Hepatic Insulin Action: Role of the Pentose Cycle

肝胰岛素作用：戊糖循环的作用

• 批准号: 6708920
• 负责人: Irwin Jack Kurland
• 金额: $ 28.07万
• 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 2004-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6708920
• 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：戊糖循环的作用。胰岛素刺激 PI3 激酶导致磷脂酰肌醇 - 3,4,5 三磷酸 (PIP3) 形成增加，这对葡萄糖 - 6 - 磷酸酶 (G6Pase) 活性具有直接抑制作用，并启动信号传导效应链，通过 Akt 激活和 GSK-3 抑制，刺激糖酵解、糖原储存和磷酸戊糖途径 (PPP) 通量，并抑制糖异生。 磷酸己糖池和磷酸丙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。 磷酸己糖库和磷酸丙糖库通过磷酸戊糖途径 (PPP) 的氧化和非氧化分支保持平衡。 我们的 13C 质量同位素异构体分布分析 (MIDA) 通量实验表明，胰岛素对 PI3-K 的刺激通过 PI3-K 对 G6Pase 的抑制来协调糖酵解/糖异生途径和磷酸戊糖途径 (PPP) 之间的通量。 胰岛素可以上调通过 PPP 非氧化区的通量，或通过 6-磷酸葡萄糖脱氢酶 (G6PDH) 上调氧化区的通量，从而提高 5-磷酸木酮糖 (X5P) 水平，从而刺激糖酵解。 G6PDH 也是 NADPH 的主要来源，它使细胞质保持还原状态。研究表明，当肝细胞质氧化程度更高时，HGP 就会增加。 假设：胰岛素刺激的PI3-K刺激PPP通量，PPP通量的刺激增强胰岛素作用的功能。假设检验的具体目标： 定量 PI3-K 及其信号效应器/调节器 Akt、MMAC、磷脂酰肌醇 3- 磷酸酶和 GSK-3 对磷酸己糖和磷酸丙糖池之间流量的作用和作用，通过腺病毒介导的过度表达，以及选定的 PI3-K 信号传导抑制剂。 特定的 13C 标记底物将用于通过原代大鼠肝细胞培养物中的质量同位素分析来确定进出 G-6-P 池的通量。 这些研究可能会确定肝脏胰岛素作用发生缺陷的区域，以及可以指导基于肝脏的基因治疗的区域。