Fight Aging! Newsletter, November 9th 2020

2020 brought unprecedented challenges as a pandemic swept the globe, leaving more than a million dead and others isolated and fearful in their homes. Through all the updates on the sick and the dead, on testing and public health guidance, one constant remains: by far the greatest predictor of death from COVID-19 is age. Most of the co-morbidities that drive COVID severity are pathologies of aging. Flattening the "demographic curve" of degenerative aging would reduce the impact of COVID-19 to roughly that of an average recent flu season, while also reducing the staggering toll of age-related disease and death that continues to inflict suffering on humankind.

Ending that toll is our mission. At SENS Research Foundation, we develop rejuvenation biotechnologies: new therapies that will repair the accumulated cellular and molecular damage in our tissues and restore youthful function.

As we reflect on the past year, we're particularly grateful to the many donors whose steadfast commitment to our work endured through economic uncertainty, to those who have become SRF Patrons by pledging to support us with recurring donations, and to the new donors who have joined our cause. You've provided a steady income stream allowing SRF to continue to fight age-related disease during the uncertainty of 2020. We appreciate you more than we can say. We know you share our vision and passion for extending healthy lifespans.

With your support, we funded research establishing systems that may accelerate progress toward novel therapies against COVID-19 as well as lung and brain aging. With your support, we explored ways to address dementia by rejuvenating the neocortex. With your support, we fight hard to reverse aging by sponsoring research, educating new scientists, and providing outreach to the public and industry partners. With your support, we can break free of age-related disease. With your support, we can #UnlockLongevity together.

SENS Research Foundation's 2020 End of Year Fundraising Campaign runs through December 31st.

Focusing ultrasound energy on a target site in the body to generate heat can burn and destroy the tissue in the site without a surgical procedure. This method is clinically applied to treat uterine fibroids, prostatic hyperplasia, prostate cancer, metastatic bone tumor and other types of tumor to destroy tumor cells using heat. However, there is a potential problem that the surrounding tissue may be burned in the process due to heat diffusion.

In 2019 a research team confirmed the possibility of precisely fractionating target tumor cells, as though it is cut out using a knife, without causing heat damage to any other part of the body by using high-intensity focused ultrasound (HIFU), an ultrasound with an acoustic pressure that is much more powerful than existing ultrasound. In the process of physically destroying the tissue without the use of heat, a boiling vapor bubble is generated at the target site of the HIFU, and it is by the kinetic energy of this primary vapor bubble that the target tumor tissue gets destroyed. However, during the process, cavitation bubble clouds can be subsequently generated between the boiling bubble and the HIFU transducer, leading to unwanted cell destruction. This made it necessary to identify the cause of their formation and to accurately predict the locations of their occurrence.

Results showed that the secondary generation of bubbles was caused by a constructive interference of the backscattered shockwave by the boiling bubble with the incoming incident shockwaves and it is within the range of this interference that the secondary bubbles formed. Based on the images obtained using a high-speed camera, it was found that the area where the interference occurred and the area where the secondary bubbles were generated were closely matched. These findings not only explain the mechanism behind the secondary bubbles formation but also help predict where they will occur, thereby presenting the possibility of destroying target tissue with greater safety and precision.

Boiling histotripsy is a High Intensity Focused Ultrasound (HIFU) technique which uses a number of short pulses with high acoustic pressures at the HIFU focus to induce mechanical tissue fractionation. In boiling histotripsy, two different types of acoustic cavitation contribute towards mechanical tissue destruction: a boiling vapour bubble and cavitation clouds. An understanding of the mechanisms underpinning these phenomena and their dynamics is therefore paramount to predicting and controlling the overall size of a lesion produced for a given boiling histotripsy exposure condition. A number of studies have shown the effects of shockwave heating in generating a boiling bubble at the HIFU focus and have studied its dynamics under boiling histotripsy insonation. However, not much is known about the subsequent production of cavitation clouds that form between the HIFU transducer and the boiling bubble.

The main objective of the present study is to examine what causes this bubble cluster formation after the generation of a boiling vapour bubble. Our results suggest that the formation of a cavitation cloud in boiling histotripsy is a threshold effect which primarily depends (a) the size and location of a boiling bubble, and (b) the sum of the incident field and that scattered by a bubble.

