A sensitive mass spectrometry platform identifies metabolic changes of life history traits in C. elegans

Surface Lipids in Nematodes are Influenced by Development and Species-specific Adaptations

The surface of an organism is a dynamic interface that continually adapts to its environment. In nematodes, the cuticle forms a complex boundary that protects against the physicochemical pressures. However, the precise molecular composition and function of this surface remain largely unexplored. By utilizing 3D-OrbiSIMS, an advanced surface-sensitive mass spectrometry method, we directly characterized the molecular composition of the outermost regions (∼50 nm) of Caenorhabditis elegans and Pristionchus pacificus to improve the understanding of species-specific surface lipid composition and its potential roles in nematode biology. We found that nematode surfaces consist of a lipid-dominated landscape (>81% C. elegans and >69% P. pacificus of all surveyed chemistries) with distinct compositions, which enrich in granularity and complexity through development. The surface lipids are also species-specific, potentially highlighting distinct molecular compositions that are derived from diverging evolutionary paths. By exploring the effect of mutations on lipid production, we found the peroxisomal fatty acid β-oxidation component daf-22 is essential for defining the surface molecular fingerprint. This pathway is conserved across species in producing distinct chemical profiles, indicating its fundamental role in lipid metabolism and maintaining the surface integrity and function. Furthermore, we discovered that variations in surface lipids of C. elegans daf-22 larvae contribute to significantly increased susceptibility to predation by P. pacificus. Therefore, our findings reveal that nematode surface lipids are developmentally dependent, species-specific, and fundamental in interspecies interactions. These insights pave the way for further exploration into the physiological and behavioral significance of surface lipids.

Lipid remodeling in context of cellular senescence

Cellular senescence is a response that irreversibly arrests stressed cells thus providing a potent tumor suppressor mechanism. In parallel, senescent cells exhibit an immunogenic secretome called SASP (senescence-associated secretory phenotype) that impairs tissue homeostasis and is involved in numerous age-related diseases. Senescence establishment is achieved through the unfolding of a profound transcriptional reprogramming together with morphological changes. These alterations are accompanied by important metabolic adaptations characterized by biosynthetic pathways reshuffling and lipid remodeling. In this mini-review we highlight the intricate links between lipid metabolism and the senescence program and we discuss the potential interventions on lipid pathways that can alleviate the senescence burden.

High-content phenotypic analysis of a C. elegans recombinant inbred population identifies genetic and molecular regulators of lifespan

Lifespan is influenced by complex interactions between genetic and environmental factors. Studying those factors in model organisms of a single genetic background limits their translational value for humans. Here, we mapped lifespan determinants in 85 C. elegans recombinant inbred advanced intercross lines (RIAILs). We assessed molecular profiles-transcriptome, proteome, and lipidome-and life-history traits, including lifespan, development, growth dynamics, and reproduction. RIAILs exhibited large variations in lifespan, which correlated positively with developmental time. We validated three longevity modulators, including rict-1, gfm-1, and mltn-1, among the top candidates obtained from multiomics data integration and quantitative trait locus (QTL) mapping. We translated their relevance to humans using UK Biobank data and showed that variants in GFM1 are associated with an elevated risk of age-related heart failure. We organized our dataset as a resource that allows interactive explorations for new longevity targets.

A conserved complex lipid signature marks human muscle aging and responds to short-term exercise

Studies in preclinical models suggest that complex lipids, such as phospholipids, play a role in the regulation of longevity. However, identification of universally conserved complex lipid changes that occur during aging, and how these respond to interventions, is lacking. Here, to comprehensively map how complex lipids change during aging, we profiled ten tissues in young versus aged mice using a lipidomics platform. Strikingly, from >1,200 unique lipids, we found a tissue-wide accumulation of bis(monoacylglycero)phosphate (BMP) during mouse aging. To investigate translational value, we assessed muscle tissue of young and older people, and found a similar marked BMP accumulation in the human aging lipidome. Furthermore, we found that a healthy-aging intervention consisting of moderate-to-vigorous exercise was able to lower BMP levels in postmenopausal female research participants. Our work implicates complex lipid biology as central to aging, identifying a conserved aging lipid signature of BMP accumulation that is modifiable upon a short-term healthy-aging intervention.

High-content phenotypic analysis of a C. elegans recombinant inbred population identifies genetic and molecular regulators of lifespan

Lifespan is influenced by complex interactions between genetic and environmental factors. Studying those factors in model organisms of a single genetic background limits their translational value for humans. Here, we mapped lifespan determinants in 85 genetically diverse C. elegans recombinant intercross advanced inbred lines (RIAILs). We assessed molecular profiles - transcriptome, proteome, and lipidome - and life-history traits, including lifespan, development, growth dynamics, and reproduction. RIAILs exhibited large variations in lifespan, which positively correlated with developmental time. Among the top candidates obtained from multi-omics data integration and QTL mapping, we validated known and novel longevity modulators, including rict-1, gfm-1 and mltn-1. We translated their relevance to humans using UK Biobank data and showed that variants in RICTOR and GFM1 are associated with an elevated risk of age-related heart disease, dementia, diabetes, kidney, and liver diseases. We organized our dataset as a resource (https://lisp-lms.shinyapps.io/RIAILs/) that allows interactive explorations for new longevity targets.

Bacterial diet affects the age-dependent decline of associative learning in Caenorhabditis elegans

The causality and mechanism of dietary effects on brain aging are still unclear due to the long time scales of aging. The nematode Caenorhabditis elegans has contributed to aging research because of its short lifespan and easy genetic manipulation. When fed the standard laboratory diet, Escherichia coli, C. elegans experiences an age-dependent decline in temperature-food associative learning, called thermotaxis. To address if diet affects this decline, we screened 35 lactic acid bacteria as alternative diet and found that animals maintained high thermotaxis ability when fed a clade of Lactobacilli enriched with heterofermentative bacteria. Among them, Lactobacillus reuteri maintained the thermotaxis of aged animals without affecting their lifespan and motility. The effect of Lb. reuteri depends on the DAF-16 transcription factor functioning in neurons. Furthermore, RNA sequencing analysis revealed that differentially expressed genes between aged animals fed different bacteria were enriched with DAF-16 targets. Our results demonstrate that diet can impact brain aging in a daf-16-dependent manner without changing the lifespan.

