A longer and healthier life with TOR down-regulation: genetics and drugs

Rapamycin's lifespan effect is modulated by mito-nuclear epistasis in Drosophila

The macrolide drug rapamycin is a benchmark anti-ageing drug, which robustly extends lifespan of diverse organisms. For any health intervention, it is paramount to establish whether benefits are distributed equitably among individuals and populations, and ideally to match intervention to recipients' needs. However, how responses to rapamycin vary is surprisingly understudied. Here we investigate how among-population variation in both mitochondrial and nuclear genetics shapes rapamycin's effects on lifespan. We show that epistatic "mito-nuclear" interactions, between mitochondria and nuclei, modulate the response to rapamycin treatment. Differences manifest as differential demographic effects of rapamycin, with altered age-specific mortality rate. However, a fitness cost of rapamycin early in life does not show a correlated response, suggesting that mito-nuclear epistasis can decouple costs and benefits of treatment. These findings suggest that a deeper understanding of how variation in mitochondrial and nuclear genomes shapes physiology may facilitate tailoring of anti-ageing therapy to individual need.

An expedited screening platform for the discovery of anti-ageing compounds in vitro and in vivo

BACKGROUND

Restraining or slowing ageing hallmarks at the cellular level have been proposed as a route to increased organismal lifespan and healthspan. Consequently, there is great interest in anti-ageing drug discovery. However, this currently requires laborious and lengthy longevity analysis. Here, we present a novel screening readout for the expedited discovery of compounds that restrain ageing of cell populations in vitro and enable extension of in vivo lifespan.

METHODS

Using Illumina methylation arrays, we monitored DNA methylation changes accompanying long-term passaging of adult primary human cells in culture. This enabled us to develop, test, and validate the CellPopAge Clock, an epigenetic clock with underlying algorithm, unique among existing epigenetic clocks for its design to detect anti-ageing compounds in vitro. Additionally, we measured markers of senescence and performed longevity experiments in vivo in Drosophila, to further validate our approach to discover novel anti-ageing compounds. Finally, we bench mark our epigenetic clock with other available epigenetic clocks to consolidate its usefulness and specialisation for primary cells in culture.

RESULTS

We developed a novel epigenetic clock, the CellPopAge Clock, to accurately monitor the age of a population of adult human primary cells. We find that the CellPopAge Clock can detect decelerated passage-based ageing of human primary cells treated with rapamycin or trametinib, well-established longevity drugs. We then utilise the CellPopAge Clock as a screening tool for the identification of compounds which decelerate ageing of cell populations, uncovering novel anti-ageing drugs, torin2 and dactolisib (BEZ-235). We demonstrate that delayed epigenetic ageing in human primary cells treated with anti-ageing compounds is accompanied by a reduction in senescence and ageing biomarkers. Finally, we extend our screening platform in vivo by taking advantage of a specially formulated holidic medium for increased drug bioavailability in Drosophila. We show that the novel anti-ageing drugs, torin2 and dactolisib (BEZ-235), increase longevity in vivo.

CONCLUSIONS

Our method expands the scope of CpG methylation profiling to accurately and rapidly detecting anti-ageing potential of drugs using human cells in vitro, and in vivo, providing a novel accelerated discovery platform to test sought after anti-ageing compounds and geroprotectors.

A ginseng-derived rhamnogalacturonan I (RG-I) pectin promotes longevity via TOR signalling in Caenorhabditis elegans

Panax ginseng C. A. Meyer (ginseng), a traditional Chinese herb, is usually used to improve health and increase anti-aging activity for human. Polysaccharides are bioactive components of ginseng. Herein, using Caenorhabditis elegans as a model, we discovered a ginseng-derived rhamnogalacturonan I (RG-I) pectin WGPA-1-RG promoted longevity via TOR signalling pathway with transcription factors FOXO/DAF-16 and Nrf2/SKN-1 accumulated in the nucleus, where they activated target genes. And the WGPA-1-RG-mediated lifespan extension was dependent on endocytosis, rather than a bacterial metabolic process. Glycosidic linkage analyses combined with arabinose- and galactose-releasing enzyme hydrolyses identified the RG-I backbone of WGPA-1-RG was primarily substituted with α-1,5-linked arabinan, β-1,4-linked galactan and arabinogalactan II (AG-II) side chains. Feeding worms with the WGPA-1-RG-derived fractions which lost distinct structural elements by enzymatic digestions, we found the arabinan side chains prominently contributed to the longevity-promoting activity of WGPA-1-RG. These findings provide a novel ginseng-derived nutrient that potentially increases human longevity.

Integrated Multi-Omics for Novel Aging Biomarkers and Antiaging Targets

Aging is closely related to the occurrence of human diseases; however, its exact biological mechanism is unclear. Advancements in high-throughput technology provide new opportunities for omics research to understand the pathological process of various complex human diseases. However, single-omics technologies only provide limited insights into the biological mechanisms of diseases. DNA, RNA, protein, metabolites, and microorganisms usually play complementary roles and perform certain biological functions together. In this review, we summarize multi-omics methods based on the most relevant biomarkers in single-omics to better understand molecular functions and disease causes. The integration of multi-omics technologies can systematically reveal the interactions among aging molecules from a multidimensional perspective. Our review provides new insights regarding the discovery of aging biomarkers, mechanism of aging, and identification of novel antiaging targets. Overall, data from genomics, transcriptomics, proteomics, metabolomics, integromics, microbiomics, and systems biology contribute to the identification of new candidate biomarkers for aging and novel targets for antiaging interventions.

Cellular senescence-an aging hallmark in chronic obstructive pulmonary disease pathogenesis

Chronic obstructive pulmonary disease (COPD),¹ a representative aging-related pulmonary disorder, is mainly caused by cigarette smoke (CS) exposure. Age is one of the most important risk factors for COPD development, and increased cellular senescence in tissues and organs is a component of aging. CS exposure can induce cellular senescence, as characterized by irreversible growth arrest and aberrant cytokine secretion of the senescence-associated secretory phenotype; thus, accumulation of senescent cells is widely implicated in COPD pathogenesis. CS-induced oxidative modifications to cellular components may be causally linked to accelerated cellular senescence, especially during accumulation of damaged macromolecules. Autophagy is a conserved mechanism whereby cytoplasmic components are sent for lysosomal degradation to maintain proteostasis. Autophagy diminishes with age, and loss of proteostasis is one of the hallmarks of aging. We have reported the involvement of insufficient autophagy in regulating CS-induced cellular senescence with respect to COPD pathogenesis. However, the role of autophagy in COPD pathogenesis can vary based on levels of cell stress and type of selective autophagy because excessive activation of autophagy can be responsible for inducing regulated cell death. Senotherapies targeting cellular senescence may be effective COPD treatments. Autophagy activation could be a promising sonotherapeutic approach, but the optimal modality of autophagy activation should be examined in future studies.

