Impaired metabolism–secretion coupling in pancreatic β-cells: Role of determinants of mitochondrial ATP production

Glucose-induced insulin secretion from β-cells is often impaired in diabetic condition and by exposure to diabetogenic pharmacological agents. In pancreatic β-cells, intracellular glucose metabolism regulates exocytosis of insulin granules, according to metabolism–secretion coupling in which glucose-induced mitochondrial ATP production plays an essential role. Impaired glucose-induced insulin secretion often results from impaired glucose-induced ATP elevation in β-cells. Mitochondrial ATP production is driven by the proton-motive force including mitochondrial membrane potential (ΔΨm) generated by the electron transport chain. These electrons are derived from reducing equivalents, generated in the Krebs cycle and transferred from cytosol by the shuttles. Here, roles of the determinants of mitochondrial ATP production in impaired glucose-induced insulin secretion are discussed.Cytosolic alkalization, H+ leak in the inner membrane by uncoupler (e.g. free fatty acid exposure), decrease in the supply of electron donors including NADH and FADH2 to the respiratory chain, and endogenous mitochondrial ROS (e.g. Na+/K+-ATPase inhibition) all reduce hyperpolarlization of ΔΨm and ATP production, causing decresed glucose-induced insulin release. The decrease in the supply of NADH and FADH2 to the respiratory chain derives from impairments in glucose metabolism including glycolysis (e.g. MODY2 and exposure to NO) and the shuttles (e.g. diabetic state and exposure to ketone body).