Fight Aging! Newsletter, February 20th 2023

Over the past few years, a parade of newly released gene therapies have consecutively claimed the title of most expensive drug in the world; the current honor goes to the 3.5 million hemophilia B treatment Hemgenix, launched in November 2022. Minicircle is taking something of a different tack. The startup, which is registered in Delaware, aims to fuse elements of the traditional drug testing path with the ethos of "biohackers" - medical mavericks who proudly dabble in self-experimentation and have long hailed the promise of DIY gene therapies.

The eccentricities don't end there. Minicircle's trials are going ahead in Próspera, an aspiring libertarian paradise born from controversial legislation that has allowed international businesses to carve off bits of Honduras and establish their own micronations. It's a radical experiment that is allowing a private company to take on the role of the state. While much attention has been paid to the charter city's use of Bitcoin as legal tender, the partnership with Minicircle is an important milestone toward another goal - becoming a hotbed of medical innovation and a future hub of medical tourism.

It's against this unusual backdrop that Minicircle is trying to lead biohacking's charge into the mainstream, or at least somewhere near it-studying gene therapies that target familiar conditions like muscular disorders, HIV, low testosterone, and obesity, and doing so with the backing of tech moguls and under the purview of bespoke "innovation-friendly" regulation. It ultimately aims to democratize access to gene therapies, with an emphasis on discovering the right nucleic cocktail to promote longevity.

Most scientists I spoke with are less than enthusiastic about Minicircle's undertaking, expressing skepticism about its methods and aims, while experts in medical ethics are concerned about how the trials will move forward - and what they could mean for the burgeoning and sometimes unscrupulous medical tourism industry. These experts also say the red-tape-trimming stance of special economic zones like Próspera can set off alarm bells (though the charter city staunchly defends its regulations).

At least one prominent scientist sees a potential upside to growth in the biohacking space: George Church, a professor of genetics at Harvard Medical School who has previously consulted on biohacking endeavors, tells me he welcomes the evolution of biohacking self-experimentation into full-blown clinical trials. He isn't familiar with Minicircle's work specifically, but he says of the general premise, "As long as nothing goes wrong, it could herald a revolution in cost reduction." That, of course, is a big caveat.

Of the well-studied effects on lifespan in mouse models, detailed mechanisms underlying the health and longevity benefit of caloric restriction (CR) are still being investigated despite some limitations on the practical applications to humans. A major limitation of animal models is that they cannot self-report hunger or other physiological sensations that would inform mechanistic work. Since ghrelin was first described and noted as a growth hormone secretagogue receptor (GHS-R) agonist, much study has focused on the effects on hunger and appetite regulation along with other aspects of energy balance.

Investigators examining effects on cognition in mouse models have posited that the mechanism may involve interoceptive cues or signaling, rather than reduced energy intake per se. In those studies, oral administration of a ghrelin agonist (LY444711, an orally active compound that binds with high affinity to and is a potent activator of the growth hormone secretagogue receptor 1a [GHS-R1a] receptor, reduces Alzheimer's disease pathology and improves cognition in the APP-SwDI mouse model. Treatment also reduced levels of amyloid beta (Aβ) and neuroinflammation (as measured by microglial activation) at 6 months of age compared to controls, like the effect seen in the 20% CR group (gp) but with no significant difference in body weight (BW) or percentage body fat.

LY444711 binds to the human ghrelin receptor (GHS-R1a) and is a functional agonist. This agonist produced orexigenic behavior in rodents, including stimulated energy intake (food consumption is 40% than controls at 10 mg/kg and 50% greater than controls at 30 mg/kg dose), positive energy balance (23% greater BW with 2 weeks treatment at 10 mg/kg), acute higher respiratory quotient (RQ) with increased dose, and increased adiposity (greater fat mass but no significant difference in lean mass). The authors conclude this substance is orally active with an extended half-life relative to native ghrelin.

