Regulation of the one carbon folate cycle as a shared metabolic signature of longevity.

The metabolome represents a complex network of biological events that reflects the physiologic state of the organism in health and disease. Additionally, specific metabolites and metabolic signaling pathways have been shown to modulate animal ageing, but whether there are convergent mechanisms uniting these processes remains elusive. Here, we used high resolution mass spectrometry to obtain the metabolomic profiles of canonical longevity pathways in C. elegans to identify metabolites regulating life span. By leveraging the metabolomic profiles across pathways, we found that one carbon metabolism and the folate cycle are pervasively regulated in common. We observed similar changes in long-lived mouse models of reduced insulin/IGF signaling. Genetic manipulation of pathway enzymes and supplementation with one carbon metabolites in C. elegans reveal that regulation of the folate cycle represents a shared causal mechanism of longevity and proteoprotection. Such interventions impact the methionine cycle, and reveal methionine restriction as an underlying mechanism. This comparative approach reveals key metabolic nodes to enhance healthy ageing.

Caenorhabditis elegans processes sensory information to choose between freeloading and self-defense strategies.

Hydrogen peroxide is the preeminent chemical weapon that organisms use for combat. Individual cells rely on conserved defenses to prevent and repair peroxide-induced damage, but whether similar defenses might be coordinated across cells in animals remains poorly understood. Here, we identify a neuronal circuit in the nematode Caenorhabditis elegans that processes information perceived by two sensory neurons to control the induction of hydrogen peroxide defenses in the organism. We found that catalases produced by Escherichia coli, the nematode's food source, can deplete hydrogen peroxide from the local environment and thereby protect the nematodes. In the presence of E. coli, the nematode's neurons signal via TGFß-insulin/IGF1 relay to target tissues to repress expression of catalases and other hydrogen peroxide defenses. This adaptive strategy is the first example of a multicellular organism modulating its defenses when it expects to freeload from the protection provided by molecularly orthologous defenses from another species.

Cells of all kinds often wage chemical warfare against each other. Hydrogen peroxide is often the weapon of choice on the microscopic battlefield, where it is used to incapacitate opponents or to defend against attackers. For example, some plants produce hydrogen peroxide in response to infection to fight off disease-causing microbes. Individual cells have also evolved defenses to prevent or repair 'injuries' caused by hydrogen peroxide. These are similar across many different species. They include enzymes called catalases, which break down hydrogen peroxide, and others to repair damage. However, scientists still do not fully understand how animals and other multicellular organisms might coordinate these defenses across their cells. Caenorhabditis elegans is a microscopic species of worm that lives in rotting fruits. It often encounters the threat of cellular warfare: many types of bacteria in its environment generate hydrogen peroxide, and some can make enough to kill the worms outright. Like other organisms, C. elegans also produces catalases to defend itself against hydrogen peroxide attacks. However, it must activate its defenses at the right time; if it did so when they were not needed, this would result in a detrimental energy 'cost' to the worm. Although C. elegans is a small organism containing only a defined number of cells, exactly why and how it switches its chemical defenses on or off remains unknown. Schiffer et al. therefore set out to determine how C. elegans controls these defenses, focusing on the role of the brain in detecting and processing information from its environment. Experiments looking at the brains of genetically manipulated worms revealed a circuit of sensory nerve cells whose job is to tell the rest of the worm's tissues that they no longer need to produce defense enzymes. Crucially, the circuit became active when the worms sensed E. coli bacteria nearby. Bacteria in the same family as E. coli are normally found in in the same habitat as C. elegans and these bacteria are also known to make enzymes of their own to eliminate hydrogen peroxide around them. These results indicate that C. elegans can effectively decide, based on the activity of its circuit, when to use its own defenses and when to 'freeload' off those of neighboring bacteria. This work is an important step towards understanding how sensory circuits in the brain can control hydrogen peroxide defenses in multicellular organisms. In the future, it could help researchers work out how more complex animals, like humans, coordinate their cellular defenses, and therefore potentially yield new strategies for improving health and longevity.

Comparison of ESI-MS/MS and APCI-MS methods for the quantification of folic acid analogs in C. elegans.

Folic acid (FA) plays a vital role in central metabolism, including the one carbon cycle, nucleotide, and amino acid biosynthesis. The development of sensitive, accurate analytical methods to measure FA intermediates in tissues is critical to understand their biological roles in diverse physiological and pathological contexts. Here, we developed a highly sensitive method for the simultaneous quantification of FA intermediates in the nematode Caenorhabditis elegans as a model to dissect metabolic networks. The method was further validated by analyzing the worm folate pool upon RNAi knockdown of the dihydrofolate reductase gene dhfr-1. Comparative mass spectrometry behavior of the FA analogs using two different ion sources, electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI), revealed ESI-MS/MS to be more sensitive, but APCI-MS provided more detailed structure inferences, which can elucidate chemical investigation and synthesis of FA analogs. Finally, we report on the use of in vitro oxidation coupled with high-resolution mass spectrometry as a tool to discover new endogenous FA derivatives in the nematode.