GLUCOSE/SECRETAGOGUE METABOLISM IN PANCREATIC ISLETS

这项研究的长期目标是获得有关胰岛素分泌代谢信号的新线索。这个项目的直接目的是了解线粒体氢穿梭及其在可代谢的促分泌剂诱导的胰岛β细胞胰岛素分泌中的作用。我们的大部分工作将集中在线粒体甘油磷酸脱氢酶(MGPD)，这是甘油磷酸穿梭的关键酶，以检验MGPD在细胞代谢脱氢酶(MGPD)中发挥重要作用的假设，MGPD是甘油磷酸穿梭的关键酶，以检验MGPD在包括胰岛素分泌在内的细胞代谢中发挥重要作用的假设。MGPD在正常的β细胞中含量丰富，但在糖尿病患者和啮齿动物模型中减少。虽然存在一种小鼠品系(BALB/CHEA)具有自然发生的胞浆甘油磷酸脱氢酶零章动(穿梭的胞液部分)，但没有突变或有效的抑制剂被描述为消除MGPD活性。第一个目的是使用最近生产的MGPD基因敲除小鼠和胞浆零动物来研究磷酸甘油穿梭及其组成酶在整个动物以及分离的胰岛和线粒体中的作用。第二个目标是继续对MGPD启动子的研究，以确定导致β细胞MGPD高表达和糖尿病中MGPD减少的因素。这个项目的第三个目的是验证这样的假设，即除了丙酮酸苹果酸穿梭外，胰岛β细胞中还有NADP(H)穿梭。最近的许多证据表明，在胰岛中存在丙酮酸-苹果酸穿梭。这种穿梭利用线粒体基质中的丙酮酸羧基酶作为维持穿梭单向性的酶，利用胞浆中的苹果酸酶作为NADP(H)氧化还原酶。有人认为，在β细胞中可能存在其他需要羧基酶的穿梭，但与其他胞质与胞质脱氢酶结合。由于MGPD和丙酮酸羧基酶的水平都不同，但与其他胞质脱氢酶结合。在非胰岛素依赖型糖尿病(NIDDM)的β细胞中，MGPD和丙酮酸羧基酶的水平是体内最高的，但在β细胞中却降低，因此研究它们的调节将有助于加深对NIDDM中燃料刺激的胰岛素分泌及其缺陷的认识。

The broad long term objective of this research is to obtain new clues about metabolic signals for insulin secretion. The immediate purpose of this project is to gain an understanding of mitochondrial hydrogen shuttles and their role in metabolizable secretagogue-induced insulin secretion in the pancreatic beta cell. Much of our effort will focus on the mitochondrial glycerol phosphate dehydrogenase (mGPD), the key enzyme in the glycerol phosphate shuttle, to test the hypothesis that mGPD plays an important role in cellular metabolism dehydrogenase (mGPD), the key enzyme in the glycerol phosphate shuttle, to test the hypothesis that mGPD plays an important role in cellular metabolism, including insulin secretion. mGPD is abundant in the normal beta cell, but is reduced in diabetics humans and in rodent models. While a mouse strain (BALB/cHeA) exists that possesses a naturally-occurring null nutation of the cytosolic glycerol phosphate dehydrogenase (the cytosolic half of the shuttle), no mutations or potent inhibitors have been described to eliminate mGPD activity. The first aim is to use a recently produced mGPD knockout mouse and the cytosolic null animal to study the role of the glycerol phosphate shuttle and its component enzymes in the whole animals and in isolated islets and mitochondria. The second aim is to continue studies of the mGPD promoter to determine factors responsible for high mGPD expression in the beta cell and its decrease in diabetes. The third aim of this project is to test the hypothesis that there are NADP(H) shuttles in the pancreatic beta cells besides the pyruvate malate shuttle. Much recent evidence suggests that the pyruvate malate shuttle is present in islets. This shuttle utilizes pyruvate carboxylase in the mitochondrial matrix as the enzyme that maintains unidirectionality of the shuttle, and malic enzyme in the cytosol as the NADP(H) oxidoreductase. It is proposed that other shuttles may exist in the beta cell that require the carboxylase, but in combination with other cytosolic with the cytosolic dehydrogenases. Since the levels of both mGPD and pyruvate carboxylase, but in combination with other cytosolic dehydrogenases. Since the levels of both mGPD and pyruvate carboxylase in the beta cell are among the highest in the body, but are decreased in the beta cell in non-insulin dependent diabetes (NIDDM), studies of their regulation will increase the understanding of fuel-stimulated insulin secretion and its defects in NIDDM.