Effect of dietary cholesterol and phospholipids on feed intake, growth performance and cholesterol metabolism in juvenile turbot (Scophthalmus maximus L.)

Dietary phospholipids play important roles in growth and nutrition metabolism in fish. Previous studies showed that moderate dietary cholesterol supplementation improved the growth performance of juvenile turbot fed plant-based or defatted fishmeal diets. Therefore, we examined the effect of dietary cholesterol and phospholipids on feed intake, growth performance and cholesterol metabolism in juvenile turbot (Scophthalmus maximus L.) (initial body weight 5.18 ± 0.01 g) during a 10-week period. Nine isonitrogenous and isolipidic diets were formulated to contain 0.0, 1.0 and 2.0% cholesterol (LC, MC and HC), and each with 0.0, 2.0 and 4.0% phospholipids (LP, MP and HP), respectively. A significant interaction between dietary cholesterol and phospholipids on weight gain rate was shown in the present study (P = 0.049). However, no significant interaction between dietary cholesterol and phospholipids was found in feed intake (P = 0.332) though the expression of the orexigenic factor ghrelin in the intestine was significantly affected by the interaction (P = 0.011). Except for total cholesterol, free cholesterol and cholesterol ester, both high-density lipoprotein cholesterol (HDL-C) (P = 0.012) and low-density lipoprotein cholesterol (LDL-C) (P = 0.002) in serum were significantly affected by the interaction between dietary cholesterol and phospholipids. Regarding the key genes involved in cholesterol and bile acid synthesis, no interaction between dietary cholesterol and phospholipids was found in the expression of 3-hydroxy-3-methylglutaryl-CoA reductase (hmgcr) (P = 0.380) and cholesterol 7α-hydroxylase (cyp7a1) (P = 0.587) in liver. In conclusion, there is a significant interaction between dietary cholesterol and phospholipids on the growth performance and the HDL-C and LDL-C involved in cholesterol transport, while no significant interaction was found on the feed intake in juvenile turbot.