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 Table of Contents  
ORIGINAL ARTICLE
Year : 2021  |  Volume : 5  |  Issue : 2  |  Page : 161-165

The effect of 16 Arg/Gly β2–adrenergic receptors gene polymorphism on pulmonary function in asthmatic children treated with nebulized salbutamol


1 Department of Pharmacology, College of Pharmacy, University of Karbala, Karbala, Iraq
2 College of Medicine, University of Karbala, Karbala, Iraq
3 Department of Pharmacology, Karbala Teaching Hospital for Children, Karbala, Iraq

Date of Submission18-Mar-2021
Date of Acceptance24-Apr-2021
Date of Web Publication16-Jun-2021

Correspondence Address:
Ayat Sahib Mohammed
Department of Pharmacology, College of Pharmacy, University of Karbala, Karbala
Iraq
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/bbrj.bbrj_36_21

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  Abstract 


Background: The β2-adrenergic receptor gene is a typical candidate for the study of genetic polymorphism, the biological relevance, and clinical consequences of polymorphisms. Many patients with asthma do not respond to β2-agonist; in addition, a wide interindividual variability in pharmacological response exists, likely because of the interaction between clinical, environmental, and genetic factors. Methods: A total of 80 asthmatic children, including 55 males and 25 females with acute attacks ages range between 5 and 18 years, attended the Respiratory Clinic at Karbala Pediatric Hospital, allele-specific polymerase chain reaction was performed to determine SNP of β2-adrenergic receptor gene at nucleic acid 46 (16 amino acid position). Results: Asthmatic children having GG genotype showed significant increase (P < 0.05) in all the recorded lung function parameter (forced expiratory volume in 1 s [FEV1], forced vital capacity [FVC], FEV1/FVC and FEV1% predicted) after treatment with nebulized salbutamol while those having AA and AG genotypes showed significant (increase) improvement (P < 0.05) only in FEV1, FVC, and FEV1% predicted after treatment with nebulized salbutamol and showed no significant increase (P > 0.05) in FEV1/FVC ratio after treatment with nebulized salbutamol, patients having GG genotype of 16Arg/Gly SNP showed highest change (increase) in FEV1 (204.44 ± 175.35) ml and in FEV1% predicted (15.22 ± 14.75) % after treatment with nebulized salbutamol in compared with other genotypes groups, although this change is not statistically significant (P > 0.05). Conclusion: Asthmatic children having GG (Gly16Gly) genotype showed better improvement in lung function after nebulized salbutamol in compared with those having AA (Arg16Arg) and those having heterozygous AG (Arg16Gly) during mild-to-moderate acute asthma attacks.

Keywords: Childhood asthma, nebulized salbutamol, spirometry, β2-adrenergic receptor gene


How to cite this article:
Mohammed AS, Abood HA, Hussein AM. The effect of 16 Arg/Gly β2–adrenergic receptors gene polymorphism on pulmonary function in asthmatic children treated with nebulized salbutamol. Biomed Biotechnol Res J 2021;5:161-5

How to cite this URL:
Mohammed AS, Abood HA, Hussein AM. The effect of 16 Arg/Gly β2–adrenergic receptors gene polymorphism on pulmonary function in asthmatic children treated with nebulized salbutamol. Biomed Biotechnol Res J [serial online] 2021 [cited 2021 Jul 23];5:161-5. Available from: https://www.bmbtrj.org/text.asp?2021/5/2/161/318430




  Introduction Top


Asthma is a syndrome more than a disease, and mainly has many environmental and genetic factor, resulting in airway hyper responsiveness, obstruction, mucus hyper-production, and airway wall morbidity.[1] The disease influence both adults and children, with high morbid and relative little mortality as compared with other chronic disease.[2],[3] Spirometry is the first-line test to diagnose asthma in children. The introduction of this test across all health-care settings has the ability to reduce misdiagnosis, developed asthma management, and decrease the health care spending for asthma.[4] Forced expiratory in bronchi calculations may help in the diagnosis and monitoring asthma and in assessing efficacy of treatment. Pulmonary function test is mainly helpful in children with asthma who are small perceivers of airflow obstruction, or when physical signs of asthma do not happen.[5] Salbutamol is first-line therapy of acute attack of asthma, it has a rapid onset of action (3–5 min), bronchodilation is maximum within 15–30 min and continuous for 3–4 h, so these agents considered as the drugs of choice for the acute asthma symptoms and for suppressing exercise-induced bronchoconstriction in children of the all ages.[6] The reversibility to bronchodilator drugs is usually calculated in a standardized way by first measuring lung function, usually forced expiratory volume in 1 s (FEV1), then inhaling a bronchodilator drug and then measuring FEV1 after a proper time, enabling the bronchodilator drug to have an effect on a bronchial smooth muscle.[7] In many methods, the beta2-adrenergic receptor gene is a typical candidate for the study of genetic polymorphism, the biological relevance, and clinical consequences of polymorphisms. The receptor is expressed on most of cells, and agonists are used in therapy of a number of diseases, like asthma.[8] In 1993, the existence of polymorphisms of the human ADRB2 was achieved.[9] ADRB2 Arg16Gly polymorphism is one of the most common nonsynonymous SNPs at amino acid 16, either Arg or Gly can be present, the former is the minor allele but for multiple years regarded as the “wild type.”[10] Several researches have demonstrated that homozygotes of Arg16 are more probably to respond (better rapid response and increased in FEV1) to albuterol[11] as compared to homozygotes of Gly16 and heterozygotes.[12] Other investigations, however, recorded no association between this SNP and different drug response,[13],[14],[15] whereas some group showed contradictory outcomes.[16],[17]

