Gut microbiota-derived metabolites as key mucosal barrier modulators in obesity

Figure 2 The roles of the indicated amino acid metabolites in mucosal homeostasis and metabolic health. Tryptophan and tyrosine metabolites can engage various molecular targets in the gut, and play positive roles in maintaining mucosal barrier integrity and regulating systemic metabolic health at least in part by modulating mucosal immune and epithelial cell functions via cytokine IL-22 or type I interferon, etc., or by promoting host energy metabolism via trace amine-associated receptor 1. The question mark indicates that the molecular target of desaminotyrosine is currently unknown. 5-HT4R: Serotonin receptor-4; AhR: Aryl hydrocarbon receptor; DAT: Desaminotyrosine; PXR: Pregnane X receptor; TAAR1: Trace amine-associated receptor 1; TRPA1: Transient receptor potential ankyrin A1.