Age-dependent changes in mitochondrial morphology and volume are not predictors of lifespan

Mitochondrial Proteome Reveals Metabolic Tuning by Restricted Insulin Signaling to Promote Longevity in Caenorhabditis elegans

Aging is a time-dependent process of functional decline influenced by genetic and environmental factors. Age-related mitochondrial changes remain incompletely understood. Here, we found that compared to the wild type, the mitochondria of long-lived daf-2 C. elegans maintain youthful morphology and function. Through quantitative proteomic analysis on isolated mitochondria, we identified 257 differentially expressed candidates. Analysis of these changed mitochondrial proteins reveals a significant upregulation of five key mitochondrial metabolic pathways in daf-2 mutants, including branched-chain amino acids (BCAA), reactive oxygen species (ROS), propionate, β-alanine, and fatty acids (FA), all of which are related to daf-2-mediated longevity. In addition, mitochondrial ribosome protein abundance slightly decreased in daf-2 mutants. A mild reduction in mitochondrial elongation factor G (gfm-1) by RNAi extends the lifespan of wild type while decreasing lipid metabolic process and cytoplasmic fatty acid metabolism, suggesting that proper inhibition of mitochondrial translation activity might be important for lifespan extension. Overall, our findings indicate that mitochondrial metabolic modulation contributes to the longevity of daf-2 mutants and further highlights the crucial role of mitochondria in aging.

Impact of ageing and disuse on neuromuscular junction and mitochondrial function and morphology: Current evidence and controversies

Inactivity and ageing can have a detrimental impact on skeletal muscle and the neuromuscular junction (NMJ). Decreased physical activity results in muscle atrophy, impaired mitochondrial function, and NMJ instability. Ageing is associated with a progressive decrease in muscle mass, deterioration of mitochondrial function in the motor axon terminals and in myofibres, NMJ instability and loss of motor units. Focusing on the impact of inactivity and ageing, this review examines the consequences on NMJ stability and the role of mitochondrial dysfunction, delving into their complex relationship with ageing and disuse. Evidence suggests that mitochondrial dysfunction can be a pathogenic driver for NMJ alterations, with studies revealing the role of mitochondrial defects in motor neuron degeneration and NMJ instability. Two perspectives behind NMJ instability are discussed: one is that mitochondrial dysfunction in skeletal muscle triggers NMJ deterioration, the other envisages dysfunction of motor terminal mitochondria as a primary contributor to NMJ instability. While evidence from these studies supports both perspectives on the relationship between NMJ dysfunction and mitochondrial impairment, gaps persist in the understanding of how mitochondrial dysfunction can cause NMJ deterioration. Further research, both in humans and in animal models, is essential for unravelling the mechanisms and potential interventions for age- and inactivity-related neuromuscular and mitochondrial alterations.

AutoMitoNetwork: Software for analyzing mitochondrial networks in autofluorescence images to enable label-free cell classification

High-resolution mitochondria imaging in combination with image analysis tools have significantly advanced our understanding of cellular function in health and disease. However, most image analysis tools for mitochondrial studies have been designed to work with fluorescently labeled images only. Additionally, efforts to integrate features describing mitochondrial networks with machine learning techniques for the differentiation of cell types have been limited. Herein, we present AutoMitoNetwork software for image-based assessment of mitochondrial networks in label-free autofluorescence images using a range of interpretable morphological, intensity, and textural features. To demonstrate its utility, we characterized unstained mitochondrial networks in healthy retinal cells and in retinal cells exposed to two types of treatments: rotenone, which directly inhibited mitochondrial respiration and ATP production, and iodoacetic acid, which had a milder impact on mitochondrial networks via the inhibition of anaerobic glycolysis. For both cases, our multi-dimensional feature analysis combined with a support vector machine classifier distinguished between healthy cells and those treated with rotenone or iodoacetic acid. Subtle changes in morphological features were measured including increased fragmentation in the treated retinal cells, pointing to an association with metabolic mechanisms. AutoMitoNetwork opens new options for image-based machine learning in label-free imaging, diagnostics, and mitochondrial disease drug development.

The clinical antiprotozoal drug nitazoxanide and its metabolite tizoxanide extend Caenorhabditis elegans lifespan and healthspan

The drugs extending healthspan in clinic have always been searched. Nitazoxanide is an FDA-approved clinical antiprotozoal drug. Nitazoxanide is rapidly metabolized to tizoxanide after absorption in vivo. Our previous studies find that nitazoxanide and its metabolite tizoxanide induce mild mitochondrial uncoupling and activate cellular AMPK, oral nitazoxanide protects against experimental hyperlipidemia, hepatic steatosis, and atherosclerosis. Here, we demonstrate that both nitazoxanide and tizoxanide extend the lifespan and healthspan of Caenorhabditis elegans through Akt/AMPK/sir 2.1/daf16 pathway. Additionally, both nitazoxanide and tizoxanide improve high glucose-induced shortening of C. elegans lifespan. Nitazoxanide has been a clinical drug with a good safety profile, we suggest that it is a novel anti-aging drug.

SIN-3 transcriptional coregulator maintains mitochondrial homeostasis and polyamine flux

Mitochondrial function relies on the coordinated transcription of mitochondrial and nuclear genomes to assemble respiratory chain complexes. Across species, the SIN3 coregulator influences mitochondrial functions, but how its loss impacts mitochondrial homeostasis and metabolism in the context of a whole organism is unknown. Exploring this link is important because SIN3 haploinsufficiency causes intellectual disability/autism syndromes and SIN3 plays a role in tumor biology. Here we show that loss of C. elegans SIN-3 results in transcriptional deregulation of mitochondrial- and nuclear-encoded mitochondrial genes, potentially leading to mito-nuclear imbalance. Consistent with impaired mitochondrial function, sin-3 mutants show extensive mitochondrial fragmentation by transmission electron microscopy (TEM) and in vivo imaging, and altered oxygen consumption. Metabolomic analysis of sin-3 mutant animals revealed a mitochondria stress signature and deregulation of methionine flux, resulting in decreased S-adenosyl methionine (SAM) and increased polyamine levels. Our results identify SIN3 as a key regulator of mitochondrial dynamics and metabolic flux, with important implications for human pathologies.

Aging-induced tRNAGlu-derived fragment impairs glutamate biosynthesis by targeting mitochondrial translation-dependent cristae organization

Mitochondrial cristae, infoldings of the mitochondrial inner membrane, undergo aberrant changes in their architecture with age. However, the underlying molecular mechanisms and their contribution to brain aging are largely elusive. Here, we observe an age-dependent accumulation of Glu-5'tsRNA-CTC, a transfer-RNA-derived small RNA (tsRNA), derived from nuclear-encoded tRNAGlu in the mitochondria of glutaminergic neurons. Mitochondrial Glu-5'tsRNA-CTC disrupts the binding of mt-tRNALeu and leucyl-tRNA synthetase2 (LaRs2), impairing mt-tRNALeu aminoacylation and mitochondria-encoded protein translation. Mitochondrial translation defects disrupt cristae organization, leading to damaged glutaminase (GLS)-dependent glutamate formation and reduced synaptosomal glutamate levels. Moreover, reduction of Glu-5'tsRNA-CTC protects aged brains from age-related defects in mitochondrial cristae organization, glutamate metabolism, synaptic structures, and memory. Thus, beyond illustrating a physiological role for normal mitochondrial cristae ultrastructure in maintaining glutamate levels, our study defines a pathological role for tsRNAs in brain aging and age-related memory decline.

