Higher levels of vitamin D binding protein (DBP) at the time of delivery, but not during the middle of pregnancy, were associated with a lower risk for type 1 diabetes (T1D) in offspring, according to findings published in Diabetes Care.

It has been suggested that vitamin D, vitamin D receptor, vitamin DBP, and genetic polymorphisms may influence the risk for T1D developing. However, there have not been any studies to date that have analyzed these factors jointly. In the current paper, researchers investigated whether vitamin DBP levels during pregnancy or at birth were associated with the development of T1D in the child and whether vitamin D pathway genetic variants modified associations between DBP, 25-hydroxy vitamin D (25[OH]D), and T1D. The cohort included 189 mother/child pairs in which T1D developed subsequently in the offspring and 576 mother/child control pairs from a random sample. To account for T1D susceptibility genotype markers, several single nucleotide polymorphisms in the vitamin D pathway underwent genotyping, including 2 near the vitamin D receptor gene (rs1544410 and rs11568820).

The results showed that only higher maternal vitamin DBP levels at delivery, but not at other times during the pregnancy, were associated with a decreased risk for T1D in the child (odds ratio for each 1 µmol/L increase, 0.86; 95% CI, 0.74-0.98). Higher levels of 25(OH)D in cord blood were also associated with lower T1D risk (odds ratio for each 10 nmol/L increase, 0.87; 95% CI, 0.77-0.98) but only in children homozygous for the vitamin D receptor rs11568820 G/G genotype (P =.01 for interaction between 25(OH)D level and rs11568820). No other gene-environment interactions were observed.

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Overall, the decreased risk for T1D associated with higher 25(OH)D levels at birth in children carrying the vitamin D receptor rs11568820 G/G genotype “supports the current recommendations for vitamin D intake for pregnant women and infants,” wrote the researchers. “These findings must be interpreted with caution, and more evidence is required to validate these results. Regardless, potential future vitamin D studies should consider including [the vitamin D receptor] genotype.”

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Reference

Tapia G, Mårild K, Dahl SR, et al. Maternal and newborn vitamin D-binding protein, vitamin D levels, vitamin D receptor genotype, and childhood type 1 diabetes [published online January 28, 2019]. Diabetes Care. doi:10.2337/dc18-2176