Effects of Childhood Asthma on the Development of Obesity among School-aged Children

RATIONALE

Asthma and obesity often occur together in children. It is unknown whether asthma contributes to the childhood obesity epidemic.

OBJECTIVES

We aimed to investigate the effects of asthma and asthma medication use on the development of childhood obesity.

METHODS

The primary analysis was conducted among 2,171 nonobese children who were 5-8 years of age at study enrollment in the Southern California Children's Health Study (CHS) and were followed for up to 10 years. A replication analysis was performed in an independent sample of 2,684 CHS children followed from a mean age of 9.7 to 17.8 years.

MEASUREMENTS AND MAIN RESULTS

Height and weight were measured annually to classify children into normal, overweight, and obese categories. Asthma status was ascertained by parent- or self-reported physician-diagnosed asthma. Cox proportional hazards models were fitted to assess associations of asthma history with obesity incidence during follow-up. We found that children with a diagnosis of asthma at cohort entry were at 51% increased risk of developing obesity during childhood and adolescence compared with children without asthma at baseline (hazard ratio, 1.51; 95% confidence interval, 1.08-2.10) after adjusting for confounders. Use of asthma rescue medications at cohort entry reduced the risk of developing obesity (hazard ratio, 0.57; 95% confidence interval, 0.33-0.96). In addition, the significant association between a history of asthma and an increased risk of developing obesity was replicated in an independent CHS sample.

CONCLUSIONS

Children with asthma may be at higher risk of obesity. Asthma rescue medication use appeared to reduce obesity risk independent of physical activity.

Identification of the genetic determinants for the frequency of regulatory T cells using system genetics

Regulatory T (Treg) cells are indispensable components of immune regulation contributing to the maintenance of respiratory tolerance and preventing autoimmunity and exaggerated immune responses. The frequency and absolute number of Treg cells in lymphoid and non-lymphoid tissues are tightly regulated through incompletely understood mechanisms. In this study, we sought to understand the pulmonary immune regulation through identification of the genetic determinants of the frequency and absolute number of CD4+FOXP3+T cells in mice using a genome-wide association study (GWAS) approach. We quantified the frequency and absolute number of CD4+FOXP3+T cells in the lungs and spleen of 102 inbred strains from the hybrid mouse diversity panel under steady state conditions and after exposure to house dust mite (HDM).

Among strains of mice examined, the absolute number of pulmonary CD4+FOXP3+ T cells varied by 312-fold at the steady state and 210-fold after HDM exposure. A GWAS analysis results revealed several loci that contribute to the regulation of CD4+FOXP3+ T cells in the lungs and spleen of mice, including a locus on chromosome 5 harboring the homeodomain-only protein (Hopx) gene. Characterization of Hopx−/− mice validated the GWAS findings by demonstrating that the frequency and number of CD4+FOXP3+ T cells are higher in the lungs of Hopx−/− compared to WT mice at the steady state and after HDM exposure. We found that in contrast to the lungs, the number of CD4+FOXP3+ T cells is lower in the spleen of Hopx−/− compared to WT mice at the steady state. Our findings suggest that Hopx is a novel genetic determinant of the frequency and number of CD4+FOXP3+ T cells in mice with opposing directional effects in mucosal and secondary lymphoid organs.

Gene Expression Profiling in Blood Provides Reproducible Molecular Insights into Asthma Control

RATIONALE

Maintaining optimal symptom control remains the primary objective of asthma treatment. Better understanding of the biologic underpinnings of asthma control may lead to the development of improved clinical and pharmaceutical approaches.

OBJECTIVES

To identify molecular pathways and interrelated genes whose differential expression was associated with asthma control.

METHODS

We performed gene set enrichment analyses of asthma control in 1,170 adults with asthma, each with gene expression data derived from either whole blood (WB) or unstimulated CD4+ T lymphocytes (CD4), and a self-reported asthma control score representing either the preceding 6 months (chronic) or 7 days (acute). Our study comprised a discovery WB cohort (n = 245, chronic) and three independent, nonoverlapping replication cohorts: a second WB set (n = 448, acute) and two CD4 sets (n = 300, chronic; n = 77, acute).

MEASUREMENTS AND MAIN RESULTS

In the WB discovery cohort, we found significant overrepresentation of genes associated with asthma control in 1,106 gene sets from the Molecular Signatures Database (false discovery rate, <5%). Of these, 583 (53%) replicated in at least one replication cohort (false discovery rate, <25%). Suboptimal control was associated with signatures of eosinophilic and granulocytic inflammatory signals, whereas optimal control signatures were enriched for immature lymphocytic patterns. These signatures included two related biologic processes related to activation by TREM-1 (triggering receptor expressed on myeloid cells 1) and lipopolysaccharide.

CONCLUSIONS

Together, these results demonstrate the existence of specific, reproducible transcriptomic components in blood that vary with degree of asthma control and implicate a novel biologic target (TREM-1).

