Fight Aging! Newsletter, January 17th 2022

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  • A Simple, Sensible Position on the Treatment of Aging as a Medical Condition
  • Metabolic Defects in Myeloid Cells Contribute to the Chronic Inflammation of Aging
  • Neutrophils Provoke Damaging Inflammation and Scarring Following Heart Damage
  • The Cambrian Biopharma Approach to Obtain Regulatory Approval of Drugs to Treat Aging
  • Nanowarming of Vitrified Kidneys and Hearts
  • Metabolic Coupling in the Aging Retina
  • Age-Related Changes in Phospholipid Composition of Cell Membranes
  • Arguing for Aging of the Gut Microbiome to Worsen the Burden of Cellular Senescence
  • Comparing Some of the Most Widely Used Epigenetic Clocks
  • A Mutation Distinguishing Modern Humans from Other Primates Acts to Reduce Oxidative Stress and Inflammation
  • Life Biosciences Raises a Sizable Round of Funding
  • Incidence of Cognitive Impairment is in Decline
  • Senescent Cells Negatively Affect T Helper Cell Differentiation
  • Further Wrangling Over the Definition of Aging as a Disease
  • UV Radiation and Cross-Linking Contribute to Elastosis in Aged Skin

A Simple, Sensible Position on the Treatment of Aging as a Medical Condition

If there is to be a simple, sensible, consensus position on the treatment of aging as a medical condition, it might run something like this. (a) If our species is going to put significant time and funding into this project, then it is much better to conduct research and development programs that are capable of achieving rejuvenation, rather than those that can achieve only a slowing of aging. (b) Similarly, more rejuvenation is better than less rejuvenation. We should aim to optimize the direction of development as early as possible. (c) At present it is challenging, slow, and expensive to assess the benefits produced by an alleged rejuvenation therapy, particularly in long-lived species such as our own. (d) Thus it is important to develop the capability to assess biological age immediately before and after treatment, via robust, accurate, low-cost approaches. (e) Epigenetic, transcriptomic, and proteomic clocks offer the most likely path to such a viable assessment of biological age. (f) Developing a consensus, validated clock should be a priority alongside development of the first few potential rejuvenation therapies to have performed well to date in mice.

The authors of today's open access paper argue much along these lines. The corresponding author, Vadim Gladyshev, is actually not that optimistic about the likely pace of progress towards meaningful human rejuvenation in our lifetimes. He nonetheless has a sensible attitude towards the bigger picture, one of a network of large-scale research and development programs that will ultimately lead towards many different successful interventions targeting the processes of aging.

Despite the great promise of clocks to assess biological age, and the proliferation of such clocks discovered via machine learning approaches, this technology is not yet capable of producing unbiased measures of the effectiveness of new therapies. The challenge is that researchers as yet have little idea as to what, in detail, causes specific age-related changes in the epigenome, transcriptome, and proteome. Thus any use of a clock to assess a new approach to therapy must first be calibrated against life span studies, in mice at the very least, before we can take any of the resulting data seriously. The research community should prioritize this area of research, along with the first few candidate rejuvenation therapies likely to produce a large enough reversal of biological age to test the clocks.

Emerging rejuvenation strategies-Reducing the biological age

As the most significant risk factor for human mortality, aging leads to functional decline, increased frailty, and elevated susceptibility to chronic disease. The current strategies for human lifespan extension can be divided into three major categories: (i) those that treat direct causes of mortality, (ii) those that slow down or attenuate the biological aging process, and (iii) those that achieve rejuvenation (i.e., the reversal of aging).

The first category involves treatments for age-related diseases, such as pharmaceuticals for COVID-19 in humans or age-related cancers in mice. Antibiotics, which single-handedly shifted the main cause of death in humans and extended lifespan by several decades, also belong to this category. The second involves lifespan extension in healthy individuals, without evident age reversal. One example in this category is lifespan extension caused by mild stressors such as heat, cold, or irradiation. The third category, rejuvenation, has long been regarded as the panacea for age-related diseases, but it has previously been deemed unrealistic.

While the first two major strategies have been extensively studied, very little is known about the systemic reversal of organismal aging. This is in part due to the lack of longitudinal data and validated quantitative readouts of rejuvenation, and also by the general belief that aging is inevitable and unidirectional. However, several putative rejuvenation therapies have recently been introduced that demonstrated age reversal as measured by aging biomarkers and physiological readouts. Despite these advances, whether systemic rejuvenation can be achieved by these approaches and how they can be translated to human applications remains unclear.

Distinguishing potential rejuvenation therapies from other longevity interventions, such as those that slow down aging, is challenging, and these anti-aging strategies are often referred to interchangeably. We suggest that the prerequisite for a rejuvenation intervention is a robust, sustained, and systemic reduction in biological age, which can be assessed by biomarkers of aging, such as epigenetic clocks. We discuss known and putative rejuvenation interventions and comparatively analyze them to explore underlying mechanisms.

Metabolic Defects in Myeloid Cells Contribute to the Chronic Inflammation of Aging

Today's commentary discusses recent research into age-related changes in myeloid cell lineages of the innate immune system. These cells are produced by hematopoietic stem cells in the bone marrow, and play important roles in immune function and tissue function throughout the body. With age, hematopoiesis becomes biased towards an ever greater production of myeloid cells at the expense of other immune cells, a problematic shift. As noted in this commentary, the changes also extend to the behavior of myeloid cells, and thus to the capabilities of the immune system.

