Integrating multiple lines of evidence to assess the effects of maternal BMI on pregnancy and perinatal outcomes.

BACKGROUND: Higher maternal pre-pregnancy body mass index (BMI) is associated with adverse pregnancy and perinatal outcomes. However, whether these associations are causal remains unclear. METHODS: We explored the relation of maternal pre-/early-pregnancy BMI with 20 pregnancy and perinatal outcomes by integrating evidence from three different approaches (i.e. multivariable regression, Mendelian randomisation, and paternal negative control analyses), including data from over 400,000 women. RESULTS: All three analytical approaches supported associations of higher maternal BMI with lower odds of maternal anaemia, delivering a small-for-gestational-age baby and initiating breastfeeding, but higher odds of hypertensive disorders of pregnancy, gestational hypertension, preeclampsia, gestational diabetes, pre-labour membrane rupture, induction of labour, caesarean section, large-for-gestational age, high birthweight, low Apgar score at 1 min, and neonatal intensive care unit admission. For example, higher maternal BMI was associated with higher risk of gestational hypertension in multivariable regression (OR = 1.67; 95% CI = 1.63, 1.70 per standard unit in BMI) and Mendelian randomisation (OR = 1.59; 95% CI = 1.38, 1.83), which was not seen for paternal BMI (OR = 1.01; 95% CI = 0.98, 1.04). Findings did not support a relation between maternal BMI and perinatal depression. For other outcomes, evidence was inconclusive due to inconsistencies across the applied approaches or substantial imprecision in effect estimates from Mendelian randomisation. CONCLUSIONS: Our findings support a causal role for maternal pre-/early-pregnancy BMI on 14 out of 20 adverse pregnancy and perinatal outcomes. Pre-conception interventions to support women maintaining a healthy BMI may reduce the burden of obstetric and neonatal complications. FUNDING: Medical Research Council, British Heart Foundation, European Research Council, National Institutes of Health, National Institute for Health Research, Research Council of Norway, Wellcome Trust.

Analysis of DNA methylation at birth and in childhood reveals changes associated with season of birth and latitude.

BACKGROUND: Seasonal variations in environmental exposures at birth or during gestation are associated with numerous adult traits and health outcomes later in life. Whether DNA methylation (DNAm) plays a role in the molecular mechanisms underlying the associations between birth season and lifelong phenotypes remains unclear. METHODS: We carried out epigenome-wide meta-analyses within the Pregnancy And Childhood Epigenetic Consortium to identify associations of DNAm with birth season, both at differentially methylated probes (DMPs) and regions (DMRs). Associations were examined at two time points: at birth (21 cohorts, N = 9358) and in children aged 1-11 years (12 cohorts, N = 3610). We conducted meta-analyses to assess the impact of latitude on birth season-specific associations at both time points. RESULTS: We identified associations between birth season and DNAm (False Discovery Rate-adjusted p values < 0.05) at two CpGs at birth (winter-born) and four in the childhood (summer-born) analyses when compared to children born in autumn. Furthermore, we identified twenty-six differentially methylated regions (DMR) at birth (winter-born: 8, spring-born: 15, summer-born: 3) and thirty-two in childhood (winter-born: 12, spring and summer: 10 each) meta-analyses with few overlapping DMRs between the birth seasons or the two time points. The DMRs were associated with genes of known functions in tumorigenesis, psychiatric/neurological disorders, inflammation, or immunity, amongst others. Latitude-stratified meta-analyses [higher (≥ 50°N), lower (< 50°N, northern hemisphere only)] revealed differences in associations between birth season and DNAm by birth latitude. DMR analysis implicated genes with previously reported links to schizophrenia (LAX1), skin disorders (PSORS1C, LTB4R), and airway inflammation including asthma (LTB4R), present only at birth in the higher latitudes (≥ 50°N). CONCLUSIONS: In this large epigenome-wide meta-analysis study, we provide evidence for (i) associations between DNAm and season of birth that are unique for the seasons of the year (temporal effect) and (ii) latitude-dependent variations in the seasonal associations (spatial effect). DNAm could play a role in the molecular mechanisms underlying the effect of birth season on adult health outcomes.

Maternal Hyperglycemia in Pregnancy and Offspring Internalizing and Externalizing Behaviors.