Prenatal Air Pollution Exposures, DNA Methyl Transferase Genotypes, and Associations with Newborn LINE1 and Alu Methylation and Childhood Blood Pressure and Carotid Intima-Media Thickness in the Children's Health Study

BACKGROUND

Although exposure to ambient air pollutants increases cardiovascular disease risk in adults little is known about the effects of prenatal exposure. Genetic variation and epigenetic alterations are two mechanisms that may influence the effects of early-life exposures on cardiovascular phenotypes.

OBJECTIVES

We investigated whether genetic and epigenetic variation modify associations between prenatal air pollution on markers of cardiovascular risk in childhood.

METHODS

We used linear regression analysis to investigate the associations between prenatal pollutants (PM2.5, PM10, NO2, O3), long interspersed nuclear elements (LINE1) and AluYb8 DNA methylation levels measured in newborn blood spot tests, and carotid intima-media thickness (CIMT) and blood pressure (BP) in 459 participants as part of the Children's Health Study. Interaction terms were also included to test for effect modification of these associations by genetic variation in methylation reprogramming genes.

RESULTS

Prenatal exposure to NO2 in the third trimester of pregnancy was associated with higher systolic BP in 11-year-old children. Prenatal exposure to multiple air pollutants in the first trimester was associated with lower DNA methylation in LINE1, whereas later exposure to O3 was associated with higher LINE1 methylation levels in newborn blood spots. The magnitude of associations with prenatal air pollution varied according to genotype for 11 SNPs within DNA methyltransferase 1 (DNMT1), DNA methyltransferase 3 Beta (DNMT3B), Tet methylcytosine dioxygenase 2 (TET2), and Thymine DNA glycosylase (TDG) genes. Although first-trimester O3 exposure was not associated with CIMT and systolic BP overall, associations within strata of DNMT1 or DNMT3B were observed, and the magnitude and the direction of these associations depended on DNMT1 genotypes.

CONCLUSIONS

Genetic and epigenetic variation in DNA methylation reprogramming genes and in LINE1 retrotransposons may play important roles in downstream cardiovascular consequences of prenatal air pollution exposure. Citation: Breton CV, Yao J, Millstein J, Gao L, Siegmund KD, Mack W, Whitfield-Maxwell L, Lurmann F, Hodis H, Avol E, Gilliland FD. 2016. Prenatal air pollution exposures, DNA methyl transferase genotypes, and associations with newborn LINE1 and Alu methylation and childhood blood pressure and carotid intima-media thickness in the Children's Health Study. Environ Health Perspect 124:1905-1912; http://dx.doi.org/10.1289/EHP181.

Air pollution affects lung cancer survival

RATIONALE

Exposure to ambient air pollutants has been associated with increased lung cancer incidence and mortality, but due to the high case fatality rate, little is known about the impacts of air pollution exposures on survival after diagnosis. This study aimed to determine whether ambient air pollutant exposures are associated with the survival of patients with lung cancer.

METHODS

Participants were 352 053 patients with newly diagnosed lung cancer during 1988-2009 in California, ascertained by the California Cancer Registry. Average residential ambient air pollutant concentrations were estimated for each participant's follow-up period. Cox proportional hazards models were used to estimate HRs relating air pollutant exposures to all-cause mortality overall and stratified by stage (localised only, regional and distant site) and histology (squamous cell carcinoma, adenocarcinoma, small cell carcinoma, large cell carcinoma and others) at diagnosis, adjusting for potential individual and area-level confounders.

RESULTS

Adjusting for histology and other potential confounders, the HRs associated with 1 SD increases in NO2, O3, PM10, PM2.5 for patients with localised stage at diagnosis were 1.30 (95% CI 1.28 to 1.32), 1.04 (95% CI 1.02 to 1.05), 1.26 (95% CI 1.25 to 1.28) and 1.38 (95% CI 1.35 to 1.41), respectively. Adjusted HRs were smaller in later stages and varied by histological type within stage (p<0.01, except O3). The largest associations were for patients with early-stage non-small cell cancers, particularly adenocarcinomas.

CONCLUSIONS

These epidemiological findings support the hypothesis that air pollution exposures after lung cancer diagnosis shorten survival. Future studies should evaluate the impacts of exposure reduction.

Ambient Air Pollution Is Associated With the Severity of Coronary Atherosclerosis and Incident Myocardial Infarction in Patients Undergoing Elective Cardiac Evaluation

Background

The effect of air pollution exposure on atherosclerosis severity or incident clinical events in patients with coronary artery disease is not known.

