Creatine supplementation in largemouth bass (Micropterus salmoides) diets: Improving intestinal health and alleviating enteritis.

Creatine plays an important role in regulating intestinal epithelial cell energy metabolism, epithelial integrity, and intestinal barrier function. In this study, three feeds with varying creatine concentrations (0 %, 0.5 %, and 4 %, labeled CR0, CR0.5, and CR4, respectively) were formulated and administered to juvenile largemouth bass (Micropterus salmoides) for 8 weeks. Creatine-containing diets significantly improved growth performance and intestinal villus height. Microbiota analysis revealed that creatine-containing diets changed the beta diversity of gut microbes and increased the relative proportion of Cetobacterium. Enteritis was induced for 7 days using the corresponding feeds containing creatine and 2 % DSS (labeled CR0, DCR0, DCR0.5, and DCR4). Enteritis resulted in an increase in hif1α expression in the DCR0.5 and DCR4 groups and a significant increase expression of creatine transporter SLC6A8. QPCR and Western blotting of intestinal barrier-related genes (e.g., Claudin1, Claudin4, and ZO1), MUC2 immunohistochemistry, and PAS mucus staining were used to show intestinal barrier status, these results suggest that dietary creatine attenuates the extent of intestinal barrier damage. After TUNEL and KI67 immunofluorescence analyses of the intestine and detection of the expression of relevant genes at the protein and transcript levels, the results showed that dietary addition of creatine significantly alleviated intestinal apoptosis and cellular inflammatory responses due to DSS-induced enteritis. These findings indicate long-term dietary supplementation with creatine modulated the microbial composition of the intestinal lumen of juvenile largemouth bass, promoted intestinal health, and improved anti-inflammatory properties following enteritis induction. This study provides a theoretical foundation for largemouth bass feed formulation optimization and fish enteritis control.