Fight Aging!

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Contents

• Forthcoming Book: Replacing Aging
• TNFα Blockade Prevents Sarcopenia and Increases Life Span in Mice
• Preventing Alzheimer's Associated Epigenetic Changes in a Mouse Model of the Condition
• Inhibition of 15-PGDH Upregulates Prostaglandin E2 to Improve Aged Mouse Muscle Function
• Recellularizing a Rat Thymus with Human Thymic Epithelial Cells Produces a Functional Thymus
• Greater Senescent Cell Burden Correlates with a Worse Cervical Cancer Survival Rate
• Autophagy is a Balance, More is Usually Good, While Too Much More is Harmful
• Immune Aging is the Foundation of Frailty
• Oxidative Stress as a Commonality Between Mechanisms of Stroke and Depression
• The Quality of Epigenetic Clocks Continues to Improve
• Circular RNAs as a Potential Basis for Biomarkers of Aging
• Declining Energy Metabolism in the Aging Brain
• RAGE Signaling Inhibition as a Goal in the Treatment of Inflammatory AGE-Related Conditions
• Inflammazone Driven Chronic Inflammation in the Progression of Age-Related Macular Degeneration
• Cisd2 in Aging and Exercise

Forthcoming Book: Replacing Aging
https://www.fightaging.org/archives/2020/12/forthcoming-book-replacing-aging/

Replacing Aging is a forthcoming book on the treatment of aging as a medical condition. It is presented as putting forward a similar point of view to that found in Ending Aging by Aubrey de Grey and Michael Rae, meaning that the research and medical communities should place a relentless focus on damage and repair of damage. Aging is caused by an accumulation of molecular damage of a few distinct classes in and around cells, that damage spiraling out into a complex network of interacting downstream consequences.

Fully understanding that network, fully understanding the progression of aging, will take the rest of this century, or longer. The root causes of aging, these forms of damage that arise from the normal operation of a youthful metabolism, are much less complex in comparison, and, at this time, are far better understood. Therapies resulting in large benefits, such as significant extension of healthy life and significant reversal of age-related disease, are more likely to arise from work on the causes of aging than from work on understanding the complicated progression of aging. That much is in the process of being demonstrated by senolytics that destroy senescent cells.

Unfortunately, the research community is still largely focused on understanding the intricacies of aging, picking apart the details of the complex, damaged disarray of an aged metabolism, and aiming at no more than a modest slowing of aging. There is comparatively little interest in applying what is already known of the causes of aging. That must change.

Replacing Aging

Replacing Aging outlines how aging will soon be reversible as a result of the advances that are being made in regenerative medicine. The book explains the enormous complexity of aging and how the accumulation of myriad types of macromolecular damage in the body essentially precludes a pharmacological solution to the problem of aging. Nevertheless drugs remain the primary focus of the anti-aging field. Instead of drugs, a decisive way to erase all forms of age-related macromolecular damage at once would be by replacing old worn-out tissues with new young ones. As the book describes, an ability to replace all body parts seems more and more likely, if not inevitable.

Regenerative medicine is developing increasingly functional lab-grown cells, tissues, and organs that are being transplanted into patients today to treat diseases or repair damage. With continued improvements, cells and organs could be used in a more comprehensive manner to replace all body parts and reset the aging clock to near zero. Even the brain can be progressively replaced at a cellular level over time without a loss of self-identity. Existing examples demonstrate that complex brain functions can if given enough time change their neural substrates. And new brain cells added to old brains can form remarkably normal connection patterns. These findings together suggest protocols for brain rejuvenation. Thus, this book heralds the day in the near future when, if we choose to, we will be able to live much longer healthier lives as a result of replacements made possible by regenerative medicine.

Is Longevity actually just Replacing Aging?

"I was a bit of a weird kid growing up. I realized at a young age, in early elementary school in fact, that we are biological machines and that even if we stay healthy, we will eventually break down with time. I didn't like this and wanted to do something about it, so I knew I wanted to be a molecular biologist working on longevity before I even knew that the words "molecular biology" and "longevity" existed. Then in high school, I started reading on my own everything I could about how we function at a molecular level."

"Macromolecular damage is aging, at least from a biologist's perspective. Any other definition such as motor, immune, cognitive performance, for example can lead to claims of rejuvenation while the actual process of macromolecular and cellular decay proceeds without hinderance. This is an important point in the book because many in the aging field use only indirect markers of aging and are open to misinterpretation and false claims."

Aubrey de Grey's Review of "Replacing Aging"

The key to understanding that aging is not a mystery is to understand that it is not a phenomenon of biology, but of physics: it is fundamentally the same thing in a living organism as it is in a car, or an aeroplane, or any man-made machine. Once one realises that, it is a small step to realising that the approach we take - with dramatic success, when we try - to preserving the function of a car is sure to work just as well on the human body, once we develop the corresponding techniques to a level that matches the greater complexity of living organisms.

The author wastes no time in highlighting this key point - not merely in the abstract, but by getting down to specifics. He notes that the way we keep a car going is by preventative maintenance - damage repair. In other words, by maintaining the overall structure and composition of the car as it was initially. And that, of course, what inspires the title of the book, because preventative maintenance is largely about replacing worn or damaged parts.

The world needs far more books like Replacing Aging. In the past year or so, a few other gerontologists have published general-audience books explaining what this field is about and why it is so promising right now - and they all have different styles and will benefit different audiences to different degrees. In my view, Replacing Aging stands out as a shining example of how to get the public to break free of the fatalistic shackles that are so impeding the crusade to create a post-aging world.