During a heart attack, or myocardial infarction (MI), a blocked artery and the resulting oxygen deprivation cause massive cardiac cell death, blood vessel impairment, and inflammation. To effectively treat MI, lost heart muscle tissue must regenerate and new blood vessels must form to restore oxygen and nutrients to cells. Scientists have tried to develop patches containing various therapeutic cells to treat MI, but so far most have been too cumbersome to make, or they don't restore both cardiac muscle and blood supply to the injured site. Researchers previously developed a relatively easy-to-make pre-vascularized cardiac patch, which contained engineered microvessels in a fibrin gel spiked with cardiac stromal cells. When implanted into rats after an MI, the cells in the patch secreted growth factors that made cardiac muscle and blood vessels regrow. Now, the researchers wanted to test the patch further in rats, as well as in pigs, which have cardiovascular systems more similar to humans than those of rodents.

The researchers implanted the cardiac patch in rats that recently had a heart attack. Four weeks later, rats that received the patch had less scar tissue, increased cardiac muscle, and improved cardiac pump function compared with untreated rats. The team observed similar effects in pigs that had undergone MI and were treated with the patches. The patch increased recruitment of the pigs' progenitor cells to the damaged area and enhanced the growth of new blood vessels, as well as decreased cardiac cell death and suppressed inflammation. Although prior studies have used blood vessel-forming cells or natural blood vessels to vascularize cardiac patches, this study is the first to demonstrate the success of pre-vascularized cardiac stromal cell patches using microengineered synthetic blood vessels for treating MI in a large animal model.

The vascularized cardiac patch strategy is promising for ischemic heart repair after myocardial infarction (MI), but current fabrication processes are quite complicated. Vascularized cardiac patches that can promote concurrent restoration of both the myocardium and vasculature at the injured site in a large animal model remain elusive. The safety and therapeutic benefits of a cardiac stromal cell patch integrated with engineered biomimetic microvessels (BMVs) were determined for treating MI. By leveraging a microfluidic method employing hydrodynamic focusing, we constructed the endothelialized microvessels and then encapsulated them together with therapeutic cardiosphere-derived stromal cells (CSCs) in a fibrin gel to generate a prevascularized cardiac stromal cell patch (BMV-CSC patch).

We showed that BMV-CSC patch transplantation significantly promoted cardiac function, reduced scar size, increased viable myocardial tissue, promoted neovascularization, and suppressed inflammation in rat and porcine MI models, demonstrating an enhanced therapeutic efficacy in comparison to conventional cardiac stromal cell patches. BMV-CSC patches did not increase renal and hepatic toxicity or exhibit immunogenicity. We noted a significant increase in endogenous progenitor cell recruitment to the peri-infarct region of the porcine hearts treated with BMV-CSC patch as compared to those that received control treatments. These findings establish the BMV-CSC patch as a novel engineered-tissue therapeutic for ischemic tissue repair.

Researchers have proposed that cellular senescence variations during the aging process could lead to control of health and onset of age-related diseases. Based on the characteristics of the secretion of inflammatory cytokines released by aged cells, they hypothesize that there are at least four distinct states of cellular senescence, and that these four states arise from coordinated metabolic and epigenomic changes. The states: 1. initiation (proliferation arrest), 2. early (anti-inflammation), 3. full (increased inflammation and metabolism), and 4. late (decreased inflammation and metabolism). Characterizing and categorizing qualitatively different states of cellular senescence could provide a new understanding of the aging and senescence process.

Many of the cells that make up the body eventually decline in function and stop growing after repeated divisions in a process called "cellular senescence," an important factor in health and longevity. Premature senescence occurs when genomic DNA is damaged by stressors such as radiation, ultraviolet light, or drugs, but its mechanisms are not yet fully understood. It can be good, like when cells become cancerous, cellular senescence works to prevent the development of malignancy, but it also increases the likelihood of many age-related diseases. It is therefore important for medical science to try to understand and control it.