The regulation of Insulin/IGF-1 signaling by miR-142-3p associated with human longevity

MicroRNAs (miRNAs) have been demonstrated to modulate life span in the invertebrates C. elegans and Drosophila by targeting conserved pathways of aging, such as insulin/IGF-1 signaling (IIS). However, a role for miRNAs in modulating human longevity has not been fully explored. Here we investigated novel roles of miRNAs as a major epigenetic component of exceptional longevity in humans. By profiling the miRNAs in B-cells from Ashkenazi Jewish centenarians and 70-year-old controls without a longevity history, we found that the majority of differentially expressed miRNAs were upregulated in centenarians and predicted to modulate the IIS pathway. Notably, decreased IIS activity was found in B cells from centenarians who harbored these upregulated miRNAs. miR-142-3p, the top upregulated miRNA, was verified to dampen the IIS pathway by targeting multiple genes including GNB2, AKT1S1, RHEB and FURIN . Overexpression of miR-142-3p improved the stress resistance under genotoxicity and induced the impairment of cell cycle progression in IMR90 cells. Furthermore, mice injected with a miR-142-3p mimic showed reduced IIS signaling and improved longevity-associated phenotypes including enhanced stress resistance, improved diet/aging-induced glucose intolerance, and longevity-associated change of metabolic profile. These data suggest that miR-142-3p is involved in human longevity through regulating IIS-mediated pro-longevity effects. This study provides strong support for the use of miR-142-3p as a novel therapeutic to promote longevity or prevent aging/aging-related diseases in human.

Glycine and aging: Evidence and mechanisms

The restriction of calories, branched-chain amino acids, and methionine have all been shown to extend lifespan in model organisms. Recently, glycine was shown to significantly boost longevity in genetically heterogenous mice. This simple amino acid similarly extends lifespan in rats and improves health in mammalian models of age-related disease. While compelling data indicate that glycine is a pro-longevity molecule, divergent mechanisms may underlie its effects on aging. Glycine is abundant in collagen, a building block for glutathione, a precursor to creatine, and an acceptor for the enzyme Glycine N-methyltransferase (GNMT). A review of the literature strongly implicates GNMT, which clears methionine from the body by taking a methyl group from S-adenosyl-L-methionine and methylating glycine to form sarcosine. In flies, Gnmt is required for reduced insulin/insulin-like growth factor 1 signaling and caloric restriction to fully extend lifespan. The geroprotector spermidine requires Gnmt to upregulate autophagy genes and boost longevity. Moreover, the overexpression of Gnmt is sufficient to extend lifespan and reduce methionine levels. Sarcosine, or methylglycine, declines with age in multiple species and is capable of inducing autophagy both in vitro and in vivo. Taken all together, existing evidence suggests that glycine prolongs life by mimicking methionine restriction and activating autophagy.

L-threonine promotes healthspan by expediting ferritin-dependent ferroptosis inhibition in C. elegans

The pathways that impact longevity in the wake of dietary restriction (DR) remain still ill-defined. Most studies have focused on nutrient limitation and perturbations of energy metabolism. We showed that the L-threonine was elevated in Caenorhabditis elegans under DR, and that L-threonine supplementation increased its healthspan. Using metabolic and transcriptomic profiling in worms that were fed with RNAi to induce loss of key candidate mediators. L-threonine supplementation and loss-of-threonine dehydrogenaseincreased the healthspan by attenuating ferroptosis in a ferritin-dependent manner. Transcriptomic analysis showed that FTN-1 encoding ferritin was elevated, implying FTN-1 is an essential mediator of longevity promotion. Organismal ferritin levels were positively correlated with chronological aging and L-threonine supplementation protected against age-associated ferroptosis through the DAF-16 and HSF-1 pathways. Our investigation uncovered the role of a distinct and universal metabolite, L-threonine, in DR-mediated improvement in organismal healthspan, suggesting it could be an effective intervention for preventing senescence progression and age-induced ferroptosis.

Metabolome Profiling in Aging Studies

Organism aging is closely related to systemic metabolic changes. However, due to the multilevel and network nature of metabolic pathways, it is difficult to understand these connections. Today, scientists are trying to solve this problem using one of the main approaches of metabolomics-untargeted metabolome profiling. The purpose of this publication is to review metabolomic studies based on such profiling, both in animal models and in humans. This review describes metabolites that vary significantly across age groups and include carbohydrates, amino acids, carnitines, biogenic amines, and lipids. Metabolic pathways associated with the aging process are also shown, including those associated with amino acid, lipid, and energy metabolism. The presented data reveal the mechanisms of aging and can be used as a basis for monitoring biological age and predicting age-related diseases in the early stages of their development.

Phosphatidylethanolamine N-Methyltransferase Knockout Modulates Metabolic Changes in Aging Mice

Phospholipid metabolism, including phosphatidylcholine (PC) biosynthesis, is crucial for various biological functions and is associated with longevity. Phosphatidylethanolamine N-methyltransferase (PEMT) is a protein that catalyzes the biosynthesis of PC, the levels of which change in various organs such as the brain and kidneys during aging. However, the role of PEMT for systemic PC supply is not fully understood. To address how PEMT affects aging-associated energy metabolism in tissues responsible for nutrient absorption, lipid storage, and energy consumption, we employed NMR-based metabolomics to study the liver, plasma, intestine (duodenum, jejunum, and ileum), brown/white adipose tissues (BAT and WAT), and skeletal muscle of young (9-10 weeks) and old (91-132 weeks) wild-type (WT) and PEMT knockout (KO) mice. We found that the effect of PEMT-knockout was tissue-specific and age-dependent. A deficiency of PEMT affected the metabolome of all tissues examined, among which the metabolome of BAT from both young and aged KO mice was dramatically changed in comparison to the WT mice, whereas the metabolome of the jejunum was only slightly affected. As for aging, the absence of PEMT increased the divergence of the metabolome during the aging of the liver, WAT, duodenum, and ileum and decreased the impact on skeletal muscle. Overall, our results suggest that PEMT plays a previously underexplored, critical role in both aging and energy metabolism.

A Lactobacilli diet that confers MRSA resistance causes amino acid depletion and increased antioxidant levels in the C. elegans host

Probiotic bacteria are increasingly popular as dietary supplements and have the potential as alternatives to traditional antibiotics. We have recently shown that pretreatment with Lactobacillus spp. Lb21 increases the life span of C. elegans and results in resistance toward pathogenic methicillin-resistant Staphylococcus aureus (MRSA). The Lb21-mediated MRSA resistance is dependent on the DBL-1 ligand of the TGF-β signaling pathway. However, the underlying changes at the metabolite level are not understood which limits the application of probiotic bacteria as timely alternatives to traditional antibiotics. In this study, we have performed untargeted nuclear magnetic resonance-based metabolic profiling. We report the metabolomes of Lactobacillus spp. Lb21 and control E. coli OP50 bacteria as well as the nematode-host metabolomes after feeding with these diets. We identify 48 metabolites in the bacteria samples and 51 metabolites in the nematode samples and 63 across all samples. Compared to the control diet, the Lactobacilli pretreatment significantly alters the metabolic profile of the worms. Through sparse Partial Least Squares discriminant analyses, we identify the 20 most important metabolites distinguishing probiotics from the regular OP50 food and worms fed the two different bacterial diets, respectively. Among the changed metabolites, we find lower levels of essential amino acids as well as increased levels of the antioxidants, ascorbate, and glutathione. Since the probiotic diet offers significant protection against MRSA, these metabolites could provide novel ways of combatting MRSA infections.

