Search

Sirtuins are nicotinamide adenine dinucleotide (NAD + )-dependent protein lysine deacylases regulating metabolism and stress responses; however, characterization of the removed acyl groups and their downstream metabolic fates remains incomplete. Here we employed untargeted comparative metabolomics to reinvestigate mitochondrial sirtuin biochemistry. First, we identified N-glutarylspermidines as metabolites downstream of the mitochondrial sirtuin SIR-2.3 in Caenorhabditis elegans and demonstrated that SIR-2.3 functions as a lysine deglutarylase and that N-glutarylspermidines can be derived from O-glutaryl-ADP-ribose. Subsequent targeted analysis of C. elegans, mouse and human metabolomes revealed a chemically diverse range of N-acylspermidines, and formation of N-succinylspermidines and/or N-glutarylspermidines was observed downstream of mammalian mitochondrial sirtuin SIRT5 in two cell lines, consistent with annotated functions of SIRT5. Finally, N-glutarylspermidines were found to adversely affect C. elegans lifespan and mammalian cell proliferation. Our results indicate that N-acylspermidines are conserved metabolites downstream of mitochondrial sirtuins that facilitate annotation of sirtuin enzymatic activities in vivo and may contribute to sirtuin-dependent phenotypes., (© 2024. The Author(s), under exclusive licence to Springer Nature America, Inc.)

Recent studies of animal metabolism have revealed large numbers of novel metabolites that are involved in all aspects of organismal biology, but it is unclear to what extent metabolomes differ between sexes. Here, using untargeted comparative metabolomics for the analysis of wildtype animals and sex determination mutants, we show that C. elegans hermaphrodites and males exhibit pervasive metabolomic differences. Several hundred small molecules are produced exclusively or in much larger amounts in one sex, including a host of previously unreported metabolites that incorporate building blocks from nucleoside, carbohydrate, lipid, and amino acid metabolism. A subset of male-enriched metabolites is specifically associated with the presence of a male germline, whereas enrichment of other compounds requires a male soma. Further, we show that one of the male germline-dependent metabolites, an unusual dipeptide incorporating N,N-dimethyltryptophan, increases food consumption, reduces lifespan, and accelerates the last stage of larval development in hermaphrodites. Our results serve as a foundation for mechanistic studies of how the genetic sex of soma and germline shape the C. elegans metabolome and provide a blueprint for the discovery of sex-dependent metabolites in other animals., (© 2023. The Author(s).)

The recently discovered mo dular gl ucosides (MOGLs) form a large metabolite library derived from combinatorial assembly of moieties from amino acid, neurotransmitter, and lipid metabolism in the model organism C. elegans . Combining CRISPR-Cas9 genome editing, comparative metabolomics, and synthesis, we show that the carboxylesterase homologue Cel-CEST-1.2 is responsible for specific 2- O -acylation of diverse glucose scaffolds with a wide variety of building blocks, resulting in more than 150 different MOGLs. We further show that this biosynthetic role is conserved for the closest homologue of Cel-CEST-1.2 in the related nematode species C. briggsae , Cbr-CEST-2. Expression of Cel-cest-1.2 and MOGL biosynthesis are strongly induced by starvation conditions in C. elegans , one of the premier model systems for mechanisms connecting nutrition and physiology. Cel-cest-1.2 -deletion results in early death of adult animals under starvation conditions, providing first insights into the biological functions of MOGLs.

Excreted small-molecule signals can bias developmental trajectories and physiology in diverse animal species. However, the chemical identity of these signals remains largely obscure. Here we report identification of an unusual N-acylated glutamine derivative, nacq#1, that accelerates reproductive development and shortens lifespan in Caenorhabditis elegans. Produced predominantly by C. elegans males, nacq#1 hastens onset of sexual maturity in hermaphrodites by promoting exit from the larval dauer diapause and by accelerating late larval development. Even at picomolar concentrations, nacq#1 shortens hermaphrodite lifespan, suggesting a trade-off between reproductive investment and longevity. Acceleration of development by nacq#1 requires chemosensation and is dependent on three homologs of vertebrate steroid hormone receptors. Unlike ascaroside pheromones, which are restricted to nematodes, fatty acylated amino acid derivatives similar to nacq#1 have been reported from humans and invertebrates, suggesting that related compounds may serve signaling functions throughout metazoa.