TNFα Blockade Prevents Sarcopenia and Increases Life Span in Mice
https://www.fightaging.org/archives/2020/12/tnf%ce%b1-blockade-prevents-sarcopenia-and-increases-life-span-in-mice/

Today's open access research reports a sizable effect on sarcopenia in aged mice via blockade of TNFα, an inflammatory signal molecule associated with cellular senescence and generated by senescent cells. Sarcopenia is the progressive loss of muscle mass and strength that takes place with age, more severely in some individuals than in others, but everyone is affected. The drug used in the study is Etanercept, already widely employed to treat autoimmune conditions. It functions as a decoy receptor, binding circulating TNFα to prevent it from interacting with cell receptors to trigger detrimental changes in cell behavior. The outcome of note is that treated mice maintain muscle volume from 12 to 22 months of age, while controls lose ~20% of muscle volume over the same period.

Etanercept is not a drug that one would take for the long term on a whim. Like most existing approaches to suppressing immune overactivation in autoimmune conditions, it is a blunt tool. It suppresses immune signaling and activity across the board, both necessary and inappropriate, and the side effects thus include a potentially dangerous weakening of the immune response to infection. In this case the drug is a tool for the purposes of research, not a potential treatment. It is used to produce what looks a lot like a confirmation of the role of senescent cell accumulation and consequent chronic inflammatory signaling in the onset of sarcopenia with age. One possible way to remove a sizable portion of the harmful TNFα signaling, without disrupting the beneficial TNFα signaling, is to get rid of senescent cells.

Senescent cells accumulate with age, lingering where they should be destroyed, either by programmed cell death or by the immune system. These errant cells generate the senescence-associated secretory phenotype (SASP), a mix of inflammatory, pro-growth, and other signals. When sustained over the long term, the SASP is very disruptive of tissue and immune function, a sizable contributing factor in age-related degeneration. TNFα features prominently in the SASP, so while that connection isn't called out in this paper, it seems likely that one could use senolytic therapies that selectively destroy senescent cells in order to prevent sarcopenia.

Pharmacological blockade of TNFα prevents sarcopenia and prolongs survival in aging mice

Aging is accompanied by chronic low-grade inflammation ("inflammaging"), which could have a causal role in sarcopenia. Tumor necrosis factor-α (TNFα), interleukin-6 (IL-6), interleukin-10, and interleukin-15 might contribute to the loss of muscle mass. TNFα is a particularly interesting candidate, being a non-redundant target in inflammatory human diseases associated to complex multi-cytokine inflammatory responses. In addition, TNFα is known to promote muscle wasting and cachexia by promoting protein degradation while decreasing protein synthesis and by inhibiting muscle regeneration by blocking proliferation and differentiation of muscle stem cells. In aged muscle, this inhibition seems to be preferentially mediated by TNFα released by bone marrow-derived leukocytes and TNFα genetic knockdown protects against aging-induced fiber loss and reduction of stem cell regenerative capacity. TNFα also promotes apoptosis of both type I and type II muscle fibers.

Etanercept is a dimeric fusion protein that acts as soluble receptor interfering with TNFα binding to tissue receptors and has been employed for the treatment of autoimmune diseases for over two decades, with excellent efficacy and safety profiles. We evaluated the effects of TNFα blockade on spontaneous aging in wild type mice aged 16 to 28 months (corresponding to 50-90 years of human age). This treatment quenched age-associated spontaneous muscle loss, reduced fiber type shift, improved muscle function, and modestly increased animal life span.

We found that spontaneous aging in mice reflects many features of human aging at the skeletal muscle level. Specifically, we observed that between 12 and 28 months of age, corresponding to 40-90 years of age in humans, aging mice lost weight and muscle mass. This was accompanied by progressive reduction of fiber cross-sectional area and of mouse endurance during exercise. Fiber size decline from 12 to 22 months was severe and further worsened at 28 months. Accordingly, MRI-measured muscle volume and body weight decreased starting from month 22 of age. The cells of innate and acquired immunity were consistently detectable in skeletal muscle at 22 months of age and remained stable thereafter. The concentration of circulating cytokines was observed to follow comparable kinetics. This suggests that inflammation could start early in aged mice, reaching a "steady state" at a low level for an extended period.

Preventing Alzheimer's Associated Epigenetic Changes in a Mouse Model of the Condition
https://www.fightaging.org/archives/2020/12/preventing-alzheimers-associated-epigenetic-changes-in-a-mouse-model-of-the-condition/

Hypothetically, if one could prevent all of the detrimental reactions a cell undergoes in response to a specific disease-causing agent, would that cure the resulting disease? Clearly some disease causing agents are just plain destructive, and further detrimental cellular reactions to that destruction are not the important component of the condition. Are there categories of condition in which the problem is largely a matter of inappropriate cellular reactions to an otherwise innocuous agent, however? In those cases, preventing that reaction could be a viable approach to therapy - with the caveat that a truly innocuous agent is an unlikely circumstance. All aspects of cellular biochemistry act in multiple ways, and that includes pathogens, persistent metabolic waste, excessive inflammatory signaling, and so forth. Blocking one detrimental reaction to an agent still leaves all of the other reactions in place, known and unknown.

Cell behavior is governed by epigenetic mechanisms that determine which proteins are produced and in what quantity. This is a complex, dynamic system of feedback between protein production, environment, and cell activity. Is it possible in principle and practice to adjust specific parts of the epigenetic system in order to steer cells away from a detrimental reaction involved in disease progression? Yes, as today's research materials illustrate. We will likely see much more of this class of approach in the future. It is analogous to widely used strategies such as blocking specific cell surface receptors or suppressing production of specific proteins. All attempt to interfere beneficially in the downstream effects of disease causing agents, in the reactions of cells, without addressing the agents themselves.

Memory deficits resulting from epigenetic changes in Alzheimer's can be reversed

Memory loss associated with Alzheimer's disease (AD) may be able to be restored by inhibiting certain enzymes involved in abnormal gene transcription, according to a preclinical study. Alzheimer's disease alters the expression of genes in the prefrontal cortex, a key region of the brain controlling cognitive processes and executive functions. By focusing on gene changes caused by epigenetic processes (those that are not related to changes in DNA sequences) such as aging, the UB researchers were able to reverse elevated levels of harmful genes that cause memory deficits in AD.

