Gene-specific DNA methylation in newborns in response to folic acid supplementation during the second and third trimesters of pregnancy: epigenetic analysis from a randomized controlled trial

Background: Emerging evidence suggests that maternal folate status can impact cognitive development in childhood. Folate-dependent DNA methylation may provide a biological mechanism to link folate status during pregnancy with cognition in the offspring. Objective: The objective was to investigate the effect of continued folic acid (FA) supplementation beyond the first trimester of pregnancy on DNA methylation in cord blood of epigenetically-controlled genes related to brain development and function. Design: Using available cord blood samples (n = 86) from the Folic Acid Supplementation in the Second and Third Trimesters (FASSTT) trial in pregnancy, we applied pyrosequencing techniques to analyze cord blood DNA at nine candidate loci known to be regulated by methylation including some previously implicated in observational studies: the widely-dispersed retrotransposon LINE-1 and eight single-copy loci (RBM46, PEG3, IGF2, GRB10, BDNF, GRIN3B, OPCML and APC2). Results: The newborns of mothers who received FA (400 µg/d) during pregnancy, compared to placebo, had significantly lower overall DNA methylation levels at LINE-1 (57.2 ± 2.1 % vs 56.3 ± 1.7 %; P = 0.024), IGF2 (51.2 ± 5.1 % vs 48.9 ± 4.4 %; P = 0.021) and BDNF (3.1 ± 0.8 % vs 2.7 ± 0.7 %; P = 0.003). The effect of FA treatment on DNA methylation was significant only in female offspring for IGF2 (P = 0.028) and only in males for BDNF (P = 0.012). For GRB10 and GRIN3B, we detected no effect on overall methylation, however, individual CpG sites showed significant DNA methylation changes in response to FA. Conclusions: Continued supplementation with FA through trimesters 2 and 3 of pregnancy results in significant changes in DNA methylation in cord blood of genes related to brain development. The findings offer a potential biological mechanism linking maternal folate status with neurodevelopment of the offspring, but this requires further investigation using a genome-wide approach.