生长激素调控鱼类脂肪分解代谢的分子机制

Growth Hormone (GH) is the main endocrine promoting factor of fish growth. In the previous report, gh mutant zebrafish exhibited retarded growth and increased fat accumulation, which indicated that the promoting action of GH in growth is mainly promoted by accelerating the fat catabolic mechanism, but the based molecular mechanism is not completely understood. And in our previous reports in zebrafish, deletion of suppressor of cytokine signaling-1a (Socs1a), which mediates the negative regulation of the GH signaling, caused decreased fat accumulation, and enhanced somatic growth. While, deletion of the main activation enzyme of vitamin D3, Cyp2r1, which needs to be highly expressed during the rapid growth period of juvenile zebrafish, caused retarded somatic growth, increased fat accumulation, and diminished GH signaling pathway. This study is planned firstly to determine the physiological process of GH regulation in fat catabolic metabolism through physiological and biochemical analysis, and secondly to research the based molecular mechanism of GH signaling in promotion of fat catabolic metabolism through various research methods, such as molecular biology, RNA-Seq, cell line analysis, by using these in vivo models (as the gh1 mutants, socs1a mutants, cyp2r1 mutants, and the common carp). The implementation of this study can further understand the mechanism of action of GH in fish growth, and provide new molecular strategies and theoretical basis for molecular genetic breeding of fish and nutrition metabolism research.

生长激素（GH）是鱼类主要生长内分泌促进因子。据报道，敲除GH的斑马鱼生长受到阻滞，脂肪积累增多，GH主要通过促进脂肪利用来促进鱼体生长，但GH促进脂肪利用的分子机制尚不完全清楚。我们在斑马鱼上的研究发现，敲除GH信号通路负反馈调控因子Socs1a，腹部脂肪组织利用显著增强，并促进蛋白质合成进而促进生长；敲除需要在幼鱼生长快速期高表达的维生素D3活化酶之一的Cyp2r1，导致敲除鱼体内的GH信号通路受阻，且生长受到阻滞，腹部脂肪积累增多。本研究拟用gh、socs1a和cyp2r1这三种基因突变型斑马鱼品系，结合养殖鱼类鲤鱼，首先通过生理生化指标分析GH调控脂肪分解代谢的生理过程，再通过转录组分析、分子生物学、细胞实验等研究手段，研究GH调控脂肪分解代谢的分子机制。本项目的实施，将能进一步理解GH促进鱼类生长的作用机制，为鱼类的分子遗传育种和营养代谢研究提供新的分子策略和理论基础。

生长激素（GH）是个多效性因子，是鱼类主要的生长内分泌促进因子。我们前期结果发现：gh敲除斑马鱼和出现生长激素信号通路抵抗的维生素D缺乏的cyp2r1敲除斑马鱼，均出现生长受到阻滞、脂肪增多、脂肪组织利用障碍的表型；敲除GH信号通路负反馈调控因子Socs1a，腹部脂肪组织利用显著增强，并促进蛋白质合成进而促进生长。这些结果表明，GH通过促进脂肪组织的利用为机体的生长提供能量，但其分子机制尚不完全清楚。本项目首先对gh敲除鱼的整体脂肪进行了扫描，并检测了肌肉和肝脏组织甘油三酯含量，其次检测了gh和crp2r1两种敲除鱼肌肉、肝脏和脂肪组织的代谢相关信号通路AKT、AMPK、S6等的磷酸化水平和线粒体蛋白Cox IV含量。此外，分别对gh和cyp2r1敲除鱼的脂肪组织转录组数据进行了KEGG、PPI和Hubgene筛选分析。综合以上结果，我们推测GH通过调控维生素D信号通路关键基因和脂肪代谢相关基因的表达来综合调控脂肪酸的代谢，维生素D信号通路在脂肪代谢生理过程上位于GH信号通路的下游。由于gh敲除鱼致死率较高，造成计划中的两个实验还在继续。项目执行过程中，我们发现了维生素D缺乏的cyp2r1敲除鱼血糖升高、雌雄繁殖异常的表型，在该基金支持下做了拓展研究。经研究我们发现：维生素D缺乏导致脂肪组织线粒体脂肪酸氧化代谢障碍引起的胰岛素抵抗，进而造成血糖升高；维生素D缺乏引起斑马鱼卵巢延迟和精巢发育异常。本项目探讨了GH和维生素D两大信号通路在通过调控脂肪代谢来促进个体生长生理过程中的作用和关系，以及维生素D缺乏在血糖代谢和雌雄生殖两个方面的功能，为调控鱼类的营养代谢和分子遗传育种提供一定的理论基础。