The work here pinpoints one set of changes in myeloid cells outside the brain that nonetheless negatively affects cognitive function, most likely via increased inflammatory signaling. The chronic inflammation of aging is coming to be understood as an important contribution to neurodegeneration. Inflammation is a necessary and useful aspect of our biochemistry when it is present in the short term, in response to infection and injury, for example. When sustained over the long term, however, inflammation disrupts normal tissue function throughout the body - and inflammatory signaling originating outside the brain can pass the blood-brain barrier to alter the behavior of cells in the brain.

Myeloid Metabolism as a New Target for Rejuvenation?

The immune system is drastically affected with ageing. While the adaptive immune response comprising B-cells and T-cells is diminished, the innate immune system (i.e., cells of the myeloid lineage) shows an increase in the pro-inflammatory state, also known as "inflammaging". This chronic low-inflammatory state is mainly driven by macrophages and pro-inflammatory cytokines.

Cellular metabolism has emerged as a key player in the regulation of immune function, starting already at the level of myeloid versus lymphoid lineage decision and greatly affecting cellular behaviour in the mature immune cells. Several recent studies have suggested that an altered cellular metabolism in aged macrophages might directly contribute to the pro-inflammatory signature. However, the detailed mechanisms initiating this increased inflammation with aging remain unclear.

In a recent publication, researchers have elucidated this cascade using an impressive set of in vitro and in vivo experiments in mice and in human myeloid cells. They found that aged myeloid cells have a decrease in cellular respiration and a decrease in glycolysis, suggesting that aged myeloid cells undergo a general bioenergetic failure. The proposed driving cause is the increased prostaglandin E2 (PGE2) signaling in the ageing myeloid compartment, mediated by the age-dependent upregulation of EP2, one of the four PGE2 receptors.

Conditional knockout of EP2, specifically in the myeloid cells (EP2 cKO) of aged mice proves to be an effective strategy at multiple levels. First, it rescues the expression of some of the immune factors upregulated with age, both in the plasma and in the hippocampus. Second, the loss of EP2 also reduces glycogen levels, normalizing the metabolic state and the associated mitochondrial defects observed in old macrophages. A similar effect is also mimicked by directly inhibiting GYS1. Third, strikingly, aged EP2 cKO mice appear to be completely protected from a decline in hippocampal-related memory functions with ageing.

Overall, this data supports an upstream role of peripheral myeloid cells in orchestrating the process of brain ageing, underscoring the important cross-talk between the immune and the central nervous systems.

Neutrophils Provoke Damaging Inflammation and Scarring Following Heart Damage

The heart is not a very regenerative organ. Following damage, scarring rather than reconstruction results, leading to reduced function. This contributes to the high mortality resulting from a heart attack. While preventing heart attacks is a much better goal than clearing up the damage afterwards, the research community is nonetheless very interested in understanding how to sabotage this scarring process. Interfering in the activities of immune cells has seemed a promising path forwards. Heart attacks provoke lasting inflammation, and such unresolved inflammation is disruptive of regenerative processes.

In today's research materials, scientists discuss the role of neutrophils in creating an inflammatory feedback loop between bone marrow and heart following heart injury. Suppressing this feedback loop reduces the scarring that takes place following a heart attack in mice. This sort of inappropriate immune activity may be a useful target for approaches to enhance regeneration in other tissues as well.

First-responder cells after heart attack prompt inflammation overdrive

Neutrophils are definitely a key part of the problem. In an earlier study, researchers found that heart-attack patients with higher numbers of neutrophils in their blood upon hospital admission, or even after doctors restored blood flow, had the worst outcomes. However, because neutrophils are vital to all wound healing and infection fighting, their first-responder role in heart repair cannot be bluntly targeted for elimination. Instead, the team has zeroed in on signals sent to the immune response control center - the bone marrow - that trigger ramped-up production of neutrophils.

As part of that investigation, the researchers found that the first wave of neutrophils to arrive at the damaged heart consider the injury so severe that they sacrifice themselves to prevent further damage, releasing their entire contents - including proteins called alarmins. These alarmins in turn activate sensors in a second wave of neutrophils, priming those cells for more intense action. These primed neutrophils then do something unexpected: they reverse migrate from the heart to the bone marrow and release a proinflammatory protein there, which prompts stem cells in the bone marrow to churn out even more neutrophils - all processes that perpetuate inflammation at a time when it's no longer needed for heart repair.

In the most recent paper, experiments in mice using genetic techniques or drugs uncovered at least two potential targets to consider for intervention: limiting the primed neutrophils' reverse migration or suppressing neutrophils' release of the proinflammatory protein in the bone marrow. The studies showed that successful inhibition of either mechanism led to better cardiac outcomes and less scarring in the mice.

