FoxO1负性调控线粒体自噬在糖尿病心肌对缺血后处理失敏感中的作用机制

Diabetic subjects are more vulnerable to myocardial ischemia reperfusion injury (IRI), but less or not responsive to therapeutic interventions, such as ischemic postconditioning (IPostC). Although the mechanisms governing the increased vulnerability of the diabetic heart to IR injury remains unclear, mitophagy dysfunction has been recently suggested to play a key role in its pathology. FoxO1 is a recently identified regulator, which plays an important role in regulating cardiac metabolism and autophagy. In the preliminary study, we found cardiac nuclear FoxO1 was progressively and persistently activated in diabetic rodents, which was accompanied with progressive cardiac dysfunction and increased myocardial susceptibility to IR injury. We further found that inhibition of FoxO1 activation attenuated hypoxia/reoxytgenation injury and restored the sensitivity to hypoxic postconditioning in isolated cardiomyocytes in the condition of high glucose and high fat. Therefore, we hypothesize that excessive activation of FoxO1 induced mitophagy dysfunction plays an important role in decreased tolerance to IRI and loss of sensitivity to IPostC in diabetic heart. In the current proposal, we will use type 2 diabetic rats, primary myocardial cells and H9C2 cells as the research subjects, to investigate the roles and mechanisms of FoxO1 negatively regulating mitophagy in the decreased tolerance to IRI and loss of sensitivity to IPostC in diabetic heart, and investigate the role of related signal pathway such asAMPK/Akt/TSC/mTOR in ischemic heart. This proposed studies will improve our understanding of diabetic myocardial IRI and may help facilitate the development of novel and optimal therapies in diabetic and ischemic heart disease.

糖尿病心脏更易遭受缺血再灌注损伤(IRI)，且对缺血后处理(IPostC)的敏感性降低，研究发现其与线粒体自噬功能紊乱有关，但其调控机制不明。新近研究表明FoxO1是心肌代谢及自噬的重要调节因子。我们预实验表明，糖尿病进程中心肌细胞核FoxO1表达持续增高，伴随心肌功能及心脏对IRI耐受性持续下降；进一步研究发现抑制FoxO1过度活化可减轻高糖高脂条件下缺氧复氧所致的心肌细胞损伤及恢复其对缺氧后处理的敏感性并伴随自噬降低。据此，我们推测糖尿病心肌FoxO1过度活化所致的线粒体自噬功能紊乱是导致糖尿病心肌对IRI耐受性降低及对IPostC不敏感的重要机制。本项目将在大鼠与心肌细胞模型上探讨FoxO1负性调控线粒体自噬在糖尿病心脏对IRI耐受性降低及对IPostC不敏感中的作用机制，并观察其对自噬相关信号通路AMPK/Akt/TSC/mTOR的影响机制，为开发糖尿病心肌IRI药物提供实验依据。

缺血性心脏病是导致糖尿病患者死亡的重要原因。糖尿病心肌较非糖尿病心肌更不易耐受缺血再灌注损伤（ischemia reperfusion injury， IRI），且对缺血后处理的敏感性降低，研究发现其与线粒体自噬功能紊乱有关，然而其相关调控机制尚未阐明。FoxO1是调控心肌代谢及自噬的重要因子。本项目旨在探讨“糖尿病心肌FoxO1过度活化所致的线粒体自噬功能紊乱是导致糖尿病心肌对IRI耐受性降低及对缺血后处理不敏感的重要机制”这一中心假说。本课题分别在糖尿病大鼠心肌IRI模型及原代心肌细胞与H9C2细胞模拟的高糖与缺氧复氧模型上进行了相关机制探索。我们研究发现：糖尿病鼠病理进程中心肌细胞FoxO1表达水平及活性逐渐升高，而线粒体自噬功能功能紊乱，两者参与了糖尿病心血管并发症的发展； FoxO1调控的线粒体自噬与AMPK/Akt/TSC/mTOR信号通路密切相关，有效调控线粒体自噬是抑制糖尿病缺血性心脏病及改善糖尿病心肌对缺血后处理敏感性的关键途径。本项目的完成不仅有助于完善糖尿病心肌IRI及缺血后处理的分子机制，而且为治疗和逆转糖尿病性缺血性心脏病提供早期预防和治疗策略，以及为临床开发糖尿病心肌IRI保护药物或措施提供潜在的作用靶点。