Association of glutathione S-transferase M1 and T1 genotypes with asthma: A meta-analysis

BACKGROUND

We performed an updated meta-analysis to clarify the relationship between glutathione S-transferase Mu and theta (GSTM1 and GSTT1, respectively) null/positive genotypes and asthma.

METHODS

We performed a literature search using PubMed and Web of Science databases in August 2019. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to assess the role of GSTM1 and GSTT1 genotypes in the risk of asthma.

RESULTS

Overall, we found a significant association with asthma risk in the general population for both the GSTM1 genotype (OR = 1.21; 95% CI: 1.07-1.35; P < .001; I = 69.5%) and the GSTT1 genotype (OR = 1.61; 95% CI: 1.30-2.00; P < .001; I = 83.6%). Moreover, significant associations between both genotypes and asthma risk were also found by age stratification. Furthermore, for GSTM1 we found significant associations in populations living in Asia, Europe, and Russia, but not in Africa. Conversely, for GSTT1, we found a significantly increased risk in populations living in Asia, Europe, Africa, and Russia. In addition, a significant association was found for both genotypes with a sample size <500, but not a sample size >2000.

CONCLUSION

Our meta-analysis provides evidence that GSTM1 and GSTT1 genotypes could be used as asthma-associated biomarkers.

Significant association between asthma risk and the GSTM1 and GSTT1 deletion polymorphisms: an updated meta-analysis of case-control studies

Polymorphisms in GSTM1 and GSTT1 may be associated with asthma risk, yet several studies and meta-analyses have reported inconclusive results. Therefore, an updated meta-analysis was conducted. Literature searches were performed using the Pubmed, Embase and Web of Science databases until October 2012. Variant 'null' genotype was compared with wild-type 'present' in the pooled data. All statistical analyses were performed using STATA 11.0. A total of 26 case-control studies were suitable for inclusion in the meta-analysis. In the overall population, a significant association was found for both the GSTM1 (odds ratio (OR) = 1.452; 95% confidence interval (CI): 1.192-1.770) and GSTT1 polymorphism (OR = 1.792; 95% CI:1.293-2.483). For subgroup analysis by age, GSTM1 significantly increased risk for both children (OR = 1.368; 95% CI: 1.051-1.781) and adults (OR = 1.859; 95% CI: 1.183-2.921). For GSTT1, a significant association was only found in the adult population (OR = 2.312; 95%CI: 1.204-4.439). Based on subgroup analysis by ethnicity, a significant association for GSTM1 was found in Europe (OR = 1.303; 95% CI: 1.018-1.667), Africa (OR = 2.175; 95%CI: 1.560-3.031) and Latin America (OR = 2.265; 95%CI: 1.375-3.729). For GSTT1, significantly increased risk was found only for Asian (OR = 2.105; 95% CI: 1.101-4.025) and Russian (OR = 2.747; 95% CI: 1.071-7.046) populations. This meta-analysis provides evidence that GSTM1 and GSTT1 polymorphisms may be risk factors for asthma.

Glutathione S-transferase polymorphisms, asthma susceptibility and confounding variables: a meta-analysis

Oxidative stress is one of the main risk factors for asthma development. Glutathione S-transferases play an important role in antioxidant defences and may influence asthma susceptibility. In particular, GSTM1 and GSTT1 positive/null genotypes and the GSTP1 Ile105 Val polymorphism have been analyzed in a number of genetic association studies, with conflicting outcomes. Two previous meta-analyses have attempted to clarify the associations between GST genes and asthma, but these studies have also showed contrasting results. Our aim was to perform a meta-analysis that included independent genetic association studies on GSTM1, GSTP1, and GSTT1, evaluating also the effect of potential confounding variables (i.e. ethnicity, population age, and urbanization). Systematic review and meta-analysis of the effects of GST genes on asthma were conducted. The meta-analyses were performed using a fixed or, where appropriate, random effects model. The meta-analysis of the GSTM1 (n = 35), GSTT1 (n = 31) and GSTP1 (n = 28) studies suggests that no significant associations with asthma susceptibility were observed for GSTM1 and GSTP1 gene polymorphisms, whereas a significant outcome was detected for the GSTT1 positive/null genotype (pooled OR = 1.33, 95 %CI = 1.10-1.60). However, high between-study heterogeneity was identified in all the general analyses (p heterogenetity < 0.05). The stratification analysis seems to explain the heterogeneity only in few cases. This picture is probably due to the interactive process of genetics and environment that characterizes disease pathogenesis. Further studies on interactions of GST genes with the potential oxidative stress sources and with other antioxidant genes are needed to explain the role of GST enzymes in asthma.

Significant association between GSTT1 null genotype and risk of asthma during childhood in Caucasians

Asthma is a complex multifactorial disorder and its management requires a better understanding of its various pathogenesis and mechanisms. Previous studies assessing the association between glutathione S-transferase T1 (GSTT1) null genotype and asthma risk during childhood reported conflicting results. To get a more precise estimation of the association between GSTT1 null genotype and risk of asthma during childhood, we performed a meta-analysis of 16 studies with a total of 18,558 subjects. Subgroup analyses were performed by ethnicity. The pooled odds ratio (OR) with corresponding 95 % confidence interval (95 %CI) was used to assess the association. Overall, there was a significant association between GSTT1 null genotype and increased risk of children asthma (OR = 1.25, 95 % CI, 1.02-1.54; P = 0.032). Subgroup analyses showed GSTT1 null genotype was associated with increased risk of children asthma in Caucasians (OR = 1.46, 95 % CI, 1.04-2.03; P = 0.027), but not in Asians (OR = 1.03, 95 % CI, 0.55-1.94; P = 0.928) and Africans (OR = 1.33, 95 % CI, 0.92-1.91; P = 0.127). There was no evidence of publication bias in the subgroup analysis of Caucasians. In conclusion, there is a significant association between GSTT1 null genotype and risk of asthma during childhood in Caucasians. More well-designed epidemiological studies are needed to further assess this association in Asians and Africans.

The relationship among IL-13, GSTP1, and CYP1A1 polymorphisms and environmental tobacco smoke in a population of children with asthma in Northern Mexico

Exposure to environmental tobacco smoke (ETS) during early childhood increases the risk of developing asthma. The intention of this study was to genotype a population of children from Coahuila state in Northern Mexico and to determine whether polymorphisms of the CYP1A1, GSTP1, and IL13 genes are associated with exposure to ETS and subsequently a higher risk for asthma. IL13 plays an important role in the development of allergic response, particularly those related with airway inflammation. CYP1A1 and GSTP1 are xenobiotic-metabolizing enzymes induced by repeated exposure to toxicants. Polymorphisms of these genes have been related with ETS exposure and increased risk for asthma. To assess the effect of IL13 (-1112 C>T and Arg110Gln), GSTP1 (Ile105Val), and CYP1A1 (Ile462Val) on asthma risk and ETS exposure, we recruited 201 unrelated children and classified them into four groups: (1) control without ETS exposure; (2) control with ETS exposure; (3) with asthma and with ETS exposure and (4) with asthma and without ETS exposure. No association among ETS exposure, asthma, and the studied polymorphisms was denoted by multivariate analysis of this population.