Cathrine Hoyo

450K epigenome-wide scan identifies differential DNA methylation in newborns related to maternal smoking during pregnancy.

Background: Epigenetic modifications, such as DNA methylation, due to in utero exposures may play a critical role in early programming for childhood and adult illness. Maternal smoking is a major risk factor for multiple adverse health outcomes in children, but the underlying mechanisms are unclear. Objective: We investigated epigenome-wide methylation in cord blood of newborns in relation to maternal smoking during pregnancy. Methods: We examined maternal plasma cotinine (an objective biomarker of smoking) measured during pregnancy in relation to DNA methylation at 473,844 CpG sites (CpGs) in 1,062 newborn cord blood samples from the Norwegian Mother and Child Cohort Study (MoBa) using the Infinium HumanMethylation450 BeadChip (450K). Results: We found differential DNA methylation at epigenome-wide statistical significance (p-value < 1.06 × 10–7) for 26 CpGs mapped to 10 genes. We replicated findings for CpGs in AHRR, CYP1A1, and GFI1 at strict Bonferroni-corrected statistical significance in a U.S. birth cohort. AHRR and CYP1A1 play a key role in the aryl hydrocarbon receptor signaling pathway, which mediates the detoxification of the components of tobacco smoke. GFI1 is involved in diverse developmental processes but has not previously been implicated in responses to tobacco smoke. Conclusions: We identified a set of genes with methylation changes present at birth in children whose mothers smoked during pregnancy. This is the first study of differential methylation across the genome in relation to maternal smoking during pregnancy using the 450K platform. Our findings implicate epigenetic mechanisms in the pathogenesis of the adverse health outcomes associated with this important in utero exposure.

Paternal obesity is associated with IGF2 hypomethylation in newborns: results from a Newborn Epigenetics Study (NEST) cohort.

BackgroundData from epidemiological and animal model studies suggest that nutrition during pregnancy may affect the health status of subsequent generations. These transgenerational effects are now being explained by disruptions at the level of the epigenetic machinery. Besides in vitro environmental exposures, the possible impact on the reprogramming of methylation profiles at imprinted genes at a much earlier time point, such as during spermatogenesis or oogenesis, has not previously been considered. In this study, our aim was to determine associations between preconceptional obesity and DNA methylation profiles in the offspring, particularly at the differentially methylated regions (DMRs) of the imprinted Insulin-like Growth Factor 2 (IGF2) gene.MethodsWe examined DNA from umbilical cord blood leukocytes from 79 newborns, born between July 2005 and November 2006 at Duke University Hospital, Durham, NC. Their mothers participated in the Newborn Epigenetics Study (NEST) during pregnancy. Parental characteristics were obtained via standardized questionnaires and medical records. DNA methylation patterns at two DMRs were analyzed by bisulfite pyrosequencing; one DMR upstream of IGF2 (IGF2 DMR), and one DMR upstream of the neighboring H19 gene (H19 DMR). Multiple regression models were used to determine potential associations between the offsprings DNA methylation patterns and parental obesity before conception. Obesity was defined as body mass index (BMI) ≥30 kg/m2.ResultsHypomethylation at the IGF2 DMR was associated with paternal obesity. Even after adjusting for several maternal and newborn characteristics, we observed a persistent inverse association between DNA methylation in the offspring and paternal obesity (β-coefficient was -5.28, P = 0.003). At the H19 DMR, no significant associations were detected between methylation patterns and paternal obesity. Our data suggest an increase in DNA methylation at the IGF2 and H19 DMRs among newborns from obese mothers, but a larger study is warranted to further explore the potential effects of maternal obesity or lifestyle on the offsprings epigenome.ConclusionsWhile our small sample size is limited, our data indicate a preconceptional impact of paternal obesity on the reprogramming of imprint marks during spermatogenesis. Given the biological importance of imprinting fidelity, our study provides evidence for transgenerational effects of paternal obesity that may influence the offsprings future health status.

