Maternal blood metal levels and fetal markers of metabolic function

Arsenic and adipose tissue: an unexplored pathway for toxicity and metabolic dysfunction

Arsenic-contaminated drinking water can induce various disorders by disrupting lipid and glucose metabolism in adipose tissue, leading to insulin resistance. It inhibits adipocyte development and exacerbates insulin resistance, though the precise impact on lipid synthesis and lipolysis remains unclear. This review aims to explore the processes and pathways involved in adipogenesis and lipolysis within adipose tissue concerning arsenic-induced diabetes. Although arsenic exposure is linked to type 2 diabetes, the specific role of adipose tissue in its pathogenesis remains uncertain. The review delves into arsenic's effects on adipose tissue and related signaling pathways, such as SIRT3-FOXO3a, Ras-MAP-AP-1, PI(3)-K-Akt, endoplasmic reticulum stress proteins, CHOP10, and GPCR pathways, emphasizing the role of adipokines. This analysis relies on existing literature, striving to offer a comprehensive understanding of different adipokine categories contributing to arsenic-induced diabetes. The findings reveal that arsenic detrimentally impacts white adipose tissue (WAT) by reducing adipogenesis and promoting lipolysis. Epidemiological studies have hinted at a potential link between arsenic exposure and obesity development, with limited research suggesting a connection to lipodystrophy. Further investigations are needed to elucidate the mechanistic association between arsenic exposure and impaired adipose tissue function, ultimately leading to insulin resistance.

Associations Between Prenatal Blood Metals and Vitamins and Cord Blood Peptide Hormone Concentrations

Background

Nonessential metals have endocrine disrupting properties, interfere with cellular processes, generate reactive oxygen and deplete antioxidants, while essential metals and vitamins act as antioxidants. The extent to which prenatal metals and vitamins are associated with cord blood hormones involved in maternal and fetal metabolic and growth processes is unknown.

Methods

We measured six nonessential (arsenic, barium, cadmium, cesium, lead, mercury) and four essential (magnesium, manganese, selenium, zinc) metals and trace elements, and two vitamins (B12 and folate) in first trimester blood from participants in the longitudinal pre-birth Project Viva cohort, who were recruited between 1999-2002 in eastern Massachusetts. We measured adiponectin, C-peptide, IGF-1, IGF-2, IGFBP-3, insulin, and leptin concentrations in cord blood (~n=695). We used covariate-adjusted quantile g-computation for mixtures and linear regression for individual exposures to estimate associations with cord blood peptide hormones.

Results

The essential metal mixture (magnesium, manganese, selenium, zinc) was associated with higher IGF-1 (β=3.20 ng/ml per quartile, 95% CI: 0.39, 6.01), IGF-2 (β=10.93 ng/ml, 95% CI: 0.08, 21.79), and leptin (β=1.03 ng/ml, 95% CI: 0.25, 1.80). Magnesium was associated with higher leptin (β=2.90 ng/ml, 95% CI: 0.89, 4.91), while B12 was associated with lower adiponectin, IGF-2, and leptin, but higher C-peptide. Other individual nonessential metals were associated with cord blood hormones.

Conclusions

Our findings suggest that some prenatal metals and vitamins are associated with cord blood hormones, which may influence growth and development.

The Association among Urinary Lead and Cadmium, Serum Adiponectin, and Serum Apoptotic Microparticles in a Young Taiwanese Population

Previous studies reported that lead (Pb) and cadmium (Cd) exposure are linked to changes in serum adiponectin; an adipokine that promotes glycolysis and inhibits gluconeogenesis to regulate glucose metabolism. However, no study has ever explored the relationship between exposure to these two heavy metals and adiponectin in adolescents and young adults. Additionally, the role of adiponectin in the relationship between Pb and Cd exposure and vascular endothelial cell apoptosis has never been investigated. In this study, 724 Taiwanese participants, aged 12 to 30 years, were enrolled to investigate the association among urinary lead and cadmium, serum adiponectin, and apoptotic microparticles (CD31+/CD42a-, CD31+/CD42a+, and CD14). The results of the current study revealed a statistically significant inverse association between urine Pb and Cd levels and adiponectin levels, as well as a positive association with apoptotic microparticles (CD31+/CD42a-, CD31+/CD42a+, and CD14). Adiponectin was also inversely correlated with CD31+/CD42a- and CD31+/CD42a+. Moreover, when subjects with both Pb and Cd levels above the 50th percentile were compared to those below it, the former group exhibited the lowest average adiponectin value. Additionally, a more pronounced positive association between heavy metals and apoptotic microparticles (CD31+/CD42a- and CD31+/CD42a+) was observed when adiponectin levels were lower. Furthermore, an interaction between adiponectin and heavy metals was identified in the relationship between these metals and CD31+/CD42a-. In conclusion, these findings suggest that Pb and Cd exposure may have an adverse effect on adiponectin, and it may play a role in the link between heavy metal exposure and the dysfunction of vascular endothelial cells. Future studies are needed to establish whether a causal relationship exists.

