基于miRNA-34a探讨VDR/Pin1轴调控糖尿病心肌细胞衰老研究

Vitamin D has a potential role in the treatment of diabetic cardiomyopathy, while the underlying mechanisms remain elusive. Recent studies suggest that overexpression of cardiac miR-34a from early stages in type-2 diabetic individuals may contribute to the following cardiomyocyte senescence and cardiac remodeling through downregulating its targets, including Bcl2, SIRT1 and PNUTS, consequently leading to the development of diabetic cardiomyopathy. Our pilot works demonstrated that vitamin D attenuated the hyperglycemia-induced upregulation of prolyl isomerase-1 (Pin1) protein expression in a vitamin D receptor (VDR)-dependent manner (i.e., VDR/Pin1 axis), reduced the p66shc-mediated mitochondrial oxidative stress, and improved the diabetic endothelial dysfunction. Additionally, recent evidence has shown that p66Shc-induced microRNA-34a is responsible for the diabetic endothelial senescence and dysfunction. In this study, we aim to explore whether vitamin D can prevent cardiomyocyte senescence and remodeling in vitro and in vivo through activating VDR/Pin1 axis and suppressing miR-34a overexpression, and improve cardiac function. Our study may reveal the underlying mechanisms of the beneficial effects of vitamin D in treating diabetic cardiomyopathy, and provide theoretical basis for this promising therapeutic strategy.

维生素D具有防治糖尿病心肌病（DCM）的潜在作用，但机制不明。近期研究发现，糖尿病患者早期心肌组织miR-34a过表达，后者通过负调节下游靶蛋白Bcl2、SIRT1及PNUTS等的表达，参与调控心肌细胞衰老和重构，可能成为DCM防治新靶点。我们前期研究发现，维生素D通过激活维生素D受体（VDR），抑制高糖环境下Pin1过表达（即VDR/Pin1轴），减轻p66shc介导的线粒体氧化应激，改善糖尿病血管内皮功能。此外，研究显示，高糖通过诱导p66Shc表达上调，增加miR-34a水平，加速内皮细胞衰老和功能障碍。因此，本研究拟在细胞和动物水平，验证维生素D能否通过激活VDR/Pin1轴，抑制miR-34a过表达，延缓糖尿病心肌细胞衰老和重构，改善心功能，并阐明可能机制，为维生素D用于防治DCM提供理论依据。

基础研究提示凋亡可能参与糖尿病心肌病发病且维生素D可能具有防止糖尿病心肌病作用，但具体机制不清。本研究发现，维生素D（骨化三醇）能够改善糖尿病心肌病小鼠心脏收缩功能，减轻心肌纤维化和心肌凋亡，抑制心肌miR-34a表达上调，增加心肌Bcl2蛋白表达水平；此外，维生素D能够抑制高糖培养H9C2细胞凋亡，抑制细胞miR-34a表达上调，增加细胞Bcl2蛋白表达水平；MiR-34a模拟物和抑制物分别拮抗和叠加维生素D对高糖培养H9C2细胞的保护作用；双荧光素酶报告测定证实Bcl2是miR-34a的直接靶标。通过本研究，进一步丰富了糖尿病心肌病的发病机制，为维生素D用于防治糖尿病心肌病提供理论依据，并为将来开展大规模临床研究提供前期基础。