miR-520h Inhibits cell survival by targeting mTOR in gestational diabetes mellitus

Gestational diabetes mellitus (GDM) is a type of diabetes that occurs during pregnancy due to abnormal maternal glucose metabolism. This study aimed to investigate the effect of miR-520h and its potential target gene on the progression of GDM. The blood samples were taken from healthy pregnant women and GDM patients. Human villous trophoblasts HTR-8/SVNEO cells were treated with 25 mM glucose and were considered as the GDM cell model. The miR-520h level was detected using qRT-PCR in the serum and GDM cell model. The correlation analysis between fasting blood-glucose (FBG) level and miR-520h expression was analyzed. The target relationship between miR-520h and mTOR was verified using dual luciferase reporter assay. HG-induced cells were transfected with miR-520h mimic or miR-520h inhibitor and pCDNA3-mTOR vector or their NCs. Cell viability, apoptosis and mTOR expression level were detected using CCK-8, flow cytometry and western blotting, respectively. The results showed that the miR-520h serum level was up-regulated in the GDM patients' serum and GDM cell model, and was positively correlated with FBG of GDM patients. High glucose (HG) inhibited HTR-8/SVNEO cell viability and decreased mTOR expression, while it promoted apoptosis. Then, the effects of HG on HTR-8/SVNEO cells were reversed by miR-520h inhibitor. Moreover, mTOR was identified as a target gene downstream of miR-520h. The overexpression of mTOR alleviated miR-520h mimic-induced reduction in cell viability and enhancement in cell apoptosis in the GDM cell model. In conclusion, miR-520h could inhibit cell viability and promote cell apoptosis by regulating mTOR expression in the GDM cell model. Hence, miR-520h might be a potential and important marker for the diagnosis and treatment of GDM.