Lack of association between ACE gene polymorphisms and atopy and asthma in British and Japanese populations

Genetically high angiotensin-converting enzyme concentrations causally increase asthma risk: A meta-analysis using Mendelian randomization

Objectives

This meta-analysis aimed to test the association of angiotensin-converting enzyme (ACE) gene I/D polymorphism with asthma risk and circulating ACE changes.

Methods

Public literature retrieval, publication selection, and information extraction were completed independently by two investigators. Effect-size values are expressed as odds ratios (ORs) or standardized mean differences (SMDs) with a 95% confidence interval (95% CI).

Results

Nineteen studies (2,888 patients and 9,549 controls) fulfilled the eligibility criteria. Overall investigations demonstrated that ACE gene I/D polymorphism was significantly associated with asthma risk under allelic (OR, 95% CI: 1.26, 1.08 to 1.48), homozygous genotypic (1.50, 1.09 to 2.06), and recessive (1.53, 1.24 to 1.89) models with moderate heterogeneity (I2 statistic: 64% to 79%). Subsidiary investigations recorded that race, matched status, asthma diagnosis, sample size, and age possibly accounted for the existence of significant heterogeneity. Relative to carriers with the II genotype, those with the DD genotype, ID genotype, and the combination of DD and ID genotypes had significantly higher concentrations of circulating ACE (WMD: 3.13, 2.07, and 2.83 U/L, respectively, p < 0.05). Adoption of Mendelian randomization analyses revealed that one unit increment in circulating ACE concentrations was found to be significantly associated with a 1.14-fold increased risk of asthma (95% CI: 1.02 to 4.24).

Conclusion

We provided strong meta-analytical evidence supporting the causal implication of high circulating ACE concentrations in the development of asthma.

Association studies for asthma and atopic diseases: a comprehensive review of the literature

Hundreds of genetic association studies on asthma-related phenotypes have been conducted in different populations. To date, variants in 64 genes have been reported to be associated with asthma or related traits in at least one study. Of these, 33 associations were replicated in a second study, 9 associations were not replicated either in a second study or a second sample in the same study, and 22 associations were reported in just a single published study. These results suggest the potential for a great amount of heterogeneity underlying asthma. However, many of these studies are methodologically limited and their interpretation hampered by small sample sizes.

Association of the TNF-alpha-308 (G-->A) polymorphism with self-reported history of childhood asthma

Asthma is a complex disease involving genetic and environmental aetiology. The tumour necrosis factor-alpha (TNF-alpha) and angiotensin-converting enzyme (ACE) genes have been implicated in asthma pathogenesis. This study investigated the association of a G-308A variant of TNF-alpha and an insertion/deletion (I/D) variant of ACE with a self-reported history of childhood asthma, in two population groups. At Northwick Park Hospital, London, 1,811 pregnant women attending for antenatal care were recruited. Participants with a self-reported history of childhood asthma, determined by a researcher-administered questionnaire, and controls with no personal or family history of asthma, of UK/Irish (cases n=20; controls n=416) and South Asian (cases n=6; controls n=275) origin were used in this study. Participants were genotyped for the TNF-alpha-308 and ACE I/D variants by a PCR-RFLP and PCR approach. The TNF-alpha-308 allele 2 (-308A) was significantly associated with self-reported childhood asthma in the UK/Irish (Odds ratios (OR): 2.6; 95% confidence intervals (CI): 1.1-6.2; P=0.03) but not in the South Asian population. The ACE DD genotype was not associated with childhood asthma in either population group. Gametic phase disequilibrium between the TNF-alpha-308 and ACE I/D variants was significantly different from zero in UK/Irish cases (delta=0.09; P=0.034). The TNF-alpha308 allele 2 or a linked major histocompatibility complex (MHC) variant may be a genetic risk factor for childhood asthma in the UK/Irish sample.