Retention of the NLRP3 Inflammasome-Primed Neutrophils in the Bone Marrow Is Essential for Myocardial Infarction-Induced Granulopoiesis

Acute myocardial infarction (MI) results in overzealous production and infiltration of neutrophils to the ischemic heart. Using a combination of time-dependent parabiosis and flow cytometry techniques, we first characterized the migration patterns of different blood cell types across the parabiotic barrier. We next induced MI in parabiotic mice by permanent ligation of the left anterior descending artery and examined the ability of injury-exposed neutrophils to permeate the parabiotic barrier and induce granulopoiesis in noninfarcted parabionts.

MI promoted greater accumulation of the inflammasome-primed neutrophils in the bone marrow. Introducing a time-dependent parabiotic barrier to the free movement of neutrophils inhibited their ability to stimulate granulopoiesis in the noninfarcted parabionts. Our data reveal a new paradigm of how circulatory cells establish a direct communication between organs by delivering signaling molecules (eg, IL-1β) directly at the sites of action rather through systemic release. We suggest that this pathway may exist to limit the off-target effects of systemic IL-1β release.

The Cambrian Biopharma Approach to Obtain Regulatory Approval of Drugs to Treat Aging

The approach outlined here by the Cambrian Biopharma principals isn't exactly a secret: at least the first part of the process is exactly the playbook for nearly every company working on interventions that target the mechanisms of aging. Since there is no established regulatory path to treat aging as a medical condition, companies must seek approval to treat a specific age-related condition. They pick the best choice of the scores that could be treated by slowing or reversing one or more mechanisms of aging. Most groups stop the future planning at that point, as the likely next step following regulatory approval will be widespread off-label use for any therapy that proves effective - and US regulators don't like companies talking about off-label use.

The interesting part of the Cambrian Biopharma plan is how to dovetail existing work on persuading regulators to accept a trial for aging, such as the TAME trial design, with the necessary first steps in gaining approval for the treatment of a single age-related condition. As the longevity industry moves forward, and more approaches reach the point of clinical trials, this sort of open discussion about how to bring the regulators into line with reality will be increasingly necessary. Working within the system like this is one approach. There is also an energetic faction that feels that regulatory arbitrage and medical tourism are more viable approaches, moving treatment to countries with less restrictive and less costly regulatory regimes in order to force change at the FDA through competition.

The Secret Cambrian Bio Master Plan to Build Drugs to Treat Aging (just between you and me)

Despite the enormous benefits to individuals and society from medicines that could keep people healthier for longer, the development of geroprotectors (aka drugs that prevent age-related decline) accounts for a tiny fraction (less than 1%) of research funding. The most common reason cited for this under-investment is that "aging" is not a disease, therefore you can't run a trial to "slow aging." This simplistic statement misses the mark in a few ways. The real challenges we need to overcome are more nuanced. They are: (1) multi-disease prevention (i.e., "aging") trials are risky, expensive, and slow; and (2) we don't have the biomarker needed to run cost-effective prevention trials in healthy people.

Cambrian's strategy tackles both of these key challenges with what I call our 'Secret Master Plan'. Our plan has three stages: get approval for newly developed geroprotectors as treatments for existing diseases causing acute suffering to patients today. Then, when it's clear these drugs are safe, effective, and valuable, do the large and expensive trials to show that these medicines slow aging in at-risk (often older) people. Finally, we will use the huge amounts of data gathered from rigorous and controlled clinical trials to approve geroprotectors using a surrogate biomarker of multi-morbidity risk to help people in good health stay that way.

Longevity outsiders criticize any preventative medicine approaches because the clinical trials are long and expensive. Longevity insiders criticize our approach of starting with currently recognized diseases because they want to run aging studies now. Both of them are wrong. Prevention studies are both feasible and worth doing, but they can only start once the safety and commercial value of a drug has been established.

Because a geroprotection study of healthy people in middle age would take decades, our first preventative studies will involve older people at high risk for developing the major diseases of aging. A well-designed trial will deliver a clear yes or no answer on whether a drug reduces risk of multiple diseases in 3 to 5 years. Still a long time, but worth it to show that a geroprotector can extend healthspan in humans.

Philanthropically funded clinical trials are already contemplating this approach, most notably the TAME Trial which proposes to use metformin (an off-patent diabetes medicine that extends healthspan in mice) in elderly individuals to prevent them from developing new morbidities. The bar for new drugs still under patent will be higher than for old drugs like metformin, but new drugs intentionally designed to maximize longevity effects and increase safety will work much better than the field's first coincidental discoveries like metformin and rapamycin.

A multi-disease preventative taken by at-risk elderly people would be the best-selling drug of all time. In 2030, a drug approved only for people 75 and older would have a market size of over 30 billion per year even if that drug costs less than 1,000 annually (way cheaper than most other drugs and less than a cup of coffee per day in New York). The impact of such a drug would be priceless.

Nanowarming of Vitrified Kidneys and Hearts

Long term low temperature storage of living tissue is an active area of research. Cryoprotectant perfusion allows tissues to vitrify on cooling, minimizing ice crystal formation and thus preserving the small scale structure that is vital to tissue function. The challenge of cooling to vitrification is largely the challenge of obtaining good perfusion of cryoprotectant throughout the tissue, something that is much less of an issue for an isolated organ or tissue sample than it is for an entire animal or human. The more significant challenges are those related to the goal of warming vitrified tissue while retaining full function.