The Regulating Effect of Autophagy-Related MiRNAs in Kidney, Bladder, and Prostate Cancer

Autophagy is a treatment target for many disorders, including cancer, and its specific role is becoming increasingly well known. In tumors, researchers pay attention to microribonucleic acids (miRNAs) with regulatory effects to develop more effective therapeutic drugs for autophagy and find new therapeutic targets. Various studies have shown that autophagy-related miRNAs play an irreplaceable role in different tumors, such as miR-495, miR-30, and miR-101. These miRNAs are associated with autophagy resistance in gastric cancer, non-small cell lung cancer, and cervical cancer. In recent years, autophagy-related miRNAs have also been reported to play a role in autophagy in urinary system tumors. This article reviews the regulatory effects of autophagy-related miRNAs in kidney, bladder, and prostate cancer and provides new ideas for targeted therapy of the three major tumors of the urinary system.

Rapamycin Treatment of Tendon Stem/Progenitor Cells Reduces Cellular Senescence by Upregulating Autophagy

The elderly population is prone to tendinopathy due to aging-related tendon changes such as cellular senescence and a decreased ability to modulate inflammation. Aging can render tendon stem/progenitor cells (TSCs) into premature senescence. We investigated the effects of rapamycin, a specific mTOR inhibitor, on the senescence of TSCs. We first showed that after treatment with bleomycin in vitro, rat patellar TSCs (PTSCs) underwent senescence, characterized by morphological alterations, induction of senescence-associated β-galactosidase (SA-β-gal) activity, and an increase in p53, p21, and p62 protein expression. Senescence of PTSCs was also characterized by the elevated expression of MMP-13 and TNF-α genes, both of which are molecular hallmarks of chronic tendinopathy. We then showed that rapamycin treatment was able to reverse the above senescent phenotypes and increase autophagy in the senescent PTSCs. The activation of autophagy and senescence rescue was, at least partly, due to the translocation of HMGB1 from the nucleus to the cytosol that functions as an autophagy promoter. By reducing TSC senescence, rapamycin may be used as a therapeutic to inhibit tendinopathy development in the aging population by promoting autophagy.

Novel target for treating Alzheimer's Diseases: Crosstalk between the Nrf2 pathway and autophagy

In mammals, the Keap1-Nrf2-ARE pathway (henceforth, "the Nrf2 pathway") and autophagy are major intracellular defence systems that combat oxidative damage and maintain homeostasis. p62/SQSTM1, a ubiquitin-binding autophagy receptor protein, links the Nrf2 pathway and autophagy. Phosphorylation of p62 dramatically enhances its affinity for Keap1, which induces Keap1 to release Nrf2, and the p62-Keap1 heterodimer recruits LC3 and mediates the permanent degradation of Keap1 in the selective autophagy pathway. Eventually, Nrf2 accumulates in the cytoplasm and then translocates into the nucleus to activate the transcription of downstream genes that encode antioxidant enzymes, which protect cells from oxidative damage. Since Nrf2 also upregulates the expression of the p62 gene, a p62-Keap1-Nrf2 positive feedback loop is created that further enhances the protective effect on cells. Studies have shown that the p62-activated noncanonical Nrf2 pathway is an important marker of neurodegenerative diseases. The p62-Keap1-Nrf2 positive feedback loop and the Nrf2 pathway are involved in eliminating the ROS and protein aggregates induced by AD. Therefore, maintaining the homeostasis of the p62-Keap1-Nrf2 positive feedback loop, which is a bridge between the Nrf2 pathway and autophagy, may be a potential target for the treatment of AD.

Dietary nitrite extends lifespan and prevents age-related locomotor decline in the fruit fly

Aging is associated with decreased nitric oxide (NO) bioavailability and signalling. Boosting of a dietary nitrate-nitrite-NO pathway e.g. by ingestion of leafy green vegetables, improves cardiometabolic function, mitochondrial efficiency and reduces oxidative stress in humans and rodents, making dietary nitrate and nitrite an appealing intervention to address age-related disorders. On the other hand, these anions have long been implicated in detrimental health effects of our diet, particularly in formation of carcinogenic nitrosamines. The aim of this study was to assess whether inorganic nitrite affects lifespan in Drosophila melanogaster and investigate possible mechanisms underlying any such effect. In a survival assay, female flies fed a nitrite supplemented diet showed lifespan extension by 9 and 15% with 0.1 and 1 μM nitrite respectively, with no impact of nitrite on reproductive output. Interestingly, nitrite could also protect female flies from age-dependent locomotor decline, indicating a protective effect on healthspan. NO generation from nitrite involved Drosophila commensal bacteria and was indicated by a fluorescent probe as well as direct measurements of NO gas formation with chemiluminescence. Nutrient sensing pathways such as TOR and sirtuins, have been strongly implicated in lifespan extension. In aged flies, nitrite supplementation significantly downregulated dTOR and upregulated dSir2 gene expression. Total triglycerides and glucose were decreased, a described downstream effect of both TOR and sirtuin pathways. In conclusion, we demonstrate that very low doses of dietary nitrite extend lifespan and favour healthspan in female flies. We propose modulation of nutrient sensing pathways as driving mechanisms for such effects.

Fine-tuning autophagy maximises lifespan and is associated with changes in mitochondrial gene expression in Drosophila

Increased cellular degradation by autophagy is a feature of many interventions that delay ageing. We report here that increased autophagy is necessary for reduced insulin-like signalling (IIS) to extend lifespan in Drosophila and is sufficient on its own to increase lifespan. We first established that the well-characterised lifespan extension associated with deletion of the insulin receptor substrate chico was completely abrogated by downregulation of the essential autophagy gene Atg5. We next directly induced autophagy by over-expressing the major autophagy kinase Atg1 and found that a mild increase in autophagy extended lifespan. Interestingly, strong Atg1 up-regulation was detrimental to lifespan. Transcriptomic and metabolomic approaches identified specific signatures mediated by varying levels of autophagy in flies. Transcriptional upregulation of mitochondrial-related genes was the signature most specifically associated with mild Atg1 upregulation and extended lifespan, whereas short-lived flies, possessing strong Atg1 overexpression, showed reduced mitochondrial metabolism and up-regulated immune system pathways. Increased proteasomal activity and reduced triacylglycerol levels were features shared by both moderate and high Atg1 overexpression conditions. These contrasting effects of autophagy on ageing and differential metabolic profiles highlight the importance of fine-tuning autophagy levels to achieve optimal healthspan and disease prevention.

