Measurements of age-related changes of physiological processes that predict lifespan of Caenorhabditis elegans

Mulberry leaf polyphenols delay aging and regulate fat metabolism via the germline signaling pathway in Caenorhabditis elegans

Mulberry leaves are an important ingredient in some traditional Chinese medicinal formulas and has been developed for use in functional food products. The antioxidant activity of mulberry leaf extract has been reported to have beneficial effects on diseases in vitro; however, it is not clear which components in mulberry leaf extracts have these functions. Furthermore, the mechanisms of action of these ingredients have not been extensively investigated. In this study, we extracted total mulberry leaf polyphenols (MLP) and identified its 13 phenolic monomers. Our results, using Caenorhabditis elegans as a model, indicated that MLPs delayed aging, improved oxidative stress resistance, and reduced fatty acid storage in vivo. Subsequent genetic screens and gene expression analyses demonstrated that the functions of MLP mainly depended on the germline signaling pathway, thus influencing the activities of downstream transcription factors (DAF-12, DAF-16, PHA-4, and NHR-80) as well as the expression levels of their target genes (fat-6, lipl-4, sod-3, unc-51, and fard-1). Our study determined that diverse modes of action on longevity were promoted by MLP exposure. These observations provide the first insight into MLP's multifaceted functions on aging, fat accumulation, and reproduction in vivo and indicate a specific model for the mechanism of action of MLP. This is a significant finding that lends support to the hypotheses that mulberry leaf extracts can have an impact on human health.

Effect of nanoparticles on the biochemical and behavioral aging phenotype of the nematode Caenorhabditis elegans

Invertebrate animal models such as the nematode Caenorhabditis elegans (C. elegans) are increasingly used in nanotechnological applications. Research in this area covers a wide range from remote control of worm behavior by nanoparticles (NPs) to evaluation of organismal nanomaterial safety. Despite of the broad spectrum of investigated NP-bio interactions, little is known about the role of nanomaterials with respect to aging processes in C. elegans. We trace NPs in single cells of adult C. elegans and correlate particle distribution with the worm's metabolism and organ function. By confocal microscopy analysis of fluorescently labeled NPs in living worms, we identify two entry portals for the uptake of nanomaterials via the pharynx to the intestinal system and via the vulva to the reproductive system. NPs are localized throughout the cytoplasm and the cell nucleus in single intestinal, and vulval B and D cells. Silica NPs induce an untimely accumulation of insoluble ubiquitinated proteins, nuclear amyloid and reduction of pharyngeal pumping that taken together constitute a premature aging phenotype of C. elegans on the molecular and behavioral level, respectively. Screening of different nanomaterials for their effects on protein solubility shows that polystyrene or silver NPs do not induce accumulation of ubiquitinated proteins suggesting that alteration of protein homeostasis is a unique property of silica NPs. The nematode C. elegans represents an excellent model to investigate the effect of different types of nanomaterials on aging at the molecule, cell, and whole organism level.

A systems analysis of age-related changes in some cardiac aging traits

Aging process or senescence affects the expression of a wide range of phenotypic traits throughout the life span of organisms. These traits often show modular, synergistic, and even antagonistic relationships, and are also influenced by genomic, developmental, physiological and environmental factors. The cardiovascular system (CVS) in humans represents a major modular system in which the relationships among physiological, anatomical and morphological traits undergo continuous remodeling throughout the life span of an individual. Here we extend the concept of developmental plasticity in order to study the relationships among 14 traits measured on 3,412 individuals from the Framingham Heart Study cohort, relative to age and gender, using exploratory structural equation modeling-a form of systems analysis. Our results reveal differing patterns of association among cardiac traits in younger and older persons in both sexes, indicating that physiological and developmental factors may be channeled differentially in relation to age and gender during the remodeling process. We suggest that systems approaches are necessary in order to understand the coordinated functional relationships among traits of the CVS over the life course of individuals.

Neuronal aging: learning from C. elegans

The heterogeneity and multigenetic nature of nervous system aging make modeling of it a formidable task in mammalian species. The powerful genetics, simple anatomy and short life span of the nematode Caenorhabditis elegans offer unique advantages in unraveling the molecular genetic network that regulates the integrity of neuronal structures and functions during aging. In this review, we first summarize recent breakthroughs in the morphological and functional characterization of C. elegans neuronal aging. Age-associated morphological changes include age-dependent neurite branching, axon beading or swelling, axon defasciculation, progressive distortion of the neuronal soma, and early decline in presynaptic release function. We then discuss genetic pathways that modulate the speed of neuronal aging concordant with alteration in life span, such as insulin signaling, as well as cell-autonomous factors that promote neuronal integrity during senescence, including membrane activity and JNK/MAPK signaling. As a robust genetic model for aging, insights from C. elegans neuronal aging studies will contribute to our mechanistic understanding of human brain aging.

Mated progeny production is a biomarker of aging in Caenorhabditis elegans

The relationships between reproduction and aging are important for understanding the mechanisms of aging and evaluating evolutionary theories of aging. To investigate the effects of progeny production on reproductive and somatic aging, we conducted longitudinal studies of Caenorhabditis elegans hermaphrodites. For mated wild-type animals that were not sperm limited and survived past the end of the reproductive period, high levels of cross-progeny production were positively correlated with delayed reproductive and somatic aging. In this group of animals, individuals that generated more cross progeny also reproduced and lived longer than individuals that generated fewer cross progeny. These results indicate that progeny production does not accelerate reproductive or somatic aging. This longitudinal study demonstrated that cumulative cross progeny production through day four is an early-stage biomarker that is a positive predictor of longevity. Furthermore, in mated animals, high levels of early cross progeny production were positively correlated with high levels of late cross progeny production, indicating that early progeny production does not accelerate reproductive aging. The relationships between progeny production and aging were further evaluated by comparing self-fertile hermaphrodites that generated relatively few self progeny with mated hermaphrodites that generated many cross progeny. The timing of age-related somatic degeneration was similar in these groups, suggesting progeny production does not accelerate somatic aging. These studies rigorously define relationships between progeny production, reproductive aging, and somatic aging and identify new biomarkers of C. elegans aging. These results indicate that some mechanisms or pathways control age-related degeneration of both reproductive and somatic tissues in C. elegans.

