载脂蛋白M下调肝细胞Cidec表达的分子机制研究及其在动脉粥样硬化中的意义

It is shown that apolipoprotein M (apoM), triglycerides (TG) play an important role atherogenesis in recent years, apoM regulates TG content has not been reported up to now . The studies which been done by the applicant have shown that, apoM combined with liver cell membrane high-density lipoprotein (HDL) receptor influence proliferation peroxide gamma (PPAR γ) expression, and then down-regulate cidec expression and reduce the liver cell TG content. According to PPAR γ can be combined with the PPAR γ element of target genes activate target genes, We puts forward hypothesis that apoM combined with liver cell membrane HDL receptor, through the cAMP/PKA signal pathway influence PPAR γ expression, PPAR γ combined with cidec gene promoter PPAR γ element down-regulates cidec expression, will employs reconbination report gene test, EMSA, ChIP technologies etc, clarify the molecular mechanism of down-regulation of cidec expression by apoM; After down-regulation of cidec expression usin cidec siRNA in vitro and in vivo, cidec can be directly reduce in hepatocytes and plasma TG content. We will further reveal apoM-PPAR γ-Cidec-TG metabolic regulation pathways and its the important biological significances in atherogenesis through the studies in the project.

近年研究表明：载脂蛋白M（apoM）,甘油三酯（TG）在动脉粥样硬化(AS)发生中起着重要作用，apoM调节TG含量未见报道。申请人前期研究发现，apoM结合肝细胞膜高密度脂蛋白（HDL）受体影响过氧化增殖激活受体γ（PPARγ）表达，进而下调cidec表达而降低肝细胞TG含量。根据PPARγ可结合靶基因的结合元件激活靶基因活性，提出apoM结合肝细胞膜HDL受体后，通过cAMP/PKA信号通路影响PPARγ表达，PPARγ与cidec基因启动子结合元件结合下调cidec表达的假说，拟用重组报告基因检测、EMSA、ChIP等技术阐明apoM降低Cidec表达的分子机制；用siRNA使cidec基因沉默观察体外、体内下调cidec表达后，Cidec可直接降低细胞或血浆TG含量。通过本项目研究可深入揭示apoM→PPARγ→Cidec→TG代谢调节通路及其在AS发生、发展中的重要生物学意义。

动脉粥样硬化（AS）是引起心脑血管基本的主要原因，但其发生机制尚未完全阐明，高甘油三酯(TG)血症是AS的重要原因；本课题组前期研究发现载脂蛋白M（apoM）可引起培养肝细胞TG含量降低，本项目试图找到apoM降低TG含量的细胞内信号转导通路，进而为防治AS提供新的靶点。.一、本项目进行了如下主要研究及获得了相应结果：. 1.进行了人apoM蛋白作用培养人肝细胞后，发现细胞内PPARγ分子表达降低。. 2. 根据基因表达调控理论，克隆了人肝细胞Cidec 基因不同长度启动子，检测其具有活性。. 3. 用共转染实验发现，PPARγ对Cidec基因活性具有上调作用。.根据上述研究结果，我们发现人apoM可降低肝细胞PPARγ表达，进一步发现了PPARγ能结合人Cidec基因启动子内的初步结合部位，使其表达上调。从而明确了apoM→ PPARγ → Cidec代谢信号通路，进而降低肝细胞内TG含量。所取得的成果目前国内外尚未见相关内容报道。