OBJECTIVE: To examine the associations between exposure to gestational diabetes mellitus (GDM) and maternal glycemic markers during pregnancy and offspring behaviors at 3 and 5 years. We hypothesized that exposure to maternal hyperglycemia would be associated with more behavioral problems in offspring. METHODS: We included 548 mother-child pairs from the prospective pre-birth Gen3G cohort (Canada). Glycemic markers were measured during a 75 g oral glucose tolerance test (OGTT) in the second trimester of pregnancy. Based on OGTT, we classified 59 women (10.8%) as having GDM according to international diagnostic criteria. Mothers reported offspring behavior using the Strengths and Difficulties Questionnaire (SDQ) at 3 and 5 years, and the Child Behavior Checklist (CBCL) at 5 years. We used linear mixed models and multivariate regression to assess the associations between GDM or glycemic markers and children's behavior, adjusted for child sex and age, and maternal demographic factors, body mass index and family history of diabetes. RESULTS: Exposure to GDM was associated with higher SDQ externalizing scores at 3 and 5 years [B = 1.12, 95% CI (0.14, 2.10)] in fully adjusted linear mixed models. These results were supported by the CBCL at 5 years. Higher levels of maternal glucose at 1 h and 2 h during OGTT were associated with greater SDQ externalizing scores. Fasting glucose levels were not associated with child behavior scores. We did not observe associations between glycemic markers and internalizing behaviors. CONCLUSIONS: Exposure to higher levels of maternal glycemia during pregnancy was associated with more externalizing behaviors in children at 3 and 5 years.

What is already known on this subject? Prenatal exposure to gestational diabetes mellitus (GDM) has been linked to a higher risk of long-term consequences in offspring including metabolic problems and cognitive difficulties. However, prior studies examining associations between GDM and behavior in children reported mixed results. What this study adds? We reported associations between exposure to maternal GDM and post-OGTT hyperglycemia during pregnancy and greater levels of externalizing behaviors in children at 3 and 5 years of age. Our results underscore the importance of early detection of behavioral problems in children.

Maternal glycemia in pregnancy is longitudinally associated with blood DNAm variation at the FSD1L gene from birth to 5 years of age.

BACKGROUND: In utero exposure to maternal hyperglycemia has been associated with an increased risk for the development of chronic diseases in later life. These predispositions may be programmed by fetal DNA methylation (DNAm) changes that persist postnatally. However, although some studies have associated fetal exposure to gestational hyperglycemia with DNAm variations at birth, and metabolic phenotypes in childhood, no study has yet examined how maternal hyperglycemia during pregnancy may be associated with offspring DNAm from birth to five years of age. HYPOTHESIS: Maternal hyperglycemia is associated with variation in offspring DNAm from birth to 5 years of age. METHODS: We estimated maternal hyperglycemia using the area under the curve for glucose (AUCglu) following an oral glucose tolerance test conducted at 24-30 weeks of pregnancy. We quantified DNAm levels in cord blood (n = 440) and peripheral blood at five years of age (n = 293) using the Infinium MethylationEPIC BeadChip (Illumina). Our total sample included 539 unique dyads (mother-child) with 194 dyads having DNAm at both time-points. We first regressed DNAm M-values against the cell types and child age for each time-point separately to account for the difference by time of measurement for these variables. We then used a random intercept model from the linear mixed model (LMM) framework to assess the longitudinal association between maternal AUCglu and the repeated measures of residuals of DNAm. We adjusted for the following covariates as fixed effects in the random intercept model: maternal age, gravidity, smoking status, child sex, maternal body mass index (BMI) (measured at first trimester of pregnancy), and a binary variable for time-point. RESULTS: In utero exposure to higher maternal AUCglu was associated with lower offspring blood DNAm levels at cg00967989 located in FSD1L gene (ß = - 0.0267, P = 2.13 × 10-8) in adjusted linear regression mixed models. Our study also reports other CpG sites for which DNAm levels were suggestively associated (P < 1.0 × 10-5) with in utero exposure to gestational hyperglycemia. Two of these (cg12140144 and cg07946633) were found in the promotor region of PRDM16 gene (ß: - 0.0251, P = 4.37 × 10-07 and ß: - 0.0206, P = 2.24 × 10-06, respectively). CONCLUSION: Maternal hyperglycemia is associated with offspring DNAm longitudinally assessed from birth to 5 years of age.