The near term goal for reversible vitrification is to enable more cost-effective organ donation and transplantation. That organ transplantation is a very expensive, uncertain process, and the available supply of organs very limited, is due in large part to the inability to keep an organ alive for long outside the body. In the mid-term, the transplantation industry will expand to include the manufacture of universal off-the-shelf tissues and organs that can be transplanted into any individual, grown from stocks of engineered cells. The logistics of that industry will be greatly aided by the ability to indefinitely store manufactured tissues, rather than making them to order. In the longer term, reversible vitrification will be used to preserve people who are close to death, in the hopes that future medical technology will allow their repair and revival.

At present vitrification of a patient at death by the still small cryonics industry is a one-way trip; the hope for future medical technology includes the development of means to safely warm the patient as well as repair other issues. It is not unreasonable to think that a future in which aging can be reversed at a very late stage is also a future in which vitrified tissues can be warmed. Unfortunately, the most successful of early approaches to warming vitrified tissues, discussed in today's research materials, won't help the cryopreserved patients already vitrified in past years. It requires nanoparticles to be perfused into tissues with cryoprotectant at the time of cooling. It will, however, help to start the organ transplantation industry on the road towards the use and refinement of vitrification technologies, still an important goal.

Vitrification and Rewarming of Magnetic Nanoparticle-Loaded Rat Hearts

To extend the preservation of donor hearts beyond the current 4-6 hours, this paper explores heart cryopreservation by vitrification - cryogenic storage in a glass-like state. While organ vitrification is made possible by using cryoprotective agents (CPA) that inhibit ice during cooling, failure occurs during convective rewarming due to slow and non-uniform rewarming which causes ice crystallization and/or cracking. Here an alternative, "nanowarming", which uses silica-coated iron oxide nanoparticles (sIONPs) perfusion loaded through the vasculature is explored, that allows a radiofrequency coil to rewarm the organ quickly and uniformly to avoid convective failures.

Nanowarming has been applied to cells and tissues, and a proof of principle study suggests it is possible in the heart, but proper physical and biological characterization especially in organs is still lacking. Here, using a rat heart model, controlled machine perfusion loading and unloading of CPA and sIONPs, cooling to a vitrified state, and fast and uniform nanowarming without crystallization or cracking is demonstrated. Further, nanowarmed hearts maintain histologic appearance and endothelial integrity superior to convective rewarming and indistinguishable from CPA load/unload control hearts while showing some promising organ-level (electrical) functional activity. This work demonstrates physically successful heart vitrification and nanowarming and that biological outcomes can be expected to improve by reducing or eliminating CPA toxicity during loading and unloading.

Vitrification and Nanowarming of Kidneys

Vitrification can dramatically increase the storage of viable biomaterials in the cryogenic state for years. Unfortunately, vitrified systems ≥3 mL like large tissues and organs, cannot currently be rewarmed sufficiently rapidly or uniformly by convective approaches to avoid ice crystallization or cracking failures. A new volumetric rewarming technology entitled "nanowarming" addresses this problem by using radiofrequency excited iron oxide nanoparticles to rewarm vitrified systems rapidly and uniformly. Here, for the first time, successful recovery of a rat kidney from the vitrified state using nanowarming is shown.

First, kidneys are perfused via the renal artery with a cryoprotective cocktail (CPA) and silica-coated iron oxide nanoparticles (sIONPs). After cooling at -40 °C min-1 in a controlled rate freezer, microcomputed tomography (µCT) imaging is used to verify the distribution of the sIONPs and the vitrified state of the kidneys. By applying a radiofrequency field to excite the distributed sIONPs, the vitrified kidneys are nanowarmed at a mean rate of 63.7 °C min-1. Experiments and modeling show the avoidance of both ice crystallization and cracking during these processes. Histology and confocal imaging show that nanowarmed kidneys are dramatically better than convective rewarming controls. This work suggests that kidney nanowarming holds tremendous promise for transplantation.

Metabolic Coupling in the Aging Retina

An interesting perspective is presented in this open access paper, a discussion of the age-related decline in coupling of metabolism between different cell types in the retina. Cell metabolism cannot be considered in isolation for a given cell or cell type, particularly in the central nervous system, where, for example, supporting cells provide metabolites to neurons. As is the case for many aspects of aging, it is hard to draw clear lines of cause and effect between more fundamental forms of cell and tissue damage and downstream disruption of complex systems such as this within our biology.

One particular metabolic pathway of interest in various cell types is the process of Warburg glycolysis. This process was originally discovered in the 1920s by Otto Warburg, who made observations about large quantities of lactate production in the neuroretinal and tumor cells in the presence of oxygen. This usually occurs as part of an "organized duet" between two compartmentalized cell types. Traditional thinking has taught that one half of this duo, cells rich in glycolytic pathways, results in the end product of pyruvate. Subsequent fate ordinarily depends on the presence of oxygen and mitochondria; however, in certain cell types - including cancer cells, neurons, and photoreceptors - pyruvate is converted to lactate by lactate dehydrogenase. This abundance of lactate generated by these specialized cells feeds other supporting cells that have adapted to use lactate as a fuel source and NAD+ to support glycolysis.

