Muscle Glucose Metabolism in Diabetes and Exercise

描述（由申请人提供）：胰岛素抵抗是肥胖的合并症，是2型糖尿病和心血管疾病发展的危险因素。我们和其他人已经证明，积累的肌肉脂质和胰岛素抵抗之间存在关系。因此，本项目的重点是两个方面：(1)研究肥胖个体肌肉中脂质积累的机制；(2)研究肌肉脂质与胰岛素信号转导失调的联系机制。我们的假设是脂质（如脂肪酸酰基辅酶a，二酰基甘油和/或神经酰胺）在胰岛素抵抗个体的肌肉中积累是因为脂肪酸在细胞膜上的摄取增加。积累的脂质随后激活PKC，导致胰岛素受体和IRS-1的磷酸化和失活，以及胰岛素抵抗。在具体目标1中，我们将继续研究肥胖个体肌肉中脂肪酸转运和脂肪酸转运蛋白的表达是否发生改变。我们将使用肌肉活组织检查的体内研究（例如高胰岛素钳）或体外实验，用培养的肌纤维条制备，然后制备巨大的膜泡，来确定肥胖是否会改变脂肪酸转运体的膜分布（特定目的2）。在具体目标3中，我们计划使用来自瘦肉和肥胖患者的培养肌管来研究操纵脂肪酸运输是否会改变细胞内脂质和胰岛素信号的积累。为了研究脂质和胰岛素信号转导之间的联系，我们将使用我们的培养肌条制剂来剧烈改变肌脂的积累，并确定是否伴随PKC的激活和胰岛素受体和IRS-1的磷酸化的变化，这与我们的假设一致（具体目标4）。拟议的研究结果应该为胰岛素抵抗和糖尿病的原因和可能的治疗提供有价值的信息。

DESCRIPTION (provided by applicant): Insulin resistance is a co-morbidity of obesity and is a risk factor for the development of type-2 diabetes and cardiovascular disease. We, and others, have demonstrated that there is a relationship between accumulated muscle lipids and insulin resistance. Therefore, the focus of this project is two fold: (1) to investigate the mechanism that causes lipids to accumulate in muscle of obese individuals and (2) to investigate the mechanism that links muscle lipids to disregulation of insulin signal transduction. Our hypothesis is that lipids accumulate (e.g. fatty acyl CoAs, diacylglycerols and/or ceramide) in muscle of insulin resistant individuals because of increased uptake of fatty acids across the cell membrane. The accumulated lipids then activate PKC, which leads to the phosphorylation and inactivation of insulin receptors and IRS-1, and insulin resistance. In specific aim 1 we will continue to investigate whether fatty acid transport and expression of fatty acid transporters are altered in muscle of obese individuals. We will use in vivo studies (e.g. hyperinsulinemic clamp) with muscle biopsies or in vitro experiments with the incubated muscle fiber strip preparation, followed by preparation of giant membrane vesicles, to determine if there are alterations in the membrane distribution of fatty acid transporters with obesity (specific aim 2). In specific aim 3 we plan to use cultured muscle myotubes from lean and obese patients to investigate whether manipulating fatty acid transport will alter accumulation of intracellular lipid and insulin signaling. To investigate the link between lipids and insulin signal transduction, we will use our incubated muscle strip preparation to acutely alter the accumulation of muscle lipids and determine if there are accompanying changes in activation of PKC and phosphorylation of insulin receptors and IRS-1 that are consistent with our hypothesis (specific aim 4). The results of the proposed studies should provide valuable information about the causes and possible treatments of insulin resistance and diabetes.