Spaceflight and ageing: reflecting on Caenorhabditis elegans in space

The prospect of space travel continues to capture the imagination. Several competing companies are now promising flights for the general population. Previously, it was recognized that many of the physiological changes that occur with spaceflight are similar to those seen with normal ageing. This led to the notion that spaceflight can be used as a model of accelerated ageing and raised concerns about the safety of individuals engaging in space travel. Paradoxically, however, space travel has been recently shown to be beneficial to some aspects of muscle health in the tiny worm Caenorhabditis elegans. C. elegans is a commonly used laboratory animal for studying ageing. C. elegans displays age-related decline of some biological processes observed in ageing humans, and about 35% of C. elegans' genes have human homologs. Space flown worms were found to have decreased expression of a number of genes that increase lifespan when expressed at lower levels. These changes were accompanied by decreased accumulation of toxic protein aggregates in ageing worms' muscles. Thus, in addition to spaceflight producing physiological changes that are similar to accelerated ageing, it also appears to produce some changes similar to delayed ageing. Here, we put forward the hypothesis that in addition to the previously well-appreciated mechanotransduction changes, neural and endocrine signals are altered in response to spaceflight and that these may have both negative (e.g. less muscle protein) and some positive consequences (e.g. healthier muscles), at least for invertebrates, with respect to health in space. Given that changes in circulating hormones are well documented with age and in astronauts, our view is that further research into the relationship between metabolic control, ageing, and adaptation to the environment should be productive in advancing our understanding of the physiology of both spaceflight and ageing.

Dramatic fertility decline in aging C. elegans males is associated with mating execution deficits rather than diminished sperm quality

Although much is known about female reproductive aging, fairly little is known about the causes of male reproductive senescence. We developed a method that facilitates culture maintenance of Caenorhabditis elegans adult males, which enabled us to measure male fertility as populations age, without profound loss of males from the growth plate. We find that the ability of males to sire progeny declines rapidly in the first half of adult lifespan and we examined potential factors that contribute towards reproductive success, including physical vigor, sperm quality, mating apparatus morphology, and mating ability. Of these, we find little evidence of general physical decline in males or changes in sperm number, morphology, or capacity for activation, at time points when reproductive senescence is markedly evident. Rather, it is the loss of efficient mating ability that correlates most strongly with reproductive senescence. Low insulin signaling can extend male ability to sire progeny later in life, although insulin impact on individual facets of mating behavior is complex. Overall, we suggest that combined modest deficits, predominantly affecting the complex mating behavior rather than sperm quality, sum up to block effective C. elegans male reproduction in middle adult life.

The longevity effect of cranberry extract in Caenorhabditis elegans is modulated by daf-16 and osr-1

Nutraceuticals are known to have numerous health and disease preventing properties. Recent studies suggest that extracts containing cranberry may have anti-aging benefits. However, little is known about whether and how cranberry by itself promotes longevity and healthspan in any organism. Here we examined the effect of a cranberry only extract on lifespan and healthspan in Caenorhabditis elegans. Supplementation of the diet with cranberry extract (CBE) increased the lifespan in C. elegans in a concentration-dependent manner. Cranberry also increased tolerance of C. elegans to heat shock, but not to oxidative stress or ultraviolet irradiation. In addition, we tested the effect of cranberry on brood size and motility and found that cranberry did not influence these behaviors. Our mechanistic studies indicated that lifespan extension induced by CBE requires the insulin/IGF signaling pathway and DAF-16. We also found that cranberry promotes longevity through osmotic stress resistant-1 (OSR-1) and one of its downstream effectors, UNC-43, but not through SEK-1, a component of the p38 MAP kinase pathway. However, SIR-2.1 and JNK signaling pathways are not required for cranberry to promote longevity. Our findings suggest that cranberry supplementation confers increased longevity and stress resistance in C. elegans through pathways modulated by daf-16 and osr-1. This study reveals the anti-aging property of widely consumed cranberry and elucidates the underpinning mechanisms.

Functional aging in the nervous system contributes to age-dependent motor activity decline in C. elegans

Aging is characterized by a progressive decline in multiple physiological functions (i.e., functional aging). As animals age, they exhibit a gradual loss in motor activity, but the underlying mechanisms remain unclear. Here we approach this question in C. elegans by functionally characterizing its aging nervous system and muscles. We find that motor neurons exhibit a progressive functional decline, beginning in early life. Surprisingly, body-wall muscles, which were previously thought to undergo functional aging, do not manifest such a decline until mid-late life. Notably, motor neurons first develop a deficit in synaptic vesicle fusion followed by that in quantal size and vesicle docking/priming, revealing specific functional deteriorations in synaptic transmission. Pharmacological stimulation of synaptic transmission can improve motor activity in aged animals. These results uncover a critical role for the nervous system in age-dependent motor activity decline in C. elegans and provide insights into how functional aging occurs in this organism.

Untangling functional declines in the locomotion of aging worms

All physiological functions decline with age, but which changes are primary and which are secondary is not always clear. Liu et al. (2013), examining functional changes in the muscles and motor neurons of C. elegans, suggest that when it comes to locomotion, it is the nervous system that shows earlier age-related deterioration.

Deletion of microRNA-80 activates dietary restriction to extend C. elegans healthspan and lifespan

Caloric/dietary restriction (CR/DR) can promote longevity and protect against age-associated disease across species. The molecular mechanisms coordinating food intake with health-promoting metabolism are thus of significant medical interest. We report that conserved Caenorhabditis elegans microRNA-80 (mir-80) is a major regulator of the DR state. mir-80 deletion confers system-wide healthy aging, including maintained cardiac-like and skeletal muscle-like function at advanced age, reduced accumulation of lipofuscin, and extended lifespan, coincident with induction of physiological features of DR. mir-80 expression is generally high under ad lib feeding and low under food limitation, with most striking food-sensitive expression changes in posterior intestine. The acetyltransferase transcription co-factor cbp-1 and interacting transcription factors daf-16/FOXO and heat shock factor-1 hsf-1 are essential for mir-80(Δ) benefits. Candidate miR-80 target sequences within the cbp-1 transcript may confer food-dependent regulation. Under food limitation, lowered miR-80 levels directly or indirectly increase CBP-1 protein levels to engage metabolic loops that promote DR.

Age-related degeneration of the egg-laying system promotes matricidal hatching in Caenorhabditis elegans

The identification and characterization of age-related degenerative changes is a critical goal because it can elucidate mechanisms of aging biology and contribute to understanding interventions that promote longevity. Here, we document a novel, age-related degenerative change in C. elegans hermaphrodites, an important model system for the genetic analysis of longevity. Matricidal hatching--intra-uterine hatching of progeny that causes maternal death--displayed an age-related increase in frequency and affected ~70% of mated, wild-type hermaphrodites. The timing and incidence of matricidal hatching were largely independent of the levels of early and total progeny production and the duration of male exposure. Thus, matricidal hatching appears to reflect intrinsic age-related degeneration of the egg-laying system rather than use-dependent damage accumulation. Consistent with this model, mutations that extend longevity by causing dietary restriction significantly delayed matricidal hatching, indicating age-related degeneration of the egg-laying system is controlled by nutrient availability. To identify the underlying tissue defect, we analyzed serotonin signaling that triggers vulval muscle contractions. Mated hermaphrodites displayed an age-related decline in the ability to lay eggs in response to exogenous serotonin, indicating that vulval muscles and/or a further downstream function that is necessary for egg laying degenerate in an age-related manner. By characterizing a new, age-related degenerative event displayed by C. elegans hermaphrodites, these studies contribute to understanding a frequent cause of death in mated hermaphrodites and establish a model of age-related reproductive complications that may be relevant to the birthing process in other animals such as humans.

