转甲状腺素蛋白在运动改善肥胖小鼠胰岛素抵抗中的作用研究

项目名称： 转甲状腺素蛋白在运动改善肥胖小鼠胰岛素抵抗中的作用研究

项目编号： No.81471099

项目类型： 面上项目

立项/批准年度： 2015

项目学科： 医药、卫生

项目作者： 郑芬萍

作者单位： 浙江大学

项目金额： 65万元

中文摘要： 胰岛素抵抗（IR）是2型糖尿病发生的基本环节，运动改善IR的机制主要涉及AMPK活性增加，但调节分子不详。我们前期研究发现高脂饮食诱导的肥胖小鼠（DIO）肝脏转甲状腺素蛋白（TTR）表达分泌增加，而运动显著降低肝脏TTR表达和循环TTR水平，且此变化独立于运动导致的体重下降作用；运动能降低骨骼肌TTR蛋白摄取，伴随糖脂代谢关键信号通路-AMPK活性增加；而体外证实TTR蛋白剂量依赖性抑制骨骼肌细胞C2C12的AMPK活性，由此提出运动可能通过降低肝脏TTR表达分泌、减少骨骼肌TTR蛋白摄取继而增加AMPK活性改善局部糖脂代谢和线粒体功能而改善IR。本研究拟利用DIO小鼠跑台模型，借助原代细胞分离、重组腺病毒表达载体构建、蛋白标记及激光共聚焦等方法，观察慢性运动训练诱导的TTR下降在运动改善IR、调节骨骼肌能量代谢中的介导作用，旨在进一步阐明运动改善IR的机制，为2型糖尿病的防治寻找新的靶点

中文关键词： 转甲状腺素蛋白；运动；AMP依赖蛋白激酶；胰岛素抵抗

英文摘要： Studies have shown that the prevention of type 2 diabetes should mainly focus on insulin resistance (IR) interference. It has become a consencus that exercise can improve insulin sensitivity involving AMPK though the upstream molecule regulating the AMPK activity is far from clarified. Our previous studies have shown that Ttr mRNA levels in liver, as well as TTR protein levels in serum were significantly decreased in the exercised rats compared with the sedentary ones, which were independent on exercise-induced weight loss.Ttr expression and secretion were increased in mice maintained on high fat diet comared with those on regular chow. However,TTR protein was significantly decreased in skeletal muscle of the exercised rats, accompanied by an increase in AMPK activity, which plays a key role in the metabolism of glucose and fatty acid. Moreover, exogenous TTR pure protein significantly inhibited the AMPK pathway activity in C2C12 cells in a dose- and time-dependent manner.Based on our previous findings, we assumed that decreased Ttr expression in the liver induced by exercise, together with the decreased serum TTR levels would result in a lower TTR endocytosis in skeletal muscle, contributing to an increased AMPK alpha phosphorylation and higher utilization of glucose and fatty acid and improvement of mitochondrial number and function. The aims of the present study are to further clarify the mechanism of whole body insulin sensitivity improvement due to exercise and try to find a new molecular target for type 2 diabetes prevention. For these aims, in vitro we would like to adopt the C2C12 cells and primary muscle cell from newborn Sparague-Dawley rats and in vivo to use obese and insulin resistant mice models induced by high fat diet, as well as different exercised-mice models (mice of treamill exercise and one blos of exercise ), using the methods of hyperinsulinemic-euglycemic clamp for insulin sensitivity assessment and recombinant adenovirus expression vector for over-expression or knock-down Ttr gene expression in the liver, to see whether the decreased TTR in liver and serum could play a key role in the improvement of insulin sensitivity and AMPK activity in the muscle induced by exercise.

英文关键词： Transthyretin;exercise;AMPK;insulin resistance