高脂通过HIF1-α双向调控ATGL诱导草鱼脂肪细胞增大和增生的分子机制

草鱼脂肪组织通过脂肪细胞的增大和增生响应高脂摄入，其机制尚不明确。研究表明，高脂通过代谢和氧气的消耗加剧，引发小鼠脂肪细胞缺氧。低氧促进小鼠前体脂肪细胞分化。同时，HIF1-α作为介导缺氧信号的转录因子，通过泛素化降解小鼠脂肪细胞ATGL蛋白。因此，结合高脂促进草鱼脂肪组织脂解、HIF1-α表达以及草鱼ATGL是HIF1-α潜在靶基因的前期基础，申请人推测：高脂条件下，HIF1-α上调ATGL转录表达促进基础脂解，进而激活PPARγ诱导草鱼脂肪细胞增生；还通过泛素-蛋白酶体途径下调ATGL蛋白诱导草鱼脂肪细胞增大。为验证该假说，本项目拟采用细胞共培养、染色质免疫共沉淀等技术，结合在体实验，探究HIF1-α对ATGL转录表达和蛋白翻译后修饰的双向调控在高脂诱导草鱼脂肪组织重构中的驱动作用及发生规律。研究结果有助于阐明高脂饲料投喂下鱼类脂肪蓄积发生机制，为其营养调控策略的研发提供理论基础资料。

Adipose tissue expansion of grass carp occurs through an enlargement in adipocyte size (hypertrophy) and an increase in adipocyte numbers (hyperplasia) in response to high fat diet, but the underlying mechanism is not clear. Studies in mice have shown that high fat induces hypoxia in adipocytes through increased metabolism and oxygen consumption. Adipogenesis is stimulated by hypoxia in 3T3-L1 cells. In addition, our lab found that HIF1-α, a transcription factor mediating hypoxia signal, was highly expressed in fat tissue of grass carp fed with high fat. HIF1-α can degrade ATGL protein by ubiquitination in 3T3-L1 adipocytes. Based on our previous studies that ATGL is the potential target gene of HIF1 - α and the lipolysis was induced by high fat, we speculate that HIF1-α may induce the hypertrophy of grass carp adipocytes by promoting the degradation of ATGL protein via ubiquitin-proteasome system, and also regulate the transcription of ATGL gene to induce the proliferation of grass carp adipocytes via activating PPARγ in response to high fat diet. In order to test the hypothesis, this project plans to use the molecular biological and cell biological techniques such as cell co culture, chromatin immunoprecipitation, etc. in combination with in vivo experiments, to explore the driving role of HIF1-α in high fat diet-induced adipocyte remodeling via dual regulation of ATGL. The results could be helpful to elucidate the mechanism of fat accumulation fed with high-fat diet and provide theoretical basis for the research of nutrition and feed development strategies in fish.