Placental DNA methylation changes associated with maternal prepregnancy BMI and gestational weight gain.

Abstract

BACKGROUNDMaternal obesity prior to or during pregnancy influences fetal growth, predisposing the offspring to increased risk for obesity across the life-course. Placental epigenetic mechanisms may underlie these associations. We conducted an epigenome-wide association study to identify placental DNA methylation changes associated with maternal pre-pregnancy body mass index (BMI) and rate of gestational weight gain at first (GWG1), second (GWG2) and third trimester (GWG3).METHODParticipants of the NICHD Fetal Growth Studies with genome-wide placental DNA methylation (n=301) and gene expression (n=75) data were included. Multivariable-adjusted regression models were used to test the associations of 1kg/m2 increase in pre-pregnancy BMI or 1kg/week increase in GWG with DNA methylation levels. Genes harboring top differentially methylated CpGs (FDR P<0.05) were evaluated for placental gene expression. We assessed whether DNA methylation sites known to be associated with BMI in child or adult tissues were also associated with maternal pre-pregnancy BMI in placenta.RESULTSPre-pregnancy BMI was associated with DNA methylation at cg14568196[EGFL7], cg15339142[VETZ] and cg02301019[AC092377.1] (FDR P<0.05, P ranging from 1.4×10−10 to 1.7×10−9). GWG1 or GWG2 was associated with DNA methylation at cg17918270[MYT1L], cg20735365[DLX5] and cg17451688[SLC35F3] (FDR P<0.05, P ranging from 6.4×10−10 to 1.2×10−8). Both pre-pregnancy BMI and DNA methylation at cg1456819 [EGFL7] were negatively correlated with EGFL7 expression in placenta (P<0.05). Several CpGs previously implicated in obesity traits in children and adults were associated with pre-pregnancy BMI in placenta. Functional annotations revealed that EGFL7 is highly expressed in placenta and the differentially methylated CpG sites near EGFL7 and VEZT were cis-meQTL targets in blood.CONCLUSIONSWe identified placental DNA methylation changes at novel loci associated with pre-pregnancy BMI and GWG. The overlap between CpGs associated with obesity traits in placenta and other tissues in children and adults suggests that epigenetic mechanisms in placenta may give insights to early origins of obesity.