as a consequence. This is one of the noteworthy contributing causes of degenerative aging, though it is likely that most mitochondrial dysfunction is downstream of underlying issues that cause alterations in the expression of proteins necessary to mitophagy or mitochondrial dynamics. The brain is an interesting mix of mitochondrial issues, as it is both energy-hungry, and thus sensitive to disruption of mitochondrial function, and contains a great many long-lived cells, in which the progressive age-related failure of mitophagy likely has a different balance of causes in comparison to to those of short-lived cells.

What can an individual do about the challenge of mitochondrial dysfunction in aging? Presently not a great deal. The only available approaches to improved mitophagy, such as NAD upregulation, tend to replicate a thin slice of the benefits produced by exercise. Calorie restriction slows the progression of all aspects of aging, mitochondrial function included, but only to a modest degree in humans. More promising classes of therapy that may be capable of producing meaningful degrees of rejuvenation, such as gene therapies to copy mitochondrial genes into the cell nucleus, or transplantation of functional mitochondria in large numbers, are being worked on, but clinical availability remains years in the future.

Impaired Mitophagy in Neurons and Glial Cells during Aging and Age-Related Disorders

Aging is accompanied by a decline in cognitive function in a significant part of the population and is a major risk factor for the development of most neurodegenerative diseases, including Alzheimer's disease (AD) and Parkinson's disease (PD). Mechanisms of brain aging remain poorly understood, and studies aimed at the development of targeted therapy for neurodegenerative diseases are an important task for modern medicine.

Over the past few decades, it has been shown that aging processes in the brain are closely associated with mitochondrial dysfunction, resulting in oxidative stress and bioenergetic deficiency in various cells of the nervous tissue, which are extremely sensitive to energy deprivation. Mitochondrial dysfunction is also a key pathological marker for neurodegenerative diseases. For example, it is a central player in sporadic and familial forms of PD, since dopaminergic neurons of the substantia nigra are especially vulnerable to energy deficiency due to their ability for autonomous activity, constant recirculation of synaptic vesicles, and developed axonal network. Therefore, maintaining adequate energy levels through a functional pool of mitochondria is critical for neuron survival and function.

The main mechanism that prevents the development of mitochondrial dysfunction is mitophagy. Mitophagy is a complex multicomponent process that ensures control of the quality and quantity of mitochondria by eliminating damaged forms of these organelles via autophagy. The importance of mitophagy for neurons may be explained by the significant role of the cytoplasmic renewal system for postmitotic cell populations. Maintaining the basal level of mitophagy is critical for ensuring the correct functioning of neurites since the bulk of mitochondria are localized in the distal parts of neuronal processes. Mitophagy restricts the production of reactive oxygen species, prevents the accumulation of mitochondrial DNA (mtDNA) mutations and the decrease in ATP production, and blocks apoptotic signaling and the activation of inflammasomes. It is the progressive decline in this type of selective macroautophagy throughout life that appears to lead to mitochondrial dysfunction and aging.

Many neurodegenerative diseases are characterized by the accumulation of neurotoxic protein aggregates resulting from mutations in the genes encoding for proteins that trigger mitophagy: PTEN-induced kinase 1 (PINK1), parkin, and protein deglycase DJ-1, among others. Therefore, determination of the relationships between mitophagy markers and various parameters of neurodegenerative processes in PD, AD, and other age-related disorders seems to be highly promising from both a clinical and fundamental point of view.

In conclusion, mitophagy pathways play an important role in maintaining physiological homeostasis, are involved in the mechanisms of aging and neurodegenerative disorders, and represent promising targets for the development of potential therapeutic agents aimed at regulating mitochondria quality control in neurons and glial cells. A significant number of molecules that induce or inhibit mitophagy are currently under consideration, which may be useful for testing hypotheses or developing drugs for the treatment of neurodegenerative diseases. The validation of promising drugs in animal and cell models, including neurons and glial cells derived from human iPSCs as well as the elucidation of mitophagy regulation mechanisms in human samples, requires reliable biomarkers.

Currently, specific biomarkers that reflect the activity of mitophagy include ubiquitin phosphorylated at serine 65, phosphorylated PINK1 and parkin, the expression and phosphorylation of several proteins of the outer mitochondrial membrane, in addition to general biomarkers of oxidative stress and neuroinflammation. At the same time, given the variety of the regulatory pathways of mitophagy, there is no doubt that this list will be expanded, eventually including indicators that reflect the state of mitophagy in certain types of cells of the nervous tissue.

Cellular Senescence Promotes Metabolic Dysfunction, in Turn Promoting Cellular Senescence
https://www.fightaging.org/archives/2021/10/cellular-senescence-promotes-metabolic-dysfunction-in-turn-promoting-cellular-senescence/

Aging is built on feedback loops, interactions between damage and dysfunction in which both sides accelerate the other. This is a feature of all complex systems, not just biological ones. The existence of feedback loops in which damage accumulation causes dysfunction that accelerates damage accumulation is the fundamental reason as to why aging is an accelerating process. It starts slowly, and moves ever more rapidly with time. Aging in one's 30s is a very different beast to aging in one's 70s, and the downhill slide is much faster in later life.

The way to break this cycle is to repair the damage. This is true whether we are talking about a manufactured machine or a living being: repair is the only viable road to rejuvenation. All other options perform poorly. If you want to engage in a costly struggle, try to keep a damaged machine running without repairing the causes of its dysfunction. That is the story of most present day medicine for age-related disease, unfortunately. It is compensatory in nature and fails to address the causes of disease, the processes of aging itself.