Methylation variation at IGF2 differentially methylated regions and maternal folic acid use before and during pregnancy

Folic acid (FA) supplementation before and during pregnancy has been associated with decreased risk of neural tube defects although recent reports suggest it may also increase the risk of other chronic diseases. We evaluated exposure to maternal FA supplementation before and during pregnancy in relation to aberrant DNA methylation at two differentially methylated regions (DMRs) regulating Insulin-like Growth Factor 2 (IGF2) expression in infants. Aberrant methylation at these regions has been associated with IGF2 deregulation and increased susceptibility to several chronic diseases. Using a self-administered questionnaire, we assessed FA intake before and during pregnancy in 438 pregnant women. Pyrosequencing was used to measure methylation at two IGF2 DMRs in umbilical cord blood leukocytes. Mixed models were used to determine relationships between maternal FA supplementation before or during pregnancy and DNA methylation levels at birth. Average methylation at the H19 DMR was 61.2%. Compared to infants born to women reporting no FA intake before or during pregnancy, methylation levels at the H19 DMR decreased with increasing FA intake (2.8%, p=0.03, and 4.9%, p=0.04, for intake before and during pregnancy, respectively). This methylation decrease was most pronounced in male infants (p=0.01). Methylation alterations at the H19 DMR are likely an important mechanism by which FA risks and/or benefits are conferred in utero. Because stable methylation marks at DMRs regulating imprinted genes are acquired before gastrulation, they may serve as archives of early exposures with the potential to improve our understanding of developmental origins of adult disease.

Gender-specific methylation differences in relation to prenatal exposure to cigarette smoke

Epigenetic alterations may mechanistically explain the developmental origins of adult disease, namely the hypothesis that many complex adult chronic diseases originate as a result of conditions encountered in utero. If true, epigenetically regulated imprinted genes, critical to normal growth and development, may partially mediate these outcomes. We determined the influence of in utero exposure to cigarette smoking on methylation at two differentially methylated regions (DMRs) regulating Insulin-like Growth Factor 2 (IGF2) and H19, and how this might relate to birth weight of infants born to 418 pregnant women. Smoking status was ascertained through self-report and medical records. Bisulfite pyrosequencing was used to measure methylation in umbilical cord blood DNAs. Least squares DNA methylation means at each DMR and birth weight were compared between infants of smokers and non-smokers, using generalized linear models. While there were no significant differences at the H19 DMR, infants born to smokers had higher methylation at the IGF2 DMR than those born to never smokers or those who quit during pregnancy (49.5%, SD=8.0 versus 46.6%, SD=5.6 and 45.8%, SD=6.3, respectively; p=0.0002). The smoking-related increase in methylation was most pronounced in male offspring (p for sex interaction=0.03), for whom approximately 20% of smoking-related low birth weight was mediated by DNA methylation at the IGF2 DMR. Our findings suggest that IGF2 DMR plasticity is an important mechanism by which in utero adjustments to environmental toxicants are conferred. Larger studies to replicate these findings are required.

Newborns of obese parents have altered DNA methylation patterns at imprinted genes.

Background:Several epidemiologic studies have demonstrated associations between periconceptional environmental exposures and health status of the offspring in later life. Although these environmentally related effects have been attributed to epigenetic changes, such as DNA methylation shifts at imprinted genes, little is known about the potential effects of maternal and paternal preconceptional overnutrition or obesity.Objective:We examined parental preconceptional obesity in relation to DNA methylation profiles at multiple human imprinted genes important in normal growth and development, such as: maternally expressed gene 3 (MEG3), mesoderm-specific transcript (MEST), paternally expressed gene 3 (PEG3), pleiomorphic adenoma gene-like 1 (PLAGL1), epsilon sarcoglycan and paternally expressed gene 10 (SGCE/PEG10) and neuronatin (NNAT).Methods:We measured methylation percentages at the differentially methylated regions (DMRs) by bisulfite pyrosequencing in DNA extracted from umbilical cord blood leukocytes of 92 newborns. Preconceptional obesity, defined as BMI ⩾30 kg m−2, was ascertained through standardized questionnaires.Results:After adjusting for potential confounders and cluster effects, paternal obesity was significantly associated with lower methylation levels at the MEST (β=−2.57; s.e.=0.95; P=0.008), PEG3 (β=−1.71; s.e.=0.61; P=0.005) and NNAT (β=−3.59; s.e.=1.76; P=0.04) DMRs. Changes related to maternal obesity detected at other loci were as follows: β-coefficient was +2.58 (s.e.=1.00; P=0.01) at the PLAGL1 DMR and −3.42 (s.e.=1.69; P=0.04) at the MEG3 DMR.Conclusion:We found altered methylation outcomes at multiple imprint regulatory regions in children born to obese parents, compared with children born to non-obese parents. In spite of the small sample size, our data suggest a preconceptional influence of parental life-style or overnutrition on the (re)programming of imprint marks during gametogenesis and early development. More specifically, the significant and independent association between paternal obesity and the offspring’s methylation status suggests the susceptibility of the developing sperm for environmental insults. The acquired imprint instability may be carried onto the next generation and increase the risk for chronic diseases in adulthood.

