Angiotensin-Converting Enzyme (ACE, I/D) Gene Polymorphism and Susceptibility to Abdominal Aortic Aneurysm or Aortoiliac Occlusive Disease

Relationship of genetic factors with development of aortic dissection and aneurysm

Background

This study aims to investigate the relationship between the development of aortic dissections and aneurysms with the polymorphisms of angiotensin converting enzyme gene, methylenetetrahydrofolate reductase gene, plasminogen activator inhibitor-1 gene, and nitric oxide synthase gene.

Methods

Between April 2009 and July 2014, 38 patients with aortic dissections (28 males, 10 females; mean age 55.1±10.7 years; range, 30 to 78 years) and 67 patients with aortic aneurysms (57 males, 10 females; mean age 63.0±11.4 years; range, 31 to 82 years) were included in this cross-sectional study. The control group consisted of 60 healthy volunteers (41 males, 19 females; mean age 56.3±11.2 years; range, 30 to 82 years) without an aortic aneurysm or dissection, as assessed by thoracoabdominal computed tomography. The prespecified four genes were genotyped with competitive allelespecific polymerase chain reaction.

Results

The aortic dissection group had higher nitric oxide synthase-3 (4b/4b) expression levels, compared to the control group. The aortic aneurysm group had also higher nitric oxide synthase-3 (4b/4a) expression levels, compared to the control group. Compared to the control group, a higher rate of angiotensin converting enzyme I/D gene polymorphism was detected in the aneurysm group, while higher D/D polymorphism rates were found in the dissection group; although not statistically significant.

Conclusion

Our study results suggest that the nitric oxide synthase-3 intron 4b/4b and nitric oxide synthase-3 intron 4b/4a gene polymorphisms can be used as a predictor of aortic dissection and aneurysm development.

Abdominal Aortic Aneurysm Genetic Associations: Mostly False? A Systematic Review and Meta-analysis

OBJECTIVE/BACKGROUND

Many associations between abdominal aortic aneurysm (AAA) and genetic polymorphisms have been reported. It is unclear which are genuine and which may be caused by type 1 errors, biases, and flexible study design. The objectives of the study were to identify associations supported by current evidence and to investigate the effect of study design on reporting associations.

METHODS

Data sources were MEDLINE, Embase, and Web of Science. Reports were dual-reviewed for relevance and inclusion against predefined criteria (studies of genetic polymorphisms and AAA risk). Study characteristics and data were extracted using an agreed tool and reports assessed for quality. Heterogeneity was assessed using I(2) and fixed- and random-effects meta-analyses were conducted for variants that were reported at least twice, if any had reported an association. Strength of evidence was assessed using a standard guideline.

RESULTS

Searches identified 467 unique articles, of which 97 were included. Of 97 studies, 63 reported at least one association. Of 92 studies that conducted multiple tests, only 27% corrected their analyses. In total, 263 genes were investigated, and associations were reported in polymorphisms in 87 genes. Associations in CDKN2BAS, SORT1, LRP1, IL6R, MMP3, AGTR1, ACE, and APOA1 were supported by meta-analyses.

CONCLUSION

Uncorrected multiple testing and flexible study design (particularly testing many inheritance models and subgroups, and failure to check for Hardy-Weinberg equilibrium) contributed to apparently false associations being reported. Heterogeneity, possibly due to the case mix, geographical, temporal, and environmental variation between different studies, was evident. Polymorphisms in nine genes had strong or moderate support on the basis of the literature at this time. Suggestions are made for improving AAA genetics study design and conduct.

Potential Interactions Between Genetic Polymorphisms of the Transforming Growth Factor-β Pathway and Environmental Factors in Abdominal Aortic Aneurysms

OBJECTIVE/BACKGROUND

Evidence has accumulated that multiple polymorphisms in the transforming growth factor (TGF)-β pathway and renin-angiotensin system play important roles in determining susceptibility to abdominal aortic aneurysm (AAA). Few studies have considered interactions between these gene polymorphisms and environmental factors. The aim of this study was to evaluate the contribution of single nucleotide polymorphisms (SNPs) and complex gene-environment interactions in AAA.

