A surge in food insecurity during the COVID-19 pandemic in a cohort in Mexico City

BACKGROUND

The COVID-19 pandemic has not only caused tremendous loss of life and health but has also greatly disrupted the world economy. The impact of this disruption has been especially harsh in urban settings of developing countries. We estimated the impact of the pandemic on the occurrence of food insecurity in a cohort of women living in Mexico City, and the socioeconomic characteristics associated with food insecurity severity.

METHODS

We analyzed data longitudinally from 685 women in the Mexico City-based ELEMENT cohort. Food insecurity at the household level was gathered using the Latin American and Caribbean Food Security Scale and measured in-person during 2015 to 2019 before the pandemic and by telephone during 2020-2021, in the midst of the pandemic. Fluctuations in the average of food insecurity as a function of calendar time were modeled using kernel-weighted local polynomial regression. Fixed and random-effects ordinal logistic regression models of food insecurity were fitted, with timing of data collection (pre-pandemic vs. during pandemic) as the main predictor.

RESULTS

Food insecurity (at any level) increased from 41.6% during the pre-pandemic period to 53.8% in the pandemic stage. This increase was higher in the combined severe-moderate food insecurity levels: from 1.6% pre-pandemic to 16.8% during the pandemic. The odds of severe food insecurity were 3.4 times higher during the pandemic relative to pre-pandemic levels (p<0.01). Socioeconomic status quintile (Q) was significantly related to food insecurity (Q2 OR = 0.35 p<0.1, Q3 OR = 0.48 p = 0.014, Q4 OR = 0.24 p<0.01, and Q5 OR = 0.17 p<0.01), as well as lack of access to social security (OR = 1.69, p = 0.01), and schooling (OR = 0.37, p<0.01).

CONCLUSIONS

Food insecurity increased in Mexico City households in the ELEMENT cohort as a result of the COVID-19 pandemic. These results contribute to the body of evidence suggesting that governments should implement well-designed, focalized programs in the context of economic crisis such as the one caused by COVID-19 to prevent families from the expected adverse health and well-being consequences associated to food insecurity, especially for the most vulnerable.

Translational toxicoepigenetic Meta-Analyses identify homologous gene DNA methylation reprogramming following developmental phthalate and lead exposure in mouse and human offspring

Although toxicology uses animal models to represent real-world human health scenarios, a critical translational gap between laboratory-based studies and epidemiology remains. In this study, we aimed to understand the toxicoepigenetic effects on DNA methylation after developmental exposure to two common toxicants, the phthalate di(2-ethylhexyl) phthalate (DEHP) and the metal lead (Pb), using a translational paradigm that selected candidate genes from a mouse study and assessed them in four human birth cohorts. Data from mouse offspring developmentally exposed to DEHP, Pb, or control were used to identify genes with sex-specific sites with differential DNA methylation at postnatal day 21. Associations of human infant DNA methylation in homologous mouse genes with prenatal DEHP or Pb were examined with a meta-analysis. Differential methylation was observed on 6 cytosines (adjusted-p < 0.05) and 90 regions (adjusted-p < 0.001). This translational approach offers a unique method that can detect conserved epigenetic differences that are developmentally susceptible to environmental toxicants.

Prenatal exposure to metal mixtures and childhood temporal processing in the PROGRESS Birth Cohort Study: Modification by childhood obesity

Children are frequently exposed to various biological trace metals, some essential for their development, while others can be potent neurotoxicants. Furthermore, the inflammatory and metabolic conditions associated with obesity may interact with and amplify the impact of metal exposure on neurodevelopment. However, few studies have assessed the potential modification effect of body mass index (BMI). As a result, we investigated the role of child BMI phenotype on the relationship between prenatal exposure to metal mixtures and temporal processing. Leveraging the PROGRESS birth cohort in Mexico City, children (N = 563) aged 6-9 years completed a Temporal Response Differentiation (TRD) task where they had to hold a lever down for 10-14 s. Blood and urinary metal (As, Pb, Cd, and Mn) measurements were collected from mothers in the 2nd and 3rd trimesters. Child BMI z-scores were dichotomized to normal (between -2 and +0.99) and high (≥1.00). Covariate-adjusted weighted quantile sum (WQS) regression models were used to estimate and examine the combined effect of metal biomarkers (i.e., blood and urine) on TRD measures. Effect modification by the child's BMI was evaluated using 2-way interaction terms. Children with a high BMI and greater exposure to the metal mixture during prenatal development exhibited significant temporal processing deficits compared to children with a normal BMI. Notably, children with increased exposure to the metal mixture and higher BMI had a decrease in the percent of tasks completed (β = -10.13; 95 % CI: -19.84, -0.42), number of average holds (β = -2.15; 95 % CI: -3.88, -0.41), longer latency (β = 0.78; 95 % CI: 0.13, 1.44), and greater variability in the standard deviation of the total hold time (β = 2.08; 95 % CI: 0.34, 3.82) compared to normal BMI children. These findings implicate that high BMI may amplify the effect of metals on children's temporal processing. Understanding the relationship between metal exposures, temporal processing, and childhood obesity can provide valuable insights for developing targeted environmental interventions.

Prenatal metal exposures and childhood gut microbial signatures are associated with depression score in late childhood

BACKGROUND

Childhood depression is a major public health issue worldwide. Previous studies have linked both prenatal metal exposures and the gut microbiome to depression in children. However, few, if any, have studied their interacting effect in specific subgroups of children.

OBJECTIVES

Using an interpretable machine-learning method, this study investigates whether children with specific combinations of prenatal metals and childhood microbial signatures (cliques or groups of metals and microbes) were more likely to have higher depression scores at 9-11 years of age.

METHODS

We leveraged data from a well-characterized pediatric longitudinal birth cohort in Mexico City and its microbiome substudy (n = 112). Eleven metal exposures were measured in maternal whole blood samples in the second and third trimesters of pregnancy. The gut microbial abundances were measured at 9-11-year-olds using shotgun metagenomic sequencing. Depression symptoms were assessed using the Child Depression Index (CDI) t-scores at 9-11 years of age. We used Microbial and Chemical Exposure Analysis (MiCxA), which combines interpretable machine-learning into a regression framework to identify and estimate joint associations of metal-microbial cliques in specific subgroups. Analyses were adjusted for relevant covariates.

RESULTS

We identified a subgroup of children (11.6 % of the sample) characterized by a four-component metal-microbial clique that had a significantly high depression score (15.4 % higher than the rest) in late childhood. This metal-microbial clique consisted of high Zinc in the second trimester, low Cobalt in the third trimester, a high abundance of Bacteroides fragilis, a high abundance of Faecalibacterium prausnitzii. All combinations of cliques (two-, three-, and four-components) were significantly associated with increased log-transformed t-scored CDI (β = 0.14, 95%CI = [0.05,0.23], P < 0.01 for the four-component clique).

SIGNIFICANCE

This study offers a new approach to chemical-microbial analysis and a novel demonstration that children with specific gut microbiome cliques and metal exposures during pregnancy may have a higher likelihood of elevated depression scores.

Prenatal and childhood lead exposure is prospectively associated with biological markers of aging in adolescence

Few studies have related early life lead exposure to adolescent biological aging, a period characterized by marked increases in maturational tempo. We examined associations between prenatal and childhood lead exposure and adolescent biological age (mean 14.5 years) utilizing multiple epigenetic clocks including: intrinsic (IEAA), extrinsic (EEAA), Horvath, Hannum, PhenoAge, GrimAge, Skin-Blood, Wu, PedBE, as well as DNA methylation derived telomere length (DNAmTL). Epigenetic clocks and DNAmTL were calculated via adolescent blood DNA methylation measured by Infinium MethylationEPIC BeadChips. We constructed general linear models (GLMs) with individual lead measures predicting biological age. We additionally examined sex-stratified models and lead by sex interactions, adjusting for adolescent age and lead levels, maternal smoking and education, and proportion of cell types. We also estimated effects of lead exposure on biological age using generalized estimating equations (GEE). First trimester blood lead was positively associated with a 0.14 increase in EEAA age in the GLMs though not the GEE models (95%CI 0.03, 0.25). First and 2nd trimester blood lead levels were associated with a 0.02 year increase in PedBE age in GLM and GEE models (1st trimester, 95%CI 0.004, 0.03; 2nd trimester, 95%CI 0.01, 0.03). Third trimester and 24 month blood lead levels were associated with a -0.06 and -0.05 decrease in Skin-Blood age, respectively, in GLM models. Additionally, 3rd trimester blood lead levels were associated with a 0.08 year decrease in Hannum age in GLM and GEE models (95%CI -0.15, -0.01). There were multiple significant results in sex-stratified models and significant lead by sex interactions, where males experienced accelerated biological age, compared to females who saw a decelerated biological age, with respect to IEAA, EEAA, Horvath, Hannum, and PedBE clocks. Further research is needed to understand sex-specific relationships between lead exposure and measures of biological aging in adolescence and the trajectory of biological aging into young adulthood.

Sensitive development windows of prenatal air pollution and cognitive functioning in preschool age Mexican children

Introduction

Neurotoxicity resulting from air pollution is of increasing concern. Considering exposure timing effects on neurodevelopmental impairments may be as important as the exposure dose. We used distributed lag regression to determine the sensitive windows of prenatal exposure to fine particulate matter (PM2.5) on children's cognition in a birth cohort in Mexico.

Methods

Analysis included 553 full-term (≥37 weeks gestation) children. Prenatal daily PM2.5 exposure was estimated using a validated satellite-based spatiotemporal model. McCarthy Scales of Children's Abilities (MSCA) were used to assess children's cognitive function at 4-5 years old (lower scores indicate poorer performance). To identify susceptibility windows, we used Bayesian distributed lag interaction models to examine associations between prenatal PM2.5 levels and MSCA. This allowed us to estimate vulnerable windows while testing for effect modification.

Results

After adjusting for maternal age, socioeconomic status, child age, and sex, Bayesian distributed lag interaction models showed significant associations between increased PM2.5 levels and decreased general cognitive index scores at 31-35 gestation weeks, decreased quantitative scale scores at 30-36 weeks, decreased motor scale scores at 30-36 weeks, and decreased verbal scale scores at 37-38 weeks. Estimated cumulative effects (CE) of PM2.5 across pregnancy showed significant associations with general cognitive index (C E ^ = -0.35, 95% confidence interval [CI] = -0.68, -0.01), quantitative scale (C E ^ = -0.27, 95% CI = -0.74, -0.02), motor scale (C E ^ = -0.25, 95% CI = -0.44, -0.05), and verbal scale (C E ^ = -0.2, 95% CI = -0.43, -0.02). No significant sex interactions were observed.

Conclusions

Prenatal exposure to PM2.5, particularly late pregnancy, was inversely associated with subscales of MSCA. Using data-driven methods to identify sensitive window may provide insight into the mechanisms of neurodevelopmental impairment due to pollution.

Breastfeeding Duration and Cardiometabolic Health during Adolescence: A Longitudinal Analysis

OBJECTIVE

To investigate the longitudinal association between breastfeeding duration and cardiometabolic health, using repeated measures study design among children and adolescents.