Pre-pregnancy body mass index and gut microbiota of mothers and children 5 years postpartum.

BACKGROUND: Maternal pre-pregnancy body mass index (BMI) has been linked to altered gut microbiota in women shortly after delivery and in their offspring in the first few years of life. But little is known about how long these differences persist. METHODS: We followed 180 mothers and children from pregnancy until 5-year postpartum in the Gen3G cohort (Canada, enrolled 2010-2013). At 5 years postpartum we collected stool samples from mothers and children and estimated the gut microbiota by 16 S rRNA sequencing (V4 region) using Illumina MiSeq, and assigning amplicon sequence variants (ASV). We examined whether overall microbiota composition (as measured by microbiota ß diversity) was more similar between mother-child pairs compared to between mothers or between children. We also assessed whether mother-child pair sharing of overall microbiota composition differed by the weight status of mothers before pregnancy and of children at 5-year. Furthermore, in mothers, we examined whether pre-pregnancy BMI, BMI 5-year postpartum, and change in BMI between time points was associated with maternal gut microbiota 5-year postpartum. In children, we further examined associations of maternal pre-pregnancy BMI and child 5-year BMI z-score with child 5-year gut microbiota. RESULTS: Mother-child pairs had greater similarity in overall microbiome composition compared to between mothers and between children. In mothers, higher pre-pregnancy BMI and 5-year postpartum BMI were associated with lower microbiota observed ASV richness and Chao 1 index; in children's gut microbiota, higher maternal pre-pregnancy BMI was weakly associated with lower microbiota Shannon index, whereas child's 5-year BMI z-score was associated with higher observed ASV richness. Pre-pregnancy BMI was also linked to differential abundances of several microbial ASVs in the Ruminococcaceae and Lachnospiraceae families, but no specific ASV had overlapping associations with BMI measures in both mothers and children. CONCLUSIONS: Pre-pregnancy BMI was associated with gut microbiota diversity and composition of mothers and children 5 years after birth, however, the nature and direction of most associations differed for mothers and children. Future studies are encouraged to confirm our findings and look into potential mechanisms or factors that may drive these associations.

Associations of maternal insulin sensitivity during pregnancy with childhood central adiposity in the Genetics of Glucose regulation in Gestation and Growth (Gen3G) cohort.

BACKGROUND: Childhood obesity has been associated with prenatal exposure to maternal hyperglycaemia, but we lack understanding about maternal insulin physiologic components that contribute to this association. OBJECTIVES: Evaluate the association between maternal insulin sensitivity during pregnancy and adiposity measures in childhood. METHODS: In 422 mother-child pairs, we tested associations between maternal insulin sensitivity measures at ~26 weeks of pregnancy and child adiposity measures, including dual-energy X-ray absorptiometry body composition and anthropometry (body mass index and waist circumference) at ~5 years. We used linear regression analyses to adjust for maternal age, ethnicity, gravidity, first-trimester body mass index, and child sex and age at mid-childhood. RESULTS: In early pregnancy, maternal mean age was 28.6 ± 4.3 years and median body mass index was 24.1 kg/m2 . Lower maternal insulin sensitivity indices were correlated with greater child adiposity based on anthropometry measures and on dual-energy X-ray absorptiometry total and trunk % fat in univariate associations (r = -0.122 to -0.159). Lower maternal insulin sensitivity was specifically associated with higher dual-energy X-ray absorptiometry trunk % fat (n = 359 for Matsuda; ß = -0.034 ± 0.013; p = 0.01) after adjustment for covariates, including maternal body mass index. CONCLUSIONS: Maternal insulin sensitivity during pregnancy may contribute to increased risk for higher offspring central adiposity in middle childhood.

Associations of maternal glucose markers in pregnancy with cord blood glucocorticoids and child hair cortisol levels.