Methods and Results

We conducted a prospective longitudinal cohort study of 6575 Ohio residents undergoing elective diagnostic coronary angiography. Multinomial regression and Cox proportional hazards models were used to assess the relationship between exposure to fine particulate matter <2.5 μm in diameter (PM_2.5) and nitrogen dioxide on coronary artery disease severity at baseline and risk of myocardial infarction, stroke, or all‐cause mortality over 3 years of follow‐up. Among participants with coronary artery disease, exposure to PM_2.5 levels was associated with increased likelihood of having coronary atherosclerosis that was mild (odds ratio 1.43, 95% CI 1.11–1.83, P=0.005) and severe (odds ratio 1.63, 95% CI 1.26–2.11, P<0.0001), with the effect on severe coronary artery disease being significantly increased compared with mild disease (P_trend=0.03). Exposure to higher PM_2.5 levels was also significantly associated with increased risk of incident myocardial infarction (hazard ratio 1.33, 95% CI 1.02–1.73, P=0.03) but not stroke or all‐cause mortality. The association of PM_2.5 with incident myocardial infarction was not affected after adjustment for Framingham Adult Treatment Panel III (ATP III) risk score or statin therapy. In comparison, there were no significant associations between nitrogen dioxide levels and all‐cause mortality or risk of stroke after adjustment for Framingham ATP III risk score.

Conclusions

Exposure to PM_2.5 increased the likelihood of having severe coronary artery disease and the risk of incident myocardial infarction among patients undergoing elective cardiac evaluation. These results suggest that ambient air pollution exposure may be a modifiable risk factor for risk of myocardial infarction in a highly susceptible patient population.

A prospective and retrospective analysis of smoking behavior changes in ever smokers with high risk for lung cancer from New Mexico and Pennsylvania

Cigarette smoking is the leading preventable cause of death worldwide. The aim of this study is to conduct a prospective and retrospective analysis of smoking behavior changes in the Lovelace Smokers Cohort (LSC) and the Pittsburgh Lung Screening Study cohort (PLuSS). Area under the curve (AUC) for risk models predicting relapse based on demographic, smoking, and relevant clinical variables was 0.93 and 0.79 in LSC and PLuSS, respectively. The models for making a quit attempt had limited prediction ability in both cohorts (AUC≤0.62). We identified an ethnic disparity in adverse smoking behavior change that Hispanic smokers were less likely to make a quit attempt and were more likely to relapse after a quit attempt compared to non-Hispanic Whites. SNPs at 15q25 and 11p14 loci were associated with risk for smoking relapse in the LSC. Rs6495308 at 15q25 has a large difference in minor allele frequency between non-Hispanic Whites and Hispanics (0.46 versus 0.23, P<0.0001) and was associated with risk for ever relapse at same magnitude between the two ethnic groups (OR=1.36, 95% CI=1.10 to 1.67 versus 1.59, 95% CI=1.00 to 2.53, P=0.81). In summary, the risk prediction model established in LSC and PLuSS provided an excellent to outstanding distinguishing for abstainers who will or will not relapse. The ethnic disparity in adverse smoking behavior between Hispanics and non-Hispanic Whites may be at least partially explained by the sequence variants at 15q25 locus that contains multiple nicotine acetylcholine receptors.

Correction: Inducible Nitric Oxide Synthase Promoter Haplotypes and Residential Traffic-Related Air Pollution Jointly Influence Exhaled Nitric Oxide Level in Children

[This corrects the article DOI: 10.1371/journal.pone.0145363.].

Ambient Air Pollutants Have Adverse Effects on Insulin and Glucose Homeostasis in Mexican Americans

OBJECTIVE

Recent studies suggest that air pollution plays a role in type 2 diabetes (T2D) incidence and mortality. The underlying physiological mechanisms have yet to be established. We hypothesized that air pollution adversely affects insulin sensitivity and secretion and serum lipid levels.

RESEARCH DESIGN AND METHODS

Participants were selected from BetaGene (n = 1,023), a study of insulin resistance and pancreatic β-cell function in Mexican Americans. All participants underwent DXA and oral and intravenous glucose tolerance tests and completed dietary and physical activity questionnaires. Ambient air pollutant concentrations (NO2, O3, and PM2.5) for short- and long-term periods were assigned by spatial interpolation (maximum interpolation radius of 50 km) of data from air quality monitors. Traffic-related air pollution from freeways (TRAP) was estimated using the dispersion model as NOx. Variance component models were used to analyze individual and multiple air pollutant associations with metabolic traits.

RESULTS

Short-term (up to 58 days cumulative lagged averages) exposure to PM2.5 was associated with lower insulin sensitivity and HDL-to-LDL cholesterol ratio and higher fasting glucose and insulin, HOMA-IR, total cholesterol, and LDL cholesterol (LDL-C) (all P ≤ 0.036). Annual average PM2.5 was associated with higher fasting glucose, HOMA-IR, and LDL-C (P ≤ 0.043). The effects of short-term PM2.5 exposure on insulin sensitivity were largest among obese participants. No statistically significant associations were found between TRAP and metabolic outcomes.

CONCLUSIONS

Exposure to ambient air pollutants adversely affects glucose tolerance, insulin sensitivity, and blood lipid concentrations. Our findings suggest that ambient air pollutants may contribute to the pathophysiology in the development of T2D and related sequelae.

