Fight Aging! Newsletter, July 11th 2022

A prominent aging-associated condition is a chronic inflammation referred to as "inflammaging," a pro-inflammatory phenotype that accompanies aging in mammals. Inflammaging is a highly significant risk factor for most, if not all, aging-related diseases including obesity and type 2 diabetes, cardiovascular diseases, Alzheimer's disease, and cancer, as well as vulnerability to infectious disease and vaccine failure.

Dietary restriction (DR) decreases the calorie intake without inducing malnutrition. Lifetime DR is a non-pharmacological intervention that can extend the lifespan in a wide range of organisms. It has been shown that long-term DR (LTDR) also reduces some aspects of inflammation, leading to the hypothesis that a life-long energy accumulation can be the origin of chronic inflammation. A very recent study carried out in rats has shown that late-life DR attenuated aging-related changes in cell type composition and gene expression, and reversed the aging-associated increase of senescence markers and alterations of the immune system. However, it is still largely unknown which signaling pathways and networks regulate the induction of inflammaging across tissues and whether DR could have an impact on rescuing such systemic induction of inflammaging.

In this study we employ a transcriptome-wide and multi-tissue approach to analyze the influence of both LTDR and short-term DR (STDR) at old age on the aging phenotype. We were able to characterize a common transcriptional gene network driving inflammaging in most of the analyzed tissues. This network is characterized by chromatin opening and upregulation in the transcription of innate immune system receptors and by activation of interferon signaling through interferon regulatory factors, inflammatory cytokines, and Stat1-mediated transcription. We also found that both DR interventions ameliorate this inflammaging phenotype, albeit with some differences mainly at tissue-specific level. Further chromatin accessibility analysis showed that DR can also rescue the aging-associated epigenetic alteration on the inflammaging-related genes, but not the genome-wide impairment of chromatin that accompanies old cells.

In this study, we showed that aging changed the transcriptome of different tissues and that DR was able to partially rescue the age transcriptome. DR intervention in late life has been recently shown to not provide as beneficial effects as long-life DR in lifespan and healthspan extension. For this reason, we compare old mice with mice treated with both a lifetime DR (LTDR) and a short-term DR at late life (STDR). We found that responses to the aging, LTDR, and STDR both in magnitude and functional aspects were tissue specific. LTDR has been previously shown to strongly prevent a pro-inflammatory phenotype in aged white adipose tissue pre-adipocytes, whereas a late-onset DR failed in preventing it. Our data show that LTDR was more effective in rescuing inflammaging in liver and kidney, while STDR mitigated aging-associated activation of inflammatory pathways more effectively in blood; in other tissues both LTDR and STDR prevented the pro-inflammatory phenotype to a similar extent.

Transposable elements (TE) make up about 46% of the human genome. They consist in repetitive sequences which are capable to or potentially capable to actively or passively insert copies of themselves elsewhere in the genome. TE are classified in Class I TEs, if they are RNA retrotransposons that require reverse transcriptase activity for transposition, and Class II TEs, or DNA transposons, that require transposase enzyme for their mobilization. LINE (long interspersed nuclear elements) and SINE (short interspersed nuclear elements) are the most studied and abundant class I TEs. The third family of Class I TEs consists of long terminal repeat (LTR) retroelements, known as HERVs (human endogenous retroviruses). HERV are residues of viral infections from the past that have remained in the human genome and occupy about 8% of it.

Bi-directional transcription of hERVs is a common feature of autoimmunity, neurodegeneration, and cancer. Higher rates of cancer incidence, neurodegeneration, and autoimmunity but a lower prevalence of autoimmune diseases characterize elderly people. Although the re-expression of hERVs is commonly observed in different cellular models of senescence as a result of the loss of their epigenetic transcriptional silencing, the hERVs modulation during aging is more complex, with a peak of activation in the sixties and a decline in the nineties. What is clearly accepted, instead, is the impact of the re-activation of dormant hERV on the maintenance of stemness and tissue self-renewing properties.

