Fight Aging!

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Contents

• Elastin Fragmentation and the Elastin Receptor Complex in Aging Blood Vessels
• Mitochondrial DNA Mutation as a Contributing Cause of Aging, and the Prospects for Therapies
• Reviewing the Mechanisms that Allow Senescent Cells to Resist Apoptosis
• The Interaction Between Metabolism and Stem Cell Aging
• The Role of Mitochondrial DNA Mutation in Aging Remains Much Debated
• Targeting Inflammasomes to Reduce Age-Related Systemic Inflammation
• Further Exploration of In Vivo Reprogramming in Mice
• Cell Reprogramming via RNA Therapies
• DLX2 Reprograms Astrocytes to Produce Neurons
• Animal Data for Life Extension via GlyNAC Supplementation
• Treating Obstructive Sleep Apnea Reduces Epigenetic Age Acceleration
• Epigenetic Aging Halts During Hibernation in Marmots
• Polarization of Microglia to M2 as a Basis for Treating Neurodegenerative Conditions
• Physical Activity Improves Brain Function in Later Life
• Variations in Biological Age Across Organs in Younger Individuals

Elastin Fragmentation and the Elastin Receptor Complex in Aging Blood Vessels
https://www.fightaging.org/archives/2022/03/elastin-fragmentation-and-the-elastin-receptor-complex-in-aging-blood-vessels/

Elastin is a vital component of the complex structure of the extracellular matrix in flexible, elastic tissues, such as skin and blood vessel walls. It is the extracellular matrix that determines physical tissue properties, such as strength, elasticity, and so forth. This structure becomes disarrayed with age for a variety of reasons: photoaging that breaks down molecules or encourages alterations; cross-linking between molecules that restricts their range of motion; changes in the behavior of cells that maintain the structure.

Today's open access paper looks at a different aspect of this issue. The researchers discuss what happens to the debris from elastin that is broken down, and how cells react to this signal of damage. Unfortunately, further harms resulting from initial damage are very much a characteristic of aging. It isn't just that molecules become broken, but cells then change their behavior as a result, often in maladaptive ways.

Restoration of the extracellular matrix in aged tissues is one of the areas of rejuvenation research in which there is little forward motion, and there are too many goals here for which there are, as of yet, no good, obvious approaches to therapy ready to move into preclinical development. Cross-links can in principle be broken, but only one biotech company is working on a plausible approach applicable to the whole body at present. Cells can be reprogrammed to more youthful function, but it is unclear as to whether that will result in improved maintenance of skin extracellular matrix in the context of damage and disarray that is not present in youth. Cells can be coerced into elastin deposition, such as via minoxidil use, but there are no good ways of doing this systemically that do not result in untenable side-effects. And so forth. More attention is needed in this part of the field.

The Elastin Receptor Complex: An Emerging Therapeutic Target Against Age-Related Vascular Diseases

Aging is accompanied by changes in vascular structure and function, especially in the large arteries. Due to their elasticity and resilience capacities, the concentric elastic lamellae of the aorta play a pivotal role in reducing the high systolic pressure at the outlet the heart. In other words, elastic lamellae stretch during cardiac ejection phases allowing the radius of the aorta to increase and to convert the pulsatile flow leaving the heart into a continuous flow in arteries. With age, these elastic lamellae exhibit wear characterized by zones of rupture. This leads to loss of elasticity and progressive hardening of the aorta and release of elastin-derived peptides (EDPs) in the circulating blood.

Elastic fibers fragmentation and release of elastin degradation products, also known as elastin-derived peptides (EDPs), are typical hallmarks of aged conduit arteries. Along with the direct consequences of elastin fragmentation on the mechanical properties of arteries, the release of EDPs has been shown to modulate the development and/or progression of diverse vascular and metabolic diseases including atherosclerosis, thrombosis, type 2 diabetes, and nonalcoholic steatohepatitis.

Most of the biological effects mediated by these bioactive peptides are due to a peculiar membrane receptor called elastin receptor complex (ERC). This heterotrimeric receptor contains a peripheral protein called elastin-binding protein, the protective protein/cathepsin A, and a transmembrane sialidase, the neuraminidase-1 (NEU1). In this review, after an introductive part on the consequences of aging on the vasculature and the release of EDPs, we describe the composition of the ERC, the signaling pathways triggered by this receptor, and the current pharmacological strategies targeting ERC activation.

Mitochondrial DNA Mutation as a Contributing Cause of Aging, and the Prospects for Therapies
https://www.fightaging.org/archives/2022/03/mitochondrial-dna-mutation-as-a-contributing-cause-of-aging-and-the-prospects-for-therapies/

Mitochondria are the power plants of the cell. They are deeply integrated into many core cellular processes, but their primary responsibility is to generate adenosine triphosphate (ATP), an energy store molecule used to power cellular activities. Mitochondria are the evolved descendants of ancient symbiotic bacteria, and carry a small remnant genome encoding a handful of genes vital to ATP production. Each cell contains hundreds of mitochondria. Worn mitochondria are destroyed by the quality control process of mitophagy, while other mitochondria replicate much like bacteria to make up numbers.