STUDY DESIGN

This study included 634 offsprings aged 10 to 21 years (52% female) from the Early Life Exposure in Mexico to Environmental Toxicants birth cohort followed up to four time points during adolescence. Breastfeeding duration was prospectively quantified using questionnaires during early childhood. Cardiometabolic risk factors, body composition, and weight-related biomarkers were assessed as outcomes during adolescent follow-up visits. Sex-stratified linear mixed-effects models were used to model the association between quartiles of breastfeeding duration and outcomes, adjusting for age and additional covariates.

RESULTS

Median breastfeeding duration was 7 months (minimum = 0, maximum = 36). Boys in the second quartile (median breastfeeding = 5 months) had lower total fat mass % (β (SE) -3.2 (1.5) P = .037), and higher lean mass % (3.1 (1.6) P = .049) and skeletal muscle mass % (1.8 (0.8) P = .031) compared with the reference group (median breastfeeding = 2 months). A positive linear trend between breastfeeding duration and trunk lean mass % (0.1 (0.04) P = .035) was found among girls. No association was found with other cardiometabolic indicators.

CONCLUSION

Despite sex-specific associations of breastfeeding duration with body composition, there was a lack of substantial evidence for the protective effects of breastfeeding against impaired cardiometabolic health during adolescence among Mexican youth. Further longitudinal studies with a robust assessment of breastfeeding are recommended.

Recent ambient temperature and fine particulate matter (PM2.5) exposure is associated with urinary kidney injury biomarkers in children

BACKGROUND

Limited research has examined associations between exposure to ambient temperature, air pollution, and kidney function or injury during the preadolescent period. We examined associations between exposure to ambient temperature and particulate matter with aerodynamic diameter ≤ 2.5 μm (PM2.5) with preadolescent estimated glomerular filtration rate (eGFR) and urinary kidney injury biomarkers.

METHODS

Participants included 437 children without cardiovascular or kidney disease enrolled in the Programming Research in Obesity, Growth, Environment and Social Stressors birth cohort study in Mexico City. eGFR and urinary kidney injury biomarkers were assessed at 8-12 years. Validated satellite-based spatio-temporal models were used to estimate mean daily temperature and PM2.5 levels at each participant's residence 7- and 30-days prior to the date of visit. Linear regression and distributed lag nonlinear models (DLNM) were used to examine associations between daily mean temperature and PM2.5 exposure and kidney outcomes, adjusted for covariates.

RESULTS

In single linear regressions, higher seven-day average PM2.5 was associated with higher urinary alpha-1-microglobulin and eGFR. In DLNM analyses, higher temperature exposure in the seven days prior to date of visit was associated with a decrease in urinary cystatin C of -0.56 ng/mL (95 % confidence interval (CI): -1.08, -0.04) and in osteopontin of -0.08 ng/mL (95 % CI: -0.15, -0.001). PM2.5 exposure over the seven days prior to date of visit was associated with an increase in eGFR of 1.77 mL/min/1.73m2 (95 % CI: 0.55, 2.99) and urinary cystatin C of 0.19 ng/mL (95 % CI: 0.03, 0.35).

CONCLUSIONS

Recent exposure to ambient temperature and PM2.5 were associated with increased and decreased urinary kidney injury biomarkers that may reflect subclinical glomerular or tubular injury in children. Further research is required to assess environmental exposures and worsening subclinical kidney injury across development.

Cross-sectional associations between phthalates, phenols, and parabens with metabolic syndrome risk during early-to-mid adolescence among a cohort of Mexican youth

BACKGROUND

Epidemiological studies on children and adults have linked toxicants from plastics and personal care products to metabolic disruption. Yet, the impact of endocrine-disrupting chemicals (EDCs) on adolescent metabolic syndrome (MetS) risk during early and mid-adolescence is unclear.

METHODS

To examine the links between exposure to EDCs and MetS risk and its components, cross-sectional data from 344 Mexican youth in early-to-mid adolescence (10-17 years) were analyzed. Urinary biomarker concentrations of phthalates, phenol, and paraben analytes were measured from a single spot urine sample collected in 2015; study personnel obtained anthropometric and metabolic measures. We examined associations between summary phthalates and metabolites, phenol, and paraben analytes with MetS risk z-scores using linear regression, adjusted for specific gravity, sex, age, pubertal status, smoking, alcohol intake, physical activity level, and screen time. As a secondary aim, mediation analysis was conducted to evaluate the role of hormones in the association between summary phthalates with lipids and MetS risk z-scores.

RESULTS

The mean (SD) age was 13.2 (1.9) years, and 50.9% were female. Sex-stratified analyses revealed associations between summary phthalates and lipids ratio z-scores, including Σ DEHP [β = 0.21 (95% CI: 0.04, 0.37; p < 0.01)], phthalates from plastic sources (Σ Plastic) [β = 0.22 (95% CI: 0.05, 0.39; p < 0.01)], anti-androgenic phthalates (Σ AA) [β = 0.22 (95% CI: 0.05, 0.39; p < 0.01)], and individual phthalate metabolites (MEHHP, MEOHP, and MECPP) among males. Among females, BPA [β = 0.24 (95% CI: 0.03, 0.44; p < 0.05)] was positively associated with lipids ratio z-score and one phenol (2,5 DCP) [β = 0.09 (95% CI: 0.01, 0.18); p < 0.05)] was associated with increased waist circumference z-score. Results showed no evidence of mediation by hormone concentrations in the association between summary phthalates with lipids ratio or MetS risk z-scores.

CONCLUSION

Higher EDC exposure was positively associated with serum lipids during adolescence, particularly among males.

Prenatal manganese biomarkers and operant test battery performance in Mexican children: Effect modification by child sex

BACKGROUND

Manganese (Mn) is essential to healthy neurodevelopment, but both Mn deficiency and over-exposure have been linked to prefrontal cortex (PFC) impairments, the brain region that regulates cognitive and neurobehavioral processes responsible for spatial memory, learning, motivation, and time perception. These processes facilitated by attention, inhibitory control, working memory, and cognitive flexibility are often sexually dimorphic and complex, driven by multiple interconnected neurologic and cognitive domains.

OBJECTIVE

We investigated the role of child sex as an effect modifier of the association between prenatal Mn exposure and performance in an operant testing battery (OTB) that assessed multiple cognitive and behavioral functional domains.

METHODS

Children (N = 575) aged 6-8 years completed five OTB tasks. Blood and urinary Mn measurements were collected from mothers in the 2nd and 3rd trimesters. Multiple regression models estimated the association between Mn biomarkers at each trimester with OTB performance while adjusting for socio-demographic covariates. Covariate-adjusted weighted quantile sum (WQS) regression models were used to estimate the association of a Mn multi-media biomarker (MMB) mixture with OTB performance. Interaction terms were used to estimate modification effect by child sex.

RESULTS

Higher blood Mn exposure was associated with better response rates (more motivation) on the progressive ratio task and higher overall accuracy on the delayed matching-to-sample task. In the WQS models, the MMB mixture was associated with better response rates (more motivation) on the progressive ratio task. Additionally, for the linear and WQS models, we observed a modification effect by child sex in the progressive ratio and delayed matching-to-sample tasks. Higher prenatal Mn biomarker levels were associated with improved task performance for girls and reduced performance in boys.

CONCLUSION

Higher prenatal blood Mn concentrations and the MMB mixture predicted improved performance on two of five operant tasks. Higher prenatal Mn concentrations regulated executive functions in children in a sexually dimorphic manner. Higher prenatal Mn exposure is associated with improved performance on spatial memory and motivation tasks in girls, suggesting that Mn's nutritional role is sexually dimorphic, and should be considered when making dietary and/or environmental intervention recommendations.

Associations of prenatal and childhood Pb exposure with allostatic load in adolescence: Findings from the ELEMENT cohort study

The biological pathways which link lead (Pb) and long-term outcomes are unclear, though rodent models and a few human studies suggest Pb may alter the body's stress response systems, which over time, can elicit dysregulated stress responses with cumulative impacts. This study examined associations between prenatal and early childhood Pb exposure and adolescent allostatic load, an index of an individual's body burden of stress in multiple biological systems, and further examined sex-based associations. Among 391 (51% male) participants in the ELEMENT birth cohort, we related trimester-specific maternal blood Pb, 1-month postpartum maternal tibia and patella Pb, and child blood Pb at 12-24 months to an allostatic load index in adolescence comprised of biomarkers of cardiovascular, metabolic, neuroendocrine, and immune function. The results were overall mixed, with prenatal exposure, particularly maternal bone Pb, being positively associated with allostatic load, and early childhood Pb showing mixed results for males and females. In adjusted Poisson regression models, 1 mcg/g increase in tibia Pb was associated with a 1% change in expected allostatic load (IRR = 1.01; 95%CI 0.99, 1.02). We found a significant Pb × sex interaction (IRR = 1.05; 95%CI 1.01, 1.10); where males saw an increasing percent change in allostatic load as 12 month Pb levels increased compared to females who saw a decreasing allostatic load. Further examination of allostatic load will facilitate the determination of potential mechanistic pathways between developmental toxicant exposures and later-in-life cardiometabolic outcomes.

Associations between blood leukocyte DNA methylation and sustained attention in mid-to-late childhood

Aims: To identify associations between DNA methylation (DNAm) across the epigenome and symptoms related to attention-deficit/hyperactivity disorder in a population of Hispanic children. Materials & methods: Among 517 participants in the ELEMENT study aged 9-18 years, we conducted an epigenome-wide association study examining associations between blood leukocyte DNAm and performance on the Conners' continuous performance test (CPT3). Results: DNAm at loci in or near ZNF814, ELF4 and OR6K6 and functional enrichment for gene pathways pertaining to ferroptosis, inflammation, immune response and neurotransmission were significantly related to CPT3 scores. Conclusion: DNAm was associated with CPT3 performance. Further analysis is warranted to understand how these genes and enriched pathways contribute to attention-deficit/hyperactivity disorder.

Sex-specific association between prenatal manganese exposure and working memory in school-aged children in Mexico city: An exploratory multi-media approach

It remains unclear whether manganese (Mn) exposure affects working memory (WM) in a sexually dimorphic manner. Further, no gold standard media exists to measure Mn, suggesting a combined blood and urinary Mn index may better capture the totality of exposure. We investigated the modification effect of child sex on the influence of prenatal Mn exposure on WM in school-age children, exploring two methodological frameworks to integrate exposure estimates across multiple exposure biomarkers. Leveraging the PROGRESS birth cohort in Mexico City, children (N = 559) ages 6-8 completed the between errors and strategy measures of the CANTAB Spatial Working Memory (SWM) task. Mn levels were assayed in blood and urine of mothers during the 2nd and 3rd trimesters and in umbilical cord blood from mothers and children at delivery. Weighted quantile sum regression estimated the association of a multi-media biomarker (MMB) mixture with SWM. We applied a confirmatory factor analysis to similarly quantify a latent blood Mn burden index. We then used an adjusted linear regression to estimate the Mn burden index with SWM measures. Interaction terms were used to estimate the modification effect by child sex for all models. Results showed that the between-errors-specific MMB mixture (i.e., this model demonstrates the impact of the MMB mixture on the between-error scores.) was associated (β = 6.50, 95% CI: 0.91, 12.08) with fewer between errors for boys and more between errors for girls. The strategy-specific MMB mixture (i.e., this model demonstrates the impact of the MMB mixture on the strategy scores) was associated (β = -1.36, 95% CI: 2.55, - 0.18) with less efficient strategy performance for boys and more efficient strategy performance for girls. A higher Mn burden index was associated (β = 0.86, 95% CI: 0.00, 1.72) with more between errors in the overall sample. The vulnerability to prenatal Mn biomarkers on SWM differs in the directionality by child sex. An MMB mixture and composite index of body burden are stronger predictors than a single biomarker for Mn exposure on WM performance.