Associations of Prenatal First Trimester Essential and Nonessential Metal Mixtures with Body Size and Adiposity in Childhood

BACKGROUND

Prenatal nonessential metals may contribute to postnatal adiposity, whereas essential metals may have metabolic benefits. We evaluated joint and individual associations between prenatal metals and childhood adiposity.

METHODS

We measured concentrations of six nonessential (arsenic, barium, cadmium, cesium, lead, and mercury) and four essential (magnesium, manganese, selenium, and zinc) metals in first trimester maternal blood from a prebirth cohort. We collected anthropometric measures in early childhood, mid-childhood, and early adolescence including subscapular+tricep skinfold thickness (mm) (N = 715-859), waist circumference (cm) (N = 717-882), and body mass index (BMI) (z-score) (N = 716-875). We measured adiposity in mid-childhood and early adolescence using bone densitometry total- and trunk- fat mass index (kg/m 2 ) (N = 511-599). We estimated associations using adjusted quantile g-computation and linear regression.

RESULTS

The nonessential metal mixture was associated with higher total (β = 0.07, 95% CI = 0.01, 0.12) and trunk fat mass index (β = 0.12, CI = 0.02, 0.22), waist circumference (β = 0.01, CI = 0.00, 0.01), and BMI (β = 0.24, CI = 0.07, 0.41) in mid-childhood, and total fat mass index (β = 0.07, CI = 0.01, 0.14), and BMI (β = 0.19, CI = 0.02, 0.37) in early adolescence. The essential metal mixture was associated with lower early adolescence total-(β = -0.11, CI = -0.17, -0.04) and trunk- fat mass index (β = -0.13, CI = -0.21, -0.05), subscapular+tricep skinfold thickness (β = -0.02, CI = -0.03, -0.00), waist circumference (β = -0.003, CI = -0.01, -0.00), and BMI (β = -0.16, CI = -0.28, -0.04). Cadmium and cesium were individually associated with childhood adiposity at different timepoints.

CONCLUSIONS

Prenatal first-trimester essential metals were associated with lower childhood adiposity, whereas nonessential metals were associated with higher adiposity into adolescence.

Joint associations among prenatal metal mixtures and nutritional factors on birth weight z-score: Evidence from an urban U.S. population

The benefits of nutritional factors on birth outcomes have been recognized, however, limited studies have examined the role of nutritional factors in mitigating the detrimental effects of metals exposure during gestation. We used data collected from 526 mother-infant dyads enrolled in the Programming of Intergenerational Stress Mechanisms longitudinal pregnancy cohort to examine the joint effects of prenatal exposure to metals and maternal nutrition on birth weight for gestational age (BWGA) z-scores. We measured concentrations of twelve metals and trace elements in urine samples collected during pregnancy. Maternal nutritional intake was measured using the Block98 Food Frequency Questionnaire and converted into energy-adjusted consumption of individual nutrients. Using multivariable linear regression and Bayesian Kernel Machine Regression, we found that three metals [cobalt (Co), nickel (Ni), and lead (Pb)] and five metals [barium (Ba), caesium (Cs), copper (Cu), Ni, and zinc (Zn)] were associated with BWGA z-score in male and female infants, respectively. When examining the sex-specific interactions between these metals and nutrient groups [macro nutrients, minerals, A vitamins, B vitamins, anti-oxidant, methyl-donor nutrients, and inflammatory (pro- and anti-)] using a Cross-validated Kernel Ensemble model, we identified significant interactions between the macro nutrients and Co (p = 0.05), minerals and Pb (p = 0.04), and A vitamins and Ni (p = 0.001) in males. No significant interactions were found in females. Furthermore, three minerals (phosphorus, iron, potassium) and vitamin A were found to be more crucial than other nutrients in modifying the association between each respective metal and BWGA z-score in males. A better understanding of the sex-specific interactions between nutrients and metals on birth weight can guide pregnant women to protect their neonates from the adverse health impacts of metal exposures by optimizing nutrient intakes accordingly.

