GLUCOSE TOXICITY IN SKELETAL MUSCLE

糖尿病引起的高血糖加剧了胰岛素抵抗。 通过葡萄糖对骨骼肌的直接毒性作用。这又反过来 导致血糖控制恶化和糖尿病的发展 发病率。葡萄糖对人体产生毒性作用的机制 骨骼肌尚不清楚，但最终结果是降低了对 肌肉GLUT4葡萄糖转运蛋白到胰岛素。一批转基因小鼠 已经开发出其中构成Glut1葡萄糖转运体的 特别是在骨骼肌中过度表达。基础葡萄糖转运是 在这些小鼠的肌肉中显著升高，通过结构性 Glut1在肌膜中的过表达。增加的基础通量 葡萄糖进入肌肉模拟高血糖的影响，并导致 GLUT4的脱敏作用。这些小鼠提供了一个独特的模型系统 体内肌肉葡萄糖毒性的直接效应研究 没有因高血糖和循环改变而产生的副作用 胰岛素水平。最近的证据表明，葡萄糖流量的增加 通过氨基葡萄糖代谢途径可能对葡萄糖负责- 诱导骨骼肌胰岛素抵抗。这样做的长期目标是 该项目旨在利用这种转基因小鼠模型来帮助阐明 葡萄糖诱导骨骼肌胰岛素抵抗的机制。至 为实现这一目标，我们提出了以下具体目标： L。为确定胰岛素和收缩是否诱导心肌细胞易位 Glut1肌肉中的Glut4到质膜均有缺陷 转基因小鼠使用定量免疫金电子显微镜。 2.确定体内细胞内游离葡萄糖的升高 影响骨骼肌基因表达模式并鉴定 可能导致葡萄糖毒性的新基因。这将是 利用逆转录差异表达技术实现mRNA的显示 Glut1转基因骨骼肌的分析。 3.确定氨基葡萄糖代谢的改变是否参与了 Glut1转基因小鼠GLUT4激活缺陷。这将是 探讨氨基葡萄糖对GLUT4的直接作用 在肌肉中的移位，测量体内氨基葡萄糖代谢产物的水平 Glut1转基因小鼠的肌肉，并检测氨基葡萄糖的作用 人葡萄糖调控候选基因的表达研究 特定目标#2.过表达谷氨酰胺的转基因小鼠：果糖-6- 肌肉中的磷酸氨基转移酶将被产生并鉴定 为了直接测试增加氨基葡萄糖的假设 代谢是葡萄糖诱导的胰岛素抵抗的原因 骨骼肌。

The hyperglycemia associated with diabetes exacerbates insulin resistance via a direct toxic effect of glucose on skeletal muscle. This in turn contributes to the worsening of glycemic control and the development of morbidity. The mechanism by which glucose exerts a toxic effect on skeletal muscle is unknown, but the end result is decreased sensitivity of the muscle Glut4 glucose transporter to insulin. A line of transgenic mice has been developed in which the constitutive Glut1 glucose transporter is overexpressed specifically in skeletal muscle. Basal glucose transport is dramatically elevated in the muscle of these mice via the constitutive overexpression of Glut1 in the sarcolemma. The increased basal flux of glucose into muscle mimics the effect of hyperglycemia and results in the desensitization of Glut4. These mice provide a unique model system for studying the direct effects of muscle glucose toxicity in vivo in the absence of secondary effects due to hyperglycemia and altered circulating insulin levels. Recent evidence suggests that increased flux of glucose through the glucosamine metabolic pathway may be responsible for glucose- induced insulin resistance in skeletal muscle. The long-term goal of this project is to exploit this transgenic mouse model to help elucidate the mechanism of glucose-induced insulin resistance in skeletal muscle. To accomplish this goal, we propose the following specific aims: l. To determine whether insulin and contraction-induced translocation of Glut4 to the plasma membrane are defective in the muscle of Glut1 transgenic mice using quantitative immunogold electron microscopy. 2. To determine how elevation of intracellular free glucose in vivo affects the pattern of skeletal muscle gene expression and to identify novel genes that may contribute to glucose toxicity. This will be accomplished by the use of reverse transcription differential mRNA display analysis of the Glut1 transgenic skeletal muscle. 3. To determine whether altered glucosamine metabolism is involved in the defect in Glut4 activation in the Glut1 transgenic mice. This will be explored by investigating the direct effect of glucosamine on Glut4 translocation in muscle, measuring levels of glucosamine metabolites in muscle of Glut1 transgenic mice, and examining the effect of glucosamine on the expression of glucose-regulated candidate genes identified in specific aim #2. Transgenic mice overexpressing glutamine:fructose-6- phosphate amidotransferase in muscle will be generated and characterized in order to directly test the hypothesis that increased glucosamine metabolism is responsible for glucose-induced insulin resistance in skeletal muscle.