Stochastic and genetic factors influence tissue-specific decline in ageing C. elegans

Asymmetry, division of labour and the evolution of ageing in multicellular organisms

Between the 1930s and 1960s, evolutionary geneticists worked out the basic principles of why organisms age. Despite much progress in the evolutionary biology of ageing since that time, however, many puzzles remain. The perhaps most fundamental of these is the question of which organisms should exhibit senescence and which should not (or which should age rapidly and which should not). The evolutionary origin of ageing from a non-senescent state has been conceptually framed, for example, in terms of the separation between germ-line and soma, the distinction between parents and their offspring, and-in unicellular organisms-the unequal distribution of cellular damage at cell division. These ideas seem to be closely related to the concept of 'division of labour' between reproduction and somatic maintenance. Here, we review these concepts and develop a toy model to explore the importance of such asymmetries for the evolution of senescence. We apply our model to the simplest case of a multicellular system: an organism consisting of two totipotent cells. Notably, we find that in organisms which reproduce symmetrically and partition damage equally, senescence is still able to evolve, contrary to previous claims. Our results might have some bearing on understanding the origin of the germ-line-soma separation and the evolution of senescence in multicellular organisms and in colonial species consisting of multiple types of individuals, such as, for example, eusocial insects with their different castes. This article is part of the theme issue 'Ageing and sociality: why, when and how does sociality change ageing patterns?'

Catechinic acid, a natural polyphenol compound, extends the lifespan of Caenorhabditis elegans via mitophagy pathways

Catechinic acid (CA), widely present in tea and fruits, has vital biological and pharmacological properties. CA plays an important role in the regulation of lifespan. However, the mechanism behind its anti-aging properties remains poorly characterized. In the present study, Caenorhabditis elegans (C. elegans) was used as a model organism. It was found that CA induced mitophagy which prevented the accumulation of dysfunctional mitochondria with age and profoundly extended lifespan. Notably, CA significantly improved the fitness of aging worms, particularly the treatment slowed age-related decline in observed spontaneous movements. Furthermore, CA was found to eliminate dysfunctional mitochondria in the gut and muscle cells, and demonstrated that the lifespan-prolonging effects of CA can be attributed to mitophagy along with the likely regulation of the genes bec-1 and pink-1. The results of this study indicated that pharmacologically induced mitophagy has a profound impact on aging, providing a novel therapeutic intervention against aging and age-related diseases.

Aging features of the migratory locust at physiological and transcriptional levels

Background

Non-Drosophila insects provide diverse aging types and important complementary systems for studies of aging biology. However, little attention has been paid to the special roles of non-Drosophila insects in aging research. Here, the aging-related features of the migratory locust, Locusta migratoria, were determined at the physiological, cellular, and transcriptional levels.

Results

In physiological assessments, the flight performance and sperm state of locusts displayed clear aging-related decline in male adults. Transcriptional analyses demonstrated locusts have similar aging-related genes with model species. However, different from those of Drosophila and mammals, the organ-specific aging transcriptional features of locusts were characterized by intensive expression changes in flight muscle and fat body and little transcriptional changes in brain. The predominant transcriptional characteristics of flight muscle and fat body aging were changes in expression of mitochondrion-related genes and detoxification and phagocytosis genes, respectively. Cellular assessments revealed the incidence of mitochondrial abnormalities significantly increased in aged flight muscle, and apoptotic signals and nuclear abnormalities were enhanced in aged fat body but not in brain. In addition, some well-known aging genes and locust aging-related genes (i.e., IAP1, PGRP-SA, and LIPT1), whose roles in aging regulation were rarely reported, were demonstrated to affect lifespan, metabolism, and flight ability of locusts after RNAi.

Conclusion

This study revealed multi-level aging signatures of locust, thus laying a foundation for further investigation of aging mechanisms in this famous insect in the future.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-07585-3.

Preconditioning of Caenorhabditis elegans to anoxic insult by inactivation of cholinergic, GABAergic and muscle activity

For most metazoans, oxygen deprivation leads to cell dysfunction and if severe, death. Sublethal stress prior to a hypoxic or anoxic insult ("preconditioning") can protect cells from subsequent oxygen deprivation. The molecular mechanisms by which sublethal stress can buffer against a subsequent toxic insult and the role of the nervous system in the response are not well understood. We studied the role of neuronal activity preconditioning to oxygen deprivation in Caenorhabditis elegans. Animals expressing the histamine gated chloride channels (HisCl1) in select cell populations were used to temporally and spatially inactivate the nervous system or tissue prior to an anoxic insult. We find that inactivation of the nervous system for 3 h prior to the insult confers resistance to a 48-h anoxic insult in 4th-stage larval animals. Experiments show that this resistance can be attributed to loss of activity in cholinergic and GABAergic neurons as well as in body wall muscles. These observations indicate that the nervous system activity can mediate the organism's response to anoxia.

The decrease of intraflagellar transport impairs sensory perception and metabolism in ageing

Sensory perception and metabolic homeostasis are known to deteriorate with ageing, impairing the health of aged animals, while mechanisms underlying their deterioration remain poorly understood. The potential interplay between the declining sensory perception and the impaired metabolism during ageing is also barely explored. Here, we report that the intraflagellar transport (IFT) in the cilia of sensory neurons is impaired in the aged nematode Caenorhabditis elegans due to a daf-19/RFX-modulated decrease of IFT components. We find that the reduced IFT in sensory cilia thus impairs sensory perception with ageing. Moreover, we demonstrate that whereas the IFT-dependent decrease of sensory perception in aged worms has a mild impact on the insulin/IGF-1 signalling, it remarkably suppresses AMP-activated protein kinase (AMPK) signalling across tissues. We show that upregulating daf-19/RFX effectively enhances IFT, sensory perception, AMPK activity and autophagy, promoting metabolic homeostasis and longevity. Our study determines an ageing pathway causing IFT decay and sensory perception deterioration, which in turn disrupts metabolism and healthy ageing.

From mutation to mechanism: deciphering the molecular function of genetic variants linked to human ageing

Many of the leading causes of death in humans, such as cardiovascular disease, type 2 diabetes and Alzheimer’s disease are influenced by biological mechanisms that become dysregulated with increasing age. Hence, by targeting these ageing-related mechanisms, we may be able to improve health in old age. Ageing is partly heritable and genetic studies have been moderately successful in identifying genetic variants associated with ageing-related phenotypes (lifespan, healthspan and longevity). To decipher the mechanisms by which the identified variants influence ageing, studies that focus on their functional validation are vital. In this perspective, we describe the steps that could be taken in the process of functional validation: (1) in silico characterisation using bioinformatic tools; (2) in vitro characterisation using cell lines or organoids; and (3) in vivo characterisation studies using model organisms. For the in vivo characterisation, it is important to focus on translational phenotypes that are indicative of both healthspan and lifespan, such as the frailty index, to inform subsequent intervention studies. The depth of functional validation of a genetic variant depends on its location in the genome and conservation in model organisms. Moreover, some variants may prove to be hard to characterise due to context-dependent effects related to the experimental environment or genetic background. Future efforts to functionally characterise the (newly) identified genetic variants should shed light on the mechanisms underlying ageing and will help in the design of targeted interventions to improve health in old age.

