Effects of choline on the growth performance, antioxidant function and lipid metabolism in juvenile largemouth bass fed with high-fat diet

Abstract

This study carried out an 8-week feeding experiment to evaluate the influence of dietary choline supplementation on the growth performance, antioxidant function and lipid metabolism in juvenile largemouth bass fed with high-fat diet. Accordingly, five experimental diets included the positive control diet (PC, 10% fat without choline supplementation), negative control diet (NC, 15% fat without choline supplementation) and high-fat diet (15% fat) supplemented with 0.3% (NC+CH0.3), 0.6% (NC+CH0.6) and 1.2% (NC+CH1.2) choline. The analyzed choline contents in experimental diets were 2.56, 2.61, 4.25, 6.58 and 9.89 g/kg, respectively. Accordingly, each experiment diet was randomly divided into 3 replicates containing 25 fish with 6.84 ± 0.01 g initial weight. Results showed that compared with the PC group, NC group decreased growth performance and increased viscerosomatic index and intraperitioneal fat ratio (P<0.05). Liver superoxide dismutase activity and serum total antioxidant capacity were decreased while serum malondialdehyde content was increased in NC group (P<0.05). NC group significantly increased lipid deposition, which was identified by increased lipid contents in the whole body especially back muscle and liver, liver fatty acids composition (16:1n-7, 18:1n-9, 20:1n-9,18:3n-3), hematological parameters (total cholesterol, triacylglycerol). Compared with NC group, dietary choline supplementation increased (P<0.05) growth performance and 6.58 mg/kg choline supplementation reached highest value. Liver n-3/n-6 PUFA, DHA/EPA contents and superoxide dismutase capacity were increased (P<0.05) while serum malondialdehyde content was decreased (P<0.05). 9.89 mg/kg choline supplementation increased expression levels of fatty acid synthase, acetyl-CoA carboxylase, elongase of very long-chain fatty acid 5 (elovl 5), Δ6 fatty acyl desaturase genes, while diet supplemented with 6.58 mg/kg choline increased levels of elovl 5 and glucose 6-phosphate dehydrogenase genes (P<0.05). Our results concluded: (1) 8-week high-fat feeding induced growth suppression, lipid accumulation and oxidative damage in juvenile largemouth bass; (2): Appropriate choline supplementation could alleviate the growth suppression, oxidative damage and lipid accumulation induced by high fat diet, and recommended choline dosage in largemouth bass compound feed was 6.58 g/kg.