Bile acids promote glucagon-like peptide-1 secretion through TGR5 in a murine enteroendocrine cell line STC-1

Abstract

Bile acids play essential roles in the absorption of dietary lipids and in the regulation of bile acid biosynthesis. Recently, a G protein-coupled receptor, TGR5, was identified as a cell-surface bile acid receptor. In this study, we show that bile acids promote glucagon-like peptide-1 (GLP-1) secretion through TGR5 in a murine enteroendocrine cell line STC-1. In STC-1 cells, bile acids promoted GLP-1 secretion in a dose-dependent manner. As STC-1 cells express TGR5 mRNA, we examined whether bile acids induce GLP-1 secretion through TGR5. RNA interference experiments showed that reduced expression of TGR5 resulted in reduced secretion of GLP-1. Furthermore, transient transfection of STC-1 cells with an expression plasmid containing TGR5 significantly enhanced GLP-1 secretion, indicating that bile acids promote GLP-1 secretion through TGR5 in STC-1 cells. Bile acids induced rapid and dose-dependent elevation of intracellular cAMP levels in STC-1 cells. An adenylate cyclase inhibitor, MDL12330A, significantly suppressed bile acid-promoted GLP-1 secretion, suggesting that bile acids induce GLP-1 secretion via intracellular cAMP production in STC-1 cells.