PGC-1α调节骨骼肌脂肪酸代谢和胰岛素抵抗的分子机制

Abnormal fatty acid metabolism in skeletal muscle leads to the development of insulin resistance (IR). Peroxisome proliferator-activated receptor (PPAR) γ coactivator-1α (PGC-1α) plays a very important role in fatty acid metabolism and insulin resistance. Our previous studies have demonstrated that PGC-1α expression level is decreased in skeletal muscles of high-fat-fed rats, and the decrease of PGC-1α is associated with a reduced expression of CPTⅠβ which is a critical enzyme in fatty acid metabolism, and the development of IR. Striated activator of Rho signaling (STARS), an actin-binding protein, is reported to act as a regulator of skeletal muscule metablism, and increased in skeletal muscles of Type 2 diabetic patients and negatively correlated with insulin resistance. PGC-1α might regulate fatty acid metabolism through STARS and CPTⅠβ. The aim of this proposal is to investigate the mechanistic role of PGC-1a and its pathway including STARS and CPT1β, in the development of abnormal fatty acid metabolism and insulin resistance in cells and high-fat-fed rats by using Adenovirus, ChIP and luciferase gene report system etc. The findings will provide useful data to understand the molecualr mechnisam of the IR formaiton and identify potential new targets for preventing insulin resistance in humans.

骨骼肌脂肪酸代谢异常导致胰岛素抵抗（IR），过氧化物酶体增生物激活受体γ共激活因子1α（PGC-1α）与脂肪酸代谢和IR关系密切。我们前期研究证实高脂喂养大鼠骨骼肌PGC-1α表达下降，伴有脂肪酸关键酶CPTⅠβ表达下降和IR。Striated activator of Rho signalling (STARS)是一种肌动蛋白结合蛋白，参与骨骼肌代谢，其在2型糖尿病患者骨骼肌表达升高，且与胰岛素敏感性呈负相关。PGC-1α可能通过调控STARS、CPTⅠβ发挥调节脂肪酸代谢和胰岛素敏感性的作用。本项目拟通过腺病毒转染，染色质免疫沉淀和荧光素酶报告基因系统等方法，从动物和细胞水平探讨PGC-1α在高脂诱导的脂肪酸代谢异常和IR形成中的分子机制，揭示PGC-1α、STARS和CPTⅠβ这一信号通路在IR形成中的作用，为阐明IR的发病机制、寻找新的药物治疗靶点提供理论依据。

背景：高脂喂养大鼠骨骼肌PGC-1α表达下降，伴有脂肪酸关键酶CPTⅠβ表达下降和IR。STARS在2型糖尿病患者骨骼肌表达升高，且与胰岛素敏感性呈负相关。PGC-1α可能通过调控STARS、CPTⅠβ发挥调节脂肪酸代谢和胰岛素敏感性的作用。本项目拟探讨PGC-1α在高脂诱导的脂肪酸代谢异常和IR形成中的分子机制，揭示PGC-1α、STARS和CPTⅠβ这一信号通路在IR形成中的作用，寻找新的药物治疗靶点提供理论依据。.研究内容：选取雄性SD大鼠分为对照组（C）和高脂组（HF），测定骨骼肌组织PGC-1α，脂肪酸代谢以及胰岛素信号通路的表达变化。应用棕榈酸孵育的L6 骨骼肌细胞，通过基因转染技术调节PGC-1α以及STARS的表达，观察脂肪酸代谢相关基因、胰岛素信号通路相关因子的表达变化。.研究结果： （1）与C组相比，HF组血糖、血脂增高（均P<0.05），骨骼肌PGC-1α表达降低， STARS表达升高，IRS-1、AKT、GLUT4表达均降低（均P<0.01）。（2）与Con组相比，PA组胰岛素敏感性下降。PGC-1α、IRS-1、AKT及GLUT4的mRNA的表达下降，STARS表达升高（均P<0.05）。（3）与Con组相比，pcDNA3/PGC-1α组STARS表达下降(P<0.05)。CPT-1β、IRS-1、AKT、GLUT4的mRNA表达升高(均P<0.05)。p-ACC、p-AKT、GLUT4蛋白表达升高，而p-IRS-1（Ser307）表达降低（均P<0.05）。与PA组相比，PA+ pcDNA3/PGC-1α组STARS表达下降(P<0.01)， CPT-1β、IRS-1、AKT及GLUT4的mRNA表达升高（均P<0.05）。（4）与Con组相比，si-PGC-1α组STARS表达增高，CPT-1β mRNA表达下降，p-ACC的蛋白表达降低（均P<0.05），IRS-1、AKT、GLUT4的mRNA表达均下降，p-IRS-1的表达升高，p-AKT以及GLUT4的蛋白表达均降低（均P<0.05）。（5）棕榈酸干预后应用转染技术调节STARS表达：与control相比，pcDNA/STARS组肌细胞STARS基因和蛋白表达均显著增加；与PA组相比，PA+pcDNA/STARS组肌细胞STARS基因和蛋白表达均显著增加，差异具有统计学意义（均P