Mitochondrial hydrogen sulfide supplementation improves health in the C. elegans Duchenne muscular dystrophy model

Duchenne muscular dystrophy (DMD) is an X-linked recessive disorder characterized by progressive muscle degeneration and weakness due to mutations in the dystrophin gene. The symptoms of DMD share similarities with those of accelerated aging. Recently, hydrogen sulfide (H2S) supplementation has been suggested to modulate the effects of age-related decline in muscle function, and metabolic H2S deficiencies have been implicated in affecting muscle mass in conditions such as phenylketonuria. We therefore evaluated the use of sodium GYY4137 (NaGYY), a H2S-releasing molecule, as a possible approach for DMD treatment. Using the dys-1(eg33) Caenorhabditis elegans DMD model, we found that NaGYY treatment (100 µM) improved movement, strength, gait, and muscle mitochondrial structure, similar to the gold-standard therapeutic treatment, prednisone (370 µM). The health improvements of either treatment required the action of the kinase JNK-1, the transcription factor SKN-1, and the NAD-dependent deacetylase SIR-2.1. The transcription factor DAF-16 was required for the health benefits of NaGYY treatment, but not prednisone treatment. AP39 (100 pM), a mitochondria-targeted H2S compound, also improved movement and strength in the dys-1(eg33) model, further implying that these improvements are mitochondria-based. Additionally, we found a decline in total sulfide and H2S-producing enzymes in dystrophin/utrophin knockout mice. Overall, our results suggest that H2S deficit may contribute to DMD pathology, and rectifying/overcoming the deficit with H2S delivery compounds has potential as a therapeutic approach to DMD treatment.

Structural aspects of the aging invertebrate brain

Aging is characterized by a decline in neuronal function in all animal species investigated so far. Functional changes are accompanied by and may be in part caused by, structurally visible degenerative changes in neurons. In the mammalian brain, normal aging shows abnormalities in dendrites and axons, as well as ultrastructural changes in synapses, rather than global neuron loss. The analysis of the structural features of aging neurons, as well as their causal link to molecular mechanisms on the one hand, and the functional decline on the other hand is crucial in order to understand the aging process in the brain. Invertebrate model organisms like Drosophila and C. elegans offer the opportunity to apply a forward genetic approach to the analysis of aging. In the present review, we aim to summarize findings concerning abnormalities in morphology and ultrastructure in invertebrate brains during normal aging and compare them to what is known for the mammalian brain. It becomes clear that despite of their considerably shorter life span, invertebrates display several age-related changes very similar to the mammalian condition, including the retraction of dendritic and axonal branches at specific locations, changes in synaptic density and increased accumulation of presynaptic protein complexes. We anticipate that continued research efforts in invertebrate systems will significantly contribute to reveal (and possibly manipulate) the molecular/cellular pathways leading to neuronal aging in the mammalian brain.

Latent alterations in swimming behavior by developmental methylmercury exposure are modulated by the homolog of tyrosine hydroxylase in Caenorhabditis elegans

Methylmercury (MeHg) is a persistent environmental neurotoxicant that may cause adverse neurodevelopmental effects. Previous studies showed that developmental MeHg exposure caused damage to brain functions that were unmasked after a silent period of years or decades. However, the underlying mechanisms of the latent neurotoxicity associated with MeHg exposure from earlier developmental stages have yet to be fully understood. Herein, we established a Caenorhabditis elegans (C. elegans) model of developmental MeHg latent toxicity. Synchronized L1 stage worms were exposed to MeHg (0, 0.05, 0.5 and 5 μM) for 48 h. Swimming moving speeds at adulthood were analyzed in worms exposed to MeHg exposure at early larvae stages. Worms developmentally exposed to MeHg had a significant decline in swimming moving speed on day 10 adult stage, but not on day 1 or 5 adult stage, even though the mercury level in the worms exposed to 0.05 or 0.5 μM MeHg were below the quantification limit on day 10 adult. Day 10 adult worms treated with MeHg showed a significant decrease in bending angle and bending frequency during swimming. Furthermore, their reduced moving speeds tended to increase during the 300-s swimming experiment. Dopamine signaling is known to be involved in the regulation of worms' moving speed. Accordingly, the moving speed of worms with cat-2 (mammalian tyrosine hydroxylase homolog) mutation or dat-1 deletion were assayed on day 10 adult. The cat-2 mutant worms did not show a decline in moving speeds, body bends or bending angles during swimming on day 10 adult stage. Analyses of moving speeds of worms with dat-1 deletion showed that the moving speeds were further reduced after MeHg exposure. However, the effects of MeHg and dat-1 deletion were not synergistic, as the interaction between these parameters did not attain statistical significance. Altogether, our results suggest that developmental MeHg exposure reduced moving speed, and this latent toxicity was less pronounced in the context of deficient production of dopamine synthesis. Tyrosine hydroxylase plays an important role in regulating dopamine-mediated modulation of neurobehavioral functions. These findings uncovered a pivotal role of dopamine and its metabolism in the latent neurotoxic effects of MeHg.

Spaceflight affects neuronal morphology and alters transcellular degradation of neuronal debris in adult Caenorhabditis elegans

Extended space travel is a goal of government space agencies and private companies. However, spaceflight poses risks to human health, and the effects on the nervous system have to be better characterized. Here, we exploited the unique experimental advantages of the nematode Caenorhabditis elegans to explore how spaceflight affects adult neurons in vivo. We found that animals that lived 5 days of adulthood on the International Space Station exhibited hyperbranching in PVD and touch receptor neurons. We also found that, in the presence of a neuronal proteotoxic stress, spaceflight promotes a remarkable accumulation of neuronal-derived waste in the surrounding tissues, suggesting an impaired transcellular degradation of debris released from neurons. Our data reveal that spaceflight can significantly affect adult neuronal morphology and clearance of neuronal trash, highlighting the need to carefully assess the risks of long-duration spaceflight on the nervous system and to develop adequate countermeasures for safe space exploration.

Statistical image processing quantifies the changes in cytoplasmic texture associated with aging in Caenorhabditis elegans oocytes

Background

Oocyte quality decreases with aging, thereby increasing errors in fertilization, chromosome segregation, and embryonic cleavage. Oocyte appearance also changes with aging, suggesting a functional relationship between oocyte quality and appearance. However, no methods are available to objectively quantify age-associated changes in oocyte appearance.

Results

We show that statistical image processing of Nomarski differential interference contrast microscopy images can be used to quantify age-associated changes in oocyte appearance in the nematode Caenorhabditis elegans. Max–min value (mean difference between the maximum and minimum intensities within each moving window) quantitatively characterized the difference in oocyte cytoplasmic texture between 1- and 3-day-old adults (Day 1 and Day 3 oocytes, respectively). With an appropriate parameter set, the gray level co-occurrence matrix (GLCM)-based texture feature Correlation (COR) more sensitively characterized this difference than the Max–min Value. Manipulating the smoothness of and/or adding irregular structures to the cytoplasmic texture of Day 1 oocyte images reproduced the difference in Max–min Value but not in COR between Day 1 and Day 3 oocytes. Increasing the size of granules in synthetic images recapitulated the age-associated changes in COR. Manual measurements validated that the cytoplasmic granules in oocytes become larger with aging.

Conclusions

The Max–min value and COR objectively quantify age-related changes in C. elegans oocyte in Nomarski DIC microscopy images. Our methods provide new opportunities for understanding the mechanism underlying oocyte aging.

