Molecular identification and expression characteristics analysis of subfatin gene from grass carp

Subfatin plays an important role in lipid metabolism, inflammation and energy consumption in mammals, but its functions in fish are rarely reported. To investigate the physiological function of subfatin in glucolipid metabolism of grass carp, we took Ctenopharyngodon idella as the research object and cloned the subfatin gene by RT-PCR. The oral glucose tolerance test (OGTT), fast and refeeding, inducing lipid accumulation and primary hepatocyte culture were proceeded. The results show that the grass carp subfatin was 861 bp, encoding 286 amino acids, and three O-linked glycosylation sites were located in the subfatin. The results of OGTT experiment show that after glucose treatment of grass carp for 1 and 3 h, the expression of subfatin mRNA was significantly up-regulated in liver and intestinal tissues, and it was also significantly up-regulated in the brain and kidney tissues after 3 h of glucose treatment. In fast and refeeding experiment, the results show that the expression of subfatin mRNA in brain, fat, intestinal and liver tissues was significantly down-regulated after 14-day starvation treatment, and was significantly up-regulated after re-feeding. In induced lipid accumulation experiment, the results show that subfatin expression in brain, fat, intestinal and liver tissues was significantly up-regulated in the induced group. In primary hepatocytes, subfatin expression level increased significantly by treatment with glucose, oleic acid and glucagon. However, subfatin level decreased significantly by treatment with insulin. In conclusion, this study demonstrates that Subfatin is involved in the process of glucose and lipid metabolism in grass carp and plays a regulatory role, which provides a theoretical basis for elucidating the physiological functions of Subfatin in fish.