Abstract: Objective　To investigate the expression of microRNA (miR)-199a in gestational diabetes mellitus (GDM) and the mechanism of silent mating type information regulator 2 homolog 1/forkhead box transcription factor O1 (SIRT1/FOXO1) pathway involved in insulin resistance (IR). Methods　A total of 56 GDM pregnant women were selected as the research objects (GDM group), and 60 normal pregnant women were selected as the control group. Real-time fluorescence quantitative PCR (qPCR) was used to detect the level of miR-199a in placenta. The insulin resistance index (HOMA-IR) was calculated. Pearson method was used to analyze the correlation between miR-199a and HOMA-IR. Human beings chorial trophcytes HTR-8/SVneo cells were cultured in vitro, and IR model was made. The function of miR-199a was verified. Cells were divided into the model group, the miRNA inhibitor NC group, the miR-199a inhibitor group, the miRNA mimic NC group and the miR-199a mimic group. The expression levels of miR-199a were detected by qPCR in each group. The intracellular glucose uptake was measured by anthrone method. The levels of superoxide dismutase (SOD) and malondialdehyde (MDA) were detected by kit. The protein levels of SIRT1, FOXO1 and acely (Ac)-FOXO1 were detected by Western blot assay. The double luciferase reporter gene assay was used to identify the targeting relationship between miR-199a and SIRT1. Results　Compared with the normal pregnant women, the levels of miR-199a and HOMA-IR in placenta were higher in GDM patients (P＜0.05), and there was a positively correlation between miR-199a level and HOMA-IR (P＜0.05). The combined action of palmitic acid and insulin on cells for 24 h could establish an IR model. Compared with the model group and the miRNA inhibitor NC group, the levels of miR-199a and MDA were decreased in the miR-199a inhibitor group, while the levels of glucose uptake, SOD and SIRT1 protein were increased (P＜0.05). Compared with the model group and the miRNA mimic NC group, the levels of miR-199a, Ac-FOXO1 protein and MDA were increased in the miR-199a mimic group, while the levels of glucose uptake and SIRT1 protein were decreased (P＜0.05). Tarbase database analysis showed that miR-199a and SIRT1 had complementary binding sites, which were verified by double luciferase. Conclusion　The level of miR-199a in placenta is highly expressed in GDM patients. The increased miR-199a can promote FOXO1 acetylation by targeting down-regulation of SIRT1, relulting in IR.

Key words: diabetes, gestational, microRNAs, Forkhead box protein O1, microRNA-199a, silent information regulator 1/forkhead transcription factor O1 pathway, insulin resistance