Angiotensin-converting enzyme and apolipoprotein E genotypes and restenosis after coronary angioplasty

Influence of the angiotensin converting enzyme insertion or deletion genetic variant and coronary restenosis risk: evidence based on 11,193 subjects

The insertion/deletion (I/D) polymorphism of the gene encoding angiotensin converting enzyme is a controversial risk factor for restenosis after percutaneous transluminal coronary angioplasties (PTCA) in patients. Genetic association studies can be problematic to reproduce due to insufficient power, phenotypic heterogeneity, population stratification, small effect of the variant and even publication biases. To derive a more precise estimation of the relationship as well as to quantify the between-study heterogeneity and potential bias, a meta-analysis including 11,193 patients from 33 published cohort studies was performed. In a combined analysis, the summary per-allele odds ratio for restenosis was 1.31 (95% CI: 1.08-1.58, P = 0.006), and 1.22 (95% CI: 0.95-1.56, P = 0.12), for PTCA-stent and PTCA-balloon, respectively. In the subgroup analysis by ethnicity, significantly increased restenosis risks after PTCA-stent were found in Asians for the polymorphism; whereas no significant associations were found among Caucasians. As for restenosis risks after PTCA-balloon, no evidence of any gene-disease association was obtained in the stratified analyses according to ethnicity and study size. In conclusion, this meta-analysis demonstrated that the DD homozygous of ACE I/D polymorphism was significantly associated with elevated restenosis susceptibility after PTCA-stent among Asian populations.

Genetic polymorphism of angiotensin converting enzyme and risk of coronary restenosis after percutaneous transluminal coronary angioplasties: evidence from 33 cohort studies

Background

In the past decade, a number of cohort studies studies have been carried out to investigate the relationship between the insertion/deletion polymorphism of the gene encoding angiotensin-converting enzyme and risk of restenosis after percutaneous transluminal coronary angioplasties in patients. However, these studies have yielded contradictory results. Genetic association studies addressing this issue are frequently hampered by insufficient power. We therefore performed a meta-analysis of the published studies to clarify this inconsistency and to establish a comprehensive picture of the relationship between ACE I/D polymorphism and post-PTCA restenosis risk.

Methods

Databases including Pubmed, EMBASE, ISI Web of Science, EBSCO, Cochrane Library databases and CNKI were searched to find relevant studies. Odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the strength of association. The random-effects model was applied, addressing heterogeneity and publication bias.

Results

A total of 33 cohort studies involving 11,099 subjects were included. In a combined analysis, the OR for post-PTCA restenosis of the ACE DD genotype was 1.61 (95% CI: 1.27–2.04; P<10⁻⁵). In the subgroup analysis by intervention, significantly increased risks were also found in PTCA-stent and PTCA-balloon for the DD genotype of the polymorphism.

Conclusions

Our meta-analysis showed that the DD genotype of ACE I/D polymorphism was significantly associated with increased risk of restenosis, particularly for PTCA-stent.

ACE (I/D) polymorphism and response to treatment in coronary artery disease: a comprehensive database and meta-analysis involving study quality evaluation

BACKGROUND

The role of angiotensin-converting enzyme (ACE) gene insertion/deletion (I/D) polymorphism in modifying the response to treatment modalities in coronary artery disease is controversial.

METHODS

PubMed was searched and a database of 58 studies with detailed information regarding ACE I/D polymorphism and response to treatment in coronary artery disease was created. Eligible studies were synthesized using meta-analysis methods, including cumulative meta-analysis. Heterogeneity and study quality issues were explored.

RESULTS

Forty studies involved invasive treatments (coronary angioplasty or coronary artery by-pass grafting) and 18 used conservative treatment options (including anti-hypertensive drugs, lipid lowering therapy and cardiac rehabilitation procedures). Clinical outcomes were investigated by 11 studies, while 47 studies focused on surrogate endpoints. The most studied outcome was the restenosis following coronary angioplasty (34 studies). Heterogeneity among studies (p < 0.01) was revealed and the risk of restenosis following balloon angioplasty was significant under an additive model: the random effects odds ratio was 1.42 (95% confidence interval:1.07-1.91). Cumulative meta-analysis showed a trend of association as information accumulates. The results were affected by population origin and study quality criteria. The meta-analyses for the risk of restenosis following stent angioplasty or after angioplasty and treatment with angiotensin-converting enzyme inhibitors produced non-significant results. The allele contrast random effects odds ratios with the 95% confidence intervals were 1.04(0.92-1.16) and 1.10(0.81-1.48), respectively. Regarding the effect of ACE I/D polymorphism on the response to treatment for the rest outcomes (coronary events, endothelial dysfunction, left ventricular remodeling, progression/regression of atherosclerosis), individual studies showed significance; however, results were discrepant and inconsistent.