An innate cellular immunity system, based on the RLR-MAVS circuit, controls the degradation of double-stranded DNAs arising from the transcription of hERV elements, similarly to what happens for the accumulation of cytoplasmic DNA leading to the activation of cGAS/STING pathway. While agonists and inhibitors of the cGAS-STING pathway are considered promising immunomodulatory molecules, the effect of the RLR-MAVS pathway on innate immunity is still largely based on correlations and not on causality. Here we review the most recent evidence regarding the activation of MDA5-RIG1-MAVS pathway as a result of hERV de-repression during aging, immunosenescence, cancer, and autoimmunity. We will also deal with the epigenetic mechanisms controlling hERV repression and with the strategies that can be adopted to modulate hERV expression in a therapeutic perspective. Finally, we will discuss if the RLR-MAVS signalling pathway actively modulates physiological and pathological conditions or if it is passively activated by them.

Nearly a decade ago, researchers showed that a large number of CpG sites in the human genome increase or decrease in methylation fraction over time, such that one can select among these CpG sites to measure the rate at which an individual ages. These so-called "epigenetic clocks" train regularized linear regression models to predict the chronological age of an individual from the methylation values of CpG sites distributed across the genome. During training, the CpG sites for which the methylation fractions are most predictive of chronological age are identified and selected for use in the linear regression equation. The number of CpG sites selected has depended greatly on the particular approach used but is typically between two and a few hundred.

In the time since these epigenetic clocks were introduced, substantial development effort has been invested into improving their predictive accuracy and extending their range of applications. The first randomized clinical trial using an epigenetic clock as the main validator of intervention efficacy was recently conducted. The prediction of epigenetic age has also been made more accessible and efficient; epigenetic clock software packages are readily available, with some requiring methylation values at only a few CpG sites for accurate age predictions. The sophistication of epigenetic clocks today is greater than it was a decade ago because the tools have broader reach, and we fully expect this trend to continue.

While optimization of existing concepts and methods is important, it is also vital that the field keeps moving. Beyond the construction of increasingly accurate chronological clocks, there are many unanswered questions related to the specific mechanisms by which the epigenome influences aging and, reciprocally, by which aging influences the epigenome. Prediction of age was an important first step, but - in our view - the focus must shift from chasing increasingly accurate age computations to understanding the links between the epigenome and the mechanisms and physiological changes of aging.

Aging is a major risk factor for developing neuroinflammation. As it progresses, neuroinflammation can cause neuron death in the brain, particularly in the hippocampus. This brain region is crucial for learning and memory function. Hence, aged humans who experience loss of neurons in this region exhibit frequent tendency of memory loss. Aging and its association for the development of numerous brain diseases are continuously increasing in prevalence. Increased plasma, cerebrospinal fluid (CSF), and brain level of alpha-synuclein (α-syn) and their association to microglial cells activation, pro-inflammatory cytokines production, neurodegeneration, and cognitive deficits have been observed in aged humans. However, the exact mechanism by which such α-syn abnormalities trigger neuroinflammation in aged humans are poorly defined.

Studies have shown that irregular accumulations and distributions of α-syn and/or the development of α-syn-reactive immunoglobulin G (IgG) autoantibodies are linked to the brain production of pro-inflammatory cytokines, i.e., interleukin-1 beta (IL1β), IL-6, and tumor necrosis factor alpha (TNF-α), which lead to neuron death and memory deficits in several age-related neurodegenerative diseases, i.e., Alzheimer's disease (AD), Parkinson's disease (PD), multiple system atrophy (MSA), rapid eye movement sleep behavior disorder (RBD), frontotemporal lobar dementia (PLD), and dementia with Lewy bodies (LBD). Therefore, this current study explored the involvement of α-syn, α-syn-reactive IgG autoantibodies, and Fc gamma receptors (FcγRs) function in aging human nervous system.

Based on the elevated brain expression of α-syn-reactive IgG auto antibodies and the higher expression of activating FcγR in aged humans, this report suggests that the α-syn-reactive IgG auto antibodies and their immunological reaction to α-syn are the basis of the formation of alpha-synuclein-specific IgG immune complexes (α-syn-IgG-ICs) in aged human brains. Furthermore, the strong interaction between such α-syn-IgG-ICs and activation of FcγR fuels the downstream signaling that causes microglial cells and/or neurons activation, pro-inflammatory cytokines production, and the death of neurons in aged humans.