A paternal environmental legacy: Evidence for epigenetic inheritance through the male germ line

Literature on maternal exposures and the risk of epigenetic changes or diseases in the offspring is growing. Paternal contributions are often not considered. However, some animal and epidemiologic studies on various contaminants, nutrition, and lifestyle‐related conditions suggest a paternal influence on the offsprings future health. The phenotypic outcomes may have been attributed to DNA damage or mutations, but increasing evidence shows that the inheritance of environmentally induced functional changes of the genome, and related disorders, are (also) driven by epigenetic components. In this essay we suggest the existence of epigenetic windows of susceptibility to environmental insults during sperm development. Changes in DNA methylation, histone modification, and non‐coding RNAs are viable mechanistic candidates for a non‐genetic transfer of paternal environmental information, from maturing germ cell to zygote. Inclusion of paternal factors in future research will ultimately improve the understanding of transgenerational epigenetic plasticity and health‐related effects in future generations.

Body mass index in relation to oesophageal and oesophagogastric junction adenocarcinomas: a pooled analysis from the International BEACON Consortium

Background Previous studies suggest an association between obesity and oesophageal (OA) and oesophagogastric junction adenocarcinomas (OGJA). However, these studies have been limited in their ability to assess whether the effects of obesity vary by gender or by the presence of gastro-oesophageal reflux (GERD) symptoms. Methods Individual participant data from 12 epidemiological studies (8 North American, 3 European and 1 Australian) comprising 1997 OA cases, 1900 OGJA cases and 11 159 control subjects were pooled. Logistic regression was used to estimate study-specific odds ratios (ORs) and 95% confidence intervals (CIs) for the association between body mass index (BMI, kg/m2) and the risk of OA and OGJA. Random-effects meta-analysis was used to combine these ORs. We also investigated effect modification and synergistic interaction of BMI with GERD symptoms and gender. Results The association of OA and OGJA increased directly with increasing BMI (P for trend <0.001). Compared with individuals with a BMI <25, BMI ≥40 was associated with both OA (OR 4.76, 95% CI 2.96–7.66) and OGJA (OR 3.07, 95% CI 1.89–4.99). These associations were similar when stratified by gender and GERD symptoms. There was evidence for synergistic interaction between BMI and GERD symptoms in relation to OA/OGJA risk. Conclusions These data indicate that BMI is directly associated with OA and OGJA risk in both men and women and in those with and without GERD symptoms. Disentangling the relationship between BMI and GERD will be important for understanding preventive efforts for OA and OGJA.

Depression in pregnancy, infant birth weight and DNA methylation of imprint regulatory elements