Mapping the pharyngeal and intestinal pH of Caenorhabditis elegans and real-time luminal pH oscillations using extended dynamic range pH-sensitive nanosensors

Extended dynamic range pH-sensitive ratiometric nanosensors, capable of accurately mapping the full physiological pH range, have been developed and used to characterize the pH of the pharyngeal and intestinal lumen of Caenorhabditis elegans in real-time. Nanosensors, 40 nm in diameter, were prepared by conjugating pH-sensitive fluorophores, carboxyfluorescein (FAM) and Oregon Green (OG) in a 1:1 ratio, and a reference fluorophore, 5-(and-6)-carboxytetramethylrhodamine (TAMRA) to an inert polyacrylamide matrix. Accurate ratiometric pH measurements were calculated through determination of the fluorescence ratio between the pH-sensitive and reference fluorophores. Nanosensors were calibrated with an automated image analysis system and validated to demonstrate a pH measurement resolution of ±0.17 pH units. The motility of C. elegans populations, as an indicator for viability, showed nematodes treated with nanosensors, for concentrations ranging from 50.00 to 3.13 mg/mL, were not statistically different to nematodes not challenged with nanosensors up to a period of 4 days (p < 0.05). The nanosensors were also found to remain in the C. elegans lumen >24 h after nanosensor challenge was removed. The pH of viable C. elegans lumen was found to range from 5.96 ± 0.31 in the anterior pharynx to 3.59 ± 0.09 in the posterior intestine. The pharyngeal pumping rate, which dictates the transfer of ingested material from the pharynx to the intestine, was found to be temperature dependent. Imaging C. elegans at 4 °C reduced the pharyngeal pumping rate to 7 contractions/min and enabled the reconstruction of rhythmic pH oscillations in the intestinal lumen in real-time with fluorescence microscopy.

Aging in the nervous system of Caenorhabditis elegans

It has recently been described that aging in C. elegans is accompanied by the progressive development of morphological changes in the nervous system. These include novel outgrowths from the cell body or axonal process, as well as blebbing and beading along the length of the axon. The formation of these structures is regulated by numerous molecular players including members of the well-conserved insulin/insulin growth factor-like (IGF)-1 signaling and mitogen-activated protein (MAP) kinase pathways. This review summarizes the recent literature on neuronal aging in C. elegans, including our own findings, which indicate a role for protein with tau-like repeats (PTL-1), the homolog of mammalian tau and MAP2/4, in maintaining neuronal integrity during aging.

WormFarm: a quantitative control and measurement device toward automated Caenorhabditis elegans aging analysis

Caenorhabditis elegans is a leading model organism for studying the basic mechanisms of aging. Progress has been limited, however, by the lack of an automated system for quantitative analysis of longevity and mean lifespan. To address this barrier, we developed 'WormFarm', an integrated microfluidic device for culturing nematodes. Cohorts of 30-50 animals are maintained throughout their lifespan in each of eight separate chambers on a single WormFarm polydimethylsiloxane chip. Design features allow for automated removal of progeny and efficient control of environmental conditions. In addition, we have developed computational algorithms for automated analysis of video footage to quantitate survival and other phenotypes, such as body size and motility. As proof-of-principle, we show here that WormFarm successfully recapitulates survival data obtained from a standard plate-based assay for both RNAi-mediated and dietary-induced changes in lifespan. Further, using a fluorescent reporter in conjunction with WormFarm, we report an age-associated decrease in fluorescent intensity of GFP in transgenic worms expressing GFP tagged with a mitochondrial import signal under the control of the myo-3 promoter. This marker may therefore serve as a useful biomarker of biological age and aging rate.

Insulin/IGF-1 signaling, including class II/III PI3Ks, β-arrestin and SGK-1, is required in C. elegans to maintain pharyngeal muscle performance during starvation

In C. elegans, pharyngeal pumping is regulated by the presence of bacteria. In response to food deprivation, the pumping rate rapidly declines by about 50–60%, but then recovers gradually to baseline levels on food after 24 hr. We used this system to study the role of insulin/IGF-1 signaling (IIS) in the recovery of pharyngeal pumping during starvation. Mutant strains with reduced function in the insulin/IGF-1 receptor, DAF-2, various insulins (INS-1 and INS-18), and molecules that regulate insulin release (UNC-64 and NCA-1; NCA-2) failed to recover normal pumping rates after food deprivation. Similarly, reduction or loss of function in downstream signaling molecules (e.g., ARR-1, AKT-1, and SGK-1) and effectors (e.g., CCA-1 and UNC-68) impaired pumping recovery. Pharmacological studies with kinase and metabolic inhibitors implicated class II/III phosphatidylinositol 3-kinases (PI3Ks) and glucose metabolism in the recovery response. Interestingly, both over- and under-activity in IIS was associated with poorer recovery kinetics. Taken together, the data suggest that optimum levels of IIS are required to maintain high levels of pharyngeal pumping during starvation. This work may ultimately provide insights into the connections between IIS, nutritional status and sarcopenia, a hallmark feature of aging in muscle.

The Caenorhabditis elegans Lifespan Machine

The measurement of lifespan pervades aging research. Because lifespan results from complex interactions between genetic, environmental and stochastic factors, it varies widely even among isogenic individuals. The actions of molecular mechanisms on lifespan are therefore visible only through their statistical effects on populations. Indeed, survival assays in Caenorhabditis elegans have provided critical insights into evolutionarily conserved determinants of aging. To enable the rapid acquisition of survival curves at an arbitrary statistical resolution, we developed a scalable imaging and analysis platform to observe nematodes over multiple weeks across square meters of agar surface at 8-μm resolution. The automated method generates a permanent visual record of individual deaths from which survival curves are constructed and validated, producing data consistent with results from the manual method of survival curve acquisition for several mutants in both standard and stressful environments. Our approach permits rapid, detailed reverse-genetic and chemical screens for effects on survival and enables quantitative investigations into the statistical structure of aging.

Effect of the tocotrienol-rich fraction on the lifespan and oxidative biomarkers in Caenorhabditis elegans under oxidative stress

OBJECTIVE

This study was performed to determine the effect of the tocotrienol-rich fraction on the lifespan and oxidative status of C. elegans under oxidative stress.

METHOD

Lifespan was determined by counting the number of surviving nematodes daily under a dissecting microscope after treatment with hydrogen peroxide and the tocotrienol-rich fraction. The evaluated oxidative markers included lipofuscin, which was measured using a fluorescent microscope, and protein carbonyl and 8-hydroxy-2'-deoxyguanosine, which were measured using commercially available kits.

