Metabolites, gene expression and gut microbiota profiles suggest the putative mechanisms via which dietary creatine increases the serum taurine and g- ABA contents in Megalobrama amblycephala

Abstract

High carbohydrate diets can affect the growth and metabolism of fish; e.g. decrease the concentration of liver betaine and cause disturbances in the creatine pathway, and damage the liver. Previous studies have shown that dietary betaine can effectively alleviate these negative effects. The aim of this study was to explore the effects of creatine on growth performance, liver health status, metabolites and gut microbiota in M. amblycephala. The results showed that supplementing creatine and betaine together reduced the feed conversion ratio significantly (P < 0.05, compared to CD and HCD) and improved liver health (compared to HCD). Compared with the BET group, dietary creatine significantly increased the abundances of Firmicutes, Bacteroidota, ZOR0006 and Bacteroides, and decreased the abundances of Proteobacteria, Fusobacteriota, Vibrio, Crenobacter, and Shewanella in the CRE1 group. Dietary creatine increased the content of taurine, arginine, ornithine, γ-aminobutyric acid (g-ABA) and creatine (CRE1 vs. BET group), and the expression of creatine kinase (ck), sulfinoalanine decarboxylase (csad), guanidinoacetate N-methyltransferase (gamt), glycine amidinotransferas (gatm), agmatinase (agmat), diamine oxidase1 (aoc1), and glutamate decarboxylase (gad) in the CRE1 group. Overall, these results suggested that dietary supplementation of creatine (0.5% − 2%) did not affect the growth performance, but it altered the gut microbial composition at the phylum and genus levels; it also increased the serum content of taurine by enhancing the activities of creatine metabolism and the CSA pathway, and increased the serum content of g-ABA by enhancing the activities of arginine metabolism, putrescine synthesis, and synthesis of g-ABA.