Effects of antioxidant vitamins and trace minerals on the pro-inflammatory status and liver insulin signaling pathway of transition dairy cows

This study aimed to evaluate the impact of parenteral vitamin and mineral supplementation on the systemic and hepatic inflammatory status and intracellular insulin signaling pathway in the liver of dairy cows during the transition period. The supplemented group (SG; n = 11) received subcutaneous injections of 5 mL of vitamin A palmitate (35 mg/mL) and vitamin E acetate (50 mg/mL) and 5 mL of a mineral solution containing copper edetate (10 mg/mL), zinc edetate (40 mg/mL), manganese edetate (10 mg/mL) and sodium selenite (5 mg/mL) on days -60, -30, and 7 (± 3) relative to calving. The control group (CG; n = 11) received placebo injections (5 mL of 9 mg/mL sodium chloride) at the same time points. Blood and liver samples were collected -21 (±3) days before the expected calving date and on days 7 (±3) and 21 (±3) after calving. On day 21 post-calving, serum insulin concentrations were significantly higher in the SG than in the CG. Moreover, serum concentrations of some mediators of inflammatory response as IL-1β and IL-6 were lower in the SG. In the liver, the SG showed reduced IL-6 protein abundance on day 7 post-calving and decreased NF-κB phosphorylation compared to the CG. However, no significant differences were observed between groups in the phosphorylation status of key proteins involved in the insulin signaling pathway. These findings suggest that parenteral vitamin and mineral supplementation in transition dairy cows exerts anti-inflammatory effects both systemically and locally in the liver; however, these changes were not accompanied by activation of the hepatic insulin signaling pathway.