The methylation levels of theH19differentially methylated region in human umbilical cords reflect newborn parameters and changes by maternal environmental factors during early pregnancy
H19 is a tumor-suppressor gene, and changes in the methylation of the H19-differential methylation region (H19-DMR) are related to human health. However, little is known about the factors that regulate the methylation levels of H19-DMR. Several recent studies have shown that maternal environmental factors during pregnancy, such as smoking, drinking, chemical exposure, and nutrient intake, can alter the methylation levels of several genes in fetal tissues. In this study, we examined the effects of maternal factors on changes in the methylation levels of H19-DMR in the human umbilical cord (UC), an extra-embryonic tissue. Participants from the Chiba study of Mother and Children's Health (C-MACH) were enrolled in this study. Genomic DNA was extracted from UC samples, and the methylation level of H19-DMR was evaluated by methylation-sensitive high resolution melting analysis. Individual maternal and paternal factors and clinical information for newborns at birth were examined using questionnaires prepared in the C-MACH study, a brief-type self-administered diet history questionnaire (BDHQ) during early pregnancy (gestational age of 12 weeks), and medical records. Univariate and multivariate logistic regression analyses indicated that reduced H19-DMR methylation (<50% methylation) in UC tissues was positively related to decreased head circumference in newborns [odds ratio (OR) =2.82; 95% confidence intervals (CI): 1.21–6.87; p=0.0183 and OR =2.51; 95% CI: 1.02–6.46; p=0.0499, respectively]. Moreover, multiple comparison test showed that H19-DMR methylation in UC tissues was significantly reduced in the low calorie group (intake of less than 1,000 kcal/day; methylation level: 40.98%; 95% CI: 33.86–48.11) compared with that in the middle (1,000–1,999 kcal/day; methylation level: 51.28%; 95% CI: 48.28–54.27) and high (≥2,000 kcal/day; methylation level: 52.16%; 95% CI: 44.81–59.51) calorie groups (p=0.0054 and 0.047, respectively). In the subpopulations with low to moderate calorie intake (<2,000 kcal/day), reduced H19-DMR methylation in UC tissues was significantly related to serum homocysteine concentration (OR =0.520; 95% CI: 0.285–0.875; p=0.019), maternal age (OR =1.22; 95% CI: 1.01–1.52; p=0.049), and serum folate levels (OR =0.917; 95% CI: 0.838–0.990; p=0.040). These data indicated that H19-DMR methylation levels in human UC tissues could be modulated by maternal factors during early pregnancy and may affect fetal and newborn growth.