Despite various studies on ghrelin effects on food intake and body composition, studies of ghrelin agonists on lifespan-extending effects in rodent models are lacking. We tested the hypothesis that a pathway related to perceived hunger, as induced by an oral, exogenously administered orexigenic agent (i.e., a synthetic ghrelin agonist), would affect lifespan in mice. Mice aged 4 weeks were allowed to acclimate for 2 weeks prior to being assigned (N = 60/group). Prior to lights off daily, animals were fed LY444711 or a placebo control until death. Treatment (GhrAg) animals were pair-fed daily based on the group mean food intake consumed by controls (ad libitum feeding) the prior week. Results indicate an increased lifespan effect for GhrAg versus controls, which weighed significantly more than GhrAg (adjusted for baseline weight). Further studies are needed to determine the full scope of effects of this ghrelin agonist, either directly via increased ghrelin receptor signaling or indirectly via other hypothalamic, systemic, or tissue-specific mechanisms.

The CALERIE Phase-2 randomized controlled trial, funded by the US National Institute on Aging, is the first ever investigation of the effects of long-term calorie restriction in healthy, non-obese humans. The trial randomized 220 healthy men and women at three sites in the US to a 25 percent calorie-restriction or normal diet for two years. To measure biological aging in CALERIE Trial participants, the team analyzed blood samples collected from trial participants at pre-intervention baseline and after 12- and 24-months of follow-up. The team analyzed methylation marks on DNA extracted from white blood cells. DNA methylation marks are chemical tags on the DNA sequence that regulate the expression of genes and are known to change with aging.

In the primary analysis researchers focused on three measurements of the DNA methylation data, sometimes known as epigenetic clocks. The first two, the PhenoAge and GrimAge clocks, estimate biological age. The third measure studied by the researchers was DunedinPACE, which estimates the pace of aging, or the rate of biological deterioration over time. "In contrast to the results for DunedinPace, there were no effects of intervention on other epigenetic clocks. The difference in results suggests that dynamic 'pace of aging' measures like DunedinPACE may be more sensitive to the effects of intervention than measures of static biological age." The intervention effect on DunedinPACE represented a 2-3 percent slowing in the pace of aging, which in other studies translates to a 10-15 percent reduction in mortality risk, an effect similar to a smoking cessation intervention.

The geroscience hypothesis proposes that therapy to slow or reverse molecular changes that occur with aging can delay or prevent multiple chronic diseases and extend healthy lifespan. Caloric restriction (CR), defined as lessening caloric intake without depriving essential nutrients, results in changes in molecular processes that have been associated with aging, including DNA methylation (DNAm), and is established to increase healthy lifespan in multiple species. Here we report the results of a post hoc analysis of the influence of CR on DNAm measures of aging in blood samples from the Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy (CALERIE) trial, a randomized controlled trial in which n = 220 adults without obesity were randomized to 25% CR or ad libitum control diet for 2 years.

We found that CALERIE intervention slowed the pace of aging, as measured by the DunedinPACE DNAm algorithm, but did not lead to significant changes in biological age estimates measured by various DNAm clocks including PhenoAge and GrimAge. Treatment effect sizes were small. Nevertheless, modest slowing of the pace of aging can have profound effects on population health. The finding that CR modified DunedinPACE in a randomized controlled trial supports the geroscience hypothesis, building on evidence from small and uncontrolled studies, and contrasting with reports that biological aging may not be modifiable. Ultimately, a conclusive test of the geroscience hypothesis will require trials with long-term follow-up to establish effects of intervention on primary healthy-aging endpoints, including incidence of chronic disease and mortality.

Centenarians and supercentenarians with exceptional longevity are excellent models for research towards improvements of healthy life expectancy. Extensive research regarding the maintenance and reduction of epigenetic age has provided insights into increasing healthy longevity. To this end, we explored the epigenetic signatures reflecting hallmarks of exceptional healthy longevity, including avoidance of age-related diseases and cognitive functional decline.

