Autophagy is required for dietary restriction-mediated life span extension in C. elegans

Autophagy and metabolic aging: Current understanding and future applications

"Metabolic aging" refers to the gradual decline in cellular metabolic function across various tissues due to defective hormonal signaling, impaired nutrient sensing, mitochondrial dysfunction, replicative stress, and cellular senescence. While this process usually corresponds with chronological aging, the recent increase in metabolic diseases and cancers occurring at younger ages in humans suggests the premature onset of cellular fatigue and metabolic aging. Autophagy, a cellular housekeeping process facilitated by lysosomes, plays a crucial role in maintaining tissue rejuvenation and health. However, various environmental toxins, hormones, lifestyle changes, and nutrient imbalances can disrupt autophagy in humans. In this review, we explore the connection between autophagy and cellular metabolism, its regulation by extrinsic factors and its modulation to prevent the early onset of metabolic aging.

C. elegans: a prominent platform for modeling and drug screening in neurological disorders

INTRODUCTION

Human neurodevelopmental and neurodegenerative diseases (NDevDs and NDegDs, respectively) encompass a broad spectrum of disorders affecting the nervous system with an increasing incidence. In this context, the nematode C. elegans, has emerged as a benchmark model for biological research, especially in the field of neuroscience.

AREAS COVERED

The authors highlight the numerous advantages of this tiny worm as a model for exploring nervous system pathologies and as a platform for drug discovery. There is a particular focus given to describing the existing models of C. elegans for the study of NDevDs and NDegDs. Specifically, the authors underscore their strong applicability in preclinical drug development. Furthermore, they place particular emphasis on detailing the common techniques employed to explore the nervous system in both healthy and diseased states.

EXPERT OPINION

Drug discovery constitutes a long and expensive process. The incorporation of invertebrate models, such as C. elegans, stands as an exemplary strategy for mitigating costs and expediting timelines. The utilization of C. elegans as a platform to replicate nervous system pathologies and conduct high-throughput automated assays in the initial phases of drug discovery is pivotal for rendering therapeutic options more attainable and cost-effective.

Dietary restriction reveals sex-specific expression of the mTOR pathway genes in Japanese quails

Limited resources affect an organism's physiology through the conserved metabolic pathway, the mechanistic target of rapamycin (mTOR). Males and females often react differently to nutritional limitation, but whether it leads to differential mTOR pathway expression remains unknown. Recently, we found that dietary restriction (DR) induced significant changes in the expression of mTOR pathway genes in female Japanese quails (Coturnix japonica). We simultaneously exposed 32 male and female Japanese quails to either 20%, 30%, 40% restriction or ad libitum feeding for 14 days and determined the expression of six key genes of the mTOR pathway in the liver to investigate sex differences in the expression patterns. We found that DR significantly reduced body mass, albeit the effect was milder in males compared to females. We observed sex-specific liver gene expression. DR downregulated mTOR expression more in females than in males. Under moderate DR, ATG9A and RPS6K1 expressions were increased more in males than in females. Like females, body mass in males was correlated positively with mTOR and IGF1, but negatively with ATG9A and RS6K1 expressions. Our findings highlight that sexes may cope with nutritional deficits differently and emphasise the importance of considering sexual differences in studies of dietary restriction.

Induction of proteasomal activity in mammalian cells by lifespan-extending tRNA synthetase inhibitors

We have recently shown that multiple tRNA synthetase inhibitors can greatly increase lifespan in multiple models by acting through the conserved transcription factor ATF4. Here, we show that these compounds, and several others of the same class, can greatly upregulate mammalian ATF4 in cells in vitro, in a dose dependent manner. Further, RNASeq analysis of these cells pointed toward changes in protein turnover. In subsequent experiments here we show that multiple tRNA synthetase inhibitors can greatly upregulate activity of the ubiquitin proteasome system (UPS) in cells in an ATF4-dependent manner. The UPS plays an important role in the turnover of many damaged or dysfunctional proteins in an organism. Increasing UPS activity has been shown to enhance the survival of Huntington's disease cell models, but there are few known pharmacological enhancers of the UPS. Additionally, we see separate ATF4 dependent upregulation of macroautophagy upon treatment with tRNA synthetase inhibitors. Protein degradation is an essential cellular process linked to many important human diseases of aging such as Alzheimer's disease and Huntington's disease. These drugs' ability to enhance proteostasis more broadly could have wide-ranging implications in the treatment of important age-related neurodegenerative diseases.

Longitudinal modeling of human neuronal aging reveals the contribution of the RCAN1-TFEB pathway to Huntington's disease neurodegeneration

Aging is a common risk factor in neurodegenerative disorders. Investigating neuronal aging in an isogenic background stands to facilitate analysis of the interplay between neuronal aging and neurodegeneration. Here we perform direct neuronal reprogramming of longitudinally collected human fibroblasts to reveal genetic pathways altered at different ages. Comparative transcriptome analysis of longitudinally aged striatal medium spiny neurons (MSNs) in Huntington's disease identified pathways involving RCAN1, a negative regulator of calcineurin. Notably, RCAN1 protein increased with age in reprogrammed MSNs as well as in human postmortem striatum and RCAN1 knockdown rescued patient-derived MSNs of Huntington's disease from degeneration. RCAN1 knockdown enhanced chromatin accessibility of genes involved in longevity and autophagy, mediated through enhanced calcineurin activity, leading to TFEB's nuclear localization by dephosphorylation. Furthermore, G2-115, an analog of glibenclamide with autophagy-enhancing activities, reduced the RCAN1-calcineurin interaction, phenocopying the effect of RCAN1 knockdown. Our results demonstrate that targeting RCAN1 genetically or pharmacologically can increase neuronal resilience in Huntington's disease.

MALT-1 shortens lifespan by inhibiting autophagy in the intestine of C. elegans

The caspase-like protease MALT1 promotes immune responses and oncogenesis in mammals by activating the transcription factor NF-κB. MALT1 is remarkably conserved from mammals to simple metazoans devoid of NF-κB homologs, like the nematode C. elegans. To discover more ancient, NF-κB -independent MALT1 functions, we analysed the phenotype of C. elegans upon silencing of MALT-1 expression systemically or in a tissue-specific manner. MALT-1 silencing in the intestine caused a significant increase in life span, whereas intestinal overexpression of MALT-1 shortened life expectancy. Interestingly, MALT-1-deficient animals showed higher constitutive levels of autophagy in the intestine, which were particularly evident in aged or starved nematodes. Silencing of the autophagy regulators ATG-13, BEC-1 or LGG-2, but not the TOR homolog LET-363, reversed lifespan extension caused by MALT-1 deficiency. These findings suggest that MALT-1 limits the lifespan of C. elegans by acting as an inhibitor of an early step of autophagy in the intestine.