Depressed mood in pregnancy has been linked to low birth weight (LBW, < 2,500 g), a risk factor for adult-onset chronic diseases in offspring. We examined maternal depressed mood in relation to birth weight and evaluated the role of DNA methylation at regulatory sequences of imprinted genes in this association. We measured depressed mood among 922 pregnant women using the CES-D scale and obtained birth weight data from hospital records. Using bisulfite pyrosequencing of cord blood DNA from 508 infants, we measured methylation at differentially methylated regions (DMRs) regulating imprinted genes IGF2/H19, DLK1/MEG3, MEST, PEG3, PEG10/SGCE, NNAT and PLAGL1. Multiple regression models were used to examine the relationship between depressed mood, birth weight and DMR methylation levels. Depressed mood was associated with a more that 3-fold higher risk of LBW, after adjusting for delivery mode, parity, education, cigarette smoking, folic acid use and preterm birth. The association may be more pronounced in offspring of black women and female infants. Compared with infants of women without depressed mood, infants born to women with severe depressed mood had a 2.4% higher methylation at the MEG3 DMR. Whereas LBW infants had 1.6% lower methylation at the IGF2 DMR, high birth weight (> 4,500 g) infants had 5.9% higher methylation at the PLAGL1 DMR compared with normal birth weight infants. Our findings confirm that severe maternal depressed mood in pregnancy is associated with LBW, and that MEG3 and IGF2 plasticity may play important roles.

Obesity and risk of ovarian cancer subtypes: evidence from the Ovarian Cancer Association Consortium

Whilst previous studies have reported that higher BMI increases a womans risk of developing ovarian cancer, associations for the different histological subtypes have not been well defined. As the prevalence of obesity has increased dramatically, and classification of ovarian histology has improved in the last decade, we sought to examine the association in a pooled analysis of recent studies participating in the Ovarian Cancer Association Consortium. We evaluated the association between BMI (recent, maximum and in young adulthood) and ovarian cancer risk using original data from 15 case-control studies (13 548 cases and 17 913 controls). We combined study-specific adjusted odds ratios (ORs) using a random-effects model. We further examined the associations by histological subtype, menopausal status and post-menopausal hormone use. High BMI (all time-points) was associated with increased risk. This was most pronounced for borderline serous (recent BMI: pooled OR=1.24 per 5 kg/m(2); 95% CI 1.18-1.30), invasive endometrioid (1.17; 1.11-1.23) and invasive mucinous (1.19; 1.06-1.32) tumours. There was no association with serous invasive cancer overall (0.98; 0.94-1.02), but increased risks for low-grade serous invasive tumours (1.13, 1.03-1.25) and in pre-menopausal women (1.11; 1.04-1.18). Among post-menopausal women, the associations did not differ between hormone replacement therapy users and non-users. Whilst obesity appears to increase risk of the less common histological subtypes of ovarian cancer, it does not increase risk of high-grade invasive serous cancers, and reducing BMI is therefore unlikely to prevent the majority of ovarian cancer deaths. Other modifiable factors must be identified to control this disease.

Insulin-Like Growth Factor 2/H19 Methylation at Birth and Risk of Overweight and Obesity in Children

OBJECTIVE To determine whether aberrant DNA methylation at differentially methylated regions (DMRs) regulating insulin-like growth factor 2 (IGF2) expression in umbilical cord blood is associated with overweight or obesity in a multiethnic cohort. STUDY DESIGN Umbilical cord blood leukocytes of 204 infants born between 2005 and 2009 in Durham, North Carolina, were analyzed for DNA methylation at two IGF2 DMRs by using pyrosequencing. Anthropometric and feeding data were collected at age 1 year. Methylation differences were compared between children >85th percentile of the Centers for Disease Control and Prevention growth charts weight-for-age (WFA) and children ≤ 85th percentile of WFA at 1 year by using generalized linear models, adjusting for post-natal caloric intake, maternal cigarette smoking, and race/ethnicity. RESULTS The methylation percentages at the H19 imprint center DMR was higher in infants with WFA >85th percentile (62.7%; 95% CI, 59.9%-65.5%) than in infants with WFA ≤ 85th percentile (59.3%; 95% CI, 58.2%-60.3%; P = .02). At the intragenic IGF2 DMR, methylation levels were comparable between infants with WFA ≤ 85th percentile and infants with WFA >85th percentile. CONCLUSIONS Our findings suggest that IGF2 plasticity may be mechanistically important in early childhood overweight or obese status. If confirmed in larger studies, these findings suggest aberrant DNA methylation at sequences regulating imprinted genes may be useful identifiers of children at risk for the development of early obesity.