Transcription of genes is regulated by an important process called histone modification, where histones, the proteins that help package DNA into chromosomes, are modified to make that packaging looser or tighter. The nature of the packaging, in turn, controls how genetic material gains access to a cell's transcriptional machinery, which can result in the activation or suppression of certain genes. Researchers found that H3K4me3, a histone modification called histone trimethylation at the amino acid lysine 4, which is linked to the activation of gene transcription, is significantly elevated in the prefrontal cortex of people with AD and mouse models of the disease. That epigenetic change is linked to the abnormally high level of histone-modifying enzymes that catalyze the modification known as H3K4me3. Researchers found that when the AD mouse models were treated with a compound that inhibits those enzymes, they exhibited a significantly improved cognitive function.

In making that discovery, the UB team also identified a number of new target genes, including Sgk1 as a top-ranking target gene of the epigenetic alteration in AD. Sgk1 transcription is significantly elevated in the prefrontal cortex of people with AD and in animal models with the disorder. Researchers found that abnormal histone methylation at Sgk1 contributes to its elevated expression in AD. Sgk1 encodes an enzyme activated by cell stress, which plays a key role in numerous processes, such as regulating ion channels, enzyme activity, gene transcription, hormone release, neuroexcitability, and cell death. The researchers found it is highly connected to other altered genes in AD, suggesting it may function as a kind of hub that interacts with many molecular components to control disease progress.

"In this study, we have found that administration of a specific Sgk1 inhibitor significantly reduces the dysregulated form of tau protein that is a pathological hallmark of AD, restores prefrontal cortical synaptic function, and mitigates memory deficits in an AD model. These results have identified Sgk1 as a potential key target for therapeutic intervention of AD, which may have specific and precise effects."

Targeting histone K4 trimethylation for treatment of cognitive and synaptic deficits in mouse models of Alzheimer's disease

Epigenetic aberration is implicated in aging and neurodegeneration. Using postmortem tissues from patients with Alzheimer's disease (AD) and AD mouse models, we have found that the permissive histone mark H3K4me3 and its catalyzing enzymes are significantly elevated in the prefrontal cortex (PFC). Inhibiting H3K4-specific methyltransferases with the compound WDR5-0103 leads to the substantial recovery of PFC synaptic function and memory-related behaviors in AD mice. Among the up-regulated genes reversed by WDR5-0103 treatment in PFC of AD mice, many have the increased H3K4me3 enrichment at their promoters. One of the identified top-ranking target genes, Sgk1 is also significantly elevated in PFC of patients with AD. Administration of a specific Sgk1 inhibitor reduces hyperphosphorylated tau protein, restores PFC glutamatergic synaptic function, and ameliorates memory deficits in AD mice. These results have found a novel epigenetic mechanism and a potential therapeutic strategy for AD and related neurodegenerative disorders.

Inhibition of 15-PGDH Upregulates Prostaglandin E2 to Improve Aged Mouse Muscle Function
https://www.fightaging.org/archives/2020/12/inhibition-of-15-pgdh-upregulates-prostaglandin-e2-to-improve-aged-mouse-muscle-function/

The researchers involved in today's research have been investigating the role of prostaglandin E2 (PGE2) in muscle stem cell function for some years. PGE2 levels decline with age, and this appears to be sufficient to cause a sizable fraction of the characteristic loss of muscle mass and strength that accompanies aging, a condition known as sarcopenia. Other lines of evidence point to loss of stem cell function in muscle tissue as the most important proximate cause of sarcopenia.

The best way to establish whether or not a mechanism is important in aging and loss of function is to block, remove, or reverse it and see what happens. Thus researchers identified 15-PGDH as a regulator of PGE2; forcing a reduction in 15-PGDH levels in old mice causes an increase in PGE2 to youthful levels, and a corresponding improvement in muscle function. This may be mediated in part by improved stem cell function, but the data from treated mice, such as the improved mitochondrial function observed in muscle cells, shows that other mechanisms are involved as well.

Small molecule restores muscle strength, boosts endurance in old mice, study finds

Previously, researchers found that a molecule called prostaglandin E2 can activate muscle stem cells that spring into action to repair damaged muscle fibers. "We wondered whether this same pathway might also be important in aging. We were surprised to find that PGE2 not only augments the function of stem cells in regeneration, but also acts on mature muscle fibers. It has a potent dual role." Prostaglandin E2 levels are regulated by 15-PGDH, which breaks down prostaglandin E2. The researchers used a highly sensitive version of mass spectrometry, a method for differentiating closely related molecules, to determine that compared with young mice, the 15-PGDH levels are elevated in the muscles of older animals, and the levels of prostaglandin E2 are lower. They found a similar pattern of 15-PGDH expression in human muscle tissues, as those from people in their 70s and early 80s expressed higher levels than those from people in their mid-20s.

The researchers administered a small molecule that blocks the activity of 15-PGDH to the mice daily for one month and assessed the effect of the treatment on the old and young animals. "We found that, in old mice, even just partially inhibiting 15-PGDH restored prostaglandin E2 to physiological levels found in younger mice. The muscle fibers in these mice grew larger, and were stronger, than before the treatment. The mitochondria were more numerous, and looked and functioned like mitochondria in young muscle." Treated animals were also able to run longer on a treadmill than untreated animals. When researchers performed the reverse experiment - overexpressing 15-PGDH in young mice - the opposite occurred. The animals lost muscle tone and strength, and their muscle fibers shrank and became weaker, like those of old animals.

