Effects of supplementation of sulfur-containing amino acids in high-lipid diets on lipid metabolism of turbot (Scophthalmus maximus)

Abstract:

A 56-day feeding trail was conducted to investigate the effects of methionine, cysteine and taurine on lipid accumulation and lipid metabolism of turbot (Scophthalmus maximus) fed high levels of dietary lipid. A high-lipid (16%) diet was used as the control diet, and 1.5% methionine (Met), 1.5% cysteine (Cys), and 1.5% taurine (Tau) was separately added into the control diets to obtain three test diets. Fish with average initial weight of (7.98±0.02) g was used. Each diet was fed to triplicate tanks of 30 fish. The feeding trial was conducted in flow-through seawater system. The results showed that no significant differences were observed among treatments in lipid content of whole body and muscle. Group Tau had the lowest liver lipid content, significantly lower than group Cys. The serum triacylglycerol and total cholesterol contents were the highest in group Tau, significantly higher than other groups. The dietary supplementation of sulfur-containing amino acids decreased the EPA content in fish body, while Tau increased the contents of C18:2n-6 and C18:3n-3. The dietary supplementation of sulfur-containing amino acids significantly regulated the lipid metabolism-related gene expression. Dietary Met supplementation up-regulated the liver mRNA expression of FAS; Dietary Cys supplementation up-regulated the liver mRNA expression of DGAT1; Dietary Tau supplementation down-regulated the hepatic mRNA expression of a series of lipogenic genes such as ACACβ, FAS, SREBP1, PPARα1, PPARγ and LXRα. Regarding the growth performance, group Tau had significantly higher final body weight of fish than other groups, but no significant difference was observed in survival, condition factor, hepatosomatic index and viscerosomatic index among dietary groups. Supplementation of methionine, cysteine and taurine in high-lipid diets regulates the lipid metabolism of turbot. Taurine appears to be able to reduce the hepatic lipid accumulation in turbot but cysteine tends to increase it.