Genetic association between common beta-2 adrenoreceptor polymorphism and asthma severity in school-age children

Abstract

Recent studies have suggested that polymorphism of the beta-2 adrenergic receptor (β2AR) gene at codon 16 affect an individual’s airway responsiveness. This study aimed to evaluate the association between beta-2 adrenoreceptor genotypes at position 16 and asthma severity among 59 school-aged children. They were divided into two groups: control group including 19 healthy children and 40 asthmatic children as the study group. The study group was also divided into 20 mild asthmatic children and the remaining 20 patients suffered from severe asthma. Blood samples were collected from Chest Department, Pediatrics Hospital, Ain Shams University, from February 2008 to March 2009. Molecular analysis was performed at Science Faculty, Ain Shams University, Cairo, Egypt. Venous blood sample were collected and genotyping of β2AR gene polymorphism at position 16 was identified by polymerase chain reaction– restriction fragment length polymorphism analysis, using the NcoI restriction enzyme. We found a highly statistically significant difference of polymorphisms’ distribution of β2AR gene at codon 16 among asthmatic patients and control subjects (χ²= 11.904; P = 0.0026), also among severe asthmatics and mild/moderate asthmatics(χ² =10.108;P=0.0064). There was a strong association of heterozygous Arg16Gly of b2AR with severe asthmatics rather than that in control subjects (70% vs. 5.3%, P < 0.001), with odd ratio (OR) 42 (95% confidence interval (CI): 4.520–390.297), the highest OR in heterozygous Arg16Gly (42) suggests a dominant mode of action of the heterozygous Arg16Gly in development of asthma severity. So, we concluded that heterozygous Arg16Gly of b2AR gene appeared to be an important genetic factor in the expression of asthma severity.

Keywords: Asthma; Beta-2 adrenoceptor gene polymorphisms; Arginine 16/Glycine