增强血管周围棕色脂肪细胞功能对血管保护作用的机制研究

Perivascular adipose tissue (PVAT) is a local deposit of adipose tissue surrounding the vasculature. PVAT is present throughout the body and has been shown to have an important local effect on blood vessels. There are 2 major types of adipose tissues in mammals, white and brown. The balance between white and brown adipose tissue play an important role in the metabolism stabilization. In normal adipose tissue, the metabolic balance favors a noninflammatory state. With the development of obesity or many other disorders, the metabolic milieu changes, favoring the instigation and perpetuation of inflammation, leading atherogenesis and many other vascular diseases. In our previous experiments, we have found that activation of the brown adipocyte plays a beneficial role in suppressing the inflammation in PVAT. So, we presumed that upregulation of the brown adipocyte may have a putative protective role in adjusting the function of vasculature. To prove this, we will study if the upregulation of brown adipocyte in abdominal aortic PVAT might have an effect on atherogenesis, contractile function of vascular, endotheliocyte and macrophage, using some molecular biology techniques and other like Transwell co-culture system. As this research continues, the understanding of the biology of perivascular brown adipocyte and its effect on the vasculature will expand. As this occurs, the next step will be the crossover of the science from experimental and epidemiological studies into clinical applications.

血管周围脂肪组织紧贴血管外膜，可通过局部作用对血管功能产生重要影响。脂肪组织依据结构不同，可分为白色及棕色脂肪组织，两者含量变化对于维持机体正常功能有着重要意义。肥胖等多种疾病可导致血管周围脂肪组织炎症，从而诱发诸多血管性疾病如动脉粥样硬化的形成。本课题组前期研究发现，上调棕色脂肪细胞功能，可抑制血管周围脂肪组织的炎症状态。因此我们推测，通过增强血管周围脂肪中棕色脂肪细胞功能，可对血管功能产生积极的保护性作用。为证明这一假说，我们通过对动物模型的干预，采用分子生物学方法及Transwell细胞共培养等技术手段，从整体及细胞两个层次，观察增强棕色脂肪细胞功能对腹主动脉粥样斑块形成，血管收缩功能，及内皮、巨噬细胞功能的作用。本课题将从新的视角阐明棕色脂肪与血管功能的关系，为今后临床干预、治疗性药物的筛选和开发提供新方法和新靶点。

本课题为证实提出的实验假说，我们采用相关技术方法促进腹主动脉周围脂肪（PVAT）中白色脂肪向棕色脂肪（BAT）转化，增强PVAT中BAT功能。从动物整体及细胞两个层次证实了增强PVAT中BAT功能对于血管的保护作用，并初步阐释了这一保护现象后的机制。小鼠腹主动脉PVAT中注射β3受体激动剂或者转染PRDM16腺病毒载体，均能促进腹主动脉PVAT中BAT样脂肪细胞的分化。增强PVAT中BAT功能可增加PVAT内毛细血管密度，并调节炎症因子及脂肪因子水平。BAT功能增强对动脉粥样硬化斑块形成具有显著抑制作用，并可稳定斑块；同时对内皮功能不全导致的舒张功能减退具有显著保护作用。PRDM16转染脂肪前体细胞可促使其向BAT样细胞分化。采用Transwell技术将转染PRDM16的棕色脂肪样细胞（BAC）与内皮细胞及巨噬细胞共培养，从细胞层面证实BAC对内皮细胞及巨噬细胞的作用。结果显示BAC可促进血管内皮细胞的增殖，增加血管内皮细胞中NO及eNOS含量，降低内皮细胞的单核细胞粘附率。BAC还可抑制巨噬细胞的胆固醇摄入，促进M2亚型的极化，并调节巨噬细胞的分泌功能。人主动脉内皮细胞予以血管紧张素Ⅱ（AngⅡ）处理后NO水平下降，PCG-1α也呈现下降趋势。过表达PGC-1α可以逆转AngⅡ所造成的NO下降，同时还可抑制AngⅡ介导的eNOS，PI3K以及 AKT脱磷酸作用。