Exposure to maternal hyperglycemia in utero has been associated with adverse metabolic outcomes in offspring. However, few studies have investigated the relationship between maternal hyperglycemia and offspring cortisol levels. We assessed associations of gestational diabetes mellitus (GDM) with cortisol biomarkers in two longitudinal prebirth cohorts: Project Viva included 928 mother-child pairs and Gen3G included 313 mother-child pairs. In Project Viva, GDM was diagnosed in N = 48 (5.2%) women using a two-step procedure (50 g glucose challenge test, if abnormal followed by 100 g oral glucose tolerance test [OGTT]), and in N = 29 (9.3%) women participating in Gen3G using one-step 75 g OGTT. In Project Viva, we measured cord blood glucocorticoids and child hair cortisol levels during mid-childhood (mean (SD) age: 7.8 (0.8) years) and early adolescence (mean (SD) age: 13.2 (0.9) years). In Gen3G, we measured hair cortisol at 5.4 (0.3) years. We used multivariable linear regression to examine associations of GDM with offspring cortisol, adjusting for child age and sex, maternal prepregnancy body mass index, education, and socioeconomic status. We additionally adjusted for child race/ethnicity in the cord blood analyses. In both Project Viva and Gen3G, we observed null associations of GDM and maternal glucose markers in pregnancy with cortisol biomarkers in cord blood at birth (ß = 16.6 nmol/L, 95% CI -60.7, 94.0 in Project Viva) and in hair samples during childhood (ß = -0.56 pg/mg, 95% CI -1.16, 0.04 in Project Viva; ß = 0.09 pg/mg, 95% CI -0.38, 0.57 in Gen3G). Our findings do not support the hypothesis that maternal hyperglycemia is related to hypothalamic-pituitary-adrenal axis activity.

Associations between Cord Blood Leptin Levels and Childhood Adiposity Differ by Sex and Age at Adiposity Assessment.

Lower cord blood leptin levels have been associated with lower and higher adiposity in childhood and associations seem to differ according to the child's age, methods of adiposity assessment and sex. Our aim was to investigate sex-specific associations of cord blood leptinemia with childhood adiposity at birth, 3 and 5 years of age. We measured cord blood leptin using Luminex immunoassays in 520 offspring from the Gen3G cohort. We tested associations between cord blood leptin and body mass index (BMI) z-score, skinfolds thicknesses (SFT), and body composition using dual-energy X-ray absorptiometry, adjusted for confounders. At birth, girls had almost twice as much leptin in cord blood as boys (15.5 [8.9; 25.6] vs. 8.6 [4.9; 15.0] ng/mL; p < 0.0001) as well as significantly greater adiposity. Lower levels of cord blood leptin were associated with higher sum of SFT (ß = −0.05 ± 0.02; p = 0.03) and higher BMI z-score (ß= −0.22 ± 0.08; p = 0.01) in 3-year-old boys only. We did not observe these associations at age 5, or in girls. Our results suggest a sexual dimorphism in the programming of leptin sensitivity and childhood adiposity, but further observational and functional studies are needed to better understand the role of leptin in early life.

First Trimester Plasma MicroRNA Levels Predict Risk of Developing Gestational Diabetes Mellitus.

Aims: Our objective is to identify first-trimester plasmatic miRNAs associated with and predictive of GDM. Methods: We quantified miRNA using next-generation sequencing in discovery (Gen3G: n = 443/GDM = 56) and replication (3D: n = 139/GDM = 76) cohorts. We have diagnosed GDM using a 75-g oral glucose tolerance test and the IADPSG criteria. We applied stepwise logistic regression analysis among replicated miRNAs to build prediction models. Results: We identified 17 miRNAs associated with GDM development in both cohorts. The prediction performance of hsa-miR-517a-3p|hsa-miR-517b-3p, hsa-miR-218-5p, and hsa-let7a-3p was slightly better than GDM classic risk factors (age, BMI, familial history of type 2 diabetes, history of GDM or macrosomia, and HbA1c) (AUC 0.78 vs. 0.75). MiRNAs and GDM classic risk factors together further improved the prediction values [AUC 0.84 (95% CI 0.73-0.94)]. These results were replicated in 3D, although weaker predictive values were obtained. We suggest very low and higher risk GDM thresholds, which could be used to identify women who could do without a diagnostic test for GDM and women most likely to benefit from an early GDM prevention program. Conclusions: In summary, three miRNAs combined with classic GDM risk factors provide excellent prediction values, potentially strong enough to improve early detection and prevention of GDM.

A meta-analysis of pre-pregnancy maternal body mass index and placental DNA methylation identifies 27 CpG sites with implications for mother-child health.

