Weissella confusa CGMCC 19,308 Strain Protects Against Oxidative Stress,Increases Lifespan,and Bacterial Disease Resistance in Caenorhabditis elegans

The aim of this study was to investigate the antioxidant activity of Weissella confusa CGMCC 19,308 and its influence on longevity and host defense against Salmonella Typhimurium of Caenorhabditis elegans. The CFCS (cell-free culture supernatant) of W. confusa CGMCC 19,308 possessed DPPH radicals, hydroxyl radicals, and superoxide anion scavenging activity. The lifespan of the C. elegans fed W. confusa CGMCC 19,308 was significantly (p?<?0.001) longer than that of worms fed Escherichia coli OP50. Moreover, worms fed W. confusa CGMCC 19,308 were more resistant to oxidative stress induced by hydrogen peroxide and S. Typhimurium infection. RNA-seq analysis showed that the most significantly differentially expressed genes (DEGs) in C. elegans fed with W. confusa CGMCC 19,308 were mainly col genes (col-43, col-2, col-40, col-155, col-37), glutathione–S-transferase (GST)-related genes (gst-44, gst-9, gst-17, gst-18, gstk-2), cnc-9 (immune-related gene), and sod-5 (superoxide dismutase). These results indicated that cuticle collagen synthesis, immunity, and antioxidant defense (AOD) system of C. elegans were affected after being fed with W. confusa CGMCC 19,308 instead of E. coli OP50. Our study suggested W. confusa CGMCC 19,308 had the antioxidant activity and could prolong lifespan and enhance the host defense against S. Typhimurium of C. elegans. This study provided new evidences for the W. confusa CGMCC 19,308 as a potential probiotic candidate for anti-aging and anti-bacterial infection.

     

Influence of Lactic Acid Bacteria on Longevity of Caenorhabditis elegans and Host Defense against Salmonella enterica Serovar Enteritidis

This study aimed to develop a convenient model to investigate the senescence of host defenses and the influence of food and nutrition. A small soil nematode, Caenorhabditis elegans, was grown for 3 days from hatching on a lawn of Escherichia coli OP50 as the normal food source, and subsequently some of the nematodes were fed lactic acid bacteria (LAB). The life spans of worms fed LAB were significantly longer than the life spans of those fed OP50. To investigate the effect of age on host defenses, 3- to 7-day-old worms fed OP50 were transferred onto a lawn of Salmonella enterica serovar Enteritidis for infection. The nematodes died over the course of several days, and the accumulation of salmonella in the intestinal lumen suggested that the worms were infected. The 7-day-old worms showed a higher death rate during the 5 days after infection than nematodes infected at the age of 3 days; no clear difference was observed when the worms were exposed to OP50. We then investigated whether the LAB could exert probiotic effects on the worms' host defenses and improve life span. Seven-day-old nematodes fed LAB from the age of 3 days were more resistant to salmonella than worms fed OP50 until they were infected with salmonella. This study clearly showed that LAB can enhance the host defense of C. elegans and prolong life span. The nematode appears to be an appropriate model for screening useful probiotic strains or dietetic antiaging substances.     

Neuronal control of lipid metabolism by STR‐2 G protein‐coupled receptor promotes longevity in Caenorhabditis elegans

The G protein‐coupled receptor (GPCR) encoding family of genes constitutes more than 6% of genes in Caenorhabditis elegans genome. GPCRs control behavior, innate immunity, chemotaxis, and food search behavior. Here, we show that C. elegans longevity is regulated by a chemosensory GPCR STR‐2, expressed in AWC and ASI amphid sensory neurons. STR‐2 function is required at temperatures of 20°C and higher on standard Escherichia coli OP50 diet. Under these conditions, this neuronal receptor also controls health span parameters and lipid droplet (LD) homeostasis in the intestine. We show that STR‐2 regulates expression of delta‐9 desaturases, fat‐5, fat‐6 and fat‐7, and of diacylglycerol acyltransferase dgat‐2. Rescue of the STR‐2 function in either AWC and ASI, or ASI sensory neurons alone, restores expression of fat‐5, dgat‐2 and restores LD stores and longevity. Rescue of stored fat levels of GPCR mutant animals to wild‐type levels, with low concentration of glucose, rescues its lifespan phenotype. In all, we show that neuronal STR‐2 GPCR facilitates control of neutral lipid levels and longevity in C. elegans.     