Industrial advances have been associated with large-scale changes in the human gut microbiome and a higher incidence of complex human diseases. Rewilding the human gut microbiome by transplanting the whole gut microbial community from donors in nonindustrial societies may result in a dramatic mismatch between our industrial environment/lifestyles and the ancestral microbiome.

Emerging studies suggest that stool banking and autologous fecal microbiota transplantation (FMT), using the recipients' own stool samples collected at a younger age when they are disease-free, may be a better - or at least an alternative - solution. This leads to the idea of rejuvenating the human gut microbiome. The conceptual similarity between stool banking for autologous FMT and cord blood banking for an autologous transplant implies the potential for rejuvenating the human gut microbiome.

Here we propose rejuvenating the human gut microbiome by stool banking and autologous fecal microbiota transplantation, that is, collecting the hosts' stool samples at a younger age when they are at optimal health, and cryopreserving the samples in a stool bank for the hosts' own future use. In this article we discuss the motivation, applications, feasibility, and challenges of this solution. Basic research in cataloging, characterizing, and even engineering individual microbes (or well-defined consortia of them) and their functions (or metabolic fuels/products) is still a very promising solution to restoring a healthy gut microbiota. However, considering the daunting complexity of the human gut microbiota, both bottom-up mechanistic approaches and top-down systems approaches (based on FMT) will be needed.

The gut microbiota is a critical regulator of human physiology, deleterious changes to its composition and function (dysbiosis) have been linked to the development and progression of cardiovascular diseases. Vascular ageing (VA) is a process of progressive stiffening of the arterial tree associated with arterial wall remodeling, which can precede hypertension and organ damage, and is associated with cardiovascular risk. Arterial stiffness has become the preferred marker of VA.

In our systematic review, we found an association between gut microbiota composition and arterial stiffness, with two patterns, in most animal and human studies: a direct correlation between arterial stiffness and abundances of bacteria associated with altered gut permeability and inflammation; an inverse relationship between arterial stiffness, microbiota diversity, and abundances of bacteria associated with most fit microbiota composition.

Interventional studies were able to show a stable link between microbiota modification and arterial stiffness only in animals. None of the human interventional trials was able to demonstrate this relationship, and very few adjusted the analyses for determinants of arterial stiffness. We observed a lack of large randomized interventional trials in humans that test the role of gut microbiota modifications on arterial stiffness, and take into account blood pressure and hemodynamic alterations.

A new study found that adult survivors of cancer had a 42% greater risk of cardiovascular diseases (CVD) than people without cancer. The authors found that survivors of cancer had a particularly higher risk of developing heart failure (52% higher risk), followed by stroke (22% higher risk). There were no significant differences in the risk of coronary heart disease between those with and without cancer.

The analysis used data from the Atherosclerosis Risk in Communities Study, a prospective community-based population study, initiated in 1987, of CVD and its risk factors. The study had 12,414 participants, with a mean age of 54 who were followed through 2020. Although the study was not designed to pinpoint the causes of increased CVD risk among survivors of cancer, the main hypothesis involves a combination of cancer and noncancer related factors such as inflammation, oxidative stress, cardiac toxicity from specific cancer treatments, and traditional risk factors like hypertension, diabetes, and obesity. While the excess risk of CVD in this group was not fully explained by traditional cardiovascular risk factors such as obesity, high blood pressure and cholesterol levels, and diabetes, it is still very important to address these risk factors that are common in survivors of cancer.

Cardiac toxicity from cancer therapies, or negative cardiac effects of cancer therapies, may be particularly important in increasing the risk of CVD in some survivors of cancer. For example, survivors of breast and blood cancers had significantly higher risk of CVD, and these cancers are typically managed with a combination of chemotherapy and chest radiation that can damage the heart. Conversely, survivors of prostate cancer did not have an increased risk of CVD. These patients can be managed with active surveillance or local therapies without the risk of cardiac toxicity.