Although senescent cells lose their ability to proliferate, recent research has shown that they secrete various proteins that act on surrounding cells and promote chronic inflammation and cancer cell growth. This is called the senescence-associated secretory phenotype (SASP). Cellular senescence is thought to be the cause of aging in the entire body. Senescent cells have been shown to accumulate in the bodies of aged mice, and removal of these cells may suppress whole-body aging. In other words, if cellular senescence is controlled, it may become possible to regulate the aging process of the whole body.

Cellular senescence involves at least four distinguishable states in chronological order (initiation, and early, full, and late senescence), which are especially classified by metabolism and SASP features. Under the action of senescenceinducing stresses, the p53-p21 CIP1 and p16 INK4a -retinoblastoma (RB) pathways cause cell cycle arrest at senescence initiation. In early senescence, transforming growth factor (TGF)β is produced possibly for anti-inflammatory defense at least in part via the Notch1-mediated pathway (TGFβ SASP) with increasing morphological changes such as an enlarged cell size.

Then, in full senescence, metabolic activation yields many metabolites, cellular energy, and reactive oxygen species that accelerate senescence progression with secretion of proinflammatory cytokines such as IL-6 and IL-8 (proinflammatory SASP). The levels of proinflammatory SASP tend to be high in oncogene-induced senescence, and low in replicative senescence. Microscopically, fully senescent cells often exhibit cytoplasmic SA β-Gal positivity and nuclear SAHF.

Finally, interferon secretion and metabolic decline occur in late senescence (interferon SASP). In full to late senescence, accumulation of cytoplasmic DNAs activates the cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) pathway for cytosolic DNA sensing and the interferon response. Thus, there are at least four different states of cellular senescence, suggesting that senescent cells diversely have metabolic and secretory phenotypes.

Skin aging has been primarily related to aesthetics and beauty. Therefore, interventions have focused on reestablishing skin appearance, but not necessarily skin health, function, and resilience. Recently, cellular senescence was shown to play a role in age-related skin function deterioration and influence organismal health and, potentially, longevity.

In the present study, a two-step screening was performed to identify peptides capable of reducing cellular senescence in human dermal fibroblasts (HDF) from Hutchinson-Gilford Progeria (HGPS) patients. From the top four peptides of the first round of screening, we built a 764-peptide library using amino acid scanning, of which the second screen led to the identification of peptide 14. Peptide 14 effectively decreased HDF senescence induced by HGPS, chronological aging, ultraviolet-B radiation, and etoposide treatment, without inducing significant cell death, and likely by modulating longevity and senescence pathways.

We further validated the effectiveness of peptide 14 using human skin equivalents and skin biopsies, where peptide 14 promoted skin health and reduced senescent cell markers, as well as the biological age of samples, according to the Skin-Specific DNA methylation clock, MolClock. Topical application of peptide 14 outperformed Retinol treatment, the current gold-standard in "anti-aging" skin care. Finally, we determined that peptide 14 is safe for long-term applications and also significantly extends both the lifespan and healthspan of C. elegans worms tested in two independent testings. This highlights the potential for geroprotective applications of the senotherapeutic compounds identified using our screening platform beyond the skin.

Researchers discovered that limiting the open time of a channel called the ryanodine receptor, which acts like a gateway to cells located in the heart and brain, reverses and prevents progression of Alzheimer's disease in animal models. A single RyR2 point mutation, which reduces RyR2 open time, prevents hyperexcitability, hyperactivity, memory impairment, neuronal cell death, and dendritic spine loss in an Alzheimer's disease mouse model.

Researchers also identified a drug, derived from the heart medication carvedilol, that interrupts the disease process by reducing the open type of the ryanodine receptor. The effect of giving the drug to animal models was remarkable: After one month of treatment, the memory loss and cognitive impairments in these models disappeared.

Previous research has shown that the progression of Alzheimer's disease is driven by a vicious cycle of the protein amyloid β (Aβ) inducing hyperactivity at the neuron level. However, the mechanism behind this wasn't fully understood nor were there effective treatments to stop the cycle. Here, the team used a portion of an existing drug used for heart patients, carvedilol, to treat mice models with Alzheimer's symptoms. "We treated them for a month and the effect was quite amazing. We couldn't tell the drug-treated disease models and the healthy models apart."