Xenobiotic metabolism and transport in Caenorhabditis elegans

Caenorhabditis elegans has emerged as a major model in biomedical and environmental toxicology. Numerous papers on toxicology and pharmacology in C. elegans have been published, and this species has now been adopted by investigators in academic toxicology, pharmacology, and drug discovery labs. C. elegans has also attracted the interest of governmental regulatory agencies charged with evaluating the safety of chemicals. However, a major, fundamental aspect of toxicological science remains underdeveloped in C. elegans: xenobiotic metabolism and transport processes that are critical to understanding toxicokinetics and toxicodynamics, and extrapolation to other species. The aim of this review was to initially briefly describe the history and trajectory of the use of C. elegans in toxicological and pharmacological studies. Subsequently, physical barriers to chemical uptake and the role of the worm microbiome in xenobiotic transformation were described. Then a review of what is and is not known regarding the classic Phase I, Phase II, and Phase III processes was performed. In addition, the following were discussed (1) regulation of xenobiotic metabolism; (2) review of published toxicokinetics for specific chemicals; and (3) genetic diversity of these processes in C. elegans. Finally, worm xenobiotic transport and metabolism was placed in an evolutionary context; key areas for future research highlighted; and implications for extrapolating C. elegans toxicity results to other species discussed.

In Vivo Quasi-Elastic Light Scattering Eye Scanner Detects Molecular Aging in Humans

The absence of clinical tools to evaluate individual variation in the pace of aging represents a major impediment to understanding aging and maximizing health throughout life. The human lens is an ideal tissue for quantitative assessment of molecular aging in vivo. Long-lived proteins in lens fiber cells are expressed during fetal life, do not undergo turnover, accumulate molecular alterations throughout life, and are optically accessible in vivo. We used quasi-elastic light scattering (QLS) to measure age-dependent signals in lenses of healthy human subjects. Age-dependent QLS signal changes detected in vivo recapitulated time-dependent changes in hydrodynamic radius, protein polydispersity, and supramolecular order of human lens proteins during long-term incubation (~1 year) and in response to sustained oxidation (~2.5 months) in vitro. Our findings demonstrate that QLS analysis of human lens proteins provides a practical technique for noninvasive assessment of molecular aging in vivo.

Dietary Restriction Improves Fitness of Aging Parents But Reduces Fitness of Their Offspring in Nematodes

Dietary restriction (DR) is a well-established intervention to extend lifespan across taxa. Recent studies suggest that DR-driven lifespan extension can be cost-free, calling into question a central tenant of the evolutionary theory of aging. Nevertheless, boosting parental longevity can reduce offspring fitness. Such intergenerational trade-offs are often ignored but can account for the "missing costs" of longevity. Here, we use the nematode Caenorhabditis remanei to test for effects of DR by fasting on fitness of females and their offspring. Females deprived of food for 6 days indeed had increased fecundity, survival, and stress resistance after re-exposure to food compared with their counterparts with constant food access. However, offspring of DR mothers had reduced early and lifetime fecundity, slower growth rate, and smaller body size at sexual maturity. These findings support the direct trade-off between investment in soma and gametes challenging the hypothesis that increased somatic maintenance and impaired reproduction can be decoupled.

Asynchronous, contagious and digital aging

Aging has largely been defined by analog measures of organ and organismal dysfunction. This has led to the characterization of aging processes at the molecular and cellular levels that underlie these gradual changes. However, current knowledge does not fully explain the growing body of data emerging from large epidemiological, systems biology, and single cell studies of entire organisms pointing to varied rates of aging between individuals (different functionality and lifespan), across lifespan (asynchronous aging), and within an organism at the tissue and organ levels (aging mosaicism). Here we consider these inhomogeneities in the broader context of the rate of aging and from the perspective of underlying cellular changes. These changes reflect genetic, environmental, and stochastic factors that cells integrate to adopt new homeostatic, albeit less functional, states, such as cellular senescence. In this sense, cellular aging can be viewed, at least in part, as a quantal process we refer to as "digital aging". Nevertheless, analog declines of tissue dysfunction and organ failure with age could be the sum of underlying digital events. Importantly, cellular aging, digital or otherwise, is not uniform across time or space within the organism or between organisms of the same species. Certain tissues may exhibit earliest signs of cellular aging, acting as drivers for organismal aging as signals from those driver cells within those tissues may accelerate the aging of other cells locally or even systemically. Advanced methodologies at the systems level and at the single cell level are likely to continue to refine our understanding to the processes of how cells and tissues age and how the integration of those processes leads to the complexities of individual, organismal aging.

Intrapopulation analysis of longitudinal lifespan in Caenorhabditis elegans identifies W09D10.4 as a novel AMPK-associated healthspan shortening factor

Caenorhabditis elegans is a model organism widely used for longevity studies. Current advances have been made in the methods that allow automated monitoring of C. elegans behavior. However, ordinary manual assays as well as automated methods have yet to achieve qualitative whole-life analysis of C. elegans longevity based on intrapopulation variation. Here, we utilized live-cell analysis system to determine the parameters of nematode lifespans. Image-based superposition method enabled to determine not only frailty in worms, but also to measure individual and longitudinal lifespan, healthspan, and frailspan. Notably, k-means clustering via principal component analysis revealed four clusters with distinct longevity patterns in wild-type C. elegans. Physiological relevance of clustering was confirmed by assays with pharmacological and/or genetic manipulation of AMP-activated protein kinase (AMPK), a crucial regulator of healthspan. Finally, we focused on W09D10.4 among the possible regulators extracted by integrative expression analysis with existing data sets. Importantly, W09D10.4 knockdown increased the high-healthspan populations only in the presence of AMPK, suggesting that W09D10.4 is a novel AMPK-associated healthspan shortening factor in C. elegans. Overall, the study establishes a novel platform of longitudinal lifespan in C. elegans, which is user-friendly, and may be a useful pharmacological tool to identify healthspan modulatory factors.

The Resistance of Drosophila melanogaster to Oxidative, Genotoxic, Proteotoxic, Osmotic Stress, Infection, and Starvation Depends on Age According to the Stress Factor

We studied how aging affects the ability of Drosophila melanogaster to tolerate various types of stress factors. Data were obtained on the resistance of D. melanogaster to oxidative and genotoxic (separately paraquat, Fe³⁺, Cu²⁺, and Zn²⁺ ions), proteotoxic (hyperthermia, Cd²⁺ ions), and osmotic (NaCl) stresses, starvation, and infection with the pathological Beauveria bassiana fungus at different ages. In all cases, we observed a strong negative correlation between age and stress tolerance. The largest change in the age-dependent decline in survival occurred under oxidative and osmotic stress. In most experiments, we observed that young Drosophila females have higher stress resistance than males. We checked whether it is possible to accurately assess the biological age of D. melanogaster based on an assessment of stress tolerance. We have proposed a new approach for assessing a biological age of D. melanogaster using a two-parameter survival curve model. For the model, we used an algorithm that evaluated the quality of age prediction for different age and gender groups. The best predictions were obtained for females who were exposed to CdCl₂ and ZnCl₂ with an average error of 0.32 days and 0.36 days, respectively. For males, the best results were observed for paraquat and NaCl with an average error of 0.61 and 0.68 days, respectively. The average accuracy for all stresses in our model was 1.73 days.

