title: Polymorphism of the ADRB2 gene and response to inhaled beta- agonists in children with asthma: a meta-analysis.
abstract: BACKGROUND
  About 9% of children have asthma, corresponding to almost 6.8 million children in the USA and 1.1 million in the UK. Asthma exacerbations are the leading cause of pediatric emergency room visits and impose a large burden on the individual, family, and society. There is mounting evidence that therapeutic failure of inhaled beta-agonists is associated with polymorphisms of the beta(2)-adrenergic receptor gene (ADRB2); specifically, mutations leading to amino acid changes at positions 16 and 27, which alter down-regulation of the beta(2)-adrenergic receptor (beta(2)AR), induce resistance to the smooth-muscle relaxing effect of beta(2)-adrenergic agonists.
  
  
  METHODS
  We conducted a meta-analysis to examine the association between ADRB2 polymorphisms and the response to inhaled beta(2)-adrenergic agonists in children with asthma. We included all published studies until November 2008, in which asthmatic children underwent testing for acute bronchodilator response, defined as > or = 15% improvement in forced expiratory volume in 1 second (FEV(1)) and single nucleotide polymorphism (SNP) genotyping for positions 16 and/or 27 of the beta(2)AR. Individual and summary odds ratios were calculated using a random effects model.
  
  
  RESULTS
  We identified three case-control or family-based studies involving 960 asthmatic children (692 children with negative beta(2)-bronchodilator response, defined as < 15% improvement in FEV(1) and 268 children with positive bronchodilator response). We found a significant association between favorable therapeutic response to inhaled beta(2)-adrenergic agonists in asthmatic children and the Arg/Arg phenotype at position 16 of the beta(2)AR [OR = 1.77; 95% CI (1.01; 3.1); p = 0.029], compared with the Arg/Gly or Gly/Gly phenotypes. The beneficial effect of Arg at position 16 of the beta(2)AR was most pronounced in African-American asthmatic children [OR = 3.54; 95% CI (1.37, 9.13)]. There was no association between clinical response to beta(2)-agonists and polymorphism at amino acid position 27 of the beta(2)AR (OR = 1.04; 95% CI [0.76,1.42]).
  
  
  CONCLUSIONS
  Failure of bronchodilator response to inhaled beta-agonists in asthmatic children is associated with the Gly allele (Arg/Gly and Gly/Gly genotypes) at position 16 of the beta(2)-adrenergic receptor. Genetic typing for beta(2)AR polymorphism may help identify children with drug-resistant asthma.
authors.affiliation: Clinical Pharmacology Unit, and Division of Emergency Medicine, Boston Children's Hospital, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, USA. yaron.finkelstein@childrens.harvard.edu
authors.forename: Yaron
authors.initials: Y
authors.lastname: Finkelstein
authors.forename: Facundo Garcia
authors.initials: FG
authors.lastname: Bournissen
authors.forename: Janine R
authors.initials: JR
authors.lastname: Hutson
authors.forename: Michael
authors.initials: M
authors.lastname: Shannon
mesh_terms: D058666:Adrenergic beta-2 Receptor Agonists; D000318:Adrenergic beta-Agonists / Q000627:therapeutic use*; D001741:Black or African American / Q000235:genetics; D001120:Arginine / Q000235:genetics; D001249:Asthma / Q000188:drug therapy*; D002648:Child; D004351:Drug Resistance / Q000235:genetics*; D005838:Genotype; D005998:Glycine / Q000235:genetics; D006630:Hispanic or Latino / Q000235:genetics; D006801:Humans; D016017:Odds Ratio; D020641:Polymorphism, Single Nucleotide / Q000235:genetics*; D018343:Receptors, Adrenergic, beta-2 / Q000235:genetics*; D044465:White People / Q000235:genetics
chemical_list: D058666:Adrenergic beta-2 Receptor Agonists; D000318:Adrenergic beta-Agonists; D018343:Receptors, Adrenergic, beta-2; D001120:Arginine; D005998:Glycine