Activation of mtor signaling and increased nitric oxide metabolism in the placenta of rats with gestational diabetes

CAPOBIANCO E, RAMIREZ VI, FORNES D, POWELL TL, JANSSON T, JAWERBAUM A.

Mar del Plata

Congreso; VI SLIMP Latin American Symposium on Maternal Fetal Interaction and Placenta.; 2015

Gestational Diabetes Mellitus (GDM) is a prevalent disease that negatively impacts fetal and placental development. Mechanistic target of Rapamycin (mTOR) regulates important metabolic pathways related the placental transfer of nutrients and fetal growth. Nitric Oxide (NO) is a vasodilatory agent, and a substrate in the formation of peroxynitrites. Objective: Using a novel model of GDM in the rat, involving female offspring of pre-gestational diabetes or control mothers, we tested the hypothesis that mTOR is activated and NO overproduced in their placentas. Methods: Pregestational diabetes was generated by neonatal streptozotocin administration (F0). Female diabetic and control rats were mated with control males. Their female offspring (F1) were mated with control males. F1 females born to mothers with pre-gestational diabetes developed GDM. At day 21 of pregnancy, the placentas and fetuses from control and GDM rats were collected and weighed. The expression of proteins involved in mTORC1 (S6K1, RP-S6K1 and 4EBP1) and mTORC2 (SGK and PKCalpha) signaling pathways, were determined by Western blot in the placenta (total and phosphorylated proteins). Placental nitrates and nitrites (indicating NO production, by Griess reaction) and protein nitrotyrosylation (indicating peroxynitrite-induced damage, by immunohistochemistry) were determined. Results: Fetal weight was higher in the GDM group as compared to control (p<0.05), but there was no difference in placental weights. Placental expression of total 4EBP1 and PKCalpha, were decreased (p<0.05) in GDM compared to controls. Phosphorylation of 4EBP1 and PKCalpha were not changed. PhosphoSGK1 (ser422) expression was increased (p<0.001) in GDM placentas compared to controls, although no changes in the expression of total SGK1 were observed. GDM was associated with increased placental nitrates-nitrites and nitrotyrosylated proteins (p<0.05). Conclusions: In this novel GDM model, characterized by fetal overgrowth, we found evidence of activation of placental mTORC1 (decreased total 4EBP-1) and mTORC2 signaling (increased SGK1 phosphorylation). Because trophoblast mTOR stimulates protein synthesis and amino acid transport, these changes may contribute to increased fetal growth. Whether NO overproduction, consistent with GDM in women, is related to mTOR activation remains to be established.