Objective: To investigate the relationship between the polymorphism of beta 2 adrenergic receptor (beta 2 AR) at loci 16, 27 and the nocturnal asthma phenotype.
Methods: Forty-nine asthmatic patients were divided into nocturnal asthmatic group (n = 25) and non-nocturnal asthmatic group(n = 24) by their peak expiratory flow rates (PEFR). The genotypes at loci 16, 27 of beta 2 AR were delineated by PCR product sequencing. Then the relationships of beta 2 AR genotypes with the PEFR, FEV1 and the situation of drug use in the two groups were analyzed.
Results: By the criteria of overnight decrements in PEFR, the nocturnal asthma group had a mean overnight decrement in PEFR of 33.6%, compared to 7.0% for the non-nocturnal asthma group (P < 0.001). The mean values of daytime baseline percent predicted forced expiratory volume in 1 s (FEV1) were 73.7% and 85.8% for the nocturnal and non-nocturnal cohorts, respectively (P < 0.001). The frequency of the Gly16 allele was 56.0% in the nocturnal group, compared to 22.9% in the non-nocturnal group (P < 0.05). The results from comparison of the two cohorts as to homozygosity for Gly16, homozygosity for Arg16, or heterozygosity were also consistent with the segregation of Gly16 with nocturnal asthma. There was no significant difference in the frequency of polymorphisms at locus 27 (Gln27 or Glu27).
Conclusion: The Gly16 polymorphism of beta 2 AR appears to be associated with nocturnal asthma.