Cellular parabiosis and the latency of age-related diseases

Cellular parabiosis is tissue-based phenotypic suppression of cellular dysfunction by intercellular molecular traffic keeping initiated age-related diseases and conditions in long latency. Interruption of cellular parabiosis (e.g. by chronic inflammation) promotes the onset of initiated pathologies.

The stability of initiated latent cancers and other age-related diseases (ARD) hints to phenotypically silent genome alterations. I propose that latency in the onset of ageing and ARD is largely due to phenotypic suppression of cellular dysfunctions via molecular traffic among neighbouring cells. Intercellular trafficking ranges from the transfer of ions and metabolites (via gap junctions) to entire organelles (via tunnelling nanotubes). Any mechanism of cell-to-cell communication resulting in functional cross-complementation among the cells is called cellular parabiosis. Such ‘cellular solidarity’ creates tissue homeostasis by buffering defects and averaging cellular functions within the tissues. Chronic inflammation is known to (i) interrupt cellular parabiosis by the activity of extracellular proteases, (ii) activate dormant pathologies and (iii) shorten disease latency, as in tumour promotion and inflammaging. Variation in cellular parabiosis and protein oxidation can account for interspecies correlations between body mass, ARD latency and longevity. Now, prevention of ARD onset by phenotypic suppression, and healing by phenotypic reversion, become conceivable.

The GATA Transcription Factor Gaf1 Represses tRNAs, Inhibits Growth, and Extends Chronological Lifespan Downstream of Fission Yeast TORC1

Target of Rapamycin Complex 1 (TORC1) signaling promotes growth and aging. Inhibition of TORC1 leads to reduced protein translation, which promotes longevity. TORC1-dependent post-transcriptional regulation of protein translation has been well studied, while analogous transcriptional regulation is less understood. Here we screen fission yeast mutants for resistance to Torin1, which inhibits TORC1 and cell growth. Cells lacking the GATA factor Gaf1 (gaf1Δ) grow normally even in high doses of Torin1. The gaf1Δ mutation shortens the chronological lifespan of non-dividing cells and diminishes Torin1-mediated longevity. Expression profiling and genome-wide binding experiments show that upon TORC1 inhibition, Gaf1 directly upregulates genes for small-molecule metabolic pathways and indirectly represses genes for protein translation. Surprisingly, Gaf1 binds to and downregulates the tRNA genes, so it also functions as a transcription factor for RNA polymerase III. Thus, Gaf1 controls the transcription of both protein-coding and tRNA genes to inhibit translation and growth downstream of TORC1.

Agephagy - Adapting Autophagy for Health During Aging

Autophagy is a major cellular recycling process that delivers cellular material and entire organelles to lysosomes for degradation, in a selective or non-selective manner. This process is essential for the maintenance of cellular energy levels, components, and metabolites, as well as the elimination of cellular molecular damage, thereby playing an important role in numerous cellular activities. An important function of autophagy is to enable survival under starvation conditions and other stresses. The majority of factors implicated in aging are modifiable through the process of autophagy, including the accumulation of oxidative damage and loss of proteostasis, genomic instability and epigenetic alteration. These primary causes of damage could lead to mitochondrial dysfunction, deregulation of nutrient sensing pathways and cellular senescence, finally causing a variety of aging phenotypes. Remarkably, advances in the biology of aging have revealed that aging is a malleable process: a mild decrease in signaling through nutrient-sensing pathways can improve health and extend lifespan in all model organisms tested. Consequently, autophagy is implicated in both aging and age-related disease. Enhancement of the autophagy process is a common characteristic of all principal, evolutionary conserved anti-aging interventions, including dietary restriction, as well as inhibition of target of rapamycin (TOR) and insulin/IGF-1 signaling (IIS). As an emerging and critical process in aging, this review will highlight how autophagy can be modulated for health improvement.

Rapamycin as a potential treatment for succinate dehydrogenase deficiency

Drosophila melanogaster is a powerful model to study mitochondrial respiratory chain defects, particularly succinate dehydrogenase (SDH) deficiency. Mutations in sdh genes cause degenerative disorders and often lead to death. Therapies for such pathologies are based on a combination of vitamins and dietary supplements, and are rarely effective. In Drosophila, mutations in several of the genes encoding SDH resemble the pathology of SDH deficiency in humans, enabling the Drosophila model to be used in finding treatments for this condition. Here we show that exposure to the drug rapamycin improves the survival of sdh mutant strains, the activity of SDH and the impaired climbing associated with sdh mutations. However, the production of reactive oxygen species, the oxygen consumption of isolated mitochondria and the resistance to hyperoxia were minimally affected. Our results contribute to the current research seeking a treatment for mitochondrial disease.

Pulmonary Diseases and Ageing

Chronic obstructive pulmonary disease (COPD) and idiopathic pulmonary fibrosis are regarded as a diseases of accelerated lung ageing and show all of the hallmarks of ageing, including telomere shortening, cellular senescence, activation of PI3 kinase-mTOR signaling, impaired autophagy, mitochondrial dysfunction, stem cell exhaustion, epigenetic changes, abnormal microRNA profiles, immunosenescence and a low grade chronic inflammation due to senescence-associated secretory phenotype (SASP). Many of these ageing mechanisms are driven by exogenous and endogenous oxidative stress. There is also a reduction in anti-ageing molecules, such as sirtuins and Klotho, which further accelerate the ageing process. Understanding these molecular mechanisms has identified several novel therapeutic targets and several drugs and dietary interventions are now in development to treat chronic lung disease.

Mitochondrial regulation of cardiac aging

Aging is associated with progressive decline in cardiac structure and function. Accumulating evidence in model organisms and humans links cardiac aging to mitochondrial regulation, encompassing a complex interplay of mitochondrial morphology, mitochondrial ROS, mitochondrial DNA mutations, mitochondrial unfolded protein response, nicotinamide adenine dinucleotide levels and sirtuins, as well as mitophagy. This review summarizes the recent discoveries on the mitochondrial regulation of cardiac aging and the possible molecular mechanisms underlying the anti-aging effects, as well as the potential interventions that alleviate aging-related cardiac diseases and attenuate cardiac aging via the regulation of mitochondria.

