Potential effects of inulin as a dietary supplement on immunity, antioxidant and intestinal health of spotted sea bass (Lateolabrax maculatus) fed a high-fat diet

The aim of this study was to investigate the potential effects of inulin on immune capacity, antioxidant capacity, and intestinal microflora in spotted sea bass fed a high-fat diet. A total of 360 juveniles were randomly assigned into six groups with three replicates per group and twenty fish per replicate. The six groups included a CK (Calvin Klein) group fed a normal fat diet, a group fed a high-fat diet (HF), and four groups fed a high-fat diet supplemented with 0.5% (G1), 1% (G2), 1.5% (G3), and 2% (G4) inulin, respectively. The experiment lasted for ten weeks. The results indicated that consumption of a high-fat diet resulted in oxidative stress injury, decreased immunity, abnormal intestinal histopathology, and an imbalance in intestinal flora in spotted sea bass compared to the CK group. However, compared to the HF group, supplementation with inulin significantly increased superoxide dismutase activity while decreasing malondialdehyde content. Notably, supplementation at 1.5% also led to significant increases in Complement 3 (C3) and Immunoglobulin M (IgM) levels while improving intestinal tissue morphology. Furthermore, phylum-level analysis revealed that Bacteroidetes , Proteobacteria and Firmicutes were the main bacterial groups found within the intestines of spotted sea bass. In terms of genus-level identification, Muribaculaceae , Citrobacte and Prevotellaceae_UCG-00 1 were identified as dominant bacterial groups. The abundances of Bacteroidetes and Muribaculaceae in the inulin group initially increased but then decreased with increasing supplementation amounts.