MPK‐1/ERK is required for the full activity of resveratrol in extended lifespan and reproduction

Resveratrol (RSV) extends the lifespan of various organisms through activation of sirtuin. However, whether RSV‐mediated longevity is entirely dependent upon sirtuin is still controversial. Thus, understanding additional mechanisms concerning the genetic requirements for the biological activity of RSV needs to be clarified to utilize the beneficial effects of RSV. In this study using Caenorhabditis elegans as a model system, we found that MPK‐1 (an ERK homolog) signaling is necessarily required for RSV‐mediated longevity of sir‐2.1/sirtuin mutants as well as for wild‐type worms. We demonstrated that MPK‐1 contributes to RSV‐mediated longevity through nuclear accumulation of SKN‐1 in a SIR‐2.1/DAF‐16 pathway‐independent manner. The positive effect of RSV in regulating lifespan was completely abolished by RNA interference against mpk‐1 in the sir‐2.1 and daf‐16 mutants, strongly indicating that the MPK‐1/SKN‐1 pathway is involved in RSV‐mediated longevity, independently of SIR‐2.1/DAF‐16. We additionally found that RSV protected worms from oxidative stress via MPK‐1. In addition to organismal aging, RSV prevented the age‐associated loss of mitotic germ cells, brood size, and reproductive span through MPK‐1 in C. elegans germline. Therefore, our findings not only provide new mechanistic insight into the controversial effects of RSV on organismal longevity, but additionally have important implications in utilizing RSV to improve the outcome of aging‐related diseases.     

KIN‐4/MAST kinase promotes PTEN‐mediated longevity of Caenorhabditis elegans via binding through a PDZ domain

PDZ domain‐containing proteins (PDZ proteins) act as scaffolds for protein–protein interactions and are crucial for a variety of signal transduction processes. However, the role of PDZ proteins in organismal lifespan and aging remains poorly understood. Here, we demonstrate that KIN‐4, a PDZ domain‐containing microtubule‐associated serine‐threonine (MAST) protein kinase, is a key longevity factor acting through binding PTEN phosphatase in Caenorhabditis elegans. Through a targeted genetic screen for PDZ proteins, we find that kin‐4 is required for the long lifespan of daf‐2/insulin/IGF‐1 receptor mutants. We then show that neurons are crucial tissues for the longevity‐promoting role of kin‐4. We find that the PDZ domain of KIN‐4 binds PTEN, a key factor for the longevity of daf‐2 mutants. Moreover, the interaction between KIN‐4 and PTEN is essential for the extended lifespan of daf‐2 mutants. As many aspects of lifespan regulation in C. elegans are evolutionarily conserved, MAST family kinases may regulate aging and/or age‐related diseases in mammals through their interaction with PTEN.     

Germline stem cell arrest inhibits the collapse of somatic proteostasis early in Caenorhabditis elegans adulthood

All cells rely on highly conserved protein folding and clearance pathways to detect and resolve protein damage and to maintain protein homeostasis (proteostasis). Because age is associated with an imbalance in proteostasis, there is a need to understand how protein folding is regulated in a multicellular organism that undergoes aging. We have observed that the ability of Caenorhabditis elegans to maintain proteostasis declines sharply following the onset of oocyte biomass production, suggesting that a restricted protein folding capacity may be linked to the onset of reproduction. To test this hypothesis, we monitored the effects of different sterile mutations on the maintenance of proteostasis in the soma of C. elegans. We found that germline stem cell (GSC) arrest rescued protein quality control, resulting in maintenance of robust proteostasis in different somatic tissues of adult animals. We further demonstrated that GSC‐dependent modulation of proteostasis requires several different signaling pathways, including hsf‐1 and daf‐16/kri‐1/tcer‐1, daf‐12, daf‐9, daf‐36, nhr‐80, and pha‐4 that differentially modulate somatic quality control functions, such that each signaling pathway affects different aspects of proteostasis and cannot functionally complement the other pathways. We propose that the effect of GSCs on the collapse of proteostasis at the transition to adulthood is due to a switch mechanism that links GSC status with maintenance of somatic proteostasis via regulation of the expression and function of different quality control machineries and cellular stress responses that progressively lead to a decline in the maintenance of proteostasis in adulthood, thereby linking reproduction to the maintenance of the soma.     

Pyruvate imbalance mediates metabolic reprogramming and mimics lifespan extension by dietary restriction in Caenorhabditis elegans