Innovations in Geroscience to enhance mobility in older adults

Aging is the primary risk factor for functional decline; thus, understanding and preventing disability among older adults has emerged as an important public health challenge of the 21st century. The science of gerontology - or geroscience - has the practical purpose of "adding life to the years." The overall goal of geroscience is to increase healthspan, which refers to extending the portion of the lifespan in which the individual experiences enjoyment, satisfaction, and wellness. An important facet of this goal is preserving mobility, defined as the ability to move independently. Despite this clear purpose, this has proven to be a challenging endeavor as mobility and function in later life are influenced by a complex interaction of factors across multiple domains. Moreover, findings over the past decade have highlighted the complexity of walking and how targeting multiple systems, including the brain and sensory organs, as well as the environment in which a person lives, can have a dramatic effect on an older person's mobility and function. For these reasons, behavioral interventions that incorporate complex walking tasks and other activities of daily living appear to be especially helpful for improving mobility function. Other pharmaceutical interventions, such as oxytocin, and complementary and alternative interventions, such as massage therapy, may enhance physical function both through direct effects on biological mechanisms related to mobility, as well as indirectly through modulation of cognitive and socioemotional processes. Thus, the purpose of the present review is to describe evolving interventional approaches to enhance mobility and maintain healthspan in the growing population of older adults in the United States and countries throughout the world. Such interventions are likely to be greatly assisted by technological advances and the widespread adoption of virtual communications during and after the COVID-19 era.

Autophagy Plays a Role in the Prolongation of the Life Span of Caenorhabditis elegans by Astaxanthin

Astaxanthin (AST), a xanthophyll belonging to the family of carotenoids, is a potent antioxidant. The effect of AST on longevity and its physiological and molecular mechanism are still unclear. In this study, we proved that AST could prolong the life span of Caenorhabditis elegans. To uncover whether AST could delay aging by upregulating autophagy, we measured the expression of autophagy gene and the life span of autophagy gene bec-1 mutant nematodes, and the results showed that the expression of autophagy gene was upregulated after AST intervention and the disruption of bec-1 weakened the extension of the life span. To explore the molecular mechanism of AST-induced autophagy upregulation, we knocked out the daf-16 or hlh-30 (key genes of insulin/insulin growth factor-1 [IGF-1] signal pathway or target of rapamycin [TOR] signal pathway) by RNA interference, and the expression of autophagy gene lgg-1 decreased. Collectively, our results strongly suggest that autophagy, which is both the insulin/IGF-1 signal pathway dependent and TOR signal pathway dependent, plays a role in the prolongation of the life span of Caenorhabditis elegans by AST.

Inhibition of PAR-1 delays aging via activating AMPK in C. elegans

The antagonistic pleiotropy theory of aging suggests that genes essential for growth and development are likely to modulate aging later in life. Previous studies in C. elegans demonstrate that inhibition of certain developmentally essential genes during adulthood leads to significant lifespan extension. PAR-1, a highly conserved serine/threonine kinase, functions as a key cellular polarity regulator during the embryonic development. However, the role of PAR-1 during adulthood remains unknown. Here we show that inhibition of par-1 either by a temperature-sensitive mutant or by RNAi knockdown only during adulthood is sufficient to extend lifespan in C. elegans. Inhibition of par-1 also improves healthspan, as indicated by increased stress resistance, enhanced proteotoxicity resistance, as well as reduced muscular function decline over time. Additionally, tissue-enriched RNAi knockdown analysis reveals that PAR-1 mainly functions in the epidermis to regulate lifespan. Further genetic epistatic and molecular studies demonstrate that the effect of par-1 on lifespan requires the AMP-activated protein kinase (AMPK), and RNAi knockdown of par-1 results in age-dependent AMPK activation and reduced lipid accumulation in the metabolic tissue. Taken together, our findings reveal a previously undescribed function of PAR-1 in adulthood, which will help to understand the molecular links between development and aging.

Generating synthetic aging trajectories with a weighted network model using cross-sectional data

We develop a computational model of human aging that generates individual health trajectories with a set of observed health attributes. Our model consists of a network of interacting health attributes that stochastically damage with age to form health deficits, leading to eventual mortality. We train and test the model for two different cross-sectional observational aging studies that include simple binarized clinical indicators of health. In both studies, we find that cohorts of simulated individuals generated from the model resemble the observed cross-sectional data in both health characteristics and mortality. We can generate large numbers of synthetic individual aging trajectories with our weighted network model. Predicted average health trajectories and survival probabilities agree well with the observed data.

Inhibition of mTOR decreases insoluble proteins burden by reducing translation in C. elegans

Aging animals accumulate insoluble proteins as a consequence of a decline of proteostatic maintenance with age. In Caenorhabditis elegans, for instance, levels of detergent-insoluble proteins increase with age. In longer-lived strains of C. elegans, this accumulation occurs more slowly, implying a link to lifespan determination. We further explored this link and found that detergent-insoluble proteins accumulate more rapidly at higher temperatures, a condition where lifespan is short. We employed a C. elegans strain carrying a GFP transcriptional reporter under the control of a heat shock (hsp-16.2) promoter to investigate the dynamics of proteostatic failure in individual nematodes. We found that early, sporadic activation of hsp-16.2 was predictive of shorter remaining lifespan in individual nematodes. Exposure to rapamycin, resulting in reduced mTOR signaling, delayed spurious expression, extended lifespan, and delayed accumulation of insoluble proteins, suggesting that targets downstream of the mTOR pathway regulate the accumulation of insoluble proteins. We specifically explored ribosomal S6 kinase (rsks-1) as one such candidate and found that RNAi against rsks-1 also resulted in less age-dependent accumulation of insoluble proteins and extended lifespan. Our results demonstrate that inhibition of protein translation via reduced mTOR signaling resulted in slower accumulation of insoluble proteins, delayed proteostatic crisis, and extended lifespan in C. elegans.

Effects of ethyl acetate fractional extract from Portulaca oleracea L. (PO-EA) on lifespan and healthspan in Caenorhabditis elegans

Portulaca oleracea L. (PO), with abundant natural bioactive phytochemicals, exhibits potential bioactivities and pharmacological activities. However, the mechanisms of action of PO on anti-aging effect remain unclear. In this study, the ethyl acetate fractional extract from PO (PO-EA) was obtained by fractionation of solvent extractions, and its effect on lifespan was assessed using the Caenorhabditis elegans (C. elegans). Results showed that PO-EA could significantly increase the lifespan of C. elegans by 5.31, 12.67, and 16.47% at the doses of 250, 500, and 1,000 µg/mL, respectively. Moreover, PO-EA significantly promoted the mobility of C. elegans without obvious side effects such as changing body length or decreasing fecundity of the nematodes. Further study demonstrated that PO-EA could enhance the stress resistance in C. elegans via improving the activities of superoxide dismutase and catalase, and diminishing the contents of reactive oxygen species and malondialdehyde. The gene expression of daf-12, daf-16, sod-3, skn-1, cat-1, mev-1, akt-1, and sek-1 were upregulated in C. elegans after administrated by PO-EA. This study indicated that PO-EA plays a vital role in extending lifespan and healthspan in C. elegans, and the underlying mechanism of action might be attributed to Insulin/IGF-1-like signaling pathways. Therefore, PO-EA could be served as a potential candidate for anti-aging functional food. PRACTICAL APPLICATION: Portulaca oleracea L. (PO) is an edible vegetable that could be used as functional food to exert health benefits for humans such as neuroprotective, antioxidant, anticancer, and anti-aging effects. Therefore, our findings would provide a strategy to promote the comprehensive utilization of ethyl acetate extract from PO with additional health benefits.

