肾脏氨基酸代谢异常与盐敏感高血压形成机制的研究

The incidence of hypertension has been rising rapidly in China during the past ten years. However, 50% of the hypertensive population exhibits salt sensitivity of blood pressure. Hypertension has been also the key risk factors for stroke, heart attack, heart failure, and arterial aneurysm, so it is extremely important to understand the mechanism of development of salt sensitive hypertension.. Our previous research data showed that the abnormal metabolism in Dahl SS rats was characterized by reduced glycolysis and TCA cycle; enhanced fatty acid synthesis and gluconeogenesis; the rate of ATP production in mitochondria was decreased significantly. We also demonstrated that the amino acids catabolism in kidney of SS rats was enhanced, as the activities of alanine aminotransferase (ALT), aspartate aminotransferase (AST), and glutamate dehydrogenase (GLDH) in the kidney increased significantly, and the free amino acids in kidney were insufficient compared with SS.13BN. . Based on the published research results and the data in our lab, the current proposal will give a new hypothesis about the mechanism of development of salt sensitive hypertension as following: (1) Free amino acids from protein hydrolysis should mainly undergo transamination, and carbon skeleton should be used for oxidation and energy production. It suggestes that amino acid catabolism possibly compensate the efficiency of sugar and lipid oxidation, which should cause the free amino acids to be consumed in renal tissue; (2) SS rats need more phosphocreatine to reserve the energy for quick regeneration of ATP during intense kidney activity and to compensate the insufficient ATP synthesis rate in the mitochondria. It will consume a large number of glycine, methionine and arginine for the synthesis of excessive phosphocreatine in kidney and liver. The excessive consumption will lead to amino acid metabolism imbalance. This contains the synthesis of NO and GSH will decrease as the insufficient content of arginine, glycine, and methionine in tissue. The production of reactive oxygen species will increase, however, the high salt diet exacerbates the metabolic process and promote the occurrence of salt sensitive hypertension in Dahl SS rats.. The purpose of the current proposal will dissect the amino acids metabolic mechanism of salt sensitive hypertension and try to design a free amino acids formula which can inhibit the development of salt sensitive hypertension. Of course, we also hope the formula could be utilized in the clinical for the treatment of salt sensitive hypertension in the future.

近年，我国高血压的发病率呈现快速上升的趋势，盐敏感高血压依然是影响我国居民健康的大问题。申请者围绕盐敏感高血压所展开的代谢组学研究发现：盐敏感大鼠糖酵解和TCA的物质转化能力下降，肾脏线粒体ATP的生成速率不足，氨基酸分解代谢增强，肝、肾、血和尿液中肌酐、尿素的含量异常升高。由此对盐敏感高血压的发病机制提出新的理论假设：氨基酸的水解氧化补偿了能量代谢的不足，导致组织中游离氨基酸含量减少；磷酸肌酸的大量合成消耗了甘氨酸、蛋氨酸和精氨酸，以弥补ATP生成速率的不足，并进一步导致氨基酸代谢异常；精氨酸不足引起了NO合成减少；甘氨酸和半胱氨酸的不足减少了GSH的合成，使得SS大鼠肾脏组织总体氧自由基增加；高盐饮食又加剧了这一代谢过程，促进了SS大鼠盐敏感高血压的发生。项目计划在以上机理研究的基础上设计出能够抑制盐敏感高血压发生的氨基酸溶液，为今后在人群中开展盐敏感高血压的预防和治疗提供理论依据。

本申请项目以Dahl盐敏感大鼠肾脏代谢作为研究对象，对其肾脏氨基酸代谢展开研究，以揭示氨基酸代谢在盐敏感高血压发病中的作用。项目通过对肾脏、肝脏、血清以及尿液等代谢组进行系统全面的分析，结合生化以及细胞等多层次的验证，对氨基酸代谢促成盐敏感高血压的发病机制的研究获得以下研究成果：（1）细胞中游离氨基酸的不足导致①电子传递链复合物蛋白I和III亚基缺失，是导致线粒体大量产生氧自由基的主要原因。②和氧自由基清除有关的SOD,CAT酶的表达量和活力均显著降低，氧自由基的清除效率降低。③GSH的合成减少，降低了底物水平抗氧化的能力。氧化还原代谢失衡是盐敏感高血压发病的主要机制这一。（2）能量需求增加是高盐饮食后的第一响应信号，糖、脂分解的缺陷加剧了氨基酸的分解代谢。这包括脱氨基作用后的短链脂肪酸和有机酸参与分解氧化和肾脏GAA的大量合成。游离氨基酸的不足进一步加剧能量供给关键酶的合成障碍，促进了氧自由基的产生。游离氨基酸的不足，特别是肾脏内源性Arg的合成不足导致NO合成减少，氧自由基和NO的代谢失衡是盐敏感高血压形成的主要机制。（3）通过门冬氨酸干预实验、瓜氨酸干预、组氨酸干预、甘氨酸干预、支链氨基酸氨基酸干预以及beta 氨基乙丁酸干预证实外源补充氨基酸都可以显著降低高盐饮食引起的血压升高，可以降低肾脏氧自由基的产生，增加抗氧化酶的活性，增加NO的有效性。（4）设计了一组复合氨基酸补充剂，其可以改善SS大鼠整体的代谢均衡。这包括氧自由基代谢，NO代谢以及能量代谢。代谢均衡的修正是复合氨基酸能够预防和抑制盐敏感高血压的根本机制。复合氨基酸制剂的干预结果也提示我们在临床实践中，可以通过饮食调节，补充关键氨基酸以达到预防和治疗盐敏感高血压的目的。