Protective effect of preconception high dose vitamin D3 supplementation in gestational diabetes mellitus rats via modulation of placental LCPUFA metabolism, one carbon cycle components, inflammation, oxidative stress, and angiogenesis.

Gestational diabetes mellitus (GDM), one of the most common pregnancy complications, adversely affects maternal and fetal health. This study investigated the impact of vitamin D3 (VD3) deficiency or supplementation on placental long chain polyunsaturated fatty acid (LCPUFA) metabolism, one-carbon cycle metabolites, inflammation, oxidative stress, angiogenesis, and birth outcomes in a GDM rat model. Wistar rats were divided into five groups: Control (1000 IU VD3/kg diet), Vitamin D Deficient (VDD, 0 IU VD3/kg diet), GDM (1000 IU VD3/kg diet + GDM), VD3 supplementation with 1500 IU (VDS-1500 +GDM), and VD3 supplementation with 10,000 IU (VDS-10,000 +GDM). GDM was induced using a high-fat, high-sugar diet and streptozotocin. Diets were provided from weaning through pregnancy. Only the VDS-10,000 +GDM group achieved sufficient serum 25(OH)D levels (>30 ng/ml). 10,000 IU/kg VD3 supplementation reduced gestational weight gain and improved fetal/placental weight ratios. It reduced the levels of FBS, fasting insulin, and HOMA-IR, while increased HOMA-IS. It regulated calcium homeostasis by decreasing parathyroid hormone and increasing phosphorous levels. It normalized one-carbon metabolites, reducing homocysteine and increasing folate levels. Both doses of VD3 supplementation mitigated oxidative stress, reducing malondialdehyde levels, which was higher in GDM and VDD groups. It restored LCPUFA profiles, increasing arachidonic acid and decreasing n-6 linoleic acid levels. High-dose VD3 reduced elevated plasma and placental TNF-α levels and downregulated IL-6 mRNA in the GDM group, while IL-6 protein levels remained comparable. The protein and mRNA levels of both VEGF and VEGF-R1 were higher in GDM group. 10,000 IU VD3 reduces VEGF levels whereas, 1500 IU VD3 reduces VEGF-R1 levels. High-dose VD3 supplementation (10,000 IU/kg) during pregnancy effectively improved vitamin D status and positively influenced placental metabolic pathways, oxidative stress, inflammation, and angiogenesis, thereby improving pregnancy outcomes in GDM.