Increased Expression of Aquaporin 9 in Trophoblast From Gestational Diabetic Patients.

Gestational diabetes mellitus is the most frequent pathophysiological alteration in pregnancy, increasing the incidence of complications in both mother and fetus. The macrosomia that occurs in these fetuses may be related with some changes in nutrient transport mechanism in placenta. The presence of aquaporin 9, an aquaglyceroporin, has previously been demonstrated in placenta. We raised the question whether aquaporin 9 expression may be upregulated in placenta from gestational diabetes, thus providing a faster transport of glycerol and water through placenta. We studied 21 placentas (13 controls and 8 gestational diabetes) from cesarean delivery at term. The expression of aquaporin 9 was analyzed by quantitative PCR, immunoblot, and immunohistochemistry. The median values from quantitative PCR were compared by nonparametric tests for independent samples (Mann-Whitney U-test). We have found that trophoblast from gestational diabetes express higher amount of aquaporin 9, which was found statistically significant (p<0.05). The increase in aquaporin 9 expression was confirmed by immunoblot, and localization in the syncytiotrophoblast was checked by immunohistochemistry. The increase in aquaporin 9 expression in placenta from gestational diabetes may contribute to the higher transport rate in this pathology of pregnancy.

Insulin and Leptin Signaling in Placenta from Gestational Diabetic Subjects.

Insulin and leptin receptors are known to share signaling pathways, such as JAK2/STAT-3 (Janus kinase2/signal transduction and activator of transcription3), MAPK (Mitogen activated protein kinase), and PI3K (phosphoinositide 3-kinase). Both positive and negative cross-talk have been previously found in different cellular systems. Gestational diabetes (GDM) is a pathophysiological state with high circulating levels of both insulin and leptin. We have previously found that these 3 signaling pathways are activated in placenta from GDM patients to promote translation, involving the activation of leptin receptor. Now, we have tested the hypothesis that both leptin and insulin receptors might contribute to this activation in a positive way that may become negative when the system is overactivated. We studied the activation of leptin and insulin receptors in placenta from GDM and healthy pregnancies. We have also performed in vitro studies with insulin and leptin stimulation of trophoblast explants from healthy placenta. We have found that both leptin and insulin receptors are activated in placenta from GDM. In vitro stimulation of trophoblast explants with both leptin and insulin at submaximal doses (0.1 nM) potentiated the activation of signaling, whereas preincubation with maximal concentrations of insulin (10 nM) and further stimulation with leptin showed negative effect. Trophoblastic explants from GDM placenta, which presented high signaling levels, had a negative signaling effect when further incubated in vitro with leptin. In conclusion, insulin and leptin receptors have positive effects on signaling, contributing to high signaling levels in GDM placenta, but insulin and leptin have negative effects upon overstimulation.

Activated translation signaling in placenta from pregnant women with gestational diabetes mellitus: possible role of leptin.

Placentas from gestational diabetes (GDM) suffer from structural and functional changes including overgrowth. That is why we aimed to study [³H]-leucine incorporation into protein in addition to translation signaling in placenta from GDM. Thus, we investigated the expression of leptin and leptin receptor (LEPR), as well as the activation state of signaling proteins regulating protein synthesis, such as mTOR, S6 Kinase, EIF4E-BP1, EIF4E, and eEF2 by measuring protein phosphorylation by immunoblot. [³H]-Leucine incorporation into protein also was determined in trophoblastic placenta explants from GDM and control pregnancy. We found that leptin and LEPR expression are increased in placentas from GDM and the translation machinery activity as well as [³H]-leucine incorporation into protein were higher in placentas from GDM compared with placentas from control pregnancy. In conclusion, protein synthesis rate is increased in placenta from GDM patients, and this may be due, at least in part, by the activation of translation signaling. The increased expression of leptin and LEPR may contribute to these effects. These results may provide a possible mechanism for the previously observed increase in placenta growth in GDM.