Effects of alternative dietary oils on lipid metabolism and related gene expression in hybrid grouper (♀ Epinephelus fuscoguttatus × ♂ E. lanceolatu )

An 8-week growth trial was conducted to evaluate effects of dietary oil sources on growth, enzymes activity and genes expression levels related to lipid metabolism of hybrid grouper (♀Epinephelus fuscoguttatus × ♂E. lanceolatu) juveniles. Seven iso-lipid (97 g/kg of dry matter) and iso-protein (503.5 g/kg of dry matter) experimental diets were formulated containing 50 g/kg fish oil (FO; acting as controls) or various vegetable oils (VOs): corn oil (CO), sunflower oil (SO), tea oil (TO), olive oil (OO), rice oil (RO) and mixed oil (MO; comprising equal amounts of these oils). Each diet was fed to triplicate groups of 40 fish for per repetition (15.09 ± 0.01 g) for 56 days. The results show that (a) alternative dietary oils had no significant effects on final weight compared with control group (p > .05); (b) compared with FO group, VOs significantly changed the contents of serum lipoproteins, cholesterol, triglycerides and the activity of liver lipid-metabolizing enzymes (p < .05); (c) CO group had the least effect on the serum lipoproteins, triglycerides and cholesterol of grouper compared with control; the activity of liver lipid-metabolizing enzymes in RO and control group was the closest; (d) the mRNA levels of Δ6 Fatty acid desaturase (Δ6Fad), hormone-sensitive lipase (HSL) and lipoprotein lipase (LPL) were not significantly effected by lipid sources, but CO, TO, OO and MO significantly down-regulated the expression of fatty acid synthetase (FAS) mRNA level in liver, while RO opposite (p < .05); (e) vegetable oil significantly up-regulated peroxisome proliferator-activated receptor α (PPARα) and peroxisome proliferator-activated receptor β (PPARβ) mRNA levels, while TO and RO down-regulated peroxisome proliferator-activated receptor γ (PPARγ) mRNA levels (p < .05); and 6) MO significantly increased the mRNA levels of heart-type fatty acid-binding protein (H-FABP) and adipocyte-type fatty acid-binding protein (A-FABP) (p < .05), while other VOs had no effect on them (p > .05). In conclusion, dietary substitution of FO by VO in diet affected lipid metabolism of grouper, which may be regulated by PPARs.