β2-adrenergic receptor gene polymorphisms in normal and asthmatic individuals in the Eastern Province of Saudi Arabia

BACKGROUND AND OBJECTIVES: Several polymorphisms of the β2-adrenergic receptor (β2-AR) gene have been identified, including the amino acid substitution from arginine (Arg) to glycine (Gly) at codon 16 and from glutamine (Gln) to glutamic acid (Glu) at codon 27. These substitutions affect receptor function and show significantly more agonist-promoted receptor down-regulation than cells expressing the Arg 16/Gln 27 variants. Although the ethnic dependency of this polymorphism has been described in other populations, no studies investigating its relationship to asthma have been conducted in the Saudi population . Therefore, our main objective was to determine the prevalence of these two mutations among patients with asthma in the Eastern Province and in matched healthy controls. DESIGN AND SETTING: A case-control study conducted at a university hospital among Saudi patients PATIENTS AND METHODS: Blood samples were collected from 73 asthmatic patients and from 85 controls, and the β2-AR gene polymorphisms at codon 16 and codon 27 were assessed by restriction fragment length polymorphism. RESULTS: Although a significant difference was observed in genotype frequencies at codon 16 (Arg/Gly) between the asthmatic and normal control subjects (P<.05), no statistically significant difference was observed in allele frequencies between the two groups. In addition, no statistically significant differences were observed in genotype and allele frequencies at codon 27 (Gln/Glu) between the normal (control) and asthmatic groups (β2=0.75, P>.68). Using the THESIAS statistical program, no significant association of any haplotype with asthma was found. CONCLUSIONS: Our findings indicate a poor association of individual single-nucleotide polymorphisms with asthma. However, further study is required to ascertain the interactions of different haplotypes and the response of patients with different haplotypes to various treatments.