从SIRT3调控角度研究病理性心肌肥大过程中能量代谢异常机制

Pathological cardiac hypertrophy is a maladaptive response in a variety of organic heart disease (OHD), and it is characterized by mitochondrial dysfunction that resulting from disturbed energy metabolism. Among the NAD(+) -dependent histone deacetylases (Sirtuins) in the mitochondrial, SIRT3 exerts the highest deacetylase activity and eventually regulates energy metabolism by deacetylating a variety of energy metabolism enzymes. Our previous studies have demonstrated significant changes of the enzyme activity and the expression of SIRT3 in the in-vitro model of pathological cardiac hypertrophy. Aslo, knockdown and overexpression of SIRT3 in cultured cardiomyocytes could exacerbate and inhibit the cardiac hypertrophic response, respectively. Based on those results, the objectives of this project are to: (1) study the in-vivo dynamic changes of enzyme activity and the expression of SIRT3 during the transition from compensatory cardiac hypertrophy to heart failure; (2) explore the interaction and regulation between the enzyme activity and expression of SIRT3 and the NAD+ production by studying the dynamic changes of NAD+ , which is the cosubstrate of SIRT3, as well as the role of SIRT3 in modification of NAD+ anabolism enzyme; (3) reveal the upstream signaling molecules that not only regulate SIRT3 gene transcription but also highly associated with cardiac hypertrophy. By studying the regulation of activity and expression of SIRT3 during pathological cardiac hypertrophy both in vitro and in vivo, our project will provide a novel theoretical basis for SITR3 as a new target of treatment in patients with pathological cardiac hypertrophy.

病理性心肌肥大是多种器质性心脏疾病的共同病理变化，线粒体功能障碍导致的能量代谢异常是其重要特征。NAD+依赖性的Ⅲ类组蛋白去乙酰化酶SIRT3是位于线粒体去乙酰化活性最强的SIRTs亚型，通过对多种能量代谢相关酶系去乙酰化修饰调节能量代谢。我们在病理性心肌肥大模型发现SIRT3活性及表达的明显变化，干扰或过表达SIRT3可加剧或抑制心肌肥大反应。本课题拟在此基础上：（1）从整体角度研究从代偿性心肌肥大到心衰过程中SIRT3活性及表达的动态变化过程；（2）通过研究心肌线粒体中SIRT3的限速底物NAD+含量的动态变化以及SIRT3对NAD+合成代谢酶的修饰，探讨SIRT3活性及NAD+生成的交互调控机制；（3）探索影响SIRT3基因转录又与心肌肥大密切相关的上游信号分子。课题主要从SIRT3活性及表达调控角度研究其与病理性心肌肥大的关系，为SIRT3作为病理性心肌肥大干预靶点提供新的理论依据

慢性心力衰竭（CHF）是心血管疾病的主要死因之一，寻找CHF干预和治疗靶点具有重大临床意义。病理性心肌肥大是多种器质性心脏疾病的共同病理变化，CHF的前驱病变，能量代谢异常是其重要病理机制。SIRT3是位于线粒体去乙酰化活性最强的SIRTs亚型，也是细胞能量代谢的感受器，通过对多种能量代谢相关酶系去乙酰化修饰调节能量代谢。1）我们在细胞及分子水平上探讨了SIRT3对心肌细胞肥大的调控作用，发现SIRT3在心肌细胞肥大模型中mRNA、蛋白水平及酶活性均降低，SIRT3-NMNAT3-NAD三者的环路在病理性心肌肥大调控中具有重要作用。2）我们发现SIRT3作为RIP140的下游信号分子，负性影响RIP140对心肌肥大、心肌能量代谢异常、线粒体功能障碍的诱导作用；RIP140可显著抑制SIRT3的表达与酶活性；RIP140对SIRT3的抑制作用依赖于其对ERRα上SIRT3启动子区的抑制。3）探讨了SIRTs其他亚型与心肌肥大等心血管疾病的关系及其机制，包括SIRT1-PKC-zeta、SIRT6-FoxO3-自噬、SIRT6-eNOS、SIRT6-STAT3、SIRT6-NFATc4等信号通路。4）我们近期发现SIRT3基因缺失小鼠（SIRT3-/-）表现出进行性的心肌肥大及自发性心衰，心肌组织芯片筛选发现28周龄出现心衰小鼠心肌组织上调及下调的ncRNA皆较野生型小鼠多10倍以上，提示非编码RNA参与病理性心肌肥大及心衰过程的调节。下一步拟在此基础上：1）对筛选出的对病理性心肌肥大及心衰过程中有明显影响的lncRNA如Plscr4和miRNA如miR-214-3p进行系统研究，明确其对病理性心肌肥大及心衰的调控机制以及与SIRT3的关系；2）研究SIRT3调节能量代谢的机制以及与ncRNA调节的关系，以期发现病理性心肌肥大及心衰新的干预靶点和生物标志物。通过本课题的实施，为SIRT3作为病理性心肌肥大干预靶点提供新的理论依据。