Tissue-disruption-induced cellular stochasticity and epigenetic drift: Common origins of aging and cancer?

Age-related and cancer-related epigenomic modifications have been associated with enhanced cell-to-cell gene expression variability that characterizes increased cellular stochasticity. Since gene expression variability appears to be highly reduced by-and epigenetic and phenotypic stability acquired through-direct or long-range cellular interactions during cell differentiation, we propose a common origin for aging and cancer in the failure to control cellular stochasticity by cell-cell interactions. Tissue-disruption-induced cellular stochasticity associated with epigenetic drift would be at the origin of organ dysfunction because of an increase in phenotypic variation among cells, ultimately leading to cell death and organ failure through a loss of coordination in cellular functions, and eventually to cancerization. We propose mechanistic research perspectives to corroborate this hypothesis and explore its evolutionary consequences, highlighting a positive correlation between the median age of mass loss onset (a proxy for the onset of organ aging) and the median age at cancer diagnosis.

Reducing Results Variance in Lifespan Machines: An Analysis of the Influence of Vibrotaxis on Wild-Type Caenorhabditis elegans for the Death Criterion

Nowadays, various artificial vision-based machines automate the lifespan assays of C. elegans. These automated machines present wider variability in results than manual assays because in the latter worms can be poked one by one to determine whether they are alive or not. Lifespan machines normally use a “dead or alive criterion” based on nematode position or pose changes, without poking worms. However, worms barely move on their last days of life, even though they are still alive. Therefore, a long monitoring period is necessary to observe motility in order to guarantee worms are actually dead, or a stimulus to prompt worm movement is required to reduce the lifespan variability measure. Here, a new automated vibrotaxis-based method for lifespan machines is proposed as a solution to prompt a motion response in all worms cultured on standard Petri plates in order to better distinguish between live and dead individuals. This simple automated method allows the stimulation of all animals through the whole plate at the same time and intensity, increasing the experiment throughput. The experimental results exhibited improved live-worm detection using this method, and most live nematodes (>93%) reacted to the vibration stimulus. This method increased machine sensitivity by decreasing results variance by approximately one half (from ±1 individual error per plate to ±0.6) and error in lifespan curve was reduced as well (from 2.6% to 1.2%).

Potential of Caenorhabditis elegans as an antiaging evaluation model for dietary phytochemicals: A review

Aging is an inevitable process characterized by the accumulation of degenerative damage, leading to serious diseases that affect human health. Studies on aging aim to develop pre-protection or therapies to delay aging and age-related diseases. A preventive approach is preferable to clinical treatment not only to reduce investment but also to alleviate pain in patients. Adjusting daily diet habits to improve the aging condition is a potentially attractive strategy. Fruits and vegetables containing active compounds that can effectively delay the aging process and reduce or inhibit age-related degenerative diseases have been identified. The signaling pathways related to aging in Caenorhabditis elegans are evolutionarily conserved; thus, studying antiaging components by intervening senescence process may contribute to the prevention and treatment of age-related diseases in humans. This review focuses on the effects of food-derived extracts or purified substance on antiaging in nematodes, as well as the underlying mechanisms, on the basis of several major signaling pathways and key regulatory factors in aging. The aim is to provide references for a healthy diet guidance and the development of antiaging nutritional supplements. Finally, challenges in the use of C. elegans as the antiaging evaluation model are discussed, together with the development that potentially inspire novel strategies and research tools.

Animal models of sarcopenia

Sarcopenia is the age-related decline in muscle mass and function without any underlying disease. The exact molecular mechanisms responsible for this pathology remain unknown. The use of model organisms, such as mice, rats, flies, and worms, has advanced the field of sarcopenia research by identifying therapeutic strategies and genetic mutations that result in improved muscle mass and function of elderly animals. This review discusses molecular and therapeutic discoveries made using these model organisms and how these animals can be further utilized to better understand sarcopenia pathogenesis. In rodents, flies, and worms, dietary restriction improves muscle performance in old animals. In rodents and worms, exercise and a number of naturally occurring compounds alleviate sarcopenia. Reduction in the insulin/IGF1 receptor pathway, well known to promote longevity, improves sarcopenia in worms and flies. Mitochondrial dysfunction may contribute to the pathogenesis of sarcopenia: In rodents, there is age-dependent reduction in mitochondrial mass and a change in morphology; in nematodes, there is age-dependent fragmentation of mitochondria that precedes sarcomeric disorganization. In Drosophila and rats, components of the 26S proteasome are elevated in aged muscle. An advantage of the worm and fly models is that these organisms lack muscle stem cells, and thus processes that promote the maintenance of already assembled muscle, can be identified without the confounding influence of muscle regeneration. Zebrafish are an up and coming model of sarcopenia for future consideration. A better understanding of the molecular changes behind sarcopenia will help researchers develop better therapies to improve the muscle health of elderly individuals.

Muscle-Specific Lipid Hydrolysis Prolongs Lifespan through Global Lipidomic Remodeling

A growing body of evidence suggests that changes in fat metabolism may have a significant effect on lifespan. Accumulation of lipid deposits in non-adipose tissue appears to be critical for age-related pathologies and may also contribute to the aging process itself. We established a model of lipid storage in muscle cells of C. elegans to reveal a mechanism that promotes longevity non-cell-autonomously. Here, we describe how muscle-specific activation of adipose triglyceride lipase (ATGL) and the phospholipase A₂ (PLA₂) ortholog IPLA-7 collectively affect inter-tissular communication and systemic adaptation that requires the activity of AMP-dependent protein kinase (AMPK) and a highly conserved nuclear receptor outside of the muscle. Our data suggest that muscle-specific bioactive lipid signals, or "lipokines," are generated following triglyceride breakdown and that these signals impinge on a complex network of genes that modify the global lipidome, consequently extending the lifespan.

Improved Human Age Prediction by Using Gene Expression Profiles From Multiple Tissues

Studying transcriptome chronological change from tissues across the whole body can provide valuable information for understanding aging and longevity. Although there has been research on the effect of single-tissue transcriptomes on human aging or aging in mice across multiple tissues, the study of human body-wide multi-tissue transcriptomes on aging is not yet available. In this study, we propose a quantitative model to predict human age by using gene expression data from 46 tissues generated by the Genotype-Tissue Expression (GTEx) project. Specifically, the biological age of a person is first predicted via the gene expression profile of a single tissue. Then, we combine the gene expression profiles from two tissues and compare the predictive accuracy between single and two tissues. The best performance as measured by the root-mean-square error is 3.92 years for single tissue (pituitary), which deceased to 3.6 years when we combined two tissues (pituitary and muscle) together. Different tissues have different potential in predicting chronological age. The prediction accuracy is improved by combining multiple tissues, supporting that aging is a systemic process involving multiple tissues across the human body.

Deep learning-enabled analysis reveals distinct neuronal phenotypes induced by aging and cold-shock

BACKGROUND

Access to quantitative information is crucial to obtain a deeper understanding of biological systems. In addition to being low-throughput, traditional image-based analysis is mostly limited to error-prone qualitative or semi-quantitative assessment of phenotypes, particularly for complex subcellular morphologies. The PVD neuron in Caenorhabditis elegans, which is responsible for harsh touch and thermosensation, undergoes structural degeneration as nematodes age characterized by the appearance of dendritic protrusions. Analysis of these neurodegenerative patterns is labor-intensive and limited to qualitative assessment.