Prior research has shown that physical activity can prevent unhealth as well as improve the prognosis of several diseases including various forms of cancer. Exactly how exercise exerts its protective effects against cancer is, however, still unknown, especially when it comes to the biological mechanisms. One plausible explanation is that physical activity activates the immune system and thereby bolsters the body's ability to prevent and inhibit cancer growth.

Researchers expanded on this hypothesis by examining how the immune system's cytotoxic T cells, that is white blood cells specialized in killing cancer cells, respond to exercise. They divided mice with cancer into two groups and let one group exercise regularly in a spinning wheel while the other remained inactive. The result showed that cancer growth slowed and mortality decreased in the trained animals compared with the untrained. Next, the researchers examined the importance of cytotoxic T cells by injecting antibodies that remove these T cells in both trained and untrained mice. The antibodies knocked out the positive effect of exercise on both cancer growth and survival, which according to the researchers demonstrates the significance of these T cells for exercise-induced suppression of cancer. The researchers also transferred cytotoxic T cells from trained to untrained mice with tumors, which improved their prospects compared with those who got cells from untrained animals.

To examine how exercise influenced cancer growth, the researchers isolated T cells, blood and tissue samples after a training sessions and measured levels of common metabolites that are produced in muscle and excreted into plasma at high levels during exertion. Some of these metabolites, such as lactate, altered the metabolism of the T cells and increased their activity. The researchers also found that T cells isolated from an exercised animal showed an altered metabolism compared to T cells from resting animals. In addition, the researchers examined how these metabolites change in response to exercise in humans. They took blood samples from eight healthy men after 30 minutes of intense cycling and noticed that the same training-induced metabolites were released in humans.

Skeletal muscle regeneration depends on a muscle stem cell population (satellite cells) in a dormant or quiescent state, a situation that can be triggered by damage or stress to form new muscle fibres and expand in new stem cells. The regenerative functions of these stem cells are known to decline with ageing. Researchers have found in experiments with mice that all muscle stem cells, despite being quiescent, are not equal, and have identified a subgroup that maintains its regenerative capacity over time, declining only at geriatric age.

The researchers have shown that this subgroup of quiescent stem cells has a greater regenerative capacity through the activation of the FoxO signalling pathway (previously associated with longevity), which maintains the expression of a youthful gene programme throughout life; however, at geriatric age, FoxO activation in this subgroup of cells is lost, causing their loss of functionality.

According to the results, compounds that activate FoxO may have a rejuvenating effect on aged muscle stem cells, opening the way to improve the health of elderly people who are debilitated by the loss of muscle mass. It may also be useful for persons who have lost muscle mass as a result of neuromuscular diseases or effects associated with cancer or infectious or inflammatory diseases.

Using a mouse model, researchers discovered a new type of immune cell that not only rescues damaged nerve cells from death, but partially reverses nerve fiber damage. The research team also identified a human immune cell line, with similar characteristics, that promotes nervous system repair. "This immune cell subset secretes growth factors that enhance the survival of nerve cells following traumatic injury to the central nervous system. It stimulates severed nerve fibers to regrow in the central nervous system, which is really unprecedented."

The cell discovered by these researchers is a granulocyte, a type of white blood cell that has small granules. The most common granulocytes, neutrophils, normally help the body fight off infection. The unique cell type resembles an immature neutrophil but is distinctive in possessing neuroprotective and neuroregenerative properties. It drives central nervous system axon (nerve) regrowth in vivo, in part through the secretion of a cocktail of growth factors. "We found that this pro-regenerative neutrophil promotes repair in the optic nerve and spinal cord, demonstrating its relevance across central nervous system compartments and neuronal populations. A human cell line with characteristics of immature neutrophils also exhibited neuroregenerative capacity, suggesting that our observations might be translatable to the clinic."

Researchers demonstrated the therapeutic potency of the immature neutrophil subset by injecting them into mice with crush injury to the optic nerve or lacerated nerve fibers in the spinal cord. Mice injected with the new neutrophil subset, but not more typical mature neutrophils, grew new nerve fibers.