Ambient air pollution during pregnancy and cardiometabolic biomarkers in cord blood

Prenatal air pollution exposure has been associated with adverse childhood cardiometabolic outcomes. It is unknown whether evidence of metabolic disruption associated with air pollution is identifiable at birth. We examined exposure to prenatal ambient air pollution and cord blood cardiometabolic biomarkers among 812 mother-infant pairs in the Healthy Start study.

Developmental Exposure to Endocrine Disrupting Chemicals and Its Impact on Cardio-Metabolic-Renal Health

Developmental origin of health and disease postulates that the footprints of early life exposure are followed as an endowment of risk for adult diseases. Epidemiological and experimental evidence suggest that an adverse fetal environment can affect the health of offspring throughout their lifetime. Exposure to endocrine disrupting chemicals (EDCs) during fetal development can affect the hormone system homeostasis, resulting in a broad spectrum of adverse health outcomes. In the present review, we have described the effect of prenatal EDCs exposure on cardio-metabolic-renal health, using the available epidemiological and experimental evidence. We also discuss the potential mechanisms of their action, which include epigenetic changes, hormonal imprinting, loss of energy homeostasis, and metabolic perturbations. The effect of prenatal EDCs exposure on cardio-metabolic-renal health, which is a complex condition of an altered biological landscape, can be further examined in the case of other environmental stressors with a similar mode of action.

Leptin and adiponectin synthesis and secretion in mature 3T3-L1 adipocytes are differentially down-regulated by arsenic and palmitic acid exposure throughout different stages of adipogenesis

AIMS

Arsenic is a risk factor for type 2 diabetes and cardiovascular disease. However, little is known about arsenic effects over adipocyte endocrine functionality, particularly for leptin and adiponectin, and about its interaction with dietary components, which are the main environmental regulators of adipose tissue functionality. The aim of this work was to evaluate leptin and adiponectin in mature 3T3-L1 adipocytes exposed to palmitate (simulating excess fat intake), arsenite, or both throughout two different stages of adipogenesis.

MATERIAL AND METHODS

3T3-L1 adipocytes were exposed starting from the beginning of its differentiation process during 11 d or once adipocytes were mature for 72 h. Adipokines secretion was evaluated by ELISA, intracellular protein levels and secreted adiponectin multimers by Western blot and mRNA abundance by qPCR.

KEY FINDINGS

Leptin and adiponectin secretion decreased by arsenite alone or in combination with palmitate due to reduced gene and protein expression of both adipokines. However, leptin was impaired more at the transcriptional level, whereas affections to adiponectin were more relevant at the intracellular protein amount level with changes in the multimers proportion. The gene expression of several of their transcription factors was altered. Additionally, the magnitude of the effects depends on the adipocyte cell stage at which exposure began; adiponectin was more affected when exposure started from differentiation and leptin once adipocytes were mature.

SIGNIFICANCE

These results in an in vivo model could be translated into less satiety and reduced insulin sensitivity.

Urinary metals and adipokines in midlife women: The Study of Women's Health Across the nation (SWAN)

BACKGROUND

Information on the associations between metal exposures and adipokines in human populations is limited and results are inconsistent. We evaluated the associations between metals and adipokines.

METHODS

Urinary concentrations of 15 metals (arsenic, barium, cadmium, cobalt, cesium, copper, mercury, manganese, molybdenum, nickel, lead, antimony, tin, thallium, and zinc) were measured in 1999-2000 among 1228 women of the Study of Women's Health Across the Nation Multi-Pollutant Study. Serum adipokines including high molecular weight (HMW)-adiponectin, leptin, and soluble leptin receptor (sOB-R) were measured at the follow-up visit (2002-2003). Linear regression models with adaptive elastic-net (AENET) were fit to identify metals associated with adipokines and to compute estimated percent changes in adipokines for one standard deviation increase in log-transformed urinary metal concentrations.

