Role of placental glucose metabolism in steroidogenesis in healthy pregnancies at term

Abstract Background The human placenta consumes, on average, one third of the glucose from maternal blood. However, the role of placental glucose consumption in the production of estradiol and progesterone remains unclear. We hypothesized that placental glucose consumption in humans is associated with steroid production via a non-glycolytic pathway. Methods We included 41 healthy pregnancies at term. Blood samples were obtained from the maternal radial artery, uterine vein, and from the umbilical artery and vein during scheduled cesarean delivery. Blood flow in the uterine artery and umbilical vein was measured using Doppler ultrasound. Plasma concentrations of estradiol, progesterone, glucose, insulin, lactate, and ketones were analyzed. We calculated uteroplacental uptake and consumption of maternal glucose and ketones, and the loss of uteroplacental lactate in 6-carbon units as well as the release of steroid hormones into maternal circulation. Results Our data revealed a net placental release of estradiol and progesterone into maternal circulation [24.1 (5.34, 49.8) and 560.3 (61.2, 798.2) nmol/min, respectively]. The release of estradiol was positively associated with uteroplacental glucose uptake (ρ = 0.59, p < 0.001) and consumption (ρ = 0.43, p = 0.005), while progesterone exhibited similar associations (ρ = 0.61, p < 0.001; ρ = 0.43, p = 0.005). Notably, both hormones correlated positively with lactate-adjusted uteroplacental glucose consumption but not with acetate-equivalent uteroplacental ketone consumption. Conclusion Placental release of estradiol and progesterone correlates with uteroplacental consumption of glucose that primarily occurs via non-glycolytic pathways in the third trimester placenta.