July 2nd, 2023

Fight Aging! Newsletter, July 3rd 2023

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Fight Aging! publishes news and commentary relevant to the goal of ending all age-related disease, to be achieved by bringing the mechanisms of aging under the control of modern medicine. This weekly newsletter is sent to thousands of interested subscribers. To subscribe or unsubscribe from the newsletter, please visit: https://www.fightaging.org/newsletter/

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Contents

If Probiotics in their Present Form Were a Truly Effective Intervention, We Would Already Know
https://www.fightaging.org/archives/2023/06/if-probiotics-in-their-present-form-were-a-truly-effective-intervention-we-would-already-know/

There is an increasing focus in the research community on the role of the gut microbiome in aging. This is in large part driven by the ability to accurately, cost-effectively measure the composition of the gut microbiome from a stool sample, using 16S rRNA sequencing. The 16S rRNA gene is differs between bacterial species, without being subject to a high rate of mutation and change. Using low-cost modern techniques, researchers can thus read out the relative numbers of different species in the gut microbiome, a service now available to the public at large as well. This allows researchers to see exactly how the balance of populations changes with age and disease states.

The gut microbiome does change with age, and it changes in ways that promote harmful, inflammatory microbial populations at the expense of helpful microbial populations responsible for generating beneficial metabolites such as butyrate. Researchers have shown that transplanting a microbiome derived from stool samples from young animals into old animals can reset the aged microbiome to a more youthful balance of microbial populations. The result is improved health and extended life.

Unfortunately, when it comes to the application of this discovery to human medicine, all too often the focus stops at the application of probiotics to the problem of the aged metabolism. Yes, we know that probiotics are beneficial. Yes, they are cheap and readily available. If present probiotic formulations were a truly effective intervention, capable of restoring a youthful gut microbiome, we would certainly know that by now. Alas, they are not. Given the evidence to date from animal studies, the real focus should be on establishing the infrastructure for widespread us of fecal microbiota transplantation from young donors to old people.

Gut microbiome-mediated mechanisms in aging-related diseases: are probiotics ready for prime time?

Aging is characterized by increased concentrations of many pro-inflammatory factors in the circulation. In addition, chronic low-grade inflammation has been identified as a key process involved in aging. Chronic low-grade inflammation is influenced by changes in different tissues (muscle, adipose tissue), organs (brain, liver), systems (immune system), and ecosystems (gut flora). It can indirectly trigger diseases in other organs (e.g., metabolic diseases, neuroinflammatory diseases, cardiovascular diseases, etc.). Chronic low-grade inflammation is one of the main contributing factors to various age-related diseases in the elderly.

Furthermore, chronic low-grade inflammation is closely related to the dysregulation of gut flora. Many immune cells and microbiota in the digestive tract interact with each other to maintain immune homeostasis. Intestinal microbiota plays a role in maintaining healthy levels of inflammation by integrating gastrointestinal, immune, and neurological information. Data obtained from animal models have demonstrated that age-related microbial ecological disorders can lead to intestinal permeability, systemic inflammation, and premature death. Altering the gut microbiota of older adults with wholesome bacteria exerts positive effects on the maintenance of optimal immune responses, which decline with age. Such effects include delaying the aging of T lymphocytes and increasing the number of immune cells that respond to acute antigen exposure.

Probiotics can effectively assist in maintaining the balance in the composition of gut microbial flora, thereby protecting the gut barrier and regulating gut immunity. Increasing scientific evidence has shown that probiotics exert a positive effect on chronic low-grade inflammation and play a key role in healthy aging and improving age-related diseases. Probiotics might be an important therapeutic strategy for the prevention, delay, or even reversal of low-grade inflammation in old age. However, robust controlled clinical trials are warranted to further validate this hypothesis.

The Contribution of Transposons to Differences in Life Span Between Species
https://www.fightaging.org/archives/2023/06/the-contribution-of-transposons-to-differences-in-life-span-between-species/

Transposable elements in the nuclear genome, also called transposons, are remnant DNA sequences left over from past, often ancient viral infections. A transposon is capable of hijacking the intricate machineries of gene expression to insert further copies of itself into the genome if not suppressed, producing what is effectively DNA damage as these haphazard insertions break existing gene sequences. Further, the transcription of transposon DNA produces viral-like RNA that can provoke an inflammatory innate immune response when present in the cell. Unfortunately, the suppression of transposons weakens with age, allowing these issues to arise and contribute to degenerative aging.

It is entirely unclear as to exactly how much of aging and cancer risk can be attributed to activation of transposons. Absent a means to safely shut down transposon activity near entirely in old animals, efforts to better understand the size of the problem must rely on more indirect approaches. Thus the research community undertakes studies such as the one outlined in today's open access paper. The authors looked over the genomes of selected small mammals with short and long life spans, and compared the differing burden of transposon insertions. It appears that short-lived species at a given body mass tend to have a greater number of potentially active transposons, which might be used to apply some bounds to the degree to which transposon activation constrains life span.

Comparative analysis of bats and rodents' genomes suggests a relation between non-LTR retrotransposons, cancer incidence, and ageing

Transposable element (TE) activity and accumulation can have manifold effects on genomes and biological phenotypes. Multiple studies have linked TEs to ageing and the development of several diseases including cancer. Here, we have studied the relationship between TEs and two different aspects of mammal life: longevity and cancer incidence. In rodents, the short lifespan is associated with the presence of cancer. On the other hand, bats are considered cancer-resistant species. The bats and rodents considered in this study are known to have different lifespans while sharing similar, small, body sizes (under 2 kg). H. glaber is the rodent with the longest lifespan known (31 years) and resistant to cancer while the other rodents show shorter lifespans of 12 (C. porcellus), 4 (M. musculus) and 3.8 (R. norvegicus) years.

