High Glucose Increases IGF-2/H19 Expression by Changing DNA Methylation in HTR8/SVneo Trophoblast Cells.

Introduction: Gestational diabetes mellitus (GDM) is associated with many adverse outcomes of pregnancy, especially macrosomia. The aim of our study was to verify whether high glucose concentrations change the methylation levels of the insulin-like growth factor-2 (IGF-2)/H19 gene promoters to increase the expression of IGF-2, a key gene in fetal growth regulation. Methods: HTR8/SVneo cells were used to establish a cell model of intrauterine hyperglycemia in pregnant women with GDM. The RNA expression levels of the IGF-2/H19 genes and the methylation levels of the IGF-2/H19 gene promoter regions were measured. Methylated and unmethylated IGF-2/H19 gene promoter plasmids were transfected into HTR8/SVneo cells. Results: Among the five groups of cells, the RNA levels of IGF-2 and H19 were lowest in the 5-mM (physiological blood glucose level) group, which was statistically significant (all P < 0.05). Compared with those in the 5-mM group, two cytosine-phosphate-guanine (CpG) sites in the promoter region of the IGF-2 gene and twelve CpG sites in the promoter region of the H19 gene had statistically significant changes in methylation levels (all P < 0.05). Additionally, luciferase activity was significantly higher in cells transfected with the methylated H19 gene promoter plasmid than in control cells transfected with the unmethylated plasmid (P < 0.01), while the methylated IGF-2 gene promoter plasmid produced lower luciferase activity than the unmethylated plasmid (P < 0.01). Discussion: High glucose concentrations may increase IGF-2/H19 expression by changing the methylation levels of the IGF-2 and H19 gene promoters.