Skeletal muscle stem cells (satellite cells) are well known to participate in regeneration and maintenance of the tissue over time. Studies have shown increases in the number of satellite cells after exercise, but their functional role in endurance training remains unexplored. In this study, young adult mice were submitted to endurance exercise training and the function, differentiation, and metabolic characteristics of satellite cells were investigated in vivo and in vitro.

We found that injured muscles from endurance-exercised mice display improved regenerative capacity, demonstrated through higher densities of newly formed myofibres compared with controls (evidenced by an increase in embryonic myosin heavy chain expression), as well as lower inflammation (evidenced by quantifying CD68-marked macrophages), and reduced fibrosis. Enhanced myogenic function was accompanied by an increased fraction of satellite cells expressing self-renewal markers, while control satellite cells had morphologies suggestive of early differentiation.

The beneficial effects of endurance exercise were associated with satellite cell metabolic reprogramming, including reduced mitochondrial respiration (O2 consumption) under resting conditions (absence of muscle injury) and increased stemness. During proliferation or activated states (3 days after injury), O2 consumption was equal in control and exercised cells, while exercise enhanced myogenic colony formation. Surprisingly, inhibition of mitochondrial O2 consumption was sufficient to enhance muscle stem cell self-renewal characteristics in vitro. Moreover, transplanted muscle satellite cells from exercised mice or cells with reduced mitochondrial respiration promoted a significant reduction in inflammation compared with controls.

Our results indicate that endurance exercise promotes self-renewal and inhibits differentiation in satellite cells, an effect promoted by metabolic reprogramming and respiratory inhibition, which is associated with a more favourable muscular response to injury.

The striatum is part of the basal ganglia - a collection of brain centers linked to habit formation, control of voluntary movement, emotion, and addiction. For several decades, researchers have studied clusters of cells called striosomes, which are distributed throughout the striatum. Their function had remained mysterious, in part because they are so small and deep within the brain that it is difficult to image them with functional magnetic resonance imaging.

In recent years, researchers have discovered that striosomes play an important role in a type of decision-making known as approach-avoidance conflict. These decisions involve choosing whether to take the good with the bad - or to avoid both - when given options that have both positive and negative elements. An example of this kind of cost-benefit decision is having to choose whether to take a job that pays more but forces a move away from family and friends. Such decisions often provoke great anxiety.

In a related study, researchers found that striosomes connect to cells of the substantia nigra, one of the brain's major dopamine-producing centers. These studies led the researchers to hypothesize that striosomes may be acting as a gatekeeper that absorbs sensory and emotional information coming from the cortex and integrates it to produce a decision on how to act. These actions can then be invigorated by the dopamine-producing cells.

Researchers found that in older mice (between 13 and 21 months, roughly equivalent to people in their 60s and older), the mice's engagement in learning this type of cost-benefit analysis went down. At the same time, their striosomal activity declined compared to that of younger mice. The researchers found a similar loss of motivation in a mouse model of Huntington's disease, a neurodegenerative disorder that affects the striatum and its striosomes. When the researchers used genetically targeted drugs to boost activity in the striosomes, they found that the mice became more engaged in performance of the task. Conversely, suppressing striosomal activity led to disengagement. The researchers are now working on possible drug treatments that could stimulate this circuit.

Altered NAD+ homeostasis has been linked to multiple diseases affecting different organs, including the brain and nervous system, liver, heart and kidney. NAD+ depletion is a hallmark of ageing and numerous age-related disorders. Therefore, boosting NAD+ offers a promising option for enhancing resilient to aging or diseases, thereby extending a healthy lifespan. The NAD+ level can be elevated by dietary supplementation of NAD+ precursors, such as tryptophan, niacin (NA), nicotinamide mononucleotide (NMN), and nicotinamide riboside (NR), inhibition of NAD+-consuming enzymes, including PARP1 and CD38, management of the NAD+ biosynthesis via controlling NAD+-biosynthesis enzymes, or improving NAD+ bioavailability through exercise and caloric restriction.