Prenatal dietary patterns in relation to adolescent offspring adiposity and adipokines in a Mexico City cohort

Maternal diet during pregnancy has been associated with obesity among offspring. The extent to which trimester-specific dietary patterns are associated with markers of adiposity during adolescence remains unclear. We examined associations between prenatal diet patterns with adolescent offspring measures of adiposity and adipokines in 384 mother-adolescent dyads from the Mexico City ELEMENT cohort. Trimester-specific diet patterns were derived from principal component analysis of food frequency questionnaire data. Adolescent anthropometry and serum leptin and adiponectin were measured at 10-17 years. Three maternal diet patterns were identified: Prudent Diet (PD), high in fish and vegetables, the High Meat and Fat Diet (HMFD), high in pork and processed meats, and the Transitioning Mexican Diet (TMD), high in corn tortillas and sugar-sweetened beverages. Multiple linear regression was used to estimate sex-stratified associations among quartiles of diet patterns with adiposity and adipokines, adjusting for maternal marital status, education, and parity. First trimester TMD was associated with greater anthropometric measures and higher leptin in females, while third trimester HMFD was associated higher body fat percentage, triceps thickness, waist circumference, and leptin, but lower adiponectin among males. Contrary to expectation, there were positive associations between the trimester 1 PD pattern and anthropometric measurements in females, and for trimester 2 HMFD and TMD patterns with adipokines among males. Findings suggest maternal diet patterns may influence offspring adiposity markers during adolescence in a sex-specific manner.

Prenatal Pb exposure is associated with reduced abundance of beneficial gut microbial cliques in late childhood: an investigation using Microbial Co-occurrence Analysis (MiCA)

Background

Many analytical methods used in gut microbiome research focus on either single bacterial taxa or the whole microbiome, ignoring multi-bacteria relationships (microbial cliques). We present a novel analytical approach to identify multiple bacterial taxa within the gut microbiome of children at 9-11 years associated with prenatal Pb exposure.

Methods

Data came from a subset of participants (n=123) in the Programming Research in Obesity, Growth, Environment and Social Stressors (PROGRESS) cohort. Pb concentrations were measured in maternal whole blood from the second and third trimesters of pregnancy. Stool samples collected at 9-11 years old underwent metagenomic sequencing to assess the gut microbiome. Using a novel analytical approach, Microbial Co-occurrence Analysis (MiCA), we paired a machine-learning algorithm with randomization-based inference to first identify microbial cliques that were predictive of prenatal Pb exposure and then estimate the association between prenatal Pb exposure and microbial clique abundance.

Results

With second-trimester Pb exposure, we identified a 2-taxa microbial clique that included Bifidobacterium adolescentis and Ruminococcus callidus, and a 3-taxa clique that added Prevotella clara. Increasing second-trimester Pb exposure was associated with significantly increased odds of having the 2-taxa microbial clique below the 50th percentile relative abundance (OR=1.03,95%CI[1.01-1.05]). In an analysis of Pb concentration at or above vs. below the United States and Mexico guidelines for child Pb exposure, odds of the 2-taxa clique in low abundance were 3.36(95%CI[1.32-8.51]) and 6.11(95%CI[1.87-19.93]), respectively. Trends were similar with the 3-taxa clique but not statistically significant.

Discussion

Using a novel combination of machine-learning and causal-inference, MiCA identified a significant association between second-trimester Pb exposure and reduced abundance of a probiotic microbial clique within the gut microbiome in late childhood. Pb exposure levels at the guidelines for child Pb poisoning in the United States, and Mexico are not sufficient to protect against the potential loss of probiotic benefits.

Associations between exposure to phthalates, phenols, and parabens with objective and subjective measures of sleep health among Mexican women in midlife: a cross-sectional and retrospective analysis

Endocrine-disrupting chemicals (EDCs) may impact sleep during the menopausal transition by altering sex hormones. However, these studies are scarce among Latin American women. This investigation utilized cross-sectional and retrospective data from midlife women enrolled in the Early Life Exposure in Mexico to Environmental Toxicants (ELEMENT) study to examine associations between exposure to EDCs (phthalates, phenols, and parabens) and sleep health measures. For cross-sectional analyses, single spot urine samples were collected between 2017-2019 from a pilot sample of women (N = 91) of midlife age to estimate the urinary concentration of individual phthalates, phenols, and parabens and to calculate the summary concentration of phthalate mixtures. Seven-day nightly sleep duration, midpoint, and fragmentation were obtained from wrist-actigraphy devices and estimated from the actigraphy data using a pruned dynamic programming algorithm. Self-reported poor sleep quality was assessed by one item from the Pittsburgh Sleep Quality Index (PSQI). We examined associations between urinary summary phthalate mixtures, phthalate metabolites, phenol, and paraben analytes with each sleep measure using linear or logistic (to compute odds of poor sleep quality only) regression models adjusted for specific gravity, age, and socioeconomic status. We ran similar regression models for retrospective analyses (N = 74), except that urine exposure biomarker data were collected in 2008 when women were 24-50 years old. At the 2017-2019 midlife visit, 38% reported poor sleep quality. Cross-sectionally, EDCs were associated with longer sleep duration, earlier sleep timing, and more fragmented sleep. For example, every 1-unit IQR increase in the phenol triclosan was associated with a 26.3 min per night (95% CI: 10.5, 42.2; P < 0.05) longer sleep duration and marginally associated with 0.2 decimal hours (95% CI: -0.4, 0.0; P < 0.10) earlier sleep midpoint; while every 1-unit IQR increase in the phthalate metabolite MEHP was associated with 1.1% higher sleep fragmentation (95% CI: 0.1, 2.1; P < 0.05). Retrospective study results generally mirrored cross-sectional results such that EDCs were linked to longer sleep duration, earlier sleep timing, and more fragmented sleep. EDCs were not significantly associated with odds of self-reported poor sleep quality. Results from cross-sectional and retrospective analyses revealed that higher exposure to EDCs was predictive of longer sleep duration, earlier sleep timing, and more fragmented sleep among midlife women.

Is adiposity related to repeat measures of blood leukocyte DNA methylation across childhood and adolescence?

Epigenetic modifications such as DNA methylation may influence gene expression and phenotypes, including obesity in childhood. The directionality of this relationship is nevertheless unclear, and some evidence suggests that adiposity modifies the epigenome, rather than the other way around. In this pilot study, we utilize data from the Early Life Exposures in Mexico to Environmental Toxicants (ELEMENT) study to examine whether measures of adiposity in childhood and early adolescence are associated with repeated measures of blood leukocyte DNA methylation at LINE-1 repetitive elements and two genes implicated in growth and adiposity: H19 and HSD11B2. Longitudinal epigenetic data were generated from cord blood and blood from follow-up visits in early and late adolescence. We assessed interactions between age and measures of body mass index (BMI) at 5 years of age and weight, BMI and waist circumference in early adolescence to infer whether adiposity deflects age-related DNA methylation changes throughout childhood. Applying linear mixed-effects models, we found an inverse association between measures of childhood BMI (kg/m2 ) and early-teen weight (kg) with repeat measures of H19 DNA methylation. We did not observe any statistically significant associations (p-value <.05) between any anthropometric measures and DNA methylation at LINE-1 or HSD11B2. We did not demonstrate statistically significant evidence in support of deflection of age-related DNA methylation trajectories by adiposity-related measures (age by adiposity interaction term). Given the pilot nature of this study, the relationships between repeat measures of DNA methylation and adiposity-measures across childhood merit further exploration in larger study populations.

Urinary phthalates, phenols, and parabens in relation to sleep health markers among a cohort of Mexican adolescents

INTRODUCTION

Emerging research has shed light on the potential impact of environmental toxicants on sleep health, however, it remains unclear if these associations exist during adolescence and whether associations differ by sex. This study aimed to examine associations between phthalates, parabens, and phenols on adolescent sleep health using cross-sectional data from 470 participants from the Early Life Exposures in Mexico to Environmental Toxicants (ELEMENT) study.

MATERIAL AND METHODS

In 2015, spot urine samples were analyzed for exposure biomarkers of 14 phthalate metabolites, seven phenol, and four paraben analytes. Over seven consecutive days, sleep duration, midpoint, and fragmentation were assessed with wrist-actigraphy. We examined associations between summary phthalates, individual phthalate metabolites, and phenol and paraben analytes with mean weekday sleep duration, midpoint, and fragmentation using linear regression models adjusted for specific-gravity and sex, age, pubertal status, smoking and alcohol behavior, physical activity, and screen time.

RESULTS

Mean (SD) age was 13.8 (2.1) years; 53.5 % were female. Σ Plastic - summary measure for toxicants from plastic sources - and Σ DEHP and its metabolites, were associated with longer sleep duration in the unstratified sample. To illustrate, every 1-unit log increase in Σ DEHP was associated with 7.7 min (95 % CI: 0.32, 15.1; p < 0.05) longer duration. Summary measures of toxicants from plastic sources, personal care products, anti-androgenic toxicants, and multiple individual phthalates, phenols, and parabens were associated with later midpoint. The midpoint associations were largely female-specific. There were no associations with sleep fragmentation.

CONCLUSIONS

Higher EDC exposure may be related to longer sleep duration and later sleep timing during adolescence, and associations may vary by toxicant and according to sex.

DNA Methylation Is a Potential Biomarker for Cardiometabolic Health in Mexican Children and Adolescents

DNA methylation (DNAm) is a plausible mechanism underlying cardiometabolic abnormalities, but evidence is limited among youth. This analysis included 410 offspring of the Early Life Exposure in Mexico to Environmental Toxicants (ELEMENT) birth cohort followed up to two time points in late childhood/adolescence. At Time 1, DNAm was quantified in blood leukocytes at long interspersed nuclear elements (LINE-1), H19, and 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD-2), and at Time 2 in peroxisome proliferator-activated receptor alpha (PPAR-α). At each time point, cardiometabolic risk factors were assessed including lipid profiles, glucose, blood pressure, and anthropometry. Linear mixed effects models were used for LINE-1, H19, and 11β-HSD-2 to account for the repeated-measure outcomes. Linear regression models were conducted for the cross-sectional association between PPAR-α with the outcomes. DNAm at LINE-1 was associated with log glucose at site 1 [β = -0.029, p = 0.0006] and with log high-density lipoprotein cholesterol at site 3 [β = 0.063, p = 0.0072]. 11β-HSD-2 DNAm at site 4 was associated with log glucose (β = -0.018, p = 0.0018). DNAm at LINE-1 and 11β-HSD-2 was associated with few cardiometabolic risk factors among youth in a locus-specific manner. These findings underscore the potential for epigenetic biomarkers to increase our understanding of cardiometabolic risk earlier in life.