This study aimed to investigate the effect of β2–adrenergic receptor polymorphisms Arg16Gly A 46 > G (rs1042713) on the therapeutic response of β2-agonist in asthmatic children.


  Methods Top


The protocol of this study was approved by the ethical research and scientific committee of College of Pharmacy, University of Karbala. Approval was also taken from Karbala Health Directorate and Administration of Karbala Teaching Hospital for children. In addition, consent was taken from parents of each patient after explaining the nature and purpose of study.

Patients

This study included a total of 80 consecutive asthmatic children with acute attack of asthma (55 males and 25 female) attending the respiratory clinic at Kerbala Pediatric Hospital in the period from September 2019 to the end of February 2020 with age of asthmatic children ranged between 5 and 18 years. All the children had the American Thoracic Society criteria for asthma.[18]

Patients assessment and follow-up

Asthmatic children with acute attacks assessed according to pulmonary function test. Assessment of lung function was done by Spirometer (Spirolab III) using forced vital capacity mode (FVC).[19] Standard dose of salbutamol nebulizer was used in this study. The reversibility to bronchodilator drugs is usually calculated in a standardized way by first measuring lung function at baseline usually FEV1, FVC, and the FEV1/FVC ratio then inhaling a bronchodilator drug and then repeated the pulmonary function parameter after 15 min of treatment.

Genotype

Blood samples were obtained from eligible children to extract genomic DNA using G-DEXTM IIb (intron, Korea). The polymorphism of the ADRB2 was detected using allele-specific polymerase chain reaction (PCR) to assess SNP at nucleic acid 46 (16 amino acid position) and the primer pairs used to delineate the 2 polymorphisms at nucleic acid 46 to detect ADRB2 mutations at codon 16 (ADRB2 16) were 5-CTTCTTGCTGGCACCCAATA-3 (sense) and 5-CCAATTTAGGAGGATGTAAACTTC-3 (antisense) or the same antisense primer and 5-CTTCTTGCTGGCACCCAATC-3 (sense).[20],[21] PCR reaction mixtures included: 5 μL of DNA sample, 2 μL of sense primer, 2 μL of antisense primer and 11 μL of nuclease free water, PCR tube of premix that contain 5 μL of premix at 25°C then, centrifuged for 10 s at 2000 x g in a micro centrifuge for mixing the sample tubes and then placed in thermocycler. 5 μL of the PCR mixture was then electrophoresed on 1% agarose gels and visualized with ethidium bromide staining and ultraviolet illumination. The sizes of the PCR products were 913 base pairs (bps) for ADRB2 16.

Statistical analysis

Data were introduced into the Statistical Package for the Social Sciences software version 20 (Graph Pad Software, San Diego, California, USA) to do statistical analysis. The data were expressed as mean ± standard deviation. Differences of data express by percentage were examined by analysis of variance Fisher's exact due to cell count were <5. The Chi-square test was used to analyzed the differences of data expressed by percent (>5) in genotype groups. Differences within genotypes groups were examined by the analysis of variance test. The paired t-test was used calculate the P value at baseline and after treatment in genotype groups. All statistical procedures and tests were applied under a level of significance (P value) of <0.05 to be considered as significant difference or correlation.


