Beta 2 adrenergic receptor polymorphisms, at codons 16 and 27, and bronchodilator responses in adult Venezuelan...

One of the gene polymorphisms often studied in asthmatic patients is the β2 adrenergic receptor (ADRβ2). Even though in the Venezuelan Mestizo population there is a high incidence of asthma, there are no direct reports of ADRβ2 gene polymorphism, and treatment response. The aim of this study was to assess, in this population, the gene frequency of ADRβ2 polymorphisms at codons 16 Arg/Gly and 27 Gln/Glu, allergen sensitization, and its relationship to bronchodilator response.

Purified genomic DNA was obtained form 105 Mestizo asthmatic and 100 Mestizo healthy individuals from Venezuela. The two polymorphisms were assessed by PCR-RFLP. Patient sensitization to aeroallergens and their response to bronchodilatation were correlated.

Significant differences between patients and controls were recorded in: 1) the prevalence of Arg/Arg at codon 16 (28.6% in patients vs. 47% in controls, P<0.01), 2) the frequency of heterozygotes Arg/Gly (55% in patients vs. 35% in controls, P<0.01). Conversely, no differences in polymorphism frequencies were found at codon 27. The haplotypes Arg/Gly-Gln/Gln were more common in patients than controls (P <0.01), whereas the Arg/Arg-Gln/Glu combination prevailed in the control group (P<0.01). The Arg/Gly and Gln/Glu genotypes were associated with better responses after salbutamol. The asthmatic homozygotes Arg/Arg have higher sensitivity to aeroallergens.

The difference in Arg/Arg frequency between groups suggests that this could be a protective genotype although the asthmatic group had a higher sensitivity to aeroallergens. The asthmatic heterozygotes had better bronchodilator responses than the homozygotes.