Autophagy in Age-Associated Neurodegeneration

The elimination of abnormal and dysfunctional cellular constituents is an essential prerequisite for nerve cells to maintain their homeostasis and proper function. This is mainly achieved through autophagy, a process that eliminates abnormal and dysfunctional cellular components, including misfolded proteins and damaged organelles. Several studies suggest that age-related decline of autophagy impedes neuronal homeostasis and, subsequently, leads to the progression of neurodegenerative disorders due to the accumulation of toxic protein aggregates in neurons. Here, we discuss the involvement of autophagy perturbation in neurodegeneration and present evidence indicating that upregulation of autophagy holds potential for the development of therapeutic interventions towards confronting neurodegenerative diseases in humans.

Evidence that hematopoietic stem cell function is preserved during aging in long-lived S6K1 mutant mice

The mechanistic target of rapamycin (mTOR) signalling pathway plays a highly conserved role in aging; mice lacking ribosomal protein S6 kinase 1 (S6K1^−/−) have extended lifespan and healthspan relative to wild type (WT) controls. Exactly how reduced mTOR signalling induces such effects is unclear, although preservation of stem cell function may be important. We show, using gene expression analyses, that there was a reduction in expression of cell cycle genes in young (12 week) and aged (80 week) S6K1^−/− BM-derived c-Kit⁺ cells when compared to age-matched WT mice, suggesting that these cells are more quiescent in S6K1^−/− mice. In addition, we investigated hematopoietic stem cell (HSC) frequency and function in young and aged S6K1^−/− and WT mice. Young, but not aged, S6K1^−/− mice had more LSK (lineage⁻, c-Kit⁺, Sca-1⁺) cells (% of bone marrow (BM)), including the most primitive long-term repopulating HSCs (LT-HSC) relative to WT controls. Donor-derived engraftment of LT-HSCs in recipient mice was unaffected by genotype in young mice, but was enhanced in transplants using LT-HSCs derived from aged S6K1^−/− mice. Our results are the first to provide evidence that age-associated HSC functional decline is ameliorated in a long-lived mTOR mutant mouse.

The TOR Signaling Pathway in Spatial and Temporal Control of Cell Size and Growth

Cell size is amenable by genetic and environmental factors. The highly conserved nutrient-responsive Target of Rapamycin (TOR) signaling pathway regulates cellular metabolic status and growth in response to numerous inputs. Timing and duration of TOR pathway activity is pivotal for both cell mass built up as well as cell cycle progression and is controlled and fine-tuned by the abundance and quality of nutrients, hormonal signals, growth factors, stress, and oxygen. TOR kinases function within two functionally and structurally discrete multiprotein complexes, TORC1 and TORC2, that are implicated in temporal and spatial control of cell size and growth respectively; however, recent data indicate that such functional distinctions are much more complex. Here, we briefly review roles of the two complexes in cellular growth and cytoarchitecture in various experimental model systems.

[Anti-ageing therapies in Alzheimer's disease]

Alzheimer's disease is the most common cause of dementia in the elderly population. Currently, there are no effective treatments to prevent or delay the natural course of the disease. Numerous studies have provided information about the molecular processes underlying biological ageing and, perhaps more importantly, potential interventions to slow ageing and promote healthy longevity in laboratory model systems. The main issue addressed in this review is whether an intervention that has anti-ageing properties can alter the appearance and/or progression of Alzheimer's disease, a disease in which age is the biggest risk factor. Different anti-ageing interventions have been shown to prevent (and in some cases possibly restore) several parameters recognised as central symptoms to the development of Alzheimer's disease. In addition, they are taking the first steps towards translating these laboratory discoveries into clinical applications.

Meat and Nicotinamide: A Causal Role in Human Evolution, History, and Demographics

Hunting for meat was a critical step in all animal and human evolution. A key brain-trophic element in meat is vitamin B3 / nicotinamide. The supply of meat and nicotinamide steadily increased from the Cambrian origin of animal predators ratcheting ever larger brains. This culminated in the 3-million-year evolution of Homo sapiens and our overall demographic success. We view human evolution, recent history, and agricultural and demographic transitions in the light of meat and nicotinamide intake. A biochemical and immunological switch is highlighted that affects fertility in the 'de novo' tryptophan-to-kynurenine-nicotinamide 'immune tolerance' pathway. Longevity relates to nicotinamide adenine dinucleotide consumer pathways. High meat intake correlates with moderate fertility, high intelligence, good health, and longevity with consequent population stability, whereas low meat/high cereal intake (short of starvation) correlates with high fertility, disease, and population booms and busts. Too high a meat intake and fertility falls below replacement levels. Reducing variances in meat consumption might help stabilise population growth and improve human capital.

Senescence in COPD and Its Comorbidities

Chronic obstructive pulmonary disease (COPD) is regarded as a disease of accelerated lung aging. This affliction shows all of the hallmarks of aging, including telomere shortening, cellular senescence, activation of PI3 kinase-mTOR signaling, impaired autophagy, mitochondrial dysfunction, stem cell exhaustion, epigenetic changes, abnormal microRNA profiles, immunosenescence, and a low-grade chronic inflammation (inflammaging). Many of these pathways are driven by chronic exogenous and endogenous oxidative stress. There is also a reduction in antiaging molecules, such as sirtuins and Klotho, which further accelerate the aging process. COPD is associated with several comorbidities (multimorbidity), such as cardiovascular and metabolic diseases, that share the same pathways of accelerated aging. Understanding these mechanisms has helped identify several novel therapeutic targets, and several drugs and dietary interventions are now in development to treat multimorbidity.

Frameworks for Proof-of-Concept Clinical Trials of Interventions That Target Fundamental Aging Processes

Therapies targeted at fundamental processes of aging may hold great promise for enhancing the health of a wide population by delaying or preventing a range of age-related diseases and conditions—a concept dubbed the “geroscience hypothesis.” Early, proof-of-concept clinical trials will be a key step in the translation of therapies emerging from model organism and preclinical studies into clinical practice. This article summarizes the outcomes of an international meeting partly funded through the NIH R24 Geroscience Network, whose purpose was to generate concepts and frameworks for early, proof-of-concept clinical trials for therapeutic interventions that target fundamental processes of aging. The goals of proof-of-concept trials include generating preliminary signals of efficacy in an aging-related disease or outcome that will reduce the risk of conducting larger trials, contributing data and biological samples to support larger-scale research by strategic networks, and furthering a dialogue with regulatory agencies on appropriate registration indications. We describe three frameworks for proof-of-concept trials that target age-related chronic diseases, geriatric syndromes, or resilience to stressors. We propose strategic infrastructure and shared resources that could accelerate development of therapies that target fundamental aging processes.