NAD+ precursors can be used as a nutritional supplement to improve a broad spectrum of physiological functions and pathological processes. The therapeutic and preventive efficacy of NAD+ boosters, especially the soluble and orally bioavailable endogenous molecules NR, nicotinamide (NAM), and NA, have been assessed in a series of clinical trials in humans. Findings suggest that elevating NAD+ levels by administration of NAD+ precursors, including NMN, NR, NAM, and NA, is a rational therapeutic strategy to improve a healthy lifespan. Given that NAD+-depleting drugs exhibit anti-tumor potential due to their impact on DNA repair and inflammation, long-term boosting NAD+ might increase the risk of driving tumor growth. Moreover, the detrimental side effects of NAD+ and its intermediates may be caused by the NAD+-dependent sirtuins that have both oncogenic and tumor suppressive activity in different contexts. Consistent with this hypothesis, NMN treatment accelerates pancreatic cancer progression via creating an inflammatory environment. Thus, future clinical studies are necessary to assess the long-term safety of NAD+ precursors in human therapeutics.

The levels and compartmentalization of NAD+ dictate energy state that impinges on normal physiological and biological responses, as indicated by the regulatory role of NAD+ in proper redox homeostasis, genomic stability, gene expression, circadian clock, inflammation, metabolism, cellular bioenergetics, mitochondrial homeostasis, and adaptive stress responses. A healthy lifestyle and exercise are non-pharmacologic strategies to improve the body's resilience and extend healthy lifespan through enhancing NAD+ levels. NAD+ boosters can be applied for a broad spectrum of NAD+ deficiency related pathologies, such as infection, cancer, metabolic diseases, acute injury, aging, and aging-related neurodegenerative disorders. Conceivably, this could be achieved by boosting NAD+ via enhancing the NAD+ generation and diminishing NAD+ consumption.

Despite exciting and emerging strides in NAD+ biology, there are a variety of outstanding questions that warrant future systematic exploitation to accelerate the translation of remarkable bench work to effective clinical application in humans. The first interesting question is that the precise mechanisms executing the beneficial effects of NAD+ and its metabolites on pathologies and lifespan remain elusive. Further investigation understanding the landscape of NAD+ in response to diseases and identifying the specific effector molecules for each NAD+ precursors at different time points provide critical insights into development of effective interventions for various physiologies. Secondly, the systemic NAD+ metabolome is largely unexplored. Are there any tissue specificities for NAD+ boosting, such tissue preferences of distinct NAD+ precursors? What is the crosstalk with the NAD+ systems of each organ? What is the distinct NAD+ metabolome in each tissue? In spite of growing interest in the use of NAD+ precursors as a strategy for healthy aging, the in vivo pharmacokinetics remain poorly understood.

Metabolic syndrome is characterized by central obesity, insulin resistance, elevated blood pressure, and dyslipidemia. Metabolic syndrome is a significant risk factor for several common cancers (e.g., liver, colorectal, breast, pancreas). Pharmacologic treatments used for the components of the metabolic syndrome appear to be insufficient to control cancer development in subjects with metabolic syndrome. Murine models showed that cancer has the slowest progression when there is no food consumption during the daily activity phase. Intermittent fasting from dawn to sunset is a form of fasting practiced during human activity hours. To test the anticancer effect of intermittent fasting from dawn to sunset in metabolic syndrome, we conducted a pilot study in 14 subjects with metabolic syndrome who fasted (no eating or drinking) from dawn to sunset for more than 14 hours daily for four consecutive weeks.

We collected serum samples before 4-week intermittent fasting, at the end of 4th week during 4-week intermittent fasting and 1 week after 4-week intermittent fasting. We performed serum proteomic analysis using nano ultra-high performance liquid chromatography-tandem mass spectrometry. We found a significant fold increase in the levels of several tumor suppressor and DNA repair gene protein products (GP)s at the end of 4th week during 4-week intermittent fasting (CALU, INTS6, KIT, CROCC, PIGR), and 1 week after 4-week intermittent fasting (CALU, CALR, IGFBP4, SEMA4B) compared with the levels before 4-week intermittent fasting. We also found a significant reduction in the levels of tumor promoter GPs at the end of 4th week during 4-week intermittent fasting (POLK, CD109, CAMP, NIFK, SRGN), and 1 week after 4-week intermittent fasting (CAMP, PLAC1) compared with the levels before 4-week intermittent fasting.