The mitochondrial genome is less well protected than the nuclear genome, and some forms of mutational damage can cause mitochondria to become both dysfunctional and in some way able to outcompete their peers, either resistant to mitophagy or better able to replicate, or both. It is an open question as to how much of the age-related decline in mitochondrial function is a result of stochastic mitochondrial DNA damage, both modest and severe, versus the characteristic epigenetic changes of age that impair mitophagy and mitochondrial function in other ways.

To answer that question, it would be necessary to repair mitochondrial DNA damage in isolation of other processes. This is the goal of the MitoSENS project at the SENS Research Foundation, and their approach is to place mitochondrial genes into the nuclear genome, suitably altered such that the proteins produced are transported into the mitochondria where they are needed. This has been achieved for a few of the necessary genes, and if achieved for all it would, in principle, make mutational damage to the mitochondrial genome a non-event. It would then be possible to observe the outcome of this intervention in animal models, to see how much of a gain in health and life span was achieved.

SRF Publication on Mitochondrial Genome in Aging and Disease and the Future of Mitochondrial Therapeutics

The MitoSENS team continue to make progress in developing rejuvenation biotechnologies to prevent, reverse, or remove mutant mitochondria from aging cells. The center of their work continues to be allotopic expression, placing "backup copies" of the mitochondrial DNA into the nucleus, which would supply the proteins that mutation-bearing mitochondria can no longer produce for themselves, and thus keep them (and our cells) functioning normally over time. The MitoSENS team's 2016 breakthrough with allotopic expression of the mitochondrial genes ATP8 and ATP6 marked an important milestone. Since then, they've continued to work to advance the field, including showing how the distinct way that mitochondria encode genetic instructions into their DNA can be better "translated" for use in the nuclear genome, resulting in robust but transient protein production for all of the 13 genes. The team is now working on creating stable expression for these proteins and in achieving functional relevance.

In a new peer-reviewed scientific paper, the MitoSENS team gives an overview of where the field is at and the obstacles that are holding us back. They first highlight some of the drugs, supplements, and stem cell treatments that have been tried and failed (or only had modest effects) to treat inherited mitochondrial diseases. But then they get to the heart of the matter: the challenges that now need to be overcome in order to move allotopic expression towards the clinic. These include mastering the targeting of allotopically-expressed proteins to the right place in the mitochondria; modifying either the protein products themselves or the way we deliver them to prevent these proteins being incorrectly assembled in places other than their intended location; and controlling the level of protein production and its regulation by the cell (since too little protein production wouldn't have a therapeutic effect, and too much might be harmful).

The Mitochondrial Genome in Aging and Disease and the Future of Mitochondrial Therapeutics

Mitochondria are at the interface between several critical functions in the cell, including metabolism, signaling, and immune surveillance. Advances in our understanding of mitochondrial biology and function have illuminated the role of mitochondrial dysfunction in pathology and aging. The unique properties of the organelle predispose its genome to mutations and compromised functions leading to several diseases collectively called mitochondriopathies. Researchers have exploited various technologies, including small-molecule drugs, allogeneic hematopoietic stem cell transplantation, mitochondrial replacement, as well as gene-editing tools, such as nucleic acid therapy and mitochondria-targeted restriction endonucleases, in alleviating these diseases. While modulating organelle function using small molecules is attractive at the outset and benefits from ease of administration, few leads have been identified that hold curative promise, and this treatment modality leaves the root cause of pathology unaddressed.

Recent gene editing approaches, such as targeted restriction endonucleases and base-editing enzymes show promise, though they are limited by their narrow specificity and may require patient-to-patient customization. Gene therapy in the form of allotopic expression has received the most attention for its potential as a robust method for reversing the symptoms of mitochondrial DNA (mtDNA) mutations. Synchronizing allotopic expression for the 13 mtDNA genes with the nuclear-mitochondrial transcription and translation machinery can overcome limitations in competing with pre-existing mutant proteins in the respiratory chain complexes due to heteroplasmy, a condition commonly observed in known mtDNA pathologies. Furthermore, advances in technologies capable of inserting large DNA cargos into the nuclear genome, such as safe harbor expression or mini chromosomes, will allow for testing multiple allotopic genes simultaneously. While validating the technology in vivo has its challenges due to inadequate animal models for all the protein coding genes, the ease of generating precise human iPSCs, particularly from patients with specific mtDNA mutations, may allow us to test these gene therapy approaches on a case-by-case basis in vitro.

Reviewing the Mechanisms that Allow Senescent Cells to Resist Apoptosis
https://www.fightaging.org/archives/2022/03/reviewing-the-mechanisms-that-allow-senescent-cells-to-resist-apoptosis/

A large portion of research into senescent cells in the context of degenerative aging is focused on how these cells fail to destroy themselves. Senescent cells are primed to enter the programmed cell death process of apoptosis, but various mechanisms hold this off. Sabotaging some of those mechanisms is an effective way to clear a sizable fraction of senescent cells in many old tissues, as demonstrated by the initial small molecule senolytic treatments, such as the dasatinib and quercetin combination.

