Glucose/Secreatogogue Metabolism in Pancreatic islets

描述(由申请人提供)：广泛的长期目标是获得有关胰岛素分泌的代谢信号的新信息。这个项目的直接目的是更好地了解线粒体生物合成途径在胰岛素分泌中的作用。葡萄糖是最有效的胰岛素促分泌剂，所有其他燃料促分泌剂都通过线粒体的新陈代谢来刺激胰岛素的分泌。我们和其他人的工作涉及柠檬酸循环中间产物的生物合成(失调症)，以及它们从线粒体输出到胞浆(失调症)，以传递胰岛素分泌的信号。第一个目标是研究复苏的潜在产物，并将检验这样一个假设，即所有燃料胰岛素分泌物的代谢都共享涉及线粒体的最终共同途径，识别这些途径将产生关于耦合代谢和胞吐的线粒体因子的新线索。我们将跟进我们实验室最近的一项令人惊讶的发现，即柠檬酸盐在供应丙酮酸的β细胞线粒体和供应葡萄糖的完整β细胞中振荡，假设柠檬酸盐可以协调线粒体代谢和整体细胞代谢。研究计划确定除柠檬酸外的柠檬酸循环中间体在完整细胞中是否振荡，非葡萄糖促分泌剂是否引起柠檬酸循环中间体的振荡，了解线粒体如何同步产生柠檬酸振荡，并研究柠檬酸振荡的调节。目的2重点研究线粒体外产物的某些作用，以验证大多数柠檬酸循环中间产物在胰岛素分泌中具有信号作用的假说。在AIM中，小干扰RNA将被用来专门降低使用线粒体产品的某些酶的水平。由此导致的胰岛素释放的减少将与代谢途径的变化进行比较。在AIM 2B中，将对2型糖尿病患者的β细胞猝发进行有限的重点研究。

DESCRIPTION (provided by applicant): The broad long-term objective is to obtain new information about the metabolic signals for insulin secretion. The immediate purpose of this project is to gain a better understanding of the role of mitochondrial biosynthetic pathways in insulin secretion. Glucose, the most potent insulin secretagogue, and all other fuel secretagogues stimulate insulin secretion via their metabolism in mitochondria. Our work and that of others has implicated the biosynthesis (anaplerosis) of citric acid cycle intermediates and their export from mitochondria to the cytosol (cataplerosis) in signaling insulin secretion. Aim 1 is to study the potential products of anaplerosis and will test the hypothesis that the metabolism of all fuel insulin secretagogues shares final common pathways involving mitochondria and that discerning these pathways will yield new clues about mitochondrial factors that couple metabolism and exocytosis. We will follow up a recent surprising discovery from our laboratory that citrate oscillates in beta cell mitochondria supplied with pyruvate and in intact beta cells supplied with glucose, it is hypothesized that citrate can coordinate mitochondrial metabolism with overall cellular metabolism. Studies are planned to determine whether citric acid cycle intermediates besides citrate oscillate in intact ceils, whether non-glucose secretagogues cause oscillations in citric acid cycle intermediates, to learn how mitochondria become synchronized to produce citrate oscillations, and to investigate the regulation of citrate oscillations. Aim 2 will focus on certain extramitochondrial actions of mitochonddal products to test the hypothesis that most citric acid cycle intermediates have signaling roles in insulin secretion. In Aim 2A small interfering RNAs will be used to specifically lower levels of certain enzymes that use mitochondrial products. Resulting decreases in insulin release will be compared with alterations in metabolic pathways. In Aim 2B limited focused studies of beta ceil cataplerosis in type 2 diabetes will be performed.