CONCLUSION

In view of available evidence, genetic testing of ACE I/D polymorphism prior to clinical decision making is not currently justified. The relation between ACE genetic variation and response to treatment in CAD remains an unresolved issue. The results of long-term and properly designed prospective studies hold the promise for pharmacogenetically tailored therapy in CAD.

Is inflammation a contributor for coronary stent restenosis?

The development of coronary stent has revolutionized the field of interventional cardiology by reducing the incidence of restenosis after balloon angioplasty. Despite significant progress in its prevention and treatment, however, in-stent restenosis (ISR) is still common, and remains a challenge for the interventional cardiologist. Restenosis after stent implantation is mainly caused by neointimal proliferation through the stent struts. Currently, there are three major factors has been demonstrated to be contributors for ISR, namely patients-, lesion- and genetic-related factors in large number of clinical trials. However, the triggers and pathophysiological mechanisms for ISR are not fully elucidated. Experimental as well as clinical studies indicate a marked activation of inflammatory cells at the site of stent structs, which are likely to play a key role in the process of neointimal proliferation and stent restenosis. Those data suggest that inflammation may be a major contributor for ISR. In fact, coronary stenting is a strong inflammatory stimulus and the acute systemic response to local inflammation produced by coronary stenting is highly individual and predicts restenosis and event-free survival. Thus, the attention should be paid on anti-inflammatory therapeutic approaches for ISR, and the benefit of anti-inflammatory therapy during the periprocedural period and long-term follow-up is dependent on the inflammatory status. Measurement of cytokine and acute phase proteins, such as C-reactive protein, therefore, may be important to identify high-risk subjects and develop specific treatment tailored to the individual patients.

677TT polymorphism of methylenetetrahydrofolate reductase in combination with low serum vitamin B12 is associated with coronary in-stent restenosis

BACKGROUND

Recent studies have shown that a common mutation (nucleotide 677 C-->T) in the methylenetetrahydrofolate reductase (MTHFR) gene may contribute to a mild rise in plasma homocysteine levels and increase the incidence of coronary artery disease. Therefore, this study was designed to further investigate whether the effects of MTHFR 677 C to T mutation, plasma homocysteine, serum vitamin B12, and folate can influence restenosis after successful coronary stenting.

METHODS AND RESULTS

We investigated 260 patients each with a lesion after successful coronary stent placement. All patients received a repeated angiography after 6 months, or earlier if clinically indicated. Angiographic in-stent restenosis (ISR) was defined as >or=50% diameter stenosis at follow-up. Genotyping for MTHFR was based on a polymerase chain reaction technique. Also fasting plasma homocysteine, vitamin B12, and folate levels were measured at the same time. The ISR rate was higher among the patients with the TT genotype than in those with the non-TT genotypes (64.0% versus 32.9%, P=0.002). There was no significant difference in plasma homocysteine levels among patients with the TT genotype and patients with the non-TT genotypes (15.9+/-7.6 versus 15.5+/-6.6 micromol/L, P=0.75). However, among the patients with the TT genotype, those with higher plasma homocysteine levels (>or=12 micromol/L) demonstrated a significantly higher ISR rate (75.0% versus 33.5%, P=0.001). Logistic regression analysis revealed that the combined presence of the MTHFR TT genotype and lower than average serum vitamin B12 (>or=550 pg/mL) resulted in the most significant difference in the risk of ISR (OR=3.57, CI=1.51-8.46, P=0.004; OR=2.36, CI=1.35-4.15, P=0.003).

CONCLUSIONS

MTHFR 677TT polymorphism and low serum vitamin B12 each individually increased the risk of coronary ISR. Furthermore, the combination of these parameters resulted in a greater increase in risk.

Buccal DNA Collection: Comparison of Buccal Swabs with FTA Cards

Collection and analysis of DNA, most commonly from blood or buccal cells, is becoming more common in epidemiologic studies. Buccal samples, which are painless to take and relatively easily collected, are often the preferred source. There are several buccal cell collection methods: swabs, brushes, mouthwash, and treated cards, such as FTA or IsoCode cards. Few studies have systematically compared methods of buccal cell collection with respect to DNA yield and amplification success under similar conditions. We compared buccal DNA collection and amplification using buccal swabs and FTA cards in 122 control subjects from our Australian case-control study of childhood acute lymphoblastic leukaemia. Buccal DNA was quantified using a real-time PCR for beta-actin and genotyped at the loci of three polymorphisms (MTHFR 677C>T, ACE I/D, and XPD 1012G>A). PCR was successful with DNA from buccal swabs for 62% to 89% of subjects and from FTA cards for 83% to 100% of subjects, depending on the locus. The matched pair odds ratios (95% confidence interval) comparing success of FTA cards with buccal swabs are as follows: MTHFR 677C>T using PCR-RFLP, 12.5 (11.6-13.5) and using real-time PCR, 130.0 (113.1-152.8); ACE I/D using PCR-amplified fragment length polymorphism, 3.36 (3.2-3.5); XPD 1012G>A using real-time PCR, 150.0 (132.7-172.3). FTA cards are a robust DNA collection method and generally produce DNA suitable for PCR more reliably than buccal swabs. There are, however, technical challenges in handling discs punched from FTA cards that intending users should be aware of.