Until recently, lactate was thought of as mainly a metabolic waste product, but its roles as a carbon source and energy substrate have slowly been uncovered in the past decade. The other half of this coupling phenomenon, oxidative phosphorylation, is responsible for energy production in various cells that act in a supportive manner to the more glycolytic cell types. One particularly interesting coupling phenomena that has been extensively studied is the lactate shuttling that occurs between astrocytes and neurons. In this system, astrocytes sense activity at a neuronal synapse and, as a result, deliver the energy substrate lactate to surrounding neurons.

Retinitis pigmentosa is characterized by a dysregulation within the metabolic coupling of the retina, particularly between the glycolytic photoreceptors and the oxidative retinal pigment epithelium. This phenomenon of metabolic uncoupling is seen in both aging and retinal degenerative diseases, as well as across a variety of cell types in human biology. In this review, we explored metabolic coupling between various cell types in the retina, how retinal degenerations progress through the breakdown of this metabolic coupling, how aging mirrors the loss of coupling seen in the degenerative conditions, and lastly the development of strategies aimed at renormalizing the metabolic coupling between photoreceptors and retinal pigment epithelium cells as an imprecision medicine therapeutic avenue.

Age-Related Changes in Phospholipid Composition of Cell Membranes

This open access paper surveys what is known of age-related changes in the phospholipid composition of cell membranes, a feature that has been studied in a range of different species. As a mechanism of aging, this is likely downstream of deeper causes of aging, while also producing its own very complex set of consequences. Those consequences are poorly understood, and will likely remain poorly understood for the foreseeable future. There are only so many researchers and so much time and funding. Picking apart the fine details of aging at the level of cellular operations, particularly processes that can in principle influence near every aspect of cellular metabolism, is a very long-term prospect. This is why the better path forward towards lengthening the healthy human lifespan is to target the known root causes of aging, rather than studying their spreading, highly complex web of downstream consequences.

The relationship between lipids and aging has been well recognized. The contents, composition, and metabolism of fatty acid (FA) are altered in aged or long-lived humans and model organisms. Moreover, studies in model organisms such as Caenorhabditis elegans have revealed that various FA species could extend lifespan when supplemented in the diet. These unsaturated FAs function mainly through classic longevity factors, such as DAF-16/FOXO3, SKN-1/Nrf2, and HSF-1/HSF1, to regulate healthspan and lifespan.

Despite these advances linking FA to longevity regulation, little is known about their mechanisms of action. Generally, FAs function through several major mechanisms, including signaling molecules, energy resources, substrates for post-translational modifications, and the components of complex lipids. Take oleoylethanolamine for example, it acts as a signaling molecule and regulates animal lifespan by direct binding and activation of the nuclear hormone receptor NHR-80. But to date, only a few FAs were found to exert their functions directly as signaling molecules, or as substrates for post-translational modifications. The majority of FAs are incorporated into complex lipids such as membrane lipids as their acyl chains, thus affecting the structure, composition, and function of the membrane. Therefore, it is conceivable that FAs may regulate lifespan by acting as the important components of membrane lipids, potentially linking membrane homeostasis to lifespan regulation.

Membrane lipids, mainly phospholipids (PLs; also known as glycerophospholipids), consist of the lipid bilayer that acts as barriers between the cell and environment, and between different cellular compartments. However, numerous studies suggest that the lipid bilayer not only function as structural barriers but also play crucial roles in the regulation of multiple cellular processes. Also, this idea is supported by the diversity of membrane lipids (different membrane lipid species and different acyl chains within certain membrane lipids), which is far more beyond the need for barrier function. In regard to the aging process, studies in several model organisms have reported the association of the contents and compositions of many membrane lipids with animal age, supporting potential roles for the membrane lipids in aging modulation. In this review, we focused on PLs and summarized recent advances that link PL homeostasis to the aging process and discussed their potential mechanisms of action.

Arguing for Aging of the Gut Microbiome to Worsen the Burden of Cellular Senescence

We should expect most of the various different aspects of aging to strongly interact with one another, leading to worse outcomes. Degenerative aging accelerates as it progresses precisely because of such harmful interactions. Researchers here discuss a still novel view of the way in which age-related changes in the gut microbiome may lead to greater harms resulting from the burden of senescent cells present in aged tissues. Incidentally, both the aging of the gut microbiome and the accumulation of senescent cells have bidirectional relationships with age-related immune system dysfunction. Near all aspects of aging interact.

Understanding the relationship between the gut microbiome and healthy aging is fundamental to achieving systemic longevity. Cellular senescence - a major hallmark of aging - is a promising area of research that requires investigation with relation to microbial dysbiosis. As an inevitable, age-related process, cellular senescence can cause severe damage to the host upon accumulation, largely due to overexpression of the senescence-associated secretory phenotype (SASP) and associated metabolic dysregulation.

Data from recent findings suggest an intricate relationship to exist between the gut microbiome, cellular senescence, and skin health. This proposed relationship is anchored by the SASP and largely influences the aging phenotype and associated diseases. The skin is vulnerable to the accumulation of senescent cells due to its external exposures (e.g., UV radiation). Recent literature suggests senescence to partake in numerous cutaneous diseases, all of which compromise function of the skin and general health. The link between skin homeostasis and healthy aging is further supported by recent evidence demonstrating systemic detrimental effects from chronic senescence in the skin, likely through paracrine signaling. Moreover, the presence of bacterial metabolites in the skin due to the gut-skin crosstalk can disrupt skin health, one way being further aggravation of the SASP.

