冷刺激诱发的脂肪代谢改变影响动脉粥样硬化进程的机制研究

Acute cardiovascular events incidence was significantly increased in the cold environment，meanwhile the adipose tissue especially the BAT also experience great metabolic changes under cold stress. Our preliminary results showed that cold stress could quickly acitivate BAT, and convert WAT into BRITE, significantly aggravate development of atherosclerosis, and promote the plaque growth, all these imply that the metabolic change of adipose tissue induced by cold stress may participate in the development of atherosclerosis. Therefore further mechanistic study of how cold-induced metabolic changes of adipose tissue aggravate the development of atherosclerosis is urgently needed, the essential scientific question here is to find a proper target to manipulate this regulatory pathway and ameliorate atherosclerotic leision. According to our former study and some recent researchs, we choose the newly discovered metabolic regulator FGF21 as the study target. The present study uses apoE-/- mice and apoE-/-/UCP1-/-mice with cold stimulation model to study if cold impact the experession level of FGF21, the influence of FGF21 on adipose tissue and atherosclerosis, in attempt to confirm the effects and clarify the possible mechanism of FGF21 induced activation of BAT and the WAT-BRITE conversion on the progress of AS and its plauqe stability. Then we delete the UCP1 gene from the apoE-/- mice to find out exact which kind of role the UCP1 plays in this study. This project will provide further understanding of the effects and molecular mechanism between cold-induced-metabolic changes of adipose tissue and atherosclerosis, offer novel therapeutic targets for atherosclerosis related diseases.

寒冷环境中急性心血管事件发生率显著增加，而脂肪代谢在冷刺激下发生显著变化。我们的前期研究结果发现，冷刺激可以迅速活化BAT，将WAT转变为BRITE，显著加剧AS进程，证实冷刺激通过改变脂肪组织代谢状态而显著影响AS进程。因此进一步研究冷刺激是如何改变脂肪组织代谢状态，是否可通过调控其中某些环节而改善AS病变成为重要的科学问题。本项目结合文献报道和前期研究结果，选取新发现的代谢调节因子FGF21作为研究靶点。使用apoE-/-小鼠和apoE-/-/UCP1-/-小鼠构建的冷刺激模型，研究FGF21对脂肪组织和AS斑块的影响；FGF21是否参与冷刺激诱导的脂肪组织代谢而影响AS进程；FGF21对脂肪组织和AS进程的影响是否依赖于UCP1；及其具体机制。本课题的实施将进一步阐明冷刺激诱导的脂肪代谢改变与AS间的作用以及其发生机制，为AS相关疾病提供新的防治靶点。

近年来许多研究揭示FGF家族的新成员，成纤维细胞生长因子21（FGF21）可以通过多种途径参与糖脂代谢的调节，而FGF21对动脉粥样硬化的具体作用及其机制却尚未明确。本课题分析了正常志愿者及冠心病患者血浆FGF21水平，结果表明急性冠脉综合征患者具有较高水平的FGF21，并与AS病变程度有一定相关性。因此我们进一步研究了应用apoE-/-敲基因小鼠、apoE&UCP1双基因敲除小鼠及体外培养的脂肪细胞，探索了FGF21在脂肪组织代谢及动脉粥样硬化中的作用及其调控机制。体内实验结果显示，冷刺激明显增加脂肪组织和肝脏组织中FGF21的mRNA及蛋白表达水平； 冷刺激明显增加小鼠脂肪组织中FGF21相关受体FGFR1c和 β-klotho的mRNA和蛋白表达水平。本课题利用渗透性微量泵置入术，发现外源性增加FGF21可降低小鼠体重、增加NST能力并明显促进小鼠白色脂肪组织的棕色化及脂降解速率，证实FGF21可促进BAT的活化及WAT的棕色化；并明显改善apoE-/-小鼠LDL-C水平尤其是VLDL-C水平，降低主动脉斑块大小及斑块的稳定性，改善动脉粥样硬化斑块的炎性因子表达水平。证实外源性增加FGF21水平可改变脂肪组织的代谢状态进而延缓动脉粥样硬化进程及斑块的不稳定性及炎症反应。体外实验结果显示，将分离制备apoE-/-小鼠的脂肪基质血管组分（SVF）细胞，成功诱导为成熟脂肪细胞，证实FGF21可通过AMPK-SIRT1信号通路作用于PPARγ/PGC1-α，从而介导WAT的棕色化；利用apoE-/-UCP1-/-小鼠的SVF细胞诱导脂肪细胞，证实UCP1基因敲除后，FGF21仍可使脂肪细胞出现类棕色化的形态学改变, 进而提示FGF21对脂肪细胞代谢状态的影响不完全依赖于UCP1。本课题首次揭示FGF21在脂肪组织代谢及动脉粥样硬化中的生物学作用及分子机制，并为疾病的防治提供了新的靶点，具有重要的理论意义和潜在的临床应用价值。