Activation of mammaLian target of rapamycin signaLing pathway in pLacentaL tissues of gravidas with gestationaL diabetes meLLitus / 中华围产医学杂志

ABSTRACT

Objective To investigate the activation of mammalian target of rapamycin (mTOR) signaling pathway in placental tissues of gestational diabetes mellitus (GDM) women and in JEG3 cells after high glucose treatment. Methods Placental tissues were collected from 60 singleton pregnant women at term, who underwent elective cesarean section in Peking University First Hospital from December 2016 to June 2017, including 30 GDM women (GDM group) and 30 normal glucose tolerance (NGT) women (NGT group). Expressions of mTOR, Rictor, Raptor, S6 kinase (S6K) and phosphorylated-S6K (p-S6K), which were mTOR signaling pathway-related molecules in those placental tissues were detected by real-time fluorescence quantitative polymerase chain reaction, Western blotting and immunohistochemistry. At the same time, JEG3 cells were treated with glucose of different concentrations (5.5, 10.0, 15.0, 25.0 and 50.0 mmol/L) for 24 h, and the expressions of mTOR, S6K and p-S6K were detected by Western blotting. Two independent samples t-test, one-way analysis of variance test and Spearman correlation analysis were used for statistical analysis. ResuLts Compared with the NGT group, the pre-pregnancy body mass index(BMI), neonatal birth weight, fasting blood glucose(FBG), and 1 h and 2 h post-load blood glucose in oral glucose tolerance test (OGTT) of the GDM group were significantly increased [pre-pregnant BMI (21.6±2.7) vs (23.4±3.5) kg/m2, t= － 2.192; neonatal birth weight (3 337.5±347.7) vs (3 618.3±580.9) g, t=－2.727; FBG (4.6±0.4) vs (5.2±0.8) mmol/L, t=－3.947; 1 h glucose level (7.4±1.2) vs (9.6±1.9) mmol/L, t=－5.332; 2 h glucose level (6.3±1.0) vs (8.1±1.5) mmol/L, t=－5.314; all P<0.05]. The mRNA expressions of mTOR, Rictor and Raptor were significantly higher in the GDM group than in the NGT group (0.051±0.015 vs 0.031±0.011, t=－5.635; 0.038±0.017 vs 0.026±0.010, t=－3.485; 0.036±0.012 vs 0.025±0.011, t=－3.312; all P<0.05). The expression of mTOR, Rictor, Raptor and p-S6K protein in the GDM group were enhanced as compared with those in the NGT group (0.834±0.432 vs 0.386±0.361, t= － 2.249;0.589±0.236 vs 0.262±0.075, t= － 3.726; 0.767±0.345 vs 0.323±0.109, t= － 3.472; 1.847±1.025 vs 0.834±0.432, t=－2.575; all P<0.05). The results of immunohistochemistry also showed that the p-S6K in the placental tissues of the GDM group was higher than that of the NGT group (0.29±0.09 vs 0.18±0.08, t=－3.122, P=0.004). The expressions of mTOR protein (0.190±0.085, 0.301±0.089, 0.419±0.065, 0.562±0.108, 0.412±0.058, F=18.351, P<0.05) and p-S6K protein (0.753±0.150, 1.146±0.289, 2.148±0.188, 2.248±0.115, 2.134±0.214, F=66.242, P<0.05) in JEG3 cells treated with different concentrations of glucose (5.5, 10.0, 15.0, 25.0 and 50.0 mmol/L) were significantly different and increased with increasing concentrations of glucose (r=0.314, P=0.035; r=0.457, P=0.002). ConcLusions The up-regulated expressions of mTOR signaling pathway-related molecules in GDM placenta and high glucose-treated trophoblast cells (JEG3 cells) indicate a possible correlation between mTOR signaling pathway and GDM. However, the specific mechanisms need further study.