Regulation of the lysosome by sphingolipids: potential role in aging

Sphingolipids are a class of bioactive complex lipids that have been closely associated with aging and aging-related diseases. However, the mechanism through which sphingolipids control aging has long been a mystery. Emerging studies reveal that sphingolipids exert tight control over lysosomal homeostasis and function, as evidenced by sphingolipid-related diseases, including but not limited to lysosomal storage disorders. These diseases are defined by primary lysosomal defects and a few secondary defects such as mitochondrial dysfunction. Intriguingly, recent research indicates that the majority of these defects are also associated with aging, implying that sphingolipid-related diseases and aging may share common mechanisms. We propose that the lysosome is a pivotal hub for sphingolipid-mediated aging regulation. This review discusses the critical roles of sphingolipid metabolism in regulating various lysosomal functions, with an emphasis on how such regulation may contribute to aging and aging-related diseases.

Caenorhabditis elegans deep lipidome profiling by using integrative mass spectrometry acquisitions reveals significantly altered lipid networks

Lipidomics coverage improvement is essential for functional lipid and pathway construction. A powerful approach to discovering organism lipidome is to combine various data acquisitions, such as full scan mass spectrometry (full MS), data-dependent acquisition (DDA), and data-independent acquisition (DIA). Caenorhabditis elegans (C. elegans) is a useful model for discovering toxic-induced metabolism, high-throughput drug screening, and a variety of human disease pathways. To determine the lipidome of C. elegans and investigate lipid disruption from the molecular level to the system biology level, we used integrative data acquisition. The methyl-tert-butyl ether method was used to extract L4 stage C. elegans after exposure to triclosan (TCS), perfluorooctanoic acid, and nanopolystyrene (nPS). Full MS, DDA, and DIA integrations were performed to comprehensively profile the C. elegans lipidome by Q-Exactive Plus MS. All annotated lipids were then analyzed using lipid ontology and pathway analysis. We annotated up to 940 lipids from 20 lipid classes involved in various functions and pathways. The biological investigations revealed that when C. elegans were exposed to nPS, lipid droplets were disrupted, whereas plasma membrane-functionalized lipids were likely to be changed in the TCS treatment group. The nPS treatment caused a significant disruption in lipid storage. Triacylglycerol, glycerophospholipid, and ether class lipids were those primarily hindered by toxicants. Finally, toxicant exposure frequently involved numerous lipid-related pathways, including the phosphoinositide 3-kinase/protein kinase B pathway. In conclusion, an integrative data acquisition strategy was used to characterize the C. elegans lipidome, providing valuable biological insights into hypothesis generation and validation.

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Multiple data acquisitions were used to profile the lipidome of C. elegans.

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940 detected lipids of 20 main classes involved in various pathways.

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Relevant hypotheses were generated using high-coverable lipidomics and pathways analysis.

Healthy aging and muscle function are positively associated with NAD+ abundance in humans

Skeletal muscle is greatly affected by aging, resulting in a loss of metabolic and physical function. However, the underlying molecular processes and how (lack of) physical activity is involved in age-related metabolic decline in muscle function in humans is largely unknown. Here, we compared, in a cross-sectional study, the muscle metabolome from young to older adults, whereby the older adults were exercise trained, had normal physical activity levels or were physically impaired. Nicotinamide adenine dinucleotide (NAD+) was one of the most prominent metabolites that was lower in older adults, in line with preclinical models. This lower level was even more pronounced in impaired older individuals, and conversely, exercise-trained older individuals had NAD+ levels that were more similar to those found in younger individuals. NAD+ abundance positively correlated with average number of steps per day and mitochondrial and muscle functioning. Our work suggests that a clear association exists between NAD+ and health status in human aging.

Reduced ech-6 expression attenuates fat-induced lifespan shortening in C. elegans

Deregulated energy homeostasis represents a hallmark of aging and results from complex gene-by-environment interactions. Here, we discovered that reducing the expression of the gene ech-6 encoding enoyl-CoA hydratase remitted fat diet-induced deleterious effects on lifespan in Caenorhabditis elegans, while a basal expression of ech-6 was important for survival under normal dietary conditions. Lipidomics revealed that supplementation of fat in ech-6-silenced worms had marginal effects on lipid profiles, suggesting an alternative fat utilization for energy production. Transcriptomics further suggest a causal relation between the lysosomal pathway, energy production, and the longevity effect conferred by the interaction between ech-6 and fat diets. Indeed, enhancing energy production from endogenous fat by overexpressing lysosomal lipase lipl-4 recapitulated the lifespan effects of fat diets on ech-6-silenced worms. Collectively, these results suggest that the gene ech-6 is potential modulator of metabolic flexibility and may be a target for promoting metabolic health and longevity.

Comparative metabolomics with Metaboseek reveals functions of a conserved fat metabolism pathway in C. elegans

Untargeted metabolomics via high-resolution mass spectrometry can reveal more than 100,000 molecular features in a single sample, many of which may represent unidentified metabolites, posing significant challenges to data analysis. We here introduce Metaboseek, an open-source analysis platform designed for untargeted comparative metabolomics and demonstrate its utility by uncovering biosynthetic functions of a conserved fat metabolism pathway, α-oxidation, using C. elegans as a model. Metaboseek integrates modules for molecular feature detection, statistics, molecular formula prediction, and fragmentation analysis, which uncovers more than 200 previously uncharacterized α-oxidation-dependent metabolites in an untargeted comparison of wildtype and α-oxidation-defective hacl-1 mutants. The identified metabolites support the predicted enzymatic function of HACL-1 and reveal that α-oxidation participates in metabolism of endogenous β-methyl-branched fatty acids and food-derived cyclopropane lipids. Our results showcase compound discovery and feature annotation at scale via untargeted comparative metabolomics applied to a conserved primary metabolic pathway and suggest a model for the metabolism of cyclopropane lipids.

Untargeted mass spectrometry-based metabolomics can reveal new biochemistry, but data analysis is challenging. Here, the authors develop Metaboseek, an open-source software that facilitates metabolite discovery, and apply it to characterize fatty acid alpha-oxidation in C. elegans.