Yet times are changing, and there is a far greater acceptance now for scientific and medical development initiatives that seek to address the damage that causes aging, such as the accumulation of senescent cells that actively disrupt tissue function and promote chronic inflammation. To the degree that these initiatives succeed, we will all have the opportunity to live significantly longer, better lives, spending a greater number of years in vigorous, youthful health.

The metabolic roots of senescence: mechanisms and opportunities for intervention

The senescence response can be beneficial or deleterious, depending on the physiological context. This dualism is consistent with the evolutionary theory of antagonistic pleiotropy. Antagonistic pleiotropy postulates that traits selected to ensure the survival of young organisms in natural environments, in which life spans are short, can become deleterious in modern protected environments, in which life spans are significantly longer. Thus, aging is likely a consequence of the declining force of natural selection with age.

With regard to the beneficial effects of cellular senescence, the senescence growth arrest protects young organisms from developing cancer. In addition, senescence-associated secretory phenotype (SASP) factors can optimize the morphogenesis of certain structures in the embryo, and initiate parturition in the placenta. Finally, senescent cells occur transiently at sites of tissue damage where they contribute to wound healing, tissue repair and regeneration, most likely through specific SASP factors.

In contrast, senescent cells increase with age in most mammalian tissues, where they appear to persist. Whether this increase is due to increased production or decreased clearance, for example by the immune system, is unclear. More importantly, experiments using human cells and tissues, transgenic mouse models, and pharmacological interventions in cells and mice strongly implicate senescent cells in a large number of age-related pathologies, ranging from neurodegeneration to, ironically, age-related cancer. Most of the detrimental effects of senescent cells can be attributed to the SASP, which is rich in pro-inflammatory molecules.

A growing body of literature indicates that both senescence and the SASP are sensitive to cellular and organismal metabolic states, which in turn can drive phenotypes associated with metabolic dysfunction. Here, we review the current literature linking senescence and metabolism, with an eye toward findings at the cellular level, including both metabolic inducers of senescence and alterations in cellular metabolism associated with senescence.

There are three types of interventions that target senescent cells and their degenerative pathologies. First, we can slow the formation of senescent cells, as observed during dietary restriction and similar interventions. Second, we can allow senescent cells to accumulate, but prevent them from causing harm, as observed during metformin-mediated SASP suppression or after CD38 inhibition. Finally, we can use senolysis to remove senescent cells. Unlike the first two interventions, senolysis can be used intermittently - allowing for a 'hit and run' approach that might be easier to implement in humans - whereas dietary and suppressive drug regimens require regular adherence to maintain benefits. We conclude that the most effective interventions will likely break a degenerative feedback cycle by which cellular senescence promotes metabolic diseases, which in turn promote senescence.

The Cellular Senescence Network (SenNet) Program
https://www.fightaging.org/archives/2021/10/the-cellular-senescence-network-sennet-program/

Larger institutions such as the NIH are now beginning to invest a great deal more into fundamental research connected to cellular senescence. Twenty years ago it was clear enough that senescent cells were important in aging for the Strategies for Engineered Negligible Senescence (SENS) pioneers to include it in their initial scientific paper, but the topic was largely ignored by the mainstream of aging research. It took a decade to get to the point of a compelling animal study of targeted senescent cell clearance that convinced the rest of the research community. Five years after that the first senolytic-focused biotech companies were established, working on therapies to selectively destroy senescent cells. A further five years after that we come to this present moment, at which large institutional funding programs get underway to expand the basic science.

Early senolytic therapies are impressive in terms of the results they produce in mice: rapid rejuvenation, extension of life span, reversal of many age-related conditions. These approaches appear to top out at removing about half of the burden of senescent cells in some of the aged tissues assessed. There is definitely room for improvement. The primary concern in the scientific community is not efficacy of therapies, however, but rather the question of how senescent cells might have meaningful differences from tissue to tissue, or by cause of senescence, or other factors. Additionally, are existing means of determining the burden of senescent cells in tissue actually measuring all senescent cells, and are they mistakenly identifying any populations of non-senescent cells that happen to employ some of the same biochemistry?

This work will likely have little influence over the course of the present senolytics industry, the fair number of startup biotechnology companies and established pharma entities attempting to bring the first rejuvenation therapies to the clinic. Some of those first generation senolytics look very promising, such as prodrug approaches to limiting chemotherapeutics to activate only in senescent cells. It will, however, inform the next generation of anti-senescence therapies, which we should expect to be somewhat more effective as as consequence.

NIH launches program to map a rare type of non-dividing cells implicated in human health and disease

The National Institutes of Health has launched a program to study a rare type of cells, called "senescent" cells, that play both positive and negative roles in biological processes. The NIH Common Fund's Cellular Senescence Network (SenNet) program will leverage recent advances in studying individual cells, or single-cell analysis, to comprehensively identify and characterize the differences in senescent cells across the body, across various states of human health, and across the lifespan. The rarity and diversity of these cells previously made them difficult to identify and study; therefore, a deeper understanding will help researchers develop therapies that encourage beneficial effects of senescent cells while suppressing their tissue-damaging effects.

NIH is funding 125 million to 16 grants over five years, pending available funds. NIH issued eight awards for the creation of SenNet Tissue Mapping Centers, seven awards for Technology Development and Application Projects, and one award for a Consortium Organization and Data Coordinating Center (CODCC). The Tissue Mapping Centers will identify biomarkers of senescent cells in humans and then construct high-resolution, detailed maps of cellular senescence across the lifespan and physiological states. The Technology Development and Application Projects will be critical in advancing promising tools, techniques, and methods for SenNet to study senescent cells. As the organizational hub, the CODCC will collect, store, and curate the Network's data, tools, and models. These projects will work together to create a publicly accessible and searchable Atlas of Cellular Senescence.

