Offspring sex impacts DNA methylation and gene expression in placentae from women with diabetes during pregnancy.

Aims/hypothesis: We hypothesized that diabetes during pregnancy (DDP) alters genome-wide DNA methylation in placenta resulting in differentially methylated loci of metabolically relevant genes and downstream changes in RNA and protein expression.

Methods: We mapped genome-wide DNA methylation with the Infinium 450K Human Methylation Bead Chip in term fetal placentae from Native American and Hispanic women with DDP using a nested case-control design (n = 17 pairs). RNA expression and protein levels were assayed via RNA-Seq and Western Blot.

Results: Genome-wide DNA methylation analysis revealed 465 CpG sites with significant changes for male offspring, 247 for female offspring, and 277 for offspring of both sexes (p<0.001). Placentae from female offspring were 40% more likely to have significant gains in DNA methylation compared with placentae from male offspring exposed to DDP (p<0.001). Changes in DNA methylation corresponded to changes in RNA and protein levels for 6 genes: PIWIL3, CYBA, GSTM1, GSTM5, KCNE1 and NXN. Differential DNA methylation was detected at loci related to mitochondrial function, DNA repair, inflammation, oxidative stress.

Conclusions/interpretation: These findings begin to explain mechanisms responsible for the increased risk for obesity and type 2 diabetes in offspring of mothers with DDP.