钙敏感受体通过PI3K/Akt通路调控自噬发挥对大鼠糖尿病心肌病的保护作用

Diabetic cardiomyopathy (DCM), a serious DM (Diabetes Mellitus) complication, can be deadly. However, the underlying molecular mechanisms on DCM largely remain unclear. Autophagy is a regulated process in which cellular components are degraded. This process, well conserved in eukaryotic cells, recycle the degraded products for ATP production. Therefore, it is often protective. The extracellular calcium-sensing receptor (CaSR) is a member of the G protein-coupled receptors, whose function is to regulate intracellular Ca2+ homeostasis and cell proliferation and so on. Our team previously found that CaSR involved in cardiac ischemia/reperfusion, apoptosis, myocardial hypertrophy and protective preconditioning. Interestingly, we found that CaSR protein expression of myocardium in diabetic rats was decreased, spermine (an agonist of CaSR) can alleviate the heart injury. We speculated that the activation of CaSR would be protective for DCM through the control of autophagy via PI3K/Akt pathway. To confirm hypothesis, we will determine the effects of CaSR on PI3K/Akt pathway and autophagy in development of DCM in multiple perspectives including organ, cellular and molecular levels. We will also apply CaSR agonist，inhibitor, siRNA in both animal models and cells. This will provide a new insight into molecular mechanisms of DCM in terms of control of CaSR and autophagy and hopefully new targets for the prevention and treatment of DCM.

糖尿病心肌病（DCM）是Ⅱ型糖尿病重要合并症，可导致糖尿病患者死亡，其确切机制不详。自噬是真核细胞通过溶酶体降解自身受损细胞器和大分子物质，实现细胞内再循环的过程，常具有保护作用。钙敏感受体（CaSR）是G蛋白偶联受体，主要参与细胞内钙稳态和细胞增殖等的调节。本课题组曾发现CaSR参与心肌缺血-再灌注损伤、细胞凋亡、心肌肥大和预适应保护。我们前期试验证实，糖尿病大鼠心肌组织CaSR表达降低，给予激动剂可减轻DCM的病变程度。我们推测：CaSR活化可通过PI3K/Akt通路调控自噬而发挥对DCM的保护作用。为证实该假说，本课题拟建立大鼠Ⅱ型糖尿病DCM动物模型和细胞模型，观察DCM不同发展阶段CaSR、自噬和PI3K/Akt通路关键蛋白的表达变化规律，以及CaSR基因沉默、激动剂和抑制剂的影响，揭示CaSR调控自噬参与DCM的分子机制，为临床DCM的干预策略提供新的药物作用靶点。

糖尿病发病率逐年升高，糖尿病心肌病（DCM）是其重要并发症之一，可以引起心衰、猝死，但机制不详。钙敏感受体（CaSR）是G蛋白偶联受体，主要参与细胞内钙稳态和细胞增殖等的调节。国外对CaSR的研究主要集中在甲状旁腺、肾脏等器官，本课题组曾发现CaSR参与心肌缺血-再灌注损伤、细胞凋亡、心肌肥大和预适应保护，但有关糖尿病心肌病中CaSR作用及机制研究较少，尤其是CaSR调控自噬在糖尿病心肌病发生中的作用，国内外尚未见报道。本课题通过建立大鼠2型糖尿病心肌病动物模型和细胞模型，采用激光共聚焦、分子生物学、HE染色和透射电镜、超声心动仪等手段，揭示CaSR调控自噬参与DCM的分子机制。. 本课题首次发现或证实：（1）DCM大鼠心肌组织CaSR表达减少，自噬增强，造成心肌结构损伤和功能障碍，其机制与PI3K/Akt/mTOR信号通路减弱有关。（2）CaSR激活通过上调PI3K/Akt/mTOR信号通路、抑制自噬发挥对DCM的保护作用。（3）精胺可通过上调CaSR-IP3R信号通路及相关钙调控蛋白，部分恢复细胞内钙稳态。这些研究成果从新的视角阐明了DCM发生发展的新机制，为DCM的防治提供一个新思路和新靶点。 . 迄今，我们如期完成了课题，在国内核心期刊已发表署名本课题资助的研究论文 1 篇，有2篇文章正在投稿中。在项目执行期间（2013-2015），课题主持人白淑芝副教授中标黑龙江省教育厅课题 1 项。