肾脏代谢反馈调节与盐敏感高血压的形成机制研究

Salt sensitive hypertension had a high incidence rate in clinical experience, and the morbidity tended to be increasing among the youths. This seriously affected the health of the labor force in China. Yet the exact pathogenesis of this disease is not clear. . Through proteomics and metabolomics studies, our results indicated that the mutation of the fumarate hydratase gene leads to the increased level of upstream organic acids in tricarboxylic acid cycle, such as succinate, fumarate, citrate and pyruvic acid in salt sensitive rats. Furthermore, increasing of these organic acids in blood could elevate the blood pressure in salt sensitive rats. . Based on these results, we come up with a new hypothesis: the mutation of fumarase gene in SS rats result in an increasing level of succinate and the expression of its receptor, GPR91. The renal local RAS system is activated by succinate /GPR91 receptor signaling system when the SS rats are fed on a high salt diet. . To confirm this hypothesis, the following problems should be solved: (1) Whether succinate /GPR91 receptor signaling system could be induced by high salt diet. (2) Whether the renal local RAS system was the main reason which triggers the increasing of blood pressure. This work can be conducted by comparing the alteration of blood pressure with or without the inhibitor of GPR91 receptor in the high salt diet. (3) Where did these organic acids come from? The metabolites in kidney of salt sensitive rat could be traced by stable isotope labeling, which will tell us how and where these compounds come from. (4) Which is the main reason causes salt sensitive hypertension, succinate/GPR91 receptor signaling or oxygen free radical /NO balance mechanism. Based on the experimental analysis, the data will help us to understand the relationship between metabolic dysfunction and salt sensitive hypertension. The results from all of the three parts will giving us a final clear answer about the main pathogenesis of salt sensitive hypertension.

盐敏感高血压在临床上具有很高的发病率，且趋于低龄化，严重影响到我国再生劳动力的健康质量，但目前对于盐敏感高血压的形成机制并不十分清楚。申请者对这一机制的蛋白质组学和代谢组学研究发现：盐敏感大鼠富马酸水合酶基因突变导致三羧酸循环中富马酸水合酶上游的琥珀酸、富马酸、柠檬酸及丙酮酸含量增加，而血浆中这些有机酸的增加均可以引起盐敏感大鼠血压升高，因此提出通过抑制剂干预实验，明确高盐饮食是否通过琥珀酸/GPR91受体信号系统激活肾脏局部RAS系统导致血压升高；通过稳定同位素的示踪研究，解析盐敏感大鼠肾脏代谢的物质转化规律以及代谢紊乱和血压升高的关系；通过对盐敏感大鼠肾脏时间动态取样，比较琥珀酸/GPR91受体信号机制和氧自由基/NO平衡机制在盐敏感高血压发病时间进程中的主次和贡献，追踪盐敏感高血压形成的原发机制。通过以上模型动物的基础研究，为临床开展盐敏感高血压的防治提供准确的研究靶点和理论指导。

盐敏感高血压是一种以高盐饮食诱导形成的原发性高血压，其血压盐敏感性即便是在没有高盐饮食诱导的情况下，也会随着衰老逐步演变为高血压。由于其发病率很高，占到自然人群的26%，对其发病的机理的研究尤为迫切。其发病机制既有一定的遗传背景，也有高盐饮食的环境诱导因子，具有环境与遗传背景交互作用的复杂疾病理特征。由于Dahl盐敏感大鼠具有许多和人类盐敏感高血压相类似的生理学特征，如血压的盐敏感性，胰岛素抵抗以及高血脂症，本申请项目以Dahl盐敏感大鼠肾脏代谢作为研究的切入点，对其整体代谢展开研究，以揭示其发病机制。项目通过对肾脏、肝脏、血清以及尿液等代谢组进行全面分析，结合生化以及细胞和转基因动物等多层次的验证，对盐敏感高血压的发病机制的研究获得以下研究成果：（1）富马酸水合酶活性不足是SS大鼠血压盐敏感性的根源。由于富马酸水合酶位于糖、脂、氨基酸物质转化的关键节点，其直接影响是细胞基质中可用于合成门冬氨酸的含量减少，导致内源性精氨酸的水平降低和NO合成减少。尽管很早就已经报道SS大鼠肾脏髓质NO水平较低，补充精氨酸可以降低SS大鼠血压的盐敏感性，但对其产生的根源并不清楚。本项目通过代谢组、细胞以及转基因动物反复验证，证实其根源在于富马酸水合酶活性不足。（2）由于糖氧化障碍，糖代谢的磷酸戊糖旁路途径增强，产生了更多的NADPH，为NADPH氧化酶提供了底物诱导了其活性，使得肾脏糖代谢产生更多的氧自由基。同时，由于氨基酸代谢作为糖代谢的补充，分解代谢增强，导致游离精氨酸、甘氨酸、谷氨酸以及半胱氨酸水平降低，使得NO和GSH的合成不足，细胞抗氧化能力减弱。（3）线粒体结构和功能的损伤促使线粒体ATPase，呼吸链复合物I和III产生更多的氧自由基。肾脏细胞整体氧化还原代谢的失衡是盐敏感高血压形成的根本机制。因此，可以通过补充游离氨基酸和抗氧化治疗获得盐敏感高血压的预防和治疗。