转录共激活因子Yap/Taz活化导致糖尿病心肌损伤的分子机制研究

The diabetes is the number one health challenge in China. The people with diabetes are 2 to 4 times more likely to have heart disease than people without diabetes. However, the mechanisms by which diabetes results in cardiac dysfunction still remains to be determined. Yap (yes-associated protein), and its paralog PDZ-binding motif (Taz), are two essential downstream effectors of the Hippo signaling. Emerging evidence has shown that Yap/Taz misregulation plays critical roles in atherosclerosis, cardiac hypertrophy and myocardial infarction. A more recent study revealed that Yap/Taz activity was controlled by metabolic and nutrient-sensing pathways. The serum starvation and glucose starvation inhibited the Yap/Taz activity. Our preliminary data showed that high glucose upregulated the Yap/Taz expression and activated their translocation in primary cultured neonatal cardiomyocytes. We also found the Yap/Taz and their binding partner Tead1 and their downstream target ANKRD1 were upregulated in the heart of STZ-induced type 1 diabetic mice. Because the tead1 activity and ANKRD1 expression are upregulated during cardiac hypertrophy, these indicated that the Yap/Taz played important roles in high glucose induced hypertrophy. We further found that in the heart of diabetic model, Yap/Taz interacted with p73 who is critical to transactivation of apoptotic target genes. Based on these findings, we hypothesize that Yap/Taz overactivation induced by diabetic condition may result in cardiac hypertrophy and cell apoptosis and lead to cardiac dysfunction...Emerging evidence has shown the canonical Wnt/β-catenin signaling pathway is associated with metabolic disorders of diabetes. Our previous study found that the over activation of β-catenin is involved in the development of diabetic cardiomyopathy. However, the precise mechanisms by which β-catenin activation is mediated remains to be clarified. Our preliminary data showed that both of Yap/Taz and active-β-catenin were upregulated in the heart of type1 diabetic mice and high glucose treated-cardiomyocytes. Overexpression of Yap/Taz induced by the adenovirus containing Yap/Taz wild type increased the active-β-catenin expression. These data indicated that β-catenin was activated by Yap/Taz in diabetic heart. Based on these novel and exciting findings, we hypothesize that Yap/Taz activation is directly involved in cardiac hypertrophy and cell apoptosis of diabetic cardiomyopathy; Activation of β-catenin induced by Yap/Taz accelerates diabetic cardiac dysfunction, and finally lead to heart failure. The completion of the proposed study will provide new effective ways to prevent as well as treat cardiac dysfunction in patient with diabetes.

糖尿病心肌病是导致糖尿病患者死亡的重要原因，目前尚无有效的治疗方法。β-catenin是经典Wnt信号通路的核心蛋白，前期研究发现它的持续活化导致糖尿病心功能障碍。已有的资料显示转录共激活因子Yap/Taz与Wnt/β-catenin通路存在交互作用。我们预实验发现糖尿病代谢环境能诱导Yap/Taz活化、入核，并与调控心肌肥大、细胞凋亡的核转录因子结合；进一步预实验发现高糖环境下Yap/Taz活化能调控心脏β-catenin活性。由此推测，Yap/Taz活化与糖尿病心脏结构和功能损伤关系密切，抑制Yap/Taz能够保护糖尿病受损的心脏功能。本项目重点研究Yap/Taz在糖尿病心肌病中的作用和核内调控机制；探讨心脏Yap/Taz与β-catenin的内在关系；深入研究Yap/Taz激活β-catenin在糖尿病心肌损伤中的作用和具体机制，为糖尿病心肌病防治提供新的分子靶标。

我国糖尿病和准糖尿病人已超过2亿。糖尿病心肌病是糖尿病人常见和重要的死亡原因但机制未明。Yap是Hippo通路关键效应分子，其调控紊乱与动脉粥样硬化、心肌肥厚、心力衰竭关系密切。前期的研究显示机体代谢环境能影响Yap表达、活性。鉴于此，本项目围绕“Yap活化导致糖尿病心肌病”的关键科学问题，利用1型、2型糖尿病小鼠、高糖处理的乳鼠心肌细胞，以心脏功能变化、心肌肥大为主要观察指标，明确持续的高糖环境能直接激活Yap通路；随后利用成年期心肌特异性敲除Yap的糖尿病小鼠、腺相关病毒调控心脏Yap表达的糖尿病小鼠，明确Yap活化直接诱导糖尿病心肌肥大；进一步利用高通量RNA-Seq、免疫沉淀耦联质谱分析技术等筛选和验证，首次发现Yap能通过抑制Sirt1的表达诱导糖尿病心肌肥大；其分子机制可能与转录因子Hic1等有关。此外，还创新性发现单酚萜类化合物香芹酚、碳酸酐酶抑制剂醋甲唑胺对糖尿病心肌病的保护作用和分子机制。本项目提出Yap通过抑制Sirt1表达导致糖尿病心肌病的新机制；本研究的系列发现为临床防治糖尿病心肌病提供新的分子靶标，并为筛选新的治疗药物或老药新用提供重要的实验依据。部分研究结果已发表于Diabetes，Frontiers in pharmacology等杂志，并获得1项国家发明专利授权。