Present status of outcome prediction of invasive coronary treatment by using genetic markers

A growing number of studies suggest that the outcome after invasive coronary treatment may be in part genetically determined. Here, we review the present status of outcome prediction of invasive coronary treatments by using genetic markers. Although some studies found an association between one or another genetic marker with one or another clinical endpoint, many other studies found no such relations; to date, none of the genetic markers that have been investigated in association studies are used in routine clinical practice to prospectively assess the prognosis following invasive coronary treatment or to decide upon therapeutic strategies. Many associations between genetic markers and certain clinical endpoints were initially reported in small studies but could not be confirmed in larger ones. Some of these discrepancies may be explained by publication bias. Some genetic variants may have true effects on clinical endpoints, which, albeit biologically interesting, do not bear much clinical relevance. On the other hand, many-if not most-studies that have been published to date are more or less grossly underpowered and very rarely report on the results of an a priori power analysis. Thus, there is still a need for further high-quality studies designed to investigate the specific contribution of genetic factors to the outcome after invasive coronary interventions.

Drug-Eluting Coronary Stents

The introduction and widespread use of coronary stents have been the most important advancement in the percutaneous treatment of coronary artery disease since the introduction of balloon angioplasty. Coronary artery stents reduce the rate of angiographic and clinical restenosis compared to balloon angioplasty. This angiographic restenosis was further reduced with the introduction of drug-eluting stents and hence further reduction in the frequency of major adverse cardiac events. Herein we present a comprehensive and up-to-date review about the use of drug-eluting stents in the treatment of coronary artery disease.

Apolipoprotein E Polymorphism and Stroke Subtypes in an Italian Cohort

BACKGROUND

Studies have indicated that apolipoprotein E (ApoE)-epsilon4 is a risk factor for ischemic cerebrovascular diseases (ICVD), but the existence of this association is still controversial. The aims of this study were: (1) to compare ApoE genotype and allele frequencies in Italian cases with ICVD and in healthy control subjects and (2) to compare ApoE allele frequencies among ischemic stroke subtypes.

METHODS

A hospital-based cohort of 302 Italian subjects with ICVD and 228 healthy subjects have been recruited to investigate the role of ApoE polymorphisms as risk factors for ICVD. TOAST criteria were employed to stratify ICVD cases by subtypes.

RESULTS

No significant differences in ApoE genotype and allele frequencies were found between cases and control subjects. The frequency of ApoE-epsilon4 was lower in cases than in control subjects (6% vs. 10.1%), although not significantly. No differences in ApoE genotype and allele frequencies were evident among ICVD subtypes. However, out of 36 ApoE-epsilon4 alleles 23 (3.7%) were found in subjects with ICVD related to primary degenerative arterial disease related to large vessel disease and small vessel disease, and 13 (2.1%) in remaining subjects. Using logistic regression analysis we assessed whether ApoE-epsilon4 allele was independently associated with risk of ICVD related to a primary degenerative arterial disease compared to other ICVD subtypes. While classical risk factors were significantly associated with higher risk for ICVD due to large vessel disease and small vessel disease than other ICVD subtypes, the role of ApoE-epsilon4 allele was not significant (OR 1.25, 95% CI 0.57-2.74).

CONCLUSION

Our study shows similar ApoE-epsilon4 genotype and allele frequencies in patients with ICVD and in control subjects. No differences were found among different ICVD subtypes either.

Apolipoprotein E polymorphism is not a predictor for repeated coronary artery bypass surgery

OBJECTIVES

Factors leading to the occlusion of coronary grafts are diverse and may at least partially be inherited. We aimed to study the possible genetic predisposition and especially the role of apoE epsilon4 allele as a risk factor for repeated coronary artery bypass grafting (CABG) in a case-control setting.

DESIGN

All patients (n=184) who underwent repeated CABG between 1990 and 1998 were identified in the computed registry of the Department of Cardiothoracic Surgery in Tampere University Hospital. Age, sex and operation date matched controls with first time CABG were selected from the same registry. DNA samples were collected by sample stick sent via the mail for buccal smear. The final analysis included 137 surviving matched pairs.

