Aging, Calorie Restriction and Insulin Signaling

描述：(逐字摘自申请表)到60-74岁，大约1/3 的美国人患有异常的糖耐量。骨骼肌胰岛素 抵抗力是与年龄相关的2型进展过程中的一个重要缺陷 糖尿病。卡路里限制(CR；消耗约60%的广告 锂，AL，摄入量)改善胰岛素敏感性。广泛的、长期的 目的是阐明CR诱导的改善的机制。 胰岛素的作用。这个项目的重点是调节葡萄糖的细胞过程。 骨骼肌的转运(葡萄糖代谢的限速步骤)。 具体目标1是确定CR-增强的机制 酪氨酸磷酸化IRS-1与胰岛素刺激下的胰岛素受体 肌肉。使IRS-1去磷酸化的蛋白酪氨酸磷酸酶和 将对胰岛素受体进行研究，因为CR不会增加胰岛素受体 使IRS-1和受体磷酸化的酪氨酸激酶。具体目标2是 确定CR是否增强胰岛素介导的磷脂酰肌醇(PI)3-激酶 功能。这种酶对葡萄糖转运的CR效应是必不可少的，尽管 铬不改变用常规方法测定的PI3-激酶活性 国税局-L-免疫沉淀样品。胰岛素刺激的CR和AL大鼠肌肉 将比较：a)p50pha调节剂的丰度和IRS结合 PI 3-激酶的亚基(据报道，这种异构体可以引起更大的PI 在完整细胞中产生的3，4，5-三磷酸高于p85α，但在 IRS-L-免疫沉淀样品)；b)PI 3-激酶脂质产物(PI 3，4，5-三磷酸)水平由完整的胰岛素刺激肌肉形成 (因为CR效应可能需要完整细胞的内部环境)；以及 蛋白激酶B的激活(胰岛素信号转导步骤位于并依赖于远端 PI3-激酶)。具体目标3是确定CR对0-连锁的影响 N-乙酰氨基葡萄糖(G1cNAc)-蛋白质的修饰。肌酸降低肌肉水平 UDP-N-乙酰氨基己糖(0-GlcNAc转移酶底物)。胰岛素 抗性与0-GIcNAc修饰蛋白的升高有关(例如， IRS-1)，因此CR降低0-GlcNAc-蛋白水平可能对 增强胰岛素的作用。胰岛素增强型机制的阐明 CR的敏感性对改善健康和质量具有重要意义 老年人的生活。这项研究还将提供基本的见解 探讨CR的多效性：酪氨酸磷酸酶和PI3-激酶发挥关键作用 在几个信号通路中的作用，以及改变的0-G1cNAc-修饰 蛋白质可能介导CR诱导的多个结果。

DESCRIPTION: (Verbatim from application) By age 60-74 years, approximately 1/3 of Americans suffer from abnormal glucose tolerance. Skeletal muscle insulin resistance is an essential defect in age-related progression to type 2 diabetes. Calorie restriction (CR; consuming approximately 60 percent of ad libitum, AL, intake) improves insulin sensitivity. The broad, long-term objective is to elucidate mechanisms underlying CR-induced improvement in insulin action. This project focuses on cellular processes regulating glucose transport (rate-limiting step for glucose metabolism) in skeletal muscle. Specific Aim 1 is to identify the mechanism for CR-enhancement in amount of tyrosine phosphorylated IRS-1 and insulin receptor in insulin-stimulated muscle. Protein tyrosine phosphatases which dephosphorylate IRS-1 and the insulin receptor will be studied because CR does not increase insulin receptor tyrosine kinase which phosphorylates IRS-1 and the receptor. Specific Aim 2 is to determine if CR enhances insulin-mediated phosphatidylinositol (PI) 3-kinase function. This enzyme is essential for CR-effect on glucose transport although CR does not alter PI 3-kinase activity determined by conventional assay with IRS-l-immunoprecipitated samples. Insulin-stimulated muscle from CR and AL rats will be compared for: a) abundance and IRS-binding of p50alpha regulatory subunit of PI 3-kinase (this isoform has been reported to elicit greater PI 3,4,5-trisphosphate production than p85alpha in intact cells, but not in IRS-l-immunoprecipitated samples); b) PI 3-kinase lipid product (PI 3,4,5-trisphosphate) levels formed by intact insulin-stimulated muscles (because CR effect may require internal milieu of intact cells); and c) activation of protein kinase B (insulin signaling step distal to and dependent on PI 3-kinase). Specific Aim 3 is to ascertain the effect of CR on 0-linked N-acetylglucosamine (G1cNAc)-modification of proteins. CR lowers muscle levels of UDP-N-acetylhexosamine (substrate for 0-GlcNAc transferase). Insulin resistance has been associated with elevated 0-GIcNAc-modified proteins (e.g., IRS-1), so lowering 0-GlcNAc-protein levels by CR could be significant for increased insulin action. Elucidating mechanisms for enhanced insulin sensitivity with CR has important implications for improving health and quality of life of older people. This research will also provide fundamental insights into CR's pleiotropic effects: tyrosine phosphatases and PI 3-kinase play key roles in several signaling pathways, and altered 0-G1cNAc-modification of proteins may mediate multiple CR-induced outcomes.