As the authors of today's open access paper note, the fact that these apoptosis-inducing senolytics are only partially effective raises questions about the diversity of anti-apoptosis mechanisms and varieties of senescent cell. It is a fertile area of research, in which scientists are uncovering new ways to provoke senescent cells into apoptosis, with different degrees of effectiveness on senescent cells of different origins. There are many more areas of cellular biochemistry yet to explore, and likely many more effective senolytic small molecules yet to be identified.

Why Senescent Cells Are Resistant to Apoptosis: An Insight for Senolytic Development

Cellular senescence is a process that leads to a state of irreversible growth arrest in response to a variety of intrinsic and extrinsic stresses. Initially, the phenomenon was found when cultured cells were shown to undergo a limited number of cell divisions in vitro. Cellular senescence is different from cell quiescence which represents a transient and reversible cell cycle arrest. Cellular senescence can be a physiologically or pathologically relevant program depending on the specific situation. It normally functions as a vital tumor suppressive mechanism and also plays an important role in tissue damage repair. However, senescent cells (SnCs) have been implicated in various age-related diseases.

Accordingly, selective elimination of SnCs has been exploited as a novel strategy to treat the diseases. In addition, SnCs have also been implicated in infectious diseases. For example, virus infection can induce cellular senescence, which was found to be a pathogenic trigger of cytokine escalation and organ damage, and recently found to be associated with the COVID-19 severity in the elderly. Clearance of virus-induced SnCs was considered as a novel treatment option against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and perhaps other viral infections.

One of the characteristics of SnCs is their ability to resist apoptosis. Until now, small molecules that can selectively kill SnCs, termed senolytics, were developed to target the proteins in the SnC anti-apoptotic pathways (SCAPs). However, due to the high heterogeneity in gene expression and their diverse origins, SnCs may use different SCAPs to maintain their survival, making it difficult to use a single senolytic to kill all types of SnCs. Although significant progresses on the development of senolytics have been made, some proteins involved in the SCAPs have been overlooked, their potential of being senolytic targets have not been investigated. Therefore, gaining more insights into the apoptosis-resistant mechanism of SnCs may greatly help to design or screen more effective senolytics that can be used to treat SnC-associated disorders.

In this review, we discussed the latest research progresses and challenge in senolytic development, described the significance of regulation of senescence and apoptosis in aging, and systematically summarized the SCAPs involved in the apoptotic resistance in SnCs.

The Interaction Between Metabolism and Stem Cell Aging
https://www.fightaging.org/archives/2022/03/the-interaction-between-metabolism-and-stem-cell-aging/

In today's open access paper, researchers discuss the influence of metabolism on the aging of stem cells. Stem cells maintain tissue by providing a supply of daughter somatic cells to replace losses. Animals have evolved to minimize the risk of cancer by limiting the ability of near all cells to replicate. Somatic cells operate under the Hayflick limit, driven by loss of telomere length with each cell division, leading to senescence or self-destruction when telomeres are short. Stem cells use telomerase to maintain long telomeres and thus continually produce replacement somatic cells with long telomeres.

Unfortunately stem cell activity is reduced with advancing age, leading to a reduced production of somatic cells and the steady decline of tissue maintenance and function. The causes of this are complex, even while being energetically explored by a large portion of the broader research community. At the very high level, damage to stem cells, damage to the supporting cells of the stem cell niche, and changes in the signaling environment that cause stem cells to become more quiescent, even if undamaged. The balance of these issues appears different for different stem cell populations. Aged muscle stem cells appear functional when given a youthful environment, for example.

Metabolic Regulation of Stem Cells in Aging

Somatic stem cells integrate critical environmental inputs that inform decisions on self-renewal, differentiation, and subsequent tissue turnover. Aging is a risk factor for many diseases, and recent studies are starting to uncover the molecular mechanisms of how environmental factors, such as diet, can influence stem cell behavior over time. With aging, many adult stem cell populations accumulate damage and become impaired in their function, which leads to inefficient tissue repair and may predispose to age-associated diseases such as cancer. Although numerous studies have shown that dietary restriction confers beneficial effects on overall organismal lifespan, we are just starting to uncover the complexities of metabolic dependencies in stem cells and how the availability of specific nutrients are sensed within a heterogeneous population of stem, progenitor, and niche cells and communicated between each other. The advent of new single cell technologies has already begun to enhance our ability to resolve the complex metabolic heterogeneity and interactions that exist in certain niches, such as in the gut crypt and bone marrow.

Recent studies using single cells technologies have also revealed that seemingly uniform, terminally differentiated cells in the liver and intestinal villus have specific transcriptional metabolic profiles that are driving cell function. These differences among hepatocytes and enterocytes were largely influenced by location, proximity to nutrients, and oxygen supply within their respective tissues. In the upcoming years, as multiple single cell -omic technologies advance and integrate, we will begin to see more advanced tissue maps of transcriptional, proteomic, and metabolomic signatures of stem and progenitor cells and their corresponding niches, both under homeostatic conditions as well as during aging and other pathological states. These types of studies will also likely layer dietary patterns with other environmental factors to expand our understanding of how nutrients and systemic metabolism impact tissue homeostasis. Finally, the constant improvement and engineering of primary 3D organoid cultures will allow us to more precisely examine intrinsic and extrinsic age-associated changes, as well as measure the activity of metabolic pathways, in response to defined nutrient conditions. We will be able to incorporate and study other signals in these systems, such as cytokines, hormones, and microbial metabolites. All of these advances will conceivably lead to better strategies and therapies for tissue repair with age, while carefully avoiding interventions that may accelerate age-dependent diseases such as cancer.