Our findings show that the epigenetic ages of Japanese centenarians and supercentenarians were remarkably lower than their chronological ages, consistently with previous findings for Italian semi-supercentenarians, suggesting that their healthy longevity has an epigenetic basis. However, whether these epigenetic ages also reflect biological age has not yet been validated. Whether healthy longevity depends on slowing epigenetic ageing or on having a younger baseline DNA methylation state would be the next subject of interest. For our multiple-sampled centenarians and supercentenarians, the longitudinal changes in epigenetic age showed that their epigenetic ageing was slower than that indirectly inferred from the cross-sectional non-centenarian cohort. Further research comparing the longitudinal epigenetic change of centenarians and supercentenarians with non-centenarians will help to answer this question.

Our study further suggests a link between the specific epigenetic states and exceptional healthy longevity in centenarians and supercentenarians. Some epigenetic signatures in centenarians and supercentenarians were maintained at young states, whereas others were maintained at advanced (or old) states. Young-state DNA-methylation signatures were overrepresented around cancer-related and neuropsychiatric disease-related genes. Conversely, CpG sites with accelerated (advanced) demethylation were also detected in centenarians and supercentenarians. Knowledge-based analyses indicated that some of these demethylated CpG sites can affect the activity of TGF-β, a major anti-inflammatory cytokine. Given that many age-related diseases can develop as a consequence of excessive pro-inflammatory responses, anti-inflammatory responses, such as those mediated by TGF-β and other cytokines, are crucial for healthy ageing and longevity. For instance, immunoassays have identified greater TGF-β activity in centenarians than in younger controls.

Because plaques are visible under a microscope, scientists long believed that they are responsible for damaging neurons in Alzheimer's disease etiology. Many clinical trials took place and billions in funding were invested over more than a quarter of a century to generate molecules and antibodies targeting and preventing formation of fibrils and plaques. Such treatments proved unsuccessful and caused intolerable side effects. Over time, fibrils and plaques themselves were deemed non-toxic, and instead earlier soluble intermediates known as oligomers are now considered the culprits in this insidious disease.

Recent clinical trials using antibodies to target oligomers have shown promising results. Researchers are now developing small cyclic peptides that have proven effective in animal models in treating the disease by targeting oligomers. When these molecules were combined in a test tube with the small protein amyloid beta, the generation of oligomers was completely blocked, and no subsequent aggregation occurred. In the next stage, the researchers incubated human neurons with the toxic oligomers and the cyclic peptides. Most neurons remained alive, but those in the control group that were exposed to the oligomers without cyclic peptides were severely damaged and died.

Next, transgenic mouse models of Alzheimer's disease in the pre-symptomatic stage were treated with the cyclic peptides and observed over time for memory functions and amount of amyloid beta oligomers in the brain. Through molecular imaging, the researchers determined that the mice didn't generate substantial amounts of oligomers and, consequently, didn't develop any sign of Alzheimer's.

SIRT3, the primary mitochondrial deacetylase, regulates the functions of mitochondrial proteins including metabolic enzymes and respiratory chain components. Although SIRT3's functions in peripheral tissues are well established, the significance of its downregulation in neurodegenerative diseases is beginning to emerge. SIRT3 plays a key role in brain energy metabolism and provides substrate flexibility to neurons. It also facilitates metabolic coupling between fuel substrate-producing tissues and fuel-consuming tissues. SIRT3 mediates the health benefits of lifestyle-based modifications such as calorie restriction and exercise.

SIRT3 deficiency is associated with metabolic syndrome (MetS), a precondition for diseases including obesity, diabetes, and cardiovascular disease. Alzheimer's disease (AD) has been reported to coexist with these diseases in aging populations. SIRT3 downregulation leads to mitochondrial dysfunction, neuroinflammation, and inflammation, potentially triggering factors of AD pathogenesis. Recent studies have also suggested that SIRT3 may act through multiple pathways to reduce plaque formation in the AD brain. In this review, we give an overview of SIRT3's roles in brain physiology and pathology and discuss several activators of SIRT3 that can be considered potential therapeutic agents for the treatment of dementia.

