Mammalian Target of Rapamycin and Insulin Resistance

雷帕霉素和胰岛素抵抗的哺乳动物靶标

• 批准号: 7139915
• 负责人: THOMAS H REYNOLDS
• 金额: $ 14.11万
• 依托单位: SKIDMORE COLLEGE
• 依托单位国家: 美国
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-03-01 至 2008-02-29
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7139915
• 关键词: SDS polyacrylamide gel electrophoresis; aminoacid; biological signal transduction; cell membrane; dietary lipid; disease /disorder etiology; enzyme activity; enzyme linked immunosorbent assay; glucose transport; glutathione; hyperinsulinism; immunoprecipitation; insulin receptor; insulin sensitivity /resistance; kinase inhibitor; laboratory mouse; messenger RNA; muscle function; noninsulin dependent diabetes mellitus; phosphorylation; scintillation counter; serine threonine protein kinase; sirolimus; striated muscles; western blottings

DESCRIPTION (provided by applicant): Approximately 18 million Americans have diabetes resulting in an estimated $92 billion in direct medical costs per year. Type 2 diabetes mellitus accounts for approximately 90-95% of all diabetes. Although the cause of type 2 diabetes is unknown, one common factor of the disease is insulin resistance. Since skeletal muscle is the primary site for insulin-mediated glucose disposal, insulin resistance is thought to be due, in part, to a defect in skeletal muscle's ability to respond appropriately to increases in circulating insulin. The goal of this proposal is to determine whether or not the mammalian target of rapamycin (mTOR) plays a role in the development of skeletal muscle insulin resistance. mTOR is a nutrient sensitive and insulin responsive serine/threonine kinase that controls mRNA translation and cellular growth. Recent cell culture studies have demonstrated that activating the mTOR pathway inhibits insulin signal transduction and promotes insulin resistance. Our first hypothesis is that activating mTOR-mediated signal transduction will produce insulin resistance in skeletal muscle, a process that will be reversed by rapamycin, a highly specific inhibitor of mTOR. Specific aim #1 will examine the effects of mTOR-mediated signaling on insulin action in skeletal muscle. We will determine if incubating muscle with amino acids produces insulin resistance by an mTOR dependent serine phosphorylation of the insulin receptor substrate-1 (IRS-1). Serine phosphorylation of IRS-1 is thought to promote insulin resistance by decreasing IRS-1 tyrosine phoshorylation and promoting IRS-1 degradation. We will also examine the effects of activating mTOR with amino acids on insulin's ability to promote the phosphorylation of protein kinase B (PKB) on Thr308 and Ser473. Phosphorylation of PKB on these sites is necessary for full kinase activity and the stimulation of glucose transport. Our preliminary data indicate activating mTOR signaling reduces insulin-stimulated PKB phosphorylation on Ser473 in skeletal muscle, a process that is abolished by rapamycin. Finally, specific aim #1 will determine if activating mTOR signaling with amino acids decreases insulin's ability to recruit GLUT4 to the cell surface and stimulate glucose transport in skeletal muscle. Our second hypothesis is that the hyperinsulinemia associated with diet-induced insulin resistance constitutively activates mTOR. Specific aim #2 will examine the phosphorylation of mTOR on Ser2448 in muscles from mice subjected to a high fat diet compared to controls. Ser2448 is a site in mTOR whose phosphorylation is associated with increased kinase activity. The results from these studies will provide new insights into factors that play a role in the development of insulin resistance and possibly lead to the use of mTOR inhibitors as novel treatments for type 2 diabetes.

描述（由申请人提供）：大约 1800 万美国人患有糖尿病，每年造成的直接医疗费用估计为 920 亿美元。 2 型糖尿病约占所有糖尿病的 90-95%。尽管2型糖尿病的病因尚不清楚，但该病的一个常见因素是胰岛素抵抗。由于骨骼肌是胰岛素介导的葡萄糖处理的主要场所，因此胰岛素抵抗被认为部分是由于骨骼肌对循环胰岛素增加做出适当反应的能力缺陷所致。该提案的目的是确定哺乳动物雷帕霉素靶点 (mTOR) 是否在骨骼肌胰岛素抵抗的发展中发挥作用。 mTOR 是一种营养敏感且胰岛素敏感的丝氨酸/苏氨酸激酶，可控制 mRNA 翻译和细胞生长。最近的细胞培养研究表明，激活 mTOR 通路会抑制胰岛素信号转导并促进胰岛素抵抗。我们的第一个假设是，激活 mTOR 介导的信号转导会在骨骼肌中产生胰岛素抵抗，这一过程将被雷帕霉素（一种高度特异性的 mTOR 抑制剂）逆转。具体目标#1 将检查 mTOR 介导的信号传导对骨骼肌中胰岛素作用的影响。我们将通过胰岛素受体底物 1 (IRS-1) 的 mTOR 依赖性丝氨酸磷酸化来确定用氨基酸孵育肌肉是否会产生胰岛素抵抗。 IRS-1 的丝氨酸磷酸化被认为通过降低 IRS-1 酪氨酸磷酸化并促进 IRS-1 降解来促进胰岛素抵抗。我们还将研究用氨基酸激活 mTOR 对胰岛素促进蛋白激酶 B (PKB) Thr308 和 Ser473 磷酸化的能力的影响。 PKB 在这些位点上的磷酸化对于完整的激酶活性和刺激葡萄糖转运是必需的。我们的初步数据表明，激活 mTOR 信号传导可减少骨骼肌中胰岛素刺激的 Ser473 上的 PKB 磷酸化，而雷帕霉素可消除这一过程。最后，具体目标#1 将确定用氨基酸激活 mTOR 信号传导是否会降低胰岛素将 GLUT4 募集到细胞表面并刺激骨骼肌中葡萄糖转运的能力。我们的第二个假设是，与饮食诱导的胰岛素抵抗相关的高胰岛素血症会持续激活 mTOR。具体目标#2 将检查与对照组相比，高脂肪饮食小鼠肌肉中 mTOR Ser2448 的磷酸化情况。 Ser2448 是 mTOR 中的一个位点，其磷酸化与激酶活性增加相关。这些研究的结果将为了解胰岛素抵抗发展中起作用的因素提供新的见解，并可能导致使用 mTOR 抑制剂作为 2 型糖尿病的新疗法。