Finally, the researchers observed the effect of prostaglandin E2 on human myotubes -immature muscle fibers - growing in a lab dish. They found that treating the myotubes with prostaglandin E2 caused them to increase in diameter, and protein synthesis in the myotubes was increased - evidence that prostaglandin E2 worked directly on the muscle cells, not on other cells in the tissue microenvironment. "It's clear that this one regulator, 15-PGDH, has a profound effect on muscle function. We're hopeful that these findings may lead to new ways to improve human health and impact the quality of life for many people. That's one of my main goals."

Recellularizing a Rat Thymus with Human Thymic Epithelial Cells Produces a Functional Thymus
https://www.fightaging.org/archives/2020/12/recellularizing-a-rat-thymus-with-human-thymic-epithelial-cells-produces-a-functional-thymus/

Decellularization followed by recellularization is a well explored approach to tissue engineering. Researchers take a donor organ or tissue section, decellularize it to leave the intricate extracellular matrix and all of its chemical cues, and then recellularize with with the desired mix of cells. When those cells are derived from a patient, it is possible to generate tissue that can be transplanted into that patient with minimal risk of rejection. There are also groups working on enabling cross-species transplantation from pigs to humans via this strategy of replacing all of the cells in an organ with patient-matched cells.

Further, recellularization can bypass the major challenge of vascular network creation in tissue engineering. Natural tissues contain extensive capillary networks, hundreds of tiny blood vessels passing through every square millimeter of tissue cross-section. Without capillaries, tissue cannot be more than a millimeter or two in thickness, as cells will not be able to receive nutrients. Capillary networks have so far proven challenging to produce at the fine scale needed via bioprinting of entirely artificial tissue structures, though some inroads have been made in recent years. A decellularized extracellular matrix contains those capillaries already.

This is not to say that recellularization of a decelluralized tissue is straightforward. Just like the production of organoids, small functional organ tissue sections grown from cells, a recipe must be established, the right cell populations derived and introduced into the right places, in the right order, provided with the right supporting cues and nutrients, and so forth. This is different for each different type of organ tissue, and there are a great many organs worthy of interest.

Today's example is the production of a recellularized organ important to the immune system, the thymus. The thymus atrophies with age, but active thymic tissue is required for thymocytes created in the bone marrow to mature into T cells of the adaptive immune system. As the supply of new T cells diminishes with age, the adaptive immune system becomes ever more dysfunctional and damaged. The thymus is unfortunately deep within chest, and a straightforward transplantation is a more extensive surgery than would be desirable in later life. The researchers behind Lygenesis have demonstrated in animal models that thymic organoid tissue placed into much more accessible lymph nodes can function correctly, however. Since thymocytes already migrate to the thymus, moving (or even distributing) the thymus to other locations in the body is a possibility. It remains to be seen as to how the tissue engineering approaches to the challenge of thymic atrophy - and consequent immune dysfunction - will evolve in the years ahead, but producing functional thymic tissue is a necessary starting point.

Scientists build whole functioning thymus from human cells

Researchers have rebuilt a human thymus, an essential organ in the immune system, using human stem cells and a bioengineered scaffold. To rebuild this organ, the researchers collected thymi from patients and in the laboratory, grew thymic epithelial cells and thymic interstitial cells from the donated tissue into many colonies of billions of cells. The next step for the researchers was to obtain a structural scaffold of thymi, which they could repopulate with the thymic cells they had cultured. For this, researchers developed a new approach to remove all the cells from rat thymi, so only the structural scaffolds remained. They had to use a new microvascular surgical approach for this, as conventional methods are not effective for the thymus.

The researchers then injected the organ scaffolds with up to six million human thymic epithelial cells as well as interstitial cells from the colonies they had grown in the lab. The cells grew onto the scaffolds and after only five days, the organs had developed to a similar stage as those seen in nine-week old foetuses. Finally, the team implanted these thymi into mice. They found that in over 75% of cases, the thymi were able to support the development of human lymphocytes. The researchers are continuing their work rebuilding thymi to refine and scale up the process.

Reconstitution of a functional human thymus by postnatal stromal progenitor cells and natural whole-organ scaffolds

The thymus is a primary lymphoid organ, essential for T cell maturation and selection. There has been long-standing interest in processes underpinning thymus generation and the potential to manipulate it clinically, because alterations of thymus development or function can result in severe immunodeficiency and autoimmunity. Here, we identify epithelial-mesenchymal hybrid cells, capable of long-term expansion in vitro, and able to reconstitute an anatomic phenocopy of the native thymus, when combined with thymic interstitial cells and a natural decellularised extracellular matrix (ECM) obtained by whole thymus perfusion. This anatomical human thymus reconstruction is functional, as judged by its capacity to support mature T cell development in vivo after transplantation into humanised immunodeficient mice.

Greater Senescent Cell Burden Correlates with a Worse Cervical Cancer Survival Rate
https://www.fightaging.org/archives/2020/12/greater-senescent-cell-burden-correlates-with-a-worse-cervical-cancer-survival-rate/

It is thought that the burden of senescent cells is likely correlated with survival in many cancers. Senescent cells cease to replicate and begin to secrete pro-growth, pro-inflammation signals. Most senescent cells are rapidly destroyed by the immune system, but this process slows with age and thus senescent cells accumulate. Cellular senescence does act to suppress cancer in its earliest stages, by removing those cells most likely to become cancerous. Once a significant number of senescent cells are present, however, their signaling begins to aid cancer growth. Thus we might expect to see that the application of senolytic therapies, capable of selectively destroying senescent cells, will slow down the progression of cancer in many cases. The standard classes of cancer therapy, those that work by damaging cells quite aggressively, have the side-effect of inducing greater levels of cellular senescence throughout the body. They may all become more effective when paired with senolytics.

