Narjes Madhloum

Air pollution-induced placental epigenetic alterations in early life: a candidate miRNA approach

ABSTRACT Particulate matter (PM) exposure during in utero life may entail adverse health outcomes in later-life. Air pollutions adverse effects are known to alter gene expression profiles, which can be regulated by microRNAs (miRNAs). We investigate the potential influence of air pollution exposure in prenatal life on placental miRNA expression. Within the framework of the ENVIRONAGE birth cohort, we measured the expression of six candidate miRNAs in placental tissue from 210 mother-newborn pairs by qRT-PCR. Trimester-specific PM2.5 exposure levels were estimated for each mothers home address using a spatiotemporal model. Multiple regression models were used to study miRNA expression and in utero exposure to PM2.5 over various time windows during pregnancy. The placental expression of miR-21 (−33.7%, 95% CI: −53.2 to −6.2, P = 0.022), miR-146a (−30.9%, 95% CI: −48.0 to −8.1, P = 0.012) and miR-222 (−25.4%, 95% CI: −43.0 to −2.4, P = 0.034) was inversely associated with PM2.5 exposure during the 2nd trimester of pregnancy, while placental expression of miR-20a and miR-21 was positively associated with 1st trimester exposure. Tumor suppressor phosphatase and tensin homolog (PTEN) was identified as a common target of the miRNAs significantly associated with PM exposure. Placental PTEN expression was strongly and positively associated (+59.6% per 5 µg/m³ increment, 95% CI: 26.9 to 100.7, P < 0.0001) with 3rd trimester PM2.5 exposure. Further research is required to establish the role these early miRNA and mRNA expression changes might play in PM-induced health effects. We provide molecular evidence showing that in utero PM2.5 exposure affects miRNAs expression as well as its downstream target PTEN.

Carotid Intima-Media Thickness, a Marker of Subclinical Atherosclerosis, and Particulate Air Pollution Exposure: the Meta-Analytical Evidence

Introduction Studies on the association between atherosclerosis and long-term exposure to ambient air pollution suggest that carotid intima-media thickness (CIMT), a marker of subclinical atherosclerosis, is positively associated with particulate matter (PM) exposure. However, there is heterogeneity between the different studies concerning the magnitude of this association. We performed a meta-analysis to determine the strength of the association between CIMT and particulate air pollution. Methods We queried PubMed citation database and Web of Knowledge up to March 2015 in order to identify studies on CIMT and particulate air pollution. Two investigators selected and computerized all relevant information, independently. Eight of the reviewed epidemiological publications provided sufficient details and met our inclusion criteria. Descriptive and quantitative information was extracted from each selected study. The meta-analysis included 18,349 participants from eight cohorts for the cross-sectional association between CIMT and PM and 7,268 participants from three cohorts for the longitudinal analysis on CIMT progression and PM exposure. Results The average exposure to PM2.5 in the different study populations ranged from 4.1 to 20.8 µg/m3 and CIMT averaged (SD) 0.73 (0.14) mm. We computed a pooled estimate from a random-effects model. In the combined cross-sectional studies, an increase of 5 µg/m3 PM2.5 was associated with a 1.66% (95% CI: 0.86 to 2.46; P<0.0001) thicker CIMT, which corresponds to an average increase of 12.1 µm. None of the studies moved the combined estimate outside the confidence interval of the overall estimate. A funnel plot suggested absence of publication bias. The combined longitudinal estimate showed for each 5 µg/m3 higher PM2.5 exposure, a 1.04 µm per year (95% CI: 0.01 to 2.07; P=0.048) greater CIMT progression. Conclusion Our meta-analysis supports the evidence of a positive association between CIMT, a marker of subclinical atherosclerosis, and long-term exposure to particulate air pollution.