RESULTS

In this work, we apply deep learning to perform quantitative image-based analysis of complex neurodegeneration patterns exhibited by the PVD neuron in C. elegans. We apply a convolutional neural network algorithm (Mask R-CNN) to identify neurodegenerative subcellular protrusions that appear after cold-shock or as a result of aging. A multiparametric phenotypic profile captures the unique morphological changes induced by each perturbation. We identify that acute cold-shock-induced neurodegeneration is reversible and depends on rearing temperature and, importantly, that aging and cold-shock induce distinct neuronal beading patterns.

CONCLUSION

The results of this work indicate that implementing deep learning for challenging image segmentation of PVD neurodegeneration enables quantitatively tracking subtle morphological changes in an unbiased manner. This analysis revealed that distinct patterns of morphological alteration are induced by aging and cold-shock, suggesting different mechanisms at play. This approach can be used to identify the molecular components involved in orchestrating neurodegeneration and to characterize the effect of other stressors on PVD degeneration.

Experimentally induced intrasexual mating competition and sex-specific evolution in female and male nematodes

Sexual dimorphism in life history traits and their trade-offs is widespread among sexually reproducing animals and is strongly influenced by the differences in reproductive strategies between the sexes. We investigated how intrasexual competition influenced specific life history traits, important to fitness and their trade-offs in the outcrossing nematode Caenorhabditis remanei. Here, we altered the strength of sex-specific selection through experimental evolution with increased potential for intrasexual competition by skewing the adult sex ratio towards either females or males (1:10 or 10:1) over 30 generations and subsequently measured the phenotypic response to selection in three traits related to fitness: body size, fecundity and tolerance to heat stress. We observed a greater evolutionary change in females than males for body size and peak fitness, suggesting that females may experience stronger net selection and potentially harbour higher amounts of standing genetic variance compared to males. Our study highlights the importance of investigating direct and indirect effects of intrasexual competition in both sexes in order to capture sex-specific responses and understand the evolution of sexual dimorphism in traits expressed by both sexes.

Tris(1,3-dichloro-2-propyl)phosphate Reduces the Lifespan via Activation of an Unconventional Insulin/Insulin-Like Growth Factor-1 Signaling Pathway

Tris(1,3-dichloro-2-propyl)phosphate (TDCPP) is an environmental contaminant that has attracted increasing concern due to its presence in environmental media and biological samples. Our previous study demonstrated that exposure to TDCPP reduced the lifespan of Caenorhabditis elegans, but the mechanisms, including the relevant signaling pathways, are unclear. The current study found that TDCPP exposure triggers an unconventional insulin/insulin-like growth factor signaling (IIS) pathway, not by disrupting the insulin-like growth factor-1 receptor DAF-2/IGF1R but by inhibiting the downstream tumor-suppressor factor DAF-18/PTEN. This inhibition reduces PI(3,4,5)P₃ (PIP₃) dephosphorylation, causing buildup that increases the activation of the Akt/Protein Kinase B (PKB) family of serine/threonine kinases. This activation induces DAF-16/FoxO phosphorylation and promotes the sequestration of DAF-16/FoxO in the cytoplasm, reducing the lifespan of nematodes. Our results have important diagnostic and therapeutic implications for controlling TDCPP-related diseases, especially those originating with IIS pathway components.

Telomerase and telomeres in aging theory and chronographic aging theory (Review)

The current review focuses on the connection of telomerase and telomeres with aging. In this review, we describe the changes in telomerase and telomere length (TEL) during development, their role in carcinogenesis processes, and the consequences of reduced telomerase activity. More specifically, the connection of TEL in peripheral blood cells with the development of aging‑associated diseases is discussed. The review provides systematic data on the role of telomerase in mitochondria, the biology of telomeres in stem cells, as well as the consequences of the forced expression of telomerase (telomerization) in human cells. Additionally, it presents the effects of chronic stress exposure on telomerase activity, the effect of TEL on fertility, and the effect of nutraceutical supplements on TEL. Finally, a comparative review of the chronographic theory of aging, presented by Olovnikov is provided based on currently available scientific research on telomere, telomerase activity, and the nature of aging by multicellular organisms.

Designing neuroreparative strategies using aged regenerating animal models

In our ever-aging world population, the risk of age-related neuropathies has been increasing, representing both a social and economic burden to society. Since the ability to regenerate in the adult mammalian central nervous system is very limited, brain trauma and neurodegeneration are often permanent. As a consequence, novel scientific challenges have emerged and many research efforts currently focus on triggering repair in the damaged or diseased brain. Nevertheless, stimulating neuroregeneration remains ambitious. Even though important discoveries have been made over the past decades, they did not translate into a therapy yet. Actually, this is not surprising; while these disorders mainly manifest in aged individuals, most of the research is being performed in young animal models. Aging of neurons and their environment, however, greatly affects the central nervous system and its capacity to repair. This review provides a detailed overview of the impact of aging on central nervous system functioning and regeneration potential, both in non-regenerating and spontaneously regenerating animal models. Additionally, we highlight the need for aging animal models with regenerative capacities in the search for neuroreparative strategies.

Antistress and anti-aging activities of Caenorhabditis elegans were enhanced by Momordica saponin extract

BACKGROUND

Momordica saponin extract (MSE) was found to not only improve longevity and neuroprotection but also alleviate fat accumulation in Caenorhabditis elegans in our previous study. However, the lipid-lowering activity of MSE alone could not fully explain its ability to improve health, so the antistress effects of MSE were further studied.

METHODS

Using C. elegans as an in vivo animal, the lifespan of MSE-treated C. elegans under various stressors (H₂O₂, paraquat and heat) and normal conditions was studied. Furthermore, the antioxidant activities of MSE were discussed. To study the underlying mechanisms, the expression of stress resistance genes and the resistance of related mutants to H₂O₂ stress were tested.

RESULTS

MSE significantly improved the lifespan of C. elegans under stress and normal conditions. Meanwhile, the mobility of C. elegans was also improved. Moreover, the activities of SOD and CAT and the ratio of GSH/GSSG were elevated. Consistently, the levels of ROS and lipid oxidation (the NEFA and MDA content) were reduced. Furthermore, MSE treatment upregulated the expression of the sod-3, sod-5, clt-1, clt-2, hsp-16.1 and hsp-16.2 genes. All biomarkers indicated that the antistress and anti-aging activities of MSE were due to its strong antioxidant activities. Finally, MSE induced nuclear DAF-16::GFP localization. Studies with mutants revealed that skn-1 and hsf-1 were involved in the activity of MSE, which might upregulate the expression of downstream stress-responsive genes.

CONCLUSIONS

Therefore, in addition to its lipid-lowering property, the ability of MSE to improve healthspan was also attributed to the stress resistance effect. Together, MSE might serve as a lead nutraceutical in geriatric research.

Short-term enhancement of motor neuron synaptic exocytosis during early aging extends lifespan in Caenorhabditis elegans

IMPACT STATEMENT

The functional decline of motor activity is a common feature in almost all aging animals that leads to frailty, loss of independence, injury, and even death in the elderly population. Thus, understanding the molecular mechanism that drives the initial stage of this functional decline and developing strategies to increase human healthspan and even lifespan by targeting this process would be of great interests to the field. In this study, we found that by precisely targeting the motor neurons to potentiate its synaptic releases either genetically or pharmacologically, we can not only delay the functional aging at NMJs but also slow the rate of aging at the organismal level. Most importantly, we have demonstrated that a critical window of time, that is the early stage of NMJs functional decline, is required for the beneficial effects. A short-term treatment within this time period is sufficient to extend the animals' lifespan.