Nutritional approaches targeting mitochondria for the prevention of sarcopenia

A decline in function and loss of mass, a condition known as sarcopenia, is observed in the skeletal muscles with aging. Sarcopenia has a negative effect on the quality of life of elderly. Individuals with sarcopenia are at particular risk for adverse outcomes, such as reduced mobility, fall-related injuries, and type 2 diabetes mellitus. Although the pathogenesis of sarcopenia is multifaceted, mitochondrial dysfunction is regarded as a major contributor for muscle aging. Hence, the development of preventive and therapeutic strategies to improve mitochondrial function during aging is imperative for sarcopenia treatment. However, effective and specific drugs that can be used for the treatment are not yet approved. Instead studies on the relationship between food intake and muscle aging have suggested that nutritional intake or dietary control could be an alternative approach for the amelioration of muscle aging. This narrative review approaches various nutritional components and diets as a treatment for sarcopenia by modulating mitochondrial homeostasis and improving mitochondria. Age-related changes in mitochondrial function and the molecular mechanisms that help improve mitochondrial homeostasis are discussed, and the nutritional components and diet that modulate these molecular mechanisms are addressed.

ORMDL3 regulates NLRP3 inflammasome activation by maintaining ER-mitochondria contacts in human macrophages and dictates ulcerative colitis patient outcome

Genome-wide association studies in inflammatory bowel disease have identified risk loci in the orosomucoid-like protein 3/ORMDL sphingolipid biosynthesis regulator 3 (ORMDL3) gene to confer susceptibility to ulcerative colitis (UC), but the underlying functional relevance remains unexplored. Here, we found that a subpopulation of the UC patients who had higher disease activity shows enhanced expression of ORMDL3 compared to the patients with lower disease activity and the non-UC controls. We also found that the patients showing high ORMDL3 mRNA expression have elevated interleukin-1β cytokine levels indicating positive correlation. Further, knockdown of ORMDL3 in the human monocyte-derived macrophages resulted in significantly reduced interleukin-1β release. Mechanistically, we report for the first time that ORMDL3 contributes to a mounting inflammatory response via modulating mitochondrial morphology and activation of the NLRP3 inflammasome. Specifically, we observed an increased fragmentation of mitochondria and enhanced contacts with the endoplasmic reticulum (ER) during ORMDL3 over-expression, enabling efficient NLRP3 inflammasome activation. We show that ORMDL3 that was previously known to be localized in the ER also becomes localized to mitochondria-associated membranes and mitochondria during inflammatory conditions. Additionally, ORMDL3 interacts with mitochondrial dynamic regulating protein Fis-1 present in the mitochondria-associated membrane. Accordingly, knockdown of ORMDL3 in a dextran sodium sulfate -induced colitis mouse model showed reduced colitis severity. Taken together, we have uncovered a functional role for ORMDL3 in mounting inflammation during UC pathogenesis by modulating ER-mitochondrial contact and dynamics.

The mechanisms and roles of mitochondrial dynamics in C. elegans

If mitochondria are the powerhouses of the cell, then mitochondrial dynamics are the power grid that regulates how that energy output is directed and maintained in response to unique physiological demands. Fission and fusion dynamics are highly regulated processes that fine-tune the mitochondrial networks of cells to enable appropriate responses to intrinsic and extrinsic stimuli, thereby maintaining cellular and organismal homeostasis. These dynamics shape many aspects of an organism's healthspan including development, longevity, stress resistance, immunity, and response to disease. In this review, we discuss the latest findings regarding the mechanisms and roles of mitochondrial dynamics by focussing on the nematode Caenorhabditis elegans. Whole live-animal studies in C. elegans have enabled a true organismal-level understanding of the impact that mitochondrial dynamics play in homeostasis over a lifetime.

Considering Caenorhabditis elegans Aging on a Temporal and Tissue Scale: The Case of Insulin/IGF-1 Signaling

The aging process is inherently complex, involving multiple mechanisms that interact at different biological scales. The nematode Caenorhabditis elegans is a simple model organism that has played a pivotal role in aging research following the discovery of mutations extending lifespan. Longevity pathways identified in C. elegans were subsequently found to be conserved and regulate lifespan in multiple species. These pathways intersect with fundamental hallmarks of aging that include nutrient sensing, epigenetic alterations, proteostasis loss, and mitochondrial dysfunction. Here we summarize recent data obtained in C. elegans highlighting the importance of studying aging at both the tissue and temporal scale. We then focus on the neuromuscular system to illustrate the kinetics of changes that take place with age. We describe recently developed tools that enabled the dissection of the contribution of the insulin/IGF-1 receptor ortholog DAF-2 to the regulation of worm mobility in specific tissues and at different ages. We also discuss guidelines and potential pitfalls in the use of these new tools. We further highlight the opportunities that they present, especially when combined with recent transcriptomic data, to address and resolve the inherent complexity of aging. Understanding how different aging processes interact within and between tissues at different life stages could ultimately suggest potential intervention points for age-related diseases.

Non-Genomic Hallmarks of Aging-The Review

Aging is a natural, gradual, and inevitable process associated with a series of changes at the molecular, cellular, and tissue levels that can lead to an increased risk of many diseases, including cancer. The most significant changes at the genomic level (DNA damage, telomere shortening, epigenetic changes) and non-genomic changes are referred to as hallmarks of aging. The hallmarks of aging and cancer are intertwined. Many studies have focused on genomic hallmarks, but non-genomic hallmarks are also important and may additionally cause genomic damage and increase the expression of genomic hallmarks. Understanding the non-genomic hallmarks of aging and cancer, and how they are intertwined, may lead to the development of approaches that could influence these hallmarks and thus function not only to slow aging but also to prevent cancer. In this review, we focus on non-genomic changes. We discuss cell senescence, disruption of proteostasis, deregualation of nutrient sensing, dysregulation of immune system function, intercellular communication, mitochondrial dysfunction, stem cell exhaustion and dysbiosis.

Mitochonic acid 5 attenuates age-related neuromuscular dysfunction associated with mitochondrial Ca2+ overload in Caenorhabditis elegans

Mitochonic acid-5 ameliorates the pathophysiology of human mitochondrial-disease fibroblasts and Caenorhabditis elegans Duchenne muscular dystrophy and Parkinson's disease models. Here, we found that 10 μM MA-5 attenuates the age-related decline in motor performance, loss of muscle mitochondria, and degeneration of dopaminergic neurons associated with mitochondrial Ca²⁺ overload in C. elegans. These findings suggest that MA-5 may act as an anti-aging agent against a wide range of neuromuscular dysfunctions in metazoans.

Partial inhibition of class III PI3K VPS-34 ameliorates motor aging and prolongs health span

Global increase of life expectancy is rarely accompanied by increased health span, calling for a greater understanding of age-associated behavioral decline. Motor independence is strongly associated with the quality of life of elderly people, yet the regulators for motor aging have not been systematically explored. Here, we designed a fast and efficient genome-wide screening assay in Caenorhabditis elegans and identified 34 consistent genes as potential regulators of motor aging. Among the top hits, we found VPS-34, the class III phosphatidylinositol 3-kinase that phosphorylates phosphatidylinositol (PI) to phosphatidylinositol 3-phosphate (PI(3)P), regulates motor function in aged but not young worms. It primarily functions in aged motor neurons by inhibiting PI(3)P-PI-PI(4)P conversion to reduce neurotransmission at the neuromuscular junction (NMJ). Genetic and pharmacological inhibition of VPS-34 improve neurotransmission and muscle integrity, ameliorating motor aging in both worms and mice. Thus, our genome-wide screening revealed an evolutionarily conserved, actionable target to delay motor aging and prolong health span.

Age-associated anatomical and physiological alterations in Caenorhabditis elegans

Since its introduction by Sydney Brenner, Caenorhabditis elegans has become a widely studied organism. Given its highly significant properties, including transparency, short lifespan, self-fertilization, high reproductive yield and ease in manipulation and genetic modifications, the nematode has contributed to the elucidation of several fundamental aspects of biology, such as development and ageing. Moreover, it has been extensively used as a platform for the modelling of ageing-associated human disorders, especially those related to neurodegeneration. The use of C. elegans for such purposes requires, and at the same time promotes the investigation of its normal ageing process. In this review we aim to summarize the major organismal alterations during normal worm ageing, in terms of morphology and functionality.