By analysing the TE annotations, we found that the main difference between short- and long-lived species of rodents is represented by a drop in non-LTR retrotransposon accumulation at recent times. Similarly, the long-lived species of bats showed a drop in non-LTR retrotransposon accumulation at recent times while presenting an overall accumulation of class II transposons (DNA transposons and Helitrons). Previous studies hypothesised that bats have a higher tolerance for the activity of transposable elements with alternative ways to dampen potential health issues due to this activity. Given our observation on the shared drop of non-LTR retrotransposons accumulation in bats and in H. glaber, we add to the aforementioned hypothesis, that the specific repression of non-LTR retrotransposon activity may enhance cancer resistance. In fact, the non-LTR retrotransposons are the most prevalent types of TEs in rodents and the most extensively investigated by biomedical research given that they are the only active TEs in the human genome.

As expected, cancer-prone species present a higher load of recently inserted non-LTR retroelements than cancer-resistant species. While lifespan of rodents showed a strong relation with the recent activity of non-LTR retrotransposons, the same type of relation for bats is less clear. However, based on a comparison of density of insertion (DI) of retrotransposons, we noticed that the long-lived bats show a DI similar to the sole long-lived cancer-resistant rodent (H. glaber), while the sole short-lived bat (M. molossus) shows a DI value more similar to short-lived rodents. Given the pattern of DI observed in rodents, we speculate that the recent accumulation of non-LTRs may be related to the lifespan of these species.

The increased transcription of non-LTR retrotransposons in humans may contribute to so-called "sterile inflammation", a phenomenon for which a chronic state of inflammation is triggered without the presence of any obvious pathogen and that is exacerbated with age ("inflammaging"). The density of recently inserted non-LTR elements in short-lived bat M. molossus is 8269 per Gb, which is comparable to the value in the short-lived rodent Cavia porcellus (9,163 insertions per Gb). In contrast, the long-lived rodent Heterocephalus glaber has a DI of only 4,550 insertions per Gb, while the long-lived bat Myotis lucifugus has 4,531 insertions per Gb. Therefore, we speculate that the marked accumulation of non-LTR retrotransposons in M. molossus might trigger phenomena similar to the sterile inflammation and inflammaging that can cause a shortening of its lifespan. For these reasons M. molossus, together with the well-known H. glaber, may be an exceptional model for biogerontology.

Reviewing the Role of TFEB Upregulation in Approaches Shown to Slow Aging
https://www.fightaging.org/archives/2023/06/reviewing-the-role-of-tfeb-upregulation-in-approaches-shown-to-slow-aging/

Most of the varied approaches shown to modestly slow the progression of aging appear to operate through a small number of common mechanisms, largely involving the cellular response to stress. Some of those mechanisms will turn out to be more influential than others, though little progress has been made towards assigning relative importance to the various layers of the exceedingly complex reactions to heat, cold, restriction of nutrients, and other forms of mild stress that can produce beneficial outcomes.

The most compelling evidence to date suggests that improved autophagy is one of the more relevant portions of the cellular response to stress, a greater recycling of worn and damaged cell components leading to improved function over time. Here, researchers discuss TFEB, a regulator of autophagy, in the context of interventions shown to slow aging. In this context, it is worth noting that stress response enhancement of longevity appears to produce much larger effects in short-lived species than in long-lived species. In the two cases where one can compare fairly directly compare humans with mice, the practice of calorie restriction and loss of function mutations in growth hormone signaling, there is no evidence for a sizable increase in life span in our species.

TFEB is a central regulator of the aging process and age-related diseases

Extending lifespan or delaying aging has been shown to protect against degenerative diseases, and interventions that slow down the normal aging process can ameliorate multiple age-related pathologies and increase lifespan. For this reason, age-related diseases may be viewed as organ-specific conditions of accelerated aging. Therefore, slowing down the aging process is vital to prevent age-associated diseases.

Transcription factor EB (TFEB) is a key transcriptional regulator of autophagy and lysosomal biogenesis. Laboratory experiments in model organisms demonstrated that TFEB overexpression promoted longevity and reduced the burden of diseases. In rodents, healthy lifestyle interventions, such as caloric restriction and physical activity, were found to activate TFEB and upregulate autophagy, leading to a lower disease burden and extended lifespan. Pharmacological activators of TFEB, such as metformin and trehalose, also promoted autophagy and therapeutic benefits similar to caloric restriction and physical exercise. In humans, the dysregulation of TFEB is implicated in aging and diseases. Clinical trials are underway to test the safety and efficacy of caloric restriction mimetics known for their potent activation of TFEB and autophagy, such as metformin, trehalose, resveratrol, and spermidine.

Understanding the functional role of TFEB in the aging process and disease could help in the development of new therapeutic interventions for treating age-related diseases, which can extend lifespan. In this review, we provide up-to-date information on the contributions of TFEB activation in the modulation of the various hallmarks of aging and discuss the specific impact these may have on different tissues in the context of aging and age-related diseases. Furthermore, we argue that TFEB activation is a vital effector mechanism by which healthy lifestyle behaviors including caloric restriction, intermittent fasting, and exercise prevent diseases and extend lifespan.