How well women with cervical cancer respond to treatment and survive correlates with the level of 10 proteins in their blood that also are associated with a cell state called senescence. Researchers looked at pretreatment levels of these proteins in the blood of 565 women with stage 2 and 3 cervical cancer, who received standard treatments of internal radiation, called brachytherapy, external radiation, or both. They found that women with low levels of the proteins secreted by senescent cells had higher survival rates than those with high levels of these senescence-associated secreted phenotypes, or SASPs.

Additionally researchers found that brachytherapy, which implants a radiation source close to the cervix, greatly improved survival of patients who had high levels of these SASPs but had little impact on those with low levels. "These results demonstrate that cellular senescence is a major determining factor for survival and therapeutic response in cervical cancer, and suggest that senescence reduction therapy may be an efficacious strategy to improve the therapeutic outcome of cervical cancer." In women with moderate to high blood levels of SASPs, use of a class of drugs called senolytics - which target these cells for elimination and are under study to improve age-related problems and disease - as an adjunct therapy could help.

While cancer cells more typically are associated with rapid reproduction that enables cancer's growth, senescent cells cannot divide and reproduce. The proteins these senescent cancer cells are secreting helps create an inflammatory state in which cancer thrives and helps lay the groundwork for cancer spread. It also provides some protection from radiation therapy, which like chemotherapy, works in part by killing off typically rapidly dividing cancer cells. "The senescent proteins really change how cancer cells may respond to therapy."

Autophagy is a Balance, More is Usually Good, While Too Much More is Harmful
https://www.fightaging.org/archives/2020/12/autophagy-is-a-balance-more-is-usually-good-while-too-much-more-is-harmful/

One of the more intriguing findings to emerge from study of the relationship between stress response mechanisms in cellular metabolism and the pace of degenerative aging is that evolution has not optimized for life span. Many aspects of metabolism can be adjusted in small ways - in mice, worms, flies, and so forth - in order to modestly slow aging. Yet these small changes are well within the bounds of what one would expect evolution to have already produced. Why didn't that happen? A long life and lasting health are just not high in the list of important pressures on evolutionary selection, it seems. Thus we have autophagy, an important collection of cellular maintenance mechanisms that run suboptimally in near every species. Make autophagy somewhat more efficient, up to a point, and health and life span improve.

The increasing number of people living with age-related diseases underscores the importance of ageing research to improve healthspan. Two well-studied evolutionary conserved interventions that extend lifespan and improve health are dietary restriction and down-regulation of nutrient sensing pathways, such as glucose sensing by insulin and amino acid sensing by the target-of-rapamycin signalling pathway. One common characteristic of these anti-ageing interventions is an increase in autophagy, a cellular pathway that degrades damaged proteins and organelles to supply essential building blocks and energy.

To help provide a more direct link between autophagy and healthy ageing, we fine-tuned overexpression of Atg1 kinase, which is critical for autophagy induction, and measured its effect on longevity in the fruit fly Drosophila. Interestingly, we observed that a moderate increase in autophagy is beneficial in extending healthy lifespan, whereas strong autophagy up-regulation is detrimental and leads to progressive lipid loss and decreased lifespan. Moderate and stronger Atg1 overexpression displayed an opposing transcriptional profile of mitochondrial genes, being upregulated in long-lived and down-regulated in short-lived Atg1 over-expressing animals. Overall, we provide a detailed description of the phenotypes associated with varying degrees of autophagy up-regulation in vivo, demonstrating that autophagy enhancement delays ageing only when applied in moderation.

Immune Aging is the Foundation of Frailty
https://www.fightaging.org/archives/2020/12/immune-aging-is-the-foundation-of-frailty/

Here find a perspective on the great importance of a functional immune system to health in later life. Many of the declines of aging appear strongly influenced, at the very least, by the progressive disarray of the immune system. It becomes less competent in destroying pathogens and malfunctioning cells, but at the same time ever more active in response to the molecular damage and cellular dysfunction accompanying aging. That inappropriate activity takes the form of chronic inflammation that disrupts tissue function and accelerates the onset and progression of all of the common age-related conditions.

The interrelation of the processes of immunity and senescence now receives an unprecedented emphasis during the COVID-19 pandemic, which brings to the fore the critical need to combat immunosenescence and improve the immune function and resilience of older persons. Here we review the historical origins and the current state of the science of innate and adaptive immunity in aging and longevity. Following a century of study, at the present time, natural immunity is understood to consist of three interrelated parts: physiological barriers, innate immunity, and adaptive immunity. All of these are affected by aging. Immunosenescence results in increased susceptibility and severity of infectious diseases and non-communicable age-associated diseases, among them cancer, cardiovascular disease, and autoimmunity.

Excessive levels or activity of antimicrobial peptides, C-reactive protein, complement system, TLR/NF-κB, cGAS/STING/IFN and AGEs/RAGE pathways, myeloid cells and NLRP3 inflammasome, declined levels of NK cells in innate immunity, thymus involution and decreased amount of naive T-cells in adaptive immunity, are biomarkers of aging and predisposition factors for cellular senescence and aging-related pathologies. Long-living species, human centenarians, and women are characterized by less inflammaging and decelerated immunosenescence. Despite recent progress in understanding, a harmonious theory of immunosenescence is still developing. Geroprotectors targeting these mechanisms are just emerging, including rapamycin, senolytics, metformin, acarbose, spermidine, NAD+ enhancers, and lithium.

Oxidative Stress as a Commonality Between Mechanisms of Stroke and Depression
https://www.fightaging.org/archives/2020/12/oxidative-stress-as-a-commonality-between-mechanisms-of-stroke-and-depression/

Cells in aged tissue are characterized by a state of oxidative stress, the presence of excessive numbers of oxidizing molecules that damage cell structures by reacting with them. Oxidative stress goes hand in hand with chronic inflammation and mitochondrial dysfunction, both of which are also features of aged tissues. For any universal state of this nature, one can then link it to many varied conditions, even those that might initially appear to have very little to do with one another. That is the case here in this consideration of commonalities between depression and stroke.