RESULTS

Hydrogen peroxide-induced oxidative stress significantly decreased the mean lifespan of C. elegans, which was restored to that of the control by the tocotrienol-rich fraction when administered before or both before and after the hydrogen peroxide. The accumulation of the age marker lipofuscin, which increased with hydrogen peroxide exposure, was decreased with upon treatment with the tocotrienol-rich fraction (p<0.05). The level of 8-hydroxy-2'-deoxyguanosine significantly increased in the hydrogen peroxide-induced group relative to the control. Treatment with the tocotrienol-rich fraction before or after hydrogen peroxide induction also increased the level of 8-hydroxy-2'-deoxyguanosine relative to the control. However, neither hydrogen peroxide nor the tocotrienol-rich fraction treatment affected the protein carbonyl content of the nematodes.

CONCLUSION

The tocotrienol-rich fraction restored the lifespan of oxidative stress-induced C. elegans and reduced the accumulation of lipofuscin but did not affect protein damage. In addition, DNA oxidation was increased.

Pheromone sensing regulates Caenorhabditis elegans lifespan and stress resistance via the deacetylase SIR-2.1

Lifespan in Caenorhabditis elegans, Drosophila, and mice is regulated by conserved signaling networks, including the insulin/insulin-like growth factor 1 (IGF-1) signaling cascade and pathways depending on sirtuins, a family of NAD(+)-dependent deacetylases. Small molecules such as resveratrol are of great interest because they increase lifespan in many species in a sirtuin-dependent manner. However, no endogenous small molecules that regulate lifespan via sirtuins have been identified, and the mechanisms underlying sirtuin-dependent longevity are not well understood. Here, we show that in C. elegans, two endogenously produced small molecules, the dauer-inducing ascarosides ascr#2 and ascr#3, regulate lifespan and stress resistance through chemosensory pathways and the sirtuin SIR-2.1. Ascarosides extend adult lifespan and stress resistance without reducing fecundity or feeding rate, and these effects are reduced or abolished when nutrients are restricted. We found that ascaroside-mediated longevity is fully abolished by loss of SIR-2.1 and that the effect of ascr#2 requires expression of the G protein-coupled receptor DAF-37 in specific chemosensory neurons. In contrast to many other lifespan-modulating factors, ascaroside-mediated lifespan increases do not require insulin signaling via the FOXO homolog DAF-16 or the insulin/IGF-1-receptor homolog DAF-2. Our study demonstrates that C. elegans produces specific small molecules to control adult lifespan in a sirtuin-dependent manner, supporting the hypothesis that endogenous regulation of metazoan lifespan functions, in part, via sirtuins. These findings strengthen the link between chemosensory inputs and conserved mechanisms of lifespan regulation in metazoans and suggest a model for communal lifespan regulation in C. elegans.

Realgar bioleaching solution is a less toxic arsenic agent in suppressing the Ras/MAPK pathway in Caenorhabditis elegans

To explore other arsenic derivatives with anticancer effects and fewer adverse effects, realgar bioleaching solution (RBS) has been found to be a viable approach. Here we used C. elegans as a model organism to its possible efficacy for anti-cancer effect of RBS. Our results indicated that RBS significantly suppressed the multivulva (Muv) phenotype of let-60 ras(gf) mutant that was positive correlated to arsenic concentrations in worms and also inhibited Muv phenotype of lin-15(lf) upstream of Ras/MAPK pathway, but did not affect the Muv phenotype resulting from loss-of-function mutations of lin-l(lf) downstream of Ras/MAPK pathway, which may be mechanism-based. In toxicity tests, RBS did not lead to reduction resulting from arsenic trioxide (ATO) in the number of pharyngeal pumping which was orthologous to vertebrate heart beating in wild type C. elegans. Overall, RBS was likely to be a potential anti-cancer drug candidate with high efficiency and low toxicity.

Roles of the developmental regulator unc-62/Homothorax in limiting longevity in Caenorhabditis elegans

The normal aging process is associated with stereotyped changes in gene expression, but the regulators responsible for these age-dependent changes are poorly understood. Using a novel genomics approach, we identified HOX co-factor unc-62 (Homothorax) as a developmental regulator that binds proximal to age-regulated genes and modulates lifespan. Although unc-62 is expressed in diverse tissues, its functions in the intestine play a particularly important role in modulating lifespan, as intestine-specific knockdown of unc-62 by RNAi increases lifespan. An alternatively-spliced, tissue-specific isoform of unc-62 is expressed exclusively in the intestine and declines with age. Through analysis of the downstream consequences of unc-62 knockdown, we identify multiple effects linked to aging. First, unc-62 RNAi decreases the expression of yolk proteins (vitellogenins) that aggregate in the body cavity in old age. Second, unc-62 RNAi results in a broad increase in expression of intestinal genes that typically decrease expression with age, suggesting that unc-62 activity balances intestinal resource allocation between yolk protein expression and fertility on the one hand and somatic functions on the other. Finally, in old age, the intestine shows increased expression of several aberrant genes; these UNC-62 targets are expressed predominantly in neuronal cells in developing animals, but surprisingly show increased expression in the intestine of old animals. Intestinal expression of some of these genes during aging is detrimental for longevity; notably, increased expression of insulin ins-7 limits lifespan by repressing activity of insulin pathway response factor DAF-16/FOXO in aged animals. These results illustrate how unc-62 regulation of intestinal gene expression is responsible for limiting lifespan during the normal aging process.

Aspirin extends the lifespan of Caenorhabditis elegans via AMPK and DAF-16/FOXO in dietary restriction pathway

Aspirin has been revealed to have many beneficial effects for health since it was discovered as a nonsteroidal anti-inflammatory drug (NSAID) to treat pain and inflammation. Here, we investigated the molecular mechanism of aspirin on the lifespan extension of Caenorhabditis elegans. Our results showed that aspirin could extend the lifespan of C. elegans, and increase its health span and stress resistance. The extension of lifespan by aspirin requires DAF-16/FOXO, AMPK, and LKB1, but not SIR-2.1. Aspirin could not extend the lifespan of the mutants of eat-2, clk-1, and isp-1. Aspirin could marginally extend the lifespan of long-live insulin-like receptor mutant daf-2(e1370) III. Taken together, aspirin might act through a dietary restriction-like mechanism, via increasing the AMP:ATP ratio and activating LKB1, subsequently activating AMPK, which stimulates DAF-16 to induce downstream effects through a DAF-16 translocation independent manner.

Drug absorption efficiency in Caenorhbditis elegans delivered by different methods

BACKGROUND

Caenorhbditis elegans has being vigorously used as a model organism in many research fields and often accompanied by administrating with various drugs. The methods of delivering drugs to worms are varied from one study to another, which make difficult in comparing results between studies.