Analysis of the burden of disease attributable to environmental risk factors in Mexico in the 1990-2021 period. Identification of advances, lags and emergencies

BACKGROUND

It is estimated that environmental risk factors (ERF) were responsible for nine million deaths worldwide in 2019.

OBJECTIVE

Using data from the Global Burden of Disease study, indicators of health loss associated with exposure to ERF in Mexico were analyzed.

MATERIAL AND METHODS

Absolute numbers and population percentages of deaths and disability-adjusted life years (DALY) lost attributed to selected ERFs were analyzed at the national and state level and by sex, as well as age-standardized trends from 1990 to 2021.

RESULTS

In 2021, ambient particulate matter pollution showed the highest mortality and DALYs lost attributed to selected ERFs (42.2 and 38.1% respectively), followed by lead exposure (20.6 and 13.4%) and low temperature (19.8 and 12.3%). Both indicators have decreased for all selected ERAs by different magnitudes between 1991 and 2021, except for high temperature.

CONCLUSIONS

Despite decreases in the last 32 years, outdoor environment particulate matter showed the highest mortality and DALYs lost, followed by lead exposure. It is essential to strengthen air quality and lead exposure policies in Mexico.

Prenatal exposure to metals and concentration thereof in umbilical cord blood in a Mexico City cohort

BACKGROUND

In Mexico, there is a paucity of evidence on the magnitude of prenatal exposure to metals.

OBJECTIVE

To estimate the concentration of arsenic, cadmium, manganese and lead in umbilical cord blood (UCB) and its association with maternal blood concentrations during pregnancy and delivery.

MATERIAL AND METHODS

Metal concentration in maternal blood was analyzed during pregnancy (n = 901), delivery (n = 732) and in UCB (n = 512) from participants of the PROGRESS cohort residing in Mexico City. The association between concentrations in UCB and maternal biomarkers was analyzed using generalized linear models, adjusted for relevant covariates.

RESULTS

Mean concentrations (μg/L) of lead, arsenic and manganese in UCB were 27.14 (25.28-29.14), 0.77 (0.71-0.84) and 42.60 (40.45-44.83), respectively. Cadmium concentration could not be estimated because 86.2% of measurements were below the detection limit. Lead and manganese concentrations in UCB were significantly associated with maternal biomarkers during pregnancy and delivery; at delivery, association was only observed with arsenic.

CONCLUSIONS

Prenatal exposure to toxic metals in sensitive periods of organogenesis shows a neglected public health problem. Biomonitoring of the population and establishment of regulations aimed at providing care to vulnerable populations is required.

Prenatal Metal Exposures and Associations with Kidney Injury Biomarkers in Children

Prenatal exposure to arsenic (As), cadmium (Cd), mercury (Hg), and lead (Pb) may be nephrotoxic, yet limited studies have examined subclinical kidney injury biomarkers in children. We assessed whether metal exposure in the second trimester (2T), a crucial time of kidney development, is associated with altered urine kidney injury and function biomarkers in preadolescent children. Analyses included 494 children participating in a birth cohort study in Mexico City. Concentrations of As, Cd, and Pb were measured from pregnant women in 2T blood and urine, and Hg in urine only. Kidney biomarkers were measured from children in urine at age 8-12 years. We assessed the associations between individual metals and (1) kidney biomarkers using linear regression and (2) a multi-protein kidney mixture using weighted quantile sum (WQS) regression. Associations of separate urine and blood metal mixtures with individual kidney biomarkers were assessed via WQS. Within the multi-protein mixture, the association with increased urinary As was predominated by urine alpha-1-microglobulin (A1M), interferon gamma-induced protein 10 (IP10), and fatty acid binding protein 1; the association with increased urinary Cd was predominated by A1M, clusterin, and albumin. The urine metal mixture was associated with increased albumin (0.23 ng/mL; 95% confidence interval (CI): 0.10, 0.37), IP10 (0.15 ng/mL; 95% CI: 0.02, 0.28), and cystatin C (0.17 ng/mL; 95% CI: 0.04, 0.31); these associations were mainly driven by urinary As and Cd. We observed null associations between prenatal blood or urine metal mixtures and estimated glomerular filtration rate. Higher prenatal urinary metals, individually and as a mixture were associated with altered kidney injury biomarkers in children. Further research and longer participant follow-up are required to ascertain the risk of kidney disease later in life.

Trimester-specific phthalate exposures in pregnancy are associated with circulating metabolites in children

Background

Prenatal phthalates exposures have been related to adiposity in peripuberty in a sex-specific fashion. Untargeted metabolomics analysis to assess circulating metabolites offers the potential to characterize biochemical pathways by which early life exposures influence the development of cardiometabolic risk during childhood and adolescence, prior to becoming evident in clinical markers.

Methods

Among mother-child dyads from the Early Life Exposure in Mexico to ENvironmental Toxicants (ELEMENT) birth cohort, we measured 9 phthalate metabolites and bisphenol A in maternal spot urine samples obtained during each trimester of pregnancy, corrected for urinary specific gravity and natural log-transformed. In 110 boys and 124 girls aged 8–14 years, we used a mass-spectrometry based untargeted metabolomics platform to measure fasting serum metabolites, yielding 572 annotated metabolites. We estimated the associations between trimester-specific urinary toxicants and each serum metabolite, among all children or stratified by sex and adjusting for child age, BMI z-score, and pubertal onset. We accounted for multiple comparisons using a 10% false discovery rate (q<0.1).

Results

Associations between exposures and metabolites were observed among all children and in sex-stratified analyses (q<0.1). First trimester MEP, MiBP, and MCPP were associated with decreased 2-deoxy-D-glucose among all children. Among girls, third trimester concentrations of MECPP, MEHHP, MEHP, and MCPP were associated with 15, 13, 1, and 10 metabolites, respectively, including decreased choline and increased acylcarnitines and saturated FAs (FA). Among boys, third trimester MIBP was positively associated with 9 features including long chain saturated FAs, and second trimester MBzP was inversely associated with thyroxine.

Conclusions

Metabolomics biomarkers may reflect sex- and exposure timing-specific responses to prenatal phthalate exposures manifesting in childhood that may not be detected using standard clinical markers of cardiometabolic risk.

Prenatal and early childhood critical windows for the association of nephrotoxic metal and metalloid mixtures with kidney function

INTRODUCTION

As renal development and maturation processes begin in utero and continue through early childhood, sensitive developmental periods arise during which metal exposures can program subclinical nephrotoxicity that manifests later in life. We used novel dentine biomarkers of established nephrotoxicants including arsenic (As), cadmium (Cd), lead (Pb), chromium (Cr), and lithium (Li), and their mixtures, to identify critical windows of exposure-associated kidney function alterations in preadolescents.

METHODS

Participants included 353 children in the Programming Research in Obesity Growth, Environment and Social Stressors (PROGRESS) longitudinal birth cohort study based in Mexico City. Estimated glomerular filtration rate (eGFR) was assessed in 8-12 year old children using serum cystatin C measures. Pre- and postnatal metal(loid) concentrations were assessed in weekly increments by analyzing deciduous teeth with laser ablation-inductively coupled plasma-mass spectrometry. We used reverse distributed lag models (rDLMs) and lagged Weighted Quantile Sum (L-WQS) regression to examine time-varying associations between weekly perinatal metal(loid) exposure or metal(loid) mixtures and preadolescent eGFR while adjusting for age, sex, BMI z-score, SES and prenatal tobacco smoke exposure.

RESULTS

We identified a critical window of susceptibility to Pb exposure, in the late 3rd trimester (5 weeks prior to birth) during which higher Pb exposure was associated with children's increased eGFR. When all elements were assessed as a mixture, we identified late 2nd/early 3rd trimester (weeks 8-17 of gestation) as a window of vulnerability associated with decreased eGFR, with Li and Cr contributing the greatest weights to the association. When stratified by sex, we observed stronger effects among boys than girls.

CONCLUSIONS

Using tooth-matrix biomarkers, we identified discrete developmental exposure windows wherein Pb and metal(loid) mixtures were associated with altered preadolescent kidney function.

Domain-specific effects of prenatal fluoride exposure on child IQ at 4, 5, and 6-12 years in the ELEMENT cohort

OBJECTIVE

Prenatal exposure to fluoride has been associated with adverse neurodevelopmental outcomes. However, the neuropsychological profile of fluoride's developmental neurotoxicity at low levels and the stability of this relationship across childhood has not been characterized. We investigated the longitudinal and domain specific effect of prenatal fluoride exposure on IQ among children ages 4, 5, and 6-12 years in the Early Life Exposures in Mexico to Environmental Toxicants (ELEMENT) cohort.

METHODS

We measured the average of maternal urinary fluoride at each trimester of pregnancy adjusted for creatinine (MUF_CRE). Children were administered the McCarthy Scales of Children's Abilities at ages 4 (N = 386) and 5 (N = 308), and the Wechsler Abbreviated Scale of Intelligence at age 6-12 (N = 278). We used generalized estimating equation (GEE) models to estimate the population averaged effect of MUF_CRE concentration on longitudinal General Cognitive Index (GCI)/Full-Scale IQ (FSIQ), Verbal IQ (VIQ), and Performance IQ (PIQ) scores (N = 348). We tested for possible interactions between MUF_CRE and child sex as well as for MUF_CRE and time point on children's IQ. All models controlled for relevant available covariates.

RESULTS

The mean/median MUF_CRE concentration was 0.90/0.83 mg/L (SD = 0.39; IQR, 0.64-1.11 mg/L). A 0.5 mg/L increase in MUF_CRE predicted an average 2.12-point decrease in GCI/FSIQ (95% CI: -3.49, -0.75) and 2.63-point decrease in PIQ (95% CI: -3.87, -1.40). MUF_CRE was marginally associated with VIQ across time (B = -1.29, 95% CI: -2.60, 0.01). No interactions between MUF_CRE and child sex or MUF_CRE and time were observed.

CONCLUSION

The negative association between prenatal fluoride exposure and longitudinal IQ was driven by decrements in non-verbal intelligence (i.e. PIQ), suggesting that visual-spatial and perceptual reasoning abilities may be more impacted by prenatal fluoride exposure as compared to verbal abilities.

Intermediate- and long-term associations between air pollution and ambient temperature and glycated hemoglobin levels in women of child bearing age

BACKGROUND

Air pollution has been linked to obesity while higher ambient temperatures typically reduce metabolic demand in a compensatory manner. Both relationships may impact glucose metabolism, thus we examined the association between intermediate- and long-term exposure to fine particulate matter (PM2.5) and ambient temperature and glycated hemoglobin(HbA1c), a longer-term marker of glucose control.

METHODS

We assessed 3-month, 6-month, and 12-month average air pollution and ambient temperature at 1-km2 spatial resolution via satellite remote sensing models (2013-2019), and assessed HbA1c at four, six, and eight years postpartum in women enrolled in the Programming Research in Obesity, Growth, Environment and Social Stressors (PROGRESS) cohort based in Mexico City. PM2.5 and ambient temperature were matched to participants' addresses and confirmed by GPS tracker. Using linear mixed-effects models, we examined the association between 3-month, 6-month, and 12-month average PM2.5 and ambient temperature with repeated log-transformed HbA1c values. All models included a random intercept for each woman and were adjusted for calendar year, season, and individual-level confounders (age, marital status, smoking, alcohol consumption level, and education level).

