Maternal plasma leptin concentration is significantly increased during pregnancy. However, its roles in pregnancy, especially in labor, have not been fully clarified. We measured plasma leptin concentrations in pregnant women during the course of induced labor, just after spontaneous vaginal delivery and Cesarean section at term. We also studied the regulation of leptin secretion from term placental tissue and BeWo cells, a trophoblastic cell-line. Plasma leptin concentrations increased significantly during labor (58.9 ± 9.2 ng/ml) compared to those before labor induction (37.5 ± 5.8 ng/ml, P<0.05), then decreased 3-6 days postpartum (14 ± 3 ng/ml, n = 6, P<0.0001) to the levels of normal nonpregnant women. Leptin concentrations within an hour and 24 hours after spontaneous vaginal delivery were significantly higher than those after Cesarean section (P<0.05 for both comparisons). Similarly, leptin mRNA expression in placental tissues obtained after spontaneous vaginal delivery was significantly greater than that in those obtained after Cesarean section without labor (P<0.05). IL-1α and TNF-α treatment significantly stimulated leptin secretion and leptin mRNA expression in explant culture of human term placental tissue and in BeWo cells as compared with those in vehicle controls (P<0.05, for all comparisons). By contrast, oxytocin and prostaglandin F2α treatment had no effects on leptin secretion from explant culture of human term placental tissue or from BeWo cells. These data indicate that pro-inflammatory cytokines might stimulate placental leptin secretion, thus finally contributing to the increase in plasma leptin concentration during labor.
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