Metformin increases norepinephrine transporter expression in placenta of patients with polycystic ovary syndrome

To evaluate the norepinephrine (NE) and placental NE transporter (NET) in women with polycystic ovary syndrome (PCOS) non-treated and treated with metformin during pregnancy.

We studied sixteen pregnant women with PCOS: 8 without metformin treatment during pregnancy (PCOS-M) and 8 treated with metformin during pregnancy (PCOS+M). Sixteen pregnant women of similar age without PCOS were included as controls (Control). At 24th and 35th weeks of pregnancy, blood samples were obtained. Placentas from full-term pregnancies were collected immediately after delivery. They were divided into two samples representative from the region near the chorionic plate (fetal side) and from the region near the basal plate (maternal side). NE plasma concentrations were measured by HPLC with electrochemical detection, and placental NET protein levels were determined by Western blot.

At week 24 of gestation, PCOS-M had higher NE plasma levels compared to control women (p < 0.001). Moreover, NET expression was lower in the maternal side of the placenta of PCOS-M compared to controls (p < 0.05). Metformin treatment normalized NE plasma levels at week 24 of gestation and NET expression in the maternal side of the placenta. In the fetal side of the placenta, NET expression was lower in PCOS-M and PCOS+M compared to control women (p < 0.001 and < 0.01, respectively).

Our results strongly suggest that norepinephrine homeostasis is altered in pregnant women with PCOS. Remarkably, metformin administration during pregnancy decreases circulating norepinephrine levels and increases NET expression in the maternal side of placentas from PCOS women.