Traffic-related air pollution and alveolar nitric oxide in southern California children

Mechanisms for the adverse respiratory effects of traffic-related air pollution (TRAP) have yet to be established. We evaluated the acute effects of TRAP exposure on proximal and distal airway inflammation by relating indoor nitric oxide (NO), a marker of TRAP exposure in the indoor microenvironment, to airway and alveolar sources of exhaled nitric oxide (FeNO).FeNO was collected online at four flow rates in 1635 schoolchildren (aged 12-15 years) in southern California (USA) breathing NO-free air. Indoor NO was sampled hourly and linearly interpolated to the time of the FeNO test. Estimated parameters quantifying airway wall diffusivity (DawNO) and flux (J'awNO) and alveolar concentration (CANO) sources of FeNO were related to exposure using linear regression to adjust for potential confounders.We found that TRAP exposure indoors was associated with elevated alveolar NO. A 10 ppb higher indoor NO concentration at the time of the FeNO test was associated with 0.10 ppb higher average CANO (95% CI 0.04-0.16) (equivalent to a 7.1% increase from the mean), 4.0% higher J'awNO (95% CI -2.8-11.3) and 0.2% lower DawNO (95% CI -4.8-4.6).These findings are consistent with an airway response to TRAP exposure that was most marked in the distal airways.

Lifetime prevalence of childhood eczema and the effect of indoor environmental factors: Analysis in Hispanic and non-Hispanic white children

BACKGROUND

The prevalence of eczema varies markedly across the globe. It is unclear whether the geographic variation is due to race and/or ethnic differences, environmental exposures, or genetic factors.

OBJECTIVE

We investigated the effects of ethnicity and environmental exposures on eczema in Hispanic white and non-Hispanic white children who participated in the Southern California Children's Health Study.

METHODS

We performed a cross-sectional study with sociodemographic predictors and environmental exposures among Hispanic white and non-Hispanic white children ages 4-8 years enrolled in the Children's Health Study, 2002-2003.

RESULTS

Eczema prevalence differed by ethnicity: Hispanic whites showed lower prevalence (13.8%) compared with non-Hispanic whites (20.2%), and adjustment for sociodemographic factors did not account for the ethnic difference (odds ratio [OR] 0.79 [95% confidence interval {CI}, 0.65-0.95]). Parental history of allergic disease had a larger effect in Hispanic whites than in non-Hispanic whites (p for interaction = 0.005). High maternal education level (OR 1.46 [95% CI, 1.14-1.87]), parental history of allergic disease (OR 2.21 [95% CI, 1.78-2.76]), and maternal smoking during pregnancy (OR 1.44 [95% CI, 1.06-1.95]) increased the risk of eczema. Indoor environmental factors (e.g., mold, water damage, humidifier use) increased the risk of eczema in non-Hispanic whites independent of a parental history of allergic disease, but, in Hispanic whites, increased risks were observed, primarily in children without a parental history of allergic disease.

CONCLUSION

Hispanic white children in southern California had a lower prevalence of eczema than non-Hispanic whites, and this ethnic difference was not accounted for by sociodemographic differences. The effects of a parental history of allergic disease and indoor environmental exposures on eczema varied by ethnicity, which indicated that the etiology of eczema may differ in Hispanic whites and in non-Hispanic whites.

Genetic Ancestry and Asthma and Rhinitis Occurrence in Hispanic Children: Findings from the Southern California Children's Health Study

Background

Asthma and rhinitis are common childhood health conditions. Being an understudied and rapidly growing population in the US, Hispanic children have a varying risk for these conditions that may result from sociocultural (including acculturative factors), exposure and genetic diversities. Hispanic populations have varying contributions from European, Amerindian and African ancestries. While previous literature separately reported associations between genetic ancestry and acculturation factors with asthma, whether Amerindian ancestry and acculturative factors have independent associations with development of early-life asthma and rhinitis in Hispanic children remains unknown. We hypothesized that genetic ancestry is an important determinant of early-life asthma and rhinitis occurrence in Hispanic children independent of sociodemographic, acculturation and environmental factors.

Methods

Subjects were Hispanic children (5–7 years) who participated in the southern California Children’s Health Study. Data from birth certificates and questionnaire provided information on acculturation, sociodemographic and environmental factors. Genetic ancestries (Amerindian, European, African and Asian) were estimated based on 233 ancestry informative markers. Asthma was defined by parental report of doctor-diagnosed asthma. Rhinitis was defined by parental report of a history of chronic sneezing or runny or blocked nose without a cold or flu. Sample sizes were 1,719 and 1,788 for investigating the role of genetic ancestry on asthma and rhinitis, respectively.

Results

Children had major contributions from Amerindian and European ancestries. After accounting for potential confounders, per 25% increase in Amerindian ancestry was associated with 17.6% (95% confidence interval [CI]: 0.74–0.99) and 13.6% (95% CI: 0.79–0.98) lower odds of asthma and rhinitis, respectively. Acculturation was not associated with either outcome.

