Dietary bile acids alleviate dextran sulfate sodium-induced enteritis in juvenile leopard coral grouper (Plectropomus leopardus)

Enteritis is a common disease in leopard coral grouper reared under intensive aquaculture conditions. We developed an enteritis model by feeding fish with 0.75 % dextran sulfate sodium (DSS) diet for one week, followed by a three-week period with diets containing graded bile acids levels (0 %, 0.15 %, 0.30 %, 0.45 %, 0.60 %). They were designated as DSSBA0, DSSBA15, DSSBA30, DSSBA45, and DSSBA60, with an control group received no DSS treatment. The results showed that growth performance was significantly impaired in the DSSBA0 group compared with the control group (P < 0.05), while it improved markedly as the bile acids levels increased (P < 0.05). Intestinal indices were significantly enhanced in the dietary bile acids groups, particularly in the DSSBA60 group (P < 0.05). Meanwhile, bile acids supplementation ameliorated DSS induced intestinal damage, including villus atrophy and reduced muscular layer thickness. Moreover, the gene expression of tight junction proteins (zo1, zo2, zo3, occludin and claudin-1) were significantly increased in higher bile acids treatment groups compared with the DSSBA0 group (P < 0.05). Furthermore, gene expression analysis indicated that pro-inflammatory cytokines (tnf-α, inf-γ, il-1β, il-6, il-8) were down-regulated, while the anti-inflammatory cytokine il-10 was up-regulated in the higher bile acids groups (DSSBA45 and DSSBA60) compared with the DSSBA0 group (P < 0.05). And the activities of enzymes associated with intestinal inflammation, including myeloperoxidase (MPO) and β-N-acetyl-D-glucosaminidase (NAG), were significantly reduced in the groups supplemented with bile acids. Microbial diversity analysis through 16S rRNA sequencing indicated that dietary bile acids notably increased the abundance of Firmicutes and Candidatus-Arthromitus. The above findings provide strong evidence that bile acids effectively alleviate enteritis in leopard coral grouper by preserving intestinal integrity, modulating inflammatory responses, and enhanced beneficial bacteria abundance. These findings provide a novel nutritional strategy for improving gut health in aquaculture, offering valuable insights for sustainable fish farming.