Cellular Senescence Network (SenNet)

One cell dividing into two is a hallmark of development in living beings. However, as we age the tissues in our body accumulate a small number of specialized cells that no longer divide. These cells are called senescent cells, and they play important roles in health and disease across the lifespan. Under certain circumstances, such as aging, senescent cells accumulate and release a collection of molecules that can cause damage to nearby tissue. Under other conditions, such as cancer or wound healing, senescent cells can protect health by preventing tumor growth or releasing molecules that promote the growth of new tissue. Biomedical researchers still have many unanswered questions about how, when, why, and where senescent cells form, but their rarity and diversity make them difficult to identify and characterize in the body. Despite this, senescence is an attractive target for new therapeutics, with some already in development. A deeper understanding of cellular senescence will help researchers to develop further therapies that encourage beneficial effects of senescent cells while suppressing their tissue-damaging effects.

The Common Fund's Cellular Senescence Network (SenNet) Program was established to comprehensively identify and characterize the differences in senescent cells across the body, across various states of human health, and across the lifespan. SenNet will provide publicly accessible atlases of senescent cells, the differences among them, and the molecules they secrete, using data collected from multiple human and model organism tissues. To identify and characterize these rare cells, SenNet will develop innovative tools and technologies that build upon previous advances in single cell analysis, such as those from the Common Fund's Human Biomolecular Atlas Program and Single Cell Analysis Program. Lastly, SenNet aims to unite cellular senescence researchers by developing common terms and classifications for senescent cells.

MicroRNA-181b in Age-Related Arterial Stiffness
https://www.fightaging.org/archives/2021/10/microrna-181b-in-age-related-arterial-stiffness/

Today's open access paper is a discussion of microRNA regulation of cell behavior in the context of age-related arterial stiffness. The stiffening of blood vessels with age is an important issue, as it produces hypertension via disruption of the feedback mechanisms that control blood pressure. The raised blood pressure of hypertension causes structural damage throughout the body, increasing mortality and accelerating progression of age-related disease.

Every distinct form of organ or tissue dysfunction in aging is made of up many layers. At the base are fundamental causes, forms of damage that arise from the normal operation of metabolism and have no deeper origin. In the case of arterial stiffness that includes loss of elastin and persistent cross-links in the extracellular matrix, both of which reduce the elasticity of blood vessel wall tissues. Some of us tend to put senescent cell accumulation in that layer as well, though the growing number of senescent cells with age is likely to be largely a result of immune system aging. The pro-inflammatory signaling of senescent cells is implicated in smooth muscle dysfunction in blood vessel walls.

These forms of damage feed into the next layer of tissue dysfunction, in which regulatory systems that control gene expression change in response to that damage. These include microRNAs, transcription factors, and other mechanisms involved in the control of the expression of networks of genes in the cell. Some responses are adaptive and some are maladaptive. Altered regulation then produces the uppermost layer of tissue dysfunction, consisting of broad and problematic changes in cell behavior and cell signaling, driven by alterations in protein abundance within the cell and changes in the environment of signals that pass between cells. The vast majority of research into aging and age-related disease focuses on these upper layers: gene expression and its regulation in the aged tissue environment. All too little work is focused on deeper causes.

Deciphering the Role of microRNAs in Large-Artery Stiffness Associated With Aging: Focus on miR-181b

Large artery stiffness (LAS) is a major, independent risk factor underlying cardiovascular disease that increases with aging. Arterial stiffness is determined by the composition and organization of the extracellular matrix, as well as the cytoskeletal properties of vascular smooth muscle cells. Therefore, investigators have concentrated on defining the biochemical and associated structural changes responsible for increased arterial stiffness, as well as the upstream regulatory pathways driving these changes. From this perspective, the microRNA system has emerged as a potential culprit, since this highly versatile signaling pathway can coordinate cellular adaptations in response to developmental and environmental signals and has been found to play key roles in vascular smooth muscle development and function. However, since each cell contains hundreds of distinct microRNAs, and these microRNA profiles differ across cell types, identifying candidate microRNAs involved in regulating arterial stiffness poses a difficult challenge.

Initial clues implicating dysregulation of specific microRNAs in LAS emerged from two approaches. As patients with LAS can be identified by measuring pulse wave velocity (PWV) using non-invasive techniques, investigators looked for alterations in microRNA signaling associated with elevated PWV. This approach yielded identification of two microRNAs linked to elevated PWV: miR-765 and miR-1185. The second approach was based on the epidemiological observation that the prevalence of LAS increases markedly with aging. Furthermore, mice also display aging-associated increases in PWV that model LAS. Thus, investigators checked for microRNAs that show altered expression with aging in blood samples from humans and in mouse aorta. This approach led to the identification of several candidate microRNAs that show altered expression with aging: mir-29, miR-34a, miR-92a, miR-137, miR-181b, miR-203, and miR-222. Mir-29, miR-34a, miR-137, miR-203, and miR-222 increase with aging in mouse aorta and miR-34a has been shown, very recently, to be associated, along with miR-34c, with aortic stiffening in human subjects. Conversely, miR-92a and miR-181b decrease in mouse aorta with aging and miR-92a is also decreased in human blood with aging.