Conclusions

Earlier work documented that Hispanic children with significant contribution from African ancestry are at increased asthma risk; however, in Hispanic children who have little contribution from African ancestry, Amerindian ancestry was independently associated with lower odds for development of early-childhood asthma and rhinitis.

Determinants of Children's Exhaled Nitric Oxide: New Insights from Quantile Regression

While the fractional concentration of exhaled nitric oxide (FeNO) has proven useful in asthma research, its exact role in clinical care remains unclear, in part due to unexplained inter-subject heterogeneity. In this study, we assessed the hypothesis that the effects of determinants of the fractional concentration of exhaled nitric oxide (FeNO) vary with differing levels of FeNO. In a population-based cohort of 1542 school children aged 12–15 from the Southern California Children's Health Study, we used quantile regression to investigate if the relationships of asthma, socio-demographic and clinical covariates with FeNO vary across its distribution. Differences in FeNO between children with and without asthma increased steeply as FeNO increased (Estimated asthma effects (in ppb) at selected 20^th, 50^th and 80^th percentiles of FeNO are 2.4, 6.3 and 22.2, respectively) but the difference was steeper with increasing FeNO in boys and in children with active rhinitis (p-values<0.01). Active rhinitis also showed significantly larger effects on FeNO at higher concentrations of FeNO (Estimated active rhinitis effects (in ppb) at selected 20^th, 50^th and 80^th percentiles of FeNO are 2.1, 5.7 and 14.3, respectively). Boys and children of Asian descent had higher FeNO than girls and non-Hispanic whites; these differences were significantly larger in those with higher FeNO (p-values<0.01). In summary, application of quantile regression techniques provides new insights into the determinants of FeNO showing substantially varying effects in those with high versus low concentrations.

Implication of a Chromosome 15q15.2 Locus in Regulating UBR1 and Predisposing Smokers to MGMT Methylation in Lung

O(6)-Methylguanine-DNA methyltransferase (MGMT) is a DNA repair enzyme that protects cells from carcinogenic effects of alkylating agents; however, MGMT is silenced by promoter hypermethylation during carcinogenesis. A single-nucleotide polymorphism (SNP) in an enhancer in the MGMT promoter was previously identified to be highly significantly associated with risk for MGMT methylation in lung cancer and sputum from smokers. To further genetic investigations, a genome-wide association and replication study was conducted in two smoker cohorts to identify novel loci for MGMT methylation in sputum that were independent of the MGMT enhancer polymorphism. Two novel trans-acting loci (15q15.2 and 17q24.3) that were identified acted together with the enhancer SNP to empower risk prediction for MGMT methylation. We found that the predisposition to MGMT methylation arising from the 15q15.2 locus involved regulation of the ubiquitin protein ligase E3 component UBR1. UBR1 attenuation reduced turnover of MGMT protein and increased repair of O6-methylguanine in nitrosomethylurea-treated human bronchial epithelial cells, while also reducing MGMT promoter activity and abolishing MGMT induction. Overall, our results substantiate reduced gene transcription as a major mechanism for predisposition to MGMT methylation in the lungs of smokers, and support the importance of UBR1 in regulating MGMT homeostasis and DNA repair of alkylated DNA adducts in cells.

Exhaled NO: Determinants and Clinical Application in Children With Allergic Airway Disease

Nitric oxide (NO) is endogenously released in the airways, and the fractional concentration of NO in exhaled breath (FeNO) is now recognized as a surrogate marker of eosinophilic airway inflammation that can be measured using a noninvasive technique suitable for young children. Although FeNO levels are affected by several factors, the most important clinical determinants of increased FeNO levels are atopy, asthma, and allergic rhinitis. In addition, air pollution is an environmental determinant of FeNO that may contribute to the high prevalence of allergic disease. In this review, we discuss the mechanism for airway NO production, methods for measuring FeNO, and determinants of FeNO in children, including host and environmental factors such as air pollution. We also discuss the clinical utility of FeNO in children with asthma and allergic rhinitis and further useful directions using FeNO measurement.

Living near a freeway is associated with lower bone mineral density among Mexican Americans

We hypothesized that chronic exposures to traffic combustion products may lower bone mineral density (BMD). We found that proximity to freeways was associated with reduced BMD. Our findings suggest that traffic-related pollution may contribute to the occurrence of osteopenia and osteoporosis.

INTRODUCTION

Adults residing in rural areas have been linked with higher BMD. We aimed to determine if this difference is due in part to air pollution by examining the relationships between traffic metrics and ambient air pollution with total body and pelvic BMD.

