以67-LR为切入点探讨茶多酚通过AMPKα2-MEF2A-GLUT4信号通路对乙醇所致心肌胰岛素抵抗的作用机制研究

We previously found that chronic and heavy ethanol consumption led to insulin resistance mainly via AMPK signal pathway. And myocardium is more sensitive to ethanol than liver, skeletal muscle and adipose tissue, et al. Tea polyphenols may improve insulin resistance induced by some factors other than ethanol. In this project we intend to investigate the following issues in myocardium of AMPKα2-/- and AMPKα2+/+ mouse and two kinds of cardiomyocytes with dominant negative mutant technology, RNA interference, chromatin immunoprecipitation, co-immunoprecipitation and so on. First to observe the improvement of tea polyphenols on chronic and heavy alcohol induced insulin resistance. Second to explore whether the above effects are associated with activation of AMPKα2-MEF2A-GLUT4 signal pathway. Third to investigate the dependence on 67-kDa laminin receptor. This study may provide effective means for improving insulin resistance evoked by chronic ethanol exposure and lowering the incidence of type 2 diabetes, also provide important experimental basis and theoretical supports for further development of green tea extracts. The expected results indeed possess critical social significances and economical values, especially for one country owning huge number of drinkers and green tea like us.

前期研究发现，长期大量饮酒主要通过AMPK信号通路诱导机体胰岛素抵抗，心肌对乙醇更为敏感，但未进行相应药物的干预研究；茶多酚可改善部分非乙醇性因素诱导的胰岛素抵抗。本项目拟以长期饮酒的AMPKα2基因敲除鼠和野生鼠的心肌组织和2种心肌细胞为研究对象，应用显性负性突变体转染、RNA干扰、染色质免疫沉淀、免疫共沉淀等多种技术，从整体-细胞-分子层次证实：⑴茶多酚对长期大量饮酒所致胰岛素抵抗的改善作用；⑵该作用是否通过激活AMPKα2-MEF2A-GLUT4信号通路而发挥；⑶该作用是否依赖于其受体67-kDa层粘连蛋白受体 (67-laminin receptor, 67-LR)。该研究将为改善长期饮酒所致胰岛素抵抗，降低2型糖尿病发生风险提供有效手段，也为茶叶提取物的深入开发提供重要的实验基础和理论支持。其研究结果对于我们这样一个饮酒大国和茶叶生产大国，无疑具有重要的社会学意义和经济学价值。

现有流行病学调查和基础研究均证实，长期大量饮酒可明显增加2型糖尿病的发生风险和发病率，但缺乏相应的干预措施。我们前期经过大量研究发现，长期大量饮酒主要通过AMPK信号通路诱导机体胰岛素抵抗；在胰岛素主要靶器官中以心肌对乙醇更为敏感；结合茶多酚可诱导AMPK活化的文献资料，我们提出“茶多酚通过AMPK信号通路改善乙醇诱导的心肌胰岛素抵抗”的假说。. 本项目从整体、细胞、分子层次对茶多酚改善乙醇所致心肌胰岛素抵抗的作用及其机制进行了深入探讨，发现：⑴茶多酚对长期大量饮酒所致胰岛素抵抗具有明显的改善作用；⑵茶多酚可使乙醇抑制的葡萄糖转运增强，该过程是通过诱导AMPKα2活化、进而促进转录因子MEF2A与靶基因启动子结合、继而增强GLUT4表达和膜转位，从而使细胞转运葡萄糖的能力增强，葡萄糖摄取得到改善；⑶茶多酚对AMPKα2-MEF2A-GLUT4信号通路的作用依赖于其受体67-LR；阻断67-LR后，茶多酚的上述作用被明显抑制。. 上述研究结果证实了我们的科学假说，为降低2型糖尿病发生风险、促进茶叶的深入开发利用提供了实验依据。