Based on these initial observations, investigators examined whether mimicking these changes is sufficient to produce stiffening. Using a transfection-based approach in vivo, it was found that elevating miR-203 leads to arterial stiffening. Furthermore, administering an antagonist of miR-92a to mice increases PWV. To examine the effect of decreased miR-181b on aortic stiffness, researchers used mice carrying a deletion of the locus (miR-181a1/b1) that blocks expression of both miR-181a and miR-181b in aorta. These mice showed a premature onset of arterial stiffness as young adults. Thus, these findings indicate that aging-associated changes in expression of these candidate microRNAs play a causal role in eliciting arterial stiffness.

Although several studies have demonstrated that mimicking the alteration of a candidate microRNA is sufficient to elicit arterial stiffness, to our knowledge, miR-181b is the only candidate microRNA for which interventions have reduced arterial stiffness. Our strategy for normalizing miR-181b levels in aorta emerged from our observation that this microRNA is one of those elevated in a cell line that had been subjected to knockdown of the translin (TN)/trax (TX) microRNA-degrading enzyme, suggesting that it was targeted by this enzyme. We reasoned that if a decrease in miR-181b levels plays a key role in driving LAS, then TN knockout (KO) mice might be resistant to developing arterial stiffness. As C57BL6 mice display aging-associated arterial stiffening, they provide a suitable animal model of this disorder. However, since that would require waiting until the mice are close to 18 months old, we first tested this hypothesis in a paradigm that elicits increased aortic stiffness in just a few weeks. In this streamlined paradigm, mice are switched from regular water to high salt water (HSW; 4% w/v), and their PWV measured on a weekly basis. Remarkably, we found that TN KO mice are resistant to developing increased PWV induced by this paradigm. Furthermore, exposure to HSW decreases levels of miR-181b in WT mice, but not in TN KO mice, consistent with the view that TN deletion confers protection from increased stiffness by blocking degradation of miR-181b.

As inhibiting the activity of the TN/TX microRNA-degrading enzyme confers protection from the development of aging-associated arterial stiffening, inhibitors of this enzyme may have translational potential. However, since the observed protection occurred in mice with a constitutive inactivation of TN/TX, it will be important to check if inhibition of this enzyme after the initial onset of aging-associated arterial stiffening can prevent the progression or even reverse this process. In addition, as TN/TX inhibition may also elevate other microRNAs, it might be more advantageous to explore other strategies to increase miR-181b levels selectively. However, since extremely high elevations of miR-181b have been implicated in the development of atherosclerotic plaques, it may be important to identify strategies that reverse the age-associated decline in miR-181b levels without elevating them further into the range associated with pathological effects.

Analysis of Human Mortality Data at Extreme Old Age from the International Database on Longevity
https://www.fightaging.org/archives/2021/10/analysis-of-human-mortality-data-at-extreme-old-age-from-the-international-database-on-longevity/

Very old flies cease to age, at least under the definition of aging as the rise of mortality rate with age. Very old flies have a high mortality rate, but that rate plateaus. There has been some back and forth over the years as to whether such a late life plateau in mortality rates can be observed in humans. Presently the consensus is that it is not apparent. It is, however, challenging to draw any robust conclusions on human mortality past the age of 110, as there are so very few survivors to that late stage of life. All of this is fascinating from a scientific point of view, but something of a sideshow when it comes to the treatment of aging as a medical condition. Earnest therapies for aging are needed at half the age of interest here, and given good approaches to repair the underlying damage of aging, it becomes somewhat irrelevant as to what happens when those therapies are not used.

The validity of conclusions about mortality at extreme age depends crucially on the quality of the data on which they are based, as age misrepresentation for the very old is common even in countries with otherwise reliable statistical data. Motivated by this, demographic researchers from 13 countries contribute to the International Database on Longevity (IDL), the third (August 2021) release of which contained 1119 individually validated life lengths of supercentenarians, i.e. those reaching age 110 or more; the data, which cover different time periods for different countries, can be obtained from www.supercentenarians.org. For some countries, the IDL now also includes data on semi-supercentenarians, i.e. people living to an age of at least 105. Since October 2019, IDL has contained French data on 9571 semi-supercentenarians and 241 supercentenarians who died between 1 January 1987 and 31 December 2016. We call these the France 2019 data; all these supercentenarians but only some of the semi-supercentenarians were validated.

We use a combination of extreme value statistics, survival analysis, and computer-intensive methods to analyse the mortality of Italian and French semi-supercentenarians. After accounting for the effects of the sampling frame, extreme-value modelling leads to the conclusion that constant force of mortality beyond 108 years describes the data well and there is no evidence of differences between countries and cohorts. These findings are consistent with use of a Gompertz model and with previous analysis of the International Database on Longevity and suggest that any physical upper bound for the human lifespan is so large that it is unlikely to be approached. Power calculations make it implausible that there is an upper bound below 130 years. There is no evidence of differences in survival between women and men after age 108 in the Italian data and the International Database on Longevity, but survival is lower for men in the French data.

Extracellular Vesicles in Aging and Rejuvenation
https://www.fightaging.org/archives/2021/10/extracellular-vesicles-in-aging-and-rejuvenation/

Extracellular vesicles carry the bulk of communication between cells. The use of extracellular vesicles to adjust cell function and spur regeneration in aged tissues is a logical step beyond stem cell therapies. Much of the benefit of first generation stem cell therapies is mediated by the release of vesicles by transplanted cells, in the short time before those cells fail to engraft and consequently die. Harvesting, storing, and injecting these vesicles is a logistically easier prospect than working with cells; even now, exosomes from stem cell populations can be purchased at a fraction of the cost of stem cell therapies. This is, however, an enormously complex area of biology. As is the case for stem cell therapies, work towards exosome therapies is a way to bypass the lack of a full understanding of the relevant biochemistry by using known beneficial cell populations as a source of signaling to adjust cell behavior in the body. A great deal of work still lies ahead in the continued development of this form of therapy.