RESULTS

After adjustment for confounders, urinary molybdenum was associated with a 5.54% higher level (95% CI: 1.36%, 9.90%), whereas cadmium was associated with a 4.53% lower level (95% CI: -8.17%, -0.76%) of HMW-adiponectin. Urinary molybdenum was also associated with a 5.95% lower leptin level (95% CI: -10.15%, -1.56%) and a 2.98% (95% CI: 0.69%, 5.32%) higher sOB-R level. Urinary cesium and lead were associated with a 3.58% (95% CI: -6.06%, -1.03%) and a 2.53% (95% CI: -4.80%, -0.21%) lower level of sOB-R, respectively.

CONCLUSIONS

Our findings suggest that molybdenum was associated with favorable profiles of HMW-adiponectin, leptin, and sOB-R. Exposures to cadmium, cesium, and lead were associated with adverse adipokine profiles.

Toxic metal (Cd, Hg, Mn, Pb) partition in the maternal/foetal unit: A systematic mini - review of recent epidemiological studies

The aim of this study was to summarise the available information regarding the partition of toxic metal (Cd, Hg, Mn, Pb) levels in the maternal/foetal unit from large epidemiological studies. We performed a systematic search of PubMed/MedLine, EMBASE, and ISI Web of Science for papers on Cd, total Hg, Mn or Pb levels in the maternal/cord blood that were published in English (n > = 200; 2010-2017). Data on year of publication, sample size, location, year of survey, and main results were extracted. We found a total of 35 papers. Most studies included large convenience samples of healthy pregnant women. The maternal/cord blood was properly used as a biomarker of prenatal exposure to toxic metals. The partition of these toxic metal levels in the maternal/foetal unit was metal-specific. Cd median levels (IQR) in cord blood reported worldwide were much lower [∼ 70 % < LOD = ± 0.11 μg/L] than those found in maternal blood [0.23 μg/L (0.15-0.35), ∼ 65 % > LOD]. Considering that Cd was under LOD in 70 % of the cord blood, Cd cord:maternal ratio as well as Cd cord proportion were not provided. Total Hg median levels (IQR) in cord blood [0.75 μg/L (0.40-1.19), ∼30 % < LOD = ±0.35 μg/L] were usually higher than in maternal blood [0.55 μg/L (0.40-0.85), ∼ 10 % < LOD = ±0.15 μg/L]. Hg cord:maternal ratio was 1.34 (1.00-1.91), and infants born would have Hg cord:(cord + maternal) proportion ranged from 0.50 to 0.63. Mn was the only metal that was detected in 100 % in both maternal (LOD : ±0.50 μg/L) and cord (LOD = ±0.2 μg/L) blood. Mn median levels (IQR) in cord blood [32.96 μg/L (26.90-40.10)] were 2 times higher than in maternal blood [14.01 μg/L (11.50-17.58)]. Mn cord:maternal ratio was 2.35 (1.09-3.80), and infants born would have Mn proportion ranged from 0.52 to 0.79. Pb median levels (IQR) in cord blood [5.79 μg/L (4.34-8.38), ∼ 5% < LOD : ±2.07 μg/L] were usually equal to or lower than those reported in maternal blood [8.07 μg/L (5.79-10.76), ∼ 1% < LOD = ±1.03 μg/L]. Pb cord:maternal ratio was 0.71 (0.59-0.96), and infants born would have Pb proportion ranged from 0.37 to 0.49. Globally, the results indicate that total Hg and Mn levels were lower in maternal blood but higher in cord blood. However, much greater variability was seen with Cd and Pb. At delivery, total Hg and Pb levels in maternal blood were strong predictors of cord blood levels. Our findings empty that understanding the partition, levels and correlations of toxic metals in the maternal/cord blood may help to elucidate the adverse effects of these metals on foetuses and neonates.

Natural compounds attenuate heavy metal-induced PC12 cell damage

Objectives

To investigate the neuroprotective effects of six natural compounds (caffeine, gallic acid, resveratrol, epigallocatechin gallate [EGCG], L-ascorbic acid and alpha tocopherol [Vitamin E] on heavy metal-induced cell damage in rat PC12 cells.

Methods

In this in vitro experiment, rat PC12 cells were exposed to four heavy metals (CdCl₂, HgCl₂, CoCl₂ and PbCl₂) at different concentrations and cell apoptosis, necrosis and oxidative stress were assessed with and without the addition of the six natural compounds.

Results

The metals decreased cell viability but the natural compounds attenuated their effects on apoptosis, necrosis and reactive oxygen species (ROS) levels. Mitochondrial protein changes were involved in the regulation.