Recent investigation has drawn correlations between gut composition and cellular senescence and revealed a distinct microbial composition in the gut in response to senolytic treatment. However, additional studies are needed to advance knowledge on microbial composition and function in the presence of accumulated senescence. Metabolomics is one approach that can help characterize metabolites found systemically and in the skin in order to quantify the impact of specific metabolic activity on senescence.

Comparing Some of the Most Widely Used Epigenetic Clocks

Epigenetic clocks assess biological age based on an algorithmic combination of the DNA methylation status at some number of CpG sites on the genome. Some changes in DNA methylation are characteristic of age, but at this time it is unknown as to how these changes relate to the underlying damage and dysfunction of age. Researchers here find that an epigenetic clock using few CpG sites performs about as well as those using many more sites when it comes to correlations with mortality risk. This is interesting, but it seems unlikely that a clock using a small number of sites will perform well as a way to assess whether or not a potential rejuvenation therapy is working. A specific rejuvenation therapy will likely address only one underlying cause of aging, and there is no reason to expect that any given small collection of CpG sites will react usefully to changes in that one cause of aging.

Three DNA methylation (DNAm) based algorithms, DNAm PhenoAge acceleration (AgeAccelPheno), DNAm GrimAge acceleration (AgeAccelGrim), and mortality risk score (MRscore), based on methylation in 513, 1030, and 10 CpGs, respectively, were established to predict health outcomes and mortality. In this study, we evaluated and compared the three DNAm algorithms and a frailty index (FI) in relation to prediction of mortality in a cohort of older adults. The three DNAm algorithms and the FI were positively correlated with each other and each of them was independently associated with all-cause and cause-specific mortality.

Whereas the first-generation epigenetic clocks were assessed solely by chronological age as the reference, PhenoAge and GrimAge were designed to better capture biological aging. Given that AgeAccelPheno and AgeAccelGrim are reflecting differences of estimated biological age and chronological age, their lack of correlation with chronological age in our study was predictable. Moreover, AgeAccelPheno and AgeAccelGrim were observed to be weakly correlated with FI.

In a previous study from the Lothian Birth Cohort 1936, higher DNAm GrimAge was associated with lower cognitive ability and brain vascular lesions in older age. Previous studies also reported that higher GrimAge and PhenoAge values were associated with an increase in physical function deficits and were correlated with poorer fitness, such as diminished grip strength and cardio-pulmonary function. Frailty is a consequence of a cumulative decline in many physiological systems and frail individuals are characterized by increased vulnerability to age-related disorders. The observed correlations of AgeAccelPheno and AgeAccelGrim with FI in the current study may reflect declines in multiple physiological systems beyond "normal aging".

One primary aim of developing DNAm biomarkers is finding an accurate, simple, and feasible method to predict mortality or lifespan. In that respect, MRscore, requiring methylation quantification at a much lower number of CpGs, by itself or in combination with some easy-to-determine frailty measure, such as FI, has potential capacity to be a practical and economic indicator for mortality risk stratification.

A Mutation Distinguishing Modern Humans from Other Primates Acts to Reduce Oxidative Stress and Inflammation

Humans are long-lived in comparison to other primates, despite exhibiting broad genetic similarity to our closest neighboring species. Our comparative longevity is thought to have evolved as a consequence of our intelligence and culture, allowing grandparents to contribute to the survival of descendants, and thus increasing the selection pressure operating in later life. Here researchers identify one genetic difference in modern humans that may contribute to greater longevity. Interestingly, it is absent from Neanderthals, an ancestral subspecies of human that one would also expect to exhibit a greater life span as a result of intelligence and culture changing the landscape of later life selection pressure.

Aerobic organisms face the challenge of oxidative damage caused by reactive oxygen species produced as metabolic by-products. Glutathione reductase (GR) is a critical enzyme for preventing oxidative stress and maintaining a reduced intracellular environment. Almost all present-day humans carry an amino acid substitution (S232G) in this enzyme relative to apes and Neanderthals.

Three Neanderthal genomes and one Denisovan genome have been sequenced to high quality. This makes it possible to identify genetic changes that characterize modern humans. Among the single-nucleotide substitutions on the lineage leading to modern humans, which alter protein sequences, approximately 100 are known to occur among all or almost all humans today but not in the archaic genomes available to date. One of these affects GR, which, in present-day humans, carries a glycine residue at position 232, whereas Neanderthals, Denisovans, and other primates carry a serine residue at this position.

We express the modern human and the ancestral enzymes and show that whereas the activity and stability are unaffected by the amino acid substitution, the ancestral enzyme produces more reactive oxygen species and increases cellular levels of transcripts encoding pro-inflammatory cytokines. We furthermore show that the ancestral enzyme has been reintroduced into the modern human gene pool by gene flow from Neanderthals and is associated with multiple traits in present-day people, including increased susceptibility for inflammatory-associated disorders and vascular disease.