RESULTS

In patients <62 years of age (median age), family history emerged as the only significant (OR=3.4; 95% CI=1.5-7.8, p=0.004) predictor for repeated surgery. Among older patients, repeated CABG was no longer predicted by family history but by hypercholesterolemia (OR=2.1; 95% CI=1.1-4.0, p=0.027), modified by apoE genotype.

CONCLUSIONS

Our results suggest that medium-term survivors after redo CABG have a strong genetic predisposition unrelated to hypercholesterolemia or apoE genotype, leading to more severe coronary artery disease at earlier age. In the older age group, redo coronary artery bypass surgery is associated with hypercholesterolemia, which, although modified by apoE genotype, may mainly be due to other genetic or acquired factors.

Predictive factors for ischemic target vessel revascularization in the Prevention of Restenosis with Tranilast and its Outcomes (PRESTO) trial

OBJECTIVES

The aim of the present study was to determine the rates of target vessel revascularization (TVR) and to determine predictors of TVR from clinical and angiographic variables available in the Prevention of Restenosis With Tranilast and its Outcomes (PRESTO) database.

BACKGROUND

The rates of TVR after percutaneous revascularization procedures, and its prediction with available clinical and angiographic variables, is less well known.

METHODS

We studied nine-month TVR in 11,484 patients enrolled in the PRESTO trial. Clinical, lesion-related, and procedural characteristics were analyzed in a logistic regression model. Study data were divided at random into an 80% training set on which the models were developed and a 20% hold-out set on which the model properties were evaluated.

RESULTS

A total of 14% (n = 1,609) had ischemic TVR. Clinical variables with increased risk for TVR included younger age; hypertension; diabetes mellitus; nonsmokers; unstable angina; previous coronary artery bypass grafting; peripheral vascular disease; procedure- and lesion-related such as ostial location, multilesion angioplasty, location in the left anterior descending artery, length > or =20 mm, in-stent restenosis at baseline, and use of rotablator. There was significant increase in the risk of ischemic TVR at U.S. treatment sites. Smoking and stent placement were associated with lower risk of ischemic TVR. The mean area (+/- SD) under the receiver-operating characteristic curve of the bootstrap samples was 0.66, indicating a modest ability of the model to discriminate patients who needed TVR on follow-up.

CONCLUSIONS

Despite being the largest prospective trial designed to test restenosis, the discriminatory ability of the clinical and angiographic variables to predict TVR is modest.

Apolipoprotein E gene polymorphisms and thrombosis and restenosis after coronary artery stenting

Experimental data support a protective function of apolipoprotein E (apoE) against restenosis, the main factor limiting the long-term benefit of percutaneous coronary interventions. We investigated the possibility that the single nucleotide polymorphisms (SNPs)--219G/T, 113G/C, 334T/C, and 472C/T of the gene encoding apoE (APOE) are associated with the incidence of death and myocardial infarction or restenosis after stenting in coronary arteries. In addition, we asked whether the apoE isotype-related epsilon2/epsilon3/epsilon4 polymorphism, defined by specific allele combinations (haplotypes) of the 334T/C and 472C/T polymorphism, and other APOE haplotypes, derived from all four SNPs investigated, are associated with adverse clinical and angiographic outcomes after stenting. Our study included 1,850 consecutive patients with symptomatic coronary artery disease (CAD) who underwent stent implantation. Follow-up angiography was performed in 1,556 patients (84.1%) at 6 months after the intervention. We found that none of the APOE SNPs is associated with death and myocardial infarction or restenosis after stenting. In addition, we observed no relationship between APOE haplotypes and adverse outcomes. In conclusion, the APOE -219G/T, 113G/C, 334T/C, and 472C/T polymorphisms, either alone or in combination, do not represent genetic markers of the risk of thrombotic and restenotic complications in patients with CAD treated with coronary stenting.

Prevention of restenosis after coronary angioplasty

PURPOSE OF REVIEW

Despite numerous advances in coronary interventional techniques, the frequent occurrence of restenosis continues to plague interventional cardiology. With the widespread use of drug-eluting stents, there is a need to reexamine critically the roles of the various interventional techniques currently available.

RECENT FINDINGS

Drug-eluting stents have dramatically reduced the rates of restenosis and target vessel revascularization in a wide spectrum of patients with varying lesion morphologies. However, when restenosis does occur, it still tends to be dependent on the same factors that predict restenosis with bare metal stenting. The routine use of drug-eluting stents entails high initial costs to the health care system. Debulking as a means to improve outcomes after angioplasty has not lived up to expectations. Gene therapy is rapidly evolving into a viable means to reduce neointimal proliferation after angioplasty.

SUMMARY

Careful patient selection and attention to the procedure of stent deployment optimize the results of angioplasty with drug-eluting stents. Because of cost considerations, drug-eluting stents should be used in patients who are expected to have the greatest absolute benefit. In this context, when judiciously used, conventional balloon angioplasty and bare metal stenting still have a definite role in the management of patients with obstructive coronary artery disease.

