TGR5受体在高糖刺激下心肌细胞功能调控中的作用及信号转导机制

Oxidative stress induced by abnormal glucose metabolism contributes to impaired cardiac function. The G protein-coupled receptor TGR5 has recently been recognized as a novel metabolic switch. TGR5 activation can improve the metabolism of glucose and reduce oxidative stress. Our previous study has shown that the TGR5 receptor agonist can increase Nrf2 nuclear translocation and subsequent upregulation of HO-1, which reduce oxidative stress injury. However, the role of TGR5 in modulation of cardiomyocytes function under high glucose and related signal transduction mechanism remain unclear. The current study shows that TGR5 activation can cause phosphorylation of Akt and GSK-3b in cardiomyocytes. Akt and GSK-3b are upstream regulators of Nrf2 activation. Thus, we hypothesized that Nrf2/HO-1 are involved in TGR5-mediated regulation of cardiomyocytes function in which Akt and GSK-3b are likely to participate. Using cardiomyocytes, the present study has been performed to investigate the protective effect of TGR5 activation against high glucose-induced dysfunction on cardiomyocytes and whether Nrf2/HO-1 signaling pathway is involved. In the study, Phosphorylation of signaling proteins, intracellular calcium transients, cell apoptosis and hypertrophy will be measured by molecular biology and morphological techniques. The resolution of these issues is expected to recognize the role and mechanism of TGR5 receptor again and enrich content of cardiovascular receptor theory.

糖代谢异常引起氧化应激，导致心肌功能受损。TGR5受体是近来发现的代谢调节开关，激动TGR5受体有利于改善机体糖代谢，减轻氧化应激。申请者前期研究发现TGR5受体激动剂能导致血管平滑肌细胞Nrf2核转位，激活HO-1的表达，减轻氧化损伤。但目前尚不知TGR5受体在高糖刺激下心肌细胞功能调控中的作用及受体后信号转导机制。现有的研究表明激动TGR5能引起心肌细胞Akt和GSK-3b磷酸化。因Akt和GSK-3b是激活Nrf2的上游因子，故推测Nrf2/HO-1途径可能参与了TGR5调控高糖环境下心肌细胞功能。因此，本项目拟采用心肌细胞，结合分子生物学及形态学技术，以信号蛋白磷酸化、细胞内钙瞬变、细胞凋亡及肥大等为主要观察指标，阐明激动TGR5受体对高糖时心肌细胞功能的影响及分子机制。这些问题的解决有望从基因转录调控角度再认识TGR5受体的作用及其机制，丰富心血管受体学理论。

糖代谢异常引起氧化应激，导致心肌功能受损。TGR5受体是近来发现的代谢调节开关，激动TGR5受体有利于改善机体糖代谢，减轻氧化应激。但目前尚不知TGR5受体在高糖刺激下心肌细胞功能调控中的作用及受体后信号转导机制。本研究发现（1）激活TGR5能减轻高糖诱导的ROS产生及激活Nrf2/HO-1信号通路；并通过激活Nrf2/HO-1信号通路减轻ROS的生成及ROS导致的心肌细胞凋亡。（2）我们还发现激活TGR5还能减轻高糖诱导心肌细胞肥大及炎症因子的表达，是通过抑制NF-κB，MAPK及CaN/NFAT3信号途径实现的。同时在糖尿病小鼠模型中我们也发现给予TGR5特异性激动剂INT-777能改善糖尿病小鼠心脏功能及炎症因子的分泌。（3）在小鼠心肌成纤维细胞中，给予TGR5过表达病毒能抑制心肌成纤维细胞胶原蛋白的分泌，并抑制血管紧张素II诱导的小鼠心肌成纤维细胞的增殖，并探讨了其中的分子机制。（4）同时我们也发现条件表达间充质干细胞上的血管紧张素II的2型受体能抑制血管损伤后的内膜新生，为心血管系统的受体研究拓展了方向，取得了一些初步数据，为本项目的进一步延伸打下了基础。（5）发现一些天然TGR5受体激动剂（如齐墩果酸等）能抑制心肌成纤维细胞增殖。本项目培养硕士研究生6名，直接或间接资助发表论文17篇，其中SCI论文1篇，中文核心期刊16篇，另有一篇中文核心期刊论文接收。