Rapamycin administration during normal and diabetic pregnancy effects the mTOR and angiogenesis signaling in the rat placenta

Objective: The mammalian target of rapamycin (mTOR) signaling pathway has newly been recommended to be a nutrient sensor in the placenta. It is speculated that mTORC1 may be activated in diabetes, associated with increased placental nutrient availability. Thus, we aimed to investigate the mTOR signaling pathway both in diabetic and non-diabetic placenta and searched for the alterations of angiogenic factors VEGF, VEGFR1 and VEGFR2.

Methods: Streptozotocin (STZ) was administered by intravenous injection in doses of 60 mg/kg body weight and STZ injected rats were exposed to Everolimus (Rapamycin analog) and sacrificed at gestational days 14 and 20. mTORC1 and mTORC2 target proteins and angiogenic factors were analyzed at protein and mRNA levels in the placenta. Soluble VEGF A and İnsulin protein levels were determined in blood serum.

Results: Placenta and embryo weights were altered after STZ and/or Rapamycin administration. mTOR pathway inhibition was confirmed by decreased p70S6K (Thr389) phosphorylation levels. We found that maternal diabetic environment led to an increase in Akt phosphorylation at 14th and decrease at 20th gestational days. Serum levels of Insulin in 14 th and 20 th days of gestation were decreased in Rapamycin and diabetic groups. On the other side serum levels of Soluble VEGF were increased in 14 th and decreased in 20 th days of pregnancy.

Conclusion: According to our results, it might be suggested that angiogenesis related proteins will be related with placental growth regulation and mTOR may be a candidate pathway mediating the process in normal and diabetic pregnancy.