The association of overweight with allergy and asthma in children: findings from the National Health and Nutrition Examination Survey (NHANES) 1999-2006

Obesity and asthma prevalence have both risen among children over the last several decades, and research efforts increasingly suggest that obesity is associated with asthma. Atopy is a strong risk factor for asthma, but previous literature on the relationship between obesity and atopy has been inconsistent. In addition, some, but not all, studies have shown that the effect of obesity on asthma is stronger among non-atopic individuals than among those with atopy. Systemic inflammation may be a factor in the relationship between obesity and asthma. Breastfeeding may potentially protect against obesity, atopy, and asthma. This dissertation used National Health and Nutrition Examination and Survey (NHANES) data from 1999-2006 to examine the relationship between obesity and asthma among U.S. children age 2-19. Data from 2005-2006, which include assays for total and allergen-specific IgE, were used to explore the relationship of obesity with IgE levels, atopy, and allergy symptoms, and also to stratify the obesity-asthma analysis by atopic status. The protective effect of breastfeeding was investigated using data for children age 1-6. Obese children were more likely to report having current asthma than children of normal weight (OR: 1.68, 95% CI: 1.33, 2.12). The association did not differ by gender, but was stronger among non-atopic children than among children with at least 1 positive specific IgE result (OR: 2.46, 95% CI: 1.21, 5.02 vs. OR: 1.34, 95% CI: 0.70, 2.57; interaction p-value 0.09). Total IgE levels increased with BMI in a dose response manner and the odds of having at least one positive specific IgE were elevated among obese children compared to normal weight children (OR: 1.35; 95% CI: 1.04-1.76). C-reactive protein levels were associated with both atopy and asthma, and may indicate a role for systemic inflammation for both outcomes. Breastfeeding was found to protect against obesity and asthma, but not atopy. The protective effect of breastfeeding against asthma was not modified by obesity or by atopy. An increased risk of allergic disease and asthma may not be the most consequential health risk faced by overweight children. Nonetheless, it provides additional motivation for undertaking the difficult challenge to reduce childhood obesity

Standardization and performance evaluation of mononuclear cell cytokine secretion assays in a multicenter study

BACKGROUND: Cryopreservation of peripheral blood mononuclear cells has been used to preserve and standardize immunologic measurements for multicenter studies, however, effects of cryopreservation on cytokine responses are incompletely understood. In designing immunologic studies for a new multicenter birth cohort study of childhood asthma, we performed a series of experiments to determine the effects of two different methods of cryopreservation on the cytokine responses of cord and peripheral blood mononuclear cells. RESULTS: Paired samples of PBMC were processed freshly, or after cryopreservation in a Nalgene container (NC) or a controlled-rate freezer (CRF). Although there were some differences between the methods, cryopreservation inhibited PHA-induced IL-10 secretion and Der f 1-induced IL-2 secretion, and augmented PHA-induced IL-2 secretion and spontaneous secretion of TNF-α. In separate experiments, NC cryopreservation inhibited secretion of several cytokines (IL-13, IL-10, IFN-γ, TNF-α) by PHA-stimulated cord blood mononuclear cells. With the exception of PHA-induced IL-13, results from fresh and cryopreserved cord blood samples were not significantly correlated. Finally, in reproducibility studies involving processing of identical cell samples in up to 4 separate laboratories, variances in cytokine responses of fresh cells stimulated at separate sites did not exceed those in cryopreserved cells stimulated at a central site. CONCLUSION: Collectively, these studies indicate that cryopreservation can affect mononuclear cell cytokine response profiles, and that IL-10 secretion and antigen-induced responses may be especially vulnerable. These studies also demonstrate that mononuclear cell responses can be standardized for performance in a small number of laboratories for multicenter studies, and underscore the importance of measuring reproducibility and of testing whether cryopreservation techniques alter specific immunologic outcomes

Longitudinal data reveal strong genetic and weak non-genetic components of ethnicity-dependent blood DNA methylation levels

