Relation of beta2-adrenoceptor polymorphisms at codons 16 and 27 to persistence of asthma symptoms after the onset of puberty

Sex and gender in asthma

Asthma is a heterogenous disease, and its prevalence and severity are different in males versus females through various ages. As children, boys have an increased prevalence of asthma. As adults, women have an increased prevalence and severity of asthma. Sex hormones, genetic and epigenetic variations, social and environmental factors, and responses to asthma therapeutics are important factors in the sex differences observed in asthma incidence, prevalence and severity. For women, fluctuations in sex hormone levels during puberty, the menstrual cycle and pregnancy are associated with asthma pathogenesis. Further, sex differences in gene expression and epigenetic modifications and responses to environmental factors, including SARS-CoV-2 infections, are associated with differences in asthma incidence, prevalence and symptoms. We review the role of sex hormones, genetics and epigenetics, and their interactions with the environment in the clinical manifestations and therapeutic response of asthma.

How to estimate overweight in pubescent asthmatics?

PURPOSE

The purpose of our research was to compare the body mass index (BMI) and selected anthropometric parameters in asthmatic and non-asthmatic pubescents.

MATERIAL AND METHODS

The study group consisted of 64 asthmatic boys and 45 girls; the control group consisted of 68 nonasthmatic boys and 48 non-asthmatic girls. All the children were 12-14 years old. We measured anthropometric parameters by a standardized method and the percentage of fat using the simple 2-site skinfold method. Additionally, we calculated the percentage of body composition (Matiegka) and the components of somatotype (Heath-Carter). Statistical significance was estimated at the level of p<0.05 by ANOVA test.

RESULTS

The asthmatic boys were significantly shorter than the non-asthmatic (p=0.015), however, we did not find any significant differences in weight and/or BMI in boys nor girls. The asthmatic boys had significantly higher fat mass % than the non-asthmatic ones (p<0.001). Moreover, they had significantly lower muscle mass % (p<0.001) as well as the bone mass % (p<0.001). The asthmatic girls had higher fat mass % than the non-asthmatic ones (p=0.028) and lower muscle mass % (p<0.001). The simple 2-site skinfold method also showed higher fat % in the asthmatic boys (p<0.001) but not in the girls. Examining the Heath-Carter somatotype components, the higher endomorphy was the only significant difference in asthmatic boys (p<0.001) and near significant in asthmatic girls (p=0.053).

CONCLUSION

Examination of the BMI alone is not sufficient in asthmatic children because of their high percentage of fat. That is why additionally testing fat % is recommended.

IFNG genotype and sex interact to influence the risk of childhood asthma

BACKGROUND

Asthma is a complex disease characterized by sex-specific differences in incidence, prevalence, and severity, but little is known about the molecular basis of these sex-based differences.

OBJECTIVE

To investigate the genetic architecture of sex differences in asthma risk, we evaluated (1) associations between polymorphisms in the IFNG gene and childhood-onset asthma in combined and sex-specific samples and (2) interactions between polymorphisms and sex on asthma risk.

METHODS

Main and sex-interaction effects of IFNG genetic diversity on asthma risk and IFN-γ levels were examined in a birth cohort of children at high risk for asthma and allergic diseases. Replication of the genetic association was assessed in an independent sample of asthma cases.

RESULTS

Significant genotype-sex interactions on asthma were observed for 2 IFNG single nucleotide polymorphisms, rs2069727 and rs2430561, which were in strong linkage disequilibrium with each other. In contrast, none of the 10 IFNG single nucleotide polymorphisms showed significant main effects on asthma. The observed genotype-sex interaction on asthma was characterized by nonadditivity; that is, heterozygous boys had the highest risk for asthma, and heterozygous girls had the lowest risk. The interaction effect was robust to other asthma risk factors but was limited to children who experienced wheezing illnesses with viral infections during the first 3 years of life. Genotype-sex interactions were also observed in the IFN-γ response to LPS in the first year of life. Finally, the sex-interaction effect was replicated in an independent population of childhood asthma cases.

CONCLUSIONS

These results provide insight into the genetic basis of sex differences in asthma and highlight the potential importance of interactions among sex, genotype, and environmental factors in asthma pathogenesis.

Beta2-adrenergic receptor polymorphisms affect response to treatment in children with severe asthma exacerbations

BACKGROUND

beta(2)-adrenergic receptor (AR) agonists are the mainstay of treatment for severe asthma exacerbations, one of the most common causes of critical illness in children. Genotypic differences in the beta(2)-AR gene, particularly at amino acid positions 16 and 27, have been shown to affect the response to beta(2)-AR agonist therapy. Our hypothesis is that genotypic differences contribute to patient response to beta(2)-AR agonist treatment during severe asthma exacerbations in children.

METHODS

Children admitted to the hospital ICU for a severe asthma exacerbation between 2002 and 2005 were located, and genetic samples were obtained from saliva. Children hospitalized during this period were treated with a protocol that titrated beta(2)-AR therapy (first nebulized, then IV) according to a validated clinical asthma score.

