家鸡GPR120受体介导多不饱和脂肪酸对肝脏脂质代谢的调节效应探究

In poultry industry, polyunsaturated fatty acids (PUFAs), such as sunflower oil, were added into the daily diet for the broilers to reduce their fat deposition and improve their carcass quality, however, the underlying mechanism of their actions remains largely unknown. Recently, G protein-coupled receptor 120 (GPR120) was identified to be the functional receptor for PUFAs and involved in the regulation of lipid metabolism and anti-inflammatory effects in mammals. In our recent study, we found that, as in mammals, GPR120 exists in chickens. Functional assay further demonstrated that chicken GPR120 could be activated by PUFAs, indicating that GPR120 is a functional receptor for PUFAs. Quantitative real-time PCR assay revealed that GPR120 is highly expressed in chicken liver. All the preliminary data led us to hypothesize that GPR120 may be involved in mediating the actions of PUFAs on lipid metabolism in chicken liver. To verify this hypothesis, present study aims to: 1) examine the gene structure and functionality of GPR120 and its downstream signaling pathways; 2) reveal the effects of PUFAs and its receptor GPR120 on liver lipid metabolism (such as fatty acid β-oxidation and fatty acid synthesis) using both in vitro (primary hepatocyte culture) and in vivo approaches. The results from present study will not only help to elucidate the underlying mechanism of PUFAs and its receptor GPR120 on hepatic lipid metabolism, but also aid to develop a novel strategy to decrease fat deposition in chickens (such as addition of PUFAs into daily diet).

在家禽养殖中，日粮中添加富含多不饱和脂肪酸(PUFAs)的葵花籽油等，可促进体内脂肪酸氧化，减少脂肪沉积，改善酮体品质。但是，这些PUFAs发挥效应的分子机制待阐明。G蛋白偶联受体120(GPR120)在哺乳动物中被发现可介导PUFAs参与调节脂质代谢和抗炎反应等。申请人首次克隆家鸡GPR120基因并发现其可作为PUFAs的功能性受体，此外，该基因在家鸡肝脏组织中高表达，作为家鸡最主要的脂肪合成器官，所有预研结果提示：GPR120或可介导PUFAs的生理效应，参与家鸡肝脏脂质代谢调节。为验证该假说，申请人拟研究：1)家鸡GPR120的基因结构与功能，阐明其下游信号通路。2)在细胞(原代培养肝细胞)和个体水平上，解析PUFAs及其受体GPR120对肝脏脂质代谢的调控机制。上述研究预期为揭示PUFAs和脂肪沉积的关系奠定基础，此外，本研究亦为新型饲料添加剂研发，降低动物脂肪沉积提供新的策略。

在家禽养殖中，日粮中添加富含多不饱和脂肪酸(PUFAs)的葵花籽油等，可促进体内脂肪酸氧化，减少脂肪沉积，改善酮体品质。研究认为多不饱和脂肪酸 (PUFA) 可以抑制脂肪细胞分化，诱导脂肪酸氧化，增强能量消耗，降低腹部脂肪的堆积，但是家禽养殖中PUFAs发挥效应的分子机制仍待阐明。本项目前期研究发现家鸡GPR120基因可作为PUFAs的功能性受体，在家鸡肝脏组织中高表达，可能介导PUFA调控肝脏脂质代谢。在本项目中，我们以家鸡为研究对象，首先解析了多不饱和脂肪酸内源性受体GPR120的基因结构和剪接变体情况，并确定其核心启动子区域和调控元件；其次明确其在肝脏组织高表达的特征，并检测其在不同发育阶段和不同品系的差异表达特征，利用单细胞测序明确其特异性表达于肝实质细胞类群；此外，本研究解析了GPR120 介导的胞内信号通路，明确其可以作为PUFA 和激动剂的功能性受体，激活下游MAPK 信号通路和β-arrestin 信号通路；最后，基于原代肝实质细胞培养和体内缓释泵植入实验，本研究揭示家鸡GPR120 及PUFAs 参与调节肝脏糖脂代谢，包括促进脂肪代谢（如诱导脂肪酸β-氧化）和抑制糖原合成等效应，明确多不饱和脂肪酸可以通过作用于内源性功能受体GPR120 参与抑制家鸡肝脏脂肪生成，并显著降低腹部脂肪沉积。本项目研究成果不仅有助于最终揭示家鸡GPR120 介导的生理效应及影响肝脏糖脂代谢和腹部脂肪沉积的分子机制，而且为商品化家鸡的分子育种提供理论依据，同时，也为开发新型饲料添加剂，降低动物脂肪沉积，通过限制脂肪沉积以提高生产饲料的利用率，为提升家鸡的生产性能提供新的策略。