Fasting from dawn to sunset for four weeks also induced an anti-diabetes proteome response by upregulating the key regulatory proteins of insulin signaling at the end of 4th week during 4-week intermittent fasting (VPS8, POLRMT, IGFBP-5) and 1 week after 4-week intermittent fasting (PRKCSH), and an anti-aging proteome response by upregulating H2B histone proteins 1 week after 4-week intermittent fasting. Subjects had a significant reduction in body mass index, waist circumference, and improvement in blood pressure that co-occurred with the anticancer, anti-diabetes, and anti-aging serum proteome response. These findings suggest that intermittent fasting from dawn to sunset actively modulates the respective genes and can be an adjunct treatment in metabolic syndrome. Further studies are needed to test the intermittent fasting from dawn to sunset in the prevention and treatment of metabolic syndrome-induced cancers.

Although the ε2 allele of apolipoprotein E (APOE2) benefits longevity, its mechanism is not understood. The protective effects of the APOE2 on Alzheimer's disease (AD) risk, particularly through their effects on amyloid or tau accumulation, may confound APOE2 effects on longevity. Herein, we showed that the association between APOE2 and longer lifespan persisted irrespective of AD status, including its neuropathology, by analyzing clinical datasets as well as animal models.

Notably, APOE2 was associated with preserved activity during aging, which also associated with lifespan. In animal models, distinct apoE isoform levels, where APOE2 has the highest, were correlated with activity levels, while some forms of cholesterol and triglycerides were associated with apoE and activity levels. These results indicate that APOE2 can contribute to longevity independent of AD. Preserved activity would be an early-observable feature of APOE2-mediated longevity, where higher levels of apoE2 and its-associated lipid metabolism might be involved.

Genetic mutants have been observed with lifespan, up to ten times longer compared to wild type in C. elegans, and up to 150% and 46% in D. melanogaster and M. musculus, respectively. In model organisms, at least 2,205 genes have been identified to produce a long-lived or short-lived phenotype when mutated, knocked down, or overexpressed. A comprehensive list of these longevity-associated genes (LAGs), including more detailed information about lifespan experiments, can be found in the GenAge database.

This type and amount of data have made it possible to perform higher-level analyses, and the collection of LAGs in public repositories has significantly pushed biogerontology towards more integrative approaches to study longevity. One important aspect observed is that many LAGs seem to act in a cooperative manner and are not independent regulators of lifespan. In fact, in most cases when combining two or more genetic interventions, the effect is rarely additive, as genes are generally epistatic and interact in nonlinear ways. While in most cases combined interventions seem to have lower than expected results in how much they extend lifespan, there are also a minority of cases where genes act synergistically. Even so, the much more common case is that of studies where partially dependent gene interactions are revealed, making it even more important to understand and predict genetic dependencies.

Unfortunately, data on epistasis is much harder to obtain through wide-screen experimental studies, which has been for example the case for the discovery of most LAG interventions in worms. The main impediment comes from the combinatorial explosion of multiple gene groups for which lifespan assays would need to be measured in a "blind" search, through wet-lab experiments. A more efficient approach is to use existing epistasis data to explore predicted synergies in guided lifespan experiments. Fortunately, an accumulating number of papers has been published in the last two decades with reported lifespans for double, triple, and even quadruple mutants. As such, it has been now possible for us: (i) to collect the data from existing studies containing lifespan records for strains that have multiple genes modulated, and (ii) to create an intuitive, network-based tool, which allows users to explore in a fast, visual and interactive way the lifespan relationships between these strains.

As a step towards applying predictive methods, but also to provide information for a guided design of epistasis lifespan experiments, we developed SynergyAge - a database containing genetic and lifespan data for animal models obtained through multiple longevity-modulating interventions. The studies included in SynergyAge focus on the lifespan of animal strains which are modified by at least two genetic interventions, with single gene mutants included as reference. SynergyAge, which is publicly available, provides an easy to use web-platform for browsing, searching and filtering through the data, as well as a network-based interactive module for visualization and analysis.