Placental Nitrosative Stress and Exposure to Ambient Air Pollution During Gestation: A Population Study

The placenta plays a crucial role in fetal growth and development through adaptive responses to perturbations of the maternal environment. We investigated the association between placental 3-nitrotyrosine (3-NTp), a biomarker of oxidative stress, and exposure to air pollutants during various time windows of pregnancy. We measured the placental 3-NTp levels of 330 mother-newborn pairs enrolled in the Environmental Influence on Ageing in Early Life (ENVIRONAGE) Study, a Belgian birth cohort study (2010-2013). Daily concentrations of particulate matter with an aerodynamic diameter ≤2.5 µm (PM2.5), black carbon (BC), and nitrogen dioxide were interpolated for each mothers residence using a spatiotemporal interpolation method. Placental 3-NTp levels, adjusted for covariates, increased by 35.0% (95% confidence interval (CI): 13.9, 60.0) for each interquartile-range increment in entire-pregnancy PM2.5 exposure. The corresponding estimate for BC exposure was 13.9% (95% CI: -0.21, 29.9). These results were driven by the first (PM2.5: 29.0% (95% CI: 4.9, 58.6); BC: 23.6% (95% CI: 4.4, 46.4)) and second (PM2.5: 39.3% (95% CI: 12.3, 72.7)) gestational exposure windows. This link between placental nitrosative stress and exposure to fine particle air pollution during gestation is in line with experimental evidence on cigarette smoke and diesel exhaust exposure. Further research is needed to elucidate potential health consequences experienced later in life through particle-mediated nitrosative stress incurred during fetal life.

Cohort Profile: The ENVIRonmental influence ON early AGEing (ENVIRONAGE): a birth cohort study

The ENVIRONAGE birth cohort is supported by the European Research Council [ERC-2012-StG.310898], and by funds of the Flemish Scientific Research council [FWO, G.0.733.15.N]. Bianca Cox, Janneke Hogervorst and Karen Vrijens have a postdoctoral fellowship from the Research Foundation - Flanders (FWO).

Fetal Thyroid Function, Birth Weight, and in Utero Exposure to Fine Particle Air Pollution: A Birth Cohort Study.

Background: Thyroid hormones are critical for fetal development and growth. Whether prenatal exposure to fine particle air pollution (≤ 2.5 μm; PM2.5) affects fetal thyroid function and what the impact is on birth weight in normal healthy pregnancies have not been studied yet. Objectives: We studied the impact of third-trimester PM2.5 exposure on fetal and maternal thyroid hormones and their mediating role on birth weight. Methods: We measured the levels of free thyroid hormones (FT3, FT4) and thyroid-stimulating hormone (TSH) in cord blood (n = 499) and maternal blood (n = 431) collected after delivery from mother–child pairs enrolled between February 2010 and June 2014 in the ENVIRONAGE birth cohort with catchment area in the province of Limburg, Belgium. Results: An interquartile range (IQR) increment (8.2 μg/m3) in third-trimester PM2.5 exposure was inversely associated with cord blood TSH levels (–11.6%; 95% CI: –21.8, –0.1) and the FT4/FT3 ratio (–62.7%; 95% CI: –91.6, –33.8). A 10th–90th percentile decrease in cord blood FT4 levels was associated with a 56 g decrease in mean birth weight (95% CI: –90, –23). Assuming causality, we estimated that cord blood FT4 mediated 21% (–19 g; 95% CI: –37, –1) of the estimated effect of an IQR increment in third-trimester PM2.5 exposure on birth weight. Third-trimester PM2.5 exposure was inversely but not significantly associated with maternal blood FT4 levels collected 1 day after delivery (–4.0%, 95% CI: –8.0, 0.2 for an IQR increment in third-trimester PM2.5). Conclusions: In our study population of normal healthy pregnancies, third-trimester exposure to PM2.5 air pollution was associated with differences in fetal thyroid hormone levels that may contribute to reduced birth weight. Additional research is needed to confirm our findings in other populations and to evaluate potential consequences later in life. Citation: Janssen BG, Saenen ND, Roels HA, Madhloum N, Gyselaers W, Lefebvre W, Penders J, Vanpoucke C, Vrijens K, Nawrot TS. 2017. Fetal thyroid function, birth weight, and in utero exposure to fine particle air pollution: a birth cohort study. Environ Health Perspect 125:699–705; http://dx.doi.org/10.1289/EHP508

