Eto K, Suga S, Wakui M, Tsubamoto Y, Terauchi Y, Taka J, Aizawa S, Noda M, Kimura S, Kasai H, Kadowaki T
Department of Metabolic Diseases, Graduate School of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan.
J Biol Chem. 1999 Sep 3;274(36):25386-92. doi: 10.1074/jbc.274.36.25386.
The NADH shuttle system is composed of the glycerol phosphate and malate-aspartate shuttles. We generated mice that lack mitochondrial glycerol-3-phosphate dehydrogenase (mGPDH), a rate-limiting enzyme of the glycerol phosphate shuttle. Application of aminooxyacetate, an inhibitor of the malate-aspartate shuttle, to mGPDH-deficient islets demonstrated that the NADH shuttle system was essential for coupling glycolysis with activation of mitochondrial ATP generation to trigger glucose-induced insulin secretion. The present study revealed that blocking the NADH shuttle system severely suppressed closure of the ATP-sensitive potassium (K(ATP)) channel and depolarization of the plasma membrane in response to glucose in beta cells, although properties of the K(ATP) channel on the excised beta cell membrane were unaffected. In mGPDH-deficient islets treated with aminooxyacetate, Ca(2+) influx through the plasma membrane induced by a depolarizing concentration of KCl in the presence of the K(ATP) channel opener diazoxide restored insulin secretion. However, the level of the secretion was only approximately 40% of wild-type controls. Thus, glucose metabolism through the NADH shuttle system leading to efficient ATP generation is pivotal to activation of both the K(ATP) channel-dependent pathway and steps distal to an elevation of cytosolic Ca(2+) concentration in glucose-induced insulin secretion.
NADH穿梭系统由磷酸甘油穿梭和苹果酸-天冬氨酸穿梭组成。我们培育出了缺乏线粒体甘油-3-磷酸脱氢酶（mGPDH）的小鼠，mGPDH是磷酸甘油穿梭的限速酶。将苹果酸-天冬氨酸穿梭的抑制剂氨基氧乙酸应用于mGPDH缺陷型胰岛，结果表明NADH穿梭系统对于糖酵解与线粒体ATP生成激活相偶联以触发葡萄糖诱导的胰岛素分泌至关重要。本研究表明，尽管切除的β细胞膜上的ATP敏感性钾（K(ATP)）通道特性未受影响，但阻断NADH穿梭系统会严重抑制β细胞中ATP敏感性钾通道的关闭以及对葡萄糖刺激的质膜去极化。在用氨基氧乙酸处理的mGPDH缺陷型胰岛中，在存在K(ATP)通道开放剂二氮嗪的情况下，由去极化浓度的氯化钾诱导的通过质膜的Ca(2+)内流恢复了胰岛素分泌。然而，分泌水平仅约为野生型对照的40%。因此，通过NADH穿梭系统进行的葡萄糖代谢导致高效的ATP生成，对于激活K(ATP)通道依赖性途径以及葡萄糖诱导的胰岛素分泌中胞质Ca(2+)浓度升高后的远端步骤至关重要。