The once mythological idea that young blood may confer antiaging benefits has had legitimate scientific support for more than 60 years. Despite the intrigue of these early parabiosis experiments, potential mechanisms for how young blood may be exerting rejuvenating effects remained elusive until much more recently. Historically characterized as "platelet dust" with a role in thrombin formation, or simply as a cellular waste disposal system, the involvement of extracellular vesicles (EVs) in a wide array of biological processes, including aging, is becoming increasingly appreciated. There is an already substantial and quickly growing body of evidence attesting to the importance of EVs in the regulation of systemic aging as well as in a number of age-related detriments including inflammaging, cellular senescence, metabolic dysfunction, cardiovascular disease, cancer, and neurodegeneration.

Additionally, the utilization of age-related changes in EVs as easily accessible aging biomarkers is an attractive strategy. However, the small size of EVs, the insufficiency of current methodologies, and the heterogeneity of EV producers, recipients, and affected biological processes have created extraordinary complexity in the EV field. Significant efforts have been put forth to standardize EV collection methods, characterization, and use to increase reproducibility. While these standardized recommendations offer a reasonable foundation, much work is needed to unravel the physiological significance of EVs in different biological paradigms.

Aging is characterized by a number of complex pathophysiological alterations, some of which are also intensive research topics in the field of EV biology. The intersection of these two fields offers considerable promise, constituting a new and exciting research arena. Recent work in this arena suggests that characterization and manipulation of age-related changes in EVs has the potential to provide a unique window through which to view, and perhaps one-day treat, the systemic deterioration that accompanies aging.

The U-Shaped Association Between Physical Activity and Cardiovascular Mortality
https://www.fightaging.org/archives/2021/10/the-u-shaped-association-between-physical-activity-and-cardiovascular-mortality/

High levels of physical activity in individuals with the greatest risk of cardiovascular disease may well be worse than moderate physical activity when it comes to mortality. We might theorize that this is the outcome of putting an excessive level of stress on a weakened, damaged system. The study noted here is supportive of other similar studies that suggest that physical activity at the high end of the range is detrimental over the long term, in comparison to more moderate levels. Though in this context, "moderate" is probably twice the present recommendation of 150 minutes per week, which is itself more moderate exercise than most of the population undertakes.

The beneficial effect of moderate physical activity (PA) on morbidity and mortality has been observed in the general population. However, the ideal intensity of PA for improving cardiovascular longevity in Japanese general population is uncertain. The aim of this study was to investigate the relationship between the PA and cardiovascular mortality in the general population. This longitudinal cohort study included 1,826 apparently healthy subjects who participated in a community-based health checkup.

There were 31 cardiovascular deaths during 10-year follow-up. Subjects were divided into 4 groups based on the quartiles of PA (low, mild, moderate and high). Kaplan-Meier analysis and multivariate Cox proportional hazard analysis demonstrated that the most favorable cardiovascular prognosis was observed in subjects with moderate PA followed by those with mild PA. High PA as well as low PA were associated with higher cardiovascular mortality compared with mild and moderate PA. Noteworthy, in subjects with high PA, Cox hazard analysis revealed that previous cardiovascular disease, smoking, brain natriuretic peptide levels, and Framingham risk score were associated with cardiovascular mortality.

The results suggest a U-shaped association between cardiovascular mortality and PA. Mild to moderate PA was associated with favorable cardiovascular outcomes in the Japanese general population. High PA might be associated with poor cardiovascular outcomes in subjects with a history of heart disease and high coronary risk factors.

How Much of the Benefit of Calorie Restriction in Mice is Due to Incidental Fasting?
https://www.fightaging.org/archives/2021/10/how-much-of-the-benefit-of-calorie-restriction-in-mice-is-due-to-incidental-fasting/

Both calorie restriction and intermittent fasting can extend life in short-lived species such as mice, the former producing a larger benefit. Both appear to produce benefits to health in humans, though nowhere near the same effects on life span. Mice in past calorie restriction studies tended to be fed at intervals, such as daily, that were in practice imposing periods of fasting as well as a lowered calorie intake. How much of the observed benefits are due to the metabolic changes imposed by reduced calorie intake versus the metabolic changes imposed by time spent fasting? A growing interest in intermittent fasting in the research community has led to the discovery that both reduced calorie intake during a fast and then the restoration of a higher calorie intake at the end of a fast appear to produce distinct benefits. Researchers here report on their efforts to split apart the effects of reduced calorie intake from duration of fasting in mice. The results are interesting.

Researchers began to realize that previous studies had unintentionally combined calorie restrictions with long fasts by providing animals with food just once a day. It was difficult, then, to distinguish the effects of one from the other. "This overlap of treatment - both reducing calories and imposing a fast - was something that everybody saw, but it wasn't always obvious that it had biological significance. It's only been in the past few years that people started getting interested in this issue."

Researchers designed four different diets for mice to follow. One group ate as much as they wanted whenever they wanted. Another group ate a full amount, but in a short period of time - this gave them a long daily fast without reducing calories. The other two groups were given about 30% fewer calories either once a day or dispersed over the entire day. That meant that some mice had a long daily fast while others ate the same reduced-calorie diet but never fasted, which differed from most previous studies of calorie restriction.