Cellular senescence is a complex process involving a close-to-irreversible arrest of the cell cycle, the acquisition of the senescence-associated secretory phenotype (SASP), as well as profound changes in the expression of cell surface proteins that determine the recognition of senescent cells by innate and cognate immune effectors including macrophages, NK, NKT, and T cells. It is important to note that senescence can occur in a transient fashion to improve the homeostatic response of tissues to stress. Moreover, both the excessive generation and the insufficient elimination of senescent cells may contribute to pathological aging.

Attempts are being made to identify the mechanisms through which senescent cell avoid their destruction by immune effectors. Such mechanisms involve the cell surface expression of immunosuppressive molecules including PD-L1 and PD-L2 to ligate PD-1 on T cells, as well as tolerogenic MHC class-I variants. In addition, senescent cells can secrete factors that attract immunosuppressive and pro-inflammatory cells into the microenvironment. Each of these immune evasion mechanism offers a target for therapeutic intervention, e.g., by blocking the interaction between PD-1 and PD-L1 or PD-L2, upregulating immunogenic MHC class-I molecules and eliminating immunosuppressive cell types.

In addition, senescent cells differ in their antigenic makeup and immunopeptidome from their normal counterparts, hence offering the opportunity to stimulate immune response against senescence-associated antigens. Ideally, immunological anti-senescence strategies should succeed in selectively eliminating pathogenic senescent cells but spare homeostatic senescence.

The hippocampus, a critical hub for cognition and memory, is one of the first brain regions to be affected in Alzheimer's disease (AD) patients. The dentate gyrus (DG), a hippocampal subfield implicated in learning and memory, particularly in pattern separation, shows substantial age-related functional decline in humans, non-human primates, and rodents. The DG is further unique as it contains the so-called "neurogenic niche," wherein stem cells continue to generate new neurons in the adult brain, in a special form of cellular plasticity referred to as "adult hippocampal neurogenesis" (AHN). Adult-born dentate granule cells (aDGCs) functionally incorporate into the granule cell layer of the DG as part of the hippocampal circuitry, where they, via their unique physiological properties, play key roles in neural plasticity and cognition. AHN has been shown to be impacted by (several aspects of) AD pathology in both rodents and humans.

Despite a substantial focus on amyloid and tau pathologies over the past decades, disease-modifying therapies for AD are still lacking. Hence, "mapping" the full mechanistic heterogeneity of AD, i.e. beyond amyloid and tau, is an important critical step to developing novel therapeutic targets. Key mechanistic questions as to what renders an individual vulnerable or resilient to developing AD remain unanswered, but may be "hidden" in the brains of a unique group of elderly individuals with preserved cognition, despite the presence of substantial AD pathology. This "cognitive reserve" that is apparent in these subjects may likely increase resilience toward developing dementia. Notably, AHN levels in postmortem brains were recently correlated with ante-mortem cognition in mild cognitive impaired (MCI) and AD patients, pointing toward a potential active role of AHN in the buildup of cognitive reserve, which can later on confer resilience to AD-related dementia.

Here, we critically discuss current knowledge on the putative role of AHN in AD pathophysiology and resilience, focusing primarily on the human brain. We emphasize the importance of the multicellular complexity of the neurogenic niche where AHN resides, and hence the relevance of integrating both intrinsic and extrinsic signals from distinct cellular populations, into any future therapeutic strategies aimed to "rejuvenate" the AD brain.

An increase in life expectancy in developed countries has led to an insurgency of chronic aging-related diseases. In the last few decades, several studies provided evidence of the prominent role of cellular senescence in many of these pathologies. Key traits of senescent cells include cell cycle arrest, apoptosis resistance, and secretome shift to senescence-associated secretory phenotype (SASP) resulting in increased secretion of various intermediate bioactive factors important for senescence pathophysiology. However, cellular senescence is a highly phenotypically heterogeneous process, hindering the discovery of totally specific and accurate biomarkers.