Nuclear hormone receptor NHR-49 is an essential regulator of stress resilience and healthy aging in Caenorhabditis elegans

The genome of Caenorhabditis elegans encodes 284 nuclear hormone receptor, which perform diverse functions in development and physiology. One of the best characterized of these is NHR-49, related in sequence and function to mammalian hepatocyte nuclear factor 4α and peroxisome proliferator-activated receptor α. Initially identified as regulator of lipid metabolism, including fatty acid catabolism and desaturation, additional important roles for NHR-49 have since emerged. It is an essential contributor to longevity in several genetic and environmental contexts, and also plays vital roles in the resistance to several stresses and innate immune response to infection with various bacterial pathogens. Here, we review how NHR-49 is integrated into pertinent signaling circuits and how it achieves its diverse functions. We also highlight areas for future investigation including identification of regulatory inputs that drive NHR-49 activity and identification of tissue-specific gene regulatory outputs. We anticipate that future work on this protein will provide information that could be useful for developing strategies to age-associated declines in health and age-related human diseases.

Unlocking the potential of Mesenchymal stem cells in liver Fibrosis: Insights into the impact of autophagy and aging

Liver fibrosis is a chronic liver disease characterized by extracellular matrix protein accumulation, potentially leading to cirrhosis or hepatocellular carcinoma. Liver cell damage, inflammatory responses, and apoptosis due to various reasons induce liver fibrosis. Although several treatments, such as antiviral drugs and immunosuppressive therapies, are available for liver fibrosis, they only provide limited efficacy. Mesenchymal stem cells (MSCs) have become a promising therapeutic option for liver fibrosis, because they can modulate the immune response, promote liver regeneration, and inhibit the activation of hepatic stellate cells that contribute to disease development. Recent studies have suggested that the mechanisms through which MSCs gain their antifibrotic properties involve autophagy and senescence. Autophagy, a vital cellular self-degradation process, is critical for maintaining homeostasis and protecting against nutritional, metabolic, and infection-mediated stress. The therapeutic effects of MSCs depend on appropriate autophagy levels, which can improve the fibrotic process. Nonetheless, aging-related autophagic damage is associated with a decline in MSC number and function, which play a crucial role in liver fibrosis development. This review summarizes the recent advancements in the understanding of autophagy and senescence in MSC-based liver fibrosis treatment, presenting the key findings from relevant studies.

Autophagy protein 5 controls flow-dependent endothelial functions

Dysregulated autophagy is associated with cardiovascular and metabolic diseases, where impaired flow-mediated endothelial cell responses promote cardiovascular risk. The mechanism by which the autophagy machinery regulates endothelial functions is complex. We applied multi-omics approaches and in vitro and in vivo functional assays to decipher the diverse roles of autophagy in endothelial cells. We demonstrate that autophagy regulates VEGF-dependent VEGFR signaling and VEGFR-mediated and flow-mediated eNOS activation. Endothelial ATG5 deficiency in vivo results in selective loss of flow-induced vasodilation in mesenteric arteries and kidneys and increased cerebral and renal vascular resistance in vivo. We found a crucial pathophysiological role for autophagy in endothelial cells in flow-mediated outward arterial remodeling, prevention of neointima formation following wire injury, and recovery after myocardial infarction. Together, these findings unravel a fundamental role of autophagy in endothelial function, linking cell proteostasis to mechanosensing.

The hunger strikes back: an epigenetic memory for autophagy

Historical and demographical human cohorts of populations exposed to famine, as well as animal studies, revealed that exposure to food deprivation is associated to lasting health-related effects for the exposed individuals, as well as transgenerational effects in their offspring that affect their diseases' risk and overall longevity. Autophagy, an evolutionary conserved catabolic process, serves as cellular response to cope with nutrient starvation, allowing the mobilization of an internal source of stored nutrients and the production of energy. We review the evidence obtained in multiple model organisms that support the idea that autophagy induction, including through dietary regimes based on reduced food intake, is in fact associated to improved health span and extended lifespan. Thereafter, we expose autophagy-induced chromatin remodeling, such as DNA methylation and histone posttranslational modifications that are known heritable epigenetic marks, as a plausible mechanism for transgenerational epigenetic inheritance of hunger.

Increased alcohol dehydrogenase 1 activity promotes longevity

Several molecules can extend healthspan and lifespan across organisms. However, most are upstream signaling hubs or transcription factors orchestrating complex anti-aging programs. Therefore, these molecules point to but do not reveal the fundamental mechanisms driving longevity. Instead, downstream effectors that are necessary and sufficient to promote longevity across conditions or organisms may reveal the fundamental anti-aging drivers. Toward this goal, we searched for effectors acting downstream of the transcription factor EB (TFEB), known as HLH-30 in C. elegans, because TFEB/HLH-30 is necessary across anti-aging interventions and its overexpression is sufficient to extend C. elegans lifespan and reduce biomarkers of aging in mammals including humans. As a result, we present an alcohol-dehydrogenase-mediated anti-aging response (AMAR) that is essential for C. elegans longevity driven by HLH-30 overexpression, caloric restriction, mTOR inhibition, and insulin-signaling deficiency. The sole overexpression of ADH-1 is sufficient to activate AMAR, which extends healthspan and lifespan by reducing the levels of glycerol-an age-associated and aging-promoting alcohol. Adh1 overexpression is also sufficient to promote longevity in yeast, and adh-1 orthologs are induced in calorically restricted mice and humans, hinting at ADH-1 acting as an anti-aging effector across phyla.

Rilmenidine extends lifespan and healthspan in Caenorhabditis elegans via a nischarin I1-imidazoline receptor

Repurposing drugs capable of extending lifespan and health span has a huge untapped potential in translational geroscience. Here, we searched for known compounds that elicit a similar gene expression signature to caloric restriction and identified rilmenidine, an I1-imidazoline receptor agonist and prescription medication for the treatment of hypertension. We then show that treating Caenorhabditis elegans with rilmenidine at young and older ages increases lifespan. We also demonstrate that the stress-resilience, health span, and lifespan benefits of rilmenidine treatment in C. elegans are mediated by the I1-imidazoline receptor nish-1, implicating this receptor as a potential longevity target. Consistent with the shared caloric-restriction-mimicking gene signature, supplementing rilmenidine to calorically restricted C. elegans, genetic reduction of TORC1 function, or rapamycin treatment did not further increase lifespan. The rilmenidine-induced longevity required the transcription factors FOXO/DAF-16 and NRF1,2,3/SKN-1. Furthermore, we find that autophagy, but not AMPK signaling, was needed for rilmenidine-induced longevity. Moreover, transcriptional changes similar to caloric restriction were observed in liver and kidney tissues in mice treated with rilmenidine. Together, these results reveal a geroprotective and potential caloric restriction mimetic effect by rilmenidine that warrant fresh lines of inquiry into this compound.