The Role of Mitochondrial DNA Mutation in Aging Remains Much Debated
https://www.fightaging.org/archives/2022/03/the-role-of-mitochondrial-dna-mutation-in-aging-remains-much-debated/

Mitochondria are the power plants of the cell, deeply integrated into many core cellular processes, but most importantly, responsible for generating the energy store molecule adenosine triphosphate (ATP), used to power cellular processes. Mitochondria are descended from ancient symbiotic bacteria, and act like bacteria in many ways, fusing and dividing, and passing around component parts promiscuously. Every cell contains a herd of hundreds of these organelles, monitored by quality control processes that destroy worn mitochondria in order to maintain overall function.

Importantly, mitochondria contain their own small circular genome. Mitochondrial DNA is less well protected than that of the cell nucleus, and more prone to stochastic mutational damage. There are clearly types of mitochondrial DNA damage, large deletion mutations that remove genes essential to the electron transport chain, central to mitochondrial function, that result in pathological damage to cells. But mitochondria throughout the body undergo a declining function with age that seems to have more to do with altered dynamics and the failure of mitophagy to keep up with worn mitochondria, a consequence of age-related changes in gene expression of crucial proteins.

Yet mutational damage other than deletions, such as point mutations, is widespread across mitochondria in aged tissues. To what degree is this stochastic mutational damage important as a contribution to age-related mitochondrial decline? Is it as relevant as loss of mitophagy? Unimportant in comparison? Today's open access paper reviews what is known on this topic. It is a complicated situation, still much debated, with mixed evidence on all sides.

The Complicated Nature of Somatic mtDNA Mutations in Aging

With only a few noted exceptions, mitochondria are the main source of cellular energy in eukaryotes. These organelles process dietary reducing equivalents and oxygen through the electron transport chain (ETC) to produce ATP via oxidative phosphorylation (OXPHOS). Mitochondria are involved in other important cellular functions. To varying extents, different cell types rely on these different functions, which, in turn, determines their intracellular localization, dynamics, number, and respiratory flux. As organisms age, these different mitochondrial processes degrade to differing extents and in tissue specific ways. A lingering question in the field of aging biology concerns the source of this dysfunction.

As a consequence of an endosymbiotic event ∼2 billion years ago that gave rise to mitochondria, these organelles have retained a small rudimentary genome that, in animals, is comprised of a circular double-stranded DNA molecule (mtDNA) present in dozens to thousands of copies per cell. The relatively small genome is extremely compact and encodes a total of 37 genes: 22 tRNAs, two mitochondrial ribosomal RNAs, and 13 peptides that comprise essential components of the ETC. As such, proper maintenance of the genetic information is essential for energy production and therefore maintaining cell homeostasis. One long-standing hypothesis in aging research is that the loss of genetic information encoded by the mtDNA is an important driver of aging.

With limited DNA repair capacity and higher replicative index, mtDNA has a substantially higher de novo mutation rate compared to nuclear DNA. The mitochondrial genome is maternally inherited, with most mtDNA within a cell and organism being an exact copy of the original maternal mtDNA pool, a phenomenon known as homoplasmy. However, mtDNA is susceptible to mutations within the germline, which can result in a number of devastating maternally inherited diseases. In addition to causing overt disease, mtDNA mutations can be present at lower levels, a condition known as heteroplasmy. The heteroplasmic allele fraction can range from very low levels to near homoplasmy and can be inherited or occur de novo within somatic tissues during aging and development.

Because of the multi-copy nature of mtDNA, it is estimated that the phenotypic threshold for pathogenic heteroplasmies is ∼60-90% of mitochondrial genomes within a cell. To add more complexity to the condition of heteroplasmy, the occurrence and frequency of mtDNA mutations may have different outcomes depending on the timing of their occurrence, the specific tissue in which they arise, and the total mtDNA content of the cell. Despite decades of study, the complex nature of mitochondrial genetics has made the exact role of somatic mtDNA mutations in aging difficult to discern.

In this review, we focus on the complicated observational and experimental evidence suggesting that, at least in some capacity, somatic mtDNA mutations are involved in the aging process with an emphasis of when, where, and how these mutations arise during aging. Additionally, we highlight current limitations in our knowledge and critically evaluate the controversies stemming from these limitations. Lastly, we highlight new and emerging possibilities that offer potential ways forward to increase our understanding of somatic mtDNA in the aging process.

Targeting Inflammasomes to Reduce Age-Related Systemic Inflammation
https://www.fightaging.org/archives/2022/03/targeting-inflammasomes-to-reduce-age-related-systemic-inflammation/

Therapies capable of reducing systemic inflammation are at present quite blunt, largely interfering in signaling that is needed for necessary short-term inflammation as well as that involved in excessive, unresolved inflammation. This has negative effects on immune function, leading to vulnerability to pathogens, for example. There is the hope that targeting the function of inflammasomes, protein complexes involved in the mechanisms of the immune response, will prove to be somewhat more selective for unwanted inflammation. This is likely not the final destination for the desired goal of only eliminating excess inflammation, however.

