Adiponectin Increases Glucose-Dependent Electrical Activity and Insulin Secretion in Mouse Pancreatic ß Cells

Decreased plasma adiponectin has been implicated as a cause of diabetes. However, the functional impact of adiponectin on glucose-dependent responses of β-cells remains poorly understood. Here we have investigated whether chronically and acutely increased adiponectin levels affect electrical activity (sharp electrodes) and insulin secretion in β-cells using respectively, adiponectin overexpressing (APNtg) mice and acute application of adiponectin. In the acute exposure experiments, adiponectin (20 µg/ml, 11 mM glucose) increased insulin secretion 42% and β-cell electrical activity (measured as the fraction ‘active phase’) 32%. In islets from APNtg mice insulin secretion increased 44% and active phase increased 25%. The effects on electrical activity in APNtg β-cells correlated with membrane hyperpolarization and the resting membrane potential at 0 mM glucose averaged -60±2 in control and -69±2 in APNtg β-cells. There was a moderate effect on action potential width (<20%) and a more pronounced impact on action potential frequency by exogenous adiponectin (+35%) and in APNtg β-cells (+50%).These results suggest that both acutely and chronically increased adiponectin levels have a positive effect on electrical activity and insulin secretion of pancreatic β-cells.