FAT/CD36在体外循环缺血再灌注心肌胰岛素抵抗发生机制中的作用

The mechanism of myocardial ischemia-reperfusion injury (MIRI) is still unclear. Our previous studies have shown that myocardial insulin resistance (IR), metabolic disorder of glucose and fatty acid (FA) exist in MIRI during cardiopulmonary bypass (CPB). These data also demonstrated that the decreased expression and the altered translocation of glucose transportor 4 (Glut4) is the key molecular mechanism of the metabolic disorder of glucose. However, the molecular mechanism of the metabolic disorder of FA is still unkown and that should be further studied. It was reported that the sensitivity of target tissue on insulin will be damaged by the anormal deposition of the intracellular mesostats of FA, which is closely associated with the abnormal expression or disfunction of fatty acid translocase (FAT/CD36), one of the major transporters of absorption and metabolism of myocardial FA. In this project, we will utilize in vivo and in vitro myocardial IR models to further study the relationship of the expression and translocation of FAT/CD36 and the metabolism of FA and glucose, the mesostats of FA, and cardiac function, using these techniques of isotope-labeled trace, gas chromatography, real-time RT-PCR, Western blot, siRNA, immunofluorescence and patch clamp. Therefore, this project will focus on FAT/CD36 to further elucidate the mechanism of CPB-myocardial IR and provide an important academic and practical significance for prevention and treatment of MIRI.

心肌缺血再灌注损伤（MIRI )的发生机制仍不甚清楚。前期研究表明，体外循环MIRI过程中存在心肌胰岛素抵抗（IR），该过程中葡萄糖及脂肪酸代谢紊乱，葡萄糖转运蛋白4（Glut4）表达及转运障碍是葡萄糖代谢紊乱的关键分子机制，但脂肪酸代谢紊乱的分子机制需进一步研究。文献显示，脂代谢中间产物的异常蓄积可能会影响靶组织对胰岛素的敏感性；脂肪酸转位酶（FAT/CD36）介导心肌脂肪酸摄取和代谢，其表达或功能异常与细胞内脂代谢中间体的蓄积密切相关。本课题拟利用在体及离体心肌IR模型，采用同位素示踪、气相色谱法、实时定量PCR、Western blot、siRNA技术、免疫荧光染色及膜片钳等技术，深入研究FAT/CD36的表达及转位调节与FA、葡萄糖摄取利用、脂代谢中间体蓄积及心功能关系，以FAT/CD36为靶点，进一步阐明体外循环心肌IR的发生机制，对MIRI的防治具有重要的学术价值及现实意义。

心肌缺血再灌注损伤（MIRI )的发生机制仍不甚清楚。我们前期研究表明，体外循环MIRI过程中存在心肌胰岛素抵抗（IR），该过程中葡萄糖及脂肪酸代谢紊乱，葡萄糖转运蛋白 4（Glut4）表达及转运障碍是葡萄糖代谢紊乱的关键分子机制，但脂肪酸代谢紊乱的分子机制需进一步研究。文献显示，脂肪酸转位酶（FAT/CD36）介导心肌脂肪酸摄取和代谢，其表达或功能异常与细胞内脂代谢中间体的蓄积密切相关。本项目采用在体及离体心肌IR模型，应用气相色谱法、实时定量PCR、Western blot、siRNA技术、免疫荧光染色及膜片钳等技术，深入研究FAT/CD36的表达及转位与脂肪酸、脂代谢中间体蓄积及心功能的关系。结果显示：在体外循环MIRI过程中，心肌细胞中FAT/CD36呈高表达和高转位，动作电位的APA和APD降低；LCACoA是心肌细胞脂代谢的重要中间产物，可作为心肌IR脂代谢紊乱的一个标志物; 沉默PPARγ表达后，心肌细胞脂代谢紊乱加重，进而加重MIRI；罗格列酮可改善体外循环 MIRI过程的脂代谢紊乱，其机制是抑制FAT/CD36表达、增加PPARγmRNA及降低LCACoA含量。 MIRI后脂代谢紊乱加重的机制可能是下调PPARγ对FAT/CD36的负向调节作用，使得心肌细胞FAT/CD36的转位和表达异常升高，导致心肌细胞异常摄取FA、动作电位的APA和APD下降减缓，心肌细胞异常堆积LCACoA。