PPAR-α激动剂上调三磷酸鸟苷环化水解酶1表达、改善同型半胱氨酸诱导的内皮一氧化氮合酶脱偶联机制研究

The activation of AMP-activated protein kinase( AMPK) has been reported to improve endothelial function. Guanosine 5'-triphosphate cyclohydrolase-1 (GTPCH-1) is a key rate limiting enzyme for Tetrahydrobiopterin (BH4).Tetrahydrobiopterin (BH4) is an essential cofactor for NO synthase (NOS). When BH4 levels are inadequate, endothelial NOS (eNOS) is no longer coupled to L-arginine oxidation, which results in ROS rather than NO production, thereby inducing vascular endothelial dysfunction. Our previous study demonstrated that homocysteine (Hcy) decreased the expression of BH4 and eNOS in cultured human endothelial cells. Hcy-induced ROS accelerated the development of atherosclerosis in mice. Furthermore, coronary flow velocity reserve (CFVR) was significantly lower in the HHcy patients. Our previous results show that peroxisome proliferator-activated receptor α (PPAR-α) agonist fenofibrate could recouple eNOS by reversing low-expression of intracellular BH4 in endothelial cells. Moreover, CFVR was significantly improved with PPAR-α agonist fenofibrate treatment in patients. In this study, we suppose that PPAR-α agonist can up-regulate the expression of GTPCH1 and BH4 through the mechanism fo the activation of AMPK, and exert a cardiovascular benefical effction in endothelial cells, hyperhomocysteinemic ApoE-/- mice and hph-1 mice and patients with hyperhomocysteinemia respectively.We investigate whether treatment with the PPAR-α agonist fenofibrate may help protect against atherosclerosis by promoting the re-coupling of eNOS with activated AMPK and increased levels of GTPCH1 and BH4 and normalizing endothelial disorders.

AMP活化的蛋白激酶（AMPK）可通过激活内皮一氧化氮合酶（eNOS）改善内皮功能。四氢生物蝶呤（BH4）是eNOS的辅助因子，三磷酸鸟苷环化水解酶1（GTPCH1）是BH4的限速酶。BH4水平下降可使eNOS脱偶联，导致内皮异常。我们前期工作显示，同型半胱氨酸（Hcy）可抑制内皮BH4水平，及eNOS的磷酸化，损害患者冠状动脉血流储备。过氧化物酶体增殖物激活受体（PPAR）-α激动剂可以上调人内皮细胞GTPCH1水平，增加BH4表达，伴随患者冠脉内皮功能的改善；我们假设在整体水平，PPAR-α激动剂能通过激活AMPK，上调内皮细胞GTPCH1水平，恢复被Hcy抑制的内皮BH4水平、引起eNOS复偶联，改善血管内皮功能。本研究分别在内皮细胞、高Hcy的ApoE-/-小鼠及BH4缺陷hph-1小鼠，探讨PPAR-α激动剂对内皮AMPK活化、GTPCH1表达、氧化应激及eNOS磷酸化的作用。

AMP活化的蛋白激酶（AMPK）可通过激活内皮一氧化氮合酶（eNOS）改善内皮功能。四氢生物蝶呤（BH4）是eNOS的辅助因子，三磷酸鸟苷环化水解酶1（GTPCH1）是BH4的限速酶。BH4水平下降可使eNOS脱偶联，导致内皮功能异常，过氧化物酶体增殖物激活受体（PPAR）-α激动剂非诺贝特具有血管保护功能。本研究阐明高同型半胱氨酸血症参与损害高血压患者冠脉血流储备和冠脉内皮功能，2型糖尿病患者低密度脂蛋白胆固醇水平与冠脉血流储备呈负相关。PPAR-α激动剂非诺贝特改善高甘油三酯血症患者冠脉血流储备和冠脉内皮功能，降低高甘油三酯血症患者血清细胞因子Irisin、RANTES水平，降低高甘油三酯血症患者胰岛β细胞负荷。在离体培养的人脐静脉内皮细胞，PPAR-α激动剂非诺贝特增加内皮细胞GTPCH1表达，增加BH4和NO水平，保护血管内皮细胞功能。并阐明糖尿病治疗药物GLP-1受体激动剂改善初诊2型糖尿病患者血管内皮功能，GLP-1受体激动剂艾塞那肽通过受体-AMPK/AKt-GTPCH1-eNOS -NO信号通路发挥内皮保护作用。二甲双胍通过AMPK-GTPCH1-eNOS信号通路改善高糖诱导的人血管内皮功能失调。本研究项目致力于阐明PPAR-α激动剂非诺贝特等的血管内皮保护作用和机制，具有重要的科学意义和应用价值。