载脂蛋白A5经Cidec负向调控脂肪间充质干细胞成脂分化的机制探讨

Recent evidence has emerged for an association between apolipoprotein A5 (apoA5) and the development of obesity. However, the mechanism involved remains to be fully elucidated. We observed that apoA5 significantly reduced the lipid droplet formation during adipogenesis of adipose-derived mesenchymal stem cells (AMSCs), indicating that apoA5 exerts inhibitory effect on adipocyte differentiation. Moreover, apoA5 could significantly decrease the expression of Cidec, a known lipid droplet-associated protein. It has been recently reported that Cidec is also localized to the nucleus and interacts with adipogenic transcription factor C/EBPβ, through which may promote adipogenesis. Therefore, we hypothesized that apoA5 may inhibit adipogenesis of AMSCs by regulating the C/EBPβ signaling through suppression of Cidec expression and/or nuclear distribution. In this study, we will focus to examine the effect of apoA5 on the expression of differentiation markers and the Cidec- C/EBPβ signaling and identify the functional region of apoA5, in order to verify the mechanism by which apoA5 regulates adipocyte differentiation. This study is expected to provide a new strategy for the prevention and treatment of obesity.

载脂蛋白A5（apoA5）与肥胖的发生密切相关，但其机制不明。申请者前期研究发现：在体外诱导人脂肪间充质干细胞（AMSCs）成脂分化过程中，apoA5可显著减少新生脂肪细胞脂滴的形成，推测apoA5具有抑制AMSCs成脂分化的作用；而且，apoA5显著下调脂滴相关蛋白Cidec的表达。最新研究表明：Cidec的核转移及其与成脂分化转录因子C/EBPβ的结合可能促进脂肪细胞的分化。由此推测：apoA5可能通过下调Cidec表达和/或抑制Cidec的核转移，继而影响C/EBPβ及其下游通路的激活，从而发挥抑制AMSCs成脂分化的作用。本项目拟从分子、细胞和动物水平观察apoA5对人AMSCs成脂分化标志物表达以及Cidec-C/EBPβ信号通路的影响、鉴定apoA5发挥作用的关键结构，来明确apoA5影响脂肪细胞分化的调控机制。本项目将开拓对apoA5的认识，并为肥胖的防治提供新思路。

载脂蛋白A5（apoA5）与肥胖及相关代谢性疾病的发生、发展密切相关，但具体机制尚不明确。本项目以人脂肪间充质干细胞（AMSCs）为研究靶点，从细胞水平观察apoA5对人AMSCs成脂分化的影响，探索apoA5影响AMSCs成脂分化的分子调控机制。研究结果发现：（1）在人AMSCs成脂分化过程中，apoA5可被细胞摄取；随着成脂分化的进行，apoA5可呈浓度依赖性降低细胞内脂滴的数量、体积以及甘油三酯含量，并显著影响成脂分化标志物的基因表达水平，提示apoA5可通过抑制人AMSCs成脂分化，从而影响肥胖的发生和发展。（2）ApoA5进入细胞后与Cidec蛋白共定位于脂滴表面，并与Cidec存在相互作用。随着人AMSCs成脂分化，apoA5可呈浓度依赖性的降低Cidec基因和蛋白的表达水平，并伴随其下游通路C/EBPβ、C/EBPα、SREBP-1c及PPARγ的基因表达水平的显著下调。（3）通过沉默及过表达Cidec基因，我们进一步证实了apoA5通过下调Cidec的表达以及核转移发挥抑制AMSCs成脂分化的作用。本项目为探索apoA5的功能提供了新思路，揭示了apoA5作为脂肪细胞内脂质代谢的新的调节因子，并为肥胖及相关代谢性疾病的防治提供以apoA5为靶点的新防治策略。