Photobiomodulation as an Approach to Improve the Quality of Transplanted Stem Cells
https://www.fightaging.org/archives/2023/06/photobiomodulation-as-an-approach-to-improve-the-quality-of-transplanted-stem-cells/

It is becoming clear that a major factor in the highly variable quality of first generation stem cell therapies has a lot to do with the degree to which cells become senescent when expanded in culture prior to injection. This can vary widely with small differences in culturing technique, even given a similar protocol, or the same team performing the same processes from one batch to the next, absent very rigorous quality control mechanisms of the sort typically not used by clinics in the medical tourism industry. The research community is looking into the use of senolytics to improve outcomes, but it is unclear as to whether this or any of the other possible approaches to minimize cellular senescence in stem cell cultures have yet to be adopted by clinics.

One of the other possible options is the use of photobiomodulation, the use of light to improve mitochondrial function. This may reduce the pace at which cells become senescent meaningfully in cell culture, and perhaps even in tissues, though there is far too little published research on that topic. Even if it isn't that great as a therapy to reduce senescence in people, it may find a use in efforts to ensure that first generation stem cell therapies are less hampered by cellular senescence. Interestingly, the researchers suggest that it may be sufficient to harvest exosomes from stem cells subjected to photobiomodulation and use those to minimize cellular senescence in cultures, though it would seem logistically easier to treat with light.

Photomodulation alleviates cellular senescence of aging adipose-derived stem cells

Mesenchymal stem cells (MSCs) therapies are emerging as a promising approach to therapeutic regeneration. Therapeutic persistence and reduced functional stem cells following cell delivery remain critical hurdles for clinical investigation due to the senescence of freshly isolated cells and extensive in-vitro passage. In this study, cultured adipose-derived stem cells (ASCs) were derived from subcutaneous white adipose tissue isolated from mice fed a normal diet. We performed senescence-associated-β-galactosidase (SA-β-gal) staining, real-time PCR, and Western blot to evaluate the levels related to cellular senescence markers.

The mRNA expression levels of senescence markers were significantly increased in the later passages of ASCs. We show that light activation reduced the expression of senescent genes, and SA-β-Gal in all cells at passages. Moreover, the light-activated ASCs-derived exosomes decrease the expression of senescence, and SA-β-Gal in the later passage cells. We further investigated the photoreceptive effect of Opsin3 (Opn3) in light-activated ASCs. Deletion of Opn3 abolished the differences of light activation in reduced expression of senescent genes, increased Ca2+ influx, and cAMP levels.

We explored the effects of photomodulation on exosome secretion. The concentration of light-treated ASC exosomes represented approximately a fivefold increase compared with non-light-treated ASCs. Light-activated ASC-derived exosomes could represent a new protective paradigm for cellular senescence resulting from in-vitro passaging.

How to Run a Comparatively Simple Self-Experiment to Assess the Impact of Taurine Supplementation on Measures of Aging
https://www.fightaging.org/archives/2023/06/how-to-run-a-comparatively-simple-self-experiment-to-assess-the-impact-of-taurine-supplementation-on-measures-of-aging/

This post walks through the process of setting up and running a simple self-experiment with taurine supplementation, shown to improve measures of health in old mice and non-human primates. These effects result from enhancing the performance of glutathione, an antioxidant enzyme. You might recall that supplementation with gluthathione precursors to increase gluthatione levels produced suprisingly large effects for a supplement regimen in a small trial in older people.

Taurine levels in blood decline with age, halving from the 20s to 40s-50s in the general population. So while forms of dietary supplementation are usually less compelling than more technological options for improving health in later life, the early decline in taurine, ease of conducting a self-experiment, data in animals, and potential connection to glutathione make it interesting enough to try.

Taurine is a semi-essential amino acid. It is widely used as a supplement, and has undergone rigorous human clinical trials. "Widely used" does not equate to "safe for everyone at any dose", however. Older individuals can and do suffer injury and death from everyday actions, foods, and medications that have no such impact on younger individuals. Regardless of the legions using any particular supplement, it is always wise to gently ease into any personal attempt to join them, rather than leaping in at a full dose on day one.

Contents

  • Why Self-Experiment with Taurine?
  • Caveats
  • Establishing Dosages
  • Obtaining Taurine
  • Establishing Tests and Measures
  • Guesstimated Costs
  • Schedule for the Self-Experiment
  • Where to Publish?

Why Self-Experiment with Taurine?

A recent study assembled a range of data on taurine levels in blood and taurine supplementation in mice and non-human primates. Taurine levels decline with age and supplementation produces interestingly large benefits to long-term health in these species. Large in the context of what can be achieved by supplements, at least. Further, taurine levels may be connected to the activity of the antioxidant enzyme gluthatione. In a different context, supplementation of glutathione precursor compounds was also shown to produce benefits that are large in the context of supplementation.

It remains unknown as to why taurine levels decline with age, though given that this is an amino acid, we might first think of changes in the gut microbiome and processing of food. There are many, many changes in measurable metabolites in blood that occur with age, but few are demonstrated to produce benefits when reversed, and few are as easily reversed as amino acid levels in the body - just consume more of that amino acid. Amino acid supplementation might be considered a relatively low risk activity, given the large numbers of people who undertake that intervention on a regular basis. A low risk, low cost, modest benefit intervention is unlikely to make you live for a decade longer, but may well be worth the effort for the results obtained.