Polymorphisms in the RAS and cardiac function

Since the discovery of the polymorphism in the angiotensin converting enzyme (ACE) and the consequences of this polymorphism on the activity levels of the enzyme, numerous association studies have been performed. However, these investigations do not often adhere to the most stringent criteria for such studies. The initial study reporting a positive association of the ACE polymorphism and myocardial infarction showed an increased risk of the DD genotype. This initial association was eventually refuted by a large, well conducted association study, which found a risk ratio of 1.02 after combining their own data with all published data. Although such large, well conducted association studies have not been performed in left ventricular (LV) hypertrophy, the association between DD genotype and hypertrophy is more convincing with a 192% excess risk of LV hypertrophy in untreated hypertensives. The role of ACE genotype in LV growth is well established, especially in athletes. In heart failure, large studies or meta-analyses have not been performed, because most studies have selected different end-points. This hampers a proper meta-analysis of the results obtained in associations with heart failure. As most association studies do not fulfill the criteria for good association studies and use too small sample sizes, it remains important to perform a meta-analysis to add meaning to the results of such studies. Above all, it is important to obey the rules set for association studies, large sample size, small P values, report associations that make biological sense and alleles that affect the gene product in a physiologically meaningful way.

Apolipoprotein E (apoE) isoforms differentially induce nitric oxide production in endothelial cells

Although apolipoprotein E3 (apoE3) is atheroprotective, two common isoforms, apoE2 and apoE4, produce recessive and dominant hyperlipidaemias, respectively. Using a fluorescent assay, we report herein that apoE3 particles secreted from recombinant cells stimulate more nitric oxide release in cultured human EA.hy926 endothelial cells than apoE2 or apoE4 (141% more than controls vs. 61 or 11%). Phosphatidylinositol (PI) 3-kinase inhibitors suppressed the apoE effect, while apoE receptor 2 (apoER2) was tyrosine phosphorylated. We conclude that apoE stimulates endothelial nitric oxide release in an isoform-dependent manner, and propose that tyrosine phosphorylation of apoER2 initiates PI3-kinase signalling and activation of nitric oxide synthase.

Apolipoprotein E polymorphism and atherosclerosis

The relationship between apolipoprotein (apo) E and vascular disease has been the subject of a considerable amount of research. However, this relationship is far from clearly defined. This deficiency appears to be due to a multitude of factors. Among these are differences in ethnicity, age (and possibly gender), diagnostic criteria, and environmental factors (eg, diet and smoking) that have contributed to the contradictory findings. Several diseases and their treatment may also influence this relationship. There are also documented interactions between apo E genotypes and other genes or vascular risk factors. One possible clinically relevant application of identifying the apo E genotype could be to assess the response to a particular drug treatment. It may also be that apo E polymorphism will become a good predictor of vascular death (eg, from myocardial infarction or stroke) rather than an indicator of the risk of developing vascular disease but without an acute ischemic event. More research is required to define the place of apo E genotyping in the management of vascular disease in its various forms. Whatever the future brings, the evaluation of apo E genotypes will need to be rapid, cheap, and technically undemanding before this investigation becomes widely available and clinically relevant.

Clinical restenosis after coronary stenting: perspectives from multicenter clinical trials

OBJECTIVES

We sought to evaluate clinical restenosis in a large population of patients who had undergone coronary stent placement.

BACKGROUND

One-year success after coronary stenting is limited mainly by restenosis of and requirement for repeat revascularization of the treated lesion. We studied 6,186 patients (6,219 lesions) pooled from several recently completed coronary stent trials. Clinical restenosis was defined using three different definitions: target lesion revascularization (TLR) beyond 30 days, target vessel revascularization (TVR) beyond 30 days, and target vessel failure (TVF), defined as TVR, any death, or myocardial infarction (MI) of the target vessel territory after hospital discharge.

RESULTS

By one year, 638 (12.2%) patients had TLR, 748 (14.3%) had TVR, and 848 (16.0%) had TVF, more than two-thirds higher than the rate of these end points at six months. The severity of angiographic restenosis (> or =50% follow-up diameter stenosis [DS]) in 419 of 1,437 (29%) patients undergoing routine angiographic follow-up correlated directly with the likelihood of TLR (73% vs. 26% for >70% DS compared with <60% DS). Smaller pretreatment minimum lumen diameter (MLD), smaller final MLD, longer stent length, diabetes mellitus, unstable angina, and hypertension were independent predictors of TLR. Prior MI and current smoking were negative predictors.