A significant percentage of older individuals develop one or more age-related diseases, which may include two leading diseases characterized by high incidence and disability: stroke and depression. Between 2006 and 2016, the actual number of stroke deaths increased 3.7%, although the age-adjusted mortality rate decreased 16.7% due to the large increase in the number of elderly people. Like stroke, another disease that affects a significant proportion of the population is depression. The 12-month prevalence of major depressive disorder (MDD) is about 6%, while the lifetime risk of MDD is nearly 15-18%. Moreover, older age is identified as a consistent and important risk factor for a worse prognosis. This phenomenon may be associated with the effect of cognitive impairment.

Over the past two decades, studies have identified the role of oxidative stress (OS) in these two diseases. Recently, preclinical experiments and clinical trials have focused on studying the efficacy of antioxidants and combined therapy with antidepressants in stroke or depressed patients. OS describes a state in which the body produces excessive reactive oxygen species (ROS) and reactive nitrogen species (RNS) in response to deleterious substances. Under physiological conditions, moderate OS activity is necessary for body health. Toxic effects derived from ROS and RNS can be ameliorated or neutralized by free radical (FR) scavengers and the antioxidant system. However, when a large number of ROS and RNS are generated, excessive FR then induce molecular oxidation, cell membrane modification, and enzyme inactivation, resulting in cellular damage and functional decline.

There is a close link between oxidative stress and aging, and this link can be proven through many related mechanisms. Firstly, age-related cognitive decline is a consequence of increased OS and neuroinflammation activity in the the aging hippocampus, and a consequence of reduced neurogenesis and synaptic plasticity. Furthermore, mutual effects of inflammation and OS are observed to exacerbate the aging brain. Inflammation stimulates both macrophages and microglia to generate mitochondrial ROS to cause cognitive decline, whereas OS-damaged cells produce inflammatory mediators to promote microglial aging. Secondly, aging and OS can damage the brain by negatively affecting neuroplasticity, brain homeostasis, and cognitive function.

OS lies in the center of the "aging-stroke-depression" network. First, when stroke occurs in animals or patients, excessive generation of ROS follows, leading to cellular damage and brain injury. Second, OS mediates inflammation, apoptosis, and the microbiota-gut-brain axis to increase the accumulation of ROS, followed by brain deterioration. Third, aging acts as a risk factor and aggravates the development of stroke and depression via OS and OS-induced pathways. Due to the central role of OS in this network, administration of antioxidants seems to provide therapeutic ways for stroke and depression.

The Quality of Epigenetic Clocks Continues to Improve
https://www.fightaging.org/archives/2020/12/the-quality-of-epigenetic-clocks-continues-to-improve/

There is at present a diverse exploration of clocks that assess biological age, these clocks constructed as weighted combinations of data picked from the epigenome, transcriptome, or proteome, all of which change in characteristic ways with age. Many different clocks are at various stages of development and refinement. The goal is the production of a robust, low-cost, rapid way to assess the efficacy of potential rejuvenation therapies: if one can use a blood test ten days before and ten days after a treatment, that would be a great deal easier than having to wait and see over the course of a life span.

Unfortunately, this goal remains a future phase of development for this class of technology. Given that there is no good understanding of exactly which processes of molecular damage cause specific changes in the epigenome, transcriptome, and proteome, every algorithm must be calibrated against a potential treatment before it can be used to assess that treatment. Which somewhat defeats the point, as the only way to calibrate it is to run the slow, expensive life span studies that we'd all like to avoid. Still, the research community is presently energetically engaged in improving on present approaches to the production of clock algorithms, as illustrated by the example here.

Researchers have produced DeepMAge, a novel aging clock that was trained to predict human age on more than 6000 DNA methylation profiles. By analyzing the methylation patterns it can estimate human age within a 3-year error margin, which is more accurate than any other human aging clock. Aging clocks boom started in 2013 when the first DNA methylation aging clocks by Horvath and Hannum were published. They have proven to be an indispensable tool in aging research, letting scientists understand its mechanisms and develop longevity interventions.

Unlike its predecessors, DeepMAge is a neural network that may prove to be more efficient in some other ways apart from prediction accuracy. In the original paper, DeepMAge deems people with certain conditions to be older, which may be useful for the development of early diagnostics tools. For example, women with ovarian cancer are on average predicted 1.7 years older than healthy women of the same chronological age, and likewise, multiple sclerosis patients are predicted 2.1 years older. Similar results have been obtained for several other conditions: irritable bowel diseases, dementia, obesity.

Higher age predictions indicate a faster pace of aging in these conditions, which begs the question: is a higher aging rate a precondition to them or is it just an epigenetic footprint of the harm they cause? The authors plan to further investigate the links between epigenetics and longevity using DeepMAge. "Aging clocks have come a long way since the first works by Horvath and Hannum in 2013. We are happy to contribute to this research field. Now, we are going to explore how epigenetic aging can be slowed down with the interventions available to consumers."

Circular RNAs as a Potential Basis for Biomarkers of Aging
https://www.fightaging.org/archives/2020/12/circular-rnas-as-a-potential-basis-for-biomarkers-of-aging/

The presence and function of circular RNAs in cells is comparatively poorly understood. The expression levels of at least some circular RNAs appear to change with age. This suggests that, even without a full understanding of function, it might be possible to use this data as the basis for a biomarker of aging. It is already the case that other biomarkers of aging have been constructed from weighted combinations of age-related changes in the broader transcriptome of RNA expression. These join aging clocks built from epigenetic and proteomic data, all of which exhibit changes that are characteristic of age.