Increased mitochondrial Ca2+ contributes to health decline with age and Duchene muscular dystrophy in C. elegans

Sarcopenia is a geriatric syndrome characterized by an age-related decline in skeletal muscle mass and strength. Here, we show that suppression of mitochondrial calcium uniporter (MCU)-mediated Ca2+ influx into mitochondria in the body wall muscles of the nematode Caenorhabditis elegans improved the sarcopenic phenotypes, blunting movement and mitochondrial structural and functional decline with age. We found that normally aged muscle cells exhibited elevated resting mitochondrial Ca2+ levels and increased mitophagy to eliminate damaged mitochondria. Similar to aging muscle, we found that suppressing MCU function in muscular dystrophy improved movement via reducing elevated resting mitochondrial Ca2+ levels. Taken together, our results reveal that elevated resting mitochondrial Ca2+ levels contribute to muscle decline with age and muscular dystrophy. Further, modulation of MCU activity may act as a potential pharmacological target in various conditions involving muscle loss.

Mitochondria dysfunction and impaired response to oxidative stress promotes proteostasis disruption in aged human cells

The plastic architecture of the mitochondrial network and its dynamic structure play crucial roles ensuring that varying energetic demands are rapidly met. Given the brain's high energy demand, mitochondria play a particularly critical role in neuronal and axonal energy homeostasis. With ageing physiological properties of the organism deteriorate, and are associated with loss of cellular homeostasis, accumulation of dysfunctional organelles and damaged macromolecules. Thus, mitochondrial loss of efficiency is likely to be both a cause and a consequence of ageing. Additionally distinct cellular events can contribute to oxidative stress, disruption of metabolism and mitochondria homeostasis, resulting in neuropathology. However, although the correlation between ageing and mitochondria disfunction is well established, the response to oxidative stress, particularly proteostasis, remains to be fully elucidated. The work here described explores the degradation of mitochondria oxidative stress-response mechanisms with ageing in human cells, addressing the physiological effects on proteostasis, focused on its role in differentiating between healthy and pathological ageing. Increased protein aggregation appears to be tightly related to impairment of ageing mitochondria response to oxidative stress, and antioxidative agents are shown to have a progressive protective effect with age; cells from old individuals show higher susceptibility to oxidative stress, in terms of protein aggregation, cell viability, or mitochondria homeostasis. These results support the antioxidant properties of flavonoids as a good therapeutic strategy for age-related diseases. Given their protective effect, this family of compounds can be of strategic therapeutic value for protein-aggregation related diseases.

Exercise preserves physical fitness during aging through AMPK and mitochondrial dynamics

Exercise is a nonpharmacological intervention that improves health during aging and a valuable tool in the diagnostics of aging-related diseases. In muscle, exercise transiently alters mitochondrial functionality and metabolism. Mitochondrial fission and fusion are critical effectors of mitochondrial plasticity, which allows a fine-tuned regulation of organelle connectiveness, size, and function. Here we have investigated the role of mitochondrial dynamics during exercise in the model organism Caenorhabditis elegans. We show that in body-wall muscle, a single exercise session induces a cycle of mitochondrial fragmentation followed by fusion after a recovery period, and that daily exercise sessions delay the mitochondrial fragmentation and physical fitness decline that occur with aging. Maintenance of proper mitochondrial dynamics is essential for physical fitness, its enhancement by exercise training, and exercise-induced remodeling of the proteome. Surprisingly, among the long-lived genotypes we analyzed (isp-1,nuo-6, daf-2, eat-2, and CA-AAK-2), constitutive activation of AMP-activated protein kinase (AMPK) uniquely preserves physical fitness during aging, a benefit that is abolished by impairment of mitochondrial fission or fusion. AMPK is also required for physical fitness to be enhanced by exercise, with our findings together suggesting that exercise may enhance muscle function through AMPK regulation of mitochondrial dynamics. Our results indicate that mitochondrial connectivity and the mitochondrial dynamics cycle are essential for maintaining physical fitness and exercise responsiveness during aging and suggest that AMPK activation may recapitulate some exercise benefits. Targeting mechanisms to optimize mitochondrial fission and fusion, as well as AMPK activation, may represent promising strategies for promoting muscle function during aging.

The innate immune signaling component FBXC-58 mediates dietary restriction effects on healthy aging in Caenorhabditis elegans

Dietary restriction (DR) is a highly effective and reproducible intervention that prolongs longevity in many organisms. The molecular mechanism of action of DR is tightly connected with the immune system; however, the detailed mechanisms and effective downstream factors of immunity that mediate the beneficial effects of DR on aging remain unknown. Here, to investigate the immune signaling that mediates DR effects, we used Caenorhabditis elegans, which has been widely used in research, to understand the underlying molecular mechanisms of aging and immunity. We found that the F-box gene, fbxc-58, a regulator of the innate immune response, is a novel mediator of DR effects on extending the health span of C. elegans. fbxc-58 is upregulated by DR and is necessary for DR-induced lifespan extension and physical health improvement in C. elegans. Furthermore, through DR, fbxc-58 prevents disintegration of the mitochondrial network in body wall muscle during aging. We found that fbxc-58 is a downstream target of the ZIP-2 and PHA-4 transcription factors, the well-known DR mediator, and fbxc-58 extends longevity in DR through an S6 kinase-dependent pathway. We propose that the novel DR effector, fbxc-58, could provide a new mechanistic understanding of the effects of DR on healthy aging and elucidate the signaling mechanisms that link immunity and DR effects with aging.

Anti-aging effects of dietary phytochemicals: From Caenorhabditis elegans, Drosophila melanogaster, rodents to clinical studies

Anti-aging research has become critical since the elderly population is increasing dramatically in this era. With the establishment of frailty phenotype and frailty index, the importance of anti-frailty research is concurrently enlightened. The application of natural phytochemicals against aging or frailty is always intriguing, and abundant related studies have been published. Various models are designed for biological research, and each model has its strength and weakness in deciphering the complex aging mechanisms. In this article, we attempt to show the potential of Caenorhabditis elegans in the study of phytochemicals' effects on anti-aging by comparing it to other animal models. In this review, the lifespan extension and anti-aging effects are demonstrated by various physical, cellular, or molecular biomarkers of dietary phytochemicals, including resveratrol, curcumin, urolithin A, sesamin, fisetin, quercetin, epigallocatechin-3-gallate, epicatechin, spermidine, sulforaphane, along with extracts of broccoli, cocoa, and blueberry. Meanwhile, the frequency of phytochemicals and models studied or presented in publications since 2010 were analyzed, and the most commonly mentioned animal models were rats, mice, and the nematode C. elegans. This up-to-date summary of the anti-aging effect of certain phytochemicals has demonstrated powerful potential for anti-aging or anti-frailty in the human population.

Ageing, Metabolic Dysfunction, and the Therapeutic Role of Antioxidants

The gradual ageing of the world population has been accompanied by a dramatic increase in the prevalence of obesity and metabolic diseases, especially type 2 diabetes. The adipose tissue dysfunction associated with ageing and obesity shares many common physiological features, including increased oxidative stress and inflammation. Understanding the mechanisms responsible for adipose tissue dysfunction in obesity may help elucidate the processes that contribute to the metabolic disturbances that occur with ageing. This, in turn, may help identify therapeutic targets for the treatment of obesity and age-related metabolic disorders. Because oxidative stress plays a critical role in these pathological processes, antioxidant dietary interventions could be of therapeutic value for the prevention and/or treatment of age-related diseases and obesity and their complications. In this chapter, we review the molecular and cellular mechanisms by which obesity predisposes individuals to accelerated ageing. Additionally, we critically review the potential of antioxidant dietary interventions to counteract obesity and ageing.

