Effects of Dietary Mannan Oligosaccharides on Growth, Disease Resistance, and Gut Microbiota in Zebrafish

This study explored the multifaceted effects of mannan oligosaccharides (MOS) on the zebrafish intestine, focusing on growth, disease resistance, antioxidant capacity, histopathological alterations, immunological parameters, and gut microbiota. In zebrafish challenged with lipopolysaccharide (LPS) or dextran sulfate sodium (DSS), supplementation with 0.6% MOS for 4 weeks enhanced growth performance and disease resistance, along with increased survival rates. MOS improved antioxidant capacity by increasing superoxide dismutase and catalase levels in the intestine and upregulating the expression of antioxidant‐related genes. Histopathological examination revealed that MOS supplementation increased eosinophil and goblet cell counts and mitigated inflammation‐associated changes. Regarding immunological parameters, MOS suppressed proinflammatory cytokine expression and upregulated tight junction proteins, indicating immune‐modulating and barrier‐strengthening effects. Terminal deoxynucleotidyl transferase dUTP nick end labeling assays demonstrated that MOS decreased apoptosis in the intestinal segments of zebrafish challenged with LPS or DSS. In addition, MOS modulated the zebrafish gut microbiota by altering bacterial composition and increasing microbial diversity, suggesting its potential as a gut microbiota modulator. In conclusion, MOS emerges as a multifaceted dietary supplement with significant implications for zebrafish intestinal health, influencing growth, immunity, and gut microbiota composition. These findings enhance our understanding of dietary interventions and their roles in maintaining intestinal homeostasis.