Higher maternal pre-pregnancy body mass index (ppBMI) is associated with increased neonatal morbidity, as well as with pregnancy complications and metabolic outcomes in offspring later in life. The placenta is a key organ in fetal development and has been proposed to act as a mediator between the mother and different health outcomes in children. The overall aim of the present work is to investigate the association of ppBMI with epigenome-wide placental DNA methylation (DNAm) in 10 studies from the PACE consortium, amounting to 2631 mother-child pairs. We identify 27 CpG sites at which we observe placental DNAm variations of up to 2.0% per 10 ppBMI-unit. The CpGs that are differentially methylated in placenta do not overlap with CpGs identified in previous studies in cord blood DNAm related to ppBMI. Many of the identified CpGs are located in open sea regions, are often close to obesity-related genes such as GPX1 and LGR4 and altogether, are enriched in cancer and oxidative stress pathways. Our findings suggest that placental DNAm could be one of the mechanisms by which maternal obesity is associated with metabolic health outcomes in newborns and children, although further studies will be needed in order to corroborate these findings.

SERPINE1 DNA Methylation Levels Quantified in Blood Cells at Five Years of Age Are Associated with Adiposity and Plasma PAI-1 Levels at Five Years of Age.

Plasminogen activator inhibitor (PAI-1) expression has been associated with a higher risk of development of obesity. DNA methylation (DNAm) is an epigenetic mechanism regulating gene transcription and likely involved in the fetal programming of childhood obesity. Our study aimed to assess the associations between PAI-1 gene (SERPINE1) DNAm, plasma PAI-1 levels, and adiposity at five years of age. We analyzed DNAm and anthropometric data from 146 girls and 177 boys from the Gen3G prospective birth cohort. We assessed adiposity using BMI z-scores, waist circumference, total skinfolds, and percentages of total, android, and trunk fat measured by dual-energy radiography (DXA). We estimated blood cell DNAm levels at 15 CpG sites within SERPINE1 using the methylationEPIC array. After correction for multiple testing, we found that lower DNAm in SERPINE1 intron 3 (cg11353706) was associated with greater adiposity levels in girls (waist circumference: r = −0.258, p = 0.002; skinfolds: r = −0.212, p = 0. 013; android fat: r = −0.215, p = 0.015; BMI z-score: r = −0.278, p < 0.001) and that lower DNAm in the SERPINE1 promoter (cg19722814) was associated with higher plasma PAI-1 levels in boys (r = −0.178, p = 0.021). Our study suggests that DNAm levels at the SERPINE1 gene locus are negatively correlated with adiposity, but not with plasma PAI-1 levels, in young girls only.

Maternal Body Mass Index Is Associated with Profile Variation in Circulating MicroRNAs at First Trimester of Pregnancy.

Many women enter pregnancy with overweight and obesity, which are associated with complications for both the expectant mother and her child. MicroRNAs (miRNAs) are short non-coding RNAs that regulate many biological processes, including energy metabolism. Our study aimed to identify first trimester plasmatic miRNAs associated with maternal body mass index (BMI) in early pregnancy. We sequenced a total of 658 plasma samples collected between the 4th and 16th week of pregnancy from two independent prospective birth cohorts (Gen3G and 3D). In each cohort, we assessed associations between early pregnancy maternal BMI and plasmatic miRNAs using DESeq2 R package, adjusting for sequencing run and lane, gestational age, maternal age at the first trimester of pregnancy and parity. A total of 38 miRNAs were associated (FDR q < 0.05) with BMI in the Gen3G cohort and were replicated (direction and magnitude of the fold change) in the 3D cohort, including 22 with a nominal p-value < 0.05. Some of these miRNAs were enriched in fatty acid metabolism-related pathways. We identified first trimester plasmatic miRNAs associated with maternal BMI. These miRNAs potentially regulate fatty acid metabolism-related pathways, supporting the hypothesis of their potential contribution to energy metabolism regulation in early pregnancy.

Meta-analysis of epigenome-wide association studies in newborns and children show widespread sex differences in blood DNA methylation.

