Effect of dietary fatty acid composition on growth, fatty acids composition and hepatic lipid metabolism in juvenile turbot (Scophthalmus maximus L.) fed diets with required n3 LC-PUFAs

A 12-week feeding experiment was conducted to investigate the effects of dietary fatty acids composition on growth performance, lipid deposition and some genes expression of hepatic lipid metabolism in juvenile turbot (Scophthalmus maximus L.) (mean initial body weight, 9.49 ± 0.03 g) fed diets with required n3 LC-PUFA. Juvenile turbot were fed diets with palm oil (PO), rapeseed oil (RO), soybean oil (SO) or linseed oil (LO) replacing the same levels of fish oil (FO), respectively. Each diet was randomly fed to triplicate tanks, and each tank was stocked with 35 fish. The results showed that growth performance and feed utilization of turbot fed diets with required n3 LC-PUFA were independent of dietary fatty acids composition. As expected, C16:0, C18:1n, C18:2n-6, C18:3n-3 and n3 LC-PUFAs level in liver were up to the maximum in the PO, RO, SO, LO and FO group, respectively, and significantly higher than that in the other groups (P < 0.05). Fish fed the diet with RO had the lowest plasma triglyceride and the highest HDL-c/LDL-c, although no significant difference of plasma triglyceride had been found between the RO group and the LO group. Hepatic lipid content in fish fed diets with SO, RO, and LO was significantly higher compared with PO and FO groups. The higher activities of hepatic G6PD and ME were found in fish fed diets with PO or FO compared to LO. The relative expression of LPL, LXR, and ApoB-100 gene in the RO group and the LO group, MTP gene in the LO group, PPARα and FAS genes in the PO group, and PPARγ gene in the SO group were significantly higher than those in the FO group. These results indicated that the increase in hepatic lipid deposition of turbot induced by the SO, RO, and LO diets are associated with up-regulation of some genes involved in lipids biosynthesis metabolism.