Regulation of aging by balancing mitochondrial function and antioxidant levels

Aging is the deterioration of physiological mechanisms that is associated with getting old. There is a link between aging and mitochondrial function. However, there is an unresolved relationship between ATP levels and aging. To address this issue, we administered febuxostat (FBX), an inhibitor of human xanthine oxidase (XO)/xanthine dehydrogenase (XDH), to C. elegans. We used C. elegans as a model to evaluate the effects of FBX and to challenge the enigma of the relationship between ATP and lifespan. In this study, we showed that FBX protects mitochondria and prevents age-related muscle deterioration in C. elegans. In addition, we showed that FBX administration could increase ATP levels without overloading the mitochondria while extending the lifespan. We also showed that the combination of FBX and an antioxidant as a protection against ROS prolongs lifespan more. We have shown that the antioxidant effects and increased ATP levels may lead to antiaging effects.

Oocyte mitophagy is critical for extended reproductive longevity

Women's reproductive cessation is the earliest sign of human aging and is caused by decreasing oocyte quality. Similarly, C. elegans' reproduction declines in mid-adulthood and is caused by oocyte quality decline. Aberrant mitochondrial morphology is a hallmark of age-related dysfunction, but the role of mitochondrial morphology and dynamics in reproductive aging is unclear. We examined the requirements for mitochondrial fusion and fission in oocytes of both wild-type worms and the long-lived, long-reproducing insulin-like receptor mutant daf-2. We find that normal reproduction requires both fusion and fission, but that daf-2 mutants utilize a shift towards fission, but not fusion, to extend their reproductive span and oocyte health. daf-2 mutant oocytes' mitochondria are punctate (fissioned) and this morphology is primed for mitophagy, as loss of the mitophagy regulator PINK-1 shortens daf-2's reproductive span. daf-2 mutants maintain oocyte mitochondria quality with age at least in part through a shift toward punctate mitochondrial morphology and subsequent mitophagy. Supporting this model, Urolithin A, a metabolite that promotes mitophagy, extends reproductive span in wild-type mothers-even in mid-reproduction-by maintaining youthful oocytes with age. Our data suggest that promotion of mitophagy may be an effective strategy to maintain oocyte health with age.

Lacticaseibacillus casei CNCM I-5663 supplementation maintained muscle mass in a model of frail rodents

The aim of this study was to identify a probiotic-based strategy for maintaining muscle anabolism in the elderly. In previous research, we found that individuals experiencing short bowel syndrome (SBS) after an intestinal resection displayed beneficial metabolic adjustments that were mediated by their gut microbes. Thus, these bacteria could potentially be used to elicit similar positive effects in elderly people, who often have low food intake and thus develop sarcopenia. Gut bacterial strains from an SBS patient were evaluated for their ability to (1) maintain Caenorhabditis elegans survival and muscle structure and (2) promote protein anabolism in a model of frail rodents (18-month-old rats on a food-restricted diet: 75% of ad libitum consumption). We screened a first set of bacteria in C. elegans and selected two Lacticaseibacillus casei strains (62 and 63) for further testing in the rat model. We had four experimental groups: control rats on an ad libitum diet (AL); non-supplemented rats on the food-restricted diet (R); and two sets of food-restricted rats that received a daily supplement of one of the strains (∼10⁹ CFU; R+62 and R+63). We measured lean mass, protein metabolism, insulin resistance, cecal short-chain fatty acids (SCFAs), and SCFA receptor expression in the gut. Food restriction led to decreased muscle mass [-10% vs. AL (p < 0.05)]. Supplementation with strain 63 tempered this effect [-2% vs. AL (p > 0.1)]. The mechanism appeared to be the stimulation of the insulin-sensitive p-S6/S6 and p-eIF2α/eIF2α ratios, which were similar in the R+63 and AL groups (p > 0.1) but lower in the R group (p < 0.05). We hypothesize that greater SCFA receptor sensitivity in the R+63 group promoted gut-muscle cross talk [GPR41: +40% and GPR43: +47% vs. R (p < 0.05)]. Hence, strain 63 could be used in association with other nutritional strategies and exercise regimes to limit sarcopenia in frail elderly people.

An aco-2::gfp knock-in enables the monitoring of mitochondrial morphology throughout C. elegans lifespan

We used CRISPR/Cas9 gene editing in C. elegans in order to fluorescently tag endogenous aconitase-2 (ACO-2). ACO-2 is a mitochondrially localized protein, and the aco-2::gfp strain enabled the examination of native mitochondrial morphology in live animals. Here we validate that the aco-2::gfp strain displays the prototypic changes in mitochondrial morphology known to occur during aging and upon paraquat (PQ) induced mitochondrial stress. We also provide evidence that the ACO-2::GFP reporter can serve as a superior means for tracking mitochondrial morphology than conventional MitoTracker dyes-especially in aged-worms.

DAF-2/insulin IGF-1 receptor regulates motility during aging by integrating opposite signaling from muscle and neuronal tissues

During aging, preservation of locomotion is generally considered an indicator of sustained good health, in elderlies and in animal models. In Caenorhabditis elegans, mutants of the insulin‐IGF‐1 receptor DAF2/IIRc represent a paradigm of healthy aging, as their increased lifespan is accompanied by a delay in age‐related loss of motility. Here, we investigated the DAF‐2/IIRc‐dependent relationship between longevity and motility using an auxin‐inducible degron to trigger tissue‐specific degradation of endogenous DAF‐2/IIRc. As previously reported, inactivation of DAF‐2/IIRc in neurons or intestine was sufficient to extend the lifespan of worms, whereas depletion in epidermis, germline, or muscle was not. However, neither intestinal nor neuronal depletion of DAF‐2/IIRc prevented the age‐related loss of motility. In 1‐day‐old adults, DAF‐2/IIRc depletion in neurons reduced motility in a DAF‐16/FOXO dependent manner, while muscle depletion had no effect. By contrast, DAF‐2 depletion in the muscle of middle‐age animals improved their motility independently of DAF‐16/FOXO but required UNC‐120/SRF. Yet, neuronal or muscle DAF‐2/IIRc depletion both preserved the mitochondria network in aging muscle. Overall, these results show that the motility pattern of daf‐2 mutants is determined by the sequential and opposing impact of neurons and muscle tissues and can be dissociated from the regulation of the lifespan. This work also provides the characterization of a versatile tool to analyze the tissue‐specific contribution of insulin‐like signaling in integrated phenotypes at the whole organism level.

Potential anti-Parkinsonian's effect of S-(+)-linalool from Cinnamomum osmophloeum ct. linalool leaves are associated with mitochondrial regulation via gas-1, nuo-1, and mev-1 in Caenorhabditis elegans

Parkinson's disease (PD) is one of the prevalent neurodegenerative diseases, and developing new treatments from natural products is of particular interest. Essential oils from Cinnamomum osmophloeum ct. linalool leaves contain high levels (~95%) of S-(+)-linalool. The neuroprotective effects of linalool have been previously described, yet the underlying molecular mechanisms remain largely unknown. This study aimed to investigate the potential anti-Parkinsonian's effect of S-(+)-linalool on mitochondrial regulation and decipher the underlying molecular mechanisms in Caenorhabditis elegans PD model. Essential oils at 20 mg/L and 20 mg/L S-(+)-linalool each significantly attenuated the damaging effects of 6-hydroxydopamine (6-OHDA) on dopaminergic (DA) neurons and decreased the mitochondrial unfolded protein response (UPR^mt ) to antimycin. RNAi knockdown of mitochondrial complex I (gas-1, nuo-1), and complex II (mev-1) genes prevented the improvement of mitochondrial activity by S-(+)-linalool. The protective effects of S-(+)-linalool on 6-OHDA-induced behavior changes were absent in a DA-specific strain of C. elegans produced by gas-1, nuo-1, and mev-1 RNAi knockdown. These results suggest the potential anti-Parkinsonian's effect of S-(+)-linalool is associated with mitochondrial activity and regulated by gas-1, nuo-1, and mev-1 in C. elegans. Our findings suggest that S-(+)-linalool might be a promising candidate for therapeutic application to inhibit the progression of PD.