RESULTS

We analyzed 1,265 HbA1c measurements of 484 women. Per 1 µg/m3 increase in 3-month and 6-month PM2.5, HbA1c levels increased by 0.28% (95% confidence interval (95 %CI): 0.14, 0.42%) and 0.28% (95 %CI: 0.04, 0.52%) respectively. No association was seen for 12-month average PM2.5. Per 1 °C increase in ambient temperature, HbA1c levels decreased by 0.63% (95 %CI: -1.06, -0.21%) and 0.61% (95 %CI: -1.08, -0.13%), while the 12-month average again is not associated with HbA1c.

CONCLUSIONS

Intermediate-term exposure to PM2.5 and ambient temperature are associated with opposing changes in HbA1c levels, in this region of high PM2.5 and moderate temperature fluctuation. These effects, measurable in mid-adult life, may portend future risk of type 2 diabetes and possible heart disease.

Third-Trimester Maternal Dietary Patterns Are Associated with Sleep Health among Adolescent Offspring in a Mexico City Cohort

BACKGROUND

Maternal diet during gestation has been linked to infant sleep; whether associations persist through adolescence is unknown.

OBJECTIVES

We explored associations between trimester-specific maternal diet patterns and measures of sleep health among adolescent offspring in a Mexico City birth cohort.

METHODS

Data from 310 mother-adolescent dyads were analyzed. Maternal diet patterns were identified by principal component analysis derived from FFQs collected during each trimester of pregnancy. Sleep duration, midpoint, and fragmentation were obtained from 7-d actigraphy data when adolescents were between 12 and 20 y old. Unstratified and sex-stratified association analyses were conducted using linear regression models, adjusted for potential confounders.

RESULTS

Mean ± SD age of offspring was 15.1 ± 1.9 y, and 52.3% of the sample was female. Three diet patterns were identified during each trimester of pregnancy: the Prudent Diet (PD), high in lean proteins and vegetables; the Transitioning Mexican Diet (TMD), high in westernized foods; and the High Meat & Fat Diet (HMFD), high in meats and fat products. Mean ± SD sleep duration was 8.5 ± 1.5 h/night. Most associations were found in the third trimester. Specifically, PD maternal adherence was associated with shorter sleep duration among offspring (-0.57 h; 95% CI: -0.98, -0.16 h, in the highest tertile compared with the lowest) and earlier sleep midpoint among females (-0.77 h; 95% CI: -1.3, -0.26 h). Adherence to the HMFD and TMD was nonlinearly associated with less fragmented sleep, with the latter only evident among females.

CONCLUSIONS

Findings indicate that maternal dietary patterns, especially during the third trimester of pregnancy, may have long-term impacts on offspring sleep.

Prenatal phthalates, gestational weight gain, and long-term weight changes among Mexican women

BACKGROUND

Phthalates are endocrine disrupting chemicals that may influence weight status; however, few studies have considered weight gain during pregnancy and subsequent long-term weight changes in women.

OBJECTIVE

To determine associations of prenatal phthalate exposure with maternal weight during pregnancy and through up to seven years post-delivery.

METHODS

We analyzed 15 urinary phthalate biomarker concentrations during the 2nd and 3rd trimesters among 874 pregnant women enrolled in the Programming Research in Obesity, Growth Environment and Social Stress Study in Mexico City. We examined three time-specific maternal weight outcomes: gestational weight gain (between 2nd and 3rd trimesters), short-term weight (between 3rd trimester and 12 months post-delivery), and long-term weight (between 18 months and 6-7 years post-delivery). We used Bayesian Kernel Machine Regression (BKMR) to estimate associations for the total phthalate mixture, as well as multivariable linear mixed models for individual phthalate biomarkers.

RESULTS

As a mixture, 2nd trimester urinary phthalate biomarker concentrations were associated with somewhat lower gestational weight gain between the 2nd and 3rd trimesters (interquartile range, IQR, difference: -0.07 standard deviations, SD; 95% credible interval, CrI: -0.20, 0.06); multivariable regression and BKMR models indicated that this inverse association was primarily driven by mono-2-ethyl-5-carboxypentyl terephthalate (MECPTP). Prenatal (2nd and 3rd trimesters) urinary phthalate mixture concentrations were positively associated with maternal weight change through 12 months postpartum (IQR difference: 0.11 SD; 95% CrI: 0.00, 0.23); these associations persisted from 18 months to 6-7 years follow-up (IQR difference: 0.07 SD; 95% CrI: 0.04, 0.10). Postpartum weight changes were associated with mono-3-carboxypropyl phthalate (MCPP) and MECPTP.

CONCLUSIONS

Prenatal phthalate exposure was inversely associated with gestational weight gain and positively associated with long-term changes in maternal weight. Further investigation is required to understand how phthalates may influence body composition and whether they contribute to the development of obesity and other cardiometabolic diseases in women.

Dietary Influences on Urinary Fluoride over the Course of Pregnancy and at One-Year Postpartum

Dietary factors are known to influence urinary fluoride (UF) levels in nonpregnant people. Maternal UF is used as a biomarker of fluoride exposure; however, dietary influences on UF during pregnancy are unknown. We compared UF levels and assessed the associations between UF and five select dietary influences in pregnancy vs. one-year postpartum: dietary fluoride (F), calcium intake from diet (Ca-diet), calcium intake from supplements (Ca-sup), dietary acid load (AL), and table salt use (TS) in 421 women exposed to fluoridated salt in the Mexican diet. Spot UF (mg/L) was measured by microdiffusion/fluoride-specific electrode and dilution-corrected with specific gravity (SG). Dietary variables were estimated from a validated Food Frequency Questionnaire. Comparisons among UF in pregnancy vs. one-year postpartum were performed with non-parametric tests. Associations between dietary variables and UF were assessed using random effect models (for pregnancy) and linear regression (for one-year postpartum). SG-corrected UF (median, range) during pregnancy (0.77, 0.01-4.73 mg/L) did not significantly differ from one-year postpartum (0.75, 0.15-2.62 mg/L) but did increase every 10 gestational weeks, β = 0.05 (CI: 0.00-0.10). Different dietary influences on UF were identified at each state. Although Ca-diet and AL were not associated with UF in either state, Ca-sup decreased UF only during pregnancy, β =  - 0.012 mg/L (CI: - 0.023-0.00). Reporting TS use was associated with 12% increase in UF only at one-year postpartum (p = 0.026). These results suggest different dietary influences on UF in the pregnant state, which need consideration when using UF as a biomarker of fluoride exposure.

Prenatal lead exposure, telomere length in cord blood, and DNA methylation age in the PROGRESS prenatal cohort

BACKGROUND

Lead is a ubiquitous pollutant with deleterious effects on human health and remains a major current public health concern in developing countries. This heavy metal may interfere with nucleic acids via oxidative stress or epigenetic changes that affect biological markers of aging, e.g., telomere length and DNA methylation (DNAm). Telomere shortening associates with biological age in newborns, and DNA methylation at specific CpG sites can be used to calculate "epigenetic clocks".

OBJECTIVE

The aim of this study was to examine the associations of prenatal lead exposures with telomere length and DNA-methylation-based predictors of age in cord blood.

DESIGN

The study included 507 mother-child pairs from the Programming Research in Obesity, Growth, Environment and Social Stressors (PROGRESS) study, a birth cohort in Mexico City. Maternal blood (second trimester, third trimester and at delivery) and bone lead levels (one month postpartum) were measured using inductively coupled plasma-mass spectrometry and X-ray fluorescence, respectively. Cord blood leukocyte telomere length was measured using quantitative PCR and apparent age by DNA methylation biomarkers, i.e., Horvath's DNA methylation age and the Knight's predictor of gestational age.

RESULTS

Average maternal age was 28.5 ± 5.5 years, and 51.5% reported low socioeconomic status. Children's mean telomere length was 1.2 ± 1.3 relative units, and mean DNA methylation ages using the Horvath's and Knight's clocks were -2.6 ± 0.1 years and 37.9 ± 1.4 weeks (mean ± SD), respectively. No significant associations were found between maternal blood and bone lead concentrations with telomere length and DNAm age in newborns.

CONCLUSION

We found no associations of prenatal lead exposure with telomere length and DNA methylation age biomarkers.

Prenatal trace elements mixture is associated with learning deficits on a behavioral acquisition task among young children

Children are exposed to many trace elements throughout their development. Given their ubiquity and potential to have effects on children's neurodevelopment, these exposures are a public health concern. This study sought to identify trace element mixture-associated deficits in learning behavior using operant testing in a prospective cohort. We included 322 participants aged 6-7 years recruited in Mexico City with complete data on prenatal trace elements measurements (third trimester blood lead and manganese levels, and & urine cadmium and arsenic levels), demographic covariates, and the Incremental Repeated Acquisition (IRA), an associative learning task. Weighted quantile sum (WQS) regression models were used to estimate the joint association of the mixture of all four trace elements and IRA performance. Performance was adversely impacted by the mixture, with different elements relating to different aspects of task performance suggesting that prenatal exposure to trace element mixtures yields a broad dysregulation of learning behavior.

Prenatal maternal phthalate exposures and trajectories of childhood adiposity from four to twelve years

BACKGROUND/AIM

Adiposity trajectories reflect dynamic process of growth and may predict later life health better than individual measures. Prenatal phthalate exposures may program later childhood adiposity, but findings from studies examining these associations are conflicting. We investigated associations between phthalate biomarker concentrations during pregnancy with child adiposity trajectories.

METHODS

We followed 514 mother-child pairs from the Mexico City PROGRESS cohort from pregnancy through twelve years. We measured concentrations of nine phthalate biomarkers in 2nd and 3rd trimester maternal urine samples to create a pregnancy average using the geometric mean. We measured child BMI z-score, fat mass index (FMI), and waist-to-height ratio (WHtR) at three study visits between four and 12 years of age. We identified adiposity trajectories using multivariate latent class growth modeling, considering BMI z-score, FMI, and WHtR as joint indicators of latent adiposity. We estimated associations of phthalates biomarkers with class membership using multinomial logistic regression. We used quantile g-computation to estimate the potential effect of the total phthalate mixture and assessed effect modification by sex.

RESULTS

We identified three trajectories of child adiposity, a "low-stable", a "low-high", and a "high-high" group. A doubling of the sum of di (2-ethylhexyl) phthalate metabolites (ΣDEHP), was associated with 1.53 (1.08, 2.19) greater odds of being in the "high-high" trajectory in comparison to the "low-stable" group, whereas a doubling in di-isononyl phthalate metabolites (ΣDiNP) was associated with 1.43 (1.02, 2.02) greater odds of being in the "low-high" trajectory and mono (carboxy-isononyl) phthalate (MCNP) was associated with 0.66 (0.45, 97) lower odds of being in the "low-high" trajectory. No sex-specific associations or mixture associations were observed.