An evaluation of aging measures: from biomarkers to clocks

With the increasing number of aged population and growing burden of healthy aging demands, a rational standard for evaluation aging is in urgent need. The advancement of medical testing technology and the prospering of artificial intelligence make it possible to evaluate the biological status of aging from a more comprehensive view. In this review, we introduced common aging biomarkers and concluded several famous aging clocks. Aging biomarkers reflect changes in the organism at a molecular or cellular level over time while aging clocks tend to be more of a generalization of the overall state of the organism. We expect to construct a framework for aging evaluation measurement from both micro and macro perspectives. Especially, population-specific aging clocks and multi-omics aging clocks may better fit the demands to evaluate aging in a comprehensive and multidimensional manner and make a detailed classification to represent different aging rates at tissue/organ levels. This framework will promisingly provide a crucial basis for disease diagnosis and intervention assessment in geroscience.

Tanshinone IIA loaded chitosan nanoparticles decrease toxicity of β-amyloid peptide in a Caenorhabditis elegans model of Alzheimer's disease

Alzheimer's disease (AD) is one of the most common neurodegenerative diseases that characterized by the accumulation of β-amyloid peptide (Aβ). Overexpressions of Aβ could induce oxidative stress that might be a key insult to initiate the cascades of Aβ accumulation. As a result, anti-oxidative stress and attenuating Aβ accumulation might be one promising intervention for AD treatment. Tanshinone IIA (Tan IIA), a major component of lipophilic tanshinones in Danshen, is proven to be effective in several diseases, including AD. Due to the poor solubility in water, the clinical application of Tan IIA was limited. Therefore, a great number of nanoparticles were designed to overcome this issue. In the current study, we choose chitson as delivery carrier to load Tanshinone IIA (CS@Tan IIA) and explore the protective effects of CS@Tan IIA on the CL2006 strain, a transgenic C. elegans of AD model organism. Compared with Tan IIA monomer, CS@Tan IIA could significantly prolong the lifespan and attenuate the AD-like symptoms, including reducing paralysis and the Aβ deposition by inhibiting the oxidative stress. The mechanism study showed that the protection of CS@Tan IIA was attenuated by knockdown of daf-16 gene, but not skn-1. The results indicated that DAF-16/SOD-3 pathway was required in the protective effects of CS@Tan IIA. Besides DAF-16/SOD-3 pathway, the Tan IIA-loaded CS nanoparticles might protect the C. elegans against the AD insults via promoting autophagy. All the results consistently suggested that coating by chitosan could improve the solubility of Tan IIA and effectively enhance the protective effects of Tan IIA on AD, which might provide a potential drug loading approach for the hydrophobic drugs as Tan IIA.

3-Bromopyruvate, a caloric restriction mimetic, exerts a mitohormetic effect to provide neuroprotection through activation of autophagy in rats during aging

In the present study, attempts have been made to evaluate the potential role of 3 Bromopyruvate (3-BP) a glycolytic inhibitor and a caloric restriction mimetic (CRM), to exert neuroprotection in rats during aging through modulation of autophagy. Young male rats (4 months), and naturally aged (22 months) male rats were supplemented with 3-BP (30 mg/kg b.w., orally) for 28 days. Our results demonstrate a significant increase in the antioxidant biomarkers (ferric reducing antioxidant potential level, total thiol, superoxide dismutase, and catalase activities) and a decrease in the level of pro-oxidant biomarkers such as protein carbonyl after 3-BP supplementation in brain tissues. A significant increase in reactive oxygen species (ROS) was observed due to the mitohormetic effect of 3-BP supplementation in the treated rats. Furthermore, the 3-BP treatment also enhanced the activities of electron transport chain complexes I and IV in aged brain mitochondria thus proving its antioxidant potential at the level of mitochondria. Gene expression analysis with reverse transcriptase-polymerase chain reaction (RT-PCR) was performed to assess the expression of autophagy, neuroprotective and aging marker genes. RT-PCR data revealed that 3-BP up-regulated the expression of autophagy markers genes (Beclin-1 and LC3 β), sirtuin-1, and neuronal marker gene (NSE), respectively in the aging brain. The results suggest that 3-BP induces a mitohormetic effect through the elevation of ROS which reinforces defensive mechanism(s) targeted at regulating autophagy. These findings suggest that consistently low-dose 3-BP may be beneficial for neuroprotection during aging and age-related disorders.

Autophagy at the intersection of aging, senescence, and cancer

Autophagy is an evolutionarily conserved cellular process in which macromolecules undergo lysosomal degradation. It fulfills essential roles in quality controlling cellular constituents and in energy homeostasis. Basal autophagy is also widely accepted to provide a protective role in aging and aging-related disorders, and its decline with age might precipitate the onset of a variety of diseases. In this review, we discuss the role of basal autophagy in maintaining homeostasis, in part through the maintenance of stem cell populations and the prevention of cellular senescence. We also consider how stress-induced senescence, for example, during oncogene activation and in premalignant disease, might rely on autophagy, and the possibility that the age-associated decline in autophagy might promote tumour development through a variety of mechanisms. Ultimately, evidence suggests that autophagy is required for malignant cancer progression in a number of settings. Thus, autophagy appears to be tumour-suppressive during the early stages of tumorigenesis and tumour-promoting at later stages.

HSF-1: Guardian of the Proteome Through Integration of Longevity Signals to the Proteostatic Network

Discoveries made in the nematode Caenorhabditis elegans revealed that aging is under genetic control. Since these transformative initial studies, C. elegans has become a premier model system for aging research. Critically, the genes, pathways, and processes that have fundamental roles in organismal aging are deeply conserved throughout evolution. This conservation has led to a wealth of knowledge regarding both the processes that influence aging and the identification of molecular and cellular hallmarks that play a causative role in the physiological decline of organisms. One key feature of age-associated decline is the failure of mechanisms that maintain proper function of the proteome (proteostasis). Here we highlight components of the proteostatic network that act to maintain the proteome and how this network integrates into major longevity signaling pathways. We focus in depth on the heat shock transcription factor 1 (HSF1), the central regulator of gene expression for proteins that maintain the cytosolic and nuclear proteomes, and a key effector of longevity signals.

Beth Levine’s Legacy: From the Discovery of BECN1 to Therapies. A Mentees’ Perspective

With great sadness, the scientific community received the news of the loss of Beth Levine on 15 June 2020. Dr. Levine was a pioneer in the autophagy field and work in her lab led not only to a better understanding of the molecular mechanisms regulating the pathway, but also its implications in multiple physiological and pathological conditions, including its role in development, host defense, tumorigenesis, aging or metabolism. This review does not aim to provide a comprehensive view of autophagy, but rather an outline of some of the discoveries made by the group of Beth Levine, from the perspective of some of her own mentees, hoping to honor her legacy in science.