The commonality between all of these approaches is that it remains very unclear as to exactly how the causes of aging, the underlying forms of molecular damage, lead to specific changes in the epigenome, transcriptome, or proteome. These measures of biological age are black boxes at present, and thus hard to use as assessments for the effectiveness of any given approach to rejuvenation. Perhaps they reflect only a few of the mechanisms of aging, or give a great deal of weight to one over another, for example. We just don't know yet.

Circular RNAs (circRNAs), a novel type of universal and diverse endogenous transcripts that has been a recent focus in the transcriptomics field, were first observed through an electron microscope in the cytoplasm of eukaryotic cells in 1979. CircRNAs form covalently closed loop structures and are more stable than linear RNAs, insusceptible to degradation by RNA exonuclease or RNase R. Subsequent reports revealed that circRNAs can act as miRNA sponges, transcriptional regulators, binding partners of proteins, or even translated into functional proteins. Furthermore, circRNAs are abundant, relatively stable, specifically expressed in tissues, and evolutionary conserved among species, affording them the potential to be biomarkers for human diseases.

Recent studies have identified several circRNAs as regulators of various pathways that are involved in aging and cellular senescence. In particular, dysregulated circRNAs were implicated in the pathophysiology of age-related diseases, including cerebrovascular disease, neurodegenerative disease, cancer, diabetes, rheumatoid arthritis, and osteoporosis.

In recent years, circRNAs have gradually become one of the most prominent targets in the field of transcriptomics because of their critical roles in the regulation of gene expression and development of several diseases. The characteristic stability, abundance, and tissue-specific expression of circRNAs confer them great potential for use as biomarkers of various diseases. Notably, circRNAs can exist in the exosomes and plasma due to their excellent stability, thus, providing a more convenient way for diagnosing pathologies. Further investigations regarding the function and mechanism underlying the associations between circRNAs and age-related diseases are required.

Declining Energy Metabolism in the Aging Brain
https://www.fightaging.org/archives/2020/12/declining-energy-metabolism-in-the-aging-brain/

This open access paper argues for the importance of mitochondrial dysfunction in the brain to the onset of neurodegenerative conditions. The primary function of mitochondria, a herd of these bacteria-like organelles found in every cell, is the production of adenosine triphosphate (ATP), a chemical energy store molecule. The energy stored in ATP is used to power cellular operations. It is thus vital in every tissue, but particularly so in the most energy-hungry tissues, such as brain and muscle.

With advancing age, mitochondria become dysfunctional throughout the body, and ATP production falters as a consequence. A network of interacting contributing causes is involved, such as loss of NAD, changes in gene expression that cause changes in mitochondrial morphology, impairment of the quality control mechanism of mitophagy responsible for removing worn and damaged mitochondria, and damage to mitochondrial DNA. Effective means of addressing age-related mitochondrial dysfunction is an important topic in rejuvenation research.

There is a growing body of evidence that indicates that the aging of the brain results from the decline of energy metabolism. In particular, the neuronal metabolism of glucose declines steadily, resulting in a growing deficit of adenosine triphosphate (ATP) production - which, in turn, limits glucose access. This vicious circle of energy metabolism at the cellular level is evoked by a rising deficiency of nicotinamide adenine dinucleotide (NAD) in the mitochondrial salvage pathway and subsequent impairment of the Krebs cycle. A decreasing NAD level also impoverishes the activity of NAD-dependent enzymes that augments genetic errors and initiate processes of neuronal degeneration and death.

This sequence of events is characteristic of several brain structures in which neurons have the highest energy metabolism. Neurons of the cerebral cortex and basal ganglia with long unmyelinated axons and these with numerous synaptic junctions are particularly prone to senescence and neurodegeneration. Unfortunately, functional deficits of neurodegeneration are initially well-compensated, therefore, clinical symptoms are recognized too late when the damages to the brain structures are already irreversible. Therefore, future treatment strategies in neurodegenerative disorders should focus on energy metabolism and compensation age-related NAD deficit in neurons.

RAGE Signaling Inhibition as a Goal in the Treatment of Inflammatory AGE-Related Conditions
https://www.fightaging.org/archives/2020/12/rage-signaling-inhibition-as-a-goal-in-the-treatment-of-inflammatory-age-related-conditions/

Advanced-glycation end products (AGEs) cause issues in two major ways. Firstly a few species of persistent AGE can cross-link molecules of the extracellular matrix, changing tissue properties in harmful ways, such as loss of elasticity in blood vessels and skin. Secondly, more prevalent short-lived AGEs can provoke chronic inflammation through their interaction with the receptor for AGEs, RAGE. This is thought to be an important contributing cause of chronic inflammation in metabolic conditions such as diabetes, but also shows up as a concern in a number of other conditions. As illustrated in this review, the research community is interested in finding ways to reduce or interfere in inflammatory AGE-RAGE signaling. There is a great deal more work taking place in this part of the field than in the search for ways to break persistent AGE cross-links.

Advanced-glycation end products (AGEs) are heterogeneous molecules derived from post-translational nonenzymatic modifications of macromolecules including proteins, lipids, and nucleic acids by glucose or other saccharides (fructose and pentose). AGEs are deleterious molecules and are found to be increased in the plasma of physiological aging and age-related diseases, diabetes mellitus, and autoimmune/inflammatory rheumatic diseases.

AGEs, by binding to receptors for AGE (RAGEs), alter innate and adaptive immune responses to induce inflammation and immunosuppression via the generation of proinflammatory cytokines, reactive oxygen species (ROS), and reactive nitrogen intermediates (RNI). These pathological molecules cause damage to vascular endothelial, smooth muscular, and connective tissue cells and renal mesangial, endothelial, and podocytic cells in AGE-related diseases. In this context, oxidative stress can disturb intracellular signals to become pathological states, particularly insulin-mediated metabolic responses and insulin resistance.