S-allylcysteine Ameliorates Aging Features Via Regulating Mitochondrial Dynamics in Naturally Aged C57BL/6J Mice

SCOPE

S-allylcysteine (SAC) is the most abundant organosulfur molecule derived from aged garlic. We evaluated the effects of S-allylcysteine (SAC) on improving aging in naturally aged C57BL/6J male mice and mitochondrial dynamics in C. elegans and its underlying mechanisms.

METHODS AND RESULTS

When mice had attained reproductive senescence at 60 weeks of age, SAC was supplemented to 0.05% and 0.2% into their normal diet for 12 weeks The results showed that SAC could significantly improve the level of hepatic OPA1 mRNA, which is a key factor for mitochondrial fusion, and consequently elevated the mitochondrial biogenesis-related proteins SIRT1 and PGC-1α, thus ameliorating oxidative stress, such as MDA in the liver and 8-OHdG in urine. Among the biochemical markers of aging, SAC significantly reduced liver GLB1 and SA-βgal, which were induced by replicative senescence. The mitochondria with GFP-tagged transgenic strain SJ4103 C. elegans was incubated with 5 or 50 μM SAC, and SAC treated groups maintained the linear morphology of mitochondria.

CONCLUSION

SAC regulated mitochondrial dynamics and ameliorated aging to a significant degree. This study also confirmed that mitochondrial dynamics are a promising target for screening materials to combat aging and as a direction for anti-aging product development. This article is protected by copyright. All rights reserved.

An extract of Rosaceae, Solanaceae and Zingiberaceae increases health span and mobility in Caenorhabditis elegans

Background

Members of the Rosaceae, Solanaceae and Zingiberaceae families which include fruits such as cherries, tomatoes and ginger are known to have health promoting effects. There is growing interest in consuming these “functional foods” as a means to increase health and healthy ageing. However, many studies explore the effect of these foods in isolation, not as a blend of multiple functional foods.

Methods

In this study, an extract containing the dried berries, fruits, and roots of members of these families was prepared, which we called Bioact®180. The nematode Caenorhabditis elegans was used to evaluate the effects of Bioact®180 on lifespan and health endpoints, including muscle and mitochondria structure and locomotion.

Results

Exposure to the 1000 µg/mL of Bioact®180 extract, containing 4% total phenols, were healthier, as observed by an increase in mean lifespan with and small but significant increase in maximal lifespan. Nematodes exposed to Bioact®180 displayed better mobility in mid-life stages as well as enhanced mitochondrial morphology, which was more comparable to younger animals, suggesting that these worms are protected to some degree from sarcopenia.

Conclusions

Together, our findings reveal that Bioact®180, a blend of fruits and roots from Rosaceae, Solanaceae and Zingiberaceae family members has anti-aging effects. Bioact®180 promotes health and lifespan extension in C. elegans, corresponding to functional improvements in mobility.

Lack of age-related respiratory changes in Daphnia

Aging is a multifaceted process of accumulation of damage and waste in cells and tissues; age-related changes in mitochondria and in respiratory metabolism have the focus of aging research for decades. Studies of aging in nematodes, flies and mammals all revealed age-related decline in respiratory functions, with somewhat controversial causative role. Here we investigated age-related changes in respiration rates, lactate/pyruvate ratio, a commonly used proxy for NADH/NAD+ balance, and mitochondrial membrane potential in 4 genotypes of an emerging model organism for aging research, a cyclic parthenogen Daphnia magna. We show that total body weight-adjusted respiration rate decreased with age, although this decrease was small in magnitude and could be fully accounted for by the decrease in locomotion and feeding activity. Neither total respiration normalized by protein content, nor basal respiration rate measured in anaesthetized animals decreased with age. Lactate/pyruvate ratio and mitochondrial membrane potential (∆Ψ_mt) showed no age-related changes, with possible exceptions of ∆Ψ_mt in epipodites (excretory and gas exchange organs) in which ∆Ψ_mt decreased with age and in the optical lobe of the brain, in which ∆Ψ_mt showed a maximum at middle age. We conclude that actuarial senescence in Daphnia is not caused by a decline in respiratory metabolism and discuss possible mechanisms of maintaining mitochondrial healthspan throughout the lifespan.

Revisiting the contribution of mitochondrial biology to the pathophysiology of skeletal muscle insulin resistance

While the etiology of type 2 diabetes is multifaceted, the induction of insulin resistance in skeletal muscle is a key phenomenon, and impairments in insulin signaling in this tissue directly contribute to hyperglycemia. Despite the lack of clarity regarding the specific mechanisms whereby insulin signaling is impaired, the key role of a high lipid environment within skeletal muscle has been recognized for decades. Many of the proposed mechanisms leading to the attenuation of insulin signaling - namely the accumulation of reactive lipids and the pathological production of reactive oxygen species (ROS), appear to rely on this high lipid environment. Mitochondrial biology is a central component to these processes, as these organelles are almost exclusively responsible for the oxidation and metabolism of lipids within skeletal muscle and are a primary source of ROS production. Classic studies have suggested that reductions in skeletal muscle mitochondrial content and/or function contribute to lipid-induced insulin resistance; however, in recent years the role of mitochondria in the pathophysiology of insulin resistance has been gradually re-evaluated to consider the biological effects of alterations in mitochondrial content. In this respect, while reductions in mitochondrial content are not required for the induction of insulin resistance, mechanisms that increase mitochondrial content are thought to enhance mitochondrial substrate sensitivity and submaximal adenosine diphosphate (ADP) kinetics. Thus, this review will describe the central role of a high lipid environment in the pathophysiology of insulin resistance, and present both classic and contemporary views of how mitochondrial biology contributes to insulin resistance in skeletal muscle.

Nicotinamide effects on the metabolism of human fibroblasts and keratinocytes assessed by quantitative, label-free fluorescence imaging

Alterations in metabolism are central to the aging process. Therefore, understanding the subcellular functional and structural changes associated with metabolic aging is critical. Current established methods for exploring cell metabolism either require the use of exogenous agents or are destructive to the tissue or cells. Two-photon excited fluorescence (TPEF) imaging has emerged as a method for monitoring subtle metabolic changes non-invasively. In this study, we use TPEF imaging to acquire high-resolution fluorescence images from two coenzymes, NAD(P)H (reduced form of nicotinamide adenine dinucleotide) and FAD (flavin adenine dinucleotide), within human fibroblasts and keratinocytes in response to B3 (a nicotinamide precursor) supplementation and/or UV irradiation, without addition of exogenous labels. In addition, multi-parametric analysis methods are used to extract functional information of cellular metabolism, including cellular redox state, NAD(P)H fluorescence lifetime, and mitochondrial organization. Our results demonstrate that such optical metabolic assessments can serve as sensitive, label-free, non-destructive reporters of known effects of B3 to maintain and in some cases even enhance the respiratory function of mitochondria, while lowering oxidative damage. Thus, TPEF imaging, supported by highly-quantitative analysis, can serve as a tool to understand aging-dependent metabolic changes as well as the effect of actives on human epidermal and dermal cells.

