Abnormal nutrient metabolism is a hallmark of aging, and the underlying genetic and nutritional framework is rapidly being uncovered, particularly using C. elegans as a model. However, the direct metabolic consequences of perturbations in life history of C. elegans remain to be clarified. Based on recent advances in the metabolomics field, we optimized and validated a sensitive mass spectrometry (MS) platform for identification of major metabolite classes in worms and applied it to study age and diet related changes. Using this platform that allowed detection of over 600 metabolites in a sample of 2500 worms, we observed marked changes in fatty acids, amino acids and phospholipids during worm life history, which were independent from the germ-line. Worms underwent a striking shift in lipid metabolism after early adulthood that was at least partly controlled by the metabolic regulator AAK-2/AMPK. Most amino acids peaked during development, except aspartic acid and glycine, which accumulated in aged worms. Dietary intervention also influenced worm metabolite profiles and the regulation was highly specific depending on the metabolite class. Altogether, these MS-based methods are powerful tools to perform worm metabolomics for aging and metabolism-oriented studies.

Mitochondrial dysfunction is at the core of many diseases, ranging from inherited metabolic diseases to common conditions that are associated with ageing. While associations between ageing and mitochondrial function have been identified using mammalian models, much of the mechanistic insight has emerged from C. elegans. Mitochondrial respiration is recognized as an indicator of mitochondrial health. Seahorse XF96 respirometers are the state-of-the-art platform to assess respiration in cells, and we adapted the technique for applications involving C. elegans. Here, we provide a detailed protocol to optimise and measure respiration in C. elegans with the XF96 respirometer, including the interpretation of parameters and results. The protocol takes ~2 days to complete, excluding time spent culturing C. elegans, and includes (i) the preparation of C. elegans samples, (ii) selection and loading of compounds to be injected, (iii) preparing and executing a run with the XF96 respirometer, and (iv) post-experimental data-analysis, including normalization. In addition, we compare our XF96 application with other existing techniques, including the 8-well Seahorse XFp. The main benefits of the XF96 include the limited number of worms required and high-throughput capacity due to 96-well format.

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.

Wnt signaling represents a highly versatile signaling system, which plays diverse and critical roles in various aspects of neural development. Sensory neurons of the dorsal root ganglia require Wnt signaling for initial cell-fate determination as well as patterning and synapse formation. Here we report that Wnt signaling pathways persist in adult sensory neurons and play a functional role in their sensitization in a pathophysiological context. We observed that Wnt3a recruits the Wnt-calcium signaling pathway and the Wnt planar cell polarity pathway in peripheral nerves to alter pain sensitivity in a modality-specific manner and we elucidated underlying mechanisms. In contrast, biochemical, pharmacological, and genetic studies revealed lack of functional relevance for the classical canonical β-catenin pathway in peripheral sensory neurons in acute modulation of nociception. Finally, this study provides proof-of-concept for a translational potential for Wnt3a-Frizzled3 signaling in alleviating disease-related pain hypersensitivity in cancer-associated pain in vivo.

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.

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 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, Y87G2A.2, ,, and Overall, this systems approach provides us with a powerful platform to study the genetic basis of 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 homeostasis is sustained by complex biological networks responding to nutrient availability. Disruption of this equilibrium involving intricate interactions between genetic and environmental factors can lead to metabolic disorders, including obesity and type 2 diabetes.To identify the genetic factors controlling metabolism, we applied a quantitative genetic strategy using a Caenorhabditis elegans population consisting of 199 recombinant inbred lines (RILs) originally derived from crossing parental strains Bristol N2 and Hawaii CB4856.We focused on the genetic factors that control metabolite levels and measured fatty acid (FA) and amino acid (AA) composition in the 199 RILs using targeted metabolomics. For both FA and AA profiles, we observed large variation in metabolite levels with 32-82% heritability between the RILs. We performed metabolite-metabolite correlation analysis and detected strongly co-correlated metabolite clusters. To identify natural genetic variants responsible for the observed metabolite variations, we performed QTL mapping and detected 36 significant metabolite QTL (mQTL). We focused on the mQTL that displayed high 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. Overall, this systems approach provides us with a powerful platform to study the genetic basis of C. elegans metabolism. It also allows us to investigate additional interventions, such as nutrients and stresses that maintain or disturb the regulatory network controlling metabolic homeostasis, and identify gene-by-environment interactions.

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 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, also driving the methionine cycle. RNA sequencing of serine-and glycine-supplemented worms reveals similar transcriptional profiles including widespread gene suppression. Taken together, these data uncover a novel role of glycine in the deceleration of aging through its function in the methionine cycle.. CC-BY 4.0 International license It is made available under a (which was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.The copyright holder for this preprint . http://dx.doi.org/10.1101/393314 doi: bioRxiv preprint first posted online Aug. 16, 2018; 3 Author summaryThere are a growing number of studies showing that amino acids function as signal metabolites that influence aging and health. Although contemporary -OMICs studies have uncovered various associations between metabolite levels and aging, in many cases the directionality of the relationships is unclear. In a recent metabolomics study, we found that glycine accumulates in aged C. elegans while other amino acids decrease. The present study shows that glycine supplementation prolongs longevity and drives a genome-wide inhibition effect on C. elegans gene expression. Glycine as a one-carbon donor fuels the methyl pool of one-carbon metabolism composed of folates and methionine cycle. We find that glycinemediated longevity effect is fully dependent on methionine cycle, and that all of these observations are conserved with supplementation of the other one-carbon amino acid, serine.