Effects of dietary choline supplementation on growth performance and hepatic lipid transport in blunt snout bream (Megalobrama amblycephala) fed high-fat diets

• Extra supplemental choline in high-fat diet could improve growth performance.
• Sufficient choline supplementation is help to diminish hepatic lipid deposition.
• Increased choline supplementation elevated hepatic SAM levels.
• Extra choline supplementation in high-fat diet upregulated apoB-100 and MTTP gene expression.

In this study, we elucidated the choline metabolic pathways and its effects on growth and hepatic lipid transport in blunt snout bream, Megalobrama amblycephala. Fish were fed six experimental diets containing three lipid levels (5%, 8%, and 11%) and two choline supplementation levels (1200 and 1800 mg kg− 1) for 8 weeks. After the feeding trial, viscera/body ratio, hepatosomatic index, plasma aspartate aminotransferase activities, and plasma triglyceride and cholesterol contents as well as liver lipid content all increased significantly (P < 0.05) as dietary lipid levels increased from 5 to 11% in terms of dietary lipid levels, whereas feed conversion ratio, plasma cholesterol content and liver lipid content decreased significantly (P < 0.05) with increasing choline supplementations. Weight gain increased significantly (P < 0.05) with increasing dietary choline supplementations when dietary lipid levels reached 11%. Additionally, hepatic lipid accumulation was further observed by oil red O staining. An increase in hepatic S-adenosylmethionine was found in fish fed diets supplemented with 1800 mg kg− 1 choline, indicating that extra choline supplementation increases very low density lipoprotein (VLDL) production through methylation of phosphatidylethanolamine to synthesize phosphatidylcholine. Additionally, increased SAM production resulted in a subsequent increase in glutathione concentration, suggesting a possible benefit in mitigating oxidative stress induced by a high-fat diet. 1800 mg kg− 1 choline supplementation in diet significantly up-regulated the relative mRNA expression levels of apolipoprotein B-100 and microsomal triglyceride transfer protein, which induced VLDL synthesis and assembly.