Methionine cycle in C. elegans serotonergic neurons regulates diet-dependent behaviour and longevity through neuron-gut signaling.

The folate and methionine cycles (Met-C) are regulated by vitamin B12 (B12), obtained exclusively from diet and microbiota. Met-C supports amino acid, nucleotide, and lipid biosynthesis and provides one-carbon moieties for methylation reactions. While B12 deficiency and polymorphisms in Met-C genes are clinically attributed to neurological and metabolic disorders, less is known about their cell-non-autonomous regulation of systemic physiological processes.