Effects of supplemental glycerol monolaurate on growth, hepatic lipid metabolism, antioxidant capacity and mitochondrial function of large yellow croaker (Larimichthys crocea) fed diets with high soybean oil level

The present study was conducted to investigate the effect of supplemental glycerol monolaurate (GML) on growth performance, hepatic lipid metabolism, antioxidant capacity and mitochondrial function in large yellow croaker (Larimichthys crocea) fed diets with high soybean oil (SBO) level. The trial diet with 7% fish oil (FO) was designed as the negative control while the diet with 7% SBO was designed as the positive control. The other three diets were formulated with the administration of 400, 800 and 1600 mg/kg GML (0.04%, 0.08% and 0.16%) on basis of the positive control diet. Results showed that the specific growth rate (SGR) was increased and the feed conversion ratio (FCR) was decreased significantly in fish fed diets with GML supplementation compared with the positive control diet, while no difference was observed in the survival rate (SR) among dietary treatments. Fish fed the diet with 0.04% GML supplementation had significantly lower triglycerides and total cholesterol contents compared with those in the positive control group. The mRNA expression of lipogenesis-related genes (srebp1c and acc) were down-regulated while the mRNA expression of lipolysis and fatty acid & beta;-oxidation-related genes (atgl, ppar & alpha; and cpt1) were up-regulated in fish fed diets with 0.04% and 0.08% GML. Compared with the positive control diet, fish fed diets with 0.04% and 0.08% GML supplementation exhibited remarkably higher activities of superoxide dismutase, catalase and the content of glutathione, as well as lower malondialdehyde level. Furthermore, in fish fed diets with 0.04% and 0.08% GML, the morphology of mitochondria was improved and their number was increased. The mRNA expression of genes related to mitochondrial biogenesis (pgc1-& alpha;, tfam and nrf1) were significantly increased in fish fed with 0.04% and 0.08% GML supplementation. Meanwhile, the content of triphosadenine (ATP), the activity of citrate synthase (CS) and succinate dehydrogenase (SDH) in liver were increased significantly in 0.04% and 0.08% treatments compared with the positive control group. Conclusively, these results indicated that dietary GML supplementation (0.04%-0.08%) could promote growth performance, improve liver lipid metabolism, antioxidant capacity and enhance mitochondrial function in large yellow croaker fed with the SBO based diet.