Nuciferine supplement improved intestinal function and inflammatory response in juvenile large yellow croaker (Larmichthys crocea) fed diets with high palm oil level

The use of high dietary palm oil (PO) as a fish oil (FO) substitute in aquafeeds is known to induce intestinal damage and inflammatory responses in fish, yet effective mitigation strategies remain scarce. Although nuciferine (NF) has been demonstrated to enhance intestinal function and attenuate inflammation in mammals, its effects on the intestinal health in fish remain poorly understood. In this study, large yellow croakers were fed diets containing FO, PO or PO supplemented with 0.01 % NF, 0.05 % NF or 0.25 % NF. After 10 weeks, the in vivo results revealed that dietary PO diet reduced the intestinal villus heights and muscle thicknesses, but 0.05 % NF addition improved the intestinal villus heights and muscular thicknesses. Moreover, NF addition improved the PO diet-induced reduction of the mRNA expressions of mechanical barrier-related genes and the activities of mucosal barrier-related enzymes in the intestines of croakers. Furthermore, the in vivo results also showed that dietary PO diet promoted the mRNA expression levels of proinflammatory genes and the protein levels of mature IL-1β. However, 0.05 % NF addition inhibited the intestinal inflammatory response induced by the PO diet. Consistent with in vivo findings, NF treatment in vitro effectively attenuated palmitic acid (PA)-induced reduction of the intestinal barrier-related genes and induction of the proinflammatory gene expressions in croaker intestinal cells. In addition, the in vitro results also showed that the anti-inflammatory effect of NF was dependent on the inhibition of p38 MAPK pathway. Thus, our results suggest that NF has the potential to counteract PO-induced intestinal injury in fish.