Epigenome-Wide Association Study Reveals Methylation Loci Associated With Offspring Gestational Diabetes Mellitus Exposure and Maternal Methylome

Abstract

Objective: Gestational diabetes mellitus (GDM) is associated with an increased risk of obesity and insulin resistance in offspring later in life, which might be explained by epigenetic changes in response to maternal hyperglycemic exposure.

Research design and methods: We explored the association between GDM exposure and maternal blood and newborn cord blood methylation in 536 mother-offspring pairs from the prospective FinnGeDi cohort using Illumina MethylationEPIC 850K BeadChip arrays. We assessed two hypotheses. First, we tested for shared maternal and offspring epigenetic effects resulting from GDM exposure. Second, we tested whether GDM exposure and maternal methylation had an epigenetic effect on the offspring.

Results: We did not find any epigenetic marks (differentially methylated CpG probes) with shared and consistent effects between mothers and offspring. After including maternal methylation in the model, we identified a single significant (false discovery rate 1.38 × 10^-2) CpG at the cg22790973 probe (TFCP2) associated with GDM. We identified seven additional FDR-significant interactions of maternal methylation and GDM status, with the strongest association at the same cg22790973 probe (TFCP2), as well as cg03456133, cg24440941 (H3C6), cg20002843 (LOC127841), cg19107264, and cg11493553 located within the UBE3C gene and cg17065901 in FAM13A, both susceptibility genes for type 2 diabetes and BMI, and cg23355087 within the DLGAP2 gene, known to be involved in insulin resistance during pregnancy.

Conclusions: Our study reveals the potential complexity of the epigenetic transmission between mothers with GDM and their offspring, likely determined by not only GDM exposure but also other factors indicated by maternal epigenetic status, such as maternal metabolic history.

Figure 1

The investigated study hypotheses. A: Hypothesis 1: assess whether there are epigenetic effects that are shared by both offspring and their mothers as a result of shared exposure to GDM (offspring and maternal methylation regressed upon GDM status; see Research Design and Methods). B: Hypothesis 2: test if there are epigenetic effects as a result of exposure to GDM that are specific to the offspring (offspring DNA methylation regressed upon GDM status, maternal methylation for the same probe, and interaction between GDM and maternal methylation status; see Research Design and Methods).

Figure 2

Summary results for offspring EWAS associations. Linear model between offspring methylation and exposure to maternal GDM, including the methylation of mothers in the model, and interaction between GDM exposure and maternal methylation, adjusted for offspring sex, gestational week, birth weight, and cell composition. A: Volcano plot for offspring probe differential methylation by GDM exposure; cg22790973 has an estimate of −1.56 (FDR 1.38 × 10⁻²), equivalent to a β-value of 1.03%. B: Manhattan plot for the GDM exposure main effect, showing the genome-wide results for all the CpGs. C: Volcano plot of the GDM exposure interaction effect. D: Manhattan plot of the GDM exposure interaction effect, showing the genome-wide results for all the CpGs. E: Probability-probability plot of the GDM exposure main effect (green) and interaction term (red) on methylation of offspring, with the black line indicating the expected distribution.

Figure 3

Differential methylation observed for offspring at probe cg22790973 (TFCP2). A: Box plot showing the methylation differences between offspring exposed to maternal GDM compared with nonexposed controls. B: Scatterplot showing increased methylation at this probe for offspring exposed to maternal GDM along with increased maternal methylation at the same probe. For nonexposed offspring, methylation decreased with increased maternal methylation at this probe.