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 objective of this study was to investigate the potential effects of inulin on the immune capacity, antioxidant capacity, and intestinal microflora of spotted sea bass (Lateolabrax maculatus) fed a high-fat diet. A total of 360 juvenile spotted sea bass were randomly assigned to six groups, with each group having three replicates and each replicate consisting of twenty fish. The six groups included a Calvin Klein (CK) 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 indicate that the consumption of a high-fat diet leads to oxidative stress injury, reduced 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 (SOD) activity while reducing malondialdehyde acid (MDA)content. Notably, supplementation at a concentration of 1.5% also resulted in significant increases in levels of Complement 3 (C3) and Immunoglobulin M (IgM), while simultaneously improving the morphology of intestinal tissue. Moreover, the analysis at the phylum-level revealed that Bacteroidetes, Proteobacteria, and Firmicutes were the predominant bacterial groups found in the intestines of spotted sea bass. In terms of genus-level identification, Muribaculaceae, Citrobacter, and Prevotellaceae_UCG-001 were identified as dominant bacterial groups. The abundances of Bacteroidetes and Muribaculaceae initially increased but then decreased with increasing supplementation amounts. These results reveal that the use of INU in aquaculture has a positive effect on regulating the gut microbiota of the spotted sea bass, promoting its immunity and antioxidant capacity.