METHODS

Six SNPs located in TGFB, TGFBR1, TGFBR2 and AGTR1 were selected. Genotyping of blood samples and collection of lifestyle factors were performed in 155 unrelated participants with AAAs and 310 non-AAA controls. Unconditional logistic regression was performed to assess the effects of SNPs on the risk of AAA. Generalized multifactor dimensionality reduction (GMDR) was used to evaluate gene-gene and gene-environment interactions.

RESULTS

Participants carrying TGFB1 rs1800469 TT (odds ratio [OR] 1.83, 95% confidence interval [CI] 1.18-2.85) or AGTR1 rs12695895 TT (OR 4.21, 95% CI 1.41-12.53) genotypes had a higher risk of AAA than those with the common CC genotype. The gene-gene interaction of AGTR1 rs5182, TGFBR1 rs1626340, and TGFB1 rs1800469 was found to be the best model according to the results of the GMDR analysis (cross validation consistency [CVC]) 10/10; p = .010). Smoking, dyslipidemia, and rs1800469 together contributed to the risk of AAA, which demonstrated a potential and complex gene-environment interaction among the three variants that might affect AAA risk (CVC 6/10; p = .001).

CONCLUSION

In this study of the Chinese population, homozygosity of TGFB1 rs1800469-T and AGTR1 rs12695895-T might be associated with increased risk of AAA. The complex gene-gene and gene-environment interactions might contribute to the risk of AAA. As a small study, the preliminary results need extensive validation and replication in larger populations.

Analysis of multiple genetic polymorphisms in aggressive-growing and slow-growing abdominal aortic aneurysms

BACKGROUND

The natural history of abdominal aortic aneurysms (AAAs) suggests that some remain slow in growth rate whereas many develop a more accelerated growth rate and reach a threshold for intervention. We hypothesized that different mechanisms are responsible for AAAs that remain slow growing and never become actionable vs the aggressive AAAs that require intervention and may be reflected by distinct associations with genetic polymorphisms.

METHODS

AAA growth rate was determined from serial imaging data in 168 control and 141 AAA patients with ultrasound or computed tomography imaging studies covering ∼5 years. Genetic polymorphisms all previously reported as showing a significant correlation with AAA with functional effects on the expression or function were determined by analysis of the genomic DNA, including angiotensin 1 receptor (rs5186), interleukin-10 (IL-10; rs1800896), methyl-tetrahydrofolate reductase (rs1801133), low-density lipoprotein receptor-related protein 1 (LRP1; rs1466535), angiotensin-converting enzyme (rs1799752), and several matrix metalloproteinase 9 (MMP-9) single nucleotide polymorphisms.

RESULTS

Of the AAA patients, 81 were classified as slow AAA growth rate (<3.25 mm/y) vs 60 with aggressive AAA growth rate (>3.25 mm/y, those presenting with a rupture, or those with maximal aortic diameter >5.5 cm [male] or >5.0 cm [female]). Discriminating confounds between the groups were identified by logistic regression. Analyses identified MMP-9 p-2502 single nucleotide polymorphism (odds ratio [OR], 0.54; 95% confidence interval [CI], 0.31-0.94; P = .029) as a significant confound discriminating between control vs slow-growth AAA, MMP-9 D165N (OR, 0.49; 95% CI, 0.26-0.95; P = .035) and LRP1 (OR, 4.99; 95% CI, 1.13-22.1; P = .034) between control vs aggressive-growth AAAs, and methyltetrahydrofolate reductase (OR, 2.99; 95% CI, 1.01-8.86; P = .048), MMP-9 p-2502 (OR, 2.19; 95% CI, 1.05-4.58; P = .037), and LRP1 (OR, 4.96; 95% CI, 1.03-23.9; P = .046) as the statistically significant confounds distinguishing slow-growth AAAs vs aggressive-growth AAAs.

CONCLUSIONS

Logistic regression identified different genetic confounds for the slow-growth and aggressive-growth AAAs, indicating a potential for different genetic influences on AAAs of distinct aggressiveness. Future logistic regression studies investigating for potential genetic or clinical confounds for this disease should take into account the growth rate and size of the AAA to better identify confounds likely to be associated with aggressive AAAs likely to require intervention.