All-trans retinoic acid and rapamycin normalize Hutchinson Gilford progeria fibroblast phenotype

Hutchinson Gilford progeria syndrome is a fatal disorder characterized by accelerated aging, bone resorption and atherosclerosis, caused by a LMNA mutation which produces progerin, a mutant lamin A precursor. Progeria cells display progerin and prelamin A nuclear accumulation, altered histone methylation pattern, heterochromatin loss, increased DNA damage and cell cycle alterations. Since the LMNA promoter contains a retinoic acid responsive element, we investigated if all-trans retinoic acid administration could lower progerin levels in cultured fibroblasts. We also evaluated the effect of associating rapamycin, which induces autophagic degradation of progerin and prelamin A. We demonstrate that all-trans retinoic acid acts synergistically with low-dosage rapamycin reducing progerin and prelamin A, via transcriptional downregulation associated with protein degradation, and increasing the lamin A to progerin ratio. These effects rescue cell dynamics and cellular proliferation through recovery of DNA damage response factor PARP1 and chromatin-associated nuclear envelope proteins LAP2α and BAF. The combined all-trans retinoic acid-rapamycin treatment is dramatically efficient, highly reproducible, represents a promising new approach in Hutchinson-Gilford Progeria therapy and deserves investigation in ageing-associated disorders.

Target of rapamycin activation predicts lifespan in fruit flies

Aging and age-related diseases are one of the most important health issues that the world will confront during the 21^st century. Only by understanding the proximal causes will we be able to find treatments to reduce or delay the onset of degenerative diseases associated with aging. Currently, the prevalent paradigm in the field is the accumulation of damage. However, a new theory that proposes an alternative explanation is gaining momentum. The hyperfunction theory proposes that aging is not a consequence of a wear and tear process, but a result of the continuation of developmental programs during adulthood. Here we use Drosophila melanogaster, where evidence supporting both paradigms has been reported, to identify which parameters that have been previously related with lifespan best predict the rate of aging in wild type flies cultured at different temperatures. We find that mitochondrial function and mitochondrial reactive oxygen species (mtROS) generation correlates with metabolic rate, but not with the rate of aging. Importantly, we find that activation of nutrient sensing pathways (i.e. insulin-PI3K/Target of rapamycin (Tor) pathway) correlates with lifespan, but not with metabolic rate. Our results, dissociate metabolic rate and lifespan in wild type flies and instead link nutrient sensing signaling with longevity as predicted by the hyperfunction theory.

Dual mTORC1/C2 inhibitors suppress cellular geroconversion (a senescence program)

In proliferating cells, mTOR is active and promotes cell growth. When the cell cycle is arrested, then mTOR converts reversible arrest to senescence (geroconversion). Rapamycin and other rapalogs suppress geroconversion, maintaining quiescence instead. Here we showed that ATP-competitive kinase inhibitors (Torin1 and PP242), which inhibit both mTORC1 and TORC2, also suppressed geroconversion. Despite inhibition of proliferation (in proliferating cells), mTOR inhibitors preserved re-proliferative potential (RP) in arrested cells. In p21-arrested cells, Torin 1 and PP242 detectably suppressed geroconversion at concentrations as low as 1-3 nM and 10-30 nM, reaching maximal gerosuppression at 30 nM and 300 nM, respectively. Near-maximal gerosuppression coincided with inhibition of p-S6K(T389) and p-S6(S235/236). Dual mTOR inhibitors prevented senescent morphology and hypertrophy. Our study warrants investigation into whether low doses of dual mTOR inhibitors will prolong animal life span and delay age-related diseases. A new class of potential anti-aging drugs can be envisioned.

Rejuvenating immunity: "anti-aging drug today" eight years later

The 2014 year ended with celebration: Everolimus, a rapamycin analog, was shown to improve immunity in old humans, heralding ‘a turning point’ in research and new era in human quest for immortality. Yet, this turning point was predicted a decade ago. But what will cause human death, when aging will be abolished?

The Role of Autophagy, Mitophagy and Lysosomal Functions in Modulating Bioenergetics and Survival in the Context of Redox and Proteotoxic Damage: Implications for Neurodegenerative Diseases

Redox and proteotoxic stress contributes to age-dependent accumulation of dysfunctional mitochondria and protein aggregates, and is associated with neurodegeneration. The free radical theory of aging inspired many studies using reactive species scavengers such as alpha-tocopherol, ascorbate and coenzyme Q to suppress the initiation of oxidative stress. However, clinical trials have had limited success in the treatment of neurodegenerative diseases. We ascribe this to the emerging literature which suggests that the oxidative stress hypothesis does not encompass the role of reactive species in cell signaling and therefore the interception with reactive species with antioxidant supplementation may result in disruption of redox signaling. In addition, the accumulation of redox modified proteins or organelles cannot be reversed by oxidant intercepting antioxidants and must then be removed by alternative mechanisms. We have proposed that autophagy serves this essential function in removing damaged or dysfunctional proteins and organelles thus preserving neuronal function and survival. In this review, we will highlight observations regarding the impact of autophagy regulation on cellular bioenergetics and survival in response to reactive species or reactive species generating compounds, and in response to proteotoxic stress.

Omega-3 fatty acids partially revert the metabolic gene expression profile induced by long-term calorie restriction

Calorie restriction (CR) consistently extends longevity and delays age-related diseases across several animal models. We have previously shown that different dietary fat sources can modulate life span and mitochondrial ultrastructure, function and membrane fatty acid composition in mice maintained on a 40% CR. In particular, animals consuming lard as the main fat source (CR-Lard) lived longer than CR mice consuming diets with soybean oil (CR-Soy) or fish oil (CR-Fish) as the predominant lipid source. In the present work, a transcriptomic analysis in the liver and skeletal muscle was performed in order to elucidate possible mechanisms underlying the changes in energy metabolism and longevity induced by dietary fat in CR mice. After 8 months of CR, transcription downstream of several mediators of inflammation was inhibited in liver. In contrast, proinflammatory signaling was increased in the CR-Fish versus other CR groups. Dietary fish oil induced a gene expression pattern consistent with increased transcriptional regulation by several cytokines (TNF, GM-CSF, TGF-β) and sex hormones when compared to the other CR groups. The CR-Fish also had lower expression of genes involved in fatty acid biosynthesis and increased expression of mitochondrial and peroxisomal fatty acid β-oxidation genes than the other CR diet groups. Our data suggest that a diet high in n-3 PUFA, partially reverts CR-related changes in gene expression of key processes, such as inflammation and steroid hormone signaling, and this may mitigate life span extension with CR in mice consuming diets high in fish oil.