BACKGROUND: Among children, sex-specific differences in disease prevalence, age of onset, and susceptibility have been observed in health conditions including asthma, immune response, metabolic health, some pediatric and adult cancers, and psychiatric disorders. Epigenetic modifications such as DNA methylation may play a role in the sexual differences observed in diseases and other physiological traits. METHODS: We performed a meta-analysis of the association of sex and cord blood DNA methylation at over 450,000 CpG sites in 8438 newborns from 17 cohorts participating in the Pregnancy And Childhood Epigenetics (PACE) Consortium. We also examined associations of child sex with DNA methylation in older children ages 5.5-10 years from 8 cohorts (n = 4268). RESULTS: In newborn blood, sex was associated at Bonferroni level significance with differences in DNA methylation at 46,979 autosomal CpG sites (p < 1.3 × 10-7) after adjusting for white blood cell proportions and batch. Most of those sites had lower methylation levels in males than in females. Of the differentially methylated CpG sites identified in newborn blood, 68% (31,727) met look-up level significance (p < 1.1 × 10-6) in older children and had methylation differences in the same direction. CONCLUSIONS: This is a large-scale meta-analysis examining sex differences in DNA methylation in newborns and older children. Expanding upon previous studies, we replicated previous findings and identified additional autosomal sites with sex-specific differences in DNA methylation. Differentially methylated sites were enriched in genes involved in cancer, psychiatric disorders, and cardiovascular phenotypes.

First trimester plasma microRNAs levels predict Matsuda Index-estimated insulin sensitivity between 24th and 29th week of pregnancy.

INTRODUCTION: Gestational diabetes mellitus (GDM) is a consequence of an imbalance between insulin sensitivity (IS) and secretion during pregnancy. MicroRNAs (miRNAs) are small and secreted RNA molecules stable in blood and known to regulate physiological processes including glucose homeostasis. The aim of this study was to identify plasmatic miRNAs detectable in early pregnancy predicting IS at 24th-29th week of pregnancy. RESEARCH DESIGN AND METHODS: We quantified circulating miRNAs in 421 women in plasma collected at 9.6±2.2 weeks of pregnancy using next-generation sequencing. RESULTS: we detected 2170 miRNAs: 39 (35 positively and 4 negatively) were associated with IS as estimated by the Matsuda Index at 26.4±1.0 weeks of pregnancy. Lasso regression identified 18 miRNAs independently predicting Matsuda Index-estimated IS. Together with gestational age, maternal age and body mass index at first trimester, they explain 36% of IS variance in late second trimester of pregnancy. These miRNAs regulate fatty acid biosynthesis and metabolism among other pathways. CONCLUSIONS: In summary, we have identified first trimester plasmatic miRNAs predictive of Matsuda Index-estimated IS in late second trimester of pregnancy. These miRNAs could also contribute to initiate and support IS adaptation to pregnancy potentially through lipid metabolism regulation.

Maternal Glycemic Dysregulation During Pregnancy and Neonatal Blood DNA Methylation: Meta-analyses of Epigenome-Wide Association Studies.

OBJECTIVE: Maternal glycemic dysregulation during pregnancy increases the risk of adverse health outcomes in her offspring, a risk thought to be linearly related to maternal hyperglycemia. It is hypothesized that changes in offspring DNA methylation (DNAm) underline these associations. RESEARCH DESIGN AND METHODS: To address this hypothesis, we conducted fixed-effects meta-analyses of epigenome-wide association study (EWAS) results from eight birth cohorts investigating relationships between cord blood DNAm and fetal exposure to maternal glucose (Nmaximum = 3,503), insulin (Nmaximum = 2,062), and area under the curve of glucose (AUCgluc) following oral glucose tolerance tests (Nmaximum = 1,505). We performed lookup analyses for identified cytosine-guanine dinucleotides (CpGs) in independent observational cohorts to examine associations between DNAm and cardiometabolic traits as well as tissue-specific gene expression. RESULTS: Greater maternal AUCgluc was associated with lower cord blood DNAm at neighboring CpGs cg26974062 (ß [SE] -0.013 [2.1 × 10-3], P value corrected for false discovery rate [PFDR] = 5.1 × 10-3) and cg02988288 (ß [SE]-0.013 [2.3 × 10-3], PFDR = 0.031) in TXNIP. These associations were attenuated in women with GDM. Lower blood DNAm at these two CpGs near TXNIP was associated with multiple metabolic traits later in life, including type 2 diabetes. TXNIP DNAm in liver biopsies was associated with hepatic expression of TXNIP. We observed little evidence of associations between either maternal glucose or insulin and cord blood DNAm. CONCLUSIONS: Maternal hyperglycemia, as reflected by AUCgluc, was associated with lower cord blood DNAm at TXNIP. Associations between DNAm at these CpGs and metabolic traits in subsequent lookup analyses suggest that these may be candidate loci to investigate in future causal and mediation analyses.