Strategies to prevent the pathological effect of senescent cell accumulation during aging by impairing senescence onset or promoting senescent cell clearance have shown great potential during in vivo studies and some are already in early stages of clinical translation. The adaptability of these senotherapeutic approaches to human application has been questioned due to the lack of proper senescence targeting and senescence involvement in important physiological functions. In this review, we explore the heterogeneous phenotype of senescent cells and its influence on the expression of biomarkers currently used for senescence detection. We also discuss the current evidence regarding the efficacy, reliability, development stage, and potential for human applicability of the main existing senotherapeutic strategies.

While it's well established that chronic mild hypoxia promotes a robust angiogenic response, we recently found that it also triggers transient blood-brain barrier (BBB) disruption, that is associated with aggregation and activation of microglia around the leaky blood vessels. Importantly, microglial depletion markedly enhanced vascular leak, demonstrating an important vasculo-protective function for microglia in maintaining BBB integrity. As a high integrity BBB is a critical determinant of cerebral health, yet evidence suggests that BBB integrity declines with age, we recently examined how aging influences both the extent of hypoxia-induced BBB disruption and the associated vasculo-protective function of microglia. This showed that compared to young (8-10 weeks) mice, the number of hypoxia-induced vascular leaks was greatly amplified (5-10 fold) in aged (20 months) mice in all regions of the brain examined.

When we analysed the impact of aging on microglia activity, we discovered an interesting paradox. On the one hand, microglia in aged brain were far more activated as assessed by morphological criteria and expression of activation markers such as Mac-1 and CD68, but on the other hand, they displayed a marked deficit in the ability to aggregate around leaky blood vessels. These findings are consistent with the work of others who showed microglia in aged brain are typically more activated than in young mice. Interestingly, microglia in the aged brain can be re-programmed by removing all microglia with the colony stimulating factor-1 receptor (CSF-1R) antagonist PLX5622, and then allowing the central nervous system to repopulate with new microglia displaying a younger phenotype. Notably, this approach was shown to reverse age-related cognitive decline, although vascular integrity was not examined.

In our study we took the simpler approach of reducing microglial activation state in the aged brain by treating mice with minocycline and this successfully reduced the number of hypoxia-induced vascular leaks. Based on these data, we proposed a biphasic relationship between microglial activation and vasculo-protection, such that microglia need to become activated to confer protection, but if they become too activated, as in the aged brain, this protection declines.

MLKL is one of the core signaling proteins of the inflammatory cell death pathway, necroptosis, which is a known mediator and modifier of human disease. Necroptosis has been implicated in the progression of disease in almost every physiological system and recent reports suggest a role for necroptosis in aging. Here, we present the first comprehensive analysis of age-related histopathological and immunological phenotypes in a cohort of Mlkl-/- mice on a congenic C57BL/6J genetic background.

Our extensive histopathological and immunophenotypic cohort analyses have identified several unique, sex-specific, differences between congenic C57BL/6J Mlkl-/- mice and their wild-type littermates that emerge with age. Several statistically significant findings were observed in hematological parameters across age in Mlkl-/- mice compared to wild-type littermate controls. Many of these parameters remained within normal range despite statistical significance, suggesting they are unlikely to assert biologically critical roles.

Of note, Mlkl-/- mice exhibit increased circulating lymphocyte numbers relative to wild-type littermates at 12-14 months of age. A comprehensive and unbiased blind scoring of inflammatory foci in more than 44 different sites revealed a 62% decrease in background, sterile inflammation of the skeletal muscle, bone, cartilage, adipose tissue, and connective tissue proper in 17-month-old female Mlkl-/- relative to age-matched wild-type littermates. It is important to consider, however, that these differences in age-related circulating lymphocyte numbers and tissue inflammation did not manifest in any overt differences in the general condition, mobility, or mortality of these mice up to 17 months of age.