CONCLUSIONS

Prenatal concentrations of urinary DEHP metabolites, DiNP metabolites, and MCNP, a di-isodecyl phthalate metabolite, were associated with trajectories of child adiposity. The total phthalate mixture was not associated with early life child adiposity.

Prenatal maternal pesticide exposure in relation to sleep health of offspring during adolescence

STUDY OBJECTIVES

The neurobiological processes involved in establishing sleep regulation are vulnerable to environmental exposures as early as seven weeks of gestation. Studies have linked in utero pesticide exposure to childhood sleep-disordered breathing. However, the impact of in utero pesticide exposure on the sleep health of adolescents remains unexplored.

MATERIALS AND METHODS

Data from 137 mother-adolescent pairs from a Mexico City cohort were analyzed. We used maternal urinary 3-phenoxybenzoic acid (3-PBA, pyrethroid metabolite) and 3, 5, 6-trichloro-2-pyridinol (TCPy, chlorpyrifos metabolite) from trimester three to estimate in utero pesticide exposure. Among adolescents, we obtained repeated measures of objectively assessed sleep duration, midpoint, and fragmentation using wrist-actigraphy devices for 7 consecutive days in 2015 and 2017. Unstratified and sex-stratified associations between maternal urinary 3-PBA and TCPy and adolescent sleep measures were examined using generalized linear mixed models (GLMMs). We also examined the interactive effects of maternal pesticide exposure and offspring sex on sleep outcomes.

RESULTS

3-PBA and TCPy were detected in 44.4% and 93% of urine samples, respectively. Adjusted findings demonstrated that higher exposure to maternal TCPy was associated with longer sleep duration and later sleep timing. Findings from interaction tests between maternal pesticide exposure and offspring sex were not statistically significant, although adjusted sex-stratified findings showed that the association between TCPy with duration and midpoint was evident only among female offspring. To illustrate, those in the highest tertile of exposure had a 59 minute (95% CI: 12.2, 104.8) (p, trend = 0.004) longer sleep duration and a 0.6 hour (95% CI: 0.01, 1.3) (p, trend = 0.01) later sleep midpoint. We found no significant associations between 3-PBA and sleep outcomes.

CONCLUSION

Within a cohort of mother-adolescent pairs, we found associations between maternal prenatal pesticide exposure and longer sleep duration and later sleep timing among adolescent offspring. Further, this association may be female-specific.

Trimester two gestational exposure to bisphenol A and adherence to mediterranean diet are associated with adolescent offspring oxidative stress and metabolic syndrome risk in a sex-specific manner

Background

Exposure to prenatal bisphenol A (BPA) and Mediterranean Diet Score (MDS) has been linked to metabolic risk in child offspring. It remains unclear if independent and interactive effects persist in adolescence.

Methods

We examined prenatal BPA and MDS on adolescent offspring metabolic syndrome risk score (MRS) and 8-isoprostane (8-iso), a biomarker of oxidative stress. Data from maternal-adolescent dyads from a Mexico City cohort were utilized, including trimester-specific prenatal BPA from spot urine and MDS from food frequency questionnaires. Offspring socio-demographic data and biomarkers to estimate MRS and 8-iso were obtained during peri-adolescence.

Results

Adjusted linear regression models examined associations between trimester-specific BPA, MDS, and BPA^*MDS on outcomes. Sex-stratified analyses revealed a significant association between MDS with increased 8-iso (β = 0.064, p < 0.05), and a marginal association between trimester two BPA with increased 8-iso (β = 0.237), while MDS modified the marginal association between BPA and 8-iso in females (β = 0.046). A negative, marginal association was observed between trimester two BPA and MRS (β = - 0.728), while BPA ^* MDS was marginally, positively associated with MRS (β = 0.152) in males.

Conclusions

Study findings indicate that trimester two prenatal BPA and maternal adherence to a Mediterranean diet may have sexually dimorphic effects on adolescent offspring oxidative stress and metabolic syndrome risk.

Prenatal metal mixture concentrations and reward motivation in children

Reward motivation is a complex umbrella term encompassing the cognitions, emotions, and behaviors involved in the activation, execution, and persistence of goal-directed behavior. Altered reward motivation in children is characteristic of many neurodevelopmental and psychiatric disorders. Previously difficult to operationalize, the Progressive Ratio (PR) task has been widely used to assess reward motivation in animal and human studies, including children. Because the neural circuitry supporting reward motivation starts developing during pregnancy, and is sensitive to disruption by environmental toxicants, including metals, the goal of this study was to examine the association between prenatal concentrations of a mixture of neurotoxic metals and reward motivation in children. We measured reward motivation by administering a PR test to 373 children ages 6-8 years enrolled in the Programming Research in Obesity, Growth, Environment and Social Stressors (PROGRESS) Study in Mexico City. Children were asked to press a response lever for a token reward; one press on the response lever was required to earn the first token and each subsequent token required an additional 10 lever presses. Maternal blood concentrations of lead, manganese, zinc, arsenic, cadmium, and selenium were measured using inductively-coupled plasma mass spectrometry during the 2nd and 3rd trimesters of pregnancy. We performed generalized Weighted Quantile Sum (gWQS) regression analyses to examine associations between the prenatal metal mixture and reward motivation; adjusting for child sex, birthweight and age; and maternal IQ, education, and socioeconomic status. The prenatal metal mixture was significantly associated with higher motivation as indicated by more lever presses (ß = 0.02, p < 0.001) and a shorter time between receiving the reinforcer and the first press (ß = 0.23, p = 0.01), and between subsequent presses (ß = 0.07, p = 0.005). Contributions of different metals to this association differed by trimester and child sex. These findings suggest that children with increased exposure to metal during the 2nd and 3rd trimesters of gestation demonstrate increased reward motivation, which may reflect a tendency to perseverate or hypersensitivity to positive reinforcement.

Sexually dimorphic associations between prenatal blood lead exposure and performance on a behavioral testing battery in children

BACKGROUND

Associations between lead (Pb) and neurodevelopment have been studied widely in the context of global measures of cognitive function, such as IQ. Operant test batteries consist of behavioral tasks that can be used to target discrete cognitive and behavioral mechanisms, which contribute to global cognitive faculties.

OBJECTIVES

The goals of this study were to identify Pb-associated deficits in cognitive development and determine the underlying mechanisms involved, utilizing an operant test battery. We evaluated effect modification by child sex.

METHODS

This study utilized data from a prospective cohort in Mexico City. We included 549 participants aged 6-to-7 years with complete data on prenatal blood Pb measurements, Operant Test Battery (OTB) tasks, and demographic covariates. General linear models were used to examine the association of Pb levels at each prenatal timepoint and OTB performance. Effect modification by child sex was evaluated using 2-way interaction terms.

RESULTS

In three of the operant tasks, we observed that higher late-pregnancy blood Pb concentrations were associated with greater response latencies. In the temporal processing task, we observed that higher late-pregnancy Pb exposure was associated with worse overall task performance. Further, in two operant tasks, the effects of Pb were dependent on the sex of the child, such that the effects of Pb were more pronounced in females in the condition position responding task, but stronger in males in the temporal processing task.

CONCLUSIONS

Our results suggest that prenatal Pb concentrations yield broad dysregulation of executive functions, which can be attributed to dysregulation of temporal processing. In addition, we observed sex differences in two operant tasks suggesting that some Pb effects on neurocognitive function may be sexually dimorphic.

Lead exposure and serum metabolite profiles in pregnant women in Mexico City

BACKGROUND

Lead (Pb) exposure is a global health hazard causing a wide range of adverse health outcomes. Yet, the mechanisms of Pb toxicology remain incompletely understood, especially during pregnancy. To uncover biological pathways impacted by Pb exposure, this study investigated serum metabolomic profiles during the third trimester of pregnancy that are associated with blood Pb and bone Pb.

METHODS

We used data and specimens from 99 women enrolled in the Programming Research in Obesity, Growth, Environment, and Social Stressors birth cohort in Mexico City. Maternal Pb exposure was measured in whole blood samples from the third trimester of pregnancy and in the tibia and patella bones at 1 month postpartum. Third-trimester serum samples underwent metabolomic analysis; metabolites were identified based on matching to an in-house analytical standard library. A metabolome-wide association study was performed using multiple linear regression models. Class- and pathway-based enrichment analyses were also conducted.

RESULTS

The median (interquartile range) blood Pb concentration was 2.9 (2.6) µg/dL. Median bone Pb, measured in the tibia and patella, were 2.5 (7.3) µg/g and 3.6 (9.5) µg/g, respectively. Of 215 total metabolites identified in serum, 31 were associated with blood Pb (p < 0.05). Class enrichment analysis identified significant overrepresentation of metabolites classified as fatty acids and conjugates, amino acids and peptides, and purines. Tibia and patella Pb were associated with 14 and 8 metabolites, respectively (p < 0.05). Comparing results from bone and blood Pb, glycochenodeoxycholic acid, glycocholic acid, and 1-arachidonoylglycerol were positively associated with blood Pb and tibia Pb, and 7-methylguanine was negatively associated with blood Pb and patella Pb. One metabolite, 5-aminopentanoic acid, was negatively associated with all three Pb measures.

CONCLUSIONS

This study identified serum metabolites in pregnant women associated with Pb measured in blood and bone. These findings provide insights on the metabolic profile around Pb exposure in pregnancy and information to guide mechanistic studies of toxicological effects for mothers and children.

Maternal Phthalates Exposure and Blood Pressure during and after Pregnancy in the PROGRESS Study

BACKGROUND

Phthalate exposure is ubiquitous and may affect biological pathways related to regulators of blood pressure. Given the profound changes in vasculature during pregnancy, pregnant women may be particularly susceptible to the potential effects of phthalates on blood pressure.

OBJECTIVES

We examined associations of phthalate exposure during pregnancy with maternal blood pressure trajectories from mid-pregnancy through 72 months postpartum.

METHODS

Women with singleton pregnancies delivering a live birth in Mexico City were enrolled during the second trimester (n=892). Spot urine samples from the second and third trimesters were analyzed for 15 phthalate metabolites. Blood pressure and covariate data were collected over nine visits through 72 months postpartum. We used linear, logistic, and linear mixed models; latent class growth models (LCGMs); and Bayesian kernel machine regression to estimate the relationship of urinary phthalate biomarkers with maternal blood pressure.

RESULTS

As a joint mixture, phthalate biomarker concentrations during pregnancy were associated with higher blood pressure rise during mid-to-late gestation. With respect to individual biomarkers, second trimester concentrations of monobenzyl phthalate (MBzP) and di(2-ethylhexyl) phthalate biomarkers (ΣDEHP) were associated with higher third trimester blood pressure. Two trajectory classes were identified by LCGM, characterized by increasing blood pressure through 72 months postpartum ("increase-increase") or decreased blood pressure through 18 months postpartum with a gradual increase thereafter ("decrease-increase"). Increasing exposure to phthalate mixtures during pregnancy was associated with higher odds of being in the increase-increase class. Similar associations were observed for mono-2-ethyl-5-carboxypentyl terephthalate (MECPTP) and dibutyl phthalate (ΣDBP) biomarkers. When specific time periods were examined, we observed specific temporal relationships were observed for ΣDEHP, MECPTP, MBzP, and ΣDBP.