CONCLUSIONS

At one year after stenting, most clinical restenosis reflected TLR, which was predicted by the same variables previously associated with an increased risk of angiographic restenosis. The lower absolute rate of clinical restenosis relative to angiographic restenosis was due to infrequent TLR in lesions with less severe (<60% DS) angiographic renarrowing.

A meta-analysis of the angiotensin-converting enzyme gene polymorphism and restenosis after percutaneous transluminal coronary revascularization: evidence for publication bias

BACKGROUND

The insertion/deletion polymorphism of the gene encoding angiotensin-converting enzyme is a controversial risk factor for restenosis after percutaneous transluminal coronary revascularization in patients. Genetic association studies addressing this issue are frequently hampered by insufficient power. Therefore, we conducted a meta-analysis of this association, taking into account the possibility of publication bias.

METHODS

We used the MEDLINE database and reviewed citations in relevant articles to identify 12 studies. Information on the design of the studies, the detailed genotype distribution, the angiographic follow-up rate, and the restenosis rate were categorized by use of a standardized protocol.

RESULTS

Overall, DD (deletion-deletion) homozygotes had a higher restenosis risk than II (insertion-insertion) carriers (odds ratio 1.22, 95% CI 1.04-1.44, P <.05). However, the published studies were significantly heterogeneous, especially those addressing in-stent restenosis. Smaller studies tended to have positive results more frequently, which is characteristic of publication bias. Correcting for publication bias, we estimated the odds ratio to be 1.15 (95% CI 0.98-1.32, not significant). None of the published studies met all rules of genetic epidemiology.

CONCLUSION

We conclude that a clinically significant association of the angiotensin-converting enzyme polymorphism with restenosis after percutaneous transluminal coronary revascularization in patients is unlikely. This meta-analysis provides evidence that the pooled estimate based on published literature, which favors an association, is distorted by publication bias. Hence, screening for this mutation in clinical practice is not justified. Future research should preferentially focus on gene-gene interaction and comply with the rules of genetic epidemiology.

Angiotensin converting enzyme insertion or deletion polymorphism and coronary restenosis: meta-analysis of 16 studies

OBJECTIVE

To assess the association between genotype at the insertion or deletion polymorphism of the angiotensin converting enzyme gene and risk of coronary restenosis after percutaneous coronary intervention.

DESIGN

Meta-analysis of studies before July 2001 that reported on these genotypes and risk of coronary restenosis after a percutaneous coronary intervention, with or without coronary stenting.

RESULTS

16 studies, involving 4631 patients undergoing a percutaneous coronary intervention, yielded 1683 patients with restenosis after a mean weighted follow up of 5.5 months. The combined odds ratio for restenosis in people with the DD genotype was 1.23 (99% confidence interval 1.03 to 1.46). When studies were grouped by size, however, the combined odds ratios for restenosis in people with the DD genotype were 1.94 (1.39 to 2.71) for studies with less than 100 cases, 1.33 (0.92 to 1.93) for studies with 100-200 cases, and 0.92 (0.72 to 1.18) for studies with more than 200 cases (trend P=0.02). Similarly, when studies were grouped by genotyping procedures, significantly larger odds ratios were found in the studies that did not conceal disease status from laboratory staff and in the studies that did not use a second polymerase chain reaction amplification to reduce genetic mistyping.

CONCLUSION

Compared with other studies, larger and more rigorous studies show a weaker association between the angiotensin converting enzyme gene DD genotype and restenosis. Publication bias or detection biases can produce artefactual associations at least as large as those that might be expected for common polymorphisms in complex diseases, suggesting the need for larger and more rigorous genetic epidemiological investigations than are now customary.

Quinapril prevents restenosis after coronary stenting in patients with angiotensin-converting enzyme D allele

Restenosis after coronary artery stent implantation is attributed chiefly to intimal hyperplasia, which is prevented experimentally by angiotensin-converting enzyme (ACE) inhibitors. Therefore, the present study investigated whether the effect of quinapril, a tissue-specific ACE inhibitor, on the prevention of coronary restenosis differs according to ACE polymorphism. One hundred consecutive patients with successful stent implantation were randomly assigned to quinapril and control groups. Both follow-up angiography and ACE polymorphism analysis were obtained from 92 patients (control, 46; quinapril treatment, 46). The prevalence of risk factors did not differ statistically according to quinapril treatment or ACE genotypes. There was no statistically significant difference in the occurrence of restenosis 6 months after stenting between the groups. Quantitative coronary angiography revealed that quinapril treatment resulted in significantly higher minimal lumen diameter and significantly lower percent diameter stenosis (22.9 +/- 22.6 vs 37.1 +/- 19.7% in the control group, p < 0.05) in patients with the D allele although there was no difference in those with the II genotype. In addition, intravascular ultrasound revealed that quinapril treatment significantly prevented the loss of minimal lumen cross-sectional area and the increase in percent area stenosis (34.5 +/- 14.0 vs 53.3 +/- 16.4% in the control group, p < 0.05) in patients with the D allele compared to those with the II genotype. These results suggest that the administration of ACE inhibitors for the attenuation of lumen loss after coronary stent implantation is best for subjects with the D allele of the ACE genotype.

