PDE4调控的心脏成纤维细胞miR-1应答高胰岛素血症在糖尿病心肌纤维化中的作用机制及干预研究

Diabetes is an independent risk factor of heart failure. The interstitial fibrosis of the myocardium exists even in mild diabetes mellitus but the underlying mechanism remains unknown. Our previous study shows that the expression of phosphodiesterase PDE4 is elevated in human hearts with DM and in diabetes mouse hearts. Inhibition of β2AR attenuated PDE4 expression and cardiac fibrosis. In our preliminary study, insulin induced PDE4 expression and fibrosis in β2AR dependent manner in fibroblast, whereas the miR-1 expression is inhibited. Pharmacological inhibition of PDE4 significantly attenuated insulin induced inhibition of miR-1 expression and diabetes related cardiac fibrosis. The cAMP response element binding protein (CREB) is a transcription activator for the miR-1 gene, which negatively regulates the expression of extracellular matrix protein. Based on these observations, we hypothesize that chronic insulin treatment selectively induces PDE4 expression in β2AR dependent manner in cardiac fibroblast leading to reduced intracellular cAMP accumulation and impaired CREB mediated miR-1 transcription, and increased cardiac fibrosis. We will test this hypothesis through a combination of physiological, biochemical and genetic approaches and attempt to identify the signaling cascades involved, and to decipher the mechanisms by which insulin attenuates miR-1 signaling in the cardiac fibroblast. This project highlights a novel and important pathophysiological role of hyperinsulinemia in the development of diabetic cardiac fibrosis that may lead to the discovery of potential new therapeutic targets for intervention.

糖尿病是心衰发病独立危险因素，早期即出现心肌纤维化但机制不明。糖尿病心脏病患者心肌磷酸二酯酶PDE4表达增加，抑制β2肾上腺素受体(β2AR)可降低糖尿病小鼠心脏PDE4表达，改善心肌纤维化。我们发现在成纤维细胞胰岛素以β2AR依赖方式促PDE4表达及纤维化，而 microRNA-1 (miR-1)表达下降，PDE4抑制剂逆转胰岛素促纤维化及抑制miR-1表达作用，并改善糖尿病小鼠心肌纤维化和心脏miR-1表达。cAMP激活的cAMP反应元件蛋白（CREB）可促进miR-1转录，而miR-1负性调控细胞外基质蛋白表达，推测胰岛素通过诱导心脏成纤维细胞PDE4表达降解cAMP而抑制CREB激活，致miR-1表达下降促细胞外基质合成及心肌纤维化。本项目拟阐明高胰岛素血症通过PDE4调控miR-1参与2型糖尿病心肌纤维化的作用机制，为临床合理应用胰岛素防治糖尿病心肌纤维化及开发新靶点提供新策略。

糖尿病是心衰发病独立危险因素。2型糖尿病合并心力衰竭的发病率和死亡率是非糖尿病患者的4～8倍。糖尿病患者早期即出现心肌纤维化，但机制不明。本项目研究发现糖尿病心脏病患者心脏磷酸二酯酶PDE4表达增加。胰岛素促进心肌PDE4D表达增加，并激活TGF-β1信号通路，抑制mir-1表达，促进纤维化。本项目研究表明PDE4抑制剂对糖尿病小鼠的糖代谢紊乱和心肌纤维化具有改善作用，并调控心脏组织mir-1表达；在心脏特异敲低PDE4D对糖尿病小鼠的血糖水平无影响，但可改善心脏功能、心脏纤维化以及心脏组织mir-1表达，确定心脏组织PDE4D对糖尿病心功能不全的改善作用。进一步观察到心脏特异表达mir-1对高脂饮食糖尿病小鼠心功能和心脏重构的改善作用，提示mir-1参与PDE4D在糖尿病心脏功能不全的发病机制。本项目明确胰岛素血症通过PDE4调控miR-1参与2型糖尿病心肌纤维化的作用机制，为临床合理应用胰岛素防治糖尿病心肌纤维化以及开发新靶点提供新策略。