FAT/CD36介导的脂肪酸转运在下丘脑能量平衡中的作用及与肥胖的关系

A series of studies on human beings and animals have suggested that individuals showed different susceptibility to obesity when exposed to high fat diet and were defined as diet induced obesity(DIO) and diet induced obesity resistant (DIR). As a fatty acid translocase, FAT/CD36 plays an important role in long chain fatty acid transport and the levels of long chain fatty acyl-CoA. To test our hypothesis that hypothalamic FAT/CD36 is involved in central neural system sensing and monitoring of lipid signal, and thus related to obesity induced by high fat diet, the aims of this project are: 1. Identify the effect of gain-of-function and loss-of-function of FAT/CD36 in N1E-115 neroblastoma cells and primary hypothalamic neuronal cells, by monitoring LCFA-CoA and Malony-CoA level and NPY, AgRP and POMC gene expression; 2. Investigate the proposed role of hypothalamic FAT/CD36 in sensing fatty acid and regulating food intake by comparison study between DIO and DIR rats in response to a high fat diet and study the effects of hypothalamic FAT/CD36 in sensing of fatty acids and regulation of food intake in vivo by MBH injection of the lentivirus which can induce up or down- regulation of CD36; 3. Further study the mechanism by which hypothalamic FAT/CD36 is involved in energy homeostasis and development of high-fat dietary induced obesity using a conditional gene knockout mouse model of CD36 in hypothalamus that were generated with Cre/loxp technique.

前期研究表明，高脂膳食喂养的动物可表现为摄食过多和肥胖（DIO）及摄食正常和肥胖抵抗（DIR），下丘脑LCFA-CoA浓度在中枢神经细胞监测和感知脂质信号中起重要作用，而膜蛋白FAT/CD36介导的LCFA可能是影响其浓度的关键，与摄食过多和肥胖发生的关系值得关注。本项目拟：1.运用重组慢病毒上调或下调FAT/CD36 表达，在细胞水平观察FAT/CD36表达对神经细胞内LCFA-CoA浓度的影响及其与NPY、AgRP、POMC 基因及蛋白表达的关系；2.利用DIO和DIR动物模型，结合第三脑室注射慢病毒载体的方法，观察下丘脑FAT/CD36低表达或过表达对高脂膳食喂养的动物脂质感知、摄食行为及体重变化的影响；3.运用Cre/loxp 条件性基因敲除技术，观察下丘脑FAT/CD36 敲除对不同膳食条件下动物摄食的影响及其与肥胖发生的关系并探讨其作用机制，为防治肥胖寻找新靶点。

人体观察和动物实验均表明，高脂饮食喂养条件下部分对象容易发生肥胖，称为饮食诱导肥胖（DIO），另一部分对象可以维持正常体重，称为饮食诱导肥胖抵抗（DIR）。下丘脑神经元可以感知脂肪酸，并通过调节胰岛素分泌及其活性、影响脂肪沉积以及摄食行为，进而控制机体能量平衡。并且发现CD36在下丘脑神经元脂肪酸感知以及调节能量代谢中起到至关重要的作用。本课题通过体内和体外研究，联合观察CD36对下丘脑脂肪酸感知及相关食欲神经肽表达的影响，为肥胖的防治提供有力依据。首先通过高脂饮食诱导大鼠肥胖模型，分析在禁食和复喂状态下，DIO和DIR大鼠下丘脑食欲神经肽NPY，AgRP和POMC的表达，发现DIO大鼠下丘脑脂肪酸感知和食欲神经肽的调节异常。利用棕榈酸、葡萄糖作用于N1E-115小鼠神经母细胞瘤细胞，比较是否添加CD36抑制剂SSO对食欲神经肽表达的影响，发现棕榈酸和葡萄糖干预N1E-115神经细胞，能够显著降低NPY/AgRP基因表达，同样的干预条件能显著增加CD36基因表达。抑制CD36功能后，由棕榈酸导致的NPY/AgRP基因表达的降低也受到抑制。结果提示CD36介导的下丘脑脂肪酸感知可以在食欲调节中起重要作用。本研究为探讨通过CD36影响下丘脑脂肪酸感知及食欲神经肽表达预防肥胖提供了重要的线索。