Neonatal Cord Blood Oxylipins and Exposure to Particulate Matter in the Early-Life Environment: An ENVIRONAGE Birth Cohort Study

Background: As part of the lipidome, oxylipins are bioactive lipid compounds originating from oxidation of different fatty acids. Oxylipins could provide a new target in the developmental origins model or the ability of early life exposure to change biology. Objectives: We studied the association between in utero PM2.5 (particulate matter with aerodynamic diameter < 2.5 μm) exposure and oxylipin profiles in newborns. Methods: Thirty-seven oxylipins reflecting the cyclooxygenase (COX), lipoxygenase (5-LOX and 12/15-LOX), and cytochrome P450 (CYP) pathways were assayed in 197 cord blood plasma samples from the ENVIRONAGE birth cohort. Principal component (PC) analysis and multiple regression models were used to estimate associations of in utero PM2.5 exposure with oxylipin pathways and individual metabolites. Results: A principal component representing the 5-LOX pathway (6 metabolites) was significantly positively associated with PM2.5 exposure during the entire (multiple testing–adjusted q-value = 0.05) and second trimester of pregnancy (q = 0.05). A principal component representing the 12/15-LOX pathway (11 metabolites) was positively associated with PM2.5 exposure during the second trimester of pregnancy (q = 0.05). PM2.5 was not significantly associated with the COX pathway during any time period. There was a positive but nonsignificant association between second-trimester PM2.5 and the CYP pathway (q = 0.16). Conclusion: In utero exposure to particulate matter, particularly during the second trimester, was associated with differences in the cord blood levels of metabolites derived from the lipoxygenase pathways. These differences may indicate an effect of air pollution during in utero life on the inflammatory state of the newborn at birth. Oxylipins may be important mediators between early life exposures and health outcomes later in life. Citation: Martens DS, Gouveia S, Madhloum N, Janssen BG, Plusquin M, Vanpoucke C, Lefebvre W, Forsberg B, Nording M, Nawrot TS. 2017. Neonatal cord blood oxylipins and exposure to particulate matter in the early-life environment: an ENVIRONAGE birth cohort study. Environ Health Perspect 125:691–698; http://dx.doi.org/10.1289/EHP291

Mother’s Pre-pregnancy BMI and Placental Candidate miRNAs: Findings from the ENVIR ON AGE Birth Cohort

There is increasing evidence that the predisposition for development of chronic diseases arises at the earliest times of life. In this context, maternal pre-pregnancy weight might modify fetal metabolism and the child’s predisposition to develop disease later in life. The aim of this study is to investigate the association between maternal pre-pregnancy body mass index (BMI) and miRNA alterations in placental tissue at birth. In 211 mother-newborn pairs from the ENVIRONAGE birth cohort, we assessed placental expression of seven miRNAs important in crucial cellular processes implicated in adipogenesis and/or obesity. Multiple linear regression models were used to address the associations between pre-pregnancy BMI and placental candidate miRNA expression. Maternal pre-pregnancy BMI averaged (±SD) 23.9 (±4.1) kg/m2. In newborn girls (not in boys) placental miR-20a, miR-34a and miR-222 expression was lower with higher maternal pre-pregnancy BMI. In addition, the association between maternal pre-pregnancy BMI and placental expression of these miRNAs in girls was modified by gestational weight gain. The lower expression of these miRNAs in placenta in association with pre-pregnancy BMI, was only evident in mothers with low weight gain (<14 kg). The placental expression of miR-20a, miR-34a, miR-146a, miR-210 and miR-222 may provide a sex-specific basis for epigenetic effects of pre-pregnancy BMI.