Conclusion

Overall, the natural compounds did provide protection against the metal-induced PC12 cell damage. These data suggest that natural compounds may have therapeutic potential against metal-induced neurodegenerative disease.

Maternal chronic stress correlates with serum levels of cortisol, glucose and C-peptide in the fetus, and maternal non chronic stress with fetal growth

INTRODUCTION

During pregnancy, maternal stressors cause changes in both maternal and fetal HPA axes. We therefore investigated the impact of maternal non chronic and chronic stress on fetal glucose metabolism and growth, and serum levels of cortisol in the fetus.

MATERIALS AND METHODS

Normal weight pregnant women (n = 192; mean ± SD 27.9 ± 4.2 years old, and; 26.9 ± 2.4 kg/m²) were assessed during the 2nd and 3rd trimester with anthropometry, fetal ultrasound, blood samples for serum CRH, cortisol and IL6, and STAI trait and state stress questionnaires. We measured serum cortisol, insulin and c-peptide, and plasma glucose from cord blood. Neonates underwent anthropometry at the 3rd post-delivery day.

RESULTS

In both 2nd and 3rd trimesters, women with STAI trait scores ≥40 had significantly greater levels of fasting serum CRH and cortisol than those with STAI trait scores<40. 2nd trimester: STAI trait scores correlated positively with cord blood glucose and c-peptide. Maternal serum CRH correlated negatively with U/S fetal biparietal head diameter, while serum cortisol correlated positively with abdominal circumference. Maternal serum IL6, CRH and cortisol all correlated positively with birth waist circumference. 3rd trimester: Women with STAI state scores ≥40 had fetuses with larger U/S abdominal and smaller head circumferences compared to those of women with STAI scores <40. Women with STAI trait scores ≥40 had greater levels of cord blood cortisol, glucose, and c-peptide compared to women with STAI scores <40. STAI state scores ≥40 correlated positively with maternal CRH and U/S fetal abdominal circumference, and negatively with fetal head circumference and biparietal diameter. STAI trait scores correlated positively with cord blood c-peptide, glucose, insulin and cortisol. Maternal serum levels of CRH correlated positively with U/S fetal abdominal circumference and cord blood cortisol, and negatively with fetal head circumference and biparietal head diameter. Maternal serum levels of both CRH and cortisol correlated positively with cord blood c-peptide, glucose, and insulin. STAI trait was the best positive predictor of cord blood cortisol, glucose and c-peptide, whilst STAI state was the best positive and negative predictor, respectively of fetal abdominal circumference and fetal head circumference or biparietal diameter.

CONCLUSIONS

Increased maternal chronic stress (reflected by the STAI trait score) associates with increased fetal cortisol, glucose, c-peptide secretion and thus, insulin resistance. Maternal non chronic stress (STAI state) in the 3rd trimester associates with changes in fetal growth pattern, including increased and decreased measurements of fetal abdominal and head growth respectively.

Prenatal Metal Concentrations and Childhood Cardiometabolic Risk Using Bayesian Kernel Machine Regression to Assess Mixture and Interaction Effects

BACKGROUND

Trace metal concentrations may affect cardiometabolic risk, but the role of prenatal exposure is unclear. We examined (1) the relation between blood metal concentrations during pregnancy and child cardiometabolic risk factors; (2) overall effects of metals mixture (essential vs. nonessential); and (3) interactions between metals.

METHODS

We measured 11 metals in maternal second-trimester whole blood in a prospective birth cohort in Mexico City. In children 4-6 years old, we measured body mass index (BMI), percent body fat, and blood pressure (N = 609); and plasma hemoglobin A1C (HbA1c), non-high-density lipoprotein (HDL) cholesterol, triglycerides, leptin, and adiponectin (N = 411). We constructed cardiometabolic component scores using age- and sex-adjusted z scores and averaged five scores to create a global risk score. We estimated linear associations of each metal with individual z scores and used Bayesian Kernel Machine Regression to assess metal mixtures and interactions.

RESULTS

Higher total metals were associated with lower HbA1c, leptin, and systolic blood pressure, and with higher adiponectin and non-HDL cholesterol. We observed no interactions between metals. Higher selenium was associated with lower triglycerides in linear (β = -1.01 z score units per 1 unit ln(Se), 95% CI = -1.84, -0.18) and Bayesian Kernel Machine Regression models. Manganese was associated with decreased HbA1c in linear models (β = -0.32 and 95% CI = -0.61, -0.03). Antimony and arsenic were associated with lower leptin in Bayesian Kernel Machine Regression models. Essential metals were more strongly associated with cardiometabolic risk than were nonessential metals.