Cardiolipin (CL) is a mitochondrial signature phospholipid that plays a pivotal role in mitochondrial dynamics, membrane structure, oxidative phosphorylation, mitochondrial DNA bioenergetics, and mitophagy. The depletion or abnormal acyl composition of CL causes mitochondrial dysfunction, which is implicated in the pathogenesis of aging and age-related disorders. However, the molecular mechanisms by which mitochondrial dysfunction causes age-related diseases remain poorly understood.

Recent development in the field has identified acyl-CoA:lysocardiolipin acyltransferase 1 (ALCAT1), an acyltransferase upregulated by oxidative stress, as a key enzyme that promotes mitochondrial dysfunction in age-related diseases. ALCAT1 catalyzes CL remodeling with very-long-chain polyunsaturated fatty acids, such as docosahexaenoic acid (DHA). Enrichment of DHA renders CL highly sensitive to oxidative damage by reactive oxygen species (ROS). Oxidized CL becomes a new source of ROS in the form of lipid peroxides, leading to a vicious cycle of oxidative stress, CL depletion, and mitochondrial dysfunction. Consequently, ablation or the pharmacological inhibition of ALCAT1 have been shown to mitigate obesity, type 2 diabetes, heart failure, cardiomyopathy, fatty liver diseases, neurodegenerative diseases, and cancer.

The findings suggest that age-related disorders are one disease (aging) manifested by different mitochondrion-sensitive tissues, and therefore should be treated as one disease. This review will discuss a unified hypothesis on CL remodeling by ALCAT1 as the common denominator of mitochondrial dysfunction, linking mitochondrial dysfunction to the development of age-related diseases.

The pig that served as the heart donor came from a population that has been extensively genetically engineered to limit the possibility of rejection by the human immune system. The line was also free of a specific virus that inserts itself into the pig genome (porcine endogenous retrovirus C, or PERV-C) and was raised in conditions that should limit pathogen exposure. The animal was also screened for viruses prior to the transplant, and the patient was screened for pig pathogens afterward.

While patient weight loss was a concern, at five weeks after the transplant, there were no indications of rejection, and the heart was still functioning. Things started to go bad about seven weeks post-transplant when the patient's blood pressure began to drop. Fluid started building on his lungs, and he had to be intubated. Imaging showed that his heart was still clearing out most of the volume of the ventricles with each beat, but the total volume had shrunk as the walls of the ventricle thickened. Eventually, external oxygenation had to be restarted.

Pig DNA began to show up in the bloodstream, indicating tissue damage; some anti-pig-cell antibodies were also detected, suggesting a degree of rejection. But a biopsy failed to find any signs of it in the heart tissue; instead, there were signs that capillaries in the heart were leaking, creating swelling and allowing blood cells into the heart tissue. A week later, a second biopsy indicated that about 40 percent of the heart muscle cells in the transplant were dead or dying, even though there were still no indications of rejection in the tissue. That level of damage brought an end to things and life support was withdrawn.

Aging is known to be associated with hippocampus-dependent memory decline, but the underlying causes of this age-related memory impairment remain yet highly debated. Here we showed that fecal microbiota transplantation (FMT) from aged, but not young, animal donors in young mice is sufficient to trigger profound hippocampal alterations including astrogliosis, decreased adult neurogenesis, decreased novelty-induced neuronal activation and impairment in hippocampus-dependent memory. Furthermore, similar alterations were reported when mice were subjected to an FMT from aged human donors.

To decipher the mechanisms involved in mediating these microbiota-induced effects on brain function, we mapped the vagus nerve (VN)-related neuronal activity patterns and report that aged-mice FM transplanted animals showed a reduction in neuronal activity in the ascending VN output brain structure, whether under basal condition or after VN stimulation. Targeted pharmacogenetic manipulation of VN-ascending neurons demonstrated that the decrease in vagal activity is detrimental to hippocampal functions. In contrast, increasing vagal ascending activity alleviated the adverse effects of aged mice FMT on hippocampal functions, and had a detrimental effect on memory in aged mice. Thus, pharmacogenetic VN stimulation is a potential therapeutic strategy to lessen microbiota-dependent age-associated impairments in hippocampal functions.

