Tumor Necrosis Factor α Decreases Glucagon-Like Peptide-2 Expression by Up-Regulating G-Protein-Coupled Receptor 120 in Crohn Disease

Glucagon-like peptide (GLP)-2, secreted by L cells in the small intestine, has anti-inflammatory effects in the gastrointestinal tract. A GLP-2 analogue has been an effective treatment for Crohn disease (CD). G-protein coupled receptor (GPR) 40 and GPR120 are probably involved in GLP-2 production, the mechanisms of which remain unclear. In our experiments, normal ilea mucosa expressed GPR40, but rarely expressed GPR120. However, both GPRs were overexpressed in the L cells of the inflamed ileal mucosa of CD patients. MucosaL inflammation induced the overexpression of GPR40, GPR120, and several inflammatory cytokines, with correlations between ilea concentrations of tumor necrosis factor (TNF)-alpha and GPR expression levels; however, inflammation did not induce the expression of proglucagon, a precursor of GLP-2 in CD patients. In rat L cells and GLUTag cells, TNF-alpha treatment increased GPR120 mRNA expression without affecting GPR40 mRNA expression. Dual agonists of GPR40 and GPR120, GW9508 and linoleic acid, respectively, increased GLP-2 production from L cells, but these agonists decreased it in the presence of TNF-alpha. The GPR40 antagonist, GW1100, inhibited the GW9508-induced increase in GLP-2 production, and silencing GPR120 resulted in further elevation of GLP-2 production. Thus, GPR120-dependent signaling inhibited the stimulatory effects of GPR40 on GLP-2 expression, and TNF-alpha treatment decreased GLP-2 expression by up-regulating GPR120 expression in L cells.