DISCUSSION

In our cohort of pregnant women from Mexico City, exposure to phthalates and phthalate biomarkers was associated with higher blood pressure during late pregnancy, as well as with long-term changes in blood pressure trajectories. https://doi.org/10.1289/EHP8562.

Prenatal PM2.5 exposure in the second and third trimesters predicts neurocognitive performance at age 9-10 years: A cohort study of Mexico City children

INTRODUCTION

Prenatal exposure to fine particulate matter air pollution (PM2.5) is an important, under-studied risk factor for neurodevelopmental dysfunction. We describe the relationships between prenatal PM2.5 exposure and vigilance and inhibitory control, executive functions related to multiple health outcomes in Mexico City children.

METHODS

We studied 320 children enrolled in Programming Research in Obesity, GRowth, Environment and Social Stressors, a longitudinal birth cohort study in Mexico City. We used a spatio-temporal model to estimate daily prenatal PM2.5 exposure at each participant's residential address. At age 9-10 years, children performed three Go/No-Go tasks, which measure vigilance and inhibitory control ability. We used Latent class analysis (LCA) to classify performance into subgroups that reflected neurocognitive performance and applied multivariate regression and distributed lag regression modeling (DLM) to test overall and time-dependent associations between prenatal PM2.5 exposure and Go/No-Go performance.

RESULTS

LCA detected two Go/No-Go phenotypes: high performers (Class 1) and low performers (Class 2). Predicting odds of Class 1 vs Class 2 membership based on prenatal PM2.5 exposure timing, logistic regression modeling showed that average prenatal PM2.5 exposure in the second and third trimesters correlated with increased odds of membership in low-performance Class 2 (OR = 1.59 (1.16, 2.17), p = 0.004). Additionally, DLM analysis identified a critical window consisting of gestational days 103-268 (second and third trimesters) in which prenatal PM2.5 exposure predicted poorer Go/No-Go performance.

DISCUSSION

Increased prenatal PM2.5 exposure predicted decreased vigilance and inhibitory control at age 9-10 years. These findings highlight the second and third trimesters of gestation as critical windows of PM2.5 exposure for the development of vigilance and inhibitory control in preadolescent children. Because childhood development of vigilance and inhibitory control informs behavior, academic performance, and self-regulation into adulthood, these results may help to describe the relationship of prenatal PM2.5 exposure to long-term health and psychosocial outcomes. The integrative methodology of this study also contributes to a shift towards more holistic analysis.

The associations of phthalate biomarkers during pregnancy with later glycemia and lipid profiles

BACKGROUND

Pregnancy induces numerous cardiovascular and metabolic changes. Alterations in these sensitive processes may precipitate long-term post-delivery health consequences. Studies have reported associations between phthalates and metabolic complications of pregnancy, but no study has investigated metabolic outcomes beyond pregnancy.

OBJECTIVES

To examine associations of exposure to phthalates during pregnancy with post-delivery metabolic health.

DESIGN

We quantified 15 urinary phthalate biomarker concentrations during the second and third trimesters among 618 pregnant women from Mexico City. Maternal metabolic health biomarkers included fasting blood measures of glycemia [glucose, insulin, Homeostatic Model Assessment of Insulin Resistance [HOMA-IR], % hemoglobin A1c (HbA1c%)] and lipids (total, high-density lipoprotein (HDL), low-density lipoprotein (LDL) cholesterol, triglycerides), at 4-5 and 6-8 years post-delivery. To estimate the influence of the phthalates mixture, we used Bayesian weighted quantile sum regression and Bayesian kernel machine regression; for individual biomarkers, we used linear mixed models.

RESULTS

As a mixture, higher urinary phthalate biomarker concentrations during pregnancy were associated with post-delivery concentrations of plasma glucose (interquartile range [IQR] difference: 0.13 SD, 95%CrI: 0.05, 0.20), plasma insulin (IQR difference: 0.06 SD, 95%CrI: -0.02, 0.14), HOMA-IR (IQR difference: 0.08 SD, 95% CrI: 0.01, 0.16), and HbA1c% (IQR difference: 0.15 SD, 95%CrI: 0.05, 0.24). Associations were primarily driven by mono-2-ethyl-5-carboxypentyl terephthalate (MECPTP) and the sum of dibutyl phthalate biomarkers (∑DBP). The phthalates mixture was associated with lower HDL (IQR difference: -0.08 SD, 95%CrI: -0.16, -0.01), driven by ∑DBP and monoethyl phthalate (MEP), and higher triglyceride levels (IQR difference: 0.15 SD, 95%CrI: 0.08, 0.22), driven by MECPTP and MEP. The overall mixture was not associated with total cholesterol and LDL. However, ∑DBP and MEP were associated with lower and higher total cholesterol, respectively, and MECPTP and ∑DBP were associated with lower LDL.

CONCLUSIONS

Phthalate exposure during pregnancy is associated with adverse long-term changes in maternal metabolic health. A better understanding of timing of the exact biological changes and their implications on metabolic disease risk is needed.

Prenatal urinary concentrations of phthalate metabolites and behavioral problems in Mexican children: The Programming Research in Obesity, Growth Environment and Social Stress (PROGRESS) study

BACKGROUND

Phthalate exposure has been associated with increased childhood behavioral problems. Existing studies failed to include phthalate replacements and did not account for high correlations among phthalates. Phthalates' exposure is higher in Mexico than in U.S. locations, making it an ideal target population for this study.

AIM

To examine associations between 15 maternal prenatal phthalate metabolite concentrations and children's behavioral problems.

METHODS

We quantified phthalate metabolites in maternal urine samples from maternal-child dyads (n = 514) enrolled in the Programming Research in Obesity, Growth Environment and Social Stress (PROGRESS) birth cohort in Mexico City. We performed least absolute shrinkage and selection operator (LASSO) regressions to identify associations between specific-gravity adjusted log₂-transformed phthalate metabolites and parent-reported 4-6 year old behavior on the Behavior Assessment System for Children (BASC-2), accounting for metabolite correlations. We adjusted for socio-demographic and birth-related factors, and examined associations stratified by sex.

RESULTS

Higher prenatal mono-2-ethyl-5-carboxypentyl terephthalate (MECPTP) urinary concentrations were associated with increased hyperactivity scores in the overall sample (β = 0.57, 95% CI = 0.17, 1.13) and in girls (β = 0.54, 95% CI = 0.16, 1.08), overall behavioral problems in boys (β = 0.58, 95% CI = 0.20, 1.15), and depression scores in boys (β = 0.44, 95% CI = 0.06, 0.88). Higher prenatal monobenzyl phthalate (MBzP) concentrations were associated with reduced hyperactivity scores in girls (ß = -0.54, 95% CI = -1.08, -0.21).

DISCUSSION

Our findings suggested that prenatal concentrations of phthalates and their replacements altered child neurodevelopment and those associations may be influenced sex.

Relationships of beverage consumption and actigraphy-assessed sleep parameters among urban-dwelling youth from Mexico

OBJECTIVE

To examine whether usual beverage intake was associated with sleep timing, duration and fragmentation among adolescents.

DESIGN

Usual beverage intake was assessed with a FFQ. Outcomes included sleep duration, midpoint (median of bed and wake times) and fragmentation, assessed with 7-d actigraphy. Sex-stratified linear regression was conducted with sleep characteristics as separate outcomes and quantiles of energy-adjusted beverage intake as exposures, accounting for age, maternal education, physical activity and smoking.

SETTING

Mexico City.

PARTICIPANTS

528 adolescents residing in Mexico City enrolled in a longitudinal cohort.

RESULTS

The mean age (sd) was 14·4 (2·1) years; 48 % were male. Among males, milk and water consumption were associated with longer weekday sleep duration (25 (95 % CI 1, 48) and 26 (95 % CI 4, 47) more minutes, in the 4th compared to the 1st quartile); and higher 100 % fruit juice consumption was related to earlier weekday sleep timing (-22 (95 % CI -28, 1) minutes in the 1st compared to the last quantile; P = 0·03). Among females, soda was associated with higher sleep fragmentation (1·6 (95 % CI 0·4, 2·8) % in the 4th compared to the 1st), and coffee/tea consumption was related to shorter weekend sleep duration (-23 (95 % CI -44, 2) minutes in the 4th compared to the 1st).

CONCLUSIONS

Among females, adverse associations with sleep were observed for caffeinated drinks, while males with higher consumption of healthier beverage options (water, milk and 100 % juice) had evidence of longer and earlier-timed sleep. Potential mechanisms involving melatonin and tryptophan should be further investigated.

Prenatal Lead (Pb) Exposure and Peripheral Blood DNA Methylation (5mC) and Hydroxymethylation (5hmC) in Mexican Adolescents from the ELEMENT Birth Cohort

BACKGROUND

Gestational lead (Pb) exposure can adversely affect offspring health through multiple mechanisms, including epigenomic alterations via DNA methylation (5mC) and hydroxymethylation (5hmC), an intermediate in oxidative demethylation. Most current methods do not distinguish between 5mC and 5hmC, limiting insights into their individual roles.

OBJECTIVE

Our study sought to identify the association of trimester-specific (T1, T2, T3) prenatal Pb exposure with 5mC and 5hmC levels at multiple cytosine-phosphate-guanine sites within gene regions previously associated with prenatal Pb (HCN2, NINJ2, RAB5A, TPPP) in whole blood leukocytes of children ages 11-18 years of age.

METHODS

Participants from the Early Life Exposure in Mexico to Environmental Toxicants (ELEMENT) birth cohorts were selected (n=144) for pyrosequencing analysis following oxidative or standard sodium bisulfite treatment. This workflow directly quantifies total methylation (5mC+5hmC) and 5mC only; 5hmC is estimated by subtraction.

RESULTS

Participants were 51% male, and mean maternal blood lead levels (BLL) were 6.43±5.16μg/dL in Trimester 1 (T1), 5.66±5.21μg/dL in Trimester 2 (T2), and 5.86±4.34μg/dL in Trimester 3 (T3). In addition, 5hmC levels were calculated for HCN2 (mean±standard deviation(SD), 2.08±4.18%), NINJ2 (G/C: 2.01±5.95; GG: 0.90±3.97), RAB5A (0.66±0.80%), and TPPP (1.11±6.67%). Furthermore, 5mC levels were measured in HCN2 (81.3±9.63%), NINJ2 (heterozygotes: 38.6±7.39%; GG homozygotes: 67.3±9.83%), RAB5A (1.41±1.21%), and TPPP (92.5±8.03%). Several significant associations between BLLs and 5mC/5hmC were identified: T1 BLLs with 5mC in HCN2 (β=-0.37, p=0.03) and 5hmC in NINJ2 (β=0.49, p=0.003); T2 BLLs with 5mC in HCN2 (β=0.37, p=0.03) and 5hmC in NINJ2 (β=0.27, p=0.008); and T3 BLLs with 5mC in HCN2 (β=0.50, p=0.01) and NINJ2 (β=-0.35, p=0.004) and 5hmC in NINJ2 (β=0.45, p<0.001). NINJ2 5mC was negatively correlated with gene expression (Pearson r=-0.5, p-value=0.005), whereas 5hmC was positively correlated (r=0.4, p-value=0.04).