Caveats

While taurine is widely used as a supplement and accompanied by copious human data on its effects and side-effects (or lack thereof at various doses), one must still think about personal responsibility in any self-experiment. Read the papers reporting on human trials - the effects, side-effects, and dosages - and make an informed personal decision on risk and comfort level based on that information. This is true of any supplement, whether or not approved for use. Do not trust other opinions you might read online: go to the primary sources, the scientific papers, and read those. Understand that where the primary data is sparse, it may well be wrong or incomplete in ways that will prove harmful. Also understand that older bodies can be frail and vulnerable in ways that do not occur in younger people, and that are sometimes not well covered by the studies.

Further, the state of knowledge regarding any particular set of compounds is not static. The science progresses. This post will become outdated in its specifics at some point, as new knowledge and new compounds with similar effects arrive on the scene. Nonetheless, the general outline should still be a useful basis for designing new self-experiments involving later and hopefully better options.

Establishing Dosages

While there is a standard rule of thumb for converting doses in animals to doses in humans, found in the open access paper "A simple practice guide for dose conversion between animals and human", the only definitive way to establish dosing for a supplement or pharmaceutical in order to achieve a given effect is to run a lot of tests in humans.

Fortunately, human trials have been conducted for taurine supplementation. Trial organizers have tended towards 1.5 grams or 3 grams per day for 16+ weeks. Animal studies in mice used 1 g/kg/day, which converts to a 0.08 g/kg/day gram dose in humans, or roughly 5 grams per day for a 60kg human. Animal studies in rhesus monkeys used 0.25 g/kg/day, which also comes to roughly 0.08 g/kg/day for humans, and thus 5 grams per day for a 60kg human.

One can in principle adjust the dose over time to get to a desired level of taurine in the blood, assuming that the desirable level is equivalent to that of a young individual as presented human data from a recent paper. It is relatively cheap to assess blood amino acids, and in many parts of the world one can simply order the tests without involving a physician. Taking 1.5 g/day or 3 g/day for a few weeks and then looking at the outcome before deciding to go to a 5 g/day dose for longer is a reasonable plan.

Obtaining Taurine

Taurine costs little and is readily available from supplement manufacturers in 1 gram pills or powder form. The pill option is more convenient but slightly more expensive. Ordering online is usually a better option than trying to find taurine in specialist supplement stores.

Establishing Tests and Measures

Looking through the literature on taurine supplementation and the various clinical trial designs, measures of inflammation, oxidative stress, and possibly glycation and insulin metabolism in blood samples are the most relevant for this exercise. Many of these tests can be purchased via Quest, Labcorp, or Life Extension Foundation (LEF) without needing a physician in most parts of the US. If cost is less of a concern, services like AgelessRx and Jinfiniti package these and many other assessments into one product. Setting aside considerations of convenience and cost, the following list is a good starting point:

  • Taurine: Amino acid level blood test.
  • Inflammation: C-reactive protein, TGF-alpha, IL-1, and IL-6, monocyte and granulocyte numbers from a complete blood count.
  • Oxidative stress: Oxidized LDL, 8-Oxo-2'-deoxyguanosine for DNA oxidation, glutathione reductase, superoxide dismutase.
  • Glycation and insulin metabolism: hemoglobin A1c, fasting glucose, insulin.

It would also be interesting to look at effects on epigenetic age, as no-one appears to have published data on that metric in the context of taurine supplementation. A number of services offer epigenetic age clocks at a variety of price points. One might also consider Phenotypic Age, which can be derived using one of the online calculators from the combination of the following from blood tests: creatine, albumin, fasting glucose, c-reactive protein, alkaline phosphatase (ALP), and the results of a complete blood count.

Guesstimated Costs

The costs given here are rounded up for the sake of convenience, and in some cases are blurred median values standing in for the range of observed prices in the wild.

  • Blood tests via Quest / Labcorp / LEF: $500 for each of baseline and final tests
  • TruDiagnostic epigenetic age kit: $500 / kit
  • Junifinity AgingSOS advanced biomarker panel: $1200 / kit
  • 1 kg of taurine powder: $30

Schedule for the Self-Experiment

One might expect the process of discovery, reading around the topic, and ordering materials to take a few weeks. Once all of the decisions are made and the materials are in hand, pick a start date. The schedule for the self-experiment is as follows:

  • Week 1: Conduct the baseline bloodwork. Take note of taurine level.
  • Weeks 1-4: Daily taurine supplementation at 1.5 g/day or 3 g/day.
  • Week 4: Conduct an amino acid test to assess taurine level. Comparing this, the baseline, and published human data, decide on the dose for the remainder of the self-experiment. Either stick with the existing dose, or move to the higher one.
  • Weeks 5-20: Daily taurine supplementation.
  • Week 20: Conduct the final bloodwork.

Where to Publish?

If you run a self-experiment and keep the results to yourself, then you helped only yourself. The true benefit of rational, considered self-experimentation only begins to emerge when many members of community share their data, to an extent that can help to inform formal trials and direction of research and development. There are communities of people whose members self-experiment with various compounds and interventions, with varying degrees of rigor.

When publishing, include all of the measured data, the compounds and doses taken, duration of treatment, and age, weight, and gender. Fuzzing age to a less distinct five year range (e.g. late 40s, early 50s) is fine. If you wish to publish anonymously, it should be fairly safe to do so, as none of that data can be traced back to you without access to the bloodwork provider. None of the usual suspects will be interested in going that far. Negative results are just as important as positive results. Many interventions will achieve too little to be easily detected for basically fit people younger than 50; the noise in the measures will be larger than the effect size of the intervention.