METHODOLOGY/PRINCIPAL FINDINGS

We evaluated the drug absorption efficiency in C. elegans using five frequently used methods with resveratrol with low aqueous solubility and water-soluble 5-Fluoro-2'-deoxyuridine (FUDR) as positive compounds. The drugs were either applied to the LB medium with bacteria OP50, before spreading onto Nematode Growth Medium (NGM) plates (LB medium method), or to the NGM with live (NGM live method) or dead bacteria (NGM dead method), or spotting the drug solution to the surface of plates directly (spot dead method), or growing the worms in liquid medium (liquid growing method). The concentration of resveratrol and FUDR increased gradually within C. elegans and reached the highest during 12 hours to one day and then decreased slowly. At the same time point, the higher the drug concentration, the higher the metabolism rate. The drug concentrations in worms fed with dead bacteria were higher than with live bacteria at the same time point. Consistently, the drug concentration in medium with live bacteria decreased much faster than in medium with dead bacteria, reach to about half of the original concentration within 12 hours.

CONCLUSION

Resveratrol with low aqueous solubility and water-soluble FUDR have the same absorption and metabolism pattern. The drug metabolism rate in worms was both dosage and time dependent. NGM dead method and liquid growing method achieved the best absorption efficiency in worms. The drug concentration within worms was comparable with that in mice, providing a bridge for dose translation from worms to mammals.

Predicting longevity in C. elegans: fertility, mobility and gene expression

Expression level of an hsp-16.2::gfp transgene is a predictor of longevity in Caenorhabditis elegans. Here we examine fertility, movement and longevity, comparing high-expressing ("bright") and low-expressing ("dim") animals. There was no differential fertility between bright and dim individuals, suggesting that dim worms were not excessively frail. Worms with high hsp-16.2::gfp expression had improved mobility, consistent with improved health span. We predicted that the increased longevity of the bright worms would be associated with increased expression of protective genes such as those shown to be upregulated in Age mutants. However, few genes were differentially transcribed, although internal controls (hsp-16.2 and family members) were differentially expressed. Quite surprising was the observation that expression level of the transgenic reporter was inherited by the progeny: in seven experiments bright worms consistently produced progeny that were brighter. We tested and ruled out possible artifacts such as differential copy-number of the transgene as an explanation of this differential brightness. These results suggest that a robust physiological state does not depend heavily upon transcriptional differences for its establishment, consistent with proteostatic mechanisms underlying the differential longevity.

Aspirin inhibits oxidant stress, reduces age-associated functional declines, and extends lifespan of Caenorhabditis elegans

AIMS

Oxidative stress and inflammation are leading risk factors for age-associated functional declines. We assessed aspirin effects on endogenous oxidative-stress levels, lifespan, and age-related functional declines, in the nematode Caenorhabditis elegans.

RESULTS

Both aspirin and its salicylate moiety, at nontoxic concentrations (0.5-1 mM), attenuated endogenous levels of reactive oxygen species (p<0.001), and upregulated antioxidant genes encoding superoxide dismutases (especially sod-3, p<0.001), catalases (especially ctl-2, p<0.0001), and two glutathione-S-transferases (gst-4 and gst-10; each p<0.005). Aspirin, and to a lesser degree salicylate, improved survival of hydrogen peroxide, and in the absence of exogenous stress aspirin extended lifespan by 21%-23% (each p<10(-9)), while salicylate added 14% (p<10(-6)). Aspirin and salicylate delayed age-dependent declines in motility and pharyngeal pumping (each p<0.005), and decreased intracellular protein aggregation (p<0.0001)-all established markers of physiological aging-consistent with slowing of the aging process. Aspirin fails to improve stress resistance or lifespan in nematodes lacking DAF-16, implying that it acts through this FOXO transcription factor.

INNOVATION

Studies in mice and humans suggest that aspirin may protect against multiple age-associated diseases by reducing all-cause mortality. We now demonstrate that aspirin markedly slows many measures of aging in the nematode.

CONCLUSIONS

Aspirin treatment is associated with diminished endogenous oxidant stress and enhanced resistance to exogenous peroxide, both likely mediated by activation of antioxidant defenses. Our evidence indicates that aspirin attenuates insulin-like signaling, thus protecting against oxidative stress, postponing age-associated functional declines and extending C. elegans lifespan under benign conditions.

MiR-34 modulates Caenorhabditis elegans lifespan via repressing the autophagy gene atg9

Evidence for a regulatory role of the miR-34 family in senescence is growing. However, the exact role of miR-34 in aging in vivo remains unclear. Here, we report that a mir-34 loss-of-function mutation in Caenorhabditis elegans markedly delays the age-related physiological decline, extends lifespan, and increases resistance to heat and oxidative stress. We also found that RNAi against autophagy-related genes, atg4, bec-1, or atg9, significantly reversed the lifespan-extending effect of the mir-34 mutants. Furthermore, miR-34a inhibits Atg9A expression at the post-transcriptional level in vitro, and the miR-34a binding sequences in the 3'-UTR of Atg9A contributes to the modulation of Atg9A expression by miR-34a. Our results demonstrate that the C. elegans mir-34 mutation extends lifespan by enhancing autophagic flux in C. elegans, and that miR-34 represses autophagy by directly inhibiting the expression of the autophagy-related proteins Atg9 in mammalian cells.

SESN-1 is a positive regulator of lifespan in Caenorhabditis elegans

Aging is a process of gradual functional decline leading to death. Reactive oxygen species (ROS) not only contribute to oxidative stress and cell damage that lead to aging but also serve as signaling molecules. Sestrins are evolutionarily conserved in all multicellular organisms and are required for regenerating hyperoxidized forms of peroxiredoxins and ROS clearance. However, whether sestrins regulate longevity in metazoans is still unclear. Here, we demonstrated that SESN-1, the only sestrin ortholog in Caenorhabditis elegans, is a positive regulator of lifespan. sesn-1 gene mutant worms had significantly shorter lifespans compared to wild-type animals, and overexpression of sesn-1 prolonged lifespan. Moreover, sesn-1 was found to play a key role in defense against several life stressors, including heat, hydrogen peroxide and the heavy metal copper; and sesn-1 mutants expressed higher levels of ROS and showed a decline in body muscle function. Surprisingly, loss of sesn-1 did not weaken the innate immune function of the worms. Together, these results suggest that SESN-1 is required for normal lifespan and its function in muscle cells prevents muscle degeneration over a lifetime.