Is angiotensin I-converting enzyme a "master" disease gene?

Clustering of diseases has been appreciated by health insurers and epidemiologists for some time. Co-morbidity suggests shared pathways of disease. It is by now well agreed that common diseases have a strong genetic component. Here we present evidence that the angiotensin I-converting enzyme (ACE) deletion/deletion (D/D) genotype is associated with a large number of common adult diseases, including cardiovascular disease, cancer, and psychiatric disease. Since the ACE D/D genotype has been shown to be associated with increased levels of tissue ACE expression at the protein level, these data suggest that overactivity of ACE may be involved in the pathogenesis of common diseases, as well as the utility of effective ACE inhibition in their treatment and, perhaps, prevention.

Interaction between apolipoprotein-E and angiotensin-converting enzyme genotype in Alzheimer's disease

Both apolipoprotein-E (apo-E) epsilon 4 allele and angiotensin-converting enzyme (ACE) deletion (D) polymorphism have been associated with a high risk for coronary heart disease. Increased frequency of the epsilon 4 allele has also been reported in patients with late-onset of familial and sporadic Alzheimer's disease (AD). The primary aim of this study is to examine the possible relationship between the ACE gene polymorphism and AD. The second aim of this study is to explore the relation of the ACE and apo-E genotypes with AD. Polymerase chain reaction (PCR), restriction fragment length polymorphism (RFLP), and agarose gel electrophoresis techniques were used to determine the apo-E and ACE genotypes. The frequencies of ACE D and ACE insertion (I) allele among AD patients and controls were 55.7 percent versus 44.2 percent and 51.7 versus 48.2 percent, respectively. Apo-E allele frequencies in the AD group for epsilon 2, epsilon 3 and epsilon 4 were, 1.7 percent, 96.5 percent, and 1.7 percent, respectively. The apo-E allele frequencies of healthy groups for epsilon 2, epsilon 3 and epsilon 4 were 1 percent, 56 percent, and 1.7 percent, respectively. In conclusion ACE D and apo epsilon 4 allele were found to be more frequent in patients with Alzheimer's disease than in the control group.

Aspects of gene polymorphisms in cardiovascular disease: the renin-angiotensin system

The renin-angiotensin system (RAS) plays a central role in cardiovascular homeostasis. Angiotensin is the key peptide of the RAS, and exerts its influence on the heart and blood vessels both through its haemodynamic effects (via its influence on after-load and pre-load and determining coronary vasoconstriction) and through its direct cellular effects (via its actions on cell proliferation). Numerous studies in the past 10 years have demonstrated that the pharmacological inhibition of angiotensin converting enzyme (ACE), one of the two critical enzymes of the RAS, improves the outcome in patients with several cardiovascular disorders (hypertension, heart failure, ischaemic heart disease). These studies suggest a role of the RAS as a major determinant of cardiovascular risk. Recent data suggest that genetics may in turn contribute to modulating the effects of angiotensin on coronary vascular biology and ischaemia. This paper reviews the physiologic characteristics of the RAS and recent research developments related to angiotensin cell biology and pathobiology in heart disease. In particular, this review will cover the genetic aspects of RAS and their implications in cardiovascular disease.