Senescent Cardiomyocytes Increase the Damage Following a Heart Attack
https://www.fightaging.org/archives/2023/06/senescent-cardiomyocytes-increase-the-damage-following-a-heart-attack/

If a heart attack is survived, it leads to long-term damage to heart tissue. Scarring, detrimental remodeling of heart muscle, and other dysfunctions result. Researchers here show that a raised burden of cellular senescence in cardiomyocytes specifically predisposes the aged heart to greater harm following a heart attack. This well illustrates that periodic senolytic treatments or related strategies that can minimize the presence of senescent cells in aged tissues are highly desirable. The presence of lingering senescent cells is harmful in many ways, directly causing organs to become less functional and more vulnerable.

Myocardial infarction is a leading cause of morbidity and mortality. While reperfusion is now standard therapy, pathological remodelling leading to heart failure remains a clinical problem. Cellular senescence has been shown to contribute to disease pathophysiology and treatment with the senolytic navitoclax attenuates inflammation, reduces adverse myocardial remodelling and results in improved functional recovery. However, it remains unclear which senescent cell populations contribute to these processes.

To identify whether senescent cardiomyocytes contribute to disease pathophysiology post-myocardial infarction, we established a transgenic mouse model in which p16 (CDKN2A) expression was specifically knocked-out in the cardiomyocyte population. Following myocardial infarction, mice lacking cardiomyocyte p16 expression demonstrated no difference in cardiomyocyte hypertrophy but exhibited improved cardiac function and significantly reduced scar size in comparison to control animals. This data demonstrates that senescent cardiomyocytes participate in pathological myocardial remodelling.

Importantly, inhibition of cardiomyocyte senescence led to reduced senescence-associated inflammation and decreased senescence-associated markers within other myocardial lineages, consistent with the hypothesis that cardiomyocytes promote pathological remodelling by spreading senescence to other cell-types. Collectively this study presents the demonstration that senescent cardiomyocytes are major contributors to myocardial remodelling and dysfunction following a myocardial infarction. Therefore, to maximise the potential for clinical translation, it is important to further understand the mechanisms underlying cardiomyocyte senescence and how to optimise senolytic strategies to target this cell lineage.

Metabolic Disorders Increase the Burden of Cellular Senescence
https://www.fightaging.org/archives/2023/06/metabolic-disorders-increase-the-burden-of-cellular-senescence/

Why do patients with metabolic disorders such as obesity and type 2 diabetes exhibit what appears to be an accelerated progression of aging, such as increased risk of disease, shorter life expectancy, and so forth? One increasingly well established candidate mechanism is the presence of a greater burden of senescent cells, these cells generating chronic inflammation and harmful alterations to the behavior of other cells via their secretions. Senolytic therapies to clear these senescent cells may prove to be a first step towards decoupling obesity from the consequences of obesity, but there are numerous other ways in which excess fat tissue or a dysfunctional, diabetic metabolism can provoke chronic inflammation and dysfunction of organs and bodily systems.

Cellular senescence is generally driven by aging and is strongly associated with age-related disorders. It promotes the common age-associated phenotypes of reduced number of functional cells and size of tissues/organs, increased fibrosis, inflammation, and accumulation of cells with genetic defects. However, other disorders such as type 2 diabetes (T2D), obesity, and NAFLD/NASH are also characterized by increased cellular senescence in metabolic cells.

Aged tissues are characterized by dysfunctional cells and increased inflammation, and both progenitor cells and mature, fully differentiated and nonproliferating cells are afflicted. Recent studies have shown that hyperinsulinemia and associated insulin resistance promote cellular senescence in both human adipose and liver cells. Similarly, increased cellular senescence can promote cellular insulin resistance, showing their interdependence. Furthermore, the increased adipose cellular senescence in T2D is independent of age, BMI, and degree of hyperinsulinemia, suggesting premature aging. These results suggest that senomorphic or senolytic therapy may become important for treating these common metabolic disorders.

HOXA3 Upregulation Accelerates Wound Healing in Aged Mice
https://www.fightaging.org/archives/2023/06/hoxa3-upregulation-accelerates-wound-healing-in-aged-mice/

Researchers here show that a gene therapy approach to upregulation of HOXA3 can accelerate wound healing in old mice. HOXA3 regulates a number of different processes related to tissue regeneration, though it is unclear as to which of these is more important in producing the observed outcome. It is worth noting that adjusting macrophage polarization to the M2 state is one of the mechanisms in play. Macrophages can adopt a range of states known as polarizations, where the more inflammatory M1 polarization is more suited to hunting down pathogens than participating in tissue regeneration. The more inflammatory environment of aged tissues may bias macrophages towards M1 and away from the desired M2 state. Methods of adjusting macrophage polarization are under investigation by a broad range of research groups as a potential way to reduce unresolved inflammatory signaling and improve the interaction of these innate immune cells with tissues in disease states and aging.

Chronic wounds are characterized by a persistent, hyper-inflammatory environment that prevents progression to regenerative wound closure. Such chronic wounds are especially common in diabetic patients, often requiring distal limb amputation, but occur in non-diabetic, elderly patients as well. Induced expression of HoxA3, a member of the Homeobox family of body patterning and master regulatory transcription factors, has been shown to accelerate wound closure in diabetic mice when applied topically as a plasmid encased in a hydrogel.

