Serum levels of mitochondrial uncoupling protein 1, leptin, and lipids during late pregnancy and the early postpartum period in mares.

The aim of this study was to investigate the changes of serum mitochondrial uncoupling protein 1 (UCP1) and leptin levels as well as of lipid and lipoprotein profiles in mares during the peripartum period. Ten pregnant mares (group A) were monitored from 15 ± 3 days of pregnancy until 15 days after foaling, and 10 nonpregnant nonlactating mares constituted the control (group B). In group A, blood sampling was performed on Days 15 ± 3 and 7 ± 3 before foaling, on the day of foaling, and on Days 7 and 15 after foaling. In group B, blood sampling was performed on the same days as in group A. Serum levels were determined for UCP1, leptin, total lipids, phospholipids, triglycerides, total cholesterol (Total-Chol), high-density lipoproteins, low-density lipoproteins (LDLs), and very low-density lipoproteins (VLDLs). Two-way repeated-measures ANOVA was applied to evaluate the effects of peripartum period and group membership. All studied parameters except phospholipid levels (P > 0.05) showed significant changes in group A over the peripartum period (P < 0.0001). A significant effect of pregnancy was found on all studied parameters (P < 0.001), which showed lower levels in group A than in group B for most of the time points considered. Significant negative correlations were found between UCP1 and total lipids, triglycerides, VLDLs, Total-Chol, and LDL values. Positive correlations were found between leptin and total lipids, triglycerides, VLDLs, Total-Chol, and LDLs. These changes observed in mares during the peripartum period could represent a response to hormonal and metabolic adaptations occurring during specific physiological conditions such as late pregnancy and early postpartum. These changes should compensate for the energy loss occurring during these particular life phases and ensure a good body condition to protect mares against negative energy balance.