Study of vitamin D receptor gene methylation and the risk of gestational diabetes mellitus in Iranian pregnant women

Vitamin D acting through vitamin D receptor (VDR) plays a crucial role in regulating multiple pathways, including immunomodulatory properties, insulin secretion, and calcium homeostasis. Gestational diabetes mellitus (GDM) is a metabolic disorder with glucose intolerance that occurs in pregnancy. It has been lately suggested that epigenetic mechanisms as well as genetic factors have a significant role in GDM pathogenesis. Our study's intention was to investigate the methylation pattern of CpG islands of the VDR gene promoter in GDM and non-GDM population and predisposition to GDM in Iranian pregnant women. A total of 240 of pregnant Iranian women including, 120 women with GDM and 120 non-GDM were recruited in this study. Diagnosis of GDM was confirmed via a 75 g oral glucose tolerance test (OGTT) at 24-28 weeks of pregnancy. Peripheral blood DNA was isolated and underwent chemical modification using sodium bisulfite. The status of VDR promoter methylation of was determined by methylation-specific PCR (MSP). Analysis of MSP data uncovered the unmethylated promoter of VDR gene both in GDM and non-GDM pregnant women. Indeed, we found no differences in the DNA methylation patterns of the VDR promoter between GDM and non-GDM groups. Our study was the first report of VDR promoter methylation in GDM. In conclusion, we found no significant association between methylation status of VDR promoter and susceptibility to GDM in our studied population.