Human plasma pregnancy-associated miRNAs and their temporal variation within the first trimester of pregnancy.

BACKGROUND: During pregnancy, maternal metabolism undergoes substantial changes to support the developing fetus. Such changes are finely regulated by different mechanisms carried out by effectors such as microRNAs (miRNAs). These small non-coding RNAs regulate numerous biological functions, mostly through post-transcriptional repression of gene expression. miRNAs are also secreted in circulation by numerous organs, such as the placenta. However, the complete plasmatic microtranscriptome of pregnant women has still not been fully described, although some miRNA clusters from the chromosome 14 (C14MC) and the chromosome 19 (C19MC and miR-371-3 cluster) have been proposed as being specific to pregnancy. Our aims were thus to describe the plasma microtranscriptome during the first trimester of pregnancy, by assessing the differences with non-pregnant women, and how it varies between the 4th and the 16th week of pregnancy. METHODS: Plasmatic miRNAs from 436 pregnant (gestational week 4 to 16) and 15 non-pregnant women were quantified using Illumina HiSeq next-generation sequencing platform. Differentially abundant miRNAs were identified using DESeq2 package (FDR q-value ≤ 0.05) and their targeted biological pathways were assessed with DIANA-miRpath. RESULTS: A total of 2101 miRNAs were detected, of which 191 were differentially abundant (fold change < 0.05 or > 2, FDR q-value ≤ 0.05) between pregnant and non-pregnant women. Of these, 100 miRNAs were less and 91 miRNAs were more abundant in pregnant women. Additionally, the abundance of 57 miRNAs varied according to gestational age at first trimester, of which 47 were positively and 10 were negatively associated with advancing gestational age. miRNAs from the C19MC were positively associated with both pregnancy and gestational age variation during the first trimester. Biological pathway analysis revealed that these 191 (pregnancy-specific) and 57 (gestational age markers) miRNAs targeted genes involved in fatty acid metabolism, ECM-receptor interaction and TGF-beta signaling pathways. CONCLUSION: We have identified circulating miRNAs specific to pregnancy and/or that varied with gestational age in first trimester. These miRNAs target biological pathways involved in lipid metabolism as well as placenta and embryo development, suggesting a contribution to the maternal metabolic adaptation to pregnancy and fetal growth.

Early-pregnancy maternal body mass index is associated with common DNA methylation markers in cord blood and placenta: a paired-tissue epigenome-wide association study.

Women entering pregnancy with elevated body mass index (BMI) face greater risk of adverse outcomes during pregnancy, delivery, and for their offspring later in life, potentially via epigenetics. If epigenetic programming occurs early during in utero development, the differential marks should be detectable in multiple tissues despite the known unique epigenetic profile in each.We used early-pregnancy BMI as reflection of maternal metabolic milieu exposure in peri-conception and early-pregnancy period. We analysed DNA methylation in paired cord blood and placenta samples among 437 newborns from Gen3G, a pre-birth prospective cohort of primarily European descent. We measured DNA methylation in both tissues across the genome in >720,000 CpG sites using the Illumina MethylationEPIC array. At each site, we used linear mixed models (LMMs) with an unstructured variance-covariance matrix to test for an association between maternal early-pregnancy BMI and DNA methylation in both tissues (modelled as M-values). We adjusted for tissue-specific covariates, offspring sex, gestational age at delivery, and maternal smoking and age.Women had a mean (SD) BMI of 25.4 (5.7) kg/m2 measured at first trimester visit (mean=9.9 weeks). Early-pregnancy BMI was associated with differential DNA methylation levels in paired-tissue analyses at two sites: cg10593758 (ß=0.0126, SE=0.0025; P=4.07e-7), annotated to CRHBP, and cg0762168 (ß=-0.0094, SE=0.0018; P=2.78e-7), annotated to CCDC97.Application of LMMs in DNA methylation data from distinct fetal-origin tissues allowed us to identify CpG sites at which early-pregnancy BMI may have an epigenetic 'programming' effect on overall fetus development. One site (CRHBP) may play a role in hypothalamic-pituitary-adrenal axis regulation.