Associations between the insertion/deletion polymorphism of the angiotensin-converting enzyme and susceptibility to aortic aneurysms: A meta-analysis

INTRODUCTION

The purpose of this study is to examine whether the insertion (I) and deletion (D) polymorphism of the angiotensin-converting enzyme (ACE) confers susceptibility to aortic aneurysms (AAs).

MATERIALS AND METHODS

A meta-analysis was conducted on the associations between the ACE I/D polymorphism and all AAs and abdominal aortic aneurysms (AAAs).

RESULTS

Ten studies consisting of 2784 cases and 2682 controls were available for the meta-analysis. Meta-analysis showed a significant association between the D allele and all types of AA (OR 1.378, 95% CI 1.103-1.723, p = 0.005) and AAA (OR 1.274, 95% CI 1.004-1.617, p = 0.046). Meta-analysis of both the DD genotype and the DD vs. II genotype showed an association with AAAs. Stratification by ethnicity indicated an association between the D allele of the ACE I/D polymorphism and AAAs in Europeans (OR = 1.338, 95% CI = 1.026-1.745, p = 0.031), but not in Asians (OR = 0.927, 95% CI = 0.660-1.303, p = 0.663). Furthermore, analysis using the recessive model, dominant model, and homozygote contrast all showed the same pattern for the D allele.

CONCLUSIONS

Our meta-analysis demonstrates that the ACE I/D polymorphism is associated with susceptibility to AAAs in European populations.

Assessment of insertion/deletion polymorphism of the angiotensin-converting enzyme gene in abdominal aortic aneurysm and inguinal hernia

The aim of the paper is to determine whether the angiotensin-converting enzyme (ACE) gene insertion/deletion (I/D) polymorphism is associated with abdominal aortic aneurysm (AAA) and inguinal hernia. A case-control study was conducted in 264 subjects: 65 patients with AAA, 91 patients with inguinal hernia, 19 patients with both AAA and hernia, and 89 controls were investigated for the ACE I/D polymorphism. Genotype analysis was performed using a polymerase chain reaction technique. Significant differences in the genotype between the patient groups and controls were identified (aneurysm versus control, P = 0.011; aneurysm plus hernia versus control, P = 0.022; hernia versus control, P = 0.001), whereas no differences were found within patient groups. Patients with AAA and/ or hernia had an increased prevalence of I/D heterozygosity, which persisted even after adjusting for differences in confounding clinical variables (aneurysm versus control, OR 0.3, 95% CI 0.2–0.8, P = 0.005; aneurysm plus hernia versus control, OR 0.3, 95% CI 0.1-0.9, P = 0.040; hernia versus control, OR 0.4, 95% CI 0.2–0.7, P = 0.004). In conclusion, an association between the heterozygote ACE I/D state and the presence of AAA and/or hernia was identified. The role of the ACE I/D polymorphism in aneurysm and hernia needs further investigation.

Protective effects of angiotensin-converting enzyme I/I and matrix metalloproteinase-3 6A/6A polymorphisms on dilatative pathology within the ascending thoracic aorta

OBJECTIVE

Activation of matrix metalloproteinases and the renin/angiotensin signaling pathways is under investigation with regard to their potential pathogenesis in dilatative pathology of the aorta. The purpose of this study was to explore matrix metalloproteinase-3 5A/6A and angiotensin-converting enzyme I/D polymorphisms as predisposing factors to dilatative pathology of the aorta.

METHODS

We studied 107 patients who underwent aortic reconstruction surgery due to dilatative pathology of ascending thoracic aorta and a random sample of the population (n = 773), all from Lithuania. The insertion/deletion (-1171 5A/6A) polymorphism in the promoter region of matrix metalloproteinase-3 studied by real-time polymerase-chain-reaction amplification and the D and I alleles were identified on the basis of standard polymerase-chain-reaction amplification of the respective fragments from intron 16 of the angiotensin-converting enzyme gene.