Gluconeogenesis and PEPCK are critical components of healthy aging and dietary restriction life extension

High glucose diets are unhealthy, although the mechanisms by which elevated glucose is harmful to whole animal physiology are not well understood. In Caenorhabditis elegans, high glucose shortens lifespan, while chemically inflicted glucose restriction promotes longevity. We investigated the impact of glucose metabolism on aging quality (maintained locomotory capacity and median lifespan) and found that, in addition to shortening lifespan, excess glucose negatively impacts locomotory healthspan. Conversely, disrupting glucose utilization by knockdown of glycolysis-specific genes results in large mid-age physical improvements via a mechanism that requires the FOXO transcription factor DAF-16. Adult locomotory capacity is extended by glycolysis disruption, but maximum lifespan is not, indicating that limiting glycolysis can increase the proportion of life spent in mobility health. We also considered the largely ignored role of glucose biosynthesis (gluconeogenesis) in adult health. Directed perturbations of gluconeogenic genes that specify single direction enzymatic reactions for glucose synthesis decrease locomotory healthspan, suggesting that gluconeogenesis is needed for healthy aging. Consistent with this idea, overexpression of the central gluconeogenic gene pck-2 (encoding PEPCK) increases health measures via a mechanism that requires DAF-16 to promote pck-2 expression in specific intestinal cells. Dietary restriction also features DAF-16-dependent pck-2 expression in the intestine, and the healthspan benefits conferred by dietary restriction require pck-2. Together, our results describe a new paradigm in which nutritional signals engage gluconeogenesis to influence aging quality via DAF-16. These data underscore the idea that promotion of gluconeogenesis might be an unappreciated goal for healthy aging and could constitute a novel target for pharmacological interventions that counter high glucose consequences, including diabetes.

It is known that high levels of dietary sugar can negatively impact human health, but the mechanisms underlying this remain unclear. Here we use the facile Caenorhabditis elegans genetic model to extend understanding of the impact of glucose and glucose metabolism on health and aging. We show that the two opposing glucose metabolism pathways–glycolysis and gluconeogenesis–have dramatically opposite effects on health: glycolytic activity responsible for sugar catabolism is detrimental, but driving gluconeogenesis promotes healthy aging. The powerful longevity regulator DAF-16 is required for the healthspan effects of gluconeogenesis. Our data highlight the intriguing possibility that driving the biosynthetic gluconeogenesis pathway could be a novel strategy for healthspan promotion. Indeed, we find that increasing levels of the core gluconeogenic enzyme PEPCK (PCK-2) in just a few intestinal cells can increase overall health in a DAF-16-dependent manner. Dietary restriction, which can promote health and longevity across species, increases PCK-2 levels in the intestine via DAF-16, and PCK-2 is required for the health benefits seen when calories are limited. Our results define gluconeogenic metabolism as a key component of healthy aging, and suggest that interventions that promote gluconeogenesis may help combat the onset of age-related diseases, including diabetes.

Discriminating between sleep and exercise-induced fatigue using computer vision and behavioral genetics

Following prolonged swimming, Caenorhabditis elegans cycle between active swimming bouts and inactive quiescent bouts. Swimming is exercise for C. elegans and here we suggest that inactive bouts are a recovery state akin to fatigue. It is known that cGMP-dependent kinase (PKG) activity plays a conserved role in sleep, rest, and arousal. Using C. elegans EGL-4 PKG, we first validate a novel learning-based computer vision approach to automatically analyze C. elegans locomotory behavior and an edge detection program that is able to distinguish between activity and inactivity during swimming for long periods of time. We find that C. elegans EGL-4 PKG function impacts timing of exercise-induced quiescent (EIQ) bout onset, fractional quiescence, bout number, and bout duration, suggesting that previously described pathways are engaged during EIQ bouts. However, EIQ bouts are likely not sleep as animals are feeding during the majority of EIQ bouts. We find that genetic perturbation of neurons required for other C. elegans sleep states also does not alter EIQ dynamics. Additionally, we find that EIQ onset is sensitive to age and DAF-16 FOXO function. In summary, we have validated behavioral analysis software that enables a quantitative and detailed assessment of swimming behavior, including EIQ. We found novel EIQ defects in aged animals and animals with mutations in a gene involved in stress tolerance. We anticipate that further use of this software will facilitate the analysis of genes and pathways critical for fatigue and other C. elegans behaviors.

Host-microbe interactions and the behavior of Caenorhabditis elegans

Microbes are ubiquitous in the natural environment of Caenorhabditis elegans. Bacteria serve as a food source for C. elegans but may also cause infection in the nematode host. The sensory nervous system of C. elegans detects diverse microbial molecules, ranging from metabolites produced by broad classes of bacteria to molecules synthesized by specific strains of bacteria. Innate recognition through chemosensation of bacterial metabolites or mechanosensation of bacteria can induce immediate behavioral responses. The ingestion of nutritive or pathogenic bacteria can modulate internal states that underlie long-lasting behavioral changes. Ingestion of nutritive bacteria leads to learned attraction and exploitation of the bacterial food source. Infection, which is accompanied by activation of innate immunity, stress responses, and host damage, leads to the development of aversive behavior. The integration of a multitude of microbial sensory cues in the environment is shaped by experience and context. Genetic, chemical, and neuronal studies of C. elegans behavior in the presence of bacteria have defined neural circuits and neuromodulatory systems that shape innate and learned behavioral responses to microbial cues. These studies have revealed the profound influence that host-microbe interactions have in governing the behavior of this simple animal host.

Multidimensional phenotyping predicts lifespan and quantifies health in Caenorhabditis elegans

Ageing affects a wide range of phenotypes at all scales, but an objective measure of ageing remains challenging, even in simple model organisms. To measure the ageing process, we characterized the sequence of alterations of multiple phenotypes at organismal scale. Hundreds of morphological, postural, and behavioral features were extracted from high-resolution videos. Out of the 1019 features extracted, 896 are ageing biomarkers, defined as those that show a significant correlation with relative age (age divided by lifespan). We used support vector regression to predict age, remaining life and lifespan of individual C. elegans. The quality of these predictions (age R2 = 0.79; remaining life R2 = 0.77; lifespan R2 = 0.72) increased with the number of features added to the model, supporting the use of multiple features to quantify ageing. We quantified the rate of ageing as how quickly animals moved through a phenotypic space; we quantified health decline as the slope of the declining predicted remaining life. In both ageing dimensions, we found that short lived-animals aged faster than long-lived animals. In our conditions, for isogenic wild-type worms, the health decline of the individuals was scaled to their lifespan without significant deviation from the average for short- or long-lived animals.

