基于GALR2/GLUT4信号通路探讨黄芩苷干预胰岛素抵抗的作用及机制

Insulin resistance is a key problem in diabetes treatment. Traditional Chinese medicine has a significant effect on insulin resistance. Moreover, the treatment of insulin resistance with traditional Chinese medicine has remarkable curative effect and few side effects. Scutellaria baicalensis Georgi contains several bioactive chemical compounds, baicalin is one of the most potent and abundant polyphenolic compounds extracted from it. Our previous studies have found that baicalin can enhance glucose transporter 4 (GLUT4) expression and translocation to alleviate insulin resistance. However, the detailed mechanism of baicalin in regulating insulin resistance has not been sufficiently documented as yet. Furthermore, our previous studies indicated that galanin receptor 2 (GALR2) was an important receptor in regulation of GLUT4 expression and translocation. Besides, GALR2 may mediate baicalin to improve insulin resistance. Basis on our previous studies, we hypothesize that baicalin can facilitate GLUT4 expression and translocation through activation of GALR2 signaling pathways. In this study, insulin resistance and GALR2 knockout model of mice have been established to evaluate the role of GALR2 in the intervention of baicalin in insulin resistance. Besides, the levels of GLUT4 and its associated signal molecules will be examined in skeletal muscle and GALR2 silencing myotubes. And the role of GALR2 in the mechanism of baicalin reducing insulin resistance will be in-depth explored. In brief, this study may provide a promising strategy for modern mechanism of Scutellaria baicalensis Georgi of Chinese medicine to treat insulin resistance in clinic. In addition, these contribute to our enriching the scientific connotation of the removing heat treatment of Chinese Medicine, and providing a pharmacological foundation for clinical treatment and new drug development of Scutellaria baicalensis Georgi.

胰岛素抵抗是糖尿病治疗中的关键问题。中医药对胰岛素抵抗有明显的改善作用，具有副作用小，疗效好的特点。我们前期研究发现，黄芩主要成份黄芩苷能够促进葡萄糖转运蛋白4（GLUT4）表达和膜转位，改善胰岛素抵抗，但具体作用机制不清楚。研究还发现，甘丙肽受体2（GALR2）是调节GLUT4表达和膜转位的重要受体，可能介导黄芩苷改善胰岛素抵抗。据此提出假说：黄芩苷通过激活GALR2及其下游信号通路，促进GLUT4表达和膜转位，改善胰岛素抵抗。本研究拟以黄芩苷为切入点，通过已有的胰岛素抵抗及GALR2基因敲除小鼠模型，评价GALR2在黄芩苷干预胰岛素抵抗效应中的作用；检测骨骼肌及GALR2沉默的肌细胞GLUT4及相关信号分子，深入探讨GALR2在黄芩苷干预胰岛素抵抗机制中的作用，为中药黄芩干预胰岛素抵抗现代机制研究开辟一条新的思路，丰富中医清热治则的科学内涵，为中药黄芩临床治疗和新药开发奠定药理学基础。

胰岛素抵抗是糖尿病治疗中的关键问题。中医药对胰岛素抵抗有明显的改善作用，具有副作用小，疗效好的特点。前期研究表明，黄芩主要成分黄芩苷能够促进葡萄糖转运蛋白4（GLUT4）表达和膜转位，改善胰岛素抵抗，但具体作用机制不清楚。甘丙肽受体2（GALR2）是调节GLUT4表达和膜转位的重要受体，可能介导黄芩苷改善胰岛素抵抗。在本研究中，首先我们通过高脂诱导胰岛素抵抗小鼠模型（分为对照组、Spexin组）、L6肌细胞（分为对照组、Spexin组、Spexin+M871组）及GALR2沉默的L6肌细胞（沉默对照组、沉默Spexin组）实验发现，Spexin组葡萄糖耐受及胰岛素敏感性显著增加，骨骼肌细胞GLUT4、PGC-1α、pAKT及pP38MAPK水平显著增加，胰岛素抵抗水平显著下降。而阻断或沉默GALR2后，Spexin干预的肌细胞GLUT4、PGC-1α、pAKT及pP38MAPK水平无显著改变。其次，我们通过高脂诱导胰岛素抵抗小鼠模型（分为模型对照组、黄芩苷组、M871组、黄芩苷+M871组）、GALR2基因敲除（GKO）模型（分为GKO对照组、GKO黄芩苷组、GKOM1145组、GKO黄芩苷+M1145组）、L6肌细胞（分为对照组、黄芩苷组、黄芩苷+M871组）以及GALR2沉默的L6肌细胞（沉默对照组、沉默黄芩苷组）研究发现，黄芩苷组葡萄糖耐受及胰岛素敏感性显著增加，骨骼肌细胞GLUT4、PGC-1α、pAKT及pP38MAPK表达和活性显著增加，胰岛素抵抗水平显著下降。而阻断或敲除GALR2后，黄芩苷干预的葡萄糖耐受及胰岛素敏感性无显著改变，并且骨骼肌细胞GLUT4、PGC-1α、pAKT及pP38MAPK表达和活性均无显著改变。本研究表明激活骨骼肌GALR2能够通过PGC-1α/GLUT4信号通路改善胰岛素抵抗，而黄芩苷能够通过激活GALR2/PGC-1α/GLUT4信号通路增加肌细胞葡萄糖摄取与代谢，改善胰岛素抵抗。因此，GALR2是黄芩苷降低胰岛素抵抗的重要作用靶点之一，为中药黄芩干预胰岛素抵抗现代机制研究开辟一条新的思路，丰富中医清热治则的科学内涵，为中药黄芩临床治疗和新药开发奠定药理学基础。