The Progress of Mitophagy and Related Pathogenic Mechanisms of the Neurodegenerative Diseases and Tumor

Mitochondrion, an organelle with two layers of membrane, is extremely vital to eukaryotic cell. Its major functions are energy center and apoptosis censor inside cell. The intactness of mitochondrial membrane is important to maintain its structure and function. Mitophagy is one kind of autophagy. In recent years, studies of mitochondria have shown that mitophagy is regulated by various factors and is an important regulation mechanism for organisms to maintain their normal state. In addition, abnormal mitophagy is closely related to several neurodegenerative diseases and tumor. However, the related signal pathway and its regulation mechanism still remain unclear. As a result, summarizing the progress of mitophagy and its related pathogenic mechanism not only helps to reveal the complicated molecular mechanism, but also helps to find a new target to treat the related diseases.

Molecular Pathways: Increased Susceptibility to Infection Is a Complication of mTOR Inhibitor Use in Cancer Therapy

As one of the earliest examples of "chemical biology," the M: echanistic T: arget of R: apamycin (mTOR) protein and its chemical inhibitors have been extensively studied across a spectrum of physiologic and pathologic processes at the molecular, organismal, and patient population levels. There are several FDA-approved mTOR inhibitors (sirolimus, everolimus, and temsirolimus) with indications for cancer treatment and for prevention of solid organ rejection. Dozens of mTOR inhibitors are currently being evaluated in hundreds of ongoing clinical trials across a spectrum of diseases, including numerous cancer indications, autoimmune diseases, and a number of congenital disorders. As many of the approved and investigational indications for mTOR inhibitors require long-term treatment, the magnitude and incidence of particular side effects differ from those observed in shorter-term treatments. Here, we focus on the increased risk of infections in patients being treated with mTOR inhibitors. While increased infection rates might be expected from a class of drugs approved as posttransplant immunosuppressants, we review reports from clinical, mechanistic, and genetically engineered mouse model studies detailing a much more nuanced view of mTOR inhibitor drug action and target biology.

Genetics and pharmacology of longevity: the road to therapeutics for healthy aging

Aging can be defined as the progressive decline in tissue and organismal function and the ability to respond to stress that occurs in association with homeostatic failure and the accumulation of molecular damage. Aging is the biggest risk factor for human disease and results in a wide range of aging pathologies. Although we do not completely understand the underlying molecular basis that drives the aging process, we have gained exceptional insights into the plasticity of life span and healthspan from the use of model organisms such as the worm Caenorhabditis elegans and the fruit fly Drosophila melanogaster. Single-gene mutations in key cellular pathways that regulate environmental sensing, and the response to stress, have been identified that prolong life span across evolution from yeast to mammals. These genetic manipulations also correlate with a delay in the onset of tissue and organismal dysfunction. While the molecular genetics of aging will remain a prosperous and attractive area of research in biogerontology, we are moving towards an era defined by the search for therapeutic drugs that promote healthy aging. Translational biogerontology will require incorporation of both therapeutic and pharmacological concepts. The use of model organisms will remain central to the quest for drug discovery, but as we uncover molecular processes regulated by repurposed drugs and polypharmacy, studies of pharmacodynamics and pharmacokinetics, drug-drug interactions, drug toxicity, and therapeutic index will slowly become more prevalent in aging research. As we move from genetics to pharmacology and therapeutics, studies will not only require demonstration of life span extension and an underlying molecular mechanism, but also the translational relevance for human health and disease prevention.

Diet-induced changes in brain structure and behavior in old gerbils

Background/Objectives:

Aging is associated with many physiological alterations such as changes in metabolism, food intake and brain dysfunction. Possible ways to correct age-related brain dysfunction using dietary treatments still remains undeveloped. The aim of our research was to investigate whether long-term dietary treatment with 2-oxoglutarate (2-OX), which is involved in many regulatory pathways, together with pancreatic-like enzymes of microbial origin (PLEM), which ensure appropriate digestion and absorption of nutrients, affects age-related changes in the brain morphology and cognitive function in old Mongolian gerbils.

Materials/methods:

Experiment was comprised of two separate studies. Samples of the hippocampus were obtained from male Mongolian gerbils of different ages (n=63 in the first study, n=74 in the second study). Immunohistochemistry was used for visualization of the nestin/NeuN-positive neuronal progenitors. Changes in amount of neural cell adhesion molecules (NCAMs) were estimated using enzyme-linked immunosorbent assay. For assessment of cognitive and sensorimotor functions, the T-maze spontaneous alternation test and the adhesive removal test (ART) were used. The ultrastructure of the CA1 hippocampal area was visualized using transmission electron microscopy.

Results:

Long-term treatment with 2-OX+PLEM led to a significantly increased amount of nestin/NeuN-positive cells in the CA1 hippocampal area and positive changes in learning and sensorimotor functions. As for synaptic transmission, changes in the spatial distribution of synaptic vesicles, as well as the redistribution of NCAM forms, were observed in the hippocampal synapses of the old gerbils.

Conclusions:

Taken together, our data show that dietary supplementation with 2-OX+PLEM not only enhances the proliferation and differentiation of neuronal progenitors, but also improves age-related deficits in the morphological and functional state of the brain of old gerbils. Thus, suggesting that a 2-OX+PLEM-enriched diet could also improve brain functions that have deteriorated with age.

Insights from yeast into whether the inhibition of heat shock transcription factor (Hsf1) by rapamycin can prevent the Hsf1 activation that results from treatment with an Hsp90 inhibitor

In human cells TORC1 mTOR (target of rapamycin) protein kinase complex renders heat shock transcription factor 1 (Hsf1) competent for stress activation. In such cells, as well as in yeast, the selective TORC1 inhibitor rapamycin blocks this activation in contrast to Hsp90 inhibitors which potently activate Hsf1. Potentially therefore rapamycin could prevent the Hsf1 activation that frequently compromises the efficiency of Hsp90 inhibitor cancer drugs. Little synergy was found between the effects of rapamycin and the Hsp90 inhibitor radicicol on yeast growth. However certain rapamycin resistance mutations sensitised yeast to Hsp90 inhibitor treatment and an Hsp90 mutation that overactivates Hsf1 sensitised cells to rapamycin. Rapamycin inhibition of the yeast Hsf1 was abolished by this Hsp90 mutation, as well as with the loss of Ppt1, the Hsp90-interacting protein phosphatase that is the ortholog of mammalian PP5. Unexpectedly Hsf1 activation was found to have a requirement for the rapamycin binding immunophilin FKBP12 even in the absence of rapamycin, while TORC1 “bypass” strains revealed that the rapamycin inhibition of yeast Hsf1 is not exerted through two of the major downstream targets of TORC1, the protein phosphatase regulator Tap42 and the protein kinase Sch9 – the latter the ortholog of human S6 protein kinase 1.

