Background and objectives:: Several mechanisms have been suggested to explain the association between asthma and obesity, one of them is the presence of common genetic predictors as β2 adrenergic receptor gene polymorphism. To test this suggestion, the present study was carried out.Subjects: 60 asthmatic patients (50 females and10 males) and 60 normal subjects (46 females and 14 males) were included in this study. Methodology: measurement of body weight and height, waist circumference and waist to hip ratio. Asthma severity was assessed by disease severity score. Pulmonary function tests and bronchial reactivity by methacholine inhalation challenge (PD20-FEV1) were performed and DNA extraction, Polymerase chain reaction (PCR)and restriction digestion was performed at codons 16 and 27of β2AR to determine β2 adrenergic receptor gene polymorphism. Results: No significant difference was detected between the asthmatic and control subjects as regards allelic or genotype frequencies of β2AR gene at codon 16 and codon 27 and no significant difference was found as regards genotype frequencies of β2AR gene at codon 16 and codon 27 between obese and non-obese asthmatics. A significantly increased frequency of Gly/Gly at codon 16 was found among severe asthmatics in comparison with mild and moderate asthmatics. A significantly higher frequency of genotype Glu/Glu at codon 27 was detected among obese subjects when compared to non-obese subjects. There was a significant difference in FEV1% predicted and in FEF25-75% predicted in non- obese asthmatics when distributed according to genotypes at codon 16. No significant difference in the distribution of the asthmatics according to the value of PD20-FEV1 among genotypes of B2AR gene at codon 16, codon 27 was found.
Conclusion: Arg16Arg was found to be protective from development of severe asthmaGlu27Gluwassignificantly associated with obesity. However, there was no detectable specific genotype for the association of asthma and obesity.