Perturbation of autophagy: An intrinsic toxicity mechanism of nanoparticles

Nanoparticles (NPs) have been widely used for various purposes due to their unique physicochemical properties. Such widespread applications greatly increase the possibility of human exposure to NPs in various ways. Once entering the human body, NPs may interfere with cellular homeostasis and thus affect the physiological system. As a result, it is necessary to evaluate the potential disturbance of NPs to multiple cell functions, including autophagy. Autophagy is an important cell function to maintain cellular homeostasis, and minimizing the disturbance caused by NP exposures to autophagy is critical to nanosafety. Herein, we summarized the recent research progress in nanotoxicity with particular focuses on the perturbation of NPs to cell autophagy. The basic processes of autophagy and complex relationships between autophagy and major human diseases were further discussed to emphasize the importance of keeping autophagy under control. Moreover, the most recent advances on perturbation of different types of NPs to autophagy were also reviewed. Last but not least, we also discussed major research challenges and potential coping strategies and proposed a safe-by-design strategy towards safer applications of NPs.

Nutrient-Response Pathways in Healthspan and Lifespan Regulation

Cellular, small invertebrate and vertebrate models are a driving force in biogerontology studies. Using various models, such as yeasts, appropriate tissue culture cells, Drosophila, the nematode Caenorhabditis elegans and the mouse, has tremendously increased our knowledge around the relationship between diet, nutrient-response signaling pathways and lifespan regulation. In recent years, combinatorial drug treatments combined with mutagenesis, high-throughput screens, as well as multi-omics approaches, have provided unprecedented insights in cellular metabolism, development, differentiation, and aging. Scientists are, therefore, moving towards characterizing the fine architecture and cross-talks of growth and stress pathways towards identifying possible interventions that could lead to healthy aging and the amelioration of age-related diseases in humans. In this short review, we briefly examine recently uncovered knowledge around nutrient-response pathways, such as the Insulin Growth Factor (IGF) and the mechanistic Target of Rapamycin signaling pathways, as well as specific GWAS and some EWAS studies on lifespan and age-related disease that have enhanced our current understanding within the aging and biogerontology fields. We discuss what is learned from the rich and diverse generated data, as well as challenges and next frontiers in these scientific disciplines.

Sonneradon A Extends Lifespan of Caenorhabditis elegans by Modulating Mitochondrial and IIS Signaling Pathways

Aging is related to the lowered overall functioning and increased risk for various age-related diseases in humans. Sonneradon A (SDA), a new compound first extracted from the edible fruits of mangrove Sonneratia apetala, showed remarkable antiaging activity. However, the role of SDA in antiaging remains unclear. In this article, we studied the function of SDA in antiaging by using the animal model Caenorhabditis elegans. Results showed that SDA inhibited production of reactive oxygen species (ROS) by 53%, and reduced the accumulation of aging markers such as lipids and lipofuscins. Moreover, SDA also enhanced the innate immune response to Pseudomonas aeruginosa infection. Genetic analysis of a series of mutants showed that SDA extended the lifespan of the mutants of eat-2 and glp-1. Together, this effect may be related to the enhanced resistance to oxidative stress via mitochondrial and insulin/insulin-like growth factor-1 signaling (IIS) pathways. The results of this study provided new evidence for an antiaging effect of SDA in C. elegans, as well as insights into the implication of antiaging activity of SDA in higher organisms.

Overview of Polyamines as Nutrients for Human Healthy Long Life and Effect of Increased Polyamine Intake on DNA Methylation

Polyamines, spermidine and spermine, are synthesized in every living cell and are therefore contained in foods, especially in those that are thought to contribute to health and longevity. They have many physiological activities similar to those of antioxidant and anti-inflammatory substances such as polyphenols. These include antioxidant and anti-inflammatory properties, cell and gene protection, and autophagy activation. We have first reported that increased polyamine intake (spermidine much more so than spermine) over a long period increased blood spermine levels and inhibited aging-associated pathologies and pro-inflammatory status in humans and mice and extended life span of mice. However, it is unlikely that the life-extending effect of polyamines is exerted by the same bioactivity as polyphenols because most studies using polyphenols and antioxidants have failed to demonstrate their life-extending effects. Recent investigations revealed that aging-associated pathologies and lifespan are closely associated with DNA methylation, a regulatory mechanism of gene expression. There is a close relationship between polyamine metabolism and DNA methylation. We have shown that the changes in polyamine metabolism affect the concentrations of substances and enzyme activities involved in DNA methylation. I consider that the increased capability of regulation of DNA methylation by spermine is a key of healthy long life of humans.

Emerging roles of ATG7 in human health and disease

The cardinal stages of macroautophagy are driven by core autophagy-related (ATG) proteins, whose ablation largely abolishes intracellular turnover. Disrupting ATG genes is paradigmatic of studying autophagy deficiency, yet emerging data suggest that ATG proteins have extensive biological importance beyond autophagic elimination. An important example is ATG7, an essential autophagy effector enzyme that in concert with other ATG proteins, also regulates immunity, cell death and protein secretion, and independently regulates the cell cycle and apoptosis. Recently, a direct association between ATG7 dysfunction and disease was established in patients with biallelic ATG7 variants and childhood-onset neuropathology. Moreover, a prodigious body of evidence supports a role for ATG7 in protecting against complex disease states in model organisms, although how dysfunctional ATG7 contributes to manifestation of these diseases, including cancer, neurodegeneration and infection, in humans remains unclear. Here, we systematically review the biological functions of ATG7, discussing the impact of its impairment on signalling pathways and human pathology. Future studies illuminating the molecular relationship between ATG7 dysfunction and disease will expedite therapies for disorders involving ATG7 deficiency and/or impaired autophagy.

Autophagy in metabolic disease and ageing

Autophagy is an evolutionarily conserved, lysosome-dependent catabolic process whereby cytoplasmic components, including damaged organelles, protein aggregates and lipid droplets, are degraded and their components recycled. Autophagy has an essential role in maintaining cellular homeostasis in response to intracellular stress; however, the efficiency of autophagy declines with age and overnutrition can interfere with the autophagic process. Therefore, conditions such as sarcopenic obesity, insulin resistance and type 2 diabetes mellitus (T2DM) that are characterized by metabolic derangement and intracellular stresses (including oxidative stress, inflammation and endoplasmic reticulum stress) also involve the accumulation of damaged cellular components. These conditions are prevalent in ageing populations. For example, sarcopenia is an age-related loss of skeletal muscle mass and strength that is involved in the pathogenesis of both insulin resistance and T2DM, particularly in elderly people. Impairment of autophagy results in further aggravation of diabetes-related metabolic derangements in insulin target tissues, including the liver, skeletal muscle and adipose tissue, as well as in pancreatic β-cells. This Review summarizes the role of autophagy in the pathogenesis of metabolic diseases associated with or occurring in the context of ageing, including insulin resistance, T2DM and sarcopenic obesity, and describes its potential as a therapeutic target.