METHODS

Mexican American adults (n = 1,175; mean 34 years; 72 % female) who had participated in the BetaGene study of air pollution, obesity, and insulin resistance were included in this analysis. Total body and pelvic BMD were estimated using dual-energy X-ray absorptiometry. Traffic and ambient air pollutant exposures were estimated at residences using location and ambient monitoring data. Variance component models were used to analyze the associations between residential distance to the nearest freeway and ambient air pollutants with BMD.

RESULTS

Residential proximity to a freeway was associated with lower total body BMD (p-trend = 0.01) and pelvic BMD (p-trend = 0.03) after adjustment for age, sex, weight, and height. The adjusted mean total body and pelvic BMD in participants living within 500 m of a freeway were 0.02 and 0.03 g/cm(2) lower than participants living greater than 1,500 m from a freeway. These associations did not differ significantly by age, sex, or obesity status. Results were similar after further adjustment for body fat and weekly physical activity minutes. Ambient air pollutants (NO2, O3, and PM2.5) were not significantly associated with BMD.

CONCLUSIONS

Traffic-related exposures in overweight and obese Mexican Americans may adversely affect BMD. Our findings indicate that long-term exposures to traffic may contribute to the occurrence of osteoporosis and its consequences.

A longitudinal cohort study of body mass index and childhood exposure to secondhand tobacco smoke and air pollution: the Southern California Children's Health Study

BACKGROUND

Childhood body mass index (BMI) and obesity prevalence have been associated with exposure to secondhand smoke (SHS), maternal smoking during pregnancy, and vehicular air pollution. There has been little previous study of joint BMI effects of air pollution and tobacco smoke exposure.

METHODS

Information on exposure to SHS and maternal smoking during pregnancy was collected on 3,318 participants at enrollment into the Southern California Children's Health Study. At study entry at average age of 10 years, residential near-roadway pollution exposure (NRP) was estimated based on a line source dispersion model accounting for traffic volume, proximity, and meteorology. Lifetime exposure to tobacco smoke was assessed by parent questionnaire. Associations with subsequent BMI growth trajectory based on annual measurements and attained BMI at 18 years of age were assessed using a multilevel modeling strategy.

RESULTS

Maternal smoking during pregnancy was associated with estimated BMI growth over 8-year follow-up (0.72 kg/m2 higher; 95% CI: 0.14, 1.31) and attained BMI (1.14 kg/m2 higher; 95% CI: 0.66, 1.62). SHS exposure before enrollment was positively associated with BMI growth (0.81 kg/m2 higher; 95% CI: 0.36, 1.27) and attained BMI (1.23 kg/m2 higher; 95% CI: 0.86, 1.61). Growth and attained BMI increased with more smokers in the home. Compared with children without a history of SHS and NRP below the median, attained BMI was 0.80 kg/m2 higher (95% CI: 0.27, 1.32) with exposure to high NRP without SHS; 0.85 kg/m2 higher (95% CI: 0.43, 1.28) with low NRP and a history of SHS; and 2.15 kg/m2 higher (95% CI: 1.52, 2.77) with high NRP and a history of SHS (interaction p-value 0.007). These results suggest a synergistic effect.

CONCLUSIONS

Our findings strengthen emerging evidence that exposure to tobacco smoke and NRP contribute to development of childhood obesity and suggest that combined exposures may have synergistic effects.

15q12 variants, sputum gene promoter hypermethylation, and lung cancer risk: a GWAS in smokers

BACKGROUND

Lung cancer is the leading cause of cancer-related mortality worldwide. Detection of promoter hypermethylation of tumor suppressor genes in exfoliated cells from the lung provides an assessment of field cancerization that in turn predicts lung cancer. The identification of genetic determinants for this validated cancer biomarker should provide novel insights into mechanisms underlying epigenetic reprogramming during lung carcinogenesis.

METHODS

A genome-wide association study using generalized estimating equations and logistic regression models was conducted in two geographically independent smoker cohorts to identify loci affecting the propensity for cancer-related gene methylation that was assessed by a 12-gene panel interrogated in sputum. All statistical tests were two-sided.

RESULTS

Two single nucleotide polymorphisms (SNPs) at 15q12 (rs73371737 and rs7179575) that drove gene methylation were discovered and replicated with rs73371737 reaching genome-wide significance (P = 3.3×10(-8)). A haplotype carrying risk alleles from the two 15q12 SNPs conferred 57% increased risk for gene methylation (P = 2.5×10(-9)). Rs73371737 reduced GABRB3 expression in lung cells and increased risk for smoking-induced chronic mucous hypersecretion. Furthermore, subjects with variant homozygote of rs73371737 had a two-fold increase in risk for lung cancer (P = .0043). Pathway analysis identified DNA double-strand break repair by homologous recombination (DSBR-HR) as a major pathway affecting susceptibility for gene methylation that was validated by measuring chromatid breaks in lymphocytes challenged by bleomycin.

CONCLUSIONS

A functional 15q12 variant was identified as a risk factor for gene methylation and lung cancer. The associations could be mediated by GABAergic signaling that drives the smoking-induced mucous cell metaplasia. Our findings also substantiate DSBR-HR as a critical pathway driving epigenetic gene silencing.