CONCLUSIONS

Low essential metals during pregnancy were associated with increased cardiometabolic risk factors in childhood.

Association between prenatal bisphenol A and phthalate exposures and fetal metabolic related biomarkers: The Hokkaido study on Environment and Children's Health

Bisphenol A and phthalates are widely detected in human urine, blood, breast milk, and amniotic fluid. Both bisphenol A and phthalates have been suggested as playing a role in obesity epidemics. Exposure to these chemicals during fetal development, and its consequences should be concerning because they can cross the placenta. Thus, this study aimed to assess the association between prenatal exposure to bisphenol A and phthalates, and cord blood metabolic-related biomarkers. Maternal serum was used during the first trimester, to determine prenatal exposure to bisphenol A and phthalates. Levels of metabolic-related biomarkers in the cord blood were also determined. Linear regression models were applied to the 365 participants with both, exposure and biomarker assessments, adjusted for maternal age, pre-pregnancy body mass index, parity, education, and sex of the child. The level of bisphenol A was negatively associated with the leptin level (β = -0.06, 95% confidence interval [CI]: -0.11, -0.01), but was positively associated with the high-molecular-weight adiponectin level, with marginal significance (β = 0.03, 95%CI: 0.00, 0.06). The mono-isobutyl phthalate (MiBP), mono-n-butyl phthalate (MnBP), mono-(2-ethylhexyl) phthalate (MEHP), and summation of MEHP and MECPP to represent DEHP exposure (∑DEHPm) levels were inversely associated with the leptin levels (β=-0.14, 95%CI: -0.27, -0.01; β = -0.12, 95%CI: -0.24, 0.00 with marginal significance; β=0.08, 95%CI: -0.14, -0.03; and β = -0.09, 95%CI: -0.16, -0.03, respectively). The present study provided some evidence that prenatal exposure to bisphenol A and certain phthalates may modify fetal adiponectin and leptin levels.

Effects of arsenic on adipocyte metabolism: Is arsenic an obesogen?

The environmental obesogen model proposes that in addition to a high-calorie diet and diminished physical activity, other factors such as environmental pollutants and chemicals are involved in the development of obesity. Although arsenic has been recognized as a risk factor for Type 2 Diabetes with a specific mechanism, it is still uncertain whether arsenic is also an obesogen. The impairment of white adipose tissue (WAT) metabolism is crucial in the onset of obesity, and distinct studies have evaluated the effects of arsenic on it, however only in some of them for obesity-related purposes. Thus, the known effects of arsenic on WAT/adipocytes were integrated based on the diverse metabolic and physiological processes that occur in WAT and are altered in obesity, specifically: adipocyte growth, adipokine secretion, lipid metabolism, and glucose metabolism. The currently available information suggests that arsenic can negatively affect WAT metabolism, resulting in arsenic being a potential obesogen.

Sex differences in the effects of prenatal lead exposure on birth outcomes

Studies on the associations between prenatal lead exposure and birth outcomes have been inconsistent, and few data are available on the sex differences in these associations. We measured the cord blood lead levels of newborns in Shanghai and determined their associations with birth outcomes, which included birth weight, birth length, head circumference, and the ponderal index, in the total sample and within sex subgroups. A total of 1009 mother-infant pairs were enrolled from 10 hospitals in Shanghai between September 2008 and October 2009. The geometric mean of the cord blood lead concentrations was 4.07 μg/dl (95% CI: 3.98-4.17 μg/dl). A significant inverse association was found between cord blood lead levels and head circumference only in the male subgroup, and increasing cord blood lead levels were related to significant decreases in the ponderal index only in females. The birth weights of the male infants were positively associated with cord blood lead levels; after adjusting for the maternal intake frequency of preserved eggs, the estimated mean differences in birth weights decreased by 11.7% for each 1-unit increase in the log10-transformed cord blood lead concentration. Our findings suggest that prenatal lead exposure may have sex-specific effects on birth outcomes and that maternal dietary intake may be a potential confounder in these relationships. Further studies on this topic are highly warranted.