DISCUSSION

These findings suggest there is variable 5hmC in human whole blood and that prenatal Pb exposure is associated with gene-specific 5mC and 5hmC levels at adolescence, providing evidence to consider 5hmC as a regulatory mechanism that is responsive to environmental exposures. https://doi.org/10.1289/EHP8507.

Maternal anxiety during pregnancy and newborn epigenome-wide DNA methylation

Maternal anxiety during pregnancy is associated with adverse foetal, neonatal, and child outcomes, but biological mechanisms remain unclear. Altered foetal DNA methylation (DNAm) has been proposed as a potential underlying mechanism. In the current study, we performed a meta-analysis to examine the associations between maternal anxiety, measured prospectively during pregnancy, and genome-wide DNAm from umbilical cord blood. Sixteen non-overlapping cohorts from 12 independent longitudinal studies of the Pregnancy And Childhood Epigenetics Consortium participated, resulting in a combined dataset of 7243 mother-child dyads. We examined prenatal anxiety in relation to genome-wide DNAm and differentially methylated regions. We observed no association between the general symptoms of anxiety during pregnancy or pregnancy-related anxiety, and DNAm at any of the CpG sites, after multiple-testing correction. Furthermore, we identify no differentially methylated regions associated with maternal anxiety. At the cohort-level, of the 21 associations observed in individual cohorts, none replicated consistently in the other cohorts. In conclusion, contrary to some previous studies proposing cord blood DNAm as a promising potential mechanism explaining the link between maternal anxiety during pregnancy and adverse outcomes in offspring, we found no consistent evidence for any robust associations between maternal anxiety and DNAm in cord blood. Larger studies and analysis of DNAm in other tissues may be needed to establish subtle or subgroup-specific associations between maternal anxiety and the foetal epigenome.

Association between cumulative childhood blood lead exposure and hepatic steatosis in young Mexican adults

BACKGROUND

Exposure to environmental toxicants may play a role in the pathogenesis of Non Alcoholic Fatty Liver Disease (NAFLD). Cumulative exposure to lead (Pb) has chronic and permanent effects on liver function. Pediatric populations are vulnerable to the toxic effects of Pb, even at low exposure levels. The purpose of the study was to estimate the association between cumulative Pb exposure during childhood and hepatic steatosis biomarkers in young Mexican adults.

METHODS

A subsample of 93 participants from the ELEMENT cohort were included in this study. Childhood blood samples were collected annually from ages 1-4 years and were used to calculate the Cumulative Childhood Blood Lead Levels (CCBLL). Hepatic steatosis during adulthood was defined as an excessive accumulation of hepatic triglycerides (>5%) determined using Magnetic Resonance Imaging (MRI). Liver enzymes were also measured at this time, and elevated liver enzyme levels were defined as ALT (≥30 IU/L), AST (≥30 IU/L), and GGT (≥40 IU/L). Adjusted linear regression models were fit to examine the association between CCBLL (quartiles) and the hepatic steatosis in young adulthood.

RESULTS

In adulthood, the mean age was 21.4 years, 55% were male. The overall prevalence of hepatic steatosis by MRI was 19%. Elevate levels of the enzymes ALT, AST, and GGT were present in 25%, 15%, and 17% of the sample, respectively. We found a positive association between the highest quartile of CCBLL with the steatosis biomarkers of hepatic triglycerides (Q4 vs. Q1: β = 6.07, 95% CI: 1.91-10.21), elevated ALT (Q4 vs. Q1: β = 14.5, 95% CI: 1.39-27.61) and elevated AST (Q4 vs. Q1: β = 7.23, 95% CI: 0.64-13.82). No significant associations were found with GGT.

CONCLUSIONS

Chronic Pb exposure during early childhood is associated with a higher levels of hepatic steatosis biomarkers and hepatocellular injury in young adulthood. More actions should be taken to eliminate sources of Pb during the first years of life.

Exposure to Phenols, Phthalates, and Parabens and Development of Metabolic Syndrome Among Mexican Women in Midlife

Background: Evidence suggests exposure to endocrine-disrupting chemicals (EDCs) can influence Metabolic Syndrome (MetS) risk in adults, but it is unclear if EDCs impact women during midlife. We examined if EDCs measured in adult women were predictive of MetS and its components 9 years later. Methods: We measured urinary phthalate metabolites, phenols, and parabens collected in 2008 among 73 females from the ELEMENT study. MetS and its components (Abdominal Obesity, Hypertriglyceridemia, Cholesterolemia, Hypertension, and Hyperglycemia) were assessed in 2017. We regressed log-transformed EDC concentrations on MetS and MetS components using logistic regression, adjusting for age and physical activity. Results: At follow-up, the mean (SD) age was 46.6 (6.3) years; the prevalence of MetS was 34.3%. Sum of dibutyl phthalate metabolites (ΣDBP), monobenzyl phthalate (MBzP), and monoethyl phthalate (MEP) were associated with an increased odds of hypertriglyceridemia. 2,5-dichlorophenol (2,5 DCP) and 2,4-dichlorophenol (2,4 DCP) were associated with increased odds of hypertriglyceridemia. The odds of hypertension were 4.18 (95% CI: 0.98, 17.7, p < 0.10) and 3.77 (95% CI: 0.76, 18.62, p < 0.10) times higher for every IQR increase in MCOP and propyl paraben, respectively. The odds of hyperglycemia were 0.46 (95% CI: 0.18, 1.17 p < 0.10) times lower for every IQR increase in the sum of di-2-ethylhexyl phthalate metabolites (ΣDEHP), and the odds of abdominal obesity were 0.70 (95% CI: 0.40, 1.21, p < 0.10) lower for every IQR increase in the concentration of triclosan. Conclusion: We found EDCs measured in 2008 were marginally predictive of hypertriglyceridemia and hypertension 9 years later. Results suggest that lower exposure to certain toxicants was related to lower markers of metabolic risk among midlife women.

Prenatal maternal phthalate exposures and child lipid and adipokine levels at age six: A study from the PROGRESS cohort of Mexico City

BACKGROUND

Prenatal phthalate exposures may affect processes that underlie offspring cardiometabolic health, but findings from studies examining these associations are conflicting. We examined associations between biomarkers of phthalate exposures during pregnancy with child lipid and adipokine levels.

METHODS

Data were from 463 mother-child pairs in the PROGRESS cohort of Mexico City. We quantified 15 phthalate metabolites in 2nd and 3rd trimester maternal urine samples and created an average pregnancy measure using the geometric mean. We evaluated the 15 metabolites as nine biomarkers, including four metabolite molar sums. We measured fasting serum triglycerides, non-HDL cholesterol, leptin, and adiponectin in children at the six-year follow-up visit (mean = 6.8 years). We estimated associations using linear regression, Bayesian kernel machine regression (BKMR), and weighted quantile sum (WQS) and assessed effect modification by sex.

RESULTS

In BKMR and WQS models, higher concentrations of the total mixture of phthalate biomarkers were associated with lower triglycerides (β = -3.7% [-6.5, -0.78] per 1 unit increase in WQS biomarker index) and non-HDL cholesterol (β = -2.0 [-3.7, -0.25] ng/ml per increase in WQS biomarker index). Associations between individual biomarkers and child outcomes were largely null. We observed some evidence of effect modification by child sex for mono-3-carboxypropyl phthalate (β = 19.4% [1.26, 40.7] per doubling of phthalate) and monobenzyl phthalate (β = -7.6% [-14.4, -0.23]) in girls for adiponectin.

CONCLUSIONS

Individual prenatal phthalate biomarkers were not associated with child lipid or adipokine levels. Contrary to our hypothesis, the total phthalate mixture was associated with lower child triglycerides and non-HDL cholesterol.

Association of Dietary Fluoride Intake and Diet Variables with Dental Caries in Adolescents from the ELEMENT Cohort Study

To examine the association of dietary fluoride intake, total carbohydrate consumption and other key dietary variables with dental caries experience among adolescents, a cross-sectional analysis was conducted in a sample of 402 participants from the Early Life Exposures in Mexico to Environmental Toxicants cohort. The presence and severity of dental caries were assessed using the International Caries Detection and Assessment System (ICDAS) to calculate the number of decayed, missing, and filled teeth or surfaces (D1MFT/D4MFT). The dietary intake of fluoride, energy, carbohydrates, and food groups was estimated using a validated food frequency questionnaire (FFQ). Multivariate zero-inflated negative binomial regression models and negative binomial regression models were run to estimate the association of fluoride intake (mg/day) and total carbohydrate intake (g/day) with the D1MFT/D4MFT index. We found that 80% of the adolescents experienced dental caries (D1MFT >0), with 30% presenting cavitated lesions (D4MFT >0). The mean scores for D1MFT and D4MFT were 6.2 (SD 5.3) and 0.67 (SD 1.3), respectively. The median intake of fluoride estimated by the FFQ was 0.015 mg/kg/day. This intake was statistically higher in participants with a D4MFT = 0 compared to those with a D4MFT >0 (0.90 vs. 0.82 mg/day; 0.016 vs. 0.014 mg/kg/day; p < 0.05). For D1MFT, D1MFS, D4MFT, and D4MFS scores, a higher fluoride consumption (mg/day) from foods and beverages was associated with a statistically significant reduction in the number of lesions. The reported frequency of consumption of sugary foods in a whole day was statistically higher in those with D1MFT >0 than in those with D1MFT = 0 (p < 0.05). The total carbohydrate intake (g/day) was positively associated with dental caries experience. We conclude that a higher fluoride intake through foods and beverages is associated with a lower dental caries experience among adolescents; this effect was seen even when the dietary intake of fluoride was 0.015 mg/kg/day, which is lower than the average intake recommendation. In contrast, a higher total carbohydrate intake and the frequency of intake of sugary foods were associated with a higher dental caries experience, with no apparent threshold for the effects.

Childhood emotional and behavioral characteristics are associated with soda intake: A prospective study in Mexico City

OBJECTIVES

To evaluate whether childhood emotional and behavioral characteristics are associated with soda intake.

METHODS

The study population included 391 Mexico City adolescents enrolled in a birth cohort study. When children were between 6 and 12 years of age, the Behavioral Assessment System for Children (BASC)-2 was administered. Nondiet soda intake was measured concurrently and again when participants were of peripubertal ages via food frequency questionnaire. Linear regression models were run with soda mL/day (cross-sectional and change in soda over time) as the outcome and BASC composite scores as predictors (in separate models), adjusting for confounders.

RESULTS

At baseline, children were 8.3 (SD 1.3) years (49% males). Three scales out of 18 examined had statistically significant associations. Parent-reported adaptive skills were inversely associated with concurrent soda intake (β = -2.29 with 95% CI -4.27 to -0.31). Parent-reported internalizing problems (higher = more problems) were related to higher change in soda intake from childhood to adolescence (β = 5.83 with 95% CI 0.98-10.68; N = 191). Self-reported school problems were associated with a higher change in soda intake over time (β = 9.46 with 95% CI 2.10-16.82; N = 122).

CONCLUSIONS

Parent- and self-reported emotional and behavioral difficulties in childhood were associated with soda consumption and changes in soda consumption over time.