It turned out that many of the benefits originally ascribed to calorie restriction alone - better blood sugar control, healthier use of fat for energy, protection from frailty in old age and longer lifespans - all required fasting as well. Mice who ate fewer calories without fasting didn't see these positive changes. Fasting on its own, without reducing the amount of food eaten, was just as powerful as calorie restriction with fasting. Fasting alone was enough to improve insulin sensitivity and to reprogram metabolism to focus more on using fats as a source of energy. The livers of fasting mice also showed the hallmarks of healthier metabolism.

The researchers did not study the effect of fasting alone on lifespan or frailty as mice aged, but other studies have suggested that fasting can provide these benefits as well. While the mice that ate fewer calories without ever fasting did show some improved blood sugar control, they also died younger. Compared with mice who both ate less and fasted, these mice that only ate less died about 8 months earlier on average. "That was quite surprising. In addition to their shorter lifespans, these mice were worse in certain aspects of frailty, but better in others. So, on balance their frailty didn't change much, but they didn't look as healthy."

Suggesting that Viral Infection Can Promote the Spread of Protein Aggregates in the Brain
https://www.fightaging.org/archives/2021/10/suggesting-that-viral-infection-can-promote-the-spread-of-protein-aggregates-in-the-brain/

There is an ongoing debate over whether or not persistent viral infection plays an important role in the development of Alzheimer's disease. That is largely focused on the function of the immune system, given the demonstrated relevance of chronic inflammation and microglial dysfunction to the progression of neurodegenerative conditions. Here, however, researchers provide in vitro evidence to support the hypothesis that viral infection can promote the spread of misfolded proteins between cells in the brain. Aggregates of misfolded or otherwise harmfully modified proteins such as amyloid-β, α-synuclein, and tau are involved in many neurodegenerative conditions. Exactly how these proteins spread as the condition progresses is an area of considerable interest in the research community.

Transmission of aggregates could involve direct cell-to-cell contact, the release of "naked" aggregates into extracellular space or packaging in vesicles, which are tiny bubbles surrounded by a lipid envelope that are secreted for communication between cells. "The precise mechanisms of transmission are unknown. However, it is an obvious guess, that aggregate exchange by both direct cell contact and via vesicles depends on ligand-receptor interactions. This is because in both scenarios, membranes need to make contact and fuse. This is facilitated when ligands are present that bind to receptors on the cell surface and then cause the two membranes to fuse."

Researchers investigated the intercellular transfer of either prions or aggregates of tau proteins, as they occur in similar form in prion diseases or Alzheimer's disease and other "tauopathies". Mimicking what happens as a result of viral infection, the researchers induced cells to produce viral proteins that mediate target cell binding and membrane fusion. Two proteins were chosen as prime examples: SARS-CoV-2 spike protein S, which stems from the virus causing COVID-19, and vesicular stomatitis virus glycoprotein VSV-G, which occurs in a pathogen that infects cattle and other animals. Moreover, cells expressed receptors for these viral proteins, namely the LDL receptor family, which act as docking ports for VSV-G, and human ACE2, the receptor for the spike protein.

"We could show that the viral proteins are incorporated both into the cellular membrane and into the extracellular vesicles. Their presence increased protein aggregate spreading between cells, both by direct cell contact or by extracellular vesicles. The viral ligands mediated an effective transfer of aggregates into recipient cells, where they induced new aggregates. The ligands act like keys that unlock the recipient cells and thus sneak in the dangerous cargo. Certainly, our cellular models do not replicate the many aspects of the brain with its very specialized cell types. However, independent of the tested cell type producing the pathologic aggregates, the presence of viral ligands clearly increased the spreading of misfolded proteins to other cells. All in all, our data suggests that viral ligand-receptor interactions can in principle affect transmission of pathologic proteins."

"The brains of patients suffering from neurodegenerative diseases sometimes contain certain viruses. They are suspected to cause inflammation or to have a toxic effect, thus accelerating neurodegeneration. However, viral proteins could also act differently: They could increase intercellular spreading of protein aggregates already ongoing in neurodegenerative diseases like Alzheimer's. Of course, this needs further studies with neurotropic viruses. Clearly, the impact of viral infections on neurodegenerative diseases deserves in-depth investigation."

Journalistic Balance Run Amok in the Matter of Aging
https://www.fightaging.org/archives/2021/10/journalistic-balance-run-amok-in-the-matter-of-aging/

The implementation of journalistic balance is a self-parodying genre of writing. In the case in which the scientific community is working towards saving countless lives, by implementing therapies targeting the underlying mechanisms of aging, the paint-by-numbers journalist and editor duo will dutifully find a curmudgeonly figure who thinks that everyone should just get on and die, and put in a few quotes in order to balance the article. The piece here is an example of exactly this phenomenon; it is left as an exercise for the reader to identify the other popular media checkboxes lazily checked in the course of its few pages. And one can still use this to say that the quality of articles on the development of therapies for aging is much better than it used to be! A low bar, but slowly rising. Still, it is hard to take the output of what passes for journalism these days at all seriously. Sadly all too many people do just that for every topic with which they have little familiarity.

The quest for eternal youth may not be new, but it is now bankrolled by some of the wealthiest individuals and corporations on Earth. Anti-ageing science works at the level of gene therapy, cell hacking and reconstituting human blood; the medical treatments at its heart are based on "bleeding edge" science and aimed at the mass market. Some focus on biological reprogramming: adding proteins known as Yamanaka factors to cells, causing them to revert to a previous state. Others look at genomic instability or the way DNA damage that accumulates over time might be repaired.