Aging is a significant risk factor for the development of neurodegenerative diseases such as Alzheimer's disease (AD) and Parkinson's disease (PD). Inflammation also plays a role in the development of neurodegenerative diseases. Inflammaging, a low level of chronic inflammation that occurs due to old age, is a normal part of the aging process. It has been shown that the inflammasome contributes to age-related inflammation and development of neurodegenerative diseases. Thus, the inflammasome is a potential therapeutic target to ameliorate inflammaging and to prevent and/or treat neurodegenerative diseases.

In this study, we show the anti-inflammatory effects of anti-ASC, a monoclonal antibody against ASC, in the cortex of aged mice. We found that protein levels of IL-1β, ASC, caspase-1, and NLRP1 were significantly elevated in the cortex of aged mice and that anti-ASC treatment inhibits the protein levels of these inflammasome signaling proteins. ASC speck formation was examined and protein levels of ASC specks were increased in old age and anti-ASC inhibits the formation of ASC specks. Moreover, we investigated the protein levels of the non-canonical inflammasome proteins caspase-8 and caspase-11. We found that caspase-8 was also elevated in the cortex of aged mice and that anti-ASC decreased the protein levels of this protein. However, we did not see any significant differences between young and aged mice in the protein levels of caspase-11.

Together, these results indicate that a novel NLRP1-caspase-8 non-canonical inflammasome is present in the cortex of mice and that anti-ASC is a potential therapeutic to decrease inflammasome-mediated inflammaging in the central nervous system.

Further Exploration of In Vivo Reprogramming in Mice
https://www.fightaging.org/archives/2022/03/further-exploration-of-in-vivo-reprogramming-in-mice/

Researchers are expanding their explorations of cellular reprogramming applied to living animals, delivering Yamanaka factors as a gene therapy. There are in principle ways to balance this sort of approach in order to minimize the conversion of somatic cells into induced pluripotent stem cells, and thus the risk of cancer, while maximizing the epigenetic rejuvenation and restoration of mitochondrial function that occurs as an early part of the reprogramming process.

Forcing cells in aged tissues to act as though they are present in youthful tissues is expected to produce meaningful benefits to health, and indeed has done so in some animal studies. It cannot fix issues related to metabolic waste that cannot be cleared effectively by even a young physiology, or issues related to stochastic DNA damage, but the hope is that the issues of aging that reprogramming can effectively address will make this a useful approach to the treatment of aging as a medical condition.

In 2016, researchers reported for the first time that they could use the Yamanaka factors to counter the signs of aging and increase life span in mice with a premature aging disease. More recently, the team found that, even in young mice, the Yamanaka factors can accelerate muscle regeneration. Following these initial observations, other scientists have used the same approach to improve the function of other tissues like the heart, brain, and optic nerve, which is involved in vision.

In the new study, researchers tested variations of the cellular rejuvenation approach in healthy animals as they aged. One group of mice received regular doses of the Yamanaka factors from the time they were 15 months old until 22 months, approximately equivalent to age 50 through 70 in humans. Another group was treated from 12 through 22 months, approximately age 35 to 70 in humans. And a third group was treated for just one month at age 25 months, similar to age 80 in humans. "What we really wanted to establish was that using this approach for a longer time span is safe. Indeed, we did not see any negative effects on the health, behavior, or body weight of these animals."

When the researchers looked at normal signs of aging in the animals that had undergone the treatment, they found that the mice, in many ways, resembled younger animals. In both the kidneys and skin, the epigenetics of treated animals more closely resembled epigenetic patterns seen in younger animals. When injured, the skin cells of treated animals had a greater ability to proliferate and were less likely to form permanent scars - older animals usually show less skin cell proliferation and more scarring. Moreover, metabolic molecules in the blood of treated animals did not show normal age-related changes.

This youthfulness was observed in the animals treated for seven or 10 months with the Yamanaka factors, but not the animals treated for just one month. What's more, when the treated animals were analyzed midway through their treatment, the effects were not yet as evident. This suggests that the treatment is not simply pausing aging, but actively turning it backwards - although more research is needed to differentiate between the two.

Cell Reprogramming via RNA Therapies
https://www.fightaging.org/archives/2022/03/cell-reprogramming-via-rna-therapies/

Gene therapies delivering mRNA produce a temporary production of proteins. An RNA molecule acts as a blueprint for a ribosome to assemble many copies of a specific protein, but this doesn't last long, and a few days of protein expression from a single treatment is a reasonable expectation in practice. This make RNA therapies suitable to produce partial reprogramming in an animal or patient. The Yamanaka factors are delivered for a long enough period of time to rejuvenate epigenetic patterns and restore mitochondrial function, but (hopefully) not long enough to convert any meaningful number of somatic cells into induced pluripotent stem cells. The former outcome is desirable, while the latter outcome would damage tissue function and create the risk of cancer.