Scientists working on an experimental anti-ageing therapy claim to have broken a record by extending the lifespan of a lab rat called Sima. Named after the Hindi word for "limit" or "boundary", Sima is the last remaining survivor from a group of rodents that received infusions of blood plasma taken from young animals to see if the treatment prolonged their lives. Sima, who was born on 28 February 2019, has lived for 47 months, surpassing the 45.5 months believed to be the oldest age recorded in scientific literature for a female Sprague-Dawley rat, the researchers say. So far, Sima has outlived her closest rival in the study by nearly six months.

Researchers have rushed to produce and trial therapies based on young blood plasma after numerous experiments found that infusions could reinvigorate ageing organs and tissues. The results from the latest study will be written up when Sima dies, but data gathered so far suggests that eight rats that received placebo infusions of saline lived for 34 to 38 months, while eight that received a purified and concentrated form of blood plasma, called E5, lived for 38 to 47 months. They also had improved grip strength. Rats normally live for two to three years, though a contender for the oldest ever is a brown rat that survived on a restricted calorie diet for 4.6 years.

Results from such small studies are tentative at best, but some scientists believe the work, and similar efforts by others, has potential. A preliminary study found that infusions of young blood plasma wound back the biological clock on rat liver, blood, heart and a brain region called the hypothalamus. A patent filing on the potential therapy describes how plasma from young mammals is purified and concentrated before use. Some components, such as platelets, are removed, as they can trigger immune reactions.

Neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and Huntington's disease, are heavy burdens to global health and economic development worldwide. Mounting evidence suggests that exercise has a positive impact on the life quality of elderly with neurodegenerative diseases. Three major databases were searched related to current studies in exercise intervention on neurodegenerative diseases using omics tools, including metabolomics, metagenomics, genomics, transcriptomics, and proteomics. We summarized the omics features and potential mechanisms associated with exercise and neurodegenerative diseases in the current studies. Three main mechanisms by which exercise affects neurodegenerative diseases were summed up, including adult neurogenesis, brain-derived neurotrophic factor (BDNF) signaling, and short-chain fatty acids (SCFAs) metabolism.

Overall, there is compelling evidence that exercise intervention is a feasible way of preventing the onset and alleviating the severity of neurodegenerative diseases. These studies highlight the importance of exercise as a complementary approach to the treatment and intervention of neurodegenerative diseases in addition to traditional treatments. More mechanisms on exercise interventions for neurodegenerative diseases, the specification of exercise prescriptions, and differentiated exercise programs should be explored so that they can actually be applied to the clinic.

In a healthy organism, the homeostasis of the central nervous system (CNS) is dependent on the interactions of various nerve cells. However, in the CNS of Parkinson's disease (PD) patients, there is an aberrant build-up of α-synuclein (α-Syn) and a cascade effect of gradual neuronal damage that breaks the appropriate balance, which leads to inflammation in the CNS. Autophagy is an evolutionarily conserved degradation pathway that is responsible for the digestion and recycling of the majority of intracytoplasmic proteins and organelles. Autophagy maintains homeostasis by delivering cytoplasmic materials to the lysosome for degradation. Due to poor autophagy, inappropriately aggregated α-Syn in the CNS of PD patients cannot be removed and accumulated. Overall, dysregulation of autophagy is thought to play an important role in the abnormal aggregation of α-Syn and the exacerbation of Parkinson's disease.

Microglia are CNS-specific immune cells that play an immunological role in the CNS comparable to that of macrophages, interact with neurons, and conduct a variety of tasks in the CNS. Recent research shows that microglial autophagy is involved in the function and regulation of inflammation in the CNS. These findings implied that dysregulation of autophagy in microglia may impact innate immune activities, including phagocytosis and inflammation, which, in turn, contribute to illnesses associated with neuroinflammation. To date, many researchers have considered PD to be a neuroinflammatory disease, and the role of microglial autophagy in the pathophysiology of PD has been a hot issue in the field. In this review, we present and highlight the contribution of microglial autophagy to the pathological mechanism of PD and aimed to determine whether microglial autophagy could be a potential target for therapeutic intervention.