内皮线粒体失稳态致血管胰岛素抵抗促发肥胖相关高血压及其机制

The incidence of hypertension shows a 2-4-fold increase in obesity, but the underlying mechanism is unclear. We previously found that vascular insulin resistance (VIR) is closely linked to hypertension in patients with obesity, and VIR is a major cause in the development of hypertension (Hypertension 2013). We recently found that mice with obesity and hypertension showed increased mitochondrial fission together with reduced Sirt3 expression and decreased flexibility of mitochondrial membrane potential (△Ψm). In addition, Sirt3 deficiency induced VIR. These data suggest that disrupted endothelium mitochondrial homeostasis is associated with VIR and hypertension in obesity. This study is designed to explore the role of vascular endothelial mitochondrial homeostasis in the development of VIR and hypertension in obesity. The relationship among endothelial mitochondrial homeostasis, VIR and blood pressure will be explored in obese patients and in high-fat diet-fed mice and ob/ob mice, respectively. The underlying mechanism of endothelium mitochondria in regulation of VIR and blood pressure will be investigated using endothelium-specific insulin receptor knockout and mitochondrial Sirt3 knockout mice and interventions with mitochondrial key factors, such as △Ψm. Finally, a mice model of aerobic exercise which has been shown to ameliorate insulin resistance will be used to further confirm the possible role of endothelial mitochondria in obesity-related vascular insulin sensitivity and hypertension. This study will focus on elucidating a possible novel role of disrupted endothelial mitochondria homeostasis in obesity-induced VIR and its mechanism of action in obesity-related hypertension.

肥胖人群高血压发病率是非肥胖者的2-4倍，但机制不清。我们前期发现肥胖患者是否存在血管胰岛素抵抗（VIR）是其是否伴发高血压的重要分界指征，且VIR是高血压发生的机制之一（Hypertension 2013）。新近发现，肥胖伴高血压小鼠舒血管功能降低，且内皮线粒体分裂增加、Sirt3表达和膜电位（△Ψm）反应性降低，提示内皮线粒体失稳态与肥胖相关高血压相关，但具体机制不明。本研究拟①分别在肥胖患者和高脂喂养及基因肥胖鼠明确肥胖（伴或不伴高血压）内皮线粒体的变化及其与VIR的相关性；②采用血管内皮胰岛素受体及Sirt3特异敲除小鼠等模式动物及△Ψm关键靶点干预等方法探讨内皮线粒体改变在VIR中的作用及机制；③进一步通过有氧运动改善肥胖鼠VIR同时观察内皮线粒体的改变，反证并明确内皮线粒体在VIR及肥胖相关高血压中的作用。本研究可望揭示内皮线粒体在肥胖相关血管功能障碍及高血压发生中的新机制。

线粒体是细胞内氧化磷酸化和ATP合成的主要场所，其生成-降解、合成-分裂、氧化-还原及相关理化性质在生理状态下处于动态平衡，进而维持线粒体稳态。与平滑肌细胞和心肌细胞相比，血管内皮细胞中线粒体的含量较少，只占细胞容积的2-6%，且内皮细胞线粒体也不是ROS产生的主要来源。新近研究发现，血管平滑肌细胞的线粒体分裂参与调节血管收缩，但内皮细胞线粒体稳态对血管功能和血压稳态具有怎样的意义尚不清楚。本课题采用SIRT3KO、Mypt1SMKO等模式动物和线粒体稳态关键靶点干预等方法，在线粒体、细胞、动物和人体层面着重研究肥胖相关高血压状态下血管内皮细胞线粒体稳态的改变并明确内皮细胞线粒体稳态变化对血管功能的影响、机制及其在高血压发生发展中的作用。结果发现：①肥胖伴或不伴高血压患者及肥胖、高血压模型小鼠血管胰岛素敏感性降低、内皮SIRT3表达下调且线粒体分裂增加；②血管内皮SIRT3表达降低可通过阻滞自噬增加线粒体ROS水平，进而降低肥胖小鼠模型中的血管内皮胰岛素敏感性并促发高血压；③Drp1介导的内皮线粒体分裂增加促发高血压状态下的血管功能障碍，而抑制Drp1可改善内皮线粒体稳态，进而改善血管内皮功能并降低血压；④葡萄糖氧化引起的血管平滑肌细胞线粒体超极化介导血管收缩，其机制与肌球蛋白磷酸酶失活有关；⑤长期有氧运动可改善SHR血管内皮线粒体稳态，改善内皮功能，进而延缓高血压发生发展，其机制与运动抑制血管Drp1，从而改善线粒体功能，降低血管ROS水平有关。此外，我们还发明了一种新的通过多普勒超声评估大鼠主动脉脉搏波传导速度，进而评估血管僵硬度的方法。本课题揭示了内皮细胞线粒体稳态在肥胖及高血压相关血管功能障碍中的作用，提示SIRT3及Drp1有望成为防治肥胖相关高血压及相关血管功能障碍的一个新的干预靶点。