Multi-omics analysis identifies essential regulators of mitochondrial stress response in two wild-type C. elegans strains

The mitochondrial unfolded protein response (UPRmt) is a promising pharmacological target for aging and age-related diseases. However, the integrative analysis of the impact of UPRmt activation on different signaling layers in animals with different genetic backgrounds is lacking. Here, we applied systems approaches to investigate the effect of UPRmt induced by doxycycline (Dox) on transcriptome, proteome, and lipidome in two genetically divergent worm strains, named N2 and CB4856. From the integrated omics datasets, we found that Dox prolongs lifespan of both worm strains through shared and strain-specific mechanisms. Specifically, Dox strongly impacts mitochondria, upregulates defense response, and lipid metabolism, while decreasing triglycerides. We further validated that lipid genes acs-2/20 and fat-7/6 were required for Dox-induced UPRmt and longevity in N2 and CB4856 worms, respectively. Our data have translational value as they indicate that the beneficial effects of Dox-induced UPRmt on lifespan are consistent across different genetic backgrounds through different regulators.

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Dox extends lifespan of N2 and CB4856 via shared and strain-specific mechanisms

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Dox controls mitochondria, defense responses, and lipid metabolism in both strains

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Dox-mediated longevity requires acs-2/20 in N2 and fat-7/6 in CB4856 worms

The Crucial Roles of Phospholipids in Aging and Lifespan Regulation

Phospholipids are major membrane lipids that consist of lipid bilayers. This basic cellular structure acts as a barrier to protect the cell against various environmental insults and more importantly, enables multiple cellular processes to occur in subcellular compartments. Numerous studies have linked the complexity of membrane lipids to signal transductions, organelle functions, as well as physiological processes, and human diseases. Recently, crucial roles for membrane lipids in the aging process are beginning to emerge. In this study, we summarized current advances in our understanding of the relationship between membrane lipids and aging with an emphasis on phospholipid species. We surveyed how major phospholipid species change with age in different organisms and tissues, and some common patterns of membrane lipid change during aging were proposed. Further, the functions of different phospholipid molecules in regulating healthspan and lifespan, as well as their potential mechanisms of action, were also discussed.

DO-SRS imaging of metabolic dynamics in aging Drosophila

Emerging studies have shown that lipid metabolism plays an important role in aging. High resolution in situ imaging of lipid metabolic dynamics inside cells and tissues affords a novel and potent approach for understanding many biological processes such as aging. Here we established a new optical imaging platform that combines D2O-probed stimulated Raman scattering (DO-SRS) imaging microscopy and a Drosophila model to directly visualize metabolic activities in situ during aging. The sub-cellular spatial distribution of de novo lipogenesis in the fat body was quantitatively imaged and examined. We discovered a dramatic decrease in lipid turnover in 35-day-old flies. Decreases in protein turnover occurred earlier than lipids (25-day vs. 35-day), and there are many proteins localized on the cell and lipid droplet membrane. This suggests that protein metabolism may act as a prerequisite for lipid metabolism during aging. This alteration of maintenance of protein turnover indicates disrupted lipid metabolism. We further found a significantly higher lipid turnover rate in large LDs, indicating more active metabolism in large LDs, suggesting that large and small LDs play different roles in metabolism to maintain cellular homeostasis. This is the first study that directly visualizes spatiotemporal alterations of lipid (and protein) metabolism in Drosophila during the aging process. Our study not only demonstrates a new imaging platform for studying lipid metabolism, but also unravels the important interconnections between lipid metabolism and aging.

Metabolomics profiling reveals the mechanism of caffeic acid in extending lifespan in Drosophila melanogaster

Caffeic acid is a phenolic compound widely synthesized by plants, which has shown health benefits for multiple aging-related diseases. The aim of this study was to investigate the life-extending effect of caffeic acid and its underlying mechanisms. The effects of caffeic acid on lifespan, climbing behavior, starvation resistance, and heat sensitivity of Drosophila melanogaster (D. melanogaster) were evaluated. 1H-NMR-based metabolomics and biochemical detection were performed to explore the potential mechanisms. The results demonstrated that supplementation with caffeic acid extended the lifespan, and improved climbing behavior and stress resistance in D. melanogaster. Additionally, continuous supplementation with caffeic acid caused the metabolic profile of 30-day D. melanogaster closer to that of 3-day D. melanogaster, among which 17 differential metabolites were significantly regulated by caffeic acid, involved in amino acid metabolism and mitochondrial metabolism. Furthermore, caffeic acid significantly prevented oxidative damage and improved mitochondrial function. Correlation analysis indicated that the differential metabolites regulated by caffeic acid were correlated with its antioxidant effect and mitochondrial improvement function. In conclusion, our data support that caffeic acid could extend lifespan in D. melanogaster through regulation of metabolic abnormality and improvement of mitochondrial function.

SID-2 negatively regulates development likely independent of nutritional dsRNA uptake

RNA interference (RNAi) is a gene regulatory mechanism based on RNA-RNA interaction conserved through eukaryotes. Surprisingly, many animals can take-up human-made double stranded RNA (dsRNA) from the environment to initiate RNAi suggesting a mechanism for dsRNA-based information exchange between organisms and their environment. However, no naturally occurring example has been identified since the discovery of the phenomenon 22 years ago. Therefore it remains enigmatic why animals are able to take up dsRNA. Here, we explore other possible functions by performing phenotypic studies of dsRNA uptake deficient sid-2 mutants in Caenorhabditis elegans. We find that SID-2 does not have a nutritional role in feeding experiments using genetic sensitized mutants. Furthermore, we use robot assisted imaging to show that sid-2 mutants accelerate growth rate and, by maternal contribution, body length at hatching. Finally, we perform transcriptome and lipidome analysis showing that sid-2 has no effect on energy storage lipids, but affects signalling lipids and the embryo transcriptome. Overall, these results suggest that sid-2 has mild effects on development and is unlikely functioning in the nutritional uptake of dsRNA. These findings broaden our understanding of the biological role of SID-2 and motivate studies identifying the role of environmental dsRNA uptake.

