Loss of Inverse Relationship Between Pulsatile Insulin and Glucagon Secretion in Patients With Type 2 Diabetes

OBJECTIVE: In patients with type 2 diabetes, glucagon levels are often increased. Furthermore, pulsatile secretion of insulin is disturbed in such patients. Whether pulsatile glucagon secretion is altered in type 2 diabetes is not known. RESEARCH DESIGN AND METHODS: Twelve patients with type 2 diabetes and 13 nondiabetic individuals were examined in the fasting state and after mixed meal ingestion. Deconvolution analyses were performed on insulin and glucagon concentration time series sampled at 1-min intervals. RESULTS: Both insulin and glucagon were secreted in distinct pulses, occurring at ∼5-min intervals. In patients with diabetes, postprandial insulin pulse mass was reduced by 74% (P < 0.001). Glucagon concentrations were increased in the patients during fasting and after meal ingestion (P < 0.05), specifically through an increased glucagon pulse mass (P < 0.01). In healthy subjects, the increase in postprandial insulin levels was inversely related to respective glucagon levels (P < 0.05). This relationship was absent in the fasting state and in patients with diabetes. CONCLUSIONS: Glucagon and insulin are secreted in a coordinated, pulsatile manner. A plausible model is that the postprandial increase in insulin burst mass represses the corresponding glucagon pulses. Disruption of the insulin–glucagon interaction in patients with type 2 diabetes could potentially contribute to hyperglucagonemia.