The mechanisms underlying the wound healing ability of HOXA3 has been preliminarily investigated. Macrophages transduced with HOXA3 promoted M2 polarization compared to controls. Furthermore, HOXA3 treatment mobilized and recruited endothelial progenitor cells while attenuating inflammatory pathways when compared to control mice and HOXA3 promotes the differentiation of hematopoietic progenitor cells into proangiogenic myeloid cells that stimulate neovascularization.

We now provide independent replication of those foundational in vivo diabetic wound closure studies, observing 16% faster healing (3.3 mm wounds vs 3.9 mm wounds at Day 9 post original injury of 6 mm diameter) under treatment with observable microscopic benefits. We then expand upon these findings with minimal dose threshold estimation of 1 μg HoxA3 plasmid delivered topically at a weekly interval. Furthermore, we observed similarities in natural wound healing rates between aged non-diabetic mice and young diabetic mice, which provided motivation to test topical HoxA3 plasmid in aged non-diabetic mice. We observed that HoxA3 treatment achieved complete wound closure (0 mm diameter) at 2 weeks whereas untreated wounds were only 50% closed (3 mm wound diameter). We did not observe any gross adverse effects macroscopically or via histology in these short studies. Whether as a plasmid or future alternative modality, topical HoxA3 is an attractive translational candidate for chronic wounds.

Senolytic Treatment Improves Neurogenesis in Aged Killifish
https://www.fightaging.org/archives/2023/06/senolytic-treatment-improves-neurogenesis-in-aged-killifish/

Killifish exhibit proficient regeneration, but lose regenerative capacity with advancing age. Some of this loss is due to the growing presence of lingering senescent cells, as the balance between the pace of creation of senescent cells and timely immune-mediated clearance of senescent cells is disrupted by the mechanisms of aging. Senolytic drugs that can force senescent cells into apoptosis represent a way to greatly reduce the impact of senescent cells on tissue function in later life. Researchers here show that the production of new neurons is inhibited by senescent cells in aged killifish, and is improved following senolytic treatment, leading to greater regeneration after brain injury.

The young African turquoise killifish has a high regenerative capacity, but loses it with advancing age, adopting several aspects of the limited form of mammalian regeneration. We deployed a proteomic strategy to identify pathways that underpin the loss of regenerative power caused by aging. Cellular senescence stood out as a potential brake on successful neurorepair.

We applied the senolytic cocktail Dasatinib and Quercetin (D + Q) to test clearance of chronic senescent cells from the aged killifish central nervous system (CNS) as well as rebooting the neurogenic output. Our results show that the entire aged killifish telencephalon holds a very high senescent cell burden, including the parenchyma and the neurogenic niches, which could be diminished by a short-term, late-onset D + Q treatment. Reactive proliferation of non-glial progenitors increased substantially and lead to restorative neurogenesis after traumatic brain injury.

Our results provide a cellular mechanism for age-related regeneration resilience and a proof-of-concept of a potential therapy to revive the neurogenic potential in an already aged or diseased CNS.

Towards Repair of the Leaking Blood-Brain Barrier
https://www.fightaging.org/archives/2023/06/towards-repair-of-the-leaking-blood-brain-barrier/

Researchers here report on an effort to find small molecule drugs that can favorably adjust cell metabolism in the blood-brain barrier, in order to prevent some fraction of the dysfunction and leakage that occurs with age. The blood-brain barrier is a specialized layer of cells that controls the traffic of molecules between the bloodstream and brain tissue. With advancing age, it becomes less effective, allowing unwanted molecules and cells to leak into the brain to provoke chronic inflammation and other issues. Maintaining effectiveness of the blood-brain barrier could push back the onset of neurodegenerative conditions.

Researchers have evaluated a new therapeutic class of molecules that can be used to treat a leaky blood-brain barrier. The researchers started by looking at WNT signaling, a communication pathway used by cells to promote tissue regeneration and wound healing. WNT signaling helps maintain the blood-brain barrier by promoting cell-to-cell communication that lines brain blood vessels. Scientists have been focusing on frizzled, a protein receptor that initiates the WNT pathway, for blood-brain barrier therapies since mouse mutations in the frizzled gene cause blood-brain barrier abnormalities.

Many different molecules bind to frizzled protein receptors, such as the frizzled receptor FZD4, so to narrow their search for a potential therapeutic molecule, the researchers selected only those that specifically target cells that line the brain's blood vessels. Researchers created L6-F4-2, a FZD4 binding molecule that activates WNT signaling 100 times more efficiently than other FZD4 binders.

Researchers then studied models of ischemic stroke, in which blood vessels and the blood-brain barrier are damaged, and fluid, blood and inflammatory proteins involved in cellular communication can leak into the brain. They found that L6-F4-2 reduced the severity of stroke and improved survival of mice compared with mice that had untreated strokes. Importantly, L6-F4-2 reversed the leakiness of brain blood vessels after stroke. Mice treated with L6-F4-2 had increased stroke survival, compared to those that were not treated. The finding shows that, in mice, the blood-brain barrier could be restored by drugs that activate FZD receptors and the WNT signaling pathway.