Quo Vadis Caenorhabditis elegans Metabolomics-A Review of Current Methods and Applications to Explore Metabolism in the Nematode

Metabolomics and lipidomics recently gained interest in the model organism Caenorhabditis elegans (C. elegans). The fast development, easy cultivation and existing forward and reverse genetic tools make the small nematode an ideal organism for metabolic investigations in development, aging, different disease models, infection, or toxicology research. The conducted type of analysis is strongly depending on the biological question and requires different analytical approaches. Metabolomic analyses in C. elegans have been performed using nuclear magnetic resonance (NMR) spectroscopy, direct infusion mass spectrometry (DI-MS), gas-chromatography mass spectrometry (GC-MS) and liquid chromatography mass spectrometry (LC-MS) or combinations of them. In this review we provide general information on the employed techniques and their advantages and disadvantages in regard to C. elegans metabolomics. Additionally, we reviewed different fields of application, e.g., longevity, starvation, aging, development or metabolism of secondary metabolites such as ascarosides or maradolipids. We also summarised applied bioinformatic tools that recently have been used for the evaluation of metabolomics or lipidomics data from C. elegans. Lastly, we curated metabolites and lipids from the reviewed literature, enabling a prototypic collection which serves as basis for a future C. elegans specific metabolome database.

Metabolomics and lipidomics in Caenorhabditis elegans using a single-sample preparation

Comprehensive metabolomic and lipidomic mass spectrometry methods are in increasing demand; for instance, in research related to nutrition and aging. The nematode Caenorhabditis elegans is a key model organism in these fields, owing to the large repository of available C. elegans mutants and their convenient natural lifespan. Here, we describe a robust and sensitive analytical method for the semi-quantitative analysis of >100 polar (metabolomics) and >1000 apolar (lipidomics) metabolites in C. elegans, using a single-sample preparation. Our method is capable of reliably detecting a wide variety of biologically relevant metabolic aberrations in, for example, glycolysis and the tricarboxylic acid cycle, pyrimidine metabolism and complex lipid biosynthesis. In conclusion, we provide a powerful analytical tool that maximizes metabolic data yield from a single sample. This article has an associated First Person interview with the joint first authors of the paper.

Caloric restriction creates a metabolic pattern of chronological aging delay that in budding yeast differs from the metabolic design established by two other geroprotectors

Caloric restriction and the tor1Δ mutation are robust geroprotectors in yeast and other eukaryotes. Lithocholic acid is a potent geroprotector in Saccharomycescerevisiae. Here, we used liquid chromatography coupled with tandem mass spectrometry method of non-targeted metabolomics to compare the effects of these three geroprotectors on the intracellular metabolome of chronologically aging budding yeast. Yeast cells were cultured in a nutrient-rich medium. Our metabolomic analysis identified and quantitated 193 structurally and functionally diverse water-soluble metabolites implicated in the major pathways of cellular metabolism. We show that the three different geroprotectors create distinct metabolic profiles throughout the entire chronological lifespan of S. cerevisiae. We demonstrate that caloric restriction generates a unique metabolic pattern. Unlike the tor1Δ mutation or lithocholic acid, it slows down the metabolic pathway for sulfur amino acid biosynthesis from aspartate, sulfate and 5-methyltetrahydrofolate. Consequently, caloric restriction significantly lowers the intracellular concentrations of methionine, S-adenosylmethionine and cysteine. We also noticed that the low-calorie diet, but not the tor1Δ mutation or lithocholic acid, decreases intracellular ATP, increases the ADP:ATP and AMP:ATP ratios, and rises intracellular ADP during chronological aging. We propose a model of how the specific remodeling of cellular metabolism by caloric restriction contributes to yeast chronological aging delay.

Comparison of lipidome profiles of Caenorhabditis elegans-results from an inter-laboratory ring trial

INTRODUCTION

Lipidomic profiling allows 100s if not 1000s of lipids in a sample to be detected and quantified. Modern lipidomics techniques are ultra-sensitive assays that enable the discovery of novel biomarkers in a variety of fields and provide new insight in mechanistic investigations. Despite much progress in lipidomics, there remains, as for all high throughput "omics" strategies, the need to develop strategies to standardize and integrate quality control into studies in order to enhance robustness, reproducibility, and usability of studies within specific fields and beyond.

OBJECTIVES

We aimed to understand how much results from lipid profiling in the model organism Caenorhabditis elegans are influenced by different culture conditions in different laboratories.

METHODS

In this work we have undertaken an inter-laboratory study, comparing the lipid profiles of N2 wild type C. elegans and daf-2(e1370) mutants lacking a functional insulin receptor. Sample were collected from worms grown in four separate laboratories under standardized growth conditions. We used an UPLC-UHR-ToF-MS system allowing chromatographic separation before MS analysis.

RESULTS

We found common qualitative changes in several marker lipids in samples from the individual laboratories. On the other hand, even in this controlled experimental system, the exact fold-changes for each marker varied between laboratories.

CONCLUSION

Our results thus reveal a serious limitation to the reproducibility of current lipid profiling experiments and reveal challenges to the integration of such data from different laboratories.

Investigation of cardiolipin oxidation products as a new endpoint for oxidative stress in C. elegans by means of online two-dimensional liquid chromatography and high-resolution mass spectrometry

The investigation of neurodegenerative and age-related diseases is a highly relevant topic in current research. Especially oxidative stress is thought to be the common underlying mechanism in diseases such as Parkinson's or Alzheimer's disease. The nematode Caenorhabditis elegans (C. elegans) is a prominent model organism, which is often used for such investigations and has gained extensive recognition in research regarding the linkage of reactive oxygen species (ROS) and neurodegeneration. Not only studies regarding genomics and proteomics have been increasingly conducted, also the number of studies based on the lipidome is rising. The phospholipid class of cardiolipin (CL) is a unique lipid class, which is exclusively located in mitochondria and is therefore of great relevance regarding oxidative stress and associated diseases. CL oxidation products have become a prominent marker for oxidative stress in various organisms. However, the CL distribution in the nematode C. elegans is still scarcely known on the molecular level and oxidation products have not yet been identified. In this work, we demonstrate the importance of CL distribution and the applicability of CL oxidation products as a sensitive marker for oxidative stress in C. elegans. For this reason, the CL distribution was determined by means of online two-dimensional liquid chromatography hyphenated with high-resolution mass spectrometry (2D-LC/HRMS). Subsequently, worms were treated with tert-butyl hydroperoxide (tBOOH) in order to provoke oxidative stress and induce the artificial formation of oxidized CL. We were able to detect increasing amounts of CL oxidation products of highly unsaturated CL species in a concentration-dependent manner. This finding emphasizes the great potential of CL oxidation products as a sensitive marker substance of oxidative stress in C. elegans, which is not only directly linked to mitochondria function but also favourable to other oxidative stress markers in terms of the needed sample material, relative substance stability and specificity of the oxidation site.