Induced pluripotent stem cells (iPSCs) reprogrammed from replicative senescing or centennial cells had restored the telomere and mitochondrial functions with a gene expression profile similar to embryonic stem cells (ESCs). This and other avenues of research confirm that cellular age can be reversed. These seminal results led the scientific community to ask whether cellular rejuvenation due to reprogramming could take place in vivo.

To answer this question, researchers generated transgenic mouse models, expressing Yamanaka factors (OSKM) under the control of doxycycline. Strikingly, they observed the emergence of teratomas in several organs, thus demonstrating the feasibility of in vivo reprogramming. However, to prevent deterioration related to aging or to rejuvenate the organism, it is important not to generate fully dedifferentiate cells, as this leads to a deterioration of the animal's health or tumor formation. Consequently, it was judicious to think to trigger the reprogramming process and stop it before obtaining pluripotent cells, hoping that it might erase cellular aging marks instead of favoring senescence. Researchers envisioned such a strategy and proposed a protocol to induce partial reprogramming in a homozygous progeria transgenic mouse model. They induced OSKM expression for 2 days per week during the lives of the animals with doxycycline and observed a significant increase in the lifespan of these animals, as well as the improvements in age-related hallmarks.

The use of strategies based on mRNA to express the factors needed for cell reprogramming has rapidly emerged as a promising technology to achieve the goal of partial reprogramming. Hence, in this review, after a brief revisiting of the state-of-the-art various technologies, we will focus on methods based on RNA that induce the conversion of somatic cells into pluripotent cells. We will frame these technological advances in the context of recent cutting-edge approaches to reverse age-related cell and tissue phenotypes by reprogramming them towards pluripotency.

DLX2 Reprograms Astrocytes to Produce Neurons
https://www.fightaging.org/archives/2022/03/dlx2-reprograms-astrocytes-to-produce-neurons/

One of the potential paths to regenerative therapies for the aging brain is to reprogram supporting cells to produce neurons that can then integrate into existing neural networks, a supplemental form of neurogenesis. One has to be a little cautious in reading new research on this topic, given that some past work has proven to be a dead end, the victim of difficulties in determining exactly what is going on inside the brain. Nonetheless, a number of different groups are pursuing a number of different possibilities; one might hope that at least one approach will bear fruit. The example here is at a comparatively early stage of discovery.

During development, mammalian stem cells readily proliferate to produce neurons throughout the brain and cells - called glia - that help support them. Glia help maintain optimal brain function by performing essential jobs like cleaning up waste and insulating nerve fibers. However, the mature brain largely loses that stem cell capacity. Only two small regenerative zones, or niches, remain in the adult brain, leaving it with extremely limited capacity to heal itself following injury or disease.

Looking for a way to spur this "multipotent" regeneration, researchers used a genetic engineering technique in adult mouse brains to induce astrocytes, a subset of glia, to produce different transcription factors, proteins pivotal for controlling cell identity. These experiments showed that a single transcription factor - a protein known as DLX2 - appeared to reprogram astrocytes into neural stem-like cells capable of producing neurons and multiple subtypes of glial cells.

The researchers confirmed these findings both using a technique called lineage tracing, in which they followed progeny of the altered astrocytes as they multiplied, as well as marker analysis that showed that these new cells had the expected identities of neurons or glia. Researchers suggest that DLX2 might someday be used as a tool to treat traumatic brain injuries, strokes, and degenerative conditions .

Animal Data for Life Extension via GlyNAC Supplementation
https://www.fightaging.org/archives/2022/03/animal-data-for-life-extension-via-glynac-supplementation/

GlyNAC supplementation means addition of glutathione precursors to the diet, glycine and N-acetylcysteine. Glutathione is a natural antioxidant, protective against oxidative stress and able to improve mitochondrial function. Levels of glutatione decline with age, but this can be compensated for via providing increased levels of precursor compounds that will lead to greater manufacture of glutathione. Delivering glutathione directly has been attempted, but doesn't work, for reasons that likely relate to how glutathione ends up in the parts of the cell where it does its work. The interesting data is of course the human data, showing a reduction in chronic inflammation and improvements in other markers, but here find evidence for life extension in mice resulting from this approach.

Determinants of length of life are not well understood, and therefore increasing lifespan is a challenge. Cardinal theories of aging suggest that oxidative stress (OxS) and mitochondrial dysfunction contribute to the aging process, but it is unclear if they could also impact lifespan. Glutathione (GSH), the most abundant intracellular antioxidant, protects cells from OxS and is necessary for maintaining mitochondrial health, but GSH levels decline with aging. Based on published human studies where we found that supplementing glycine and N-acetylcysteine (GlyNAC) improved/corrected GSH deficiency, OxS, and mitochondrial dysfunction, we hypothesized that GlyNAC supplementation could increase longevity.

