Contribution of endogenous glucagon-like peptide-1 to changes in glucose metabolism and islet function in people with type 2 diabetes four weeks after Roux-en-Y gastric bypass (RYGB).

Abstract

Glucagon-Like Peptide-1 (GLP-1) is an insulin secretagogue which is elevated after Roux-en-Y Gastric Bypass (RYGB). However, its contribution to glucose metabolism after RYGB remains uncertain.\n\n\nAIMS\nWe tested the hypothesis that GLP-1 lowers postprandial glucose concentrations and improves β-cell function after RYGB.\n\n\nMATERIALS AND METHODS\nTo address these questions we used a labeled mixed meal to assess glucose metabolism and islet function in 12 obese subjects with type 2 diabetes studied before and four weeks after RYGB. During the post-RYGB study subjects were randomly assigned to receive an infusion of either saline or Exendin-9,39 a competitive antagonist of GLP-1 at its receptor. Exendin-9,39 was infused at 300\u202fpmol/kg/min for 6\u202fh. All subjects underwent RYGB for medically-complicated obesity.\n\n\nRESULTS\nExendin-9,39 resulted in increased integrated incremental postprandial glucose concentrations (181\u202f±\u202f154 vs. 582\u202f±\u202f129\u202fmmol per 6\u202fh, p\u202f=\u202f0.02). In contrast, this was unchanged in the presence of saline (275\u202f±\u202f88 vs. 315\u202f±\u202f66\u202fmmol per 6\u202fh, p\u202f=\u202f0.56) after RYGB. Exendin-9,39 also impaired β-cell responsivity to glucose but did not alter Disposition Index (DI).\n\n\nCONCLUSIONS\nThese data indicate that the elevated GLP-1 concentrations that occur early after RYGB improve postprandial glucose tolerance by enhancing postprandial insulin secretion.