Loss of metabolic plasticity underlies metformin toxicity in aged Caenorhabditis elegans

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

Caenorhabditis elegans as a Useful Model for Studying Aging Mutations

The Caenorhabditis elegans genome possesses homologs of about two-thirds of all human disease genes. Based on its physiological aging characteristics and superiority, the use of C. elegans as a model system for studies on aging, age-related diseases, mechanisms of longevity, and drug screening has been widely acknowledged in recent decades. Lifespan increasing mutations in C. elegans were found to delay aging by impinging several signaling pathways and related epigenetic modifications, including the insulin/IGF-1 signaling (IIS), AMP-activated protein kinase (AMPK), and mechanistic target of rapamycin (mTOR) pathways. Interestingly, dietary restriction (DR) has been shown to increase the lifespan of numerous metazoans and protect them from multiple age-related pathologies. However, the underlying molecular mechanisms are unclear. In recent decades, C. elegans has been used as a unique model system for high-throughput drug screening. Here, we review C. elegans mutants exhibiting increased in lifespan and age-dependent changes under DR, as well as the utility of C. elegans for drug screening. Thus, we provide evidence for the use of this model organism in research on the prevention of aging.

Metabolism of sleep and aging: Bridging the gap using metabolomics

Sleep is a conserved behavior across the evolutionary timescale. Almost all known animal species demonstrate sleep or sleep like states. Despite extensive study, the mechanistic aspects of sleep need are not very well characterized. Sleep appears to be needed to generate resources that are utilized during the active stage/wakefulness as well as clearance of waste products that accumulate during wakefulness. From a metabolic perspective, this means sleep is crucial for anabolic activities. Decrease in anabolism and build-up of harmful catabolic waste products is also a hallmark of aging processes. Through this lens, sleep and aging processes are remarkably parallel- for example behavioral studies demonstrate an interaction between sleep and aging. Changes in sleep behavior affect neurocognitive phenotypes important in aging such as learning and memory, although the underlying connections are largely unknown. Here we draw inspiration from the similar metabolic effects of sleep and aging and posit that large scale metabolic phenotyping, commonly known as metabolomics, can shed light to interleaving effects of sleep, aging and progression of diseases related to aging. In this review, data from recent sleep and aging literature using metabolomics as principal molecular phenotyping methods is collated and compared. The present data suggests that metabolic effects of aging and sleep also demonstrate similarities, particularly in lipid metabolism and amino acid metabolism. Some of these changes also overlap with metabolomic data available from clinical studies of Alzheimer's disease. Together, metabolomic technologies show promise in elucidating interleaving effects of sleep, aging and progression of aging disorders at a molecular level.

A Comprehensive Understanding of Dietary Effects on C. elegans Physiology

Diet has been shown to play an important role in human physiology. It is a predominant exogenous factor regulating the composition of gut microbiota, and dietary intervention holds promise for treatment of diseases such as obesity, type 2 diabetes, and malnutrition. Furthermore, it was reported that diet has significant effects on physiological processes of C. elegans, including reproduction, fat storage, and aging. To reveal novel signaling pathways responsive to different diets, C. elegans and its bacterial diet were used as an interspecies model system to mimic the interaction between host and gut microbiota. Most signaling pathways identified in C. elegans are highly conserved across different species, including humans. A better understanding of these pathways can, therefore, help to develop interventions for human diseases. In this article, we summarize recent achievements on molecular mechanisms underlying the response of C. elegans to different diets and discuss their relevance to human health.

Host-Microbe-Drug-Nutrient Screen Identifies Bacterial Effectors of Metformin Therapy

Metformin is the first-line therapy for treating type 2 diabetes and a promising anti-aging drug. We set out to address the fundamental question of how gut microbes and nutrition, key regulators of host physiology, affect the effects of metformin. Combining two tractable genetic models, the bacterium E. coli and the nematode C. elegans, we developed a high-throughput four-way screen to define the underlying host-microbe-drug-nutrient interactions. We show that microbes integrate cues from metformin and the diet through the phosphotransferase signaling pathway that converges on the transcriptional regulator Crp. A detailed experimental characterization of metformin effects downstream of Crp in combination with metabolic modeling of the microbiota in metformin-treated type 2 diabetic patients predicts the production of microbial agmatine, a regulator of metformin effects on host lipid metabolism and lifespan. Our high-throughput screening platform paves the way for identifying exploitable drug-nutrient-microbiome interactions to improve host health and longevity through targeted microbiome therapies. VIDEO ABSTRACT.

Metabolic regulation of lifespan from a C. elegans perspective

Decline of cellular functions especially cognitive is a major deficit that arises with age in humans. Harnessing the strengths of small and genetic tractable model systems has revealed key conserved regulatory biochemical and signaling pathways that control aging. Here, we review some of the key signaling and biochemical pathways that coordinate aging processes with special emphasis on Caenorhabditis elegans as a model system and discuss how nutrients and metabolites can regulate lifespan by coordinating signaling and epigenetic programs. We focus on central nutrient-sensing pathways such as mTOR and insulin/insulin-like growth factor signaling and key transcription factors including the conserved basic helix-loop-helix transcription factor HLH-30/TFEB.

DAF-16 stabilizes the aging transcriptome and is activated in mid-aged Caenorhabditis elegans to cope with internal stress

The roles and regulatory mechanisms of transcriptome changes during aging are unclear. It has been proposed that the transcriptome suffers decay during aging owing to age‐associated down‐regulation of transcription factors. In this study, we characterized the role of a transcription factor DAF‐16, which is a highly conserved lifespan regulator, in the normal aging process of Caenorhabditis elegans. We found that DAF‐16 translocates into the nucleus in aged wild‐type worms and activates the expression of hundreds of genes in response to age‐associated cellular stress. Most of the age‐dependent DAF‐16 targets are different from the canonical DAF‐16 targets downstream of insulin signaling. This and other evidence suggest that activation of DAF‐16 during aging is distinct from activation of DAF‐16 due to reduced signaling from DAF‐2. Further analysis showed that it is due in part to a loss of proteostasis during aging. We also found that without daf‐16, dramatic gene expression changes occur as early as on adult day 2, indicating that DAF‐16 acts to stabilize the transcriptome during normal aging. Our results thus reveal that normal aging is not simply a process in which the gene expression program descends into chaos due to loss of regulatory activities; rather, there is active transcriptional regulation during aging.

The sphingolipidome of the model organism Caenorhabditis elegans

Sphingolipids are important lipids and integral members of membranes, where they form small microdomains called lipid rafts. These rafts are enriched in cholesterol and sphingolipids, which influences biophysical properties. Interestingly, the membranes of the biomedical model organism Caenorhabditis elegans contain only low amounts of cholesterol. Sphingolipids in C. elegans are based on an unusual C17iso branched sphingoid base. In order to analyze and the sphingolipidome of C. elegans in more detail, we performed fractionation of lipid extracts and depletion of glycero- and glycerophospholipids together with in-depth analysis using UPLC-UHR-ToF-MS. In total we were able to detect 82 different sphingolipids from different classes, including several isomeric species.