Cord plasma insulin and in utero exposure to ambient air pollution

INTRODUCTION Cardio-metabolic risk factors including insulin levels are at young age barely perceived as harmful, but over time these risk factors may track and lead to higher risk of metabolic syndrome. Studies showed that exposure to air pollution is associated with an increased risk of insulin resistance in childhood. We determined whether the origin of type 2 diabetes can be found in the early childhood by examining the levels of insulin in the neonatal cord blood and whether this can be considered as a disease marker for later life. METHODS In the ENVIRONAGE (ENVIRonmental influence ON early AGEing) birth cohort, we recruited 620 mother-infant pairs between February 2nd 2010 until August 12th 2014 at the East-Limburg Hospital in Genk, Belgium. We investigated in 590 newborns the association between cord plasma insulin levels and exposure to particulate matter (PM2.5 and PM10) and nitrogen dioxide (NO2) in various exposure windows during pregnancy. Trimester-specific air pollutant exposure levels were estimated for each mothers home address using a spatiotemporal model. RESULTS Cord plasma insulin levels averaged 33.1pmol/L (25-75th percentile: 20.1-53.5), while PM2.5 exposure during pregnancy averaged (SD) 13.7μg/m3 (2.4). Independent of maternal age, newborns sex, birth weight, gestational age, parity, early-pregnancy BMI, ethnicity, smoking status, time of the day, maternal education, time of delivery, and season of delivery, cord plasma insulin levels increased with 15.8% (95% CI 7.8 to 24.4, p<0.0001) for each SD increment in PM2.5 levels during the entire pregnancy and was most pronounced in the 2nd trimester (13.1%, 95% CI 3.4 to 23.7, p=0.007) of pregnancy. The results for PM10 exposure were similar with those of PM2.5 exposure but we did not observe an association between cord blood insulin levels and NO2 exposure. CONCLUSIONS Exposure to particulate air pollution during pregnancy is associated with increased levels of cord plasma insulin at birth. The public health relevance of this association is demonstrated by the fact that a 2.4μg/m3 (SD) increase in PM2.5 during pregnancy on cord plasma insulin levels corresponds to the effect-size of a 9kg/m2 higher early-pregnancy BMI on cord plasma. Particulate air pollution induced changes in cord plasma insulin levels during early life and might be a risk factor in the development of metabolic disease, such as glucose intolerance or type 2 diabetes, later in life.

Author Correction: Mother’s Pre-pregnancy BMI and Placental Candidate miRNAs: Findings from the ENVIR ON AGE Birth Cohort

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Sex-specific associations between telomere length and candidate miRNA expression in placenta

BackgroundIn the early-life environment, proper development of the placenta is essential for both fetal and maternal health. Telomere length at birth has been related to life expectancy. MicroRNAs (miRNAs) as potential epigenetic determinants of telomere length at birth have not been identified. In this study, we investigate whether placental miRNA expression is associated with placental telomere length at birth.MethodsWe measured the expression of seven candidate miRNAs (miR-16-5p, -20a-5p, -21-5p, -34a-5p, 146a-5p, -210-3p and -222-3p) in placental tissue at birth in 203 mother-newborn (51.7% girls) pairs from the ENVIRONAGE birth cohort. We selected miRNAs known to be involved in crucial cellular processes such as inflammation, oxidative stress, cellular senescence related to aging. Placental miRNA expression and relative average placental telomere length were measured using RT-qPCR.ResultsBoth before and after adjustment for potential covariates including newborn’s ethnicity, gestational age, paternal age, maternal smoking status, maternal educational status, parity, date of delivery and outdoor temperature during the 3rd trimester of pregnancy, placental miR-34a, miR-146a, miR-210 and miR-222 expression were significantly (p ≤ 0.03) and positively associated with placental relative telomere length in newborn girls. In newborn boys, only higher expression of placental miR-21 was weakly (p = 0.08) associated with shorter placental telomere length. Significant miRNAs explain around 6–8% of the telomere length variance at birth.ConclusionsPlacental miR-21, miR-34a, miR-146a, miR-210 and miR-222 exhibit sex-specific associations with telomere length in placenta. Our results indicate miRNA expression in placental tissue could be an important determinant in the process of aging starting from early life onwards.