Long-Term Caffeine Intake Exerts Protective Effects on Intestinal Aging by Regulating Vitellogenesis and Mitochondrial Function in an Aged Caenorhabditis Elegans Model

Caffeine, a methylxanthine derived from plants, is the most widely consumed ingredient in daily life. Therefore, it is necessary to investigate the effects of caffeine intake on essential biological activities. In this study, we attempted to determine the possible anti-aging effects of long-term caffeine intake in the intestine of an aged Caenorhabditis elegans model. We examined changes in intestinal integrity, production of vitellogenin (VIT), and mitochondrial function after caffeine intake. To evaluate intestinal aging, actin-5 (ACT-5) mislocalization, lumenal expansion, and intestinal colonization were examined after caffeine intake, and the levels of vitellogenesis as well as the mitochondrial activity were measured. We found that the long-term caffeine intake (10 mM) in the L4-stage worms at 25 °C for 3 days suppressed ACT-5 mislocalization. Furthermore, the level of autophagy, which is normally increased in aging animals, was significantly reduced in these animals, and their mitochondrial functions improved after caffeine intake. In addition, the caffeine-ingesting aging animals showed high resistance to oxidative stress and increased the expression of antioxidant proteins. Taken together, these findings reveal that caffeine may be a potential anti-aging agent that can suppress intestinal atrophy during the progression of intestinal aging.

C. elegans electrotaxis behavior is modulated by heat shock response and unfolded protein response signaling pathways

The nematode C. elegans is a leading model to investigate the mechanisms of stress-induced behavioral changes coupled with biochemical mechanisms. Our group has previously characterized C. elegans behavior using a microfluidic-based electrotaxis device, and showed that worms display directional motion in the presence of a mild electric field. In this study, we describe the effects of various forms of genetic and environmental stress on the electrotactic movement of animals. Using exposure to chemicals, such as paraquat and tunicamycin, as well as mitochondrial and endoplasmic reticulum (ER) unfolded protein response (UPR) mutants, we demonstrate that chronic stress causes abnormal movement. Additionally, we report that pqe-1 (human RNA exonuclease 1 homolog) is necessary for the maintenance of multiple stress response signaling and electrotaxis behavior of animals. Further, exposure of C. elegans to several environmental stress-inducing conditions revealed that while chronic heat and dietary restriction caused electrotaxis speed deficits due to prolonged stress, daily exercise had a beneficial effect on the animals, likely due to improved muscle health and transient activation of UPR. Overall, these data demonstrate that the electrotaxis behavior of worms is susceptible to cytosolic, mitochondrial, and ER stress, and that multiple stress response pathways contribute to its preservation in the face of stressful stimuli.

SUMO Wrestles with Mitophagy to Extend Lifespan

SUMOylation, a conserved protein post-translational modification that performs multiple functions including regulation of nuclear transport and transcription, is implicated in numerous biological processes including aging. RNAi knockdown of the sole Small Ubiquitin-like MOdifier (SUMO) gene, smo-1, in Caenorhabditis elegans shortened lifespan, whereas overexpression in the intestine modestly increased lifespan. Smo-1 is required for mitochondrial fission in a tissue-specific manner. Fission, in turn, is needed for mitophagy to maintain mitochondrial homeostasis during aging. SUMOlyation affects DAuer Formation (DAF)-16, which can be directly SUMOylated, and SKN-1, the homolog of mammalian Nrf2. These regulators play key roles in maintaining mitochondrial homeostasis. However, given the modest effect of overexpressing smo-1 on lifespan enhancement and potential interference with other genes that can promote increased lifespan, caution is advised in the translation of this study based on C. elegans. Although inhibitors of SUMOlyation have been developed for cancer and activators also have been identified, broad-acting biochemical pathway modifiers such as SUMO are often suboptimal drug targets and may not be as promising for antiaging applications as they first appear.

Relevance of endoplasmic reticulum and mitochondria interactions in age-associated diseases

Although the elixir of youth remains in the darkness, medical and scientific advances have succeeded in increasing human longevity; however, the predisposition to disease and its high economic cost are raising. Different strategies (e.g., antioxidants) and signaling pathways (e.g., Nrf2) have been identified to help regulate disease progression, nevertheless, there are still missing links that we need to understand. Contact sites called mitochondria-associated membranes (MAM) allow bi-directional communication between organelles as part of the essential functions in the cell to maintain its homeostasis. Different groups have deeply studied the role of MAM in aging; however, it's necessary to analyze their involvement in the progression of age-related diseases. In this review, we highlight the role of contact sites in these conditions, as well as the morphological and functional changes of mitochondria and ER in aging. We emphasize the intimate relationship between both organelles as a reflection of the biological processes that take place in the cell to try to regulate the deterioration characteristic of the aging process; proposing MAM as a potential target to help limit the disease progression with age.

Axin-Mediated Regulation of Lifespan and Muscle Health in C. elegans Requires AMPK-FOXO Signaling

Aging is a significant risk factor for several diseases. Studies have uncovered multiple signaling pathways that modulate aging, including insulin/insulin-like growth factor-1 signaling (IIS). In Caenorhabditis elegans, the key regulator of IIS is DAF-16/FOXO. One of the kinases that affects DAF-16 function is the AMPK catalytic subunit homolog AAK-2. In this study, we report that PRY-1/Axin plays an essential role in AAK-2 and DAF-16-mediated regulation of life span. The pry-1 mutant transcriptome contains many genes associated with aging and muscle function. Consistent with this, pry-1 is strongly expressed in muscles, and muscle-specific overexpression of pry-1 extends life span, delays muscle aging, and improves mitochondrial morphology in AAK-2-DAF-16-dependent manner. Furthermore, PRY-1 is necessary for AAK-2 phosphorylation. Taken together, our data demonstrate that PRY-1 functions in muscles to promote the life span of animals. This study establishes Axin as a major regulator of muscle health and aging.

•

pry-1 transcriptome contains genes linked to aging and muscle function

•

pry-1 functions in muscles to maintain life span and mitochondrial network

•

Muscle-specific overexpression of pry-1 extends life span and promotes muscle health

•

PRY-1-mediated life span extension depends on AAK-2-DAF-16 signaling

Paraquat exposure over generation affects lifespan and reproduction through mitochondrial disruption in C. elegans

Paraquat (methyl viologen), is a non-selective contact herbicide and well known mitochondrial toxicant. Mitochondria are the center of cellular metabolism, and involved in the development, lifespan, and reproduction of an organism. Mitochondria are dynamic organelles that are inherited maternally through the germline and carry multiple copies of their own genome (mtDNA). It is important to understand the effects of acute and chronic stress caused by mitochondrial toxicants over multiple generations at the cellular and organism levels. Using the model nematode C. elegans, we show that acute and chronic exposure to paraquat affects reproduction, longevity, gene expression, and mitochondrial physiology. Acute exposure to paraquat in N2 (wild type) causes induction of mitochondrial unfolded protein response (mtUPR), increased expression of mitochondrial superoxide dismutase, decreased mitochondrial membrane potential (Δψm), a dose-dependent progression from linear to fragmented mitochondria, and dose-dependent changes in longevity. Chronic exposure to a low dose of paraquat (0.035 mM) over multiple generations in N2 causes a progressive decline of fertility, leading to complete loss of fertile embryo production by the third generation. The mutation in CEP-1 [cep-1(gk138)], a key regulator of stress-induced apoptosis in the germline, causes increased sensitivity to chronic paraquat relative to N2 with no fertile embryo production beyond the second generation. Whereas, mitochondrial electron transport chain (complex III) mutant [isp-1(qm150)], which display constitutive activation of mtUPR showed increased tolerance and produced fertile embryo out to the fourth generation. The N2, cep-1(gk138), and isp-1(qm150) strain's lifespan over multiple generations exposed to chronic paraquat were measured. Fertility and lifespan data together indicate a trade-off between reproduction and somatic maintenance during chronic paraquat exposure. We have proposed that mitochondrial signaling, dynamics, and CEP-1 mediated germline apoptosis is involved in this trade-off.