Frailty Correlates with Cognitive Decline
https://www.fightaging.org/archives/2023/06/frailty-correlates-with-cognitive-decline/

Frailty is known to correlate with risk of dementia, and here researchers observe an inverse correlation with cognitive function in a large study population of older adults. The many manifestations of aging, including age-related conditions, all arise from the underlying burden of molecular damage and disarray. To the degree that an older person is more damaged, one may expect them to exhibit greater tissue dysfunction and a higher risk of suffering many different conditions. Both frailty and neurodegenerative conditions are strongly linked to the chronic inflammation of aging, for example, the state known as inflammaging. This overactivation of the immune system is disruptive to health and tissue function throughout the body.

Frailty has been recognized as a growing issue in older adults, with recent evidence showing that this condition heralds several health-related problems, including cognitive decline. The objective of this work is to determine if frailty is associated with cognitive decline among older adults from different countries. We analyzed the baseline the Study on Global Ageing and Adult Health (SAGE), that includes six countries. A cross-sectional analysis was used to assess how frailty was related with the Clinical Frailty Scale (CFS) decision tree, while cognitive decline was evaluated using standardized scores of tests used in SAGE.

A total of 30,674 participants aged 50 years or older were included. To the best of our knowledge this is the first study to assess the association between cognitive performance tests and frailty measured using the CFS decision tree. Moreover, this adds to the current knowledge on how frailty relates to cognitive status in older adults, the higher the burden of frailty the lower the cognitive test scores.

Previous evidence shows that frailty could precede dementia and other neurocognitive disorders, and even be related to neuropathological findings. On the other hand, there have been some interventions - mainly based in physical activity - that have shown to improve the overall health status of an older adult with frailty, and this has the potential to stop the progression of both cognitive and physical decline. However, this relationship is still not fully understood, and merits further research.

The Interaction of Calorie Restriction and Circadian Rhythm
https://www.fightaging.org/archives/2023/06/the-interaction-of-calorie-restriction-and-circadian-rhythm/

Researchers here note that feeding and fasting time appears to meaningfully change the effects of long-term calorie restriction on life span in short-lived mammals. Much of the more recent literature on intermittent fasting, fasting mimicking strategies, and calorie restriction appears, to me at least, to lean towards the conclusion that time spent in a state of hunger is an important factor in the degree to which the intervention slows aging. It is interesting to compare this with protein restriction studies in which hunger and calorie intake is not meaningfully different between restricted animals and the control group. One might think that there are two very different sets of mechanisms at play, (a) those involving cell reactions to a diminished amount of specific proteins versus (b) cellular reactions to the regulatory signaling generated in the state of hunger, such as increased ghrelin secretion.

The modification of diet for longevity has long been of interest, research generally having been conducted in animal experiments. Caloric restriction (CR) is known to contribute to a prolongation of lifespan, even in higher animals. Recently, caloric restriction, fasting, and fasting intervals, and the time of eating with consideration to species-appropriate circadian alignment has been investigated. While caloric restriction itself has been found in numerous species to result in a significant prolongation of lifespan, it has also been shown that fasting regimens can independently promote longevity as well as improve deteriorated metabolic functions.

Researchers have reported that circadian alignment in addition to fasting promotes longevity independently of caloric restriction in male mice. The study compares the contribution of adjusted feeding times in addition to fasting in five caloric restriction groups on behavioral, metabolic, and molecular outcomes using automated feeders. Diet energy was restricted by 30% in all caloric restriction groups of mice fed under five caloric restriction protocols: two of the groups were fed during the active (night) or non-active (day) period for 2 hours; two groups were fed regularly every 90 minutes during half (12 hours) of the active or non-active period; and one group was fed every 160 minutes throughout the 24 hour day.

The results are intriguing. Caloric restriction itself extended the lifespan by 10%; when the fasting time was added, the lifespan was increased to 20%; and when the feeding time was aligned to the active period, the lifespan was further extended to 35%, demonstrating that when food intake is restricted to an appropriate time of the day there is an additional benefit to caloric restriction and fasting on lifespan.

Senescent Astrocytes in the Aging of the Brain
https://www.fightaging.org/archives/2023/06/senescent-astrocytes-in-the-aging-of-the-brain/

Cellular senescence in the supporting cells of the brain is increasingly implicated in the onset and progression of neurodegenerative conditions. Senescent cells accumulate with age, as the immune system becomes less competent and falters in their timely removal. These errant cells secrete pro-inflammatory factors that are disruptive of tissue structure and function, contributing to the neuroinflammation that is characteristic of age-related cognitive decline and dementia. We can hope that senolytic treatments capable of passing the blood-brain barrier will help to prevent and treat many forms of neurodegenerative disease but reducing the burden of cellular senescence, both in the brain, and elsewhere in the body.

For many decades after their discovery, astrocytes, the abundant glial cells of the brain, were believed to work as a glue, supporting the structure and metabolic functions of neurons. A revolution that started over 30 years ago revealed many additional functions of these cells, including neurogenesis, gliosecretion, glutamate homeostasis, assembly and function of synapses, neuronal metabolism with energy production, and others. These properties have been confirmed, limited however, to proliferating astrocytes.

During their aging or following severe brain stress lesions, proliferating astrocytes are converted into their no-longer-proliferating, senescent forms, similar in their morphology but profoundly modified in their functions. The changed specificity of senescent astrocytes is largely due to their altered gene expression. The ensuing effects include downregulation of many properties typical of proliferating astrocytes, and upregulation of many others, concerned with neuroinflammation, release of pro-inflammatory cytokines, dysfunction of synapses, etc., specific to their senescence program. The ensuing decrease in neuronal support and protection by astrocytes induces the development, in vulnerable brain regions, of neuronal toxicity together with cognitive decline. Similar changes, ultimately reinforced by astrocyte aging, are also induced by traumatic events and molecules involved in dynamic processes.

