Differential expression of lipid metabolism-related genes and miRNAs in Ctenopharyngodon idella liver in relation to fatty liver induced by high non-protein energy diets

To explore the mechanism of fatty liver formation induced by high non-protein energy diets in grass carp (Ctenopharyngodon idella), basal diet and high-energy diets were fed to juvenile grass carp for 9weeks. The experimental groups fed on high-energy diets which included a high-lipid diet (H-LIP), a high-carbohydrate diet (H-CHO) and a high-lipid and carbohydrate diet (H-CL). The control group fed on basal diet. Growth performance, liver fat accumulation, serum biochemical indexes and the expression levels of lipid metabolism-related genes (SREBP-1, PPAR, FAS, ACC1, and LPL) and miRNAs (miR-33, miR-122, and miR-370) were examined at the end of the feeding trial. There were no significant differences in growth rate and feed efficiency among the four groups. However, significant increase in mesenteric and liver fat contents, and lipid droplets in the liver was induced by high-lipid and high-carbohydrate diets. There were significant differences in serum biochemical indicators such as AST/ALT, GLB, TG and TP, and liver fatty acid composition between the control and experimental groups. The expression levels of SREBP-1, PPAR, FAS, ACC1 and LPL were upregulated, while CPT-1 was downregulated with the high-energy treatments. Additionally, the expression levels of miR-33, miR-122 and miR-370 in the liver were higher in the three high-energy treatments than those in the control (P<0.05). The results suggest that modifications of lipid metabolism-related genes and miRNAs may be involved in fatty liver formation induced by high non-protein energy diets in grass carp.