Lento Bio, Inc., a preclinical pharmaceutical company focused on developing small molecule therapeutics to target molecular damage driving age-related disease, announced its launch today. The company will initially focus on developing pharmaceutical eyedrops to treat a common vision disorder, presbyopia, or age-related farsightedness. Lento Bio will be supported and incubated by Ichor Life Sciences, a pre-clinical contract research organization, at Clarkson University's Peyton Hall Biotechnology Incubator.

Presbyopia is caused by stiffening of the eye lens, which stems from molecular crosslinks that include advanced glycation end products (AGE) that cause tissue rigidity. The small molecule drugs being developed by Lento Bio will target underlying molecular damage accumulation with the goal of reversing the process of tissue-stiffening in the ocular lens. Upon successful completion of its first project, Lento Bio plans to apply its anti-glycation products more widely to include systemic diseases of aging.

"Lento Bio is starting from a solid foundation of established research into molecular aging damage and will focus development efforts towards the most accessible and relevant disease indications. Through bringing the problem to the science we aim to accelerate the creation of clinical assets and validate our disease hypothesis. We look forward towards collaborating with the scientific teams at Ichor and Clarkson University to pursue research and development of small molecule drugs."

With Vadim Gladyshev serving as chairman and Steve Horvath as vice-chairman, the conference set the stage for the field, paving the way for the development of interventions to delay and reverse aging. Both are world-renowned researchers, and spoke and led the discussions at the conference. The conference was attended by a number of prominent researchers from renowned institutions; such as Cynthia Kenyon of Calico Labs, who discussed about interventions that slow aging, Morten Scheibye-Knudsen of the University of Copenhagen, who talked about modulating DNA repair for healthy aging, and Emma Teeling of the University College Dublin, who spoke about the genetic basis of exceptional longevity of bats.

Day one was about "Delaying Age," and was led by Steve Horvath as the discussion leader. On this day, Cynthia Kenyon, Richard Miller of the University of Michigan and Inigo Martincorena of the Sanger Institute presented. Richard and Inigo presented on drugs and mutations that slow aging in mice, and somatic mutations and clonal expansions in aging, respectively. Day two was all about "Epigenetic Reprogramming and Rejuvenation." It was led by Joe Betts-LaCroix of Retro Biosciences. Manuel Serrano of IRB Barcelona started the day with a talk on understanding and manipulating in vivo reprogramming and its effects on aging. He was followed by Vittorio Sebastiano of Stanford University, who spoke about transient reprogramming for multifaceted reversal of aging. Jacob Kimmel of NewLimit Research followed Vittorio with a talk on reprogramming strategies to restore youthful gene expression. Then came Morgan Levine of Yale University, who discussed DNA methylation landscapes in aging and reprogramming.

The first discussion topic for day three was "Epigenetic Biomarkers," with Kristen Fortney of Bioage leading the discussions. First to the podium was Nick Schaum of Astera Institute, whose discussion topic was "rejuvenome: toward a functional and multiomics understanding of aging and rejuvenation". He was followed by Riccardo Marioni of University of Edinburgh and Ake Lu of San Diego Institute of Science, who discussed about epigenetic clocks and universal DNA methylating age, respectively. "Artificial Intelligence and Machine Learning" was the first subject matter for day four, which was moderated by Marc Kirschner of Harvard. Sergiy Libert of Calico started the day with a talk on construction and analysis of the physiology clock for human aging. I took to the podium next and discussed applications of deep aging clocks in clinical practice and drug discovery. I was followed by Kristen Fortney of Bioage and Albert-laszlo Barabasi of Northeastern University, who discussed data-informed drug discovery for aging and the dark matter of nutrition, respectively.

Over the course of the five-day event, presentations covered many topics, like delaying aging, aging clocks, longevity intervention, and so much more. Many organizations like MIT, Stanford, and Yale were represented. It was truly a great opportunity to network with peers. With this successful conference on aging, the GRC has now plans the second Systems Aging meeting in 2024.