The entrepreneurs in this fledgling field are determined that the end of ageing will come via therapies approved by the US Food and Drug Administration (FDA) and the European Medicines Agency (EMA). The elixir of youth won't be a single drug, but a regimen of treatments that knock out different hallmarks of ageing and allow us to get older without losing our bodies and minds. We will still die: there will be accidents as well as diseases unrelated to age (children still get fatal cancers, after all). But death will become increasingly remote, and no longer preceded by years of inevitable decline. Its advocates argue that, once ageing is cured, the financial, medical, societal, and emotional burden of taking care of the elderly will disappear. But have these entrepreneurs thought about what a post-ageing world would look like? And if they have, would anyone want to live there?

Paul Root Wolpe, 64, director of the centre for ethics at Emory University (and a former senior bioethicist at NASA), told me that a world without ageing would be "an economic disaster". The argument some advocates make for its enormous social benefits is "a misdirection", he said. "I find their arguments extremely naive, sociologically unsupportable, and most importantly, deeply narcissistic. I've never heard a single plausible argument of how radical life extension would benefit society - only an egocentric desire not to die. The truth is, they want to stop ageing. They want to live healthily to 150."

In Wolpe's view, anti-ageing scientists and entrepreneurs minimise or ignore the profound implications of significantly increasing the human lifespan. "The International Monetary Fund has stated that an ageing population in Japan has led to a vanishing labour force, higher demands for social services, a shrinking tax pool, greater wealth disparities - and that's just from living what is currently our lifespan. If we increase it, all of those things would increase exponentially." But in the future envisaged by the biotech start-ups, we would work into our hundreds: an elderly population would still be a labour force. Wolpe had little patience for this idea. "That is a profoundly elite perspective."

Organoids in the Study of Aging
https://www.fightaging.org/archives/2021/10/organoids-in-the-study-of-aging/

Over the course of the past twenty years, researchers have established the techniques needed to grow small volumes of functional tissue for many organ types. Lacking blood vessel networks, these organoids are at most a few millimeters in size; any larger and nutrients cannot perfuse to the innermost cells. There will be a use for organoids grown from a patient's own cells or from universal cell lines in transplantation therapies, such as those developed by Lygenesis. As researchers note here, however, by far the greatest use at present is to produce models for research.

Patient-derived organoids are self-organized 3D tissue cultures that are derived from stem cells. Isolated patients' stem cells differentiate to form an organ-like tissue comprising multiple cell types. Organoids have self-renewal and self-organization capabilities and retain the characteristics of the physiological structure and function of their source. Recent culturing advances aim to create the right environment for the stem cells so they can follow their own genetic instructions to self-organize, forming organoid structures that resemble miniature organs composed of many cell types. This approach provides tractable in vitro models of human physiology and pathology, thereby enabling interventional studies that are difficult or impossible to conduct in human subjects.

The biology of aging is focused on the identification of novel pathways that regulate the underlying processes of aging to develop interventions aimed at delaying the onset and progression of chronic diseases to extend lifespan. However, the research on the aging field has been conducted mainly in animal models, yeast, Caenorhabditis elegans, and cell cultures. Thus, it is unclear to what extent this knowledge is transferable to humans since they might not reflect the complexity of aging in people.

Organoid culture technology is being used in the cancer field to predict the response of a patient-derived tumor to a certain drug or treatment serving as patient stratification and drug-guidance approaches. Modeling aging with patient-derived organoids has a tremendous potential as a preclinical model tool to discover new biomarkers of aging, to predict adverse outcomes during aging, and to design personalized approaches for the prevention and treatment of aging-related diseases and geriatric syndromes. This could represent a novel approach to study chronological and/or biological aging, paving the way to personalized interventions targeting the biology of aging.

Animal Size and Force on Cells in the Evolution of Proficient Regeneration
https://www.fightaging.org/archives/2021/10/animal-size-and-force-on-cells-in-the-evolution-of-proficient-regeneration/

A fair number of researchers are investigating the molecular biology of species capable of proficient regeneration without scarring, such as salamanders and zebrafish. It is suspected that mammals retain much of the necessary biology to accomplish feats of regeneration such as regrowing limbs, mechanisms that are in some way blocked in adults, because this sort of regeneration can occur during embryonic development. Researchers here discuss a novel line of research based on the forces exerted on cells due to animal size, and how cells react to those forces. Proficient regeneration occurs in small species, and perhaps that is an important detail.

So what is the difference between animals that can regenerate tissue without scarring, and those that scar? The answer, it turned out, stemmed from something few if any scientists had previously focused on: animal size and the physical forces on their cells. In some small animals - think zebrafish and salamanders - you don't need strong bonds between cells to help them glom onto one another, but when animals grow as large as elephants or dinosaurs, the bonds between cells must be much stronger. Without such strong bonds, even tissues of medium-sized animals, like cats or dogs, would never hold together on the animals' skeleton. It would be like trying to pile pudding on a coat hanger.

"All the animals capable of scarless regeneration have very small bones and their tissues are almost gelatinous. We wondered if these allometric scaling forces might be part of the reason that zebrafish can regenerate tissues, but humans cannot. Allometric scaling forces are known to change bone size and muscle strength, but no one had looked into how they affect tissue regeneration."