Involvement of Autophagy in Ageing and Chronic Cholestatic Diseases

Autophagy is a “housekeeping” lysosomal degradation process involved in numerous physiological and pathological processes in all eukaryotic cells. The dysregulation of hepatic autophagy has been described in several conditions, from obesity to diabetes and cholestatic disease. We review the role of autophagy, focusing on age-related cholestatic diseases, and discuss its therapeutic potential and the molecular targets identified to date. The accumulation of toxic BAs is the main cause of cell damage in cholestasis patients. BAs and their receptor, FXR, have been implicated in the regulation of hepatic autophagy. The mechanisms by which cholestasis induces liver damage include mitochondrial dysfunction, oxidative stress and ER stress, which lead to cell death and ultimately to liver fibrosis as a compensatory mechanism to reduce the damage. The stimulation of autophagy seems to ameliorate the liver damage. Autophagic activity decreases with age in several species, whereas its basic extends lifespan in animals, suggesting that it is one of the convergent mechanisms of several longevity pathways. No strategies aimed at inducing autophagy have yet been tested in cholestasis patients. However, its stimulation can be viewed as a novel therapeutic strategy that may reduce ageing-dependent liver deterioration and also mitigate hepatic steatosis.

Increased mitochondrial calcium uptake and concomitant mitochondrial activity by presenilin loss promotes mTORC1 signaling to drive neurodegeneration

Metabolic dysfunction and protein aggregation are common characteristics that occur in age‐related neurodegenerative disease. However, the mechanisms underlying these abnormalities remain poorly understood. We have found that mutations in the gene encoding presenilin in Caenorhabditis elegans, sel‐12, results in elevated mitochondrial activity that drives oxidative stress and neuronal dysfunction. Mutations in the human presenilin genes are the primary cause of familial Alzheimer's disease. Here, we demonstrate that loss of SEL‐12/presenilin results in the hyperactivation of the mTORC1 pathway. This hyperactivation is caused by elevated mitochondrial calcium influx and, likely, the associated increase in mitochondrial activity. Reducing mTORC1 activity improves proteostasis defects and neurodegenerative phenotypes associated with loss of SEL‐12 function. Consistent with high mTORC1 activity, we find that SEL‐12 loss reduces autophagosome formation, and this reduction is prevented by limiting mitochondrial calcium uptake. Moreover, the improvements of proteostasis and neuronal defects in sel‐12 mutants due to mTORC1 inhibition require the induction of autophagy. These results indicate that mTORC1 hyperactivation exacerbates the defects in proteostasis and neuronal function in sel‐12 mutants and demonstrate a critical role of presenilin in promoting neuronal health.

Einstein-Nathan Shock Center: translating the hallmarks of aging to extend human health span

The overarching mission of the Einstein-Nathan Shock Center (E-NSC) is to make scientific discoveries in geroscience, leveraging on the expertise in our center in 6 out of the 7 pillars of aging, and to translate their effects towards drug discovery. The relevance of this basic biology of aging discoveries to humans will be confirmed through the unique gero-human resource at E-NSC. This is achieved through services provided by E-NSC, connectivity among its members, attracting worldwide investigators, and providing them with the opportunities to become future leaders. The two central components of the E-NSC are (a) cutting-edge research programs and (b) unique E-NSC research support cores. E-NSC scientists lead NIH-supported cutting-edge research programs that integrate key hallmarks of aging including proteostasis/autophagy, metabolism/inflammaging, genetic/epigenetics, stem cells/regeneration, and translational aging/longevity. Since the inception of the E-NSC, the well-integrated, collaborative, and innovative nature of the multiple supporting state-of-the-art E-NSC research cores form the bedrock of research success at the E-NSC. The three state-of-the-art E-NSC research cores, (i) Proteostasis of Aging Core (PAC), (ii) the Health Span Core (HSC), and (iii) the Human Multi-Omics Core (HMOC), have allowed impressive expansion of translational biological research programs. Expansion was facilitated through the wealth of data coming from genomics/proteomics and metabolomic analysis on human longevity studies, due to access to a variety of biological samples from elderly subjects in clinical trials with aging-targeting drugs, and new drug design services via the PAC to target the hallmarks of aging.

The Multifaceted Role of Nutrient Sensing and mTORC1 Signaling in Physiology and Aging

The mechanistic Target of Rapamycin (mTOR) is a growth-related kinase that, in the context of the mTOR complex 1 (mTORC1), touches upon most fundamental cellular processes. Consequently, its activity is a critical determinant for cellular and organismal physiology, while its dysregulation is commonly linked to human aging and age-related disease. Presumably the most important stimulus that regulates mTORC1 activity is nutrient sufficiency, whereby amino acids play a predominant role. In fact, mTORC1 functions as a molecular sensor for amino acids, linking the cellular demand to the nutritional supply. Notably, dietary restriction (DR), a nutritional regimen that has been shown to extend lifespan and improve healthspan in a broad spectrum of organisms, works via limiting nutrient uptake and changes in mTORC1 activity. Furthermore, pharmacological inhibition of mTORC1, using rapamycin or its analogs (rapalogs), can mimic the pro-longevity effects of DR. Conversely, nutritional amino acid overload has been tightly linked to aging and diseases, such as cancer, type 2 diabetes and obesity. Similar effects can also be recapitulated by mutations in upstream mTORC1 regulators, thus establishing a tight connection between mTORC1 signaling and aging. Although the role of growth factor signaling upstream of mTORC1 in aging has been investigated extensively, the involvement of signaling components participating in the nutrient sensing branch is less well understood. In this review, we provide a comprehensive overview of the molecular and cellular mechanisms that signal nutrient availability to mTORC1, and summarize the role that nutrients, nutrient sensors, and other components of the nutrient sensing machinery play in cellular and organismal aging.

Autophagy in healthy aging and disease

Autophagy is a fundamental cellular process that eliminates molecules and subcellular elements, including nucleic acids, proteins, lipids and organelles, via lysosome-mediated degradation to promote homeostasis, differentiation, development and survival. While autophagy is intimately linked to health, the intricate relationship among autophagy, aging and disease remains unclear. This Review examines several emerging features of autophagy and postulates how they may be linked to aging as well as to the development and progression of disease. In addition, we discuss current preclinical evidence arguing for the use of autophagy modulators as suppressors of age-related pathologies such as neurodegenerative diseases. Finally, we highlight key questions and propose novel research avenues that will likely reveal new links between autophagy and the hallmarks of aging. Understanding the precise interplay between autophagy and the risk of age-related pathologies across organisms will eventually facilitate the development of clinical applications that promote long-term health.