Environmental conditions experienced during animal development are thought to have sustained impact on maturation and adult lifespan. Here we show that in the model organism C. elegans developmental rate and adult lifespan depend on larval population density, and that this effect is mediated by excreted small molecules. By using the time point of first egg laying as a marker for full maturity, we found that wildtype hermaphrodites raised under high density conditions developed significantly faster than animals raised in isolation. Population density-dependent acceleration of development (Pdda) was dramatically enhanced in fatty acid β-oxidation mutants that are defective in the biosynthesis of ascarosides, small-molecule signals that induce developmental diapause. In contrast, Pdda is abolished by synthetic ascarosides and steroidal ligands of the nuclear hormone receptor DAF-12. We show that neither ascarosides nor any known steroid hormones are required for Pdda and that another chemical signal mediates this phenotype, in part via the nuclear hormone receptor NHR-8. Our results demonstrate that C. elegans development is regulated by a push-pull mechanism, based on two antagonistic chemical signals: chemosensation of ascarosides slows down development, whereas population-density dependent accumulation of a different chemical signal accelerates development. We further show that the effects of high larval population density persist through adulthood, as C. elegans larvae raised at high densities exhibit significantly reduced adult lifespan and respond differently to exogenous chemical signals compared to larvae raised at low densities, independent of density during adulthood. Our results demonstrate how inter-organismal signaling during development regulates reproductive maturation and longevity.

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

Over the past 10 years, the relevance of small-molecule signaling for many aspects of C. elegans development and behavior has become apparent. One prominent group of small-molecule signals are the ascarosides, which control dauer entry and exit as well as a variety of sex-specific and social behaviors, including male attraction, hermaphrodite repulsion, olfactory plasticity, and aggregation. This wide range of biological functions is facilitated by a great diversity of ascaroside chemical structures. These are based on the sugar ascarylose, which is linked to fatty acid-like side chains of varying lengths and often decorated further with building blocks derived from amino acids, folate, and other primary metabolites. Different ascarosides or combinations of ascarosides mediate different phenotypes, and even small differences in chemical structures are often associated with strongly altered activity profiles. Additional complexity arises from concentration-dependent effects and synergism between different ascarosides. The ascarosides are sensed by several types of chemosensory head neurons, including the ASK, ASI, and ADL neurons as well as the male-specific CEM neurons. Ascaroside perception is mediated by diverse families of G-protein coupled membrane receptors that act upstream of conserved signal transduction pathways, including insulin/IGF-1 signaling and transforming growth factor beta (TGF-β) signaling. Biosynthesis of the ascarosides appears to integrate input from several primary metabolic pathways, including peroxisomal β-oxidation of long-chain fatty acids and amino acid catabolism. Life stage, sex, as well as food availability and other environmental factors affect ascaroside biosynthesis, suggesting that ascaroside signaling communicates detailed information about life history and metabolic state.

Environmental cues transduced by an endocrine network converge on Caenorhabditis elegans nuclear receptor DAF-12 to mediate arrest at dauer diapause or continuous larval development. In adults, DAF-12 selects long-lived or short-lived modes. How these organismal choices are molecularly specified is unknown. Here we show that coregulator DIN-1 and DAF-12 physically and genetically interact to instruct organismal fates. Homologous to human corepressor SHARP, DIN-1 comes in long (L) and short (S) isoforms, which are nuclear localized but have distinct functions. DIN-1L has embryonic and larval developmental roles. DIN-1S, along with DAF-12, regulates lipid metabolism, larval stage-specific programs, diapause, and longevity. Epistasis experiments reveal that din-1S acts in the dauer pathways downstream of lipophilic hormone, insulin/IGF, and TGFbeta signaling, the same point as daf-12. We propose that the DIN-1S/DAF-12 complex serves as a molecular switch that implements slow life history alternatives in response to diminished hormonal signals.