Ageing and the small, non-coding RNA world

MicroRNAs, a class of small, non-coding RNAs, are now widely known for their importance in many aspects of biology. These small regulatory RNAs have critical functions in diverse biological events, including development and disease. Recent findings show that microRNAs are essential for lifespan determination in the model organisms, Caenorhabditis elegans and Drosophila, suggesting that microRNAs are also involved in the complex process of ageing. Further, short RNA fragments derived from longer parental RNAs, such as transfer RNA cleavage fragments, have now emerged as a novel class of regulatory RNAs that inhibit translation in response to stress. In addition, the RNA editing pathway is likely to act in the double-stranded RNA-mediated silencing machinery to suppress unfavorable RNA interference activity in the ageing process. These multiple, redundant layers in gene regulatory networks may make it possible to both stably and flexibly regulate genetic pathways in ensuring robustness of developmental and ageing processes.

Natural variation in Caenorhabditis briggsae mitochondrial form and function suggests a novel model of organelle dynamics

Mitochondrial functioning and morphology are known to be connected through cycles of organelle fusion and fission that depend upon the mitochondrial membrane potential (ΔΨM); however, we lack an understanding of the features and dynamics of natural mitochondrial populations. Using data from our recent study of univariate mitochondrial phenotypic variation in Caenorhabditis briggsae nematodes, we analyzed patterns of phenotypic correlation for 24 mitochondrial traits. Our findings support a role for ΔΨM in shaping mitochondrial dynamics, but no role for mitochondrial ROS. Further, our study suggests a novel model of mitochondrial population dynamics dependent upon cellular environmental context and with implications for mitochondrial genome integrity.

Pharmacological assays reveal age-related changes in synaptic transmission at the Caenorhabditis elegans neuromuscular junction that are modified by reduced insulin signalling

Frailty is a feature of neuromuscular ageing. Here we provide insight into the relative contribution of pre- and postsynaptic dysfunction to neuromuscular ageing using the nematode Caenorhabditis elegans. Assays of C. elegans motility highlight a precipitous decline during ageing. We describe a novel deployment of pharmacological assays of C. elegans neuromuscular function to resolve pre- and postsynaptic dysfunction that underpin this decreased motility during ageing. The cholinergic agonist levamisole and the cholinesterase inhibitor aldicarb elicited whole worm contraction and allowed a direct comparison of neuromuscular integrity, from 1 to 16 days old: measurements could be made from aged worms that were otherwise almost completely immobile. The rapidity and magnitude of the drug-induced contraction provides a measure of neuromuscular signalling whilst the difference between levamisole and aldicarb highlights presynaptic effects. Presynaptic neuromuscular transmission increased between 1 and 5 days old in wild-type but not in the insulin/IGF1 receptor mutant daf-2 (e1370). Intriguingly, there was no evidence of a role for insulin-dependent effects in older worms. Notably in 16-day-old worms, which were virtually devoid of spontaneous movement, the maximal contraction produced by both drugs was unchanged. Taken together the data support a maturation of presynaptic function and/or upstream elements during early ageing that is lost after genetic reduction of insulin signalling. Furthermore, this experimental approach has demonstrated a counterintuitive phenomenon: in aged worms neuromuscular strength is maintained despite the absence of motility.

Neurite sprouting and synapse deterioration in the aging Caenorhabditis elegans nervous system

Caenorhabditis elegans is a powerful model for analysis of the conserved mechanisms that modulate healthy aging. In the aging nematode nervous system, neuronal death and/or detectable loss of processes are not readily apparent, but because dendrite restructuring and loss of synaptic integrity are hypothesized to contribute to human brain decline and dysfunction, we combined fluorescence microscopy and electron microscopy (EM) to screen at high resolution for nervous system changes. We report two major components of morphological change in the aging C. elegans nervous system: (1) accumulation of novel outgrowths from specific neurons, and (2) physical decline in synaptic integrity. Novel outgrowth phenotypes, including branching from the main dendrite or new growth from somata, appear at a high frequency in some aging neurons, but not all. Mitochondria are often associated with age-associated branch sites. Lowered insulin signaling confers some maintenance of ALM and PLM neuron structural integrity into old age, and both DAF-16/FOXO and heat shock factor transcription factor HSF-1 exert neuroprotective functions. hsf-1 can act cell autonomously in this capacity. EM evaluation in synapse-rich regions reveals a striking decline in synaptic vesicle numbers and a diminution of presynaptic density size. Interestingly, old animals that maintain locomotory prowess exhibit less synaptic decline than same-age decrepit animals, suggesting that synaptic integrity correlates with locomotory healthspan. Our data reveal similarities between the aging C. elegans nervous system and mammalian brain, suggesting conserved neuronal responses to age. Dissection of neuronal aging mechanisms in C. elegans may thus influence the development of brain healthspan-extending therapies.

Tyrosol, a main phenol present in extra virgin olive oil, increases lifespan and stress resistance in Caenorhabditis elegans

Extra virgin olive oil (EVOO) consumption has been traditionally related to a higher longevity in the human population. EVOO effects on health are often attributed to its unique mixture of phenolic compounds with tyrosol and hydroxityrosol being the most biologically active. Although these compounds have been extensively studied in terms of their antioxidant potential and its role in different pathologies, their actual connection with longevity remains unexplored. This study utilized the nematode Caenorhabditis elegans to investigate the possible effects of tyrosol in metazoan longevity. Significant lifespan extension was observed at one specific tyrosol concentration, which also induced a higher resistance to thermal and oxidative stress and delayed the appearance of a biomarker of ageing. We also report that, although tyrosol was efficiently taken up by these nematodes, it did not induce changes in development, body length or reproduction. In addition, lifespan experiments with several mutant strains revealed that components of the heat shock response (HSF-1) and the insulin pathway (DAF-2 and DAF-16) might be implicated in mediating tyrosol effects in lifespan, while caloric restriction and sirtuins do not seem to mediate its effects. Together, our results point to hormesis as a possible mechanism to explain the effects of tyrosol on longevity in C. elegans.

Expression of a single-copy hsp-16.2 reporter predicts life span

The level of green fluorescent protein expression from an hsp-16.2-based transcriptional reporter predicts life span and thermotolerance in Caenorhabditis elegans. The initial report used a high-copy number reporter integrated into chromosome IV. There was concern that the life-span prediction power of this reporter was not attributable solely to hsp-16.2 output. Specifically, prediction power could stem from disruption of some critical piece of chromatin on chromosome IV by the gpIs1 insertion, a linked mutation from the process used to create the reporter, or from an artifact of transgene regulation (multicopy transgenes are subject to regulation by C elegans chromatin surveillance machinery). Here we determine if the ability to predict life span and thermotolerance is specific to the gpIs1 insertion or a general property of hsp-16.2-based reporters. New single-copy hsp-16.2-based reporters predict life span and thermotolerance. We conclude that prediction power of hsp-16.2-based transcriptional reporters is not an artifact of any specific transgene configuration or chromatin surveillance mechanism.