The intracellular metabolome of starving cells

Fasting induces vast metabolic adaptations on the cellular level and leads to an organism-wide induction of autophagy. Autophagic degradation subserves resource recycling and facilitates the maintenance of energetic homeostasis. Mass spectrometry offers the possibility to assess changes in the metabolome that occur in conditions of nutrient deprivation and to profile such adaptations. Here we describe a detailed workflow for the targeted quantitation and untargeted profiling of metabolites that can be used to assess the intracellular metabolome of starving cells. Moreover, we outline a workflow for the use of non-radioactive isotope labeled metabolites. Altogether, we show that mass spectrometry is a powerful tool for monitoring metabolic changes in conditions of fasting.

Stress and ageing in yeast

There has long been speculation about the role of various stresses in ageing. Some stresses have beneficial effects on ageing-dependent on duration and severity of the stress, others have negative effects and the question arises whether these negative effects are causative of ageing or the result of the ageing process. Cellular responses to many stresses are highly coordinated in a concerted way and hence there is a great deal of cross-talk between different stresses. Here the relevant aspects of the coordination of stress responses and the roles of different stresses on yeast cell ageing are discussed, together with the various functions that are involved. The cellular processes that are involved in alleviating the effects of stress on ageing are considered, together with the possible role of early stress events on subsequent ageing of cells.

Drug discovery: Insights from the invertebrate Caenorhabditis elegans

Therapeutic drug development is a long, expensive, and complex process that usually takes 12-15 years. In the early phases of drug discovery, in particular, there is a growing need for animal models that ensure the reduction in both cost and time. Caenorhabditis elegans has been traditionally used to address fundamental aspects of key biological processes, such as apoptosis, aging, and gene expression regulation. During the last decade, with the advent of large-scale platforms for screenings, this invertebrate has also emerged as an essential tool in the pharmaceutical research industry to identify novel drugs and drug targets. In this review, we discuss the reasons why C. elegans has been positioned as an outstanding cost-effective option for drug discovery, highlighting both the advantages and drawbacks of this model. Particular attention is paid to the suitability of this nematode in large-scale genetic and pharmacological screenings. High-throughput screenings in C. elegans have indeed contributed to the breakthrough of a wide variety of candidate compounds involved in extensive fields including neurodegeneration, pathogen infections and metabolic disorders. The versatility of this nematode, which enables its instrumentation as a model of human diseases, is another attribute also herein underscored. As illustrative examples, we discuss the utility of C. elegans models of both human neurodegenerative diseases and parasitic nematodes in the drug discovery industry. Summing up, this review aims to demonstrate the impact of C. elegans models on the drug discovery pipeline.

Autophagy and senescence: Insights from normal and cancer stem cells

Autophagy is a fundamental cellular process, which allows cells to adapt to metabolic stress through the degradation and recycling of intracellular components to generate macromolecular precursors and produce energy. Autophagy is also critical in maintaining cellular/tissue homeostasis, as well preserving immunity and preventing human disease. Deregulation of autophagic processes is associated with cancer, neurodegeneration, muscle and heart disease, infectious diseases and aging. Research on a variety of stem cell types establish that autophagy plays critical roles in normal and cancer stem cell quiescence, activation, differentiation, and self-renewal. Considering its critical function in regulating the metabolic state of stem cells, autophagy plays a dual role in the regulation of normal and cancer stem cell senescence, and cellular responses to various therapeutic strategies. The relationships between autophagy, senescence, dormancy and apoptosis frequently focus on responses to various forms of stress. These are interrelated processes that profoundly affect normal and abnormal human physiology that require further elucidation in cancer stem cells. This review provides a current perspective on autophagy and senescence in both normal and cancer stem cells.

Mechanism of the lifespan extension induced by submaximal SERCA inhibition in C. elegans

We have reported recently that submaximal inhibition of the Sarco Endoplasmic Reticulum Ca²⁺ ATPase (SERCA) produces an increase in the lifespan of C. elegans worms. We have explored here the mechanism of this increased survival by studying the effect of SERCA inhibition in several mutants of signaling pathways related to longevity. Our data show that the mechanism of the effect is unrelated with the insulin signaling pathway or the sirtuin activity, because SERCA inhibitors increased lifespan similarly in mutants of these pathways. However, the effect required functional mitochondria and both the AMP kinase and TOR pathways, as the SERCA inhibitors were ineffective in the corresponding mutants. The same effects were obtained after reducing SERCA expression with submaximal RNAi treatment. The SERCA inhibitors did not induce ER-stress at the concentrations used, and their effect was not modified by inactivation of the OP50 bacterial food. Altogether, our data suggest that the effect may be due to a reduced ER-mitochondria Ca²⁺ transfer acting via AMPK activation and mTOR inhibition to promote survival.

Molecular Basis of Neuronal Autophagy in Ageing: Insights from Caenorhabditis elegans

Autophagy is an evolutionarily conserved degradation process maintaining cell homeostasis. Induction of autophagy is triggered as a response to a broad range of cellular stress conditions, such as nutrient deprivation, protein aggregation, organelle damage and pathogen invasion. Macroautophagy involves the sequestration of cytoplasmic contents in a double-membrane organelle referred to as the autophagosome with subsequent degradation of its contents upon delivery to lysosomes. Autophagy plays critical roles in development, maintenance and survival of distinct cell populations including neurons. Consequently, age-dependent decline in autophagy predisposes animals for age-related diseases including neurodegeneration and compromises healthspan and longevity. In this review, we summarize recent advances in our understanding of the role of neuronal autophagy in ageing, focusing on studies in the nematode Caenorhabditis elegans.

Genetic characteristics of Bursaphelenchus xylophilus third-stage dispersal juveniles

The third-stage dispersal juvenile (DJ3) of pinewood nematode (PWN) is highly associated with low-temperature survival and spread of the nematode. Oil-Red-O staining showed that its lipid content was significantly higher compared with other PWN stages. Weighted gene coexpression network analysis identified that genes in the pink module were highly related to DJ3 induced in the laboratory (DJ3-lab). These genes were arranged according to their gene significance (GS) to DJ3-lab. Of the top 30 genes with the highest GS, seven were found to be highly homologous to the cysteine protease family cathepsin 1 (CATH1). The top 30 genes with the highest weight value to each of the seven genes in the pink module were selected, and finally 35 genes were obtained. Between these seven CATH1 homologous genes and their 35 highly related genes, 15 were related to fat metabolism or autophagy. These autophagy-related genes were also found to be highly correlated with other genes in the pink module, suggesting that autophagy might be involved in the mechanism of longevity in DJ3 and the formation of DJ3 by regulating genes related to fat metabolism.

High throughput screening for autophagy

Robotized high throughput screening allows for the assessment of autophagy in a large number of samples. Here, we describe a drug discovery platform for the phenotypic identification of novel autophagy inducers by means of automated cell biology workflows employing robotized cell culture, sample preparation and data acquisition. In this setting, fluorescent biosensor cells that express microtubule-associated proteins 1A/1B light chain 3B (best known as LC3) conjugated to green fluorescent protein (GFP), are utilized together with automated high content microscopy for the image-based assessment of autophagy. In sum, we detail a drug discovery screening workflow from high throughput sample preparation and processing to data acquisition and analysis.