Associations between an integrated component of maternal glycemic regulation in pregnancy and cord blood DNA methylation.

Background: Previous studies suggest that fetal programming to hyperglycemia in pregnancy is due to modulation of DNA methylation (DNAm), but they have been limited in their maternal glycemic characterization. Methods: In the Gen3G study, we used a principal component analysis to integrate multiple glucose and insulin values measured during the second trimester oral glucose tolerance test. We investigated associations between principal components and cord blood DNAm levels in an epigenome-wide analysis among 430 mother-child pairs. Results: The first principal component was robustly associated with lower DNAm at cg26974062 (TXNIP; p = 9.9 × 10-9) in cord blood. TXNIP is a well-known DNAm marker for type 2 diabetes in adults. Conclusion: We hypothesize that abnormal glucose metabolism in pregnancy may program dysregulation of TXNIP across the life course.

Lay abstract Elevated maternal levels of glucose affect the in utero environment and play a crucial role in the adequate development of the fetus and the long-term health of the child. Increasing evidence shows that a regulatory process called DNA methylation (DNAm), which affects gene expression, may be an epigenetic mechanism responsible for linking in utero exposures and long-term health. In this study, we derived a marker reflecting elevated maternal glucose and insulin levels during pregnancy. Next, we used this marker to assess its association with DNAm measured in the child's cord blood collected at delivery. We found that overall higher circulating levels of both maternal glucose and insulin in pregnancy were related to cord blood DNAm at a gene called TXNIP. This gene has been previously recognized as a type 2 diabetes epigenetic signature in blood cells of adults from different populations. Thus, we may have identified a cord blood DNAm marker that signals long-term risk of diabetes over the life course.

Placental DNA methylation signatures of maternal smoking during pregnancy and potential impacts on fetal growth.

Maternal smoking during pregnancy (MSDP) contributes to poor birth outcomes, in part through disrupted placental functions, which may be reflected in the placental epigenome. Here we present a meta-analysis of the associations between MSDP and placental DNA methylation (DNAm) and between DNAm and birth outcomes within the Pregnancy And Childhood Epigenetics (PACE) consortium (N = 1700, 344 with MSDP). We identify 443 CpGs that are associated with MSDP, of which 142 associated with birth outcomes, 40 associated with gene expression, and 13 CpGs are associated with all three. Only two CpGs have consistent associations from a prior meta-analysis of cord blood DNAm, demonstrating substantial tissue-specific responses to MSDP. The placental MSDP-associated CpGs are enriched for environmental response genes, growth-factor signaling, and inflammation, which play important roles in placental function. We demonstrate links between placental DNAm, MSDP and poor birth outcomes, which may better inform the mechanisms through which MSDP impacts placental function and fetal growth.

Associations of maternal insulin resistance during pregnancy and offspring inflammation at birth and at 5 years of age: A prospective study in the Gen3G cohort.

BACKGROUND: Maternal insulin resistance is associated with greater maternal inflammation during pregnancy, but its relation to inflammation in offspring remains unclear. The goal of this study was to assess the relationship of gestational insulin resistance and other glycemic markers with offspring inflammation at birth and at 5 years of age. METHODS: We included 653 mother-child pairs from the prospective pre-birth Gen3G cohort. We examined maternal insulin and glucose levels measured during the second trimester of pregnancy, from which we derived the homeostatic model of assessment of insulin resistance (HOMA-IR) and the Matsuda index. We assessed offspring inflammation at birth and at 5 years of age by measuring plasma tumor necrosis factor-α (TNFα) concentrations. We conducted multivariable regression models to evaluate associations of each insulin and glucose marker with offspring inflammation adjusting for confounding variables. RESULTS: Higher levels of fasting insulin were associated with lower TNFα levels at birth (-0.78, 95% CI [-1.45, -0.11]), in the fully adjusted model. We observed similar associations with the HOMA-IR and opposite direction with the Matsuda index. We did not find persistence of the association between maternal fasting insulin and offspring TNFα at 5 years of age. CONCLUSIONS: Greater maternal insulin resistance during pregnancy was associated with lower cord blood TNFα levels in newborns. The mechanisms by which maternal insulin resistance may promote lower inflammatory levels in newborns are not fully understood and more research is needed to deepen our understanding of these mechanisms.