The mammalian target of rapamycin (mTOR) couples’ energy and nutrient abundance to cell growth and is critically involved in the onset and progression of diabetes, cancer and ageing. Placental mTOR is involved in nutrient sensing and transfer to the fetus; animal models suggest that placental mTOR is upregulated in pregnancies complicated by hyperglycaemia (1). In this study we investigated expression patterns and activation of placental mTOR and possible effects of gestational diabetes (GDM). Our study consisted of GDM-mothers (n=28) and their offspring and ii) mothers (n=33) with normal pregnancies (non-GDM) and their infants. Total and phospho-mTOR (Ser2448) expression were determined in placental biopsies using either immunoblotting and immunohistochemistry (IHC) analysis. Newborn anthropometric parameters were also determined at delivery. GDM pregnant women presented with higher fasting glucose levels than non-GDM (98.12±22.82mg/dL; 73.61±9.89mg/dL; p<0.001). No significant difference was found in birth weight or baby length between GDM and non-GDM infants. IHC analysis showed that both total and activated mTOR were predominantly expressed in trophoblasts and to a lesser extend in syncytiotrophoblasts, in both GDM and non-GDM placentas. GDM placentas exhibited a higher mTOR H-score (2) compared to non-GDM (p<0.012), and WB analysis showed a higher phosphor-mTOR signal intensity (p=0.047) in the same group, most likely due to increased total mTOR expression. mTOR expression was also increased in both GDM syncytiotrophoblasts and endothelial cells compared to non-GDM (p<0.001) whereas a reduced signal was detected in stromal phospho-mTOR (p=0.004). No difference was found in trophoblasts or endothelial cells between the 2 study groups suggesting that activation of this kinase is tightly regulated and is relatively independent of changes in total kinase levels. Interestingly bivariate correlation analysis identified an extensive network of significant associations in the expression levels of total, phosphor-mTOR and P/T mTOR between trophoblasts, stroma, endothelial and syncytiotrophoblastsin control placental biopsies; this network was significantly disrupted in GDM placentas, identifying a disheveled regulation of placental mTOR activity. In conclusion, placental mTOR/PmTOR expression is differentially regulated across different placental cell types and is sensitive to hyperglycaemia associated with gestational diabetes mellitus.(1)M. Castillo-Castrejon and TL. Powell. Front Endocrinol (Lausanne). 2017; 8: 306. (2) E. Lakiotaki, et al., Scientific Reports 2016; 6, 21252.
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