Hepatic Insulin Action: Role of the Pentose Cycle

肝胰岛素作用：戊糖循环的作用

• 批准号: 6435151
• 负责人: Irwin Jack Kurland
• 金额: $ 33.55万
• 依托单位: UNIVERSITY OF CALIFORNIA LOS ANGELES
• 依托单位国家: 美国
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-03-15 至 2007-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6435151
• 关键词: Adenoviridae; NAD(H) phosphate; biological signal transduction; enzyme activity; enzyme inhibitors; gluconeogenesis; glucose 6 phosphatase; glucose 6 phosphate dehydrogenase; glycogenesis; glycogenolysis; glycolysis; hormone regulation /control mechanism; insulin; insulin sensitivity /resistance; laboratory rat; liver cells; liver metabolism; pentose phosphate; pentoses; phosphatidylinositol 3 kinase; polymerase chain reaction; sirolimus; tissue /cell culture; transfection /expression vector

Hepatic insulin action: Role of the pentose cycle. Insulin stimulation of PI3-Kinase results in an increase in phosphatidylinositol-3,4,5 tri-phosphate (PIP3) formation, which has direct inhibitory effects on glucose-6-phosphatase (G6Pase) activity, as well as initiating the activation of a signaling effector chain, via Akt activation and GSK-3 inhibition, that stimulates glycolysis, glycogen storage, and pentose phosphate pathway (PPP) flux, and inhibits gluconeogenesis. The control of substrate flux between the hexose phosphate pool and the triose phosphate pool has been recognized as the key mechanism for insulin's regulation of HGP. The hexose phosphate pool and the triose phosphate pool are in equilibrium through the oxidative and non-oxidative branches of the pentose phosphate pathway (PPP). Our 13C mass isotopomer distribution analysis (MIDA) flux experiments indicate that insulin's stimulation of PI3-K coordinates flux between the glycolytic/gluconeogenic pathways and the pentose phosphate pathway (PPP) via PI3-K's inhibition of G6Pase. Insulin can upregulate flux through the non-oxidative limb of the PPP, or the oxidative limb via glucose-6-phosphate dehydrogenase (G6PDH), raising xylulose-5-phosphate (X5P) levels, which can stimulate glycolysis. G6PDH is also the principal source of NADPH, which keeps the cytoplasm in a reduced state. Studies suggest that when the liver cytoplasm is more oxidized, HGP is increased. Hypothesis: Insulin-stimulated PI3-K stimulates PPP flux, and the stimulation of PPP flux enhances the function of insulin action. Specific aims for hypothesis testing: To quantitate the roles, and actions on the flux between the hexose phosphate and the triose phosphate pools, of PI3-K and its signaling effectors/modulators Akt, MMAC, a phosphatidylinositol 3- phosphatase, and GSK-3, via adenoviral mediated overexpression, and selected inhibitors of PI3-K signaling. Specific 13C labeled substrates will be used to determine flux passing to and from the G-6-P pool using mass isotopomer analysis in primary rat hepatocyte culture. These studies may identify areas where defects in hepatic insulin action occur, and where hepatic-based gene therapies can be directed.

肝胰岛素作用：戊糖周期的作用。 PI3-激酶刺激PI3-激酶会导致磷脂酰肌醇-3,4,5三磷酸（PIP3）形成，对葡萄糖6-磷酸酶（G6Pase）活性具有直接抑制作用储存和戊糖磷酸途径（PPP）通量，并抑制糖异生。 磷酸己糖池和磷酸三糖池之间底物通量的控制已被认为是胰岛素调节HGP的关键机制。 磷酸己糖和三糖磷酸盐池通过戊糖磷酸途径（PPP）的氧化和非氧化分支处于平衡状态。 我们的13C质量同位素分布分析（MIDA）通量实验表明，胰岛素刺激PI3-K在糖酵解/糖素异生途径和五肽磷酸途径（PPP）之间通过PI3-K通过PI3-K的G6Pase抑制作用之间的通量。 胰岛素可以通过PPP的非氧化肢或通过葡萄糖-6-磷酸脱氢酶（G6PDH）上调通量，从而提高了木糖糖 - 5-磷酸（X5P）水平，从而可以刺激糖酵解。 G6PDH也是NADPH的主要来源，它使细胞质保持在降低的状态。研究表明，当肝脏细胞质被更多地氧化时，HGP会增加。 假设：胰岛素刺激的PI3-K刺激PPP通量，PPP通量的刺激增强了胰岛素作用的功能。假设检验的具体目的：量化PI3-K及其信号效应子/调节剂AKT，MMAC，MMAC，一种磷脂酰肌醇3-磷酸蛋白酶3-磷酸酶和GSK-3的磷酸二磷酸和三糖磷酸盐池之间的磁通的作用。 特异性13C标记的底物将使用原代大鼠肝细胞培养中的质量同位素分析来确定传递G-6-P池的通量。 这些研究可能会确定发生肝胰岛素作用缺陷的领域，以及可以指示基于肝的基因疗法的领域。