Epigenetic architecture is influenced by genetic and environmental factors, but little is known about their relative contributions or longitudinal dynamics. Here, we studied DNA methylation (DNAm) at over 750,000 CpG sites in mononuclear blood cells collected at birth and age 7 from 196 children of primarily self-reported Black and Hispanic ethnicities to study race-associated DNAm patterns. We developed a novel Bayesian method for high-dimensional longitudinal data and showed that race-associated DNAm patterns at birth and age 7 are nearly identical. Additionally, we estimated that up to 51% of all self-reported race-associated CpGs had race-dependent DNAm levels that were mediated through local genotype and, quite surprisingly, found that genetic factors explained an overwhelming majority of the variation in DNAm levels at other, previously identified, environmentally-associated CpGs. These results indicate that race-associated blood DNAm patterns in particular, and blood DNAm levels in general, are primarily driven by genetic factors, and are not as sensitive to environmental exposures as previously suggested, at least during the first 7 years of life

Association of Childhood Obesity With Atopic and Nonatopic Asthma: Results From the National Health and Nutrition Examination Survey 1999–2006

Obesity and asthma prevalence have both risen among children over the last several decades, and research efforts increasingly suggest that obesity is associated with asthma. Some, but not all, studies have shown that the effect of obesity on asthma is stronger among non-atopic individuals than among those with atopy. Systemic inflammation may be a factor in this relationship

Association of Obesity with IgE and Allergy Symptoms in Children and Adolescents: Results from NHANES 2005–2006

The prevalence of both obesity and allergic disease has increased among children over the last several decades. Previous literature on the relationship between obesity and allergic disease has been inconsistent. It is not known whether systemic inflammation could be a factor in this relationship

The Pediatric Asthma Risk Score: A New Gold Standard for Asthma Prediction

Rationale: Early prediction of asthma is critical to identify potential primary prevention strategies. The Pediatric Asthma Risk Score (PARS) is a continuous score to predict early-life asthma but was developed and validated in relatively homogenous populations. We compared PARS directly to the Asthma Predictive Index (API) and validated in 10 cohorts with varying race, ethnicity, sex, cohort type, missing data and birth decades, and perform a meta-analysis across all 10 cohorts. Methods: We utilized data from 5674 children participating in the Children’s Respiratory and Environmental Workgroup. We applied both PARS and the API in each cohort, as well as harmonized across all cohorts, and directly compared the ability of each tool to predict asthma development at ages 5-10. Results: The PARS area under the curve (AUC) was significantly higher than the AUC of the API in 9 cohorts (p-value range 0.01 - \u3c0.001). The PARS AUC did not differ by cohort type (high risk or general population), decade of enrollment, race, sex, ethnicity, missing PARS factors or polysensitization definition (skin prick test vs. specific IgE). The weights of the 6 PARS factors in the meta-analysis were very similar to the original weights, validating the original PARS scoring. Conclusions: This multi-cohort study makes the PARS the most validated model of asthma prediction in children to date, not only with respect to the number of cohorts used but also with regards to capturing the diversity of asthma in the United States. Future studies may consider PARS the new gold standard in pediatric asthma risk prediction

Distinct Airway Inflammatory Pathways Associated with Asthma Exacerbations are Modulated by Mepolizumab Therapy in Children

Rationale: Identification of specific airway inflammatory pathways can lead to effective personalized treatment with biologics in asthma and insights to mechanisms of action. Methods: 290 urban children with exacerbation-prone asthma and ≥150/mm3 blood eosinophils were randomized (1:1) to placebo or mepolizumab added to guideline-based care. Nasal lavage samples were collected at randomization and during treatment for RNA-sequencing, and analyzed by cell-deconvolution modular analysis to assess genome-wide expression patterns associated with exacerbation number and effect of treatment. Results: Mepolizumab significantly reduced the frequency of exacerbations compared to placebo. At randomization, there were no differences in expression between treatment groups; multiple modules were subsequently differentially expressed during mepolizumab but not placebo treatment. Furthermore, expression levels of multiple modules were associated with the exacerbation number during the study, with distinct relationships observed in the placebo and/or mepolizumab groups. Notably, higher expression at randomization of an eosinophil-associated module enriched for Type-2 genes including IL4, IL5, and IL13, was associated with increased exacerbations in placebo (β=0.19, p\u3c0.001), but not mepolizumab-treated children (interaction p\u3c0.01). Furthermore, mepolizumab treatment reduced expression of this module (Fold-change=0.62, p\u3c0.001). In contrast, higher expression at randomization of an eosinophil-associated module enriched for eosinophil activation (e.g. CD9) and mucus hypersecretion (e.g. MUC5AC) genes was associated with exacerbation number in both groups throughout the study (β=0.18, p\u3c0.01) and was unaltered by mepolizumab therapy. Conclusions: Multiple distinct airway inflammation patterns were identified associated with exacerbation frequency. These findings identify inflammatory endotypes and indicate likelihood and potential mechanisms of a beneficial clinical response to mepolizumab therapy to prevent exacerbations

