Muscle Glucose Metabolism in Diabetes and Exercise

描述（由申请方提供）：胰岛素抵抗是肥胖的共病，是2型糖尿病和心血管疾病发展的风险因素。我们和其他人已经证明，肌肉脂质积累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）研究导致脂质在肥胖个体肌肉中积聚的机制;（2）研究肌肉脂质与胰岛素信号转导失调之间的联系机制。我们的假设是，脂质（如脂肪酰辅酶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，因为脂肪酸跨细胞膜的摄取增加。积累的脂质然后激活PKC，这导致胰岛素受体和IRS-1的磷酸化和失活，以及胰岛素抵抗。在具体目标1中，我们将继续研究脂肪酸转运和脂肪酸转运蛋白的表达是否在肥胖个体的肌肉中改变。我们将使用肌肉活检的体内研究（例如高胰岛素钳夹）或孵育肌纤维条制备物的体外实验，然后制备巨膜囊泡，以确定肥胖症脂肪酸转运蛋白的膜分布是否发生变化（具体目的2）。在具体目标3中，我们计划使用来自瘦和肥胖患者的培养的肌管来研究操纵脂肪酸转运是否会改变细胞内脂质的积累和胰岛素信号传导。为了研究脂质和胰岛素信号转导之间的联系，我们将使用我们孵育的肌条制备物来急性改变肌肉脂质的积累，并确定是否存在与我们的假设一致的PKC激活和胰岛素受体和IRS-1磷酸化的伴随变化（具体目的4）。这些研究的结果将为胰岛素抵抗和糖尿病的病因和可能的治疗方法提供有价值的信息。

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.