Lifespan and healthspan benefits of exogenous H2S in C. elegans are independent from effects downstream of eat-2 mutation

Caloric restriction (CR) is one of the most effective interventions to prolong lifespan and promote health. Recently, it has been suggested that hydrogen sulfide (H₂S) may play a pivotal role in mediating some of these CR-associated benefits. While toxic at high concentrations, H₂S at lower concentrations can be biologically advantageous. H₂S levels can be artificially elevated via H₂S-releasing donor drugs. In this study, we explored the function of a novel, slow-releasing H₂S donor drug (FW1256) and used it as a tool to investigate H₂S in the context of CR and as a potential CR mimetic. We show that exposure to FW1256 extends lifespan and promotes health in Caenorhabditis elegans (C. elegans) more robustly than some previous H₂S-releasing compounds, including GYY4137. We looked at the extent to which FW1256 reproduces CR-associated physiological effects in normal-feeding C. elegans. We found that FW1256 promoted healthy longevity to a similar degree as CR but with fewer fitness costs. In contrast to CR, FW1256 actually enhanced overall reproductive capacity and did not reduce adult body length. FW1256 further extended the lifespan of already long-lived eat-2 mutants without further detriments in developmental timing or fertility, but these lifespan and healthspan benefits required H₂S exposure to begin early in development. Taken together, these observations suggest that FW1256 delivers exogenous H₂S efficiently and supports a role for H₂S in mediating longevity benefits of CR. Delivery of H₂S via FW1256, however, does not mimic CR perfectly, suggesting that the role of H₂S in CR-associated longevity is likely more complex than previously described.

Production of YP170 Vitellogenins Promotes Intestinal Senescence in Caenorhabditis elegans

During aging, etiologies of senescence cause multiple pathologies, leading to morbidity and death. To understand aging requires identification of these etiologies. For example, Caenorhabditis elegans hermaphrodites consume their own intestinal biomass to support yolk production, which in later life drives intestinal atrophy and ectopic yolk deposition. Yolk proteins (YPs; vitellogenins) exist as three abundant species: YP170, derived from vit-1–vit-5; and YP115 and YP88, derived from vit-6. Here, we show that inhibiting YP170 synthesis leads to a reciprocal increase in YP115/YP88 levels and vice versa, an effect involving posttranscriptional mechanisms. Inhibiting YP170 production alone, despite increasing YP115/YP88 synthesis, reduces intestinal atrophy as much as inhibition of all YP synthesis, which increases life span. By contrast, inhibiting YP115/YP88 production alone accelerates intestinal atrophy and reduces life span, an effect that is dependent on increased YP170 production. Thus, despite copious abundance of both YP170 and YP115/YP88, only YP170 production is coupled to intestinal atrophy and shortened life span. In addition, increasing levels of YP115/YP88 but not of YP170 increases resistance to oxidative stress; thus, longevity resulting from reduced vitellogenin synthesis is not attributable to oxidative stress resistance.

Biophysical studies of protein misfolding and aggregation in in vivo models of Alzheimer's and Parkinson's diseases

Neurodegenerative disorders, including Alzheimer's (AD) and Parkinson's diseases (PD), are characterised by the formation of aberrant assemblies of misfolded proteins. The discovery of disease-modifying drugs for these disorders is challenging, in part because we still have a limited understanding of their molecular origins. In this review, we discuss how biophysical approaches can help explain the formation of the aberrant conformational states of proteins whose neurotoxic effects underlie these diseases. We discuss in particular models based on the transgenic expression of amyloid-β (Aβ) and tau in AD, and α-synuclein in PD. Because biophysical methods have enabled an accurate quantification and a detailed understanding of the molecular mechanisms underlying protein misfolding and aggregation in vitro, we expect that the further development of these methods to probe directly the corresponding mechanisms in vivo will open effective routes for diagnostic and therapeutic interventions.

The acute transcriptional response to resistance exercise: impact of age and contraction mode

Optimization of resistance exercise (RE) remains a hotbed of research for muscle building and maintenance. However, the interactions between the contractile components of RE (i.e. concentric (CON) and eccentric (ECC)) and age, are poorly defined. We used transcriptomics to compare age-related molecular responses to acute CON and ECC exercise. Eight young (21±1 y) and eight older (70±1 y) exercise-naïve male volunteers had vastus lateralis biopsies collected at baseline and 5 h post unilateral CON and contralateral ECC exercise. RNA was subjected to next-generation sequencing and differentially expressed (DE) genes tested for pathway enrichment using Gene Ontology (GO). The young transcriptional response to CON and ECC was highly similar and older adults displayed moderate contraction-specific profiles, with no GO enrichment. Age-specific responses to ECC revealed 104 DE genes unique to young, and 170 DE genes in older muscle, with no GO enrichment. Following CON, 15 DE genes were young muscle-specific, whereas older muscle uniquely expressed 147 up-regulated genes enriched for cell adhesion and blood vessel development, and 28 down-regulated genes involved in mitochondrial respiration, amino acid and lipid metabolism. Thus, older age is associated with contraction-specific regulation often without clear functional relevance, perhaps reflecting a degree of stochastic age-related dysregulation.

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.

Longitudinal assessment of health-span and pre-death morbidity in wild type Drosophila

The increase in human life expectancy is accompanied by age-related cognitive and motor disability, thus raising the demand for strategies toward healthy aging. This requires understanding the biology of normal aging and late-life functional phenotypes. Genetic model organisms, such as Drosophila melanogaster, can help identifying evolutionary conserved mechanisms underlying aging. Longitudinal assessment of motor performance of more than 1000 individual flies revealed age-related motor performance decline and specific late-life motor disabilities. This allows defining heath- and ill-span and scoring late-life quality of individual flies. As in mammals, including humans, onset, duration, severity, and progression dynamics of decline are heterogenic and characterized by both, progressive worsening and sudden late-life events. Flies either become increasingly incapacitated by accumulating disability over multiple days prior to death, or they escape disability until few hours prior to death. Both late-life trajectories converge into a terminal stage characterized by stereotypical signs of functional collapse and death within 3 hours. Drosophila can now be used to evaluate life prolonging manipulations in the context of late-life quality. High sugar diet increases lifespan and late-life quality, whereas lifespan prolonging antioxidant supplementation has either no, or negative effects on late-life quality, depending on base diet and gender.

Tart Cherry Increases Lifespan in Caenorhabditis elegans by Altering Metabolic Signaling Pathways

Aging and healthspan are determined by both environmental and genetic factors. The insulin/insulin-like growth factor-1(IGF-1) pathway is a key mediator of aging in Caenorhabditis elegans and mammals. Specifically, DAF-2 signaling, an ortholog of human IGF, controls DAF-16/FOXO transcription factor, a master regulator of metabolism and longevity. Moreover, mitochondrial dysfunction and oxidative stress are both linked to aging. We propose that daily supplementation of tart cherry extract (TCE), rich in anthocyanins with antioxidant properties may exert dual benefits for mitochondrial function and oxidative stress, resulting in beneficial effects on aging in C. elegans. We found that TCE supplementation at 6 μg or 12 μg/mL, increased (p < 0.05) the mean lifespan of wild type N2 worms, respectively, when compared to untreated control worms. Consistent with these findings, TCE upregulated (p < 0.05) expression of longevity-related genes such as daf-16 and aak-2 (but not daf-2 or akt-1 genes) and genes related to oxidative stress such as sod-2. Further, we showed that TCE supplementation increased spare respiration in N2 worms. However, TCE did not change the mean lifespan of daf-16 and aak-2 mutant worms. In conclusion, our findings indicate that TCE confers healthspan benefits in C. elegans through enhanced mitochondrial function and reduced oxidative stress, mainly via the DAF-16 pathway.