Identification of chemical mixtures to which Canadian pregnant women are exposed: The MIREC Study

Depending on the chemical and the outcome, prenatal exposures to environmental chemicals can lead to adverse effects on the pregnancy and child development, especially if exposure occurs during early gestation. Instead of focusing on prenatal exposure to individual chemicals, more studies have taken into account that humans are exposed to multiple environmental chemicals on a daily basis. The objectives of this analysis were to identify the pattern of chemical mixtures to which women are exposed and to characterize women with elevated exposures to various mixtures. Statistical techniques were applied to 28 chemicals measured simultaneously in the first trimester and socio-demographic factors of 1744 participants from the Maternal-Infant Research on Environment Chemicals (MIREC) Study. Cluster analysis was implemented to categorize participants based on their socio-demographic characteristics, while principal component analysis (PCA) was used to extract the chemicals with similar patterns and to reduce the dimension of the dataset. Next, hypothesis testing determined if the mean converted concentrations of chemical substances differed significantly among women with different socio-demographic backgrounds as well as among clusters. Cluster analysis identified six main socio-demographic clusters. Eleven components, which explained approximately 70% of the variance in the data, were retained in the PCA. Persistent organic pollutants (PCB118, PCB138, PCB153, PCB180, OXYCHLOR and TRANSNONA) and phthalates (MEOHP, MEHHP and MEHP) dominated the first and second components, respectively, and the first two components explained 25.8% of the source variation. Prenatal exposure to persistent organic pollutants (first component) were positively associated with women who have lower education or higher income, were born in Canada, have BMI ≥25, or were expecting their first child in our study population. MEOHP, MEHHP and MEHP, dominating the second component, were detected in at least 98% of 1744 participants in our cohort study; however, no particular group of pregnant women was identified to be highly exposed to phthalates. While widely recognized as important to studying potential health effects, identifying the mixture of chemicals to which various segments of the population are exposed has been problematic. We present an approach using factor analysis through principal component method and cluster analysis as an attempt to determine the pregnancy exposome. Future studies should focus on how to include these matrices in examining the health effects of prenatal exposure to chemical mixtures in pregnant women and their children.

Arsenic levels among pregnant women and newborns in Canada: Results from the Maternal-Infant Research on Environmental Chemicals (MIREC) cohort

Arsenic is a common environmental contaminant from both naturally-occurring and anthropomorphic sources and human exposure can be detected in various tissues. Its toxicity depends on many factors including the chemical form, valence state, bioavailability, metabolism and detoxification within the human body. Of paramount concern, particularly with respect to health effects in children, is the timing of exposure as the prenatal and early life periods are more susceptible to toxic effects. The Maternal-Infant Research on Environmental Chemicals (MIREC) cohort was established to obtain national-level biomonitoring data for approximately 2,000 pregnant women and their infants between 2008 and 2011 from 10 Canadian cities. We measured total arsenic (As) in 1st and 3rd trimester maternal blood, umbilical cord blood, and infant meconium and speciated arsenic in 1st trimester maternal urine. Most pregnant women had detectable levels of total arsenic in blood (92.5% and 87.3%, respectively, for 1st and 3rd trimester); median difference between 1st and 3rd trimester was 0.1124µg/L (p<0.0001), but paired samples were moderately correlated (Spearman r=0.41, p<0.0001). Most samples were below the LOD for umbilical cord blood (50.9%) and meconium (93.9%). In 1st trimester urine samples, a high percentage (>50%) of arsenic species (arsenous acid (As-III), arsenic acid (As-V), monomethylarsonic acid (MMA), and arsenobetaine (AsB)) were also below the limit of detection, except dimethylarsinic acid (DMA). DMA (>85% detected) ranged from <LOD to 64.42 (95th percentile: 11.99)µgAs/L. There was a weak but significant correlation between total arsenic in blood and specific gravity-adjusted DMA in urine (Spearman r=0.33, p<0.0001). Among this population of pregnant woman and newborns, levels of arsenic measured in blood and urine were lower than national population figures for Canadian women of reproductive age (20-39 years). In general, higher arsenic levels were observed in women who were older, foreign-born (predominantly from Asian countries), and had higher education. Further research is needed to elucidate sources of exposure and factors that may influence arsenic exposure in pregnant women and children.