We tested our hypothesis by evaluating the effect of supplementing GlyNAC vs. placebo in C57BL/6J mice on (a) length of life; and (b) age-associated GSH deficiency, OxS, mitochondrial dysfunction, abnormal mitophagy and nutrient-sensing, and genomic damage in the heart, liver, and kidneys. Results showed that mice receiving GlyNAC supplementation (1) lived 24% longer than control mice; (2) improved/corrected impaired GSH synthesis, GSH deficiency, OxS, mitochondrial dysfunction, abnormal mitophagy and nutrient-sensing, and genomic damage. These studies provide proof-of-concept that GlyNAC supplementation can increase lifespan and improve multiple age-associated defects. GlyNAC could be a novel and simple nutritional supplement to improve lifespan and healthspan, and warrants additional investigation.

Treating Obstructive Sleep Apnea Reduces Epigenetic Age Acceleration
https://www.fightaging.org/archives/2022/03/treating-obstructive-sleep-apnea-reduces-epigenetic-age-acceleration/

Now that cost-effective epigenetic age assessment is a going concern, we will see all sorts of interesting correlations, such as the one noted here in patients with obstructive sleep apnea, before and after treatment. Since it remains unclear as to what exactly is being measured by epigenetic age, which aspects of aging and consequent metabolic dysfunction contribute to the outcome, a good deal of speculation is involved when thinking about why and how what is known of the consequences of sleep apnea relates to what is known of degenerative aging.

Obstructive sleep apnea (OSA) affects 22 million people in the U.S. and is linked to a higher risk of hypertension, heart attacks, stroke, diabetes, and many other chronic conditions. Age acceleration testing involves a blood test that analyzes DNA and uses an algorithm to measure a person's biological age. The phenomenon of a person's biological age surpassing their chronological age is called "epigenetic age acceleration", and is linked to overall mortality and to chronic diseases.

Researchers studied 16 adult nonsmokers who were diagnosed with OSA and compared them to eight control subjects without the condition to assess the impact of OSA on epigenetic age acceleration over a one-year period. After a baseline blood test, the OSA group received continuous positive airway pressure (CPAP) treatment for one year before being tested again.

"Our results found that OSA-induced sleep disruptions and lower oxygen levels during sleep promoted faster biological age acceleration compared to the control group. However, the OSA patients who adhered to CPAP showed a deceleration of the epigenetic age, while the age acceleration trends did not change for the control group. Our results suggest that biological age acceleration is at least partially reversible when effective treatment of OSA is implemented."

Epigenetic Aging Halts During Hibernation in Marmots
https://www.fightaging.org/archives/2022/03/epigenetic-aging-halts-during-hibernation-in-marmots/

Continuing the recent run of interesting observations arising from the ability to assess epigenetic age, researchers here show that a hibernating species shows no uptick in epigenetic age over the period of hibernation. The metabolism of hibernation has been a topic of minor interest for some years in the context of aging and mechanisms of aging. The metabolic state of hibernation seems favorable in many of the same ways that are observed in states like calorie restriction, but perhaps for distinct reasons.

Yellow-bellied marmots are able to virtually halt the aging process during the seven to eight months they spend hibernating in their underground burrows. The study, the first to analyze the rate of aging among marmots in the wild, shows that this anti-aging phenomenon kicks in once the animals reach 2 years old, their age of sexual maturity. The researchers studied marmot blood samples collected over multiple summer seasons in Colorado, when the animals are active above ground, to build statistical models that allowed them to estimate what occurred during hibernation. They assessed the biological aging of the marmots based on what are known as epigenetic changes - hundreds of chemical modifications that occur to their DNA.

This process, the researchers said, helps explain why the average life span of a yellow-bellied marmot is longer than would be expected from its body weight. Hibernation, an evolutionary adaptation that allows animals to survive in harsh seasonal environments where there is no food and temperatures are very low, is common among smaller mammals, like marmots. The marmots' hibernation alternates between periods of metabolic suppression that last a week or two and shorter periods of increased metabolism, which generally last less than a day. During metabolic suppression, their breathing slows and their body temperature drops dramatically.

All of these hibernation-related conditions - diminished food consumption, low body temperature and reduced metabolism - are known to counter the aging process and promote longevity. This delayed aging is likely to occur in other mammals that hibernate, because the molecular and physiological changes are similar.

Polarization of Microglia to M2 as a Basis for Treating Neurodegenerative Conditions
https://www.fightaging.org/archives/2022/03/polarization-of-microglia-to-m2-as-a-basis-for-treating-neurodegenerative-conditions/

A good deal of evidence points to increased inflammatory activation of microglia in the brain, and consequent chronic inflammation of brain tissue, as an important component of neurodegenerative conditions. Some of these inflammatory microglia are senescent, and their clearance has been shown to be helpful in animal models, but the broader problem is an imbalance between pro-inflammatory M1 microglia and anti-inflammatory M2 microglia. A number of options exist if the goal is to shift the balance, from clearance and regeneration of all microglia via CSFR1 inhibition to various mechanisms that might encourage microglia to preferentially adopt the M2 state.

