Dietary bile acids supplementation mainly regulates the amino acid metabolic pathways without decreasing bile acids levels in the liver of farmed European eel (Anguilla anguilla) juveniles

Abstract

This study was conducted to investigate the effects of dietary bile acids (BAs) supplementation on the liver metabolism of farmed European eel (Anguilla anguilla) juveniles. Fish with similar body weight (140 g per fish) in six tanks (681.7 ± 22.7 kg fish per tank) were randomly divided into the control group fed a basal diet and the BAs group fed a basal diet supplemented with 500 mg/kg BAs. The experiment lasted for 15 weeks. The untargeted metabolomics method was used to evaluate global metabolic profiles, while the targeted metabolomics method was utilized for BAs profile analysis in the liver. Compared with the control group, there were 33 upregulated metabolites and 15 downregulated metabolites in the BAs group. The differential metabolites belonged to amino acids, carbohydrates, lipids, nucleotides, vitamins, etc. Among the top ten differential metabolic pathways affected by BAs supplementation, the main pathways were relevant to amino acids metabolisms. These included aminoacyl-tRNA biosynthesis, phenylalanine, tyrosine and tryptophan biosynthesis, alanine, aspartate and glutamate metabolism, histidine metabolism, arginine and proline metabolism, beta-alanine metabolism, phenylalanine metabolism, D-glutamine and D-glutamate metabolism, sphingolipid metabolism, and pantothenate and CoA biosynthesis. Only the levels of deoxycholic acid, glycodeoxycholic acid, and glycoursodeoxycholic acid were significantly increased in the liver of the European eel in the BAs group (P < 0.05). These results indicated that exogenous bile acids might mainly regulate the metabolism of amino acids without decreasing the bile acids levels in the liver of farmed European eel juveniles.