Changes in the expression of α-tocopherol-related genes in liver and mammary gland biopsy specimens of peripartum dairy cows

Blood alpha a-tocopherol (alpha-Toc) concentrations decline gradually throughout the prepartum period, reaching the nadir after calving in dairy cows. The 6 alpha-Toc-related molecules [alpha-Toc transfer protein (TTPA); afamin; scavenger receptor class B, Type I; ATP-binding cassette transporter Al; tocopherol-associated protein (SEC14L2); and cytochrome P450 family 4, subfamily F, polypeptide 2 (CYP4F2)] are expressed in liver and other peripheral tissues. These molecules could regulate alpha-Toc transport, blood concentrations, and metabolism of alpha-Toc. Therefore, the aim of this study was to evaluate the changes in the expression of alpha-Toc related genes in liver and mammary gland tissues of dairy cows around calving, which have remained elusive until now. In experiment (Exp.) 1, 28 multiparous Holstein cows were used (from -5 to 6 wk relative to parturition) to monitor the changes in dietary alpha-Toc intake, blood concentrations of alpha-Toc, and lipoproteins; in Exp. 2, 7 peripartum Holstein cows were used (from -4 to 4 wk relative to parturition) for liver tissue biopsy; and in Exp. 3, 10 peripartum Holstein cows were used (from -8 to 6 wk relative to parturition) to carry out the mammary gland tissue biopsy and milk sampling. In Exp. 1, the serum alpha-Toc concentrations declined gradually with decreasing amount of alpha-Toc intake and plasma high-density lipoprotein concentrations toward calving time. However, in the early lactation period after calving, serum alpha-Toc concentrations remained at a lower concentration despite the recovery of alpha-Toc intake and plasma high-density lipoprotein concentrations. In Exp. 2, just after calving, the TTPA, SEC14L2, afamin, and albumin mRNA expression levels in the liver were temporarily downregulated, and the hepatic mRNA levels of endoplasmic reticulum stress-induced unfolded protein response markers and acute-phase response marker increased at calving. In Exp. 3, the concentrations of alpha-Toc in colostrum were greater than those in precolostrum (samples were collected at wk -1 relative to parturition) and mature milk. The expression of TTPA, SEC14L2, arid CYP4F2 mRNA in bovine mammary gland tissue was detected. However, TTPA and SEC14L2 mRNA expressions showed the opposite trends: the expression levels of TTPA mRNA peaked whereas SEC14L2 mRNA reached a nadir at calving. These results indicate that the expression of alpha-Toc-related genes involved in specific alpha-Toc transfer and metabolism in the liver and mammary gland are altered during calving. Moreover, these changes might be associated with the maintenance of lower serum alpha-Toc concentrations after calving.