Abstract
Enhancing the supply of rumen-protected Met (RPM) during the peripartum period alleviates inflammation and oxidative stress status in dairy cows. We tested the hypothesis that RPM could increase abundance of genes and proteins related to glutathione (GSH) metabolism and the antioxidant transcription factor nuclear factor erythroid 2-like 2 (NFE2L2) in subcutaneous adipose tissue. Multiparous Holstein cows were fed a basal diet [control prepartum diet = 1.47 Mcal/kg of dry matter (DM) and 15.3% crude protein; control postpartum diet = 1.67 Mcal/kg of DM and 17.7% crude protein] or the control plus ethyl-cellulose RPM at a rate of 0.09 and 0.10% of DM intake before expected calving and after calving, respectively. Sixty cows were assigned to treatments based on parity, previous 305-d milk yield, and body condition score at 28 d from parturition. Diets were fed from -28 to 30 d. Biopsies of subcutaneous adipose tissue collected on d -10, 10, and 30 relative to parturition from 7 cows in each group were used for measuring concentrations of GSH, reactive oxygen species, superoxide dismutase, malondialdehyde, and mRNA and protein abundance (Western blotting). A repeated-measures ANOVA was used for statistics. The statistical model included the random effect of block and fixed effects of treatment, time, and its interaction. There was a diet × time effect for reactive oxygen species due to lower concentrations in Met versus control cows specifically at d -10. Cows fed Met also had lower concentrations of malondialdehyde in subcutaneous adipose tissue. Compared with controls, overall mRNA abundance of the GSH metabolism-related genes cystathionine-β-synthase (CBS), glutamate-cysteine ligase modifier subunit (GCLM), glutathione reductase (GSR), and glutathione peroxidase 1 (GPX1) was greater in cows fed Met. Furthermore, supply of Met resulted in an overall upregulation of protein abundance of glutathione peroxidase (GPX) 1, GPX3, glutathione S-transferase mu 1 (GSTM1), and glutathione S-transferase α 4 (GSTA4), all related to GSH metabolism. There was a diet × time effect for protein abundance of NFE2L2 and its repressor Kelch-like ECH associated protein 1 (KEAP1) due to lower values at 30 d in cows fed Met versus controls. The abundance of phosphorylated NFE2L2 was lower at 30 d in response to Met. Overall, the data suggest that exogenous Met may play a role in activating GSH metabolism and the antioxidant NFE2L2 pathways in subcutaneous adipose tissue.