The Effect of Subcutaneous German Cockroach Immunotherapy (SCIT) on Nasal Allergen Challenge (NAC) and Cockroach-specific Antibody Responses Among Urban Children and Adolescents

Rationale: Cockroach allergy contributes to asthma and rhinitis morbidity among many urban children. Treatment with cockroach SCIT could be beneficial. Methods: 8-17 year-old children with mild-moderate asthma from 11 urban sites participated in a randomized double-blind placebo-controlled SCIT trial using non-standardized, glycerinated German cockroach extract. Positive cockroach skin tests, cockroach-specific IgE, and nasal challenge response with total nasal symptom scores (TNSS) ≥6 or maximal sneeze scores of 3 during a graded NAC were required for enrollment. Following dose escalation, 0.4 ml of undiluted extract was targeted for maintenance dosing (∼7 mcg Bla g2/dose). The primary endpoint was change in NAC-induced mean TNSS from baseline to one year post randomization. Changes in cockroach-specific IgE (CRsIgE) and IgG4 (CRsIgG4) were also analyzed. Results: Mean TNSS did not significantly change from baseline in either group (placebo n=29, SCIT n=28). There was no significant difference in the change in mean TNSS between placebo and SCIT [−0.79±0.35 vs. −1.02±0.37, respectively, difference=0.2(−1.15, 0.70), p=0.63]. Baseline CRsIgE and CRsIgG4 didn’t differ between groups. Mean CRsIgE decreased in both groups following treatment: 3.6 to 2.3 kU/L (0.64 fold change), p=0.015 and 8.3 to 4.2 kU/L (0.51 fold change), p\u3c0.001 in placebo and SCIT respectively, but did not differ between groups [p=0.33]. Significant increases in CRsIgG4 post-treatment were observed among SCIT recipients only: 0.07 to 12.3 mg/L (176 fold change), p\u3c0.001. Conclusions: Cockroach SCIT increased CRsIgG4 levels but did not significantly alter NAC-induced TNSS responses. The extent to which NAC in these children may reflect clinical efficacy for rhinitis or asthma is uncertain

Multi-omic association study identifies DNA methylation-mediated genotype and smoking exposure effects on lung function in children living in urban settings

Impaired lung function in early life is associated with the subsequent development of chronic respiratory disease. Most genetic associations with lung function have been identified in adults of European descent and therefore may not represent those most relevant to pediatric populations and populations of different ancestries. In this study, we performed genome-wide association analyses of lung function in a multiethnic cohort of children (n = 1,035) living in low-income urban neighborhoods. We identified one novel locus at the TDRD9 gene in chromosome 14q32.33 associated with percent predicted forced expiratory volume in one second (FEV1) (p = 2.4x10-9; βz = -0.31, 95% CI = -0.41- -0.21). Mendelian randomization and mediation analyses revealed that this genetic effect on FEV1 was partially mediated by DNA methylation levels at this locus in airway epithelial cells, which were also associated with environmental tobacco smoke exposure (p = 0.015). Promoter-enhancer interactions in airway epithelial cells revealed chromatin interaction loops between FEV1-associated variants in TDRD9 and the promoter region of the PPP1R13B gene, a stimulator of p53-mediated apoptosis. Expression of PPP1R13B in airway epithelial cells was significantly associated the FEV1 risk alleles (p = 1.3x10-5; β = 0.12, 95% CI = 0.06–0.17). These combined results highlight a potential novel mechanism for reduced lung function in urban youth resulting from both genetics and smoking exposure

A distributed geospatial approach to describe community characteristics for multisite studies

Understanding place-based contributors to health requires geographically and culturally diverse study populations, but sharing location data is a significant challenge to multisite studies. Here, we describe a standardized and reproducible method to perform geospatial analyses for multisite studies. Using census tract-level information, we created software for geocoding and geospatial data linkage that was distributed to a consortium of birth cohorts located throughout the USA. Individual sites performed geospatial linkages and returned tract-level information for 8810 children to a central site for analyses. Our generalizable approach demonstrates the feasibility of geospatial analyses across study sites to promote collaborative translational research