Abstract
The purpose of this experiment was to investigate high-concentrate feeding-induced changed status of oxidative and autophagy in the livers of dairy cows. Hepatocyte nuclear factor 3β (FOXA2) was reported in cases of liver fibrosis, glucolipid metabolism, and hepatocyte differentiation, but not in cases liver damage in cows fed a high-concentrate diet. Therefore, we also aimed to explore the potential role of FOXA2 in SARA-induced liver damage. We divided 12 mid-lactating Holstein cows into 2 groups and fed them a high-concentrate (HC group, forage:concentrate = 4:6) and a low-concentrate (forage:concentrate = 6:4) diet. After a 2-wk adaptation period and a 3-wk experimental period, peripheral blood was collected for determination of antioxidant enzyme activity, and liver tissue was collected to examine genes and proteins. On d 20 and 21 of the experiment, rumen fluid was collected, and the pH was measured. A significant difference in rumen fluid pH was found between the 2 groups (low-concentrate: 6.10 ± 0.07 vs. HC: 5.59 ± 0.09). The rumen fluid pH in the HC group was less than 5.6 at 2 time points, indicating that SARA was successfully induced. Lipopolysaccharide (0.24 ± 0.10 vs. 0.42 ± 0.12) and malondialdehyde (1.46 ± 0.25 vs. 2.94 ± 0.65) increased, whereas superoxide dismutase (14.06 ± 0.63 vs. 11.71 ± 0.64), reduced glutathione (14.48 ± 2.25 vs. 6.82 ± 0.67), and the total antioxidant capacity (0.43 ± 0.03 vs. 0.30 ± 0.03) decreased in the peripheral blood of the HC group. Moreover, in liver tissue from the HC group, catalase (0.71 ± 0.03 vs. 0.49 ± 0.03) and superoxide dismutase (27.46 ± 1.90 vs. 20.32 ± 1.54) were decreased, whereas malondialdehyde (0.21 ± 0.03 vs. 0.28 ± 0.03) was elevated. Meanwhile, we observed lower gene expression of CAT (1.00 ± 0.15 vs. 0.64 ± 0.17), NAD(P)H quinone dehydrogenase 1 (NQO1; 1.00 ± 0.09 vs. 0.47 ± 0.14), glutathione peroxidase 1 (GPX1; 1.03 ± 0.27 vs. 0.55 ± 0.09), SOD1 (1.01 ± 0.17 vs. 0.76 ± 0.17), and SOD3 (1.02 ± 0.21 vs. 0.55 ± 0.16) in the liver tissue of the HC group. Furthermore, western blot analysis showed that high-concentrate feeding led to decreased sirtuin-1 (SIRT1) (1.00 ± 0.10 vs. 0.62 ± 0.15) and FOXA2 (1.02 ± 0.19 vs. 0.68 ± 0.18), elevated autophagy-related protein microtubule associated protein 1 light chain 3 II (MAP1LC3-II; 1.00 ± 0.32 vs. 1.98 ± 0.83) and autophagy related 5 (ATG5; 1.00 ± 0.30 vs. 1.80 ± 0.27), and suppressed antioxidant signaling pathway-related protein nuclear factor erythroid 2-like 2 (NFE2L2; 1.00 ± 0.18 vs. 0.61 ± 0.30) and heme oxygenase 1 (HMOX1; 1.00 ± 0.48 vs. 0.38 ± 0.25) in liver tissue. Overall, these data indicated that SARA elevated systematic oxidative status and enhanced autophagy in the liver, and suppressed SIRT1 and FOXA2 may mediate enhanced oxidative damage and autophagy in the livers of dairy cows fed a high-concentrate diet.