Super-enhancers regulate genes with important functions in processes that are cell type-specific or define cell identity. Mouse embryonic fibroblasts establish 40 senescence-associated super-enhancers regardless of how they become senescent, with 50 activated genes located in the vicinity of these enhancers. Here we show, through gene knockdown and analysis of three core biological properties of senescent cells that a relatively large number of senescence-associated super-enhancer-regulated genes promote survival of senescent mouse embryonic fibroblasts.

Of these, Mdm2, Rnase4, and Ang act by suppressing p53-mediated apoptosis through various mechanisms that are also engaged in response to DNA damage. MDM2 and RNASE4 transcription is also elevated in human senescent fibroblasts to restrain p53 and promote survival. These findings further support the idea that senescent cells actively combat apoptosis on multiple fronts and therefore have numerous therapeutically exploitable vulnerabilities for elimination of detrimental senescent cells implicated in aging and aging-related diseases. These insights provide molecular entry points for the development of targeted therapeutics that eliminate senescent cells at sites of pathology.

When a healthy human cell divides to form two identical cells, a small piece of DNA is shaved off each chromosome's tip, so that telomeres become gradually shorter with each division. However, it remains unclear whether over a person's lifetime, a cell may divide so often that its telomeres erode completely, prompting transition to a senescent state. Researchers have known for decades that telomere shortening triggers senescence in lab-grown cells, but they could only hypothesize that DNA damage at telomeres could make cells senescent.

Until now, testing this hypothesis had not been possible because the tools used to damage DNA were non-specific, causing lesions across the whole chromosome. A new tool uses a special protein that binds exclusively to telomeres. This protein acts like a catcher's mitt, grabbing hold of light-sensitive dye "baseballs" that researchers tossed into the cell. When activated with light, the dye produces DNA-damaging reactive oxygen molecules. Because the dye-catching protein binds only to telomeres, the tool creates DNA lesions specifically at chromosome tips.

Using human cells grown in a dish, the researchers found that damage at telomeres sent the cells into a senescent state after just four days - much faster than the weeks or months of repeated cell divisions that it takes to induce senescence by telomere shortening in the lab. "We found a new mechanism for inducing senescent cells that is completely dependent on telomeres. These findings also solve the puzzle of why dysfunctional telomeres are not always shorter than functional ones. Now that we understand this mechanism, we can start to test interventions to prevent senescence. For example, maybe there are ways to target antioxidants to the telomeres to protect them from oxidative damage."

Researchers coined the term "COPD-associated secretory phenotype" (CASP) to refer to the inflammatory mediators that are increased in COPD and provided a comparison of CASP and senescence-associated secretory phenotype (SASP) factors. In summary, there is a large degree of overlap, supporting the notion that they are strongly linked and reinforces the theory that senescence, along with SASP, is a major contributor to the inflammation that defines COPD.

Typically, cells undergoing senescence chemoattract immune cells, resulting in clearance of these senescent cells by immune cells such as NK cells and macrophages. However, senescent cells in diseased tissues can also impede innate and adaptive immune responses. Senescent cells accumulate in tissues during aging and could influence several pathological features observed in COPD, such as inflammation-associated tissue damage and remodeling. It is difficult to determine whether inflammation observed in COPD is primarily due to senescence, as many other contributing factors within the disease may contribute. However, the presence of enhanced senescent cell frequency in the lungs does contribute to a modified immune response that may influence several aspects of COPD pathogenesis.

There is increasing interest in the resolution of abundant senescence as a potential therapeutic approach in COPD. Senolytic agents, compounds that facilitate the elimination of senescent cells, have received considerable attention lately as a potential treatment for COPD. However, the investigation of these agents is limited by the lack of universal markers of senescence. A better understanding of pathways that induce and reinforce senescence in COPD may allow us to discover possible biomarkers that could serve as targets for these senolytic therapies.

Overall, there is mounting evidence to suggest that senescence could contribute to cells being resistant to apoptosis, exhibiting elevated inflammation, and reduced dead cell clearance, resulting in extensive tissue remodeling observed in COPD. Targeting senescent cells using senolytics to selectively remove senescent cells or modulate SASP using small molecules or antibodies represents a novel approach to countering COPD progression. Several treatments that may target cellular senescence are in development.