The aging proteostasis decline: From nematode to human

The aging proteostasis decline manifests in a failure of aging cells and organisms to properly respond to proteotoxic challenges. This proteostasis collapse has long been considered a hallmark of aging in nematodes, and has recently been shown to occur also in human cells upon entry to senescence, opening the way to exploring the phenomenon in the broader context of human aging. Cellular senescence is part of the normal human physiology of aging, with senescent cell accumulation as a prominent feature of aged tissues. Being highly resistant to cell death, senescent cells, as they accumulate, become pro-inflammatory and promote disease. Here we discuss the causes of human senescence proteostasis decline, in view of the current literature on nematodes, on the one hand, and senescence, on the other hand. We review two major aspects of the phenomenon: (1) the decline in transcriptional activation of stress-response pathways, and (2) impairments in proteasome function. We further outline potential underlying mechanisms of transcriptional proteostasis decline, focusing on reduced chromatin dynamics and compromised nuclear integrity. Finally, we discuss potential strategies for reinforcing proteostasis as a means to improve organismal health and address the relationship to senolytics.

Build-UPS and break-downs: metabolism impacts on proteostasis and aging

Perturbation of metabolism elicits cellular stress which profoundly modulates the cellular proteome and thus protein homeostasis (proteostasis). Consequently, changes in the cellular proteome due to metabolic shift require adaptive mechanisms by molecular protein quality control. The mechanisms vitally controlling proteostasis embrace the entire life cycle of a protein involving translational control at the ribosome, chaperone-assisted native folding, and subcellular sorting as well as proteolysis by the proteasome or autophagy. While metabolic imbalance and proteostasis decline have been recognized as hallmarks of aging and age-associated diseases, both processes are largely considered independently. Here, we delineate how proteome stability is governed by insulin/IGF1 signaling (IIS), mechanistic target of Rapamycin (TOR), 5′ adenosine monophosphate-activated protein kinase (AMPK), and NAD-dependent deacetylases (Sir2-like proteins known as sirtuins). This comprehensive overview is emphasizing the regulatory interconnection between central metabolic pathways and proteostasis, indicating the relevance of shared signaling nodes as targets for future therapeutic interventions.

A Critical Review of the Evidence That Metformin Is a Putative Anti-Aging Drug That Enhances Healthspan and Extends Lifespan

The numerous beneficial health outcomes associated with the use of metformin to treat patients with type 2 diabetes (T2DM), together with data from pre-clinical studies in animals including the nematode, C. elegans, and mice have prompted investigations into whether metformin has therapeutic utility as an anti-aging drug that may also extend lifespan. Indeed, clinical trials, including the MILES (Metformin In Longevity Study) and TAME (Targeting Aging with Metformin), have been designed to assess the potential benefits of metformin as an anti-aging drug. Preliminary analysis of results from MILES indicate that metformin may induce anti-aging transcriptional changes; however it remains controversial as to whether metformin is protective in those subjects free of disease. Furthermore, despite clinical use for over 60 years as an anti-diabetic drug, the cellular mechanisms by which metformin exerts either its actions remain unclear. In this review, we have critically evaluated the literature that has investigated the effects of metformin on aging, healthspan and lifespan in humans as well as other species. In preparing this review, particular attention has been placed on the strength and reproducibility of data and quality of the study protocols with respect to the pharmacokinetic and pharmacodynamic properties of metformin. We conclude that despite data in support of anti-aging benefits, the evidence that metformin increases lifespan remains controversial. However, via its ability to reduce early mortality associated with various diseases, including diabetes, cardiovascular disease, cognitive decline and cancer, metformin can improve healthspan thereby extending the period of life spent in good health. Based on the available evidence we conclude that the beneficial effects of metformin on aging and healthspan are primarily indirect via its effects on cellular metabolism and result from its anti-hyperglycemic action, enhancing insulin sensitivity, reduction of oxidative stress and protective effects on the endothelium and vascular function.

Guidelines for the use and interpretation of assays for monitoring autophagy (4th edition)1

In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this topic has received increasing attention, and many scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular basis updated guidelines for monitoring autophagy in different organisms. Despite numerous reviews, there continues to be confusion regarding acceptable methods to evaluate autophagy, especially in multicellular eukaryotes. Here, we present a set of guidelines for investigators to select and interpret methods to examine autophagy and related processes, and for reviewers to provide realistic and reasonable critiques of reports that are focused on these processes. These guidelines are not meant to be a dogmatic set of rules, because the appropriateness of any assay largely depends on the question being asked and the system being used. Moreover, no individual assay is perfect for every situation, calling for the use of multiple techniques to properly monitor autophagy in each experimental setting. Finally, several core components of the autophagy machinery have been implicated in distinct autophagic processes (canonical and noncanonical autophagy), implying that genetic approaches to block autophagy should rely on targeting two or more autophagy-related genes that ideally participate in distinct steps of the pathway. Along similar lines, because multiple proteins involved in autophagy also regulate other cellular pathways including apoptosis, not all of them can be used as a specific marker for bona fide autophagic responses. Here, we critically discuss current methods of assessing autophagy and the information they can, or cannot, provide. Our ultimate goal is to encourage intellectual and technical innovation in the field.

Identification of putative calorie restriction mimetics using mammalian gene expression profiles

Obesity is a risk factor for cardiovascular diseases, diabetes and cancer. In theory, the obesity problem could be solved by the adherence to a calorie-restricted diet, but that is not generally achieved in practice. An alternative is a pharmacological approach, using compounds that trigger the same metabolic changes associated with calorie restriction. Here, I expand in the pharmacological direction by identifying compounds that induce liver gene signature profiles that mimic those induced by calorie restriction. Using gene expression profiles from mice and rat, I identify corticosteroids, PPAR agonists and some antibacterial/antifungal as candidate compounds mimicking the response to calorie restriction in the liver gene signatures.

Differential Effects of Rapamycin and Metformin in Combination With Rapamycin on Mechanisms of Proteostasis in Cultured Skeletal Myotubes

mTOR inhibition extends life span in multiple organisms. In mice, when metformin treatment (Met) is added to the mTOR inhibitor rapamycin (Rap), median and maximal life span is extended to a greater degree than with Rap or Met alone. Treatments that extend life span often maintain proteostasis. However, it is less clear how individual tissues, such as skeletal muscle, maintain proteostasis with life span-extending treatments. In C2C12 myotubes, we used deuterium oxide (D2O) to directly measure two primary determinants of proteostasis, protein synthesis, and degradation rates, with Rap or Met+Rap treatments. We accounted for the independent effects of cell growth and loss, and isolated the contribution of autophagy and mitochondrial fission to obtain a comprehensive assessment of protein turnover. Compared with control, both Rap and Met+Rap treatments lowered mitochondrial protein synthesis rates (p < .001) and slowed cellular proliferation (p < .01). These changes resulted in greater activation of mechanisms promoting proteostasis for Rap, but not Met+Rap. Compared with control, both Rap and Met+Rap slowed protein breakdown. Autophagy and mitochondrial fission differentially influenced the proteostatic effects of Rap and Met+Rap in C2C12 myotubes. In conclusion, we demonstrate that Met+Rap did not increase protein turnover and that these treatments do not seem to promote proteostasis through increased autophagy.