Age-dependent changes and biomarkers of aging in Caenorhabditis elegans

Caenorhabditis elegans is an exceptionally valuable model for aging research because of many advantages, including its genetic tractability, short lifespan, and clear age‐dependent physiological changes. Aged C. elegans display a decline in their anatomical and functional features, including tissue integrity, motility, learning and memory, and immunity. Caenorhabditis elegans also exhibit many age‐associated changes in the expression of microRNAs and stress‐responsive genes and in RNA and protein quality control systems. Many of these age‐associated changes provide information on the health of the animals and serve as valuable biomarkers for aging research. Here, we review the age‐dependent changes in C. elegans and their utility as aging biomarkers indicative of the physiological status of aging.

Glycine promotes longevity in Caenorhabditis elegans in a methionine cycle-dependent fashion

The deregulation of metabolism is a hallmark of aging. As such, changes in the expression of metabolic genes and the profiles of amino acid levels are features associated with aging animals. We previously reported that the levels of most amino acids decline with age in Caenorhabditis elegans (C. elegans). Glycine, in contrast, substantially accumulates in aging C. elegans. In this study we show that this is coupled to a decrease in gene expression of enzymes important for glycine catabolism. We further show that supplementation of glycine significantly prolongs C. elegans lifespan, and early adulthood is important for its salutary effects. Moreover, supplementation of glycine ameliorates specific transcriptional changes that are associated with aging. Glycine feeds into the methionine cycle. We find that mutations in components of this cycle, methionine synthase (metr-1) and S-adenosylmethionine synthetase (sams-1), completely abrogate glycine-induced lifespan extension. Strikingly, the beneficial effects of glycine supplementation are conserved when we supplement with serine, which also feeds into the methionine cycle. RNA-sequencing reveals a similar transcriptional landscape in serine- and glycine-supplemented worms both demarked by widespread gene repression. Taken together, these data uncover a novel role of glycine in the deceleration of aging through its function in the methionine cycle.

Multi-Omics and Genome-Scale Modeling Reveal a Metabolic Shift During C. elegans Aging

In this contribution, we describe a multi-omics systems biology study of the metabolic changes that occur during aging in Caenorhabditis elegans. Sampling several time points from young adulthood until early old age, our study covers the full duration of aging and include transcriptomics, and targeted MS-based metabolomics. In order to focus on the metabolic changes due to age we used two strains that are metabolically close to wild-type, yet are conditionally non-reproductive. Using these data in combination with a whole-genome model of the metabolism of C. elegans and mathematical modeling, we predicted metabolic fluxes during early aging. We find that standard Flux Balance Analysis does not accurately predict in vivo measured fluxes nor age-related changes associated with the Citric Acid cycle. We present a novel Flux Balance Analysis method where we combined biomass production and targeted metabolomics information to generate an objective function that is more suitable for aging studies. We validated this approach with a detailed case study of the age-associated changes in the Citric Acid cycle. Our approach provides a comprehensive time-resolved multi-omics and modeling resource for studying the metabolic changes during normal aging in C. elegans.

Linking Lipid Metabolism to Chromatin Regulation in Aging

The lifespan of an organism is strongly influenced by environmental factors (including diet) and by internal factors (notably reproductive status). Lipid metabolism is critical for adaptation to external conditions or reproduction. Interestingly, specific lipid profiles are associated with longevity, and increased uptake of certain lipids extends longevity in Caenorhabditis elegans and ameliorates disease phenotypes in humans. How lipids impact longevity, and how lipid metabolism is regulated during aging, is just beginning to be unraveled. This review describes recent advances in the regulation and role of lipids in longevity, focusing on the interaction between lipid metabolism and chromatin states in aging and age-related diseases.

Quantitative Imaging of Lipid Synthesis and Lipolysis Dynamics in Caenorhabditis elegans by Stimulated Raman Scattering Microscopy

Quantitative methods to precisely measure cellular states in vivo have become increasingly important and desirable in modern biology. Recently, stimulated Raman scattering (SRS) microscopy has emerged as a powerful tool to visualize small biological molecules tagged with alkyne (C≡C) or carbon-deuterium (C-D) bonds in the cell-silent region. In this study, we developed a technique based on SRS microscopy of vibrational tags for quantitative imaging of lipid synthesis and lipolysis in live animals. The technique aims to overcome the major limitations of conventional fluorescent staining and lipid extraction methods that do not provide the capability of in vivo quantitative analysis. Specifically, we used three bioorthogonal lipid molecules (the alkyne-tagged fatty acid 17-ODYA, deuterium-labeled saturated fatty acid PA-D₃₁, and unsaturated fatty acid OA-D₃₄) to investigate the metabolic dynamics of lipid droplets (LDs) in live Caenorhabditis elegans ( C. elegans). Using a hyperspectral SRS (hsSRS) microscope and subtraction method, the interfering non-Raman background was eliminated to improve the accuracy of lipid quantification. A linear relationship between SRS signals and fatty acid molar concentrations was accurately established. With this quantitative analysis tool, we imaged and determined the changes in concentration of the three fatty acids in LDs of fed or starved adult C. elegans. Using the hsSRS imaging mode, we also observed the desaturation of fatty acids in adult C. elegans via spectral analysis on the SRS signals from LDs. The results demonstrated the unique capability of hsSRS microscopy in quantitative analysis of lipid metabolism in vivo.

Modeling Meets Metabolomics-The WormJam Consensus Model as Basis for Metabolic Studies in the Model Organism Caenorhabditis elegans

Metabolism is one of the attributes of life and supplies energy and building blocks to organisms. Therefore, understanding metabolism is crucial for the understanding of complex biological phenomena. Despite having been in the focus of research for centuries, our picture of metabolism is still incomplete. Metabolomics, the systematic analysis of all small molecules in a biological system, aims to close this gap. In order to facilitate such investigations a blueprint of the metabolic network is required. Recently, several metabolic network reconstructions for the model organism Caenorhabditis elegans have been published, each having unique features. We have established the WormJam Community to merge and reconcile these (and other unpublished models) into a single consensus metabolic reconstruction. In a series of workshops and annotation seminars this model was refined with manual correction of incorrect assignments, metabolite structure and identifier curation as well as addition of new pathways. The WormJam consensus metabolic reconstruction represents a rich data source not only for in silico network-based approaches like flux balance analysis, but also for metabolomics, as it includes a database of metabolites present in C. elegans, which can be used for annotation. Here we present the process of model merging, correction and curation and give a detailed overview of the model. In the future it is intended to expand the model toward different tissues and put special emphasizes on lipid metabolism and secondary metabolism including ascaroside metabolism in accordance to their central role in C. elegans physiology.

