Intestinal immune function, antioxidant status and tight junction proteins mRNA expression in young grass carp (Ctenopharyngodon idella) fed riboflavin deficient diet.

This study investigated the effects of riboflavin on intestinal immunity, tight junctions and antioxidant status of young grass carp (Ctenopharyngodon idella). Fish were fed diets containing graded levels of riboflavin (0.63-10.04 mg/kg diet) for 8 weeks. The study indicated that riboflavin deficiency decreased lysozyme, acid phosphatase, copper/zinc superoxide dismutase, glutathione reductase and glutathione peroxidase activities, and contents of complement component 3 and reduced glutathione in the intestine of fish (P < 0.05). Meanwhile, riboflavin deficiency increased reactive oxygen species, malondialdehyde and protein carbonyl contents and catalase activity (P < 0.05) in the intestine of fish. Furthermore, real-time polymerase chain reaction analysis was used to investigate mRNA expression patterns and found that the mRNA levels of interleukin 10 and transforming growth factor β1, Occludin, zonula occludens 1, Claudin-b and Claudin-c, inhibitor protein κBα, target of rapamycin, ribosomal S6 protein kinase 1 and NF-E2-related factor 2, copper/zinc superoxide dismutase, glutathione peroxidase and glutathione reductase were decreased (P < 0.05) in the intestine of fish fed riboflavin-deficient diet. Conversely, the mRNA levels of tumor necrosis factor α, interleukin 1β, interleukin 8, nuclear factor kappa B p65, Ikappa B kinase β, Ikappa B kinase γ, Kelch-like-ECH-associated protein 1b, p38 mitogen-activated protein kinase, myosin light chain kinase and Claudin-12 were increased (P < 0.05) in the intestine of fish fed riboflavin-deficient diet. In conclusion, riboflavin deficiency decreased immunity and structural integrity of fish intestine. The optimum riboflavin level for intestinal acid phosphatase activity of young grass carp was estimated to be 6.65 mg/kg diet.