Upregulation of OGT-mediated EZH2 O-GlcNAcylation Promotes Human Umbilical Vein Endothelial Cell Proliferation, Invasion, Migration, and Tube Formation in Gestational Diabetes Mellitus

O-linked N-acetylglucosamine transferase (OGT)-catalyzed O-linked N-acetylglucosamine glycosylation (O-GlcNAcylation) is closely associated with diabetes progression. This study aims to investigate the mechanism of OGT in regulating endothelial dysfunction in gestational diabetes mellitus (GDM). Expressions of OGT, O-linked N-acetylglucosamine (O-GlcNAc), enhancer of zeste homolog 2 (EZH2), and HEK27me3 in human umbilical vein endothelial cells (HUVECs) and GDM-derived HUVECs (GDM-HUVECs) were assessed by western blot. RT-qPCR and western blot assays were used to test the OGT overexpression and EZH2 silencing levels. CCK-8, EdU, wound healing, and transwell invasion assays were used to analyze the cell proliferative, migratory, and invasive abilities. Tube formation assay was performed to evaluate angiogenesis ability of cells. Western blot assay was performed to estimate vascular endothelial growth factor (VEGF) and p-VEGFR2 levels in cells. The binding of O-GlcNAc and EZH2 after OGT overexpression was measured by Co-IP assay. The results showed that OGT, O-GlcNAc, EZH2, and HEK27me3 expressions were declined in GDM-HUVECs. OGT overexpression induced the proliferation, migration, and invasion of GDM-HUVECs, and also elevated angiogenesis and the expressions of VEGF and p-VEGFR2 in cells. O-GlcNAc, EZH2, and HEK27me3 expressions were upregulated after OGT overexpression. OGT upregulation induced the binding between O-GlcNAc and EZH2. EZH2 silencing attenuated the promotion of OGT overexpression on the proliferative, invasive, migratory, and angiogenic capacities of GDM-HUVECs. To be concluded, OGT overexpression stabilized EZH2 expression by promoting O-GlcNAcylation modification of EZH2, and further enhanced proliferation, migration, and invasion as well as angiogenesis of GDM-HUVECs. While these effects were decayed after EZH2 absenting. Overall, the modulation of OGT on endothelial dysfunction in GDM provides a novel perspective for the clinical treatment of GDM.