Loss of metabolic plasticity underlies metformin toxicity in aged Caenorhabditis elegans

Current clinical trials are testing the life-extending benefits of the diabetes drug metformin in healthy individuals without diabetes. However, the metabolic response of a non-diabetic cohort to metformin treatment has not been studied. Here, we show in C. elegans and human primary cells that metformin shortens lifespan when provided in late life, contrary to its positive effects in young organisms. We find that metformin exacerbates ageing-associated mitochondrial dysfunction, causing respiratory failure. Age-related failure to induce glycolysis and activate the dietary-restriction-like mobilization of lipid reserves in response to metformin result in lethal ATP exhaustion in metformin-treated aged worms and late-passage human cells, which can be rescued by ectopic stabilization of cellular ATP content. Metformin toxicity is alleviated in worms harbouring disruptions in insulin-receptor signalling, which show enhanced resilience to mitochondrial distortions at old age. Together, our data show that metformin induces deleterious changes of conserved metabolic pathways in late life, which could bring into question its benefits for older individuals without diabetes.

SUMO promotes longevity and maintains mitochondrial homeostasis during ageing in Caenorhabditis elegans

The insulin/IGF signalling pathway impacts lifespan across distant taxa, by controlling the activity of nodal transcription factors. In the nematode Caenorhabditis elegans, the transcription regulators DAF-16/FOXO and SKN-1/Nrf function to promote longevity under conditions of low insulin/IGF signalling and stress. The activity and subcellular localization of both DAF-16 and SKN-1 is further modulated by specific posttranslational modifications, such as phosphorylation and ubiquitination. Here, we show that ageing elicits a marked increase of SUMO levels in C. elegans. In turn, SUMO fine-tunes DAF-16 and SKN-1 activity in specific C. elegans somatic tissues, to enhance stress resistance. SUMOylation of DAF-16 modulates mitochondrial homeostasis by interfering with mitochondrial dynamics and mitophagy. Our findings reveal that SUMO is an important determinant of lifespan, and provide novel insight, relevant to the complexity of the signalling mechanisms that influence gene expression to govern organismal survival in metazoans.

Age-Related Deterioration of Mitochondrial Function in the Intestine

Aging is an important and inevitable biological process in human life, associated with the onset of chronic disease and death. The mechanisms behind aging remain unclear. However, changes in mitochondrial function and structure, including reduced activity of the mitochondrial respiratory chain and increased production of reactive oxygen species—thus oxidative damage—are believed to play a major role. Mitochondria are the main source of cellular energy, producing adenosine triphosphate (ATP) via oxidative phosphorylation. Accumulation of damaged cellular components reduces a body's capacity to preserve tissue homeostasis and affects biological aging and all age-related chronic conditions. This includes the onset and progression of classic degenerative diseases such as cardiovascular disease, kidney failure, neurodegenerative diseases, and cancer. Clinical manifestations of intestinal disorders, such as mucosal barrier dysfunction, intestinal dysmotility, and chronic obstipation, are highly prevalent in the elderly population and have been shown to be associated with an age-dependent decline of mitochondrial function. This review summarizes our current understanding of the role of mitochondrial dysfunction in intestinal aging.

Cell-autonomous and non-autonomous roles of daf-16 in muscle function and mitochondrial capacity in aging C. elegans

Sarcopenia, defined as the loss of skeletal muscle mass and strength, contributes to disability and health-related conditions with aging. In vitro studies indicate that age-related mitochondrial dysfunction could play a central role in the development and progression of sarcopenia, but because of limitations in the methods employed, how aging affects muscle mitochondrial function in vivo is not fully understood. We use muscle-targeted fluorescent proteins and the ratiometric ATP reporter, ATeam, to examine changes in muscle mitochondrial mass and morphology, and intracellular ATP levels in C. elegans. We find that the preserved muscle function in aging daf-2 mutants is associated with higher muscle mitochondrial mass, preserved mitochondrial morphology, and higher levels of intracellular ATP. These phenotypes require the daf-16/FOXO transcription factor. Via the tissue-specific rescue of daf-16, we find that daf-16 activity in either muscle or neurons is sufficient to enhance muscle mitochondrial mass, whereas daf-16 activity in the muscle is required for the enhanced muscle function and mobility of the daf-2 mutants. Finally, we show through the use of drugs known to enhance mitochondrial activity that augmenting mitochondrial function leads to improved mobility during aging. These results suggest an important role for mitochondrial function in muscle aging.

Disruption of mitochondrial dynamics increases stress resistance through activation of multiple stress response pathways

Mitochondria are dynamic organelles that can change shape and size depending on the needs of the cell through the processes of mitochondrial fission and fusion. In this work, we investigated the role of mitochondrial dynamics in organismal stress response. By using C. elegans as a genetic model, we could visualize mitochondrial morphology in a live organism with well‐established stress assays and well‐characterized stress response pathways. We found that disrupting mitochondrial fission (DRP1/drp‐1) or fusion (OPA1/eat‐3, MFN/fzo‐1) genes caused alterations in mitochondrial morphology that impacted both mitochondrial function and physiologic rates. While both mitochondrial fission and mitochondrial fusion mutants showed increased sensitivity to osmotic stress and anoxia, surprisingly we found that the mitochondrial fusion mutants eat‐3 and fzo‐1 are more resistant to both heat stress and oxidative stress. In exploring the mechanism of increased stress resistance, we found that disruption of mitochondrial fusion genes resulted in the upregulation of multiple stress response pathways. Overall, this work demonstrates that disrupting mitochondrial dynamics can have opposite effects on resistance to different types of stress. Our results suggest that disruption of mitochondrial fusion activates multiple stress response pathways that enhance resistance to specific stresses.

Inhibition of mTOR Alleviates Early Brain Injury After Subarachnoid Hemorrhage Via Relieving Excessive Mitochondrial Fission

The mammalian target of rapamycin (mTOR) was reported to regulate cell autophagy and outcomes of several neurological diseases. Mitochondria, which serve as critical organelles in neurons. are also involved in the pathology of neurological diseases. However, the role of mTOR in mitochondrial morphology has not been clarified especially in subarachnoid hemorrhage (SAH). In this study, we established SAH models both in vivo and in vitro. Rapamycin and 3-methyl adenine (3-MA) were then administered to alter mTOR activity. Post-SAH assessment included SAH grading, neurological evaluation, blood-brain barrier (BBB) permeability, brain water content, mitochondrial membrane potential (MMP), mitochondrial morphology, ATP content, cell viability, cytotoxicity, and expression of proteins related to apoptosis and mitochondrial fission. The results showed that (1) neurological deficits, BBB permeability, and brain edema were increased after SAH and that cell viability was exacerbated in brain tissue. (2) Excessive mitochondrial fission was evident based on changes in mitochondrial morphology, while MMP and ATP content were decreased in neurons after SAH. (3) Administration of rapamycin improved the excessive mitochondrial fission and restored mitochondrial function, which subsequently reduced apoptosis. (4) 3-MA showed an adverse effect on mitochondria and aggravated excessive mitochondrial fission and dysfunction in SAH. Neurological deficits and neuronal viability were also exacerbated following the administration of 3-MA. Therefore, our study suggests that mTOR inhibition has neuroprotective effects against neuronal injury after SAH via alleviating excessive mitochondrial fission.

A cellular surveillance and defense system that delays aging phenotypes in C. elegans

Physiological stresses, such as pathogen infection, are detected by “cellular Surveillance Activated Detoxification and Defenses” (cSADD) systems that trigger host defense responses. Aging is associated with physiological stress, including impaired mitochondrial function. Here, we investigated whether an endogenous cSADD pathway is activated during aging in C. elegans. We provide evidence that the transcription factor ZIP-2, a well-known immune response effector in C. elegans, is activated in response to age-associated mitochondrial dysfunction. ZIP-2 mitigates multiple aging phenotypes, including mitochondrial disintegration and reduced motility of the pharynx and intestine. Importantly, our data suggest that ZIP-2 is activated during aging independently of bacterial infection and of the transcription factors ATFS-1 and CEBP-2. Thus, ZIP-2 is a key component of an endogenous pathway that delays aging phenotypes in C. elegans. Our data suggest that aging coopted a compensatory strategy for regulation of aging process as a guarded process rather than a simple passive deterioration process.

