High-Dose Vitamin D Supplementation Significantly Affects the Placental Transcriptome

Abstract

Vitamin D deficiency is a highly prevalent obstetrical concern associated with an increased risk of complications like pre-eclampsia, gestational diabetes, and growth retardation. Vitamin D status in pregnancy is also linked to long-term offspring health, e.g., the risk of obesity, metabolic disease, and neurodevelopmental problems. Despite the suspected role of vitamin D in placental diseases and fetal development, there is limited knowledge on the effect of vitamin D on placental function. Thus, we performed next-generation RNA sequencing, comparing the placental transcriptome from uncomplicated term pregnancies receiving the often-recommended dose of 10 µg vitamin D/day (n = 36) with pregnancies receiving 90 µg/day (n = 34) from late first trimester to delivery. Maternal vitamin D status in the first trimester was also considered. We found that signaling pathways related to cell adhesion, immune function, and neurodevelopment were affected, supporting that increased vitamin D supplementation benefits placental function in established pregnancies without severe vitamin D deficiency, also underlining the importance of vitamin D in brain development. Specific effects of the first trimester vitamin D status and offspring sex were also identified. Further studies are warranted, addressing the optimal vitamin status during pregnancy with a focus on organ-specific vitamin D needs in individual pregnancies.

Keywords: NGS; immune function; placenta; pregnancy; vitamin D.

Figure 1

Principal component analysis of normalized expression in all 70 samples.

Figure 2

Volcano plot of differential expression analysis between the vitamin D-deficient/insufficient group (n = 28) against the vitamin D-sufficient group (n = 40) with correction for offspring sex. Highlighted in red are nominally significant DEGs with p < 0.001. Top ten most significant DEGs are marked with gene symbol labels, incl. six DEGs that remain significant after false discovery correction at 10% (C2, XIST, SKIC2, SQSTM1, RNU1-4, and PTH). The red dashed line represents a nominally significant cut-off of p = 0.05.

Figure 3

Differential expression analysis between the 90 µg vitamin D group and the 10 µg group with correction for sex. (a) Volcano plot of differential expression analysis. Highlighted in red are nominally significant DEGs with p < 0.001. Top ten most significant DEGs are marked with gene symbol labels, incl. three DEGs that remain significant after false discovery correction at 10% (EIF3K, TDRD12, and JPH1). The red dashed line represents a nominally significant cut-off of p = 0.05. (b) Heatmap of normalized expression values of nominally significant DEGs with p < 0.001 with hierarchical clustering applied. (c) Gene set enrichment analysis of nominally significant DEGs with p < 0.001 against GO terms. (d) Gene set enrichment analysis against the GWAS catalogue.

Figure 4

Heatmaps of normalized expression values of the nominally significant DEGs with p < 0.001 with hierarchical clustering applied for (a) placental samples from pregnancies with male offspring (42 DEGs) and (b) placental samples from pregnancies with female offspring (52 DEGs).