Leptin promotes K-ATP channel trafficking by AMPK signaling in pancreatic beta-cells

Abstract

Leptin is a pivotal regulator of energy and glucose homeostasis, and defects in leptin signaling result in obesity and diabetes. The ATP-sensitive potassium (K-ATP) channels couple glucose metabolism to insulin secretion in pancreatic beta-cells. In this study, we provide evidence that leptin modulates pancreatic beta-cell functions by promoting K-ATP channel translocation to the plasma membrane via AMP-activated protein kinase (AMPK) signaling. K-ATP channels were localized mostly to intracellular compartments of pancreatic beta-cells in the fed state and translocated to the plasma membrane in the fasted state. This process was defective in leptin-deficient ob/ob mice, but restored by leptin treatment. We discovered that the molecular mechanism of leptin-induced AMPK activation involves canonical transient receptor potential 4 and calcium/calmodulin-dependent protein kinase kinase beta. AMPK activation was dependent on both leptin and glucose concentrations, so at optimal concentrations of leptin, AMPK was activated sufficiently to induce K-ATP channel trafficking and hyperpolarization of pancreatic beta-cells in a physiological range of fasting glucose levels. There was a close correlation between phospho-AMPK levels and beta-cell membrane potentials, suggesting that AMPK-dependent K-ATP channel trafficking is a key mechanism for regulating beta-cell membrane potentials. Our results present a signaling pathway whereby leptin regulates glucose homeostasis by modulating beta-cell excitability.