心肌CTRP9基因转录调控机制及其在糖尿病缺血心肌易损性中的作用

CTRP9（C1q/TNF related protein 9）is an newly discovered cardiovascular protective factor. Our previous study found that CTRP9 is high expressed in the heart. CTRP9 knockdown significantly enhanced simulated ischemia/reperfusion injury in H9c2 cells. Cardiac CTRP9 decreased significantly in type 2 diabetic heart and the myocardial ischemia/reperfusion injury exacerbated. Supplement of CTRP9 can decreased the acute myocardial ischemia/reperfusion injury (Basic Res Cardiol, 2012). It implied that decreased CTRP9 may play an important role in the vulnerability of diabetic heart to ischemia. However, the mechanism of CTRP9 gene transcription is still unknown. Our further research found that TNF-α significantly inhibited CTRP9 expression mediated by transcription factor PPARγ inhibition in H9c2 cell. We also identified the binding sites for PPARγ, FoxO3, CREB in the basic activity area of CTRP9 promoter in our pre-experiment. On the basis of the previous study, this project is to investigate the regulation of CTRP9 gene transcription expression in physiologic and diabetes pathologic condition. The aims of the project are 1.to determine whether the transcription factors participate the CTRP9 transcription regulation; 2.to find out whether TNF-α downregulates CTRP9 gene transcription by these transcription factors; 3. to determine whether overexpression or knockdown some special transcription factors can reverse the inhibition of CTRP9 and myocardial I/R injury in type 2 diabetes. So, the clarification of the mechanisms of CTRP9 gene transcription and the decreased CTRP9 gene transcription in diabetic heart is to find out a novel clinical therapeutic strategy and a new target for the treatment of myocardial ischemia/reperfusion injury in type 2 diabetes.

CTRP9是新发现的心血管保护因子。我们前期发现，CTRP9在心肌组织高表达，敲除CTRP9可加重细胞缺氧/复氧损伤；2型糖尿病心肌CTRP9降低，且缺血/再灌注(I/R)心肌损伤加重，补充外源CTRP9可减轻其心肌损伤(Basic Res Cardiol,2012)，提示CTRP9表达下降在糖尿病缺血心肌易损性中的重要作用。然而，CTRP9基因转录调控机制尚不清楚。我们最新实验显示TNF-α通过抑制PPARγ、下调心肌CTRP9，且CTRP9基因启动子区存在PPARγ、FoxO3及CREB等转录因子结合位点。本项目拟在此基础上，探讨上述转录因子是否参与CTRP9基因表达；TNF-α是否通过改变转录因子而下调CTRP9表达；过表达或抑制特定转录因子可否逆转糖尿病CTRP9低表达及I/R心肌损伤。期望通过阐明心肌CTRP9转录调控及其下调机制，为临床防治糖尿病缺血心肌损伤提供新策略和新靶点。

CTRP9是一种新发现的心血管保护因子。我们前期发现，CTRP9在心肌组织高表达，敲除CTRP9可加重细胞缺氧/复氧损伤；2型糖尿病心肌CTRP9降低，且缺血/再灌注(I/R)心肌损伤加重，补充外源CTRP9可减轻其心肌损伤(Basic Res Cardiol,2012)，提示CTRP9表达下降在糖尿病缺血心肌易损性中起重要作用。然而，CTRP9基因转录调控机制尚不清楚。我们探讨了参与CTRP9基因表达的转录因子；TNF-α是否通过改变转录因子而下调CTRP9表达；过表达或抑制特定转录因子可否逆转糖尿病CTRP9低表达。研究结果表明：1.转录因子PPARγ、CREB参与了CTRP9基因的转录调控，而转录因子FoxO3不参与其中；2.TNF-α下调CTRP9基因转录调控，转录因子PPARγ、CREB参与TNF-α对CTRP9基因的转录抑制；3.糖尿病缺血心肌中CTRP9基因转录与表达显著抑制，而PPARγ过表达和CREB siRNA可逆转糖尿病心肌CTRP9的表达抑制，同时减轻糖尿病鼠缺血再灌注心肌损伤。本研究对心肌CTRP9转录调控及其下调机制的阐明，为糖尿病缺血心肌损伤的防治提供了新的治疗靶点。