Microglia-mediated neuroinflammation is a common feature shared by various neurodegenerative diseases. Neuroinflammatory includes microglial activation, and microglia could polarize into either M1 pro-inflammatory phenotype or M2 anti-inflammatory phenotype in response to different micro-environmental disturbances, which are called classical activation and alternative activation, respectively. M1 microglia release inflammatory cytokines and chemokines, resulting in inflammation and neuronal death. However, tissue maintenance and repair are associated with alternative activation of M2 microglia. M1 microglia induce inflammation and neurotoxicity, while M2 microglia induce anti-inflammatory and neuroprotection, both of which are involved in the pathogenesis of neurodegenerative diseases, therefore microglia act as a double-edged sword in neurodegenerative diseases.

It's impossible to repair or regenerate damaged neurons by current drugs nowadays once neurodegenerative diseases occur or even before the onset of diseases, but current drugs could alleviate disease-related symptoms by restricting the extent of neuroinflammation. Fortunately, the balance between microglia M1/M2 polarization has a promising therapeutic prospect in the pathogenesis of neurodegenerative diseases. However, previous studies have shown that several M1 inhibitive agents are unhelpful.

As inhibiting M1 microglia alone is not enough, promoting M2 microglia activation simultaneously might also be required for treating neurodegenerative diseases. Promoting microglia polarization shift from M1 to M2 phenotype may be a more prospective strategy in the therapy of neurodegenerative diseases. Activated microglia is also a double-edged sword in other central nervous system diseases such as ischemic stroke, spinal cord injury, and traumatic brain injury. There have been many studies about modulation of microglia polarization from M1 to M2 in these diseases, which may provide many interesting ideas in neurodegenerative diseases.

Physical Activity Improves Brain Function in Later Life
https://www.fightaging.org/archives/2022/03/physical-activity-improves-brain-function-in-later-life/

Many studies of exercise and health support the view that older people typically undertake far less exercise than they should. Exercise improves function and lowers mortality risk, and therefore the less active segment of the older population are only harming themselves. We evolved to be active throughout life, and we suffer when that is not the case. As researchers note here, the dose-response curve for exercise results in sizable benefits when moving from little exercise to some exercise, and diminishing returns with further increases. Evidence suggests that the optimal level is probably still somewhat more than the established 150 minutes per week, however.

The study followed 51 older adults, tracking their physical activity and fitness measurements. The participants performed tests specifically designed to measure cognitive functioning and underwent MRIs to assess brain functioning. They also wore a device that measured the intensity of the wearer's physical activity, number of steps taken and distance covered. The researchers assessed fitness through a six-minute walking test, during which participants walked as quickly as they could to cover the most distance possible within the time limit.

The brain is made up of a bunch of distinct networks. Different parts of the brain are active at different times. While one of these networks is active, the other should be shut off. If it's not, that's a sign that a person's brain isn't functioning as well as it should be. These networks are the key to being able to perform basic tasks in daily life, such as remembering important information and exhibiting self-control. But as people age, these tasks often become more difficult. This study was the first to examine how these networks interact with physical activity and fitness to impact how the brain functions.

"This paper is exciting because it gives us some evidence that when people whose brain networks aren't functioning optimally engage in physical activity, we see improvement in their executive function and their independence. Maybe just take the stairs on the way to work. Stand up and walk around a little bit more. That's where you get the most bang for your buck, not crazy, high-intensity exercise."

Variations in Biological Age Across Organs in Younger Individuals
https://www.fightaging.org/archives/2022/03/variations-in-biological-age-across-organs-in-younger-individuals/

Systems of measuring biological age are multiplying rapidly. There are many ways of going about this, from epigenetic clocks to weighted combinations of simple measures such as grip strength. Researchers here build their own assessments for the purpose of looking at aging in younger adults, 20s to 40s, a part of aging that is not well studied at all. The interesting outcome is that there appears to be a significant variation in assessed biological age between different organs and systems in the body. It is a little early to talk about why this arises, whether an artifact of the tools used, or reflects some underlying truth about the nature of aging.

Investigators recruited 4,066 volunteers to supply blood and stool samples and facial skin images and to undergo physical fitness examinations. The volunteers were between the ages of 20 and 45 years; 52% were female and 48% were male. "Most human aging studies have been conducted on older populations and in cohorts with a high incidence of chronic diseases. Because the aging process in young healthy adults is largely unknown and some studies have suggested that age-related changes could be detected in people as young as their 20s, we decided to focus on this age range."

In total, 403 features were measured, including 74 metabolomic features, 34 clinical biochemistry features, 36 immune repertoire features, 15 body composition features, 8 physical fitness features, 10 electroencephalography features, 16 facial skin features, and 210 gut microbiome features. These features were then classified into nine categories, including cardiovascular-related, renal-related, liver-related, sex hormone, facial skin, nutrition/metabolism, immune-related, physical fitness-related, and gut microbiome features.

Because of the difference in sex-specific effects, the groups were divided into male and female. The investigators then developed an aging-rate index that could be used to correlate different bodily systems with each other. Based on their findings, they classified the volunteers either as aging faster or aging slower than their chronological age. Overall, they discovered that biological ages of different organs and systems had diverse correlations, and not all were expected. Although healthy weight and high physical fitness levels were expected to have a positive impact, the investigators were surprised by other findings. For example, having a more diverse gut microbiota indicated a younger gut while at the same time having a negative impact on the aging of the kidneys, possibly because the diversity of species causes the kidneys to do more work.