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: 6897719
• 负责人: THOMAS H REYNOLDS
• 金额: $ 4.81万
• 依托单位: ITHACA 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 2005-08-15
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6897719
• 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）：大约有1800万美国人患有糖尿病，估计每年直接医疗费用为920亿美元。2型糖尿病约占所有糖尿病的90-95%。虽然2型糖尿病的原因尚不清楚，但该疾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置的主要部位，胰岛素抵抗被认为部分是由于骨骼肌对循环胰岛素增加的适当反应能力的缺陷。该提案的目的是确定哺乳动物雷帕霉素靶蛋白（mTOR）是否在骨骼肌胰岛素抵抗的发展中起作用。mTOR是控制mRNA翻译和细胞生长的营养敏感性和胰岛素响应性丝氨酸/苏氨酸激酶。最近的细胞培养研究表明，激活mTOR通路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介导的信号转导将在骨骼肌中产生胰岛素抵抗，这一过程将被雷帕霉素逆转，雷帕霉素是一种高度特异性的mTOR抑制剂。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。我们将确定肌肉与氨基酸一起孵育是否通过胰岛素受体底物-1（IRS-1）的mTOR依赖性丝氨酸磷酸化产生胰岛素抵抗。IRS-1的丝氨酸磷酸化被认为通过降低IRS-1酪氨酸磷酸化和促进IRS-1降解而促进胰岛素抵抗。我们还将检查用氨基酸激活mTOR对胰岛素促进蛋白激酶B（PK B）在Thr 308和Ser 473上磷酸化的能力的影响。这些位点上的PKB磷酸化对于完整的激酶活性和葡萄糖转运的刺激是必需的。我们的初步数据表明，激活mTOR信号减少胰岛素刺激的PKB磷酸化Ser 473在骨骼肌中，这是一个过程，被雷帕霉素废除。最后，具体目标#1将确定用氨基酸激活mTOR信号传导是否降低胰岛素将GLUT 4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组成性激活mTOR。具体目标#2将检查与对照相比，来自经受高脂肪饮食的小鼠的肌肉中Ser 2448上的mTOR的磷酸化。Ser 2448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在胰岛素抵抗发展中发挥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型糖尿病的新型治疗方法。