RESULTS

Thirty-seven children hospitalized during the study period were enrolled into the study. At amino acid position 16 in the beta(2)-AR gene, 13 children were homozygous for the glycine (Gly) allele (Gly/Gly), 8 were homozygous for the arginine (Arg) allele (Arg/Arg), and 16 were heterozygous (Arg/Gly). Despite similar clinical asthma scores on hospital admission, the children with the Gly/Gly genotype had significantly shorter hospital ICU length of stay and duration of continuously nebulized albuterol therapy and were significantly less likely to require IV beta(2)-AR therapy than those with Arg/Arg or Arg/Gly genotypes. No association existed among polymorphisms at amino acid position 27 and response to beta(2)-AR therapy.

CONCLUSIONS

In this cohort of children with severe asthma exacerbations, children whose genotypes were homozygous for Gly at amino acid position 16 of the beta(2)-AR gene had a more rapid response to beta(2)-AR agonist treatment. The beta(2)-AR genotype appears to influence the response to therapy in this population.

An african-specific functional polymorphism in KCNMB1 shows sex-specific association with asthma severity

A highly heritable and reproducible measure of asthma severity is baseline pulmonary function. Pulmonary function is largely determined by airway smooth muscle (ASM) tone and contractility. The large conductance, voltage and calcium-activated potassium (BK) channel negatively regulates smooth muscle tone and contraction in ASM. The modulatory subunit of BK channels, the beta1-subunit, is critical for proper activation of BK channels in smooth muscle and has shown sex hormone specific regulation. We hypothesized that KCNMB1 genetic variants in African Americans may underlie differences in bronchial smooth muscle tone and thus pulmonary function, possibly in a sex-specific manner. Through resequencing of the KCNMB1 gene we identified several common variants including a novel African-specific coding polymorphism (C818T, R140W). The C818T SNP and four other KCNMB1 variants were genotyped in two independent groups of African American asthmatics (n = 509) and tested for association with the pulmonary function measure--forced expiratory volume (FEV(1)) % of predicted value. The 818T allele is associated with a clinically significant decline (-13%) in FEV(1) in both cohorts of asthmatics among males but not females (P(combined) = 0.0003). Patch clamp electrophysiology studies of the BK channel expressed with the 140Trp variant of the beta1-subunit demonstrated significantly reduced channel openings, predicted by the loss of pulmonary function observed. African American male asthmatics carrying the 818T allele (10% of population) are potentially at risk for greater airway obstruction and increased asthma morbidity. Female asthmatics may be insulated from the deleterious effects of the 818T allele by estrogen-mediated upregulation in BK channel activity.

Variations in genetic influences on the development of asthma throughout childhood, adolescence and early adult life

PURPOSE OF REVIEW

Asthma is likely to be due to many aetiological factors, the effect of each varying considerably with age. Now that there are well established candidate genes for asthma, using genetics to examine age-related susceptibility to asthma offers a new approach to understanding the basic underlying mechanisms.

RECENT FINDINGS

Since few long-term, longitudinal asthma studies exist, opportunities to examine age-related genetic susceptibility have been limited, but have produced some specific findings. The CCR5Delta32 polymorphism renders the chemokine receptor nonfunctional and is associated with reduced asthma susceptibility in children but not adults. In CD14 C-159T, the -159C allele has been associated with increased atopy in mid-childhood, but not in young adults. IL-12beta is a promoter polymorphism associated with reduced lung function in girls but not boys in mid-childhood only. Regarding the beta(2)adrenoceptor, results from three studies suggest that Arg16 can be associated with impaired airway function in infancy and Gly16 with asthma and wheeze in mid-childhood.

SUMMARY

Age-related genetic susceptibility studies are likely to make a major contribution to understanding basic mechanisms in asthma, but the limited number of suitable cohorts has meant that to date few studies have been reported.

Susceptibility genes in severe asthma

Asthma is a common complex disease with a very wide spectrum of severity. Although part of this may be due to differing environmental interactions and inadequate treatment, there is increasing evidence that in addition to susceptibility genes for asthma onset, there are also important genetic influences over the disease severity, response to treatment, and natural history. In this review, we bring together recent literature in the field of genetic influences over disease severity and discuss some of the clinical implications in terms of drug discovery and personalized medicine.

Childhood asthma: breakthroughs and challenges

As we move forward, our goal is to control and eliminate asthma and other allergic disorders. This may come through broadly applied manipulation of environmental, dietary, and infectious risk factors, possibly during the perinatal period. Or we may learn to identify genetically susceptible children and to intervene with individualized genotype-specific treatment before the onset of disease. Maybe we'll learn how to block the mechanisms that give rise to chronic inflammation, or how to subdue Th2 activation. However, as the Swedish proverb says--Don't throw away the old bucket until you know whether the new one holds water. To continue using the old bucket, we have to fix the leaks. One approach to reducing asthma disparities is through traditional disease prevention stages. Primary prevention targets asthma incidence; secondary prevention mitigates established disease and involves disease detection, management, and control; and tertiary prevention is the reduction of complications caused by severe disease. Once causative factors at each level of disease prevention are understood, this knowledge can be translated into clinical practice and public health policy. We need reliable diagnostic criteria to provide correct treatment for infants and toddlers. This will require longitudinal cohort studies supported by assessment of pulmonary function and inflammatory markers. We must find ways to convince more physicians to embrace controller therapy for more severe disease, and to identify the patients with less severe disease who also require ongoing controller therapy. We need to close the gap between what we know and what we do in practice. We need to link basic research to healthcare delivery, and to gain acceptance and support from the intended recipients of new interventions. We need better strategies for improving adherence. We need accountability, foresight, and imagination.