Endosomal free fatty acid receptor 2 signaling is essential for propionate-induced anorectic gut hormone release

The ability of propionate, a short chain fatty acid produced from the fermentation of non-digestible carbohydrates in the colon, to stimulate the release of anorectic gut hormones, such as glucagon like peptide-1 (GLP-1), is an attractive approach to enhance appetite regulation, weight management and glycaemic control. Propionate induces GLP-1 release via its G protein-coupled receptor (GPCR), free fatty acid receptor 2 (FFA2); a GPCR that activates Gαi and Gαq/11 pathways. However, how pleiotropic GPCR signaling mechanisms in the gut regulates appetite is poorly understood. Here, we identify propionate-mediated G protein signaling is spatially directed within the cell via the targeting of FFA2 to very early endosomes. Furthermore, propionate activates an endosomal Gαi/p38 signaling pathway, which is essential for propionate-induced GLP-1 release in enteroendocrine cells and colonic crypts. Our study reveals that intestinal metabolites can engage membrane trafficking pathways and endosomal signaling platforms to orchestrate complex GPCR pathways within the gut.