TOR signaling and rapamycin influence longevity by regulating SKN-1/Nrf and DAF-16/FoxO

The TOR kinase, which is present in the functionally distinct complexes TORC1 and TORC2, is essential for growth but associated with disease and aging. Elucidation of how TOR influences life span will identify mechanisms of fundamental importance in aging and TOR functions. Here we show that when TORC1 is inhibited genetically in C. elegans, SKN-1/Nrf, and DAF-16/FoxO activate protective genes, and increase stress resistance and longevity. SKN-1 also upregulates TORC1 pathway gene expression in a feedback loop. Rapamycin triggers a similar protective response in C. elegans and mice, but increases worm life span dependent upon SKN-1 and not DAF-16, apparently by interfering with TORC2 along with TORC1. TORC1, TORC2, and insulin/IGF-1-like signaling regulate SKN-1 activity through different mechanisms. We conclude that modulation of SKN-1/Nrf and DAF-16/FoxO may be generally important in the effects of TOR signaling in vivo and that these transcription factors mediate an opposing relationship between growth signals and longevity.

Genetics, life span, health span, and the aging process in Caenorhabditis elegans

As a tool for measuring the aging process, life span has been invaluable in dissecting the genes that modulate longevity. Studies over the past few decades have identified several hundred genes that can modify life span in model organisms such as yeast, worms, and flies. Yet, despite this vast amount of research, we still do not fully understand how the genes that affect life span influence how an organism ages. How does modulation of the genes that affect life span contribute to the aging process? Does life-span extension result in extension of healthy aging? Here, we will focus primarily on the insulin/IGF-1 signaling pathway in Caenorhabditis elegans because members of this pathway have been shown to be associated with extended life span across phylogeny, from worms to humans. I discuss how this connects to the aging process, age-associated disease, and the potential to increase healthy aging in addition to lengthening life span.

The C. elegans microRNA mir-71 acts in neurons to promote germline-mediated longevity through regulation of DAF-16/FOXO

The life span of Caenorhabditis elegans is controlled by signaling between the germline and the soma. Germ cell removal extends life span by triggering the activation of the DAF-16/FOXO transcription factor in the intestine. Here we analyze microRNA function in C. elegans aging and show that the microRNA mir-71 functions to mediate the effects of germ cell loss on life span. mir-71 is required for the life span extension caused by germline removal, and overexpression of mir-71 further extends the life span of animals lacking germ cells. mir-71 functions in the nervous system to facilitate the localization and transcriptional activity of DAF-16 in the intestine. Our findings reveal a microRNA-dependent mechanism of life span regulation by the germline and indicate that signaling among the gonad, the nervous system, and the intestine coordinates the life span of the entire organism.

Control of intestinal bacterial proliferation in regulation of lifespan in Caenorhabditis elegans

Background

A powerful approach to understanding complex processes such as aging is to use model organisms amenable to genetic manipulation, and to seek relevant phenotypes to measure. Caenorhabditis elegans is particularly suited to studies of aging, since numerous single-gene mutations have been identified that affect its lifespan; it possesses an innate immune system employing evolutionarily conserved signaling pathways affecting longevity. As worms age, bacteria accumulate in the intestinal tract. However, quantitative relationships between worm genotype, lifespan, and intestinal lumen bacterial load have not been examined. We hypothesized that gut immunity is less efficient in older animals, leading to enhanced bacterial accumulation, reducing longevity. To address this question, we evaluated the ability of worms to control bacterial accumulation as a functional marker of intestinal immunity.

Results

We show that as adult worms age, several C. elegans genotypes show diminished capacity to control intestinal bacterial accumulation. We provide evidence that intestinal bacterial load, regulated by gut immunity, is an important causative factor of lifespan determination; the effects are specified by bacterial strain, worm genotype, and biologic age, all acting in concert.

Conclusions

In total, these studies focus attention on the worm intestine as a locus that influences longevity in the presence of an accumulating bacterial population. Further studies defining the interplay between bacterial species and host immunity in C. elegans may provide insights into the general mechanisms of aging and age-related diseases.

Behavioral decay in aging male C. elegans correlates with increased cell excitability

Deteriorative changes in behavioral functions are natural processes that accompany aging. In advanced aged C. elegans nematodes, gross decline in general behaviors, such as locomotion and feeding, is correlated with degeneration of muscle structure and contractile function. In this study, we characterized the age-related changes in C. elegans male mating behavior to determine possible causes that ultimately lead to age-related muscle frailty. Unlike the kinetics of general behavioral decline, we found that mating behavior deteriorates early in adulthood, with no obvious muscle fiber disorganization or sperm dysfunction. Through direct mating behavior observations, Ca(2+) imaging, and pharmacological tests, we found that the muscular components used for mating become more excitable as the males age. Interestingly, manipulating either the expression of acetylcholine receptor (AChR) genes or dietary-mediated ether-a-go-go family K(+) channel function can reduce the muscle excitability of older males and concurrently improve mating behavior, suggesting a correlation between these biological processes.

Dosage-dependent induction of behavioral decline in Caenorhabditis elegans by long-term treatment of static magnetic fields

The aim of this work was to explore the molecular mechanisms associated with possible health hazards induced by static magnetic fields (SMFs). Nematodes were grown under SMFs at field strengths from 0 to 200 mT, and the speed of body movement was measured. The effects of exposure to static magnetic fields were observed to be significant in the higher field strength and longer treatment. To explore the possible molecular mechanisms responsible for these effects, semi-quantitative real-time RT-PCR was performed using primers specific to 120 randomly selected genes. Twenty-six differentially expressed genes among apoptosis-, oxidative stress-, and cancer-related genes were identified, indicating that a global molecular response to SMF treatment occurred. The induction of apoptosis was verified by the increase of fluorescence in a terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay, by the caspase-3 activity assay, and by immunostaining using an antibody against the ced-3 gene product. Mutations in genes involved in major apoptotic pathways, that is, ced-3, ced-4, and ced-9, abolished this SMF-induced behavioral decline; this is consistent with the hypothesis that the apoptosis pathways are involved in the SMF-induced mobility decline. Here we show that long-term and low-dosage exposure to SMF is capable of inducing an apoptosis-mediated behavioral decline in nematodes.

Analysis of aging in Caenorhabditis elegans

This chapter is dedicated to the study of aging in Caenorhabditis elegans (C. elegans). The assays are divided into two sections. In the first section, we describe detailed protocols for performing life span analysis in solid and liquid medium. In the second section, we describe various assays for measuring age-related changes. Our laboratory has been involved in several fruitful collaborations with non-C. elegans researchers keen on testing a role for their favorite gene in modulating aging (Carrano et al., 2009; Dong et al., 2007; Raices et al., 2008; Wolff et al., 2006). But even with the guidance of trained worm biologists, this undertaking can be daunting. We hope that this chapter will serve as a worthy compendium for those researchers who may or may not have immediate access to laboratories studying C. elegans.

