Chlorogenic acid improves common carp (Cyprinus carpio) liver and intestinal health through Keap-1/Nrf2 and NF-B signaling pathways: Growth performance, immune response and antioxidant capacity

In this experiment, we investigated the effects of adding chlorogenic acid (CGA) to the diet on growth performance, immune function, inflammation response, antioxidant capacity and its related mechanisms of common carp (Cyprinus carpio). A total of 600 fish were selected and randomly divided into five treatment groups and fed with CGA containing 0 mg/kg (CK), 100 mg/kg (L100), 200 mg/kg (L200), 400 mg/kg (L400) and 800 mg/kg (L800) for 56 days. The results of the experiment were as follows: addition of CGA significantly increased the WGR, SGR, FER, and PER of common carp (P < 0.05). The addition of 400-800 mg/kg of CGA significantly increased the serum levels of LZM, AKP activity, C3 and C4 concentration, and increased immune function of common carp (P < 0.05). Regarding antioxidant enzyme activities, adding CGA significantly increased SOD, CAT, and GsH-Px activities, while decreasing MDA content (P < 0.05). Compared with the CK group, the mRNA expression levels of NF-kappa B, TNF-alpha, and IL-1 beta were decreased. The IL-10 and TGF-beta were increased in the liver and intestines of the CGA supplemented group. Meanwhile, the addition of CGA also significantly up-regulated the mRNA expression levels of Nrf2, HO-1, SOD, CAT, and GPX (P < 0.05). CGA also positively contributed to the development of the carp intestinal tract, as demonstrated by decreased serum levels of DAO, D-LA, and ET-1. And the mucosal fold height was increased significantly with increasing levels of CGA. In conclusion, the addition of CGA in the feed can enhance the growth performance, immune function and antioxidant capacity of common carp, and improve the health of the intestine and liver. According to the results of this experiment, the optimal addition amount in common carp diets was 400 mg/kg.