Vitamin D deficiency in gestational diabetes mellitus and the role of the placenta

Objective The aim of this study was to evaluate the relationships between maternal vitamin D levels and gestational diabetes mellitus (GDM) and differences in the placental production of vitamin D receptor (VDR), CYP24A, and CYP27B1. Study Design Forty normal pregnant women and 20 women with GDM were included in this study. Serum levels of 25-hydroxyvitamin D (25[OH]D) were measured with enzyme-linked immunosorbent assay. The expression and production of VDR, CYP27B1, and CYP24A1 in the placenta were evaluated with real time-polymerase chain reaction and Western blot, respectively. Results We found that 27.5% of normal pregnant women and 85% of women with GDM had vitamin D deficiency, with serum 25(OH)D levels <20 ng/mL. Serum levels of 25(OH)D were lower in women with GDM than normal pregnant women (P <.01). The production of CYP24A1 protein and messenger RNA expression was significantly higher in placental tissue from patients with GDM than in those from normal pregnancies; however, the production of CYP27B1 and VDR protein and messenger RNA expression were not different between 2 the groups. Conclusion In this study, vitamin D deficiency was associated with GDM. Given that 25(OH)D is hydroxylated by CYP27B1 to the bioactive 1,25(OH)₂D form, and CYP24A1 catabolizes both 25(OH)D and 1,25(OH)₂D to the inactive metabolites, respectively, our data indicate that the elevated activity of CYP24A1 in the placenta may play a key role in the development of vitamin D deficiency in GDM.