Reserpine modulates neurotransmitter release to extend lifespan and alleviate age-dependent Aβ proteotoxicity in Caenorhabditis elegans

Aging is a debilitating process often associated with chronic diseases such as diabetes, cardiovascular and neurodegenerative diseases like Alzheimer's disease (AD). AD occurs at a very high incidence posing a huge burden to the society. Model organisms such as C. elegans become essential to understand aging or lifespan extension - the etiology, molecular mechanism and identification of new drugs against age associated diseases. The AD model, manifesting Aβ proteotoxicity, in C. elegans is well established and has provided valuable insights. Earlier, we have reported that Reserpine, an FDA-approved antihypertensive drug, increases C. elegans lifespan with a high quality of life and ameliorates Aβ toxicity in C. elegans. But reserpine does not seem to act through the known lifespan extension pathways or inhibition of its known target, vesicular monoamine transporter, VMAT. Reserpine's mode of action and the pathways it activates are not known. Here, we have evaluated the presynaptic neurotransmitter(s) release pathway and identified acetylcholine (ACh) as the crucial player for reserpine's action. The corroborating evidences are: i) lack of lifespan extension in the ACh loss of function (hypomorphic) - synthesis (cha-1) and transport (unc-17) mutants; ii) mitigation of chronic aldicarb effect; iii) lifespan extension in dopamine (cat-2) and dopamine and serotonin (bas-1) biosynthetic mutants; iv) no rescue from exogenous serotonin induced paralysis in the AD model worms; upon reserpine treatment. Thus, modulation of acetylcholine is essential for reserpine's action.

MicroRNA predictors of longevity in Caenorhabditis elegans

Neither genetic nor environmental factors fully account for variability in individual longevity: genetically identical invertebrates in homogenous environments often experience no less variability in lifespan than outbred human populations. Such variability is often assumed to result from stochasticity in damage accumulation over time; however, the identification of early-life gene expression states that predict future longevity would suggest that lifespan is least in part epigenetically determined. Such "biomarkers of aging," genetic or otherwise, nevertheless remain rare. In this work, we sought early-life differences in organismal robustness in unperturbed individuals and examined the utility of microRNAs, known regulators of lifespan, development, and robustness, as aging biomarkers. We quantitatively examined Caenorhabditis elegans reared individually in a novel apparatus and observed throughout their lives. Early-to-mid-adulthood measures of homeostatic ability jointly predict 62% of longevity variability. Though correlated, markers of growth/muscle maintenance and of metabolic by-products ("age pigments") report independently on lifespan, suggesting that graceful aging is not a single process. We further identified three microRNAs in which early-adulthood expression patterns individually predict up to 47% of lifespan differences. Though expression of each increases throughout this time, mir-71 and mir-246 correlate with lifespan, while mir-239 anti-correlates. Two of these three microRNA "biomarkers of aging" act upstream in insulin/IGF-1-like signaling (IIS) and other known longevity pathways, thus we infer that these microRNAs not only report on but also likely determine longevity. Thus, fluctuations in early-life IIS, due to variation in these microRNAs and from other causes, may determine individual lifespan.

Hormetins, antioxidants and prooxidants: defining quercetin-, caffeic acid- and rosmarinic acid-mediated life extension in C. elegans

Quercetin, Caffeic- and Rosmarinic acid exposure extend lifespan in Caenorhabditis elegans. This comparative study uncovers basic common and contrasting underlying mechanisms: For all three compounds, life extension was characterized by hormetic dose response curves, but hsp-level expression was variable. Quercetin and Rosmarinic acid both suppressed bacterial growth; however, antibacterial properties were not the dominant reason for life extension. Exposure to Quercetin, Caffeic- and Rosmarinic acid resulted in reduced body size, altered lipid-metabolism and a tendency towards a delay in reproductive timing; however the total number of offspring was not affected. An indirect dietary restriction effect, provoked by either chemo-repulsion or diminished pharyngeal pumping was rejected. Quercetin and Caffeic acid were shown to increase the antioxidative capacity in vivo and, by means of a lipofuscin assay, reduce the oxidative damage in the nematodes. Finally, it was possible to demonstrate that the life and thermotolerance enhancing properties of Caffeic- and Rosmarinic acid both rely on osr-1, sek-1, sir-2.1 and unc-43 plus daf-16 in the case of Caffeic acid. Taken together, hormesis, in vivo antioxidative/prooxidative properties, modulation of genetic players, as well as the re-allocation of energy all contribute (to some extent and dependent on the polyphenol) to life extension.

Caenorhabditis elegans as a platform for molecular quantitative genetics and the systems biology of natural variation

Over the past 30 years, the characteristics that have made the nematode Caenorhabditis elegans one of the premier animal model systems have also allowed it to emerge as a powerful model system for determining the genetic basis of quantitative traits, particularly for the identification of naturally segregating and/or lab-adapted alleles with large phenotypic effects. To better understand the genetic underpinnings of natural variation in other complex phenotypes, C. elegans is uniquely poised in the emerging field of quantitative systems biology because of the extensive knowledge of cellular and neural bases to such traits. However, perturbations in standing genetic variation and patterns of linkage disequilibrium among loci are likely to limit our ability to tie understanding of molecular function to a broader evolutionary context. Coupling the experimental strengths of the C. elegans system with the ecological advantages of closely related nematodes should provide a powerful means of understanding both the molecular and evolutionary genetics of quantitative traits.

MicroRNAs in C. elegans Aging: Molecular Insurance for Robustness?

The last decade has witnessed a revolution in our appreciation of the extensive regulatory gene expression networks modulated by small untranslated RNAs. microRNAs (miRNAs), ~22 nt RNAs that bind imperfectly to partially homologous sites on target mRNAs to regulate transcript expression, are now known to influence a broad range of biological processes germane to development, homeostatic regulation and disease. It has been proposed that miRNAs ensure biological robustness, and aging has been described as a progressive loss of system and cellular robustness, but relatively little work to date has addressed roles of miRNAs in longevity and healthspan (the period of youthful vigor and disease resistance that precedes debilitating decline in basic functions). The C. elegans model is highly suitable for testing hypotheses regarding miRNA impact on aging biology: the lifespan of the animal is approximately three weeks, there exist a wealth of genetic mutations that alter lifespan through characterized pathways, biomarkers that report strong healthspan have been defined, and many miRNA genes have been identified, expression-profiled, and knocked out. 50/114 C. elegans miRNAs change in abundance during adult life, suggesting significant potential to modulate healthspan and lifespan. Indeed, miRNA lin-4 has been elegantly shown to influence lifespan and healthspan via its lin-14 mRNA target and the insulin signaling pathway. 27 of the C. elegans age-regulated miRNAs have sequence similarity with both fly and human miRNAs. We review current understanding of a field poised to reveal major insights into potentially conserved miRNA-regulated networks that modulate aging.