  Results Top


The distribution of genotyping groups of asthmatic patients is show in [Table 1] and [Figure 1]. [Table 2] shows the demographic profile of asthmatics children, there was no significant association (P > 0.05) regarding age, weight, height, BMI, and gender between different genotypes of 16Arg/Gly SNP in asthmatic children. The significant improvement in pulmonary function parameters (P < 0.05) in FEV1, FVC, FEV1/FVC ratio, and FEV1% predicted after treatment with salbutamol in asthmatic children as summarized in [Table 3]. The effect of treatment with salbutamol on lung function in asthmatic children with different genotypes of 16Arg/Gly SNP is shown in [Table 4]. Patients having GG genotype showed significant (increase) improvement (P < 0.05) in all the recorded lung function parameter (FEV1, FVC, FEV1/FVC, and FEV1%predicted) after treatment with nebulized salbutamol while those having AA and AG genotypes showed significant (increase) improvement (P < 0.05) in FEV1, FVC, and FEV1%predicted after treatment with nebulized salbutamol, while showed no significant increase (P > 0.05) in FEV1/FVC ratio after treatment with nebulized salbutamol. [Table 5] and [Figure 2] and [Figure 3] demonstrate that patients having GG genotype of 16Arg/Gly SNP showed highest change (increase) in FEV1 (204.44 ± 175.35) ml and in FEV1% predicted (15.22 ± 14.75) after treatment with nebulized salbutamol in compared with other genotypes groups, although this change is not statistically significant (P > 0.05).
Table 1: Distribution of ADRB2 gene polymorphism 16 Arg/Gly SNP different genotype in asthmatic children

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Figure 1: Distribution of different genotype of 16 Arg/Gly SNP of ADRB2 gene in asthmatic children

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Table 2: Association between demographic characteristic and different genotypes of 16Arg/Gly SNP in asthmatic children

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Table 3: Effect of treatment with salbutamol on pulmonary function parameters in asthmatic children

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Table 4: Effect of treatment with salbutamol on pulmonary function in asthmatic children with different genotypes of 16Arg/Gly SNP

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Table 5: Association of pulmonary function parameter with 16Arg/Gly SNP

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Figure 2: Change (increase) in forced expiratory volume in 1 s percentage predicted after treatment in different genotypes of 16Arg/Gly SNP

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Figure 3: Change (increase) in forced expiratory volume in 1 s after treatment in asthmatic children with different genotypes of 16Arg/Gly SNP

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  Discussion Top


Asthmatic patients show a large heterogeneity in response to bronchodilator short acting β2-agonist. Rapidly evolving genotyping technologies have led to the identification of various genetic variants associated with treatment outcomes.[22] The genotypes of β2-adrenergic receptor (AA, GG, and AG) in the study were 51.2%, 33.8%, and 15%, respectively, of asthmatic children. This was the first interventional prospective study done on Iraqi asthmatic children demonstrate the rationale behind conducting asthma pharmacogenetics studies, provide an overview of asthma pharmacogenetics phenotypes, and detail the most important results of asthma pharmacogenetics studies in the Iraqi population. Some studies found that the Arg-16 genotype is associated with reduced response to β2-adrenergic agonists (189), whereas others have found that the Gly-16 genotype is associated with reduced response (172). In this study, patients having GG (Gly/Gly) genotype show better pulmonary function improvement compared with patients having AA (Arg/Arg) and heterozygous AG (Arg/Gly). These results in line with several previous studies on asthmatic children, one of these studies done by Martinez et al. 1997 genotyped 269 children of Hispanic or Caucasian descent, 78 (29.2%) of whom reported episodes of wheezing during the previous year. They found that children who were homozygous for Arg16 were 5.3 times more likely to respond to a single dose of albuterol than the children who were homozygous for Gly16.[12] Another study by Ritushree et al. 2005 on the Indian population found that patients with a homozygous Arg-16 form at nucleotide position 46 are poor responders to salbutamol treatment, and patients with a homozygous Gly-16 form are good responders.[17] On the other hand, the results disagree with another previous study on ADRB2 polymorphism and salbutamol responsiveness in Northern Indian children with mild-to-moderate exacerbation of asthma, in study reported by Sahi et al. 2016, who trend toward greater bronchodilator responsiveness among AA genotype, compared to GG genotype was observed (Median change in percent predicted FEV1 14.5% and 7.5%, respectively).[23]


  Conclusion Top


Asthmatic children having GG (Gly16Gly) genotype showed better improvement in lung function after nebulized salbutamol in compared with those having AA (Arg16Arg) and those having heterozygous AG (Arg16Gly) during mild-to-moderate acute asthma attacks.

Financial support and sponsorship

Nil.

Conflicts of interest

The authors declare that none of the authors have any competing interests.



 
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    Figures

  [Figure 1], [Figure 2], [Figure 3]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5]



 

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