Senescent astrocytes play critical roles in the development of many severe brain diseases. The first demonstration, obtained for Alzheimer's disease less than 10 years ago, contributed to the elimination of the previously predominant neuro-centric amyloid hypothesis. The initial astrocyte effects, operating a considerable time before the appearance of known Alzheimer's symptoms evolve with the severity of the disease up to their proliferation during the final outcome. Involvement of astrocytes in other neurodegenerative diseases is now intensely investigated.

Rat Kidneys Vitrified, Warmed with Magnetic Nanoparticles, then Transplanted Successfully
https://www.fightaging.org/archives/2023/06/rat-kidneys-vitrified-warmed-with-magnetic-nanoparticles-then-transplanted-successfully/

Another step forward for the magnetic nanoparticle approach to thawing vitrified tissues was recently reported. Vitrification for low-temperature storage is a fairly well established technique, at least for organs. The challenge lies in thawing vitrified organ tissue without causing so much damage that it becomes non-viable for transplantation. Researchers have now managed to make this work for rat kidneys, albeit just barely. The kidneys were damaged, and it remains the case that scaling up to human organs will have its challenges. A greater volume of tissue makes cryopreservation and later thawing much harder, but success will greatly improve the economics and logistics of organ transplantation and tissue engineering, allowing tissues to be stored indefinitely.

For decades bringing organs back from a deep freeze without injury and with full function has remained a frustrating problem for the field. Researchers have already vitrified and revived human, mouse, and pig pancreas islet cells, and vitrified and rewarmed rat hearts and livers. When vitrifying, scientists first infuse the organ or tissue with magnetic nanoparticles and safeguarding chemicals called cryoprotective agents that serve as a kind of antifreeze. Afterward, they cool it quickly - 24 degrees Celsius per minute - to bypass the formation of cell-shredding ice crystals and directly enter a glass-like state.

Researchers have spent years developing technology that can rewarm vitrified materials fast enough to avoid ice-crystal formation in the physical transition back from glass. This rewarming, critically, also must be uniform, to avoid an organ cracking and splitting from its outside surfaces being too different a temperature from its core - like an ice cube in a glass of room-temperature water. Their solution is a technique called nanowarming, which utilizes a radio-frequency copper coil to create a magnetic field that excites iron nanoparticles throughout the organ all at once, similar to a microwave oven, but more uniform.

The experimental thawed rat kidneys produced urine within 45 minutes of transplantation into young rats, compared to a few minutes for their fresh counterparts. And for the first days after surgery, they were slower to clear out creatinine, a chemical waste product that kidneys remove from the body. "The biggest issue is that the kidneys were, in fact, badly damaged. The function of those kidneys was cut in about half. These were kidneys in the peak of life, in perfect health - and they barely made it." On the other hand, the degree to which the kidneys did heal and recover was "remarkable and encouraging." The researchers also noted that because they ended the study 30 days post-transplant, they weren't able to assess longer-term survival.

Researchers said they plan to spend the next six months attempting to scale their cryopreservation method up to pig organs - a size change, kidney-wise, from a large grape (in rats) to about a pear (in pigs). As they go, they will continue to study whether rewarmed animal organs recover their original physiological, chemical, and electrical properties. Down the line, if all goes well, the future might hold living banks where organs, skin, nerves, blood vessels, cartilage, and stem cells are preserved in liquid nitrogen for years until they're matched with the right patients.

Senescent Melanocytes Encourage Hair Growth
https://www.fightaging.org/archives/2023/06/senescent-melanocytes-encourage-hair-growth/

Why do moles tend to grow hair, even in older people who are well advanced in loss of hair growth elsewhere on the skin? Researchers here provide evidence for this to be due to signals secreted by senescent melanocyte cells. This may provide a path to encourage a reversal of hair loss in all of the various poorly-understood circumstances that lead to balding. Inducing an additional burden of cellular senescence in skin is not desirable, but a better understanding of exactly how the senescence-associated secretory phenotype (SASP) encourages hair growth could provide a more direct way to provide only the necessary signals to the skin.

Niche signals maintain stem cells in a prolonged quiescence or transiently activate them for proper regeneration. Altering niche signalling can lead to regenerative disorders. Melanocytic skin nevi in human often display excessive hair growth, suggesting hair stem cell hyperactivity. Here, using genetic mouse models of nevi, we show that dermal clusters of senescent melanocytes drive epithelial hair stem cells to exit quiescence and change their transcriptome and composition, potently enhancing hair renewal.

Nevus melanocytes activate a distinct secretome, enriched for signalling factors. Osteopontin, the leading nevus signalling factor, is both necessary and sufficient to induce hair growth. Injection of osteopontin or its genetic overexpression is sufficient to induce robust hair growth in mice, whereas germline and conditional deletions of either osteopontin or CD44, its cognate receptor on epithelial hair cells, rescue enhanced hair growth induced by dermal nevus melanocytes. Osteopontin is overexpressed in human hairy nevi, and it stimulates new growth of human hair follicles.

Although broad accumulation of senescent cells, such as upon ageing or genotoxic stress, is detrimental for the regenerative capacity of tissue, we show that signalling by senescent cell clusters can potently enhance the activity of adjacent intact stem cells and stimulate tissue renewal. This finding identifies senescent cells and their secretome as an attractive therapeutic target in regenerative disorders.

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