Targeting Mitochondrial Network Architecture in Down Syndrome and Aging

Mitochondria are organelles that mainly control energy conversion in the cell. In addition, they also participate in many relevant activities, such as the regulation of apoptosis and calcium levels, and other metabolic tasks, all closely linked to cell viability. Functionality of mitochondria appears to depend upon their network architecture that may dynamically pass from an interconnected structure with long tubular units, to a fragmented one with short separate fragments. A decline in mitochondrial quality, which presents itself as an altered structural organization and a function of mitochondria, has been observed in Down syndrome (DS), as well as in aging and in age-related pathologies. This review provides a basic overview of mitochondrial dynamics, from fission/fusion mechanisms to mitochondrial homeostasis. Molecular mechanisms determining the disruption of the mitochondrial phenotype in DS and aging are discussed. The impaired activity of the transcriptional co-activator PGC-1α/PPARGC1A and the hyperactivation of the mammalian target of rapamycin (mTOR) kinase are emerging as molecular underlying causes of these mitochondrial alterations. It is, therefore, likely that either stimulating the PGC-1α activity or inhibiting mTOR signaling could reverse mitochondrial dysfunction. Evidence is summarized suggesting that drugs targeting either these pathways or other factors affecting the mitochondrial network may represent therapeutic approaches to improve and/or prevent the effects of altered mitochondrial function. Overall, from all these studies it emerges that the implementation of such strategies may exert protective effects in DS and age-related diseases.

Mitophagy in the Retinal Pigment Epithelium of Dry Age-Related Macular Degeneration Investigated in the NFE2L2/PGC-1α-/- Mouse Model

Increased oxidative stress and mitochondrial damage are observed in protein aggregation diseases, such as age-related macular degeneration (AMD). We have recently reported elevated levels of oxidative stress markers, damaged mitochondria, accumulating lysosomal lipofuscin and extracellular drusen-like structures in the retinal pigment epithelial cells (RPE) of the dry AMD-resembling NFE2L2/PGC1α double knockout (dKO) mouse model. Here, we provide evidence of a disturbance in the autolysosomal machinery handling mitochondrial clearance in the RPE cells of one-year-old NFE2L2/PGC1α-deficient mice. Confocal immunohistochemical analysis revealed an upregulation of autophagosome marker microtubule-associated proteins 1A/1B light chain 3B (LC3B) as well as numerous mitophagy markers, such as PTE-induced putative kinase 1 (PINK1) and E3 ubiquitin ligase (PARKIN) together with damaged mitochondria. However, we detected no evidence of increased autolysosome formation in transmission electron micrographs or of colocalization of lysosomal marker LAMP2 (lysosome-associated membrane protein 2) and the mitochondrial marker ATP synthase β in confocal micrographs. Interestingly, we observed an upregulation of late autolysosomal fusion Ras-related protein (Rab7) in the perinuclear space of RPE cells together with autofluorescence aggregates. Our results reveal that there is at least a relative decrease of mitophagy in the RPE cells of NFE2L2/PGC1α dKO mice. This further supports the hypothesis that mitophagy is a putative therapy target in AMD-like pathology.

Mitochondrial fission and fusion: A dynamic role in aging and potential target for age-related disease

The mitochondria is the major hub to convert energy for cellular processes. Dysregulation of mitochondrial function is one of the classical hallmarks of aging, and mitochondrial interventions have repeatedly been shown to improve outcomes in age-related diseases. Crucial to mitochondrial regulation is the dynamic nature of their network structure. Mitochondria separate and merge using fission and fusion processes in response to changes in energy and stress status. While many mitochondrial processes are already characterized in relation to aging, specific evidence in multicellular organisms causally linking mitochondrial dynamics to the regulation of lifespan is limited. There does exist, however, a large body of evidence connecting mitochondrial dynamics to other aging-related cellular processes and implicates them in a number of human diseases. Here, we discuss the mechanisms of mitochondrial fission and fusion, the current evidence of their role in aging of multicellular organisms, and how these connect to cell cycle regulation, quality control, and transmission of energy status. Finally, we discuss the current evidence implicating these processes in age-related human pathologies, such as neurodegenerative or cardio-metabolic diseases. We suggest that deeper understanding of the regulatory mechanisms within this system and downstream implications could benefit in understanding and intervention of these conditions.

Greater loss of mitochondrial function with ageing is associated with earlier onset of sarcopenia in C. elegans

Sarcopenia, the age-related decline of muscle, is a significant and growing public health burden. C. elegans, a model organism for investigating the mechanisms of ageing, also displays sarcopenia, but the underlying mechanism(s) remain elusive. Here, we use C. elegans natural scaling of lifespan in response to temperature to examine the relationship between mitochondrial content, mitochondrial function, and sarcopenia. Mitochondrial content and maximal mitochondrial ATP production rates (MAPR) display an inverse relationship to lifespan, while onset of MAPR decline displays a direct relationship. Muscle mitochondrial structure, sarcomere structure, and movement decline also display a direct relationship with longevity. Notably, the decline in mitochondrial network structure occurs earlier than sarcomere decline, and correlates more strongly with loss of movement, and scales with lifespan. These results suggest that mitochondrial function is critical in the ageing process and more robustly explains the onset and progression of sarcopenia than loss of sarcomere structure.

Swim exercise in Caenorhabditis elegans extends neuromuscular and gut healthspan, enhances learning ability, and protects against neurodegeneration

Exercise is a powerful antiaging intervention that protects against cardiovascular disease, dementia, diabetes, sarcopenia, and cancer. How exercise promotes health benefits to multiple tissues in the body, however, remains poorly understood. We establish a young adult swim exercise regimen for the short-lived nematode Caenorhabditis elegans that induces health benefits at the neuromuscular, intestinal, and cognitive levels and protects against neurodegeneration in models of tauopathy, Alzheimer’s disease, and Huntington’s disease. Importantly, we found that swim exercise performed exclusively in early adulthood promotes long-lasting systemic benefits that are still detectable in midlife. The advantages of C. elegans as a short-lived genetic model will allow for dissection of the molecular circuitry involved in system-wide exercise benefits.

Regular physical exercise is the most efficient and accessible intervention known to promote healthy aging in humans. The molecular and cellular mechanisms that mediate system-wide exercise benefits, however, remain poorly understood, especially as applies to tissues that do not participate directly in training activity. The establishment of exercise protocols for short-lived genetic models will be critical for deciphering fundamental mechanisms of transtissue exercise benefits to healthy aging. Here we document optimization of a long-term swim exercise protocol for Caenorhabditis elegans and we demonstrate its benefits to diverse aging tissues, even if exercise occurs only during a restricted phase of adulthood. We found that multiple daily swim sessions are essential for exercise adaptation, leading to body wall muscle improvements in structural gene expression, locomotory performance, and mitochondrial morphology. Swim exercise training enhances whole-animal health parameters, such as mitochondrial respiration and midlife survival, increases functional healthspan of the pharynx and intestine, and enhances nervous system health by increasing learning ability and protecting against neurodegeneration in models of tauopathy, Alzheimer’s disease, and Huntington’s disease. Remarkably, swim training only during early adulthood induces long-lasting systemic benefits that in several cases are still detectable well into midlife. Our data reveal the broad impact of swim exercise in promoting extended healthspan of multiple C. elegans tissues, underscore the potency of early exercise experience to influence long-term health, and establish the foundation for exploiting the powerful advantages of this genetic model for the dissection of the exercise-dependent molecular circuitry that confers system-wide health benefits to aging adults.