Environmental influences on reproductive health: the importance of chemical exposures

Chemical exposures during pregnancy can have a profound and life-long impact on human health. Because of the omnipresence of chemicals in our daily life, there is continuous contact with chemicals in food, water, air, and consumer products. Consequently, human biomonitoring studies show that pregnant women around the globe are exposed to a variety of chemicals. In this review we provide a summary of current data on maternal and fetal exposure, as well as health consequences from these exposures. We review several chemical classes, including polychlorinated biphenyls, perfluoroalkyl substances, polybrominated diphenyl ethers, phenols, phthalates, pesticides, and metals. Additionally, we discuss environmental disparities and vulnerable populations, and future research directions. We conclude by providing some recommendations for prevention of chemical exposure and its adverse reproductive health consequences.

Developmental Exposure to Environmental Chemicals and Metabolic Changes in Children

The incidence of childhood obesity, type 2 diabetes, and other forms of metabolic disease have been rising over the past several decades. Although diet and physical activity play important roles in these trends, other environmental factors also may contribute to this significant public health issue. In this article, we discuss the possibility that widespread exposure to endocrine-disrupting chemicals (EDCs) may contribute to the development of metabolic diseases in children. We summarize the epidemiological evidence on exposure to environmental chemicals during early development and metabolic outcomes in infants and children. Prenatal exposure to EDCs, particularly the persistent organic pollutant DDT and its metabolite DDE, may influence growth patterns during infancy and childhood. The altered growth patterns associated with EDCs vary according to exposure level, sex, exposure timing, pubertal status, and age at which growth is measured. Early exposure to air pollutants also is linked to impaired metabolism in infants and children. As a result of these and other studies, professional health provider societies have called for a reduction in environmental chemical exposures. We summarize the resources available to health care providers to counsel patients on how to reduce chemical exposures. We conclude with a discussion of environmental policies that address chemical exposures and ultimately aim to improve public health.

Air Pollution Exposure During Pregnancy and Fetal Markers of Metabolic function: The MIREC Study

Previous evidence suggests that exposure to outdoor air pollution during pregnancy could alter fetal metabolic function, which could increase the risk of obesity in childhood. However, to our knowledge, no epidemiologic study has investigated the association between prenatal exposure to air pollution and indicators of fetal metabolic function. We investigated the association between maternal exposure to nitrogen dioxide and fine particulate matter (aerodynamic diameter ≤2.5 µm) and umbilical cord blood leptin and adiponectin levels with mixed-effects linear regression models among 1,257 mother-infant pairs from the Maternal-Infant Research on Environmental Chemicals (MIREC) Study, conducted in Canada (2008-2011). We observed that an interquartile-range increase in average exposure to fine particulate matter (3.2 µg/m(3)) during pregnancy was associated with an 11% (95% confidence interval: 4, 17) increase in adiponectin levels. We also observed 13% (95% confidence interval: 6, 20) higher adiponectin levels per interquartile-range increase in average exposure to nitrogen dioxide (13.6 parts per billion) during pregnancy. Significant associations were seen between air pollution markers and cord blood leptin levels in models that adjusted for birth weight z score but not in models that did not adjust for birth weight z score. The roles of prenatal exposure to air pollution and fetal metabolic function in the potential development of childhood obesity should be further explored.

Impact of fetal and childhood mercury exposure on immune status in children

BACKGROUND

Mercury exposure have been shown to affect immune status in animals as reflected by cytokine expression. It is unclear whether low levels of exposure during fetal and/or childhood periods could impact on immune status in humans.

OBJECTIVES

To test the hypothesis that fetal and childhood mercury exposure is associated with childhood cytokine profiles and to investigate whether childhood selenium levels interact with any of the associations found.

METHODS

Children were recruited from a previously established birth cohort between the ages of 6-9 years for assessment and measurement of blood mercury, selenium and cytokine profile (interleukin (IL)-4, IL-6, IL-8, IL-10, IL-13 and TNF-alpha). Multivariable linear regression models were used to assess the adjusted association of cord blood mercury concentration and current mercury concentrations with levels of the cytokine levels. We tested whether the association with current mercury level varied by current selenium level and cord blood mercury level.

RESULTS

IL-10 was negatively associated with current blood mercury concentration. The effect was greatest in cases with low cord blood mercury and low current selenium concentrations. None of the other cytokine levels were associated with either cord blood or current blood mercury concentrations, except that cord blood mercury was negatively associated with IL-6.

CONCLUSIONS

Childhood mercury exposure was negatively associated with childhood IL-10 levels. It is postulated that while selenium is protective, low levels of fetal mercury exposure may increase the degree of this negative association during childhood. Further studies into the clinical significance of these findings are required.