Significance: A problem with most of the Hsp90 inhibitor drugs now in cancer clinic trials is that they potently activate Hsf1. This leads to an induction of heat shock proteins, many of which have a “pro-survival” role in that they help to protect cells from apopotosis. As the activation of Hsf1 requires TORC1, inhibitors of mTOR kinase could potentially block this activation of Hsf1 and be of value when used in combination drug therapies with Hsp90 inhibitors. However many of the mechanistic details of the TORC1 regulation of Hsf1, as well as the interplay between cellular resistances to rapamycin and to Hsp90 inhibitors, still remain to be resolved.

Drug synergy drives conserved pathways to increase fission yeast lifespan

Aging occurs over time with gradual and progressive loss of physiological function. Strategies to reduce the rate of functional loss and mitigate the subsequent onset of deadly age-related diseases are being sought. We demonstrated previously that a combination of rapamycin and myriocin reduces age-related functional loss in the Baker’s yeast Saccharomyces cerevisiae and produces a synergistic increase in lifespan. Here we show that the same drug combination also produces a synergistic increase in the lifespan of the fission yeast Schizosaccharomyces pombe and does so by controlling signal transduction pathways conserved across a wide evolutionary time span ranging from yeasts to mammals. Pathways include the target of rapamycin complex 1 (TORC1) protein kinase, the protein kinase A (PKA) and a stress response pathway, which in fission yeasts contains the Sty1 protein kinase, an ortholog of the mammalian p38 MAP kinase, a type of Stress Activated Protein Kinase (SAPK). These results along with previous studies in S. cerevisiae support the premise that the combination of rapamycin and myriocin enhances lifespan by regulating signaling pathways that couple nutrient and environmental conditions to cellular processes that fine-tune growth and stress protection in ways that foster long term survival. The molecular mechanisms for fine-tuning are probably species-specific, but since they are driven by conserved nutrient and stress sensing pathways, the drug combination may enhance survival in other organisms.

Mechanisms of development of multimorbidity in the elderly

In ageing populations many patients have multiple diseases characterised by acceleration of the normal ageing process. Better understanding of the signalling pathways and cellular events involved in ageing shows that these are characteristic of many chronic degenerative diseases, such as chronic obstructive pulmonary disease (COPD), chronic cardiovascular and metabolic diseases, and neurodegeneration. Common mechanisms have now been identified in these diseases, which show evidence of cellular senescence with telomere shortening, activation of PI3K–AKT–mTOR signalling, impaired autophagy, mitochondrial dysfunction, stem cell exhaustion, epigenetic changes, abnormal microRNA profiles, immunosenescence and low grade chronic inflammation (“inflammaging”). Many of these pathways are driven by chronic oxidative stress. There is also a reduction in anti-ageing molecules, such as sirtuins and Klotho, which further accelerates the ageing process. Understanding these molecular mechanisms has identified several novel therapeutic targets and several drugs have already been developed that may slow the ageing process, as well as lifestyle interventions, such as diet and physical activity. This indicates that in the future new treatment approaches may target the common pathways involved in multimorbidity and this area of research should be given high priority. Thus, COPD should be considered as a component of multimorbidity and common disease pathways, particularly accelerated ageing, should be targeted.

Teaching the basics of autophagy and mitophagy to redox biologists--mechanisms and experimental approaches

Autophagy is a lysosomal mediated degradation activity providing an essential mechanism for recycling cellular constituents, and clearance of excess or damaged lipids, proteins and organelles. Autophagy involves more than 30 proteins and is regulated by nutrient availability, and various stress sensing signaling pathways. This article provides an overview of the mechanisms and regulation of autophagy, its role in health and diseases, and methods for its measurement. Hopefully this teaching review together with the graphic illustrations will be helpful for instructors teaching graduate students who are interested in grasping the concepts and major research areas and introducing recent developments in the field.

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mTOR, Beclin–VPS34, LC3 homologs, and adaptor proteins in autophagy.

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Autophagosomal membranes may derive from multiple sources.

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Autophagosomal–lysosomal fusion contributes to the control of autophagic flux.

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Assess autophagy by autophagosomal and protein turnover, and morphological alterations.

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Autophagy adysfunction in cancer, aging, neurodegeneration and infection.

Rapamycin reduces fibroblast proliferation without causing quiescence and induces STAT5A/B-mediated cytokine production

Rapamycin is a well-known inhibitor of the Target of Rapamycin (TOR) signaling cascade; however, the impact of this drug on global genome function and organization in normal primary cells is poorly understood. To explore this impact, we treated primary human foreskin fibroblasts with rapamycin and observed a decrease in cell proliferation without causing cell death. Upon rapamycin treatment chromosomes 18 and 10 were repositioned to a location similar to that of fibroblasts induced into quiescence by serum reduction. Although similar changes in positioning occurred, comparative transcriptome analyses demonstrated significant divergence in gene expression patterns between rapamycin-treated and quiescence-induced fibroblasts. Rapamycin treatment induced the upregulation of cytokine genes, including those from the Interleukin (IL)-6 signaling network, such as IL-8 and the Leukemia Inhibitory Factor (LIF), while quiescent fibroblasts demonstrated up-regulation of genes involved in the complement and coagulation cascade. In addition, genes significantly up-regulated by rapamycin treatment demonstrated increased promoter occupancy of the transcription factor Signal Transducer and Activator of Transcription 5A/B (STAT5A/B). In summary, we demonstrated that the treatment of fibroblasts with rapamycin decreased proliferation, caused chromosome territory repositioning and induced STAT5A/B-mediated changes in gene expression enriched for cytokines.

Ageing and the border between health and disease

Ageing is associated with a progressive degeneration of the tissues, which has a negative impact on the structure and function of vital organs and is among the most important known risk factors for most chronic diseases. Since the proportion of the world's population aged >60 years will double in the next four decades, this will be accompanied by an increased incidence of chronic age-related diseases that will place a huge burden on healthcare resources. There is increasing evidence that many chronic inflammatory diseases represent an acceleration of the ageing process. Chronic pulmonary diseases represents an important component of the increasingly prevalent multiple chronic debilitating diseases, which are a major cause of morbidity and mortality, particularly in the elderly. The lungs age and it has been suggested that chronic obstructive pulmonary disease (COPD) is a condition of accelerated lung ageing and that ageing may provide a mechanistic link between COPD and many of its extrapulmonary effects and comorbidities. In this article we will describe the physiological changes and mechanisms of ageing, with particular focus on the pulmonary effects of ageing and how these may be relevant to the development of COPD and its major extrapulmonary manifestations.

