Abstract:

This study aimed to further explore the effect of taraxasterol on liver tissue oxidative stress cauesed by aflatoxin B₁ (AFB₁) in broiler chickens. One hundred and twenty broilers were randomly divided into six groups: normal group, model group, taraxasterol low-, medium- and high-dose groups (25, 50, 100 mg·kg^-1 BW) and positive group (300 mg·kg^-1 silibinin). Except the normal group, which was fed a basal diet, the other groups were fed a diet containing 0.5 mg·kg^-1 AFB₁ for 21 consecutive days to establish a liver injury model, the corresponding concentrations of medication were administered daily in drinking water during this period to each group. The body weight of broilers in each group were recorded and the feed-to-gain ratios were calculated; Liver function indexes asaspartate aminotransferase (AST), alanine aminotransferase (ALT), gamma-glutamyltransferase (GGT), total bilirubin (TBIL), alkaline phosphatase (ALP) in broilers were determined by kits. The contents of reactive oxygen species (ROS), malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), and glutathione (GSH) in broiler liver tissues were determined by kits. The expression of nuclear factor erythroid2-related factor 2 (Nrf2), Kelch-like ECH-associated protein 1 (Keap1) and heme oxygenase-1 (Heme Oxygenase-1), NAD(P) H: Quinone oxidoreductase-1 (NQO1) mRNA and protein in brolier liver were determined by RT-qPCR and Western blot. The results showed that the body weight was increased (P < 0.05) and the feed-to-weight ratio was decreased (P < 0.05) in broilers with AFB₁-induced liver injury at 14 and 21 days in the high dose group of taraxasterol. After 21 days, it was shown by the results that the activities of ALT (P < 0.05), AST (P < 0.01), GGT (P < 0.01), TBIL (P < 0.01), and ALP (P < 0.01), which are indicators of hepatic function, were reduced in the serum of broilers with AFB1-induced liver injury in the high dose group of taraxasterol. ROS and MDA content were inhibited (P < 0.01), while SOD (P < 0.01), CAT (P < 0.05) and GSH (P < 0.05) activities were increased in the liver of broilers with AFB1-induced liver injury in the high dose group of taraxasterol. The mRNA and protein expression levels of Nrf2 (P < 0.05), NQO1 (P < 0.01) and HO-1 (P < 0.05) were up-regulated. The mRNA (P < 0.05) and protein expression levels of Keap1 were down-regulated in the livers of broilers with AFB₁-induced liver injury in the high dose group of taraxasterol. In conclusion, taraxasterol can inhibit the overproduction of ROS and MDA and increase the content of antioxidants SOD, CAT, and GSH in broiler liver by regulating the Nrf2/Keap1 signaling pathway, enhance the hepatic antioxidant function, and significantly improve the liver function and growth performance, which can have a significant inhibitory effect on the oxidative damage caused by the induction of AFB₁.

Key words: AFB₁, taraxasterol, broilers, liver injury, oxidative stress