Identification of key pathways and metabolic fingerprints of longevity in C. elegans

Impaired insulin/IGF-1 signaling (IIS) and caloric restriction (CR) prolong lifespan in the nematode C. elegans. However, a cross comparison of these longevity pathways using a multi-omics integration approach is lacking. In this study, we aimed to identify key pathways and metabolite fingerprints of longevity that are shared between IIS and CR worm models using multi-omics integration. We generated transcriptomics and metabolomics data from long-lived worm strains, i.e. daf-2 (impaired IIS) and eat-2 (CR model) and compared them with the wild-type strain N2. Transcriptional profiling identified shared longevity signatures, such as an upregulation of lipid storage and defense responses, and downregulation of macromolecule synthesis and developmental processes. Metabolomics profiling identified an increase in the levels of glycerol‑3P, adenine, xanthine, and AMP, and a decrease in the levels of the amino acid pool, as well as the C18:0, C17:1, C19:1, C20:0 and C22:0 fatty acids. After we integrated transcriptomics and metabolomics data based on the annotations in KEGG, our results highlighted increased amino acid metabolism and an upregulation of purine metabolism as a commonality between the two long-lived mutants. Overall, our findings point towards the existence of shared metabolic pathways that are likely important for lifespan extension and provide novel insights into potential regulators and metabolic fingerprints for longevity.

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Multi-omics integration identified common longevity signatures.

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Amino acid metabolism was increased in both daf-2 and eat-2 mutants.

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Purine biosynthesis pathway was enhanced in the long-lived mutants.

Emerging topics in C. elegans aging research: Transcriptional regulation, stress response and epigenetics

Key discoveries in aging research have been made possible with the use of model organisms. Caenorhabditis elegans is a short-lived nematode that has become a well-established system to study aging. The practicality and powerful genetic manipulations associated with this metazoan have revolutionized our ability to understand how organisms age. 25 years after the publication of the discovery of the daf-2 gene as a genetic modifier of lifespan, C. elegans remains as relevant as ever in the quest to understand the process of aging. Nematode aging research has proven useful in identifying transcriptional regulators, small molecule signals, cellular mechanisms, epigenetic modifications associated with stress resistance and longevity, and lifespan-extending compounds. Here, we review recent discoveries and selected topics that have emerged in aging research using this incredible little worm.

Natural genetic variation in C. elegans identified genomic loci controlling metabolite levels

Metabolic homeostasis is sustained by complex biological networks that respond to nutrient availability. Genetic and environmental factors may disrupt this equilibrium, leading to metabolic disorders, including obesity and type 2 diabetes. To identify the genetic factors controlling metabolism, we performed quantitative genetic analysis using a population of 199 recombinant inbred lines (RILs) in the nematode Caenorhabditis elegans We focused on the genomic regions that control metabolite levels by measuring fatty acid (FA) and amino acid (AA) composition in the RILs using targeted metabolomics. The genetically diverse RILs showed a large variation in their FA and AA levels with a heritability ranging from 32% to 82%. We detected strongly co-correlated metabolite clusters and 36 significant metabolite quantitative trait loci (mQTL). We focused on mQTL displaying highly significant linkage and heritability, including an mQTL for the FA C14:1 on Chromosome I, and another mQTL for the FA C18:2 on Chromosome IV. Using introgression lines (ILs), we were able to narrow down both mQTL to a 1.4-Mbp and a 3.6-Mbp region, respectively. RNAi-based screening focusing on the Chromosome I mQTL identified several candidate genes for the C14:1 mQTL, including lagr-1, Y87G2A.2, nhr-265, nhr-276, and nhr-81 Overall, this systems approach provides us with a powerful platform to study the genetic basis of C. elegans metabolism. Furthermore, it allows us to investigate interventions such as nutrients and stresses that maintain or disturb the regulatory network controlling metabolic homeostasis, and identify gene-by-environment interactions.

Metabolic Flexibility as an Adaptation to Energy Resources and Requirements in Health and Disease

The ability to efficiently adapt metabolism by substrate sensing, trafficking, storage, and utilization, dependent on availability and requirement, is known as metabolic flexibility. In this review, we discuss the breadth and depth of metabolic flexibility and its impact on health and disease. Metabolic flexibility is essential to maintain energy homeostasis in times of either caloric excess or caloric restriction, and in times of either low or high energy demand, such as during exercise. The liver, adipose tissue, and muscle govern systemic metabolic flexibility and manage nutrient sensing, uptake, transport, storage, and expenditure by communication via endocrine cues. At a molecular level, metabolic flexibility relies on the configuration of metabolic pathways, which are regulated by key metabolic enzymes and transcription factors, many of which interact closely with the mitochondria. Disrupted metabolic flexibility, or metabolic inflexibility, however, is associated with many pathological conditions including metabolic syndrome, type 2 diabetes mellitus, and cancer. Multiple factors such as dietary composition and feeding frequency, exercise training, and use of pharmacological compounds, influence metabolic flexibility and will be discussed here. Last, we outline important advances in metabolic flexibility research and discuss medical horizons and translational aspects.

In vitro and in vivo defensive effect of probiotic LAB against Pseudomonas aeruginosa using Caenorhabditis elegans model

This study aimed to investigate in vitro and in vivo the probiotic characteristics of lactic acid bacteria (LAB) isolated from Korean traditional fermented foods. Caenorhabditis elegans  (C. elegans) was used for analytical assays of fertility, chemotaxis, life-span, worm-killing and bacterial colonization in the intestinal lumen of the worm. All 35 strains of LAB reduced fertility and slowed development in the worms. The worm-killing assay showed that LAB significantly increased the lifespan (P < 0.05) and reduced the susceptibility to virulent PA14; however, the heat-killed LAB did not. The bacterial colonization assay revealed that LAB proliferated and protected the gut of the worm against infection by Pseudomonas aeruginosa PA14. In addition, specific LAB Pediococcus acidilactici(P. acidilactici DM-9), Pediococcus brevis (L. brevis SDL1411), and Pediococcus pentosaceus (P. pentosaceus SDL1409) strains showed acid resistance (66-91%), resistance to pepsin (64-67%) and viability in simulated intestinal fluid (67-73%) based on in vitro probiotic analyses. Taken together, these results suggest that C. elegans may be a tractable model for screening efficient probiotics.