High nutrient levels and TORC1 activity reduce cell viability following prolonged telomere dysfunction and cell cycle arrest

Cells challenged with DNA damage activate checkpoints to arrest the cell cycle and allow time for repair. Successful repair coupled to subsequent checkpoint inactivation is referred to as recovery. When DNA damage cannot be repaired, a choice between permanent arrest and cycling in the presence of damage (checkpoint adaptation) must be made. While permanent arrest jeopardizes future lineages, continued proliferation is associated with the risk of genome instability. We demonstrate that nutritional signaling through target of rapamycin complex 1 (TORC1) influences the outcome of this decision. Rapamycin-mediated TORC1 inhibition prevents checkpoint adaptation via both Cdc5 inactivation and autophagy induction. Preventing adaptation results in increased cell viability and hence proliferative potential. In accordance, the ability of rapamycin to increase longevity is dependent upon the DNA damage checkpoint. The crosstalk between TORC1 and the DNA damage checkpoint may have important implications in terms of therapeutic alternatives for diseases associated with genome instability.

Aging and energetics' 'Top 40' future research opportunities 2010-2013

BACKGROUND

As part of a coordinated effort to expand our research activity at the interface of Aging and Energetics a team of investigators at The University of Alabama at Birmingham systematically assayed and catalogued the top research priorities identified in leading publications in that domain, believing the result would be useful to the scientific community at large.

OBJECTIVE

To identify research priorities and opportunities in the domain of aging and energetics as advocated in the 40 most cited papers related to aging and energetics in the last 4 years.

DESIGN

The investigators conducted a search for papers on aging and energetics in Scopus, ranked the resulting papers by number of times they were cited, and selected the ten most-cited papers in each of the four years that include 2010 to 2013, inclusive.

RESULTS

  Ten research categories were identified from the 40 papers.  These included: (1) Calorie restriction (CR) longevity response, (2) role of mTOR (mechanistic target of Rapamycin) and related factors in lifespan extension, (3) nutrient effects beyond energy (especially resveratrol, omega-3 fatty acids, and selected amino acids), 4) autophagy and increased longevity and health, (5) aging-associated predictors of chronic disease, (6) use and effects of mesenchymal stem cells (MSCs), (7) telomeres relative to aging and energetics, (8) accretion and effects of body fat, (9) the aging heart,  and (10) mitochondria, reactive oxygen species, and cellular energetics.

CONCLUSION

The field is rich with exciting opportunities to build upon our existing knowledge about the relations among aspects of aging and aspects of energetics and to better understand the mechanisms which connect them.

The search for antiaging interventions: from elixirs to fasting regimens

The phenomenon of aging is an intrinsic feature of life. Accordingly, the possibility to manipulate it has fascinated humans likely since time immemorial. Recent evidence is shaping a picture where low caloric regimes and exercise may improve healthy senescence, and several pharmacological strategies have been suggested to counteract aging. Surprisingly, the most effective interventions proposed to date converge on only a few cellular processes, in particular nutrient signaling, mitochondrial efficiency, proteostasis, and autophagy. Here, we critically examine drugs and behaviors to which life- or healthspan-extending properties have been ascribed and discuss the underlying molecular mechanisms.

Extension of Saccharomyces paradoxus chronological lifespan by retrotransposons in certain media conditions is associated with changes in reactive oxygen species

Retrotransposons are mobile DNA elements present throughout eukaryotic genomes that can cause mutations and genome rearrangements when they replicate through reverse transcription. Increased expression and/or mobility of retrotransposons has been correlated with aging in yeast, Caenorhabditis elegans, Drosophila melanogaster, and mammals. The many copies of retrotransposons in humans and various model organisms complicate further pursuit of this relationship. The Saccharomyces cerevisiae Ty1 retrotransposon was introduced into a strain of S. paradoxus that completely lacks retrotransposons to compare chronological lifespans (CLSs) of yeast strains with zero, low, or high Ty1 copy number. Yeast chronological lifespan reflects the progressive loss of cell viability in a nondividing state. Chronological lifespans for the strains were not different in rich medium, but were extended in high Ty1 copy-number strains in synthetic medium and in rich medium containing a low dose of hydroxyurea (HU), an agent that depletes deoxynucleoside triphosphates. Lifespan extension was not strongly correlated with Ty1 mobility or mutation rates for a representative gene. Buffering deoxynucleoside triphosphate levels with threonine supplementation did not substantially affect this lifespan extension, and no substantial differences in cell cycle arrest in the nondividing cells were observed. Lifespan extension was correlated with reduced reactive oxygen species during early stationary phase in high Ty1 copy strains, and antioxidant treatment allowed the zero Ty1 copy strain to live as long as high Ty1 copy-number strains in rich medium with hydroxyurea. This exceptional yeast system has identified an unexpected longevity-promoting role for retrotransposons that may yield novel insights into mechanisms regulating lifespan.

Weekly administration of rapamycin improves survival and biomarkers in obese male mice on high-fat diet

Recent discoveries have revealed the key role of mTOR (target of rapamycin) in aging. Furthermore, rapamycin extends lifespan in mice, especially in female mice. Here, we treated obese male mice on high-fat diet with rapamycin given intermittently: either weekly (once a week) or alternating bi-weekly (three injections every other week). While only marginally reducing obesity, intermittent administration of rapamycin significantly extended lifespan. Significance was achieved for weekly treated group and for the three rapamycin-received groups combined. In weekly treatment group, 100% mice were alive by the age of 2 years, whereas 60% of mice died in untreated group by this age. The effect of weekly treatment on survival was highly significant and cannot be fully explained by partial reduction in obesity. Alternating bi-weekly treatments seem to be less effective than weekly treatment, although effects of additional factors (see Discussion) may not be excluded. After one year of treatment, all survived mice were sacrificed 8 days after the last administration of rapamycin to avoid its direct interference with parameters examined. Fasting levels of cardiac and hepatic p-S6, a marker of mTORC1 activity, were lower in weekly treatment group compared with control mice. In contrast, levels of p-Akt (S473), glucose, triglycerides and insulin were unchanged, whereas leptin and IGF-1 tended to be lower. Thus, weekly treatment with rapamycin may slow down aging in obese male mice on high-fat diet.