Chronic effects of air pollution on respiratory health in Southern California children: findings from the Southern California Children's Health Study

Outdoor air pollution is one of the leading contributors to adverse respiratory health outcomes in urban areas around the world. Children are highly sensitive to the adverse effects of air pollution due to their rapidly growing lungs, incomplete immune and metabolic functions, patterns of ventilation and high levels of outdoor activity. The Children's Health Study (CHS) is a continuing series of longitudinal studies that first began in 1993 and has focused on demonstrating the chronic impacts of air pollution on respiratory illnesses from early childhood through adolescence. A large body of evidence from the CHS has documented that exposures to both regional ambient air and traffic-related pollutants are associated with increased asthma prevalence, new-onset asthma, risk of bronchitis and wheezing, deficits of lung function growth, and airway inflammation. These associations may be modulated by key genes involved in oxidative-nitrosative stress pathways via gene-environment interactions. Despite successful efforts to reduce pollution over the past 40 years, air pollution at the current levels still brings many challenges to public health. To further ameliorate adverse health effects attributable to air pollution, many more toxic pollutants may require regulation and control of motor vehicle emissions and other combustion sources may need to be strengthened. Individual interventions based on personal susceptibility may be needed to protect children's health while control measures are being implemented.

Ethnic-specific associations of rare and low-frequency DNA sequence variants with asthma

Common variants at many loci have been robustly associated with asthma but explain little of the overall genetic risk. Here we investigate the role of rare (<1%) and low-frequency (1-5%) variants using the Illumina HumanExome BeadChip array in 4,794 asthma cases, 4,707 non-asthmatic controls and 590 case-parent trios representing European Americans, African Americans/African Caribbeans and Latinos. Our study reveals one low-frequency missense mutation in the GRASP gene that is associated with asthma in the Latino sample (P=4.31 × 10(-6); OR=1.25; MAF=1.21%) and two genes harbouring functional variants that are associated with asthma in a gene-based analysis: GSDMB at the 17q12-21 asthma locus in the Latino and combined samples (P=7.81 × 10(-8) and 4.09 × 10(-8), respectively) and MTHFR in the African ancestry sample (P=1.72 × 10(-6)). Our results suggest that associations with rare and low-frequency variants are ethnic specific and not likely to explain a significant proportion of the 'missing heritability' of asthma.

Genetic ancestry influences asthma susceptibility and lung function among Latinos

BACKGROUND

Childhood asthma prevalence and morbidity varies among Latinos in the United States, with Puerto Ricans having the highest and Mexicans the lowest.

OBJECTIVE

To determine whether genetic ancestry is associated with the odds of asthma among Latinos, and secondarily whether genetic ancestry is associated with lung function among Latino children.

METHODS

We analyzed 5493 Latinos with and without asthma from 3 independent studies. For each participant, we estimated the proportion of African, European, and Native American ancestry using genome-wide data. We tested whether genetic ancestry was associated with the presence of asthma and lung function among subjects with and without asthma. Odds ratios (OR) and effect sizes were assessed for every 20% increase in each ancestry.

RESULTS

Native American ancestry was associated with lower odds of asthma (OR = 0.72, 95% CI: 0.66-0.78, P = 8.0 × 10(-15)), while African ancestry was associated with higher odds of asthma (OR = 1.40, 95% CI: 1.14-1.72, P = .001). These associations were robust to adjustment for covariates related to early life exposures, air pollution, and socioeconomic status. Among children with asthma, African ancestry was associated with lower lung function, including both pre- and post-bronchodilator measures of FEV1 (-77 ± 19 mL; P = 5.8 × 10(-5) and -83 ± 19 mL; P = 1.1 x 10(-5), respectively) and forced vital capacity (-100 ± 21 mL; P = 2.7 × 10(-6) and -107 ± 22 mL; P = 1.0 x 10(-6), respectively).

CONCLUSION

Differences in the proportions of genetic ancestry can partially explain disparities in asthma susceptibility and lung function among Latinos.

Genome-wide interaction studies reveal sex-specific asthma risk alleles

Asthma is a complex disease with sex-specific differences in prevalence. Candidate gene studies have suggested that genotype-by-sex interaction effects on asthma risk exist, but this has not yet been explored at a genome-wide level. We aimed to identify sex-specific asthma risk alleles by performing a genome-wide scan for genotype-by-sex interactions in the ethnically diverse participants in the EVE Asthma Genetics Consortium. We performed male- and female-specific genome-wide association studies in 2653 male asthma cases, 2566 female asthma cases and 3830 non-asthma controls from European American, African American, African Caribbean and Latino populations. Association tests were conducted in each study sample, and the results were combined in ancestry-specific and cross-ancestry meta-analyses. Six sex-specific asthma risk loci had P-values < 1 × 10(-6), of which two were male specific and four were female specific; all were ancestry specific. The most significant sex-specific association in European Americans was at the interferon regulatory factor 1 (IRF1) locus on 5q31.1. We also identify a Latino female-specific association in RAP1GAP2. Both of these loci included single-nucleotide polymorphisms that are known expression quantitative trait loci and have been associated with asthma in independent studies. The IRF1 locus is a strong candidate region for male-specific asthma susceptibility due to the association and validation we demonstrate here, the known role of IRF1 in asthma-relevant immune pathways and prior reports of sex-specific differences in interferon responses.

