Regulatory effects of brown adipose tissue thermogenesis on maternal metabolic adaptation, placental efficiency, and fetal growth in mice

To determine the role of UCP1-mediated thermogenesis in controlling maternal metabolic adaptation to pregnancy, energy metabolism of C57BL/6 wild-type (WT) and Ucp1 gene knockout (Ucp1(-/-)) mice was studied during pregnancy. With the progression of pregnancy, maternal energy expenditure rates (EERs), expression of UCP1, and core body temperature steadily declined in WT dams. Despite no significant alterations in core body temperature and weight gain during pregnancy, Ucp1(-/-) dams exhibited lower rates in EER decline. High-fat (HF) feeding not only robustly increased maternal UCP1 expression and core body temperature but also abolished gestation-suppressed EER in WT dams. However, HF-increased EERs were significantly attenuated in Ucp1(-/-) dams. Significantly increased fetal body weights and fetal/placental weight ratio were detected in fetuses from Ucp1(-/-) dams compared with fetuses from WT dams. Markedly increased expression levels of glucose transporter 1 and amino acid transporters were also observed in placentas from Ucp1(-/-) dams. Furthermore, blood glucose concentrations of fetuses from Ucp1(-/-) dams were significantly higher than those of fetuses from WT dams. indicating that maternal UCP1 has an inhibitory effect on placental efficiency and fetal growth. Taken all together, this study demonstrated that maternal brown adipose tissue plays an important role in controlling maternal metabolic adaptation and placental nutrient transport.