Life Biosciences Raises a Sizable Round of Funding

I'll note the recent Life Biosciences capital raise as an example of the dramatic increase in funding flowing into the longevity industry in the past year or so. The companies that started earlier, many of which are running multiple distinct programs aimed at various approaches to the treatment of aging, are reaching the point at which they need to pull in significant funding to prepare for and undertake their first clinical trials. That funding is increasingly available. This remains a young industry, yet to obtain regulatory approval for any of the therapies under development, but it is clearly a field of growing interest.

Life Biosciences, a pioneering life sciences company developing therapeutics that target the biology of aging, today announced the completion of a Series C financing of 82 million led by Alpha Wave Ventures. Senior management and founders invested in the Series C financing alongside longevity-oriented funds, seasoned investors, and experienced biotechnology scientists/entrepreneurs. Since its founding, Life Biosciences has raised over 158 million.

"Our three platforms are based on seminal research demonstrating that aging biology can be modified therapeutically. The Series C funding enables us to accelerate development of our innovative therapies for multiple aging-related conditions, and we expect to initiate first-in-human studies for our first drug candidate possibly as early as the end of 2022."

Proceeds from the Series C financing will be used to accelerate research and development activities in the company's three platforms that target fundamental biological mechanisms contributing to aging. The mitochondrial uncoupling platform is developing oral small molecules that are designed to increase metabolic rate and decrease fat accumulation in models of obesity and NASH. The chaperone-mediated autophagy (CMA) platform is developing oral small molecules that are designed to activate CMA and thereby remove unwanted proteins that accumulate during aging and contribute to multiple aging-related diseases including neurodegenerative diseases. The epigenetic reprogramming platform is developing therapies that are designed to induce the expression of three Yamanaka factors to reprogram the epigenome of cells to a younger state and thereby restore cellular function across a wide range of diseases such as glaucoma.

Incidence of Cognitive Impairment is in Decline

Rates of cognitive impairment in older people continue to decline, as noted in this study. The researchers attribute this to just about everything except improvements in medical technology, though it may well be the case that improvements in treatment and prevention of cardiovascular disease contribute to this slowed loss of cognitive function. The population is aging, however, and with an ever greater fraction of the population being old, the overall incidence of age-related disease is increasing even as individual risk falls. Further, present trends represent only incremental improvements; the development of new medical technology to treat the causes of aging is the only viable path to radical gains in health and life span.

A new nationally representative study found an abrupt decline in the prevalence of cognitive impairment among American adults aged 65 and older compared to the same age group a decade earlier. In 2008, 12.2% of older Americans reported serious cognitive problems. In 2017, the percentage had declined to 10.0%. To put this into perspective, if the prevalence of cognitive impairment had remained at the 2008 levels, an additional 1.13 million older Americans would have experienced cognitive impairment in 2017.

The study was based on 10 consecutive waves of the American Community Survey (2008-2017), an annual nationally representative cross-sectional survey of approximately half a million American respondents aged 65 and older, including both institutionalized and community-dwelling older adults. A total of 5.4 million older Americans were included in the study. In each year, respondents were asked to report if they had "serious difficulty concentrating, remembering, or making decisions." The rate of decline in cognitive impairment was steeper for women than men. Women experienced a decline of 23% over the decade, while their male peers had a 13% decline during that period.

Further analyses indicated that 60% of the observed decline in serious cognitive impairment between 2008 and 2017 was attributable to generational differences in educational attainment. Extensive previous research has concluded that every additional year of formal schooling lowers the risk of individuals eventually developing dementia. Compared to children born in the 1920s, Americans born in each successive decade had much greater opportunities to pursue post-secondary education.

However, the decline in the prevalence of cognitive problems was not entirely explained by generational differences in educational attainment, suggesting there may be other factors at play that warrant future research. The authors hypothesize several possible contributors to these positive trends, such as improvement across the generations in nutrition, declines in smoking and air pollution, and the phase out of leaded gasoline.

Senescent Cells Negatively Affect T Helper Cell Differentiation

The accumulation of senescent cells with age harms tissues and cell behavior throughout the body. Senescent cells generate a pro-growth, pro-inflammation mix of molecules, the senescence-associated secretory phenotype (SASP). Researchers are still comparatively early in the process of producing a complete list of problems caused by the SASP. One of the better studied SASP components is TGF-β, and here researchers demonstrates that it causes disarray in the normal behavior of T-helper cells of the adaptive immune system. Applying senolytic treatments that selectively destroy senescent cells can reverse this aspect of aging, along with many others that are caused in part by senescent cells.

Aging and senescence impact CD4 T helper cell (Th) subset differentiation during influenza infection. In the lungs of infected aged mice, there were significantly greater percentages of Th cells expressing the transcription factor FoxP3, indicative of regulatory CD4 T cells (Treg), when compared to young. TGF-beta levels, which drive FoxP3 expression, were also higher in the bronchoalveolar lavage of aged mice and blocking TGF-beta reduced the percentage of FoxP3+ Th in aged lungs during influenza infection.

Since TGF-beta can be the product of senescent cells, these were targeted by treatment with senolytic drugs. Treatment of aged mice with senolytics prior to influenza infection restored the differentiation of Th cells in those aged mice to a more youthful phenotype with fewer Th cells expressing FoxP3. In addition, treatment with senolytic drugs induced differentiation of aged Th toward a healing Type 2 phenotype, which promotes a return to homeostasis. These results suggest that senescent cells, via production of cytokines such as TGF-beta, have a significant impact on Th differentiation.

