组蛋白去甲基化酶KDM3a在糖尿病心脏“代谢记忆”和损伤修复中的作用

Diabetes is an independent risk factor for coronary heart disease. However，intensive blood glucose control could not effectively reduce the risk of cardiovascular events, which was associated with diabetes-mediated ‘metabolic memory’. Previous studies and our preliminary research work found that histone methylation is the main approach to regulate ‘metabolic memory’; in addition, the common modification site locates in H3K9 methylation in cardiovascular system, which was specifically regulated by demethylase KDM3a; furthermore, this process exists widely and persistently in cardiovascular systems. Therefore, our research is mainly focused on 1) examination of the underlying mechanisms with which KDM3a regulated the functions and metabolic memory of vascular smooth muscle cell, vascular endothelial cell and cardiomyocyte; investigation of the superiority of KDM3a for multiple target cells and sites; 2) evaluation of recovery for coronary / microcirculation physiological function and improvement for cardiac function after alteration in H3K9 methylation via KDM3a pathway; clarification of the relationship between KDM3a-mediated H3K9 methylation and metabolic memory in diabetes. This research might be helpful to elucidate the relationship between epigenetics and cardiovascular injury, and might provide novel therapeutic approach for coronary heart disease with diabetes.

糖尿病是冠心病的独立危险因素，然而强化降糖并不能有效降低心血管事件风险，其原因可能与高糖介导的代谢记忆有关。以往研究及我们的前期工作提示组蛋白甲基化修饰是机体调控代谢记忆的主要方式，而心脏代谢记忆的共同修饰位点是组蛋白H3K9，主要受去甲基化酶KDM3a特异性调控，且这一过程广泛而持久。在本项目中，我们拟通过腺病毒转染：1）研究KDM3a对血管平滑肌细胞、血管内皮细胞及心肌细胞功能和代谢记忆的影响及内在机制，探讨KDM3a介导的H3K9甲基化是否在“靶向细胞多样性”和“干预位点广泛性”上更具优势；2）动物水平评价通过KDM3a途径改变H3K9甲基化水平，对冠脉/微循环生理功能的恢复程度和心脏功能的改善情况，阐明KDM3a介导的H3K9甲基化与糖尿病心脏“代谢记忆”的关系。通过本项目实施可进一步阐明表观遗传学与心脏血管损伤修复的作用规律，并为糖尿病合并冠心病患者提供新的治疗策略。

代谢记忆表现为机体血糖恢复到正常水平后持续心脏损伤，而既往研究提示组蛋白H3K9me2特异性去甲基化酶KDM3A可能参与糖尿病血管持续重构，所以在阐明糖尿病或高糖心肌“代谢记忆”损伤具体表现的基础上，我们进一步探讨“KDM3A-H3K9me2 途径”在其中发挥的关键作用，并对可能的分子机制进行了研究。我们首先在动物水平和细胞水平分别验证了糖尿病诱导代谢记忆损伤表现为心脏功能紊乱、ROS、凋亡与炎症反应等仍继续存在，其次构建KDM3A基因敲除大鼠，在动物水平进一步验证KDM3A敲除抑制了该损伤的持续恶化。应用腺病毒载体上调或下调KDM3A表达，建立高糖心肌细胞“代谢记忆”模型，在细胞水平验证了抑制KDM3A表达可以减轻“代谢记忆”损伤进展，而高表达KDM3A则加剧该病理过程。通过对相关机制的研究我们发现，KDM3A主要通过促进NF-κB/P65表达与转录活性诱导糖尿病或高糖心肌“代谢记忆”损伤发生，应用siRNA抑制P65则能逆转KDM3A高表达所致的“代谢记忆”损伤加重。综上所述，本研究阐明了糖尿病心肌“代谢记忆” 损伤主要表现为心脏结构与功能、心肌病理生理（炎症、凋亡与 ROS 反应） 等层面的广泛持续恶化。通过抑制“KDM3A-H3K9me2 途径”能够减缓糖尿病心肌“代谢记忆” 损伤进展，其机制主要通过下调NF-κB/P65 表达与转录活性来发挥心肌保护功能。这也为临床防治糖尿病心肌“代谢记忆”损伤提供了新靶点。