To investigate the role of these forces in scarring, the researchers disrupted sensors that all cells have to detect mechanical stresses in their environment. The scientists blocked a molecule called focal adhesion kinase, the most evolutionarily conserved component of this sensing system, and observed how it affected the tissue healing process in pigs, which have the most similar skin to humans, through a very small lesion on anesthetized skin. "To our surprise, simply blocking this one component allowed burn injuries that normally result in scars to heal with completely normal skin architecture and morphology, just like a salamander would."

The researchers are now pursuing clinical trials to reduce scarring in burn patients or also use techniques described in the previously published research to reduce scarring after accidents or surgery. They are also hopeful that looking at these same mechanisms might be useful in helping other organs, such as the lungs, liver and heart, to heal without scarring after injury or disease.

Calorie Restriction Mimetics in the Context of Cardiovascular Disease
https://www.fightaging.org/archives/2021/10/calorie-restriction-mimetics-in-the-context-of-cardiovascular-disease/

The practice of calorie restriction produces a beneficial upregulation of cellular stress responses. In short-lived species such as mice this can produce a dramatic slowing of aging, improvement in health, and extension of life span. The same mechanisms produce similar short-term benefits to health, but not a significant lengthening of life, in species as long-lived a our own, however. Nonetheless, there is considerable interest in calorie restriction mimetics, compounds that can trigger at least some of the same regulatory mechanisms governing cellular stress responses, particularly the operation of autophagy.

Recent years have seen a growing interest in understanding how dietary interventions shape and interact with the most common cardiovascular risk factors, including hypertension, obesity, metabolic syndrome, and diabetes mellitus type 2. Substantial cardiometabolic improvements have been reported with fasting interventions such as reduction in blood pressure, body weight and fat mass, lower blood glucose, and improvement in insulin sensitivity, both in experimental and clinical studies. Although caloric restriction consistently improves several aspects of health, its application has been hampered by poor compliance and adverse side effects on bone health and immune response, especially in the elderly.

An interesting aspect that warrants further attention is the effect of caloric restriction mimetics or dietary interventions aimed at weight loss on the gut microbiome changes in obese patients with diabetes mellitus type 2 or metabolic syndrome. Although these interventions propose beneficial clinical outcomes, their effect on the gut microbiome is only beginning to unfold. Interestingly, a combination therapy of resveratrol and spermidine synergistically induces autophagy at doses which do not trigger effects of the same magnitude if administered alone. At present, however, it remains elusive what is the optimal dose for any of the caloric restriction mimetics that could provide health benefits or protect humans at risk of cardiovascular disease.

Unlike the current drug development approaches that focus on individual diseases in isolation and consider specificity as a desirable outcome in disease prevention and treatment, both caloric restriction mimetics and caloric restriction intercept multiple different targets. Such pleiotropic mode of action appears advantageous in targeting the complex process of aging as the greatest risk factor for cardiovascular diseases and associated comorbid conditions. Thus, dietary interventions should aim to maintain optimum health and prevent cardiovascular diseases by attenuating the molecular causes of biological aging directly.

Non-cell autonomous effects of caloric restriction mimetics and caloric restriction itself, such as the anti-inflammatory or immune modulatory functions, are increasingly viewed as relevant as cell autonomous mechanisms. Taking this into account, more research is needed to ascertain how different forms of fasting and caloric restriction mimetics can be the most favorable to further improve cardiometabolic markers in healthy adults and patients living with or at risk of developing cardiovascular disease. Based on the currently available data, harnessing caloric restriction mimetics or dietary interventions, such as intermittent fasting or the Mediterranean diet represent a promising preventive venue, which might reduce cardiovascular risk and the burden of cardiovascular disease.

Fat Cells in Cognitive Decline and Neurodegeneration
https://www.fightaging.org/archives/2021/10/fat-cells-in-cognitive-decline-and-neurodegeneration/

Excess visceral fat produces systemic dysfunction throughout the body through many different mechanisms. The most evident is an increase in chronic inflammation, disruptive of health and tissue function. This can occur through a greater burden of senescent cells, through signaling from fat cells that mimics that of infected cells, the presence of debris from dying fat cells, and further mechanisms. Researchers here look at one of these other signaling changes in fat tissue that provoke inflammation, as well as possible means to interfere in that detrimental signaling.

New research shows that fat cells control the systemic response to brain function, causing impairment in memory and cognition in mice. The activation of Na,K-ATPase oxidant amplification loop affects the expression of important protein markers in fat cells as well as in the hippocampus, which can worsen brain function and lead to neurodegeneration. Targeting the fat cells to antagonize Na,K-ATPase may improve these outcomes. "We have aimed to demonstrate that Na,K-ATPase signaling, specifically in adipocytes, play a central role in inducing alterations in specific regions of the brain, most notably in the hippocampus, which is critical to memory and cognitive function."

Researchers used a genetically-modified mouse model that released the peptide NaKtide specifically in adipocytes, or fat cells, to find that NaKtide inhibited the signaling function of Na,K-ATPase. The adipocyte-specific NaKtide expression improved the altered phenotype of adipocytes and improved function of the hippocampus, the part of the brain associated with memory and cognition. Inducing oxidative stress through western diet increased production of inflammatory cytokines confined to adipocytes as well as altered protein markers of memory and cognition in the hippocampus.

"Western diet induces oxidant stress and adipocyte alteration through Na,K-ATPase signaling which causes systemic inflammation and affects behavioral and brain biochemical changes. Our study showed that adipocyte-specific NaKtide expression in our murine model ameliorated these changes and improved neurodegenerative phenotype."