Obesity-associated asthma is a distinct entity characterized by increased lower airway obstruction and suboptimal response to conventional asthma management that disproportionately affects urban children. However, its pathogenesis is poorly understood. In contrast to atopic T helper (Th) type 2 inflammation found in classic childhood asthma, studies from our lab indicate that obesity-associated asthma in Hispanic and African American children is associated with non-atopic Th1 inflammation that correlates with lower airway obstruction. Additionally, our findings of decreased promoter methylation of genes associated with T cell signaling suggest that epigenetic mechanisms may, in part, mediate the distinct asthma phenotype observed in obese children. However, molecular mechanisms that underlie non-atopic inflammation in obese asthmatics are not known. Asthma and obesity are multifactorial diseases, determined by genetic susceptibility, including that related to ancestry, epigenetic modification by environmental exposures and non-genetic environmental factors that influence gene expression and thus clinical phenotype. Hence, investigation of the association between gene expression, genetic polymorphisms, and epigenetic modulation may identify a unifying molecular mechanism to explain the obese asthma phenotype observed in urban children. Situated in the Bronx where the prevalence of childhood asthma and obesity are twice the national average, we are uniquely positioned to study these associations and investigate the role of the genome and epigenome in mediating the effect of obesity on the asthma phenotype. We hypothesize that Th-cell gene expression in obese asthmatics differs from that in normal-weight asthmatics, is determined by genetic polymorphisms (eQTLs and ancestry-specific haplotypes), and is influenced by DNA methylation. We propose the following specific aims to address these hypotheses: (1) To quantify Th-cell gene expression differences between obese asthmatic and normal- weight asthmatic children. (2) To determine if epigenetic mechanisms mediate the effect of obesity on asthma. (3) To investigate if genetic polymorphisms, including ancestry-specific haplotypes, determine susceptibility to obesity-associated asthma. We will isolate Th cells from 100 obese asthmatic and 100 normal-weight asthmatic children matched for age and gender. We will simultaneously conduct genome-wide assays of a) gene expression by Directional Transcriptome Sequencing (RNA-seq) b) DNA methylation by HELP-tagging and c) genetic polymorphisms and single nucleotide polymorphisms (SNPs) informative of ancestry by array-based genotyping on these cells. Study of gene expression and DNA methylation will identify mechanistic molecular pathways specific to the obese asthma phenotype and improve our understanding of the disease pathogenesis. We will identify key molecules associated with non-atopic inflammation that could be novel targets for therapeutic intervention. Links between expression and methylation will elucidate the role of environmental exposures. Association of gene expression with genetic polymorphisms will identify variants predicting genetic susceptibility, which may be used to screen at-risk individuals. Together, our study will provide fundamental insights into the pathogenesis of obesity-associated asthma among high-risk ethnicities. As a pediatric pulmonologist, my goal is to become an independent translational investigator in the field of pediatric asthma with a focus on the pulmonary effects of obesity. My current objective is to obtain the K23 Mentored Patient Oriented-Research Career Development Award that will allow an in-depth study of genetic and epigenetic factors influencing Th cell mediated inflammation in obese asthmatic minority children. Findings from this proposal will lay the foundation for an R01 application, which may focus on a) validation of the key differentially expressed and/or methylated molecules in a separate cohort of children with poorly controlled disease b) confirmation of the role of key molecules in in-vitro cell culture systems with molecule-specific inhibitors and/or methylation modulators c) a prospective investigation into links between obesity onset, rapidity of weight gain, development of asthma and Th cell differentiation, given the young age at which obesity- associated asthma afflicts urban children. The combination of my mentoring team including established researchers in the field of epigenomics, obesity-related diseases, T cell biology, asthma and mucosal and systemic immunity, extensive available resources at Einstein, including the Center of Epigenomics, and our patient population provides an ideal environment to conduct this research and achieve my goals. The career development plan proposed in this application incorporates mentorship in translational epigenetic research, coursework in genetics and epigenomics, hand on training in novel methods to investigate gene expression, genotyping and DNA methylation, and participation and presentation at local, regional and national meetings. Together, the research proposed in this K23 award will lay the foundation for my development into an independent investigator in the field of pediatric obesity-associated asthma.
Obese asthmatics have increased asthma severity and suboptimal response to conventional asthma management, likely due to a non-allergic pattern of T cell inflammation that differs from allergic inflammation found in normal-weight asthmatics. However, the molecular mechanisms associated with non-allergic inflammation are not known. Our proposed studies will investigate T cell gene expression and its genetic, including ethnicity, and epigenetic determinants to identify key molecules and associated molecular pathways specific to inflammation observed in obesity-associated asthma. While key molecules and pathways will identify novel targets for therapeutic interventions and improve our understanding of mechanisms linked to obesity-associated asthma, the genetic variants may be used to screen high-risk individuals.
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