Stimulation of Hair Growth by Small Molecules that Activate Autophagy

Hair plays important roles, ranging from the conservation of body heat to the preservation of psychological well-being. Hair loss or alopecia affects millions worldwide, but methods that can be used to regrow hair are lacking. We report that quiescent (telogen) hair follicles can be stimulated to initiate anagen and hair growth by small molecules that activate autophagy, including the metabolites α-ketoglutarate (α-KG) and α-ketobutyrate (α-KB), and the prescription drugs rapamycin and metformin, which impinge on mTOR and AMPK signaling. Stimulation of hair growth by these agents is blocked by specific autophagy inhibitors, suggesting a mechanistic link between autophagy and hair regeneration. Consistently, increased autophagy is detected upon anagen entry during the natural hair follicle cycle, and oral α-KB prevents hair loss in aged mice. Our finding that anagen can be pharmacologically activated in telogen skin when natural anagen-inducing signal(s) are absent has implications for the treatment of hair loss patients.

Lysosomes, Autophagy, and Hormesis in Cell Physiology, Pathology, and Age-Related Disease

Autophagy has been strongly linked with hormesis, however, it is only relatively recently that the mechanistic basis underlying this association has begun to emerge. Lysosomal autophagy is a group of processes that degrade proteins, protein aggregates, membranes, organelles, segregated regions of cytoplasm, and even parts of the nucleus in eukaryotic cells. These degradative processes are evolutionarily very ancient and provide a survival capability for cells that are stressed or injured. Autophagy and autophagic dysfunction have been linked with many aspects of cell physiology and pathology in disease processes; and there is now intense interest in identifying various therapeutic strategies involving its regulation. The main regulatory pathway for augmented autophagy is the mechanistic target of rapamycin (mTOR) cell signaling, although other pathways can be involved, such as 5'-adenosine monophosphate-activated protein kinase. Mechanistic target of rapamycin is a key player in the many highly interconnected intracellular signaling pathways and is responsible for the control of cell growth among other processes. Inhibition of mTOR (specifically dephosphorylation of mTOR complex 1) triggers augmented autophagy and the search is on the find inhibitors that can induce hormetic responses that may be suitable for treating many diseases, including many cancers, type 2 diabetes, and age-related neurodegenerative conditions.

Essential Physiological Differences Characterize Short- and Long-Lived Strains of Drosophila melanogaster

Aging is a multifactorial process which affects all animals. Aging as a result of damage accumulation is the most accepted explanation but the proximal causes remain to be elucidated. There is also evidence indicating that aging has an important genetic component. Animal species age at different rates and specific signaling pathways, such as insulin/insulin-like growth factor, can regulate life span of individuals within a species by reprogramming cells in response to environmental changes. Here, we use an unbiased approach to identify novel factors that regulate life span in Drosophila melanogaster. We compare the transcriptome and metabolome of two wild-type strains used widely in aging research: short-lived Dahomey and long-lived Oregon R flies. We found that Dahomey flies carry several traits associated with short-lived individuals and species such as increased lipoxidative stress, decreased mitochondrial gene expression, and increased Target of Rapamycin signaling. Dahomey flies also have upregulated octopamine signaling known to stimulate foraging behavior. Accordingly, we present evidence that increased foraging behavior, under laboratory conditions where nutrients are in excess increases damage generation and accelerates aging. In summary, we have identified several new pathways, which influence longevity highlighting the contribution and importance of the genetic component of aging.

C. elegans to model autophagy-related human disorders

Autophagy is a highly conserved degradation process that clears damaged intracellular macromolecules and organelles in order to maintain cellular health. Dysfunctional autophagy is fundamentally linked to the development of various human disorders and pathologies. The use of the nematode Caenorhabditis elegans as a model system to study autophagy has improved our understanding of its regulation and function in organismal physiology. Here, we review the genetic, functional, and regulatory conservation of the autophagy pathway in C. elegans and we describe tools to quantify and study the autophagy process in this incredibly useful model organism. We further discuss how these nematodes have been modified to model autophagy-related human diseases and underscore the important insights obtained from such models. Altogether, we highlight the strengths of C. elegans as an exceptional tool to understand the genetic and molecular foundations underlying autophagy-related human diseases.

Temporal inhibition of autophagy reveals segmental reversal of ageing with increased cancer risk

Autophagy is an important cellular degradation pathway with a central role in metabolism as well as basic quality control, two processes inextricably linked to ageing. A decrease in autophagy is associated with increasing age, yet it is unknown if this is causal in the ageing process, and whether autophagy restoration can counteract these ageing effects. Here we demonstrate that systemic autophagy inhibition induces the premature acquisition of age-associated phenotypes and pathologies in mammals. Remarkably, autophagy restoration provides a near complete recovery of morbidity and a significant extension of lifespan; however, at the molecular level this rescue appears incomplete. Importantly autophagy-restored mice still succumb earlier due to an increase in spontaneous tumour formation. Thus, our data suggest that chronic autophagy inhibition confers an irreversible increase in cancer risk and uncovers a biphasic role of autophagy in cancer development being both tumour suppressive and oncogenic, sequentially.

Caloric restriction rescues yeast cells from alpha-synuclein toxicity through autophagic control of proteostasis

α-Synuclein (SNCA) is a presynaptic protein that is associated with the pathophysiology of synucleinopathies, including Parkinson's disease. SNCA is a naturally aggregation-prone protein, which may be degraded by the ubiquitin-proteasome system (UPS) and by lysosomal degradation pathways. Besides being a target of the proteolytic systems, SNCA can also alter the function of these pathways further, contributing to the progression of neurodegeneration. Deterioration of UPS and autophagy activities with aging further aggravates this toxic cycle. Caloric restriction (CR) is still the most effective non-genetic intervention promoting lifespan extension. It is known that CR-mediated lifespan extension is linked to the regulation of proteolytic systems, but the mechanisms underlying CR rescue of SNCA toxicity remain poorly understood. This study shows that CR balances UPS and autophagy activities during aging. CR enhances UPS activity, reversing the decline of the UPS activity promoted by SNCA, and keeps autophagy at homeostatic levels. Maintenance of autophagy at homeostatic levels appears to be relevant for UPS activity and for the mechanism underlying rescue of cells from SNCA-mediated toxicity by CR.