AGEs contribute to the development of physiological aging and many major chronic diseases, including diabetic pathology, and neurodegenerative, autoimmune/inflammatory, and metabolic cardiovascular diseases. Accordingly, it is valuable to search for novel therapeutic interventions for AGE-related diseases. The underlying modes of action of different AGE inhibitors are based on the attenuation of glycosylation, antioxidative stress, metal ion chelating, and scavengers of reactive 1,2-dicarbonyl compounds or ROS/RNI. Arbitrarily, these novel therapeutic AGE inhibitors can be classified into 4 categories: (1) inhibitors of AGE formation; (2) breakers of preformed AGEs; (3) blockades of AGE-RAGE axis signaling; and (4) inducers of intracellular glyoxalase, ubiquitin-proteasome, and autophagy pathways.

Inflammazone Driven Chronic Inflammation in the Progression of Age-Related Macular Degeneration
https://www.fightaging.org/archives/2020/12/inflammazone-driven-chronic-inflammation-in-the-progression-of-age-related-macular-degeneration/

The later, "wet" stages of macular degeneration involve the inappropriate formation of leaky blood vessels under the retina, destroying its integrity and function. This is in large part driven by chronic inflammation and the altered cell behavior that it causes. Researchers here focus on one specific class of regulators of inflammation and its role in the progression of macular degeneration.

Inflammasomes are multiprotein complexes that lead to the proteolytic activation of proinflammatory IL-1β and IL-18 through the catalytic activity of caspase-1. Canonical inflammasome activation is initiated by cytosolic pattern recognition receptors (PRRs) when exposed to specific triggers, either microbe-derived pathogen-associated molecular patterns (PAMPs) or host-derived danger-associated molecular patterns (DAMPs). These PRRs include the family of NOD-like receptors, to which NLRP3 belongs.

Recent studies implicated canonical inflammasome activation in age-related macular degeneration (AMD) pathogenesis. However, these studies have focused on the NLRP3 inflammasome and did not consider a potential contribution of other PRRs for inflammasome activation in AMD. The reason for this very narrow focus on NLRP3 as a PRR that initiates inflammasome activation in AMD is that various stimuli that are well-established risk factors for AMD, including increased oxidative stress or lipid accumulations, are known activators of the NLRP3 inflammasome. This has led to the assumption that AMD risk factors promote NLRP3 inflammasome activation, which further exacerbates AMD pathologies through activation of proinflammatory cytokines, such as IL-1β that is known to stimulate inflammatory angiogenesis.

Key open questions are (1) whether NLRP3 inflammasome activation mainly in retinal pigment epithelium (RPE) or rather in non-RPE cells promotes choroidal neovascularization (CNV), (2) whether inflammasome activation in CNV occurs via NLRP3 or also through NLRP3-independent mechanisms, and (3) whether complement activation induces inflammasome activation in CNV.

Here we show in a neovascular AMD mouse model that NLRP3 inflammasome activation in non-RPE cells but not in RPE cells promotes CNV. We demonstrate that both NLRP3-dependent and NLRP3-independent inflammasome activation mechanisms induce CNV. Finally, we find that complement and inflammasomes promote CNV through independent mechanisms. Our findings uncover an unexpected role of non-NLRP3 inflammasomes for CNV and suggest that combination therapies targeting inflammasomes and complement may offer synergistic benefits to inhibit CNV.

Cisd2 in Aging and Exercise
https://www.fightaging.org/archives/2020/12/cisd2-in-aging-and-exercise/

This open access paper provides an overview of Cisd2, one of many genes for which upregulation extends life and improves health in mice. This is potentially mediated by its effects on the cellular maintenance processes of autophagy and on mitochondrial function. It reduces the loss of mitochondrial function that occurs in aging, perhaps through improved removal of damaged mitochondria via mitophagy, but perhaps through other mechanisms. The researchers show that Cisd2 expression is upregulated as a result of exercise, making it plausibly a part of the regulatory system by which the response to exercise can improve health and slow the progression of aging.

Cisd2 (CDGSH Iron Sulfur Domain 2) is an oxidative stress-sensitive gene, the expression of which is able to prolong the lifespan in mice. Cisd2 loss-of-function mice exhibit premature aging phenotypes and have a shortened lifespan. Conversely, Cisd2 transgenic mice not only are longer lived (both males and females), they also have a healthier physical condition, such as better fur function, increased muscle strength and improved cardiac function. The Cisd2 protein has been localized to mitochondria, mitochondria-associated membrane (MAM) and the endoplasmic reticulum (ER), and is involved in calcium homeostasis. We have demonstrated using aged mice that maintenance of the expression level of Cisd2 sustains metabolic activity, ameliorates aging-associated mitochondrial dysregulation, reduces DNA damages and improves the calcium imbalance within skeletal muscles, liver, and heart. Taken together, Cisd2 is a lifespan regulator and its expression level seems to be a critical factor in relation to prolong healthspan.

Cisd2 and exercise have both been reported to contribute to an extended lifespan and to improve healthspan. A recent report has shown that the protein levels of Cisd1 and Cisd2 in skeletal muscle and white adipose tissue are increased approximately 1.5-fold and 1.2-fold after 4 weeks of voluntary excise in mice. The authors also observed that there were significant increases in the levels of multiple mitochondrial proteins, which agrees with our previous discovery of increased mitochondrial number in the muscle of Cisd2 transgenic mice compared to their wild type cohorts. To examine the transcription of Cisd2 in real-time, here we have generated a Cisd2 reporter transgenic mouse that carries luciferase as the reporter. The Cisd2-Luciferase reporter mice were trained on a treadmill for 56 days. It was found that a drastic enhancement in Cisd2 transcription was able to be observed. The most intense signal was observed at the abdomen, with the thymus showing the next largest increase in signal. A moderately increase in signal was also observed in forelimbs and hindlimbs.