Further Wrangling Over the Definition of Aging as a Disease

The World Health Organization (WHO) manages the International Classification of Diseases (ICD), which goes through revised editions every so often. Since regulatory agencies and healthcare payers use the ICD in determining just about everything regarding whether or not specific treatments are permitted, many groups involved in the development of therapies to treat aging are interested in seeing aging unambiguously added to the ICD. At the end of the day this has little to do with semantics and a great deal to do with finances: the availability of funding for research and development, the direct and indirect costs of gaining regulatory approval, and so forth. Needless to say, this is all proceeding much as things usually do in large bureaucracies - slowly and to no-one's satisfaction, with the likely end result being greater ambiguity and cost rather than less ambiguity and cost.

It was proposed to exclude the code 'Old age' MG2A from the latest version of the International Classification of Diseases, ICD-11, with the claim that equating old age to a disease could have the negative consequences of treating calendar age as a disease, raising concerns of ageism. Yet, in fact, the 'Old age' code is not a new ICD addition, or one that should raise special concerns of ageism. The synonymic designation of 'Senility' or 'Old age' was carried over from ICD-10 as it has been a rather technical designation that allowed to establish the cause of death, when it was difficult or impossible to establish other causes. In contrast to the earlier versions, the ICD-11 allows for diverse synonymic interpretations, including those that can be highly useful for a clinician treating older persons, such as 'Ageing', 'Senescence', 'Senile state', 'Frailty', and 'Senile dysfunction', which refer to a state of health but not the number in the passport.

It is becoming increasingly clear that pathological processes of ageing are the major risk factors, and even major underlying causes of mortality and morbidity from non-communicable diseases, and, as we learn from the recent pandemics, also from infectious diseases. To address these ageing-related risk factors, there is a new wave of research and development that seeks to develop new therapies or repurpose older therapies, with the aim to slow and reverse the damage of ageing - i.e. preventive, regenerative, and curative medicine. This research and development necessitates appropriate ICD coding.

The new ICD-11 makes important steps toward that goal, as it provides a double focus for improving the health of older persons. First, by including the old age, senescence, and senile debility in the general symptoms category to target the state of ageing-related ill health, and second by including 'Ageing-related' code in the aetiology or causality category to target the pathogenic ageing processes. Thus, far from discriminating against the rights of older persons and fostering neglect for their curative or preventive health care, the ICD-11 codes for old age and ageing-related causality do exactly the opposite: they draw the public and professional attention to the specific health problems of older persons and call to action to improve the prevention and cures specifically for older persons. Thus, these designations are the very opposite of ageism.

UV Radiation and Cross-Linking Contribute to Elastosis in Aged Skin

The elasticity of skin emerges from the structural properties of the extracellular matrix maintained by skin cells, the fine details of the structure of elastin and collagen that become disrupted with age. Two of the more important contributions to skin aging are, separately, exposure to UV radiation and the formation of persistent cross-links. Cross-links emerge from advanced glycation end-products (AGEs), sugary metabolic waste that can persistently link molecules in the extracellular matrix, changing the properties of tissue.

Removing persistent cross-links is a tractable challenge, given suitable enzymes, though too few groups are at present working towards this important goal. A more challenging prospect is restoration of elastin, ensuring that the structure of the aged extracellular matrix is returned to a more youthful configuration. This is likely to require sophisticated control of skin cell behavior, to replicate the initial creation of elastin structures that takes place during the developmental period of life.

Skin aging is the result of superimposed intrinsic (individual) and extrinsic (e.g., UV exposure or nutrition) aging. Previous works have reported a relationship between UV irradiation and glycation in the aging process, leading, for example, to modified radical species production and the appearance of AGEs (advanced glycosylation end products) in increasing quantities, particularly glycoxidation products like pentosidine. In addition, the colocalization of AGEs and elastosis has also been observed.

We first investigated the combination of the glycation reaction and UVA effects on a reconstructed skin model to explain their cumulative biological effect. We found that UVA exposure combined with glycation had the ability to intensify the response for specific markers: for example, MMP1 or MMP3 mRNA, proteases involved in extracellular matrix degradation, or proinflammatory cytokine, IL1α, protein expression. Moreover, the association of glycation and UVA irradiation is believed to promote an environment that favors the onset of an elastotic-like phenomenon: mRNA coding for elastin, elastase, and tropoelastin expression is increased.

Secondly, because the damaging effects of UV radiation in vivo might be more detrimental in aged skin than in young skin due to increased accumulation of pentosidine and the exacerbation of alterations related to chronological aging, we studied the biological effect of soluble pentosidine in fibroblasts grown in monolayers. We found that pentosidine induced upregulation of CXCL2, IL8, and MMP12 mRNA expression (inflammatory and elastotic markers, respectively). Tropoelastin protein expression (elastin precursor) was also increased.

In conclusion, fibroblasts in monolayers cultured with soluble pentosidine and tridimensional in vitro skin constructs exposed to the combination of AGEs and UVA promote an inflammatory state and an alteration of the dermal compartment in relation to an elastosis-like environment.

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