BACKGROUND: Postprandial secretion of glucagon-like peptide 1 (GLP-1) has been found diminished in some patients with type 2 diabetes mellitus (T2DM) and high glucagon concentrations. We examined the effects of exogenous glucagon on the release of incretin hormones. PATIENTS AND METHODS: Ten patients with T2DM and 10 healthy controls were examined with a meal test during the iv administration of glucagon 0.65 ng/kg.min and placebo. RESULTS:GLP-1 plasma concentration increased after meal ingestion in both groups (P<0.0001), but postprandial GLP-1 plasma levels were not affected by glucagon administration. However, immediately after cessation of the glucagon infusion, GLP-1 levels increased by about 2-fold to levels of 51.8+/-14.6 pmol/liter in the T2DM patients and 58.9+/-20.0 pmol/liter in controls (P<0.05). The time courses of glucose-dependent insulinotropic peptide glucose-dependent insulinotropic peptide and GLP-1 concentrations were not different between T2DM patients and controls during the placebo experiments (P=0.33 and P=0.13, respectively). Glucose concentrations were increased by glucagon administration in controls (P<0.05, respectively), but insulin and C-peptide levels were not affected. Gastric emptying was slightly delayed by glucagon administration in controls (P<0.05) but not in T2DM patients (P=0.77). CONCLUSIONS:Exogenous glucagon does not directly inhibit incretin secretion. However, a decline in circulating glucagon levels may exert a permissive effect on GLP-1 release. This might contribute to the reduction in GLP-1 concentrations found in some patients with T2DM.
RCT Entities:
BACKGROUND: Postprandial secretion of glucagon-like peptide 1 (GLP-1) has been found diminished in some patients with type 2 diabetes mellitus (T2DM) and high glucagon concentrations. We examined the effects of exogenous glucagon on the release of incretin hormones. PATIENTS AND METHODS: Ten patients with T2DM and 10 healthy controls were examined with a meal test during the iv administration of glucagon 0.65 ng/kg.min and placebo. RESULTS:GLP-1 plasma concentration increased after meal ingestion in both groups (P<0.0001), but postprandial GLP-1 plasma levels were not affected by glucagon administration. However, immediately after cessation of the glucagon infusion, GLP-1 levels increased by about 2-fold to levels of 51.8+/-14.6 pmol/liter in the T2DM patients and 58.9+/-20.0 pmol/liter in controls (P<0.05). The time courses of glucose-dependent insulinotropic peptide glucose-dependent insulinotropic peptide and GLP-1 concentrations were not different between T2DM patients and controls during the placebo experiments (P=0.33 and P=0.13, respectively). Glucose concentrations were increased by glucagon administration in controls (P<0.05, respectively), but insulin and C-peptide levels were not affected. Gastric emptying was slightly delayed by glucagon administration in controls (P<0.05) but not in T2DM patients (P=0.77). CONCLUSIONS: Exogenous glucagon does not directly inhibit incretin secretion. However, a decline in circulating glucagon levels may exert a permissive effect on GLP-1 release. This might contribute to the reduction in GLP-1 concentrations found in some patients with T2DM.