Being born small for gestational age (SGA), a proxy for intrauterine growth restriction (IUGR), and prenatal famine exposure are both associated with a greater risk of metabolic disease. Both... Show moreBeing born small for gestational age (SGA), a proxy for intrauterine growth restriction (IUGR), and prenatal famine exposure are both associated with a greater risk of metabolic disease. Both associations have been hypothesized to involve epigenetic mechanisms. We investigated whether prenatal growth restriction early in pregnancy was associated with changes in DNA methylation at loci that were previously shown to be sensitive to early gestational famine exposure. We compared 38 individuals born preterm (<32 weeks) and with a birth weight too low for their gestational age (<-1SDS; "SGA") with 75 individuals born preterm but with a birth weight appropriate for their gestational age (>-1SDS) and a normal postnatal growth (>-1SDS at 3 months post term; "AGA"). The SGA individuals were not only lighter at birth, but also had a smaller length (p = 3.3 × 10(-13)) and head circumference at birth (p = 4.1 × 10(-13)). The DNA methylation levels of IGF2, GNASAS, INSIGF and LEP were 48.5%, 47.5%, 79.4% and 25.7% respectively. This was not significantly different between SGA and AGA individuals. Risk factors for being born SGA, including preeclampsia and maternal smoking, were also not associated with DNA methylation at these loci. Growth restriction early in development is not associated with DNA methylation at loci shown to be affected by prenatal famine exposure. Our and previous results by others indicate that prenatal growth restriction and famine exposure may be associated with different epigenetic changes or non-epigenetic mechanisms that may lead to similar later health outcomes. Show less
The prospect of finding epigenetic risk factors for complex diseases would be greatly enhanced if DNA from existing biobanks, which is generally extracted from whole blood, could be used to perform... Show moreThe prospect of finding epigenetic risk factors for complex diseases would be greatly enhanced if DNA from existing biobanks, which is generally extracted from whole blood, could be used to perform epigenetic association studies. We characterized features of DNA methylation at 16 candidate loci, 8 of which were imprinted, in DNA samples from the Netherlands Twin Register biobank. Except for un-methylated or fully methylated sites, CpG methylation varied considerably in a sample of 30 unrelated individuals. This variation remained after accounting for the cellular heterogeneity of blood. Methylation of CpG sites was correlated within loci and, for 4 imprinted loci, across chromosomes. In 34 additional individuals, we investigated the DNA methylation of 8 representative loci in 2 longitudinal blood and 2 longitudinal buccal cell samples (follow-up 11-20 and 2-8 yr, respectively). Five of 8 loci were stable over time (rho > 0.75) in both tissues, indicating that prospective epigenetic studies may be possible. For 4 loci, the DNA methylation in blood (mesoderm) correlated with that in the buccal cells (ectoderm) (rho > 0.75). Our data suggest that epigenetic studies on complex diseases may be feasible for a proportion of genomic loci provided that they are carefully designed.-Talens, R. P., Boomsma, D. I., Tobi, E. W., Kremer, D., Jukema, J. W., Willemsen, G., Putter, H., Slagboom, P. E., Heijmans, B. T. Variation, patterns, and temporal stability of DNA methylation: considerations for epigenetic epidemiology. FASEB J. 24, 3135-3144 (2010). www.fasebj.org Show less