Abstract LB-261: Atopic allergic conditions and colorectal cancer risk in the Multiethnic Cohort

Previous studies have provided suggestive evidence of an inverse association between atopic allergic conditions (AAC) and colorectal cancer (CRC) incidence and mortality in predominantly White populations. Here we examined the association between AAC and CRC among White, African American, Native Hawaiian, Japanese American, and Latino men and women in the Multiethnic Cohort (MEC). AAC exposure status was ascertained via self-reported physician diagnosis using a baseline 26-page validated questionnaire. The analysis included 4259 incident CRC cases and 1221 CRC-related deaths ascertained between 1993 and 2010. We also examined associations by ethnic group, location, and stage of cancer as well as potential effect modification by CRC risk factors. AAC was associated with a reduced risk of colorectal cancer incidence among both men and women (RR = 0.85, 95% CI 0.79, 0.91, p &lt; 0.0001). The reduction in risk was noted in each population and was significant in Whites (RR = 0.84, 95% CI 0.71, 0.98, p = 0.03), African Americans (RR = 0.81, 95% CI 0.69, 0.95, p = 0.01), and Japanese Americans (RR = 0.85, 95% CI 0.75, 0.97, p = 0.01). Suggestive evidence of effect modification was noted by smoking (p = 0.07) and aspirin use (p = 0.08), with a greater protective effect observed among current smokers (RR = 0.72, 95% CI 0.58, 0.89, p = 0.002) and never users of aspirin (RR = 0.81, 95% CI 0.73, 0.89, p &lt; 0.0001). Individuals with AAC also had a 19% reduction in CRC-related mortality (P = 0.004). Colonoscopy screening is unlikely to explain these inverse associations, as individuals with AAC were more likely to be screened than those without AAC (p &lt; 0.003 for all ethnic groups). These findings provide support for an association between immune pathology and colorectal cancer, potentially through modulation of the immune system's IgE-mediated pathways systemically and within the gut.

Citation Format: Neal A. Tambe, Dan O. Stram, Lynne R. Wilkens, Peggy Wan, Frank D. Gilliland, Brian E. Henderson, Loic Le Marchand, Christopher A. Haiman. Atopic allergic conditions and colorectal cancer risk in the Multiethnic Cohort. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr LB-261. doi:10.1158/1538-7445.AM2014-LB-261

Fraction of exhaled nitric oxide values in childhood are associated with 17q11.2-q12 and 17q12-q21 variants

BACKGROUND

The fraction of exhaled nitric oxide (Feno) value is a biomarker of eosinophilic airway inflammation and is associated with childhood asthma. Identification of common genetic variants associated with childhood Feno values might help to define biological mechanisms related to specific asthma phenotypes.

OBJECTIVE

We sought to identify the genetic variants associated with childhood Feno values and their relation with asthma.

METHODS

Feno values were measured in children age 5 to 15 years. In 14 genome-wide association studies (N = 8,858), we examined the associations of approximately 2.5 million single nucleotide polymorphisms (SNPs) with Feno values. Subsequently, we assessed whether significant SNPs were expression quantitative trait loci in genome-wide expression data sets of lymphoblastoid cell lines (n = 1,830) and were related to asthma in a previously published genome-wide association data set (cases, n = 10,365; control subjects: n = 16,110).

RESULTS

We identified 3 SNPs associated with Feno values: rs3751972 in LYR motif containing 9 (LYRM9; P = 1.97 × 10(-10)) and rs944722 in inducible nitric oxide synthase 2 (NOS2; P = 1.28 × 10(-9)), both of which are located at 17q11.2-q12, and rs8069176 near gasdermin B (GSDMB; P = 1.88 × 10(-8)) at 17q12-q21. We found a cis expression quantitative trait locus for the transcript soluble galactoside-binding lectin 9 (LGALS9) that is in linkage disequilibrium with rs944722. rs8069176 was associated with GSDMB and ORM1-like 3 (ORMDL3) expression. rs8069176 at 17q12-q21, but not rs3751972 and rs944722 at 17q11.2-q12, were associated with physician-diagnosed asthma.

CONCLUSION

This study identified 3 variants associated with Feno values, explaining 0.95% of the variance. Identification of functional SNPs and haplotypes in these regions might provide novel insight into the regulation of Feno values. This study highlights that both shared and distinct genetic factors affect Feno values and childhood asthma.