Abstract

Objective— AMP-activated protein kinase (AMPK) and the ATP-sensitive K⁺ (K_ATP) channel are metabolic sensors that become activated during metabolic stress. AMPK is an important regulator of metabolism, whereas the K_ATP channel is a regulator of cellular excitability. Crosstalk between these systems is poorly understood.

Research design and methods— Rat pancreatic β-cells or INS-1 cells were pretreated for 2 h at various concentrations of glucose. Maximum K_ATP conductance (G_max) was monitored by whole-cell measurements following intracellular ATP washout using ATP-free internal solutions. K_ATP channel activity (NPo) was monitored by inside-out patch recordings in the presence of diazoxide. Distributions of K_ATP channel proteins (Kir6.2 and SUR1) were examined using immunofluorescence imaging and surface biotinylation studies. Insulin secretion from rat pancreatic islets was measured using an enzyme immunoassay.

Results— G_max and NPo in cells pretreated with glucose-free or 3 mM glucose solutions were significantly higher than those in cells pretreated in 11.1 mM glucose solutions. Immunofluorescence imaging and biotinylation studies revealed that glucose deprivation induced an increase in the surface level of Kir6.2 without affecting the total cellular amount. Increases in G_max and the surface level of Kir6.2 were inhibited by compound C, an AMPK inhibitor, and siAMPK transfection. The effects of glucose deprivation on K_ATP channels were mimicked by an AMPK activator. Glucose deprivation reduced insulin secretion, but this response was attenuated by compound C.

Conclusions— K_ATP channel trafficking is regulated by energy status via AMPK, and this mechanism may play a key role in inhibiting insulin secretion under low energy status.