Dietary restriction (DR) is the most universal intervention known to extend animal lifespan. DR also prevents tumor development in mammals, and this effect requires the tumor suppressor PTEN. However, the metabolic and cellular processes that underly the beneficial effects of DR are poorly understood. We identified slcf‐1 in an RNAi screen for genes that extend Caenorhabditis elegans lifespan in a PTEN/daf‐18‐dependent manner. We showed that slcf‐1 mutation, which increases average lifespan by 40%, mimics DR in worms fed ad libitum. An NMR‐based metabolomic characterization of slcf‐1 mutants revealed lower lipid levels compared to wild‐type animals, as expected for dietary‐restricted animals, but also higher pyruvate content. Epistasis experiments and metabolic measurements support a model in which the long lifespan of slcf‐1 mutants relies on increased mitochondrial pyruvate metabolism coupled to an adaptive response to oxidative stress. This response requires DAF‐18/PTEN and the previously identified DR effectors PHA‐4/FOXA, HSF‐1/HSF1, SIR‐2.1/SIRT‐1, and AMPK/AAK‐2. Overall, our data show that pyruvate homeostasis plays a central role in lifespan control in C. elegans and that the beneficial effects of DR results from a hormetic mechanism involving the mitochondria. Analysis of the SLCF‐1 protein sequence predicts that slcf‐1 encodes a plasma membrane transporter belonging to the conserved monocarboxylate transporter family. These findings suggest that inhibition of this transporter homolog in mammals might also promote a DR response.     

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.     

DILP‐producing median neurosecretory cells in the Drosophila brain mediate the response of lifespan to nutrition

Dietary restriction extends lifespan in diverse organisms, but the gene regulatory mechanisms and tissues mediating the increased survival are still unclear. Studies in worms and flies have revealed a number of candidate mechanisms, including the target of rapamycin and insulin/IGF‐like signalling (IIS) pathways and suggested a specific role for the nervous system in mediating the response. A pair of sensory neurons in Caenorhabditis elegans has been found to specifically mediate DR lifespan extension, but a neuronal focus in the Drosophila nervous system has not yet been identified. We have previously shown that reducing IIS via the partial ablation of median neurosecretory cells in the Drosophila adult brain, which produce three of the seven fly insulin‐like peptides, extends lifespan. Here, we show that these cells are required to mediate the response of lifespan to full feeding in a yeast dilution DR regime and that they appear to do so by mechanisms that involve both altered IIS and other endocrine effects. We also present evidence of an interaction between these mNSCs, nutrition and sleep, further emphasising the functional homology between the DILP‐producing neurosecretory cells in the Drosophila brain and the hypothalamus of mammals in their roles as integration sites of many inputs for the control of lifespan and behaviour.     

Insulin‐like signalling in neurons controls lifespan in C. elegans

Insulin‐like signalling controls C. elegans lifespan, development and metabolism. Mutations that weaken this insulin‐like signalling pathway extend lifespan. Severe mutations abolishing insulin‐like signalling cause animals to arrest development as dauer larvae, a larval form specialized for stress resistance and long‐term survival. A number of the genes acting in this pathway have been cloned, including daf‐2, which encodes a homolog of vertebrate insulin/IGF‐I receptors, and age‐1, encoding the C. elegans homolog of the PI(3)K p110 catalytic subunit. In order to identify cells from which insulin‐like signalling controls lifespan and development, transgenic animals were constructed which possessed insulin‐like signalling only in specific cell types. To achieve this, cell‐type specific promoters were used to drive expression of daf‐2 or age‐1 cDNAs in daf‐2(–/–) or age‐1(–/–) backgrounds, respectively. By utilizing this strategy, we could restore wild‐type daf‐2 or age‐1 activity only in cells that are capable of expressing each transgene. Restoring insulin‐like signalling to the nervous system of daf‐2 or age‐1 mutants could rescue long lifespan. This result was specific for transgenes restoring insulin‐like signalling to the nervous system. Expressing daf‐2 or age‐1 cDNAs from muscle‐ or intestinally‐restricted promoters was insufficient to rescue lifespan. In contrast, age‐1 and daf‐2 expression in either neuronal or non‐neuronal cell types rescued dauer larval arrest in the mutants. These findings demonstrate that insulin‐like signalling pathways in the nervous system control C. elegans lifespan.     

Mitochondrial metabolites extend lifespan

Disruption of mitochondrial respiration in the nematode Caenorhabditis elegans can extend lifespan. We previously showed that long‐lived respiratory mutants generate elevated amounts of α‐ketoacids. These compounds are structurally related to α‐ketoglutarate, suggesting they may be biologically relevant. Here, we show that provision of several such metabolites to wild‐type worms is sufficient to extend their life. At least one mode of action is through stabilization of hypoxia‐inducible factor‐1 (HIF‐1). We also find that an α‐ketoglutarate mimetic, 2,4‐pyridinedicarboxylic acid (2,4‐PDA), is alone sufficient to increase the lifespan of wild‐type worms and this effect is blocked by removal of HIF‐1. HIF‐1 is constitutively active in isp‐1(qm150) Mit mutants, and accordingly, 2,4‐PDA does not further increase their lifespan. Incubation of mouse 3T3‐L1 fibroblasts with life‐prolonging α‐ketoacids also results in HIF‐1α stabilization. We propose that metabolites that build up following mitochondrial respiratory dysfunction form a novel mode of cell signaling that acts to regulate lifespan.