强制能量限制调控AMPK/NCX1通路拮抗糖尿病心肌病的机制

Diabetic cardiomyopathy is one of the important complications of diabetes mellitus，and mitochondrial dysfunction plays a key role in in its pathogenesis. It was reported that Na+/Ca2+ exchanger 1 (NCX1), localizing in mitochondrial inner membrane, maintains a normal cardiomyocyte mitochondrial respiration function through modulation of cardiac Ca2+ homeostasis. However, the mechanism of the effect of diabetes on NCX1 expression is still unclear. Our previous work showed that high glucose induced increased cytoplasmic and mitochondrial Ca2+ influx in cardiac myocytes, and significantly decreased the expression of NCX1 in cardiac myocytes of diabetic rats, accompanied with cardiomyocyte mitochondrial dysfunction. We used metabolic surgery as a tool to confirm that the activity of energy sensor AMPK in myocardial tissue increased after compulsory energy restriction, accompanied by the up-regulation of NCX1 expression, and significantly reversed the myocardial mitochondrial respiratory dysfunction caused by diabetes mellitus, and improved myocardial structural damage and diastolic dysfunction. Nevertheless, how energy restriction regulates the AMPK/NCX1 pathway, corrects the imbalance of Ca2+ homeostasis in myocardial mitochondria, and thus improve the respiratory function of mitochondria still needs determined. Thus, we propose a theoretical hypothesis that NCX1 is an important regulator of mitochondrial Ca2+ homeostasis, and that the dysfunction of NCX1 in diabetes can cause the imbalance of mitochondrial Ca2+ homeostasis and lead to cardiac damage. The present study will further clarify the mechanism of compulsory energy restriction regulating AMPK/NCX1 pathway antagonizing diabetic cardiomyopathy.

糖尿病心肌病是糖尿病的重要并发症，线粒体功能障碍在其发病过程中起关键作用。线粒体内膜钠钙交换子NCX1通过调节线粒体钙稳态维持正常的线粒体呼吸功能，但糖尿病对NCX1影响的机制尚不清楚。我们前期工作显示，高糖诱导心肌细胞胞浆及线粒体钙内流增加，且糖尿病大鼠心肌组织中NCX1表达显著下调，伴随线粒体呼吸功能异常。我们以代谢手术作为干预工具证实，强制能量限制后心肌能量感受器AMPK活性增加，伴随NCX1表达上调，且显著逆转糖尿病引起的心肌线粒体呼吸功能障碍，改善心肌结构及功能损害。但能量限制如何调控AMPK/NCX1通路，纠正线粒体钙稳态失衡，从而改善线粒体呼吸功能的机制尚不清楚。为此，我们提出理论假设：NCX1是维持心脏线粒体钙稳态的重要调节因子，糖尿病可损害NCX1，使心肌线粒体钙稳态失衡，导致心脏病变。本研究将揭示强制能量限制调控AMPK/NCX1通路拮抗糖尿病心肌病的机制。

糖尿病心肌病是糖尿病的重要并发症，线粒体功能障碍在其发病过程中起关键作用。线粒体内膜钠钙交换子NCX1通过调节线粒体钙稳态维持正常的线粒体呼吸功能，但糖尿病对NCX1影响的机制尚不清楚。本项目以代谢手术作为强制能量限制干预手段，针对其是否可以逆转糖尿病的心脏损害进行了研究，并探索了其分子机制。在本项目中，我们通过链脲佐菌素（STZ）造成高血糖模型，通过超声心动图确定其形成糖尿病心肌病典型症状后接受代谢手术治疗。我们发现代谢手术后动物的心脏舒张功能障碍得到显著改善，心肌AMPK活性上调，同时逆转了高血糖所致的线粒体功能损害。细胞实验证实，高糖引起线粒体钙超载，进而影响线粒体功能，AMPK激动剂干预可以拮抗高糖导致的线粒体损害。通过心肌特异性敲除AMPK后，代谢手术的心脏获益消失。通过蛋白质组学筛查手段，我们发现代谢手术后心肌线粒体相关蛋白变化最为显著，而且代谢手术逆转了高糖导致的NCX1蛋白的下调，其表达下调可能是细胞线粒体钙超载的关键因素。我们发现抑制NCX1的功能造成AMPK激活后的线粒体功能改善消失。而且特异性敲除心肌的NCX1几乎完全阻断了糖尿病时代谢手术的心肌获益。同时，我们注意到代谢手术后NAD+从头合成途径激活，心肌组织内NAD+含量增加，包括Sirt1在内的Sirt家族表达上调。阻断NAD+的合成后代谢手术的心脏获益消失，而补充NAD+的前体物质可以显著改善糖尿病心肌病。我们的研究结果提示，在整体能量状态改变时，存在AMPK/NAD+/Sirt/NCX1调控通路，通过介导线粒体钙稳态而调节线粒体功能，进而调整心肌细胞功能。我们的研究表明整体能量状态的控制是一个有前景的改善心脏功能受损的预防和治疗措施。

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