RESULTS

The frequency of the angiotensin-converting enzyme D allele was significantly higher in dilatative pathology of ascending thoracic aorta patients than in the reference group subjects (0.55 vs 0.48, respectively). The latter group had a significantly higher frequency of the angiotensin-converting enzyme I/I genotype than in dilatative pathology of ascending thoracic aorta patients (27.4% vs 16.5%, respectively). In the reference group, the frequency of combined angiotensin-converting enzyme I/I and matrix metalloproteinase-3 6A/6A genotypes was 7.5%, while in the dilatative pathology of ascending thoracic aorta patient group, there was no one carrying that combined genotype (p = 0.001).

CONCLUSIONS

The present study showing a role of angiotensin-converting enzyme and matrix metalloproteinase-3 in the development of dilatative pathology of ascending thoracic aorta permits us to entertain a possible protective mechanism for the combined effects of the angiotensin-converting enzyme I/I and the matrix metalloproteinase-3 6A/6A genotypes.

Genes and abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a multifactorial disease with a strong genetic component. Since the first candidate gene studies were published 20 years ago, approximately 100 genetic association studies using single nucleotide polymorphisms (SNPs) in biologically relevant genes have been reported on AAA. These studies investigated SNPs in genes of the extracellular matrix, the cardiovascular system, the immune system, and signaling pathways. Very few studies were large enough to draw firm conclusions and very few results could be replicated in another sample set. The more recent unbiased approaches are family-based DNA linkage studies and genome-wide genetic association studies, which have the potential of identifying the genetic basis for AAA, only when appropriately powered and well-characterized large AAA cohorts are used. SNPs associated with AAA have already been identified in these large multicenter studies. One significant association was of a variant in a gene called contactin-3, which is located on chromosome 3p12.3. However, two follow-up studies could not replicate this association. Two other SNPs, which are located on chromosome 9p21 and 9q33, were replicated in other samples. The two genes with the strongest supporting evidence of contribution to the genetic risk for AAA are the CDKN2BAS gene, also known as ANRIL, which encodes an antisense ribonucleic acid that regulates expression of the cyclin-dependent kinase inhibitors CDKN2A and CDKN2B, and DAB2IP, which encodes an inhibitor of cell growth and survival. Functional studies are now needed to establish the mechanisms by which these genes contribute toward AAA pathogenesis.

Abdominal aortic aneurysm: a review of the genetic basis

BACKGROUND

Abdominal aortic aneurysm (AAA) is a complex disease with a largely unknown pathophysiological background and a strong genetic component. Various studies have tried to link specific genetic variants with AAA.

METHODS

Systematic review of the literature (1947-2009).

RESULTS

A total of 249 studies were identified, 89 of which were eventually deemed relevant to this review. Genetic variants (polymorphisms) in a wide variety of genes, most of which encode proteolytic enzymes and inflammatory molecules, have been associated with AAA development and progression.

CONCLUSION

The genetic basis of AAA remains unknown, and most results from ''candidate-gene'' association studies are contradictory. Further analyses in appropriately powered studies in large, phenotypically well-characterized populations, including genome-wide association studies, are necessary to elucidate the exact genetic contribution to the pathophysiology of AAA.

Genetic and epigenetic mechanisms and their possible role in abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a common disease associated with significant cardiovascular morbidity and mortality. The pathogenesis of AAA is poorly defined, making targeting of new therapies problematic. Current evidence favours an interaction of multiple environmental and genetic factors in the initiation and progression of AAA. Epigenetics is the term used to define the properties of the genome that are not explained by the primary sequence, but are due to the modifications of DNA and/or associated proteins. Previous research indicates the association of gene specific promoter DNA hyper-methylation and global DNA hypo-methylation with atherosclerosis. Evidence also suggests an important role for epigenetic processes such as histone acetylation in cardiovascular diseases including atherosclerosis and restenosis. Altered DNA methylation or histone acetylation occur in inflammation, cellular proliferation and remodelling processes and therefore maybe relevant to the pathology of AAA. Important risk factors for AAA, including cigarette smoking, older age, male gender and hypertension, have been linked with epigenetic effects and thus could act in this way to promote AAA. In this review, we discuss the potential role of epigenetic mechanisms in AAA. Since epigenetic alterations are to some extent reversible, further study of this area may identify new treatment targets for AAA.