Sirt6经KLF4/PGC-1a 调控内皮细胞线粒体稳态的机制及其在糖尿病性动脉粥样硬化中的作用

The vascular endothelium serves as a key player in the pathogenesis of diabetic atherosclerosis via abnormal mitochondria. The occurrence of sirtuins has been described in damaged-diabetic-endothelium, however the role of sirtuins in endothelial cells mitochondrial homeostasis are still not very clear. We have demonstrated that disrupting Sirt6 has been shown to provide significant disastrous for endothelial damage and carotid plaque development in diabetic patients, and this effect has been shown to be reliant on mitochondrial dysfunction, and over-expression of sirt6 attenuated mitochondrial damage as blocking sirt6 by shRNA substantially stimulated mitochondrial damage in glucose-treated-HUVEC, suggesting that sirt6-mitochondrial homeostasis may be involved in diabetic atherosclerosis. Thus, we hypothesized that sirt6 may be a key regulator of endothelial mitochondrial homeostasis. In this study, we will observe the mitochondrial-protective effect of sirt6 under glucose- treated HUVEC and sirt6-/- or sirt6+/+ HUVEC or endothelium specific sirt6+/+ and sirt6-/- knockout mice or technique, and study other candidate strategy of sirt6, the modulation of E2F1 pathway, the blockage of NF-kB pathway and the amelioration of ITCH pathway, respectively. At the same time, the explosure level of Sirt6/KLF4/PGC-1a was measured in diabetic patients to evaluate its relationship with endothelial dysfunction. Taken together, we will provide a new thesis for studying on the mechanism of endothelial mitochondrial homeostasis, and also provide a novel feasibility treatment target of diabetic atherosclerosis.

糖尿病性动脉粥样硬化(AS) 的始动因素是内皮功能紊乱，内皮功能的维持与Sirtuin家族调控的线粒体稳态密切相关。我们等发现：糖尿病性AS斑块中Sirtuin表达下调，以Sirt6最显著；且Sirt6可维持高糖诱导内皮细胞线粒体稳态；进一步研究发现Sirt6可影响线粒体重要保护因子KLF4/PGC-1a的表达。故假设：Sirt6经KLF4/PGC-1a调控内皮细胞线粒体稳态发挥抗糖尿病性AS的作用。拟通过细胞和动物模型证实Sirt6对高糖诱导内皮细胞线粒体稳态的调控作用；然后对比其它候选途径，明确Sirt6经KLF4/PGC-1a调控线粒体稳态的机制及其在糖尿病性AS中的作用；同时临床水平探讨Sirt6/KLF4/PGC-1a与糖尿病患者内皮功能紊乱的相关性。从而明确Sirt6/KLF4/PGC-1a调控内皮细胞线粒体稳态在糖尿病性AS中的作用及机制，为寻找新的治疗靶点奠定一定的基础。

动脉粥样硬化及其并发症严重威胁现代人的健康，给国家带来巨大的经济损失和沉 重的社会负担。内皮细胞损伤在动脉粥样硬化发生发展中发挥关键性调节作用。Sirt6、KLF4均为重要的内皮细胞保护因子。在前期的研究中我们发现，Sirt6具有重要的启动细胞自噬的作用，提示Sirt6可能通过KLF4调节内皮细胞线粒体稳态。在后续研究中，课题组发现：Sirt6通过启动线粒体自噬阻断高糖/ox-LDL诱导的内皮细胞炎症性死亡；药物及基因下调KLF4，Sirt6介导的线粒体自噬激活及内皮细胞保护作用消失，内皮细胞炎症反应及死亡显著升高；说明Sirt6通过KLF4启动的线粒体自噬具有显著的内皮细胞保护作用。动物研究证实，在糖尿病小鼠中，Sirt6、KLF4基因敲除小鼠血管内膜自噬小体数目显著减少、线粒体结构破坏、数目减少，血管脂质体积增大，说明Sirt/KLF4诱导的线粒体自噬具有抑制糖尿病性动脉粥样硬化形成及进展的作用。在临床研究中，我们证实血浆Sirt6水平降低、应激性血糖升高与ST段抬高型心肌梗死患者罪犯血管血栓负荷相关，并可预测远期不良事件的发生；使用QFR等新型生理学评估软件可评估糖尿病患者罪犯血管PCI治疗效果，指导非罪犯血管的PCI治疗，减少远期不良事件的发生，并证实应激性血糖水平与微循环阻力升高密切升高相关；证实血糖水平升高可预测糖尿病患者动脉粥样硬化的负荷、微循环阻力及远期预后。本研究首次明确了Sirt6激活内皮细胞自噬，抑制动脉粥样发生、发展的作用，并进一步KLF4激活是其主要的分子机制，提出激活Sirt6/KLF4及其诱导的线粒体自噬可作为治疗动脉粥样硬化的靶点 ，具有广阔应用前景。