Dietary conjugated linoleic acid supplementation alleviates high lipid-induced intestinal damage in grass carp (Ctenopharyngodon idella)

High lipid diet has been shown to increase the intestinal permeability and inflammatory properties in mammals, and the conjugated linoleic acid (CLA) could alleviate the symptoms caused by high lipid diet. However, the information about the impact of high lipid diet on the intestine of fish was limited, and the effect of CLA on intestinal changes induced by high lipid diet in fish is still unknown. Therefore, an 8-week feeding trial was conducted to investigate CLA's potential effects against high lipid diet-induced intestinal physical and immune barrier damage in grass carp (Ctenopharyngodon idella). Three isonitrogenous diets, including fish meal-control diet, control diet supplemented with 3.5% soybean oil as high lipid diet (HL), and HL replaced with a 2.5% CLA diet (CLA) formulated. Compared to the control group, HL significantly increased the expression of pro-inflammation genes (TNF-α, IL-8, IL-1β, NF-κB p65, IκBα, IKKα, IKKβ, and IKKγ) and down-regulated the gene expression of anti-inflammation cytokine (IL-10). The expression of intestinal tight junction proteins (ZO-1, occludin, claudin c, and claudin b) in fish fed with high lipid diets was lower than those fed with control diets. In the CLA group, the gene expression of pro-inflammation cytokines was decreased, and the expression level of the anti-inflammation cytokine was increased, compared with those in HL group. Moreover, feeding with high lipid diets induced fish intestine and dietary CLA damage could alleviate the symptom as shown by HE staining. In conclusion, this research revealed that CLA could mitigate high lipid diet-induced inflammation and permeability in the intestine of grass carp