RBP4诱导Th17/Treg失衡在促进2型糖尿病心肌纤维化中的作用研究

Diabetic cardiomyopathy (DCM) is the major cause of heart failure in patients with type 2 diabetes. Cardiac fibrosis is the specific pathogenic feature of DCM. Imbalance of Th17/Treg induces cardiac inflammation, which plays crucial role in the process of diabetic cardiac fibrosis. Retinol binding protein 4 (RBP4) is a novel proinflammatory adipokine. Our previous studies showed that RBP4 promoted cardiac insulin resistance and pathogenic hypertrophy via inducing TLR4/MyD88 pathway. Moreover, serum RBP4 level was increased in mice with DCM, and positively correlated with the index of cardiac fibrosis and imbalance of Th17/Treg. It has been reported that TLR4/MyD88 pathway is involved in the development of Th17/Treg imbalance. Thus, our project will firstly construct type 2 diabetes model using RBP4 transgenic and knockout mice to investigate the role of RBP4 in diabetic cardiac fibrosis. Then T lymphocyte and cardiac fibroblast co-culture model will be used to explore whether RBP4 promotes diabetic fibrosis via inducing Th17/Treg imbalance. At last, we will construct type 2 diabetes model using TLR4 and MyD88 knockout mice to investigate whether TLR4/MyD88 pathway is involved in the promoting role of RBP4 in diabetic fibrosis. This proposal will provide a new insight into prevention and treatment for DCM.

糖尿病心肌病（DCM）是2型糖尿病患者心力衰竭的主要原因，心肌纤维化是DCM特征性病理改变。T淋巴细胞亚群Th17/Treg失衡诱导的炎症反应在其中起重要作用。视黄醇结合蛋白4（RBP4）是新的促炎因子，我们前期发现RBP4可通过TLR4/MyD88通路促进心肌细胞胰岛素抵抗和病理性肥大；且RBP4水平在DCM小鼠升高，并与心肌纤维化及Th17/Treg失衡呈正相关。而TLR4/MyD88通路异常激活可促进Th17/Treg失衡。本项目将利用RBP4转基因和敲除小鼠糖尿病模型研究RBP4对糖尿病心肌纤维化的影响；并结合T淋巴细胞/心脏成纤维细胞共培养模型，研究RBP4是否通过诱导Th17/Treg失衡促进心肌纤维化；最后利用TLR4和MyD88敲除小鼠糖尿病模型研究RBP4是否通过TLR4/MyD88通路诱导Th17/Treg失衡，促进糖尿病心肌纤维化。本研究将为DCM的防治提供新思路。

本项目前期研究结果证实（Retinol binding protein 4，RBP4）具有促进胰岛素抵抗和心肌重构的双重作用，可以通过激活心肌细胞TLR4/MyD88信号通路在“心力衰竭-胰岛素抵抗”恶性循环中起关键性的促进作用，提示RBP4可能参与介导了糖尿病性心肌病的心肌重构进程。在项目实施过程中，课题组同样发现RBP4在缺血性心脏病（Ischemic heart disease，IHD）的发生发展中起重要作用，而RBP4在糖尿病心肌纤维化中的作用已有较多文献报道，因此本项目深入开展了RBP4参与IHD的作用及机制研究。.主要研究结果：一、冠心病患者血清RBP4水平明显升高，并与氧化应激损伤及动脉粥样硬化程度相关。二、RBP4水平在亚临床甲减患者中有明显升高，升高的RBP4水平是冠心病发病的独立危险因素，且RBP4水平随着冠脉病变严重程度增加而升高。三、血清RBP4水平在缺血性心力衰竭患者中有明显升高，并且RBP4水平与LVEF值呈负相关，与NT-proBNP呈正相关。即使在校正了传统危险因素，RBP4水平升高仍是心力衰竭患者并发心血管死亡和心衰再入院的独立危险因素。四、RBP4在心肌细胞中同样有稳定表达，且心梗小鼠及细胞模型中RBP4表达呈特异性升高。升高的心肌RBP4表达与细胞焦亡指标呈正相关。过表达RBP4可促进心肌细胞焦亡，沉默RBP4可减轻心肌细胞焦亡。免疫共沉淀证实RBP4可与细胞焦亡关键诱导因子NLRP3结合，沉默NLRP3可减轻RBP4诱导的心肌细胞焦亡，提示RBP4可通过激活NLRP3途径介导的细胞焦亡促进心梗后心肌损伤，提示RBP4可能为急性心肌梗死患者心脏功能障碍的防治提供新靶点。五、新脂肪因子Metrnl水平在冠心病患者有明显降低，且随着冠脉病变严重程度的增加而呈现下降，降低的Metrnl水平是冠心病发病的独立危险因素。六、miR-191可以通过抑制VEZF1相关信号通路，促进内皮细胞凋亡、抑制血管新生，从而加重缺血缺氧诱导的脑损伤。