β-Endorphin infusion restores acute insulin responses to glucose in type-2 diabetes mellitus

To address the possibility that an abnormality in pancreatic β-endorphin activity might contribute to abnormal insulin secretion in diabetes mellitus, we studied the effects of β-endorphin infusion on islet function in diabetic patients. The iv infusion of human β-endorphin at a dose of 0.5 mg/h for 2 h in type-2 non-insulin-dependent diabetic patients (n = 12) raised plasma insulin and glucagon levels and slightly but significantly lowered plasma glucose concentrations. β-Endorphin infusion also resulted in reappearance of a clear-cut acute insulin response to glucose, while second phase insulin release was increased and glucose disposal accelerated. Acute insulin and glucagon responses to arginine were not increased by β-endorphin, suggesting that the effect of the opioid on the B cells of the diabetic patients is specific for glucose. An intraislet abnormality of opioid peptides action and/or secretion may play a role in the disturbances of insulin secretion in patients with type-2 diabetes mellitus.