N-arachidonylglycine is a caloric state-dependent circulating metabolite which regulates human CD4+T cell responsiveness

Caloric deprivation interventions such as intermittent fasting and caloric restriction ameliorate metabolic and inflammatory disease. As a human model of caloric deprivation, a 24-h fast blunts innate and adaptive immune cell responsiveness relative to the refed state. Isolated serum at these time points confers these same immunomodulatory effects on transformed cell lines. To identify serum mediators orchestrating this, metabolomic and lipidomic analysis was performed on serum extracted after a 24-h fast and re-feeding. Bioinformatic integration with concurrent peripheral blood mononuclear cells RNA-seq analysis implicated key metabolite-sensing GPCRs in fasting-mediated immunomodulation. The putative GPR18 ligand N-arachidonylglycine (NAGly) was elevated during fasting and attenuated CD4(+)T cell responsiveness via GPR18 MTORC1 signaling. In parallel, NAGly reduced inflammatory Th1 and Th17 cytokines levels in CD4(+)T cells isolated from obese subjects, identifying a fasting-responsive metabolic intermediate that may contribute to the regulation of nutrient-level dependent inflammation associated with metabolic disease.

Automated summary

Caloric deprivation interventions such as intermittent fasting and caloric restriction have positive effects on metabolic and inflammatory diseases. When subjected to a 24-hour fast, both innate and adaptive immune cell responsiveness is reduced, and this effect can be transferred through serum. Metabolomic and lipidomic analysis of serum extracted after a 24-hour fast and re-feeding revealed metabolite-sensing GPCRs as crucial mediators of fasting-mediated immune modulation. The elevated levels of N-arachidonylglycine (NAGly), a putative GPR18 ligand, during fasting attenuate CD4(+)T cell responsiveness and reduce inflammatory cytokines levels in obese subjects, suggesting its role in regulating nutrient-level dependent inflammation associated with metabolic disease.