Anti-ischemic potential of drugs related to the renin-angiotensin system

Actions mediated by the renin-angiotensin system may be inhibited at various levels: renin itself may be inhibited, angiotensin-I (A-1) conversion to angiotensin-II (A-II), or binding of A-II at the A-II type 1 (A-II1) receptor. The angiotensin-converting enzyme (ACE) inhibitors and the A-II1 receptor antagonists are now clinically established. Because ACE is a relatively unspecific peptidase which catalyses the breakdown of A-I, bradykinin and neuropeptides like substance P and neurotensin, the effects of ACE inhibitors go far beyond the prevention of A-II production. On the other hand, in certain tissues like vascular and cardiac tissue, A-II is produced by other enzymes, for instance chymase, and ACE inhibitors do not consistently prevent A-II production. The action of A-II1 receptor antagonists may also not be confined to prevention of binding of A-II at the A-II1 receptor, as by rebound more A-II may bind at the A-II type 2 (A-II2) receptor and thus mediate until now not well defined effects. Thus, anti-ischemic actions of these drugs may be related to multiple mechanisms. Inhibition of A-II effects at the A-II1 receptor may prevent systemic and coronary vasoconstriction and growth effects of A-II on various cell types. In addition, A-II may potentiate, by pre- and postsynaptic mechanisms, activation of the sympathetic nervous system. Prevention of breakdown of bradykinin, substance P and neurotensin may result in direct vasodilation or release of nitrous oxide from the endothelium. Thus, growth-inhibiting effects may also be mediated. All these mechanisms seem to direct to a reduction of cardiac load by vasodilation and to a limitation of cardiovascular cell growth. While the systemic circulating renin-angiotensin system is probably responsible for control of cardiac load, local systems seem to control cell growth. Systemic effects seem to depend on activation of the renin-angiotensin system which has been shown in various ischemic syndromes. Activation of various components of the renin-angiotensin system has been demonstrated in myocardial ischemia, acute myocardial infarction and coronary occlusion and reperfusion models as well as in chronic left ventricular dysfunction post-myocardial infarction. While animal models of stress-induced myocardial ischemia have revealed predominantly positive results, clinical studies, which mostly were small and not well controlled, were equivocal. Large clinical trials with ACE inhibitors in acute myocardial infarction showed small benefits over placebo. Hypotension seems to be a critical side-effect in this situation. Experimental models show protective effects of both ACE inhibitors and A-II1 receptor antagonists in the situation of ischemia and reperfusion. New data on large clinical trials in patients at risk of cardiovascular events but normal left ventricular function demonstrate clear benefits of an ACE inhibitor. Large clinical trials in patients with chronic left ventricular dysfunction post-myocardial infarction show reduction of ischemic events.

Apolipoprotein E polymorphisms and age at first coronary artery bypass graft

Apolipoprotein E (apoE) polymorphisms are heritable determinants of total and low-density lipoprotein cholesterol. The impact of apoE4 genotypes on the severity of atherosclerosis has been debated; however, recent studies have identified a correlation between apoE4 genotype and atherosclerosis. We assessed the impact of apoE4 genotype on age at first coronary artery bypass graft (CABG), hypothesizing that patients with the apoE4 allele are predisposed to coronary artery disease and present earlier for coronary revascularization. We assessed individual apoE genotypes and age in 560 patients undergoing primary CABG, by using analysis of variance (ANOVA) and controlling for gender. Because of the small number of patients in individual genotype groups, we compared patients with one or more copies of the apoE4 allele with those having no copies of the allele, again controlling for gender. A comparison of patients with one or more copies of the apoE4 allele with patients without the allele showed an earlier age at first CABG for those with the allele (P: = 0.032). Gene-dose analysis was also significant (P: = 0.012); patients with two copies of the allele presented at 54.2 +/- 6.9 yr. We report that the apoE4 allele is linked to age at first CABG. Identifying at-risk individuals may help prevent atherosclerosis. Further study is needed to define the mechanism of this association, and to define which coronary intervention is appropriate, based on long-term outcome.

IMPLICATIONS

A correlation exists between apolipoprotein E (apoE) genotypes and the severity of atherosclerosis. We hypothesized that patients with the apoE4 allele are predisposed to coronary artery disease and present earlier for coronary artery bypass graft (CABG). Individuals with the apoE4 allele presented earlier for CABG, and the apoE4 allele is linked to age at first CABG.

Apolipoprotein E inhibits neointimal hyperplasia after arterial injury in mice

The potential cytostatic function of apolipoprotein (apo) E in vivo was explored by measuring neointimal hyperplasia in response to vascular injury in apoE-deficient and apoE-overexpressing transgenic mice. Results showed a significant increase in medial thickness, medial area, and neointimal formation after vascular injury in both apoE knockout and wild-type C57BL/6 mice. Immunochemical analysis with smooth muscle alpha-actin-specific antibodies revealed that the neointima contained proliferating smooth muscle cells. Neointimal area was 3.4-fold greater, and the intima/medial ratio as well as stenotic luminal area was more pronounced in apoE(-/-) mice than those observed in control mice (P < 0.05). The human apoE3 transgenic mice in FVB/N genetic background were then used to verify a direct effect of apoE in protection against neointimal hyperplasia in response to mechanically induced vascular injury. Results showed that neointimal area was reduced threefold to fourfold in mice overexpressing the human apoE3 transgene (P < 0.05). Importantly, suppression of neointimal formation in the apoE transgenic mice also abolished the luminal stenosis observed in their nontransgenic FVB/N counterparts. These results documented a direct role of apoE in modulating vascular response to injury, suggesting that increasing apoE level may be beneficial in protection against restenosis after vascular surgery.

Lesion-to-lesion relationship of the restenosis process after placement of coronary stents

The interrelation between multiple stented lesions within one patient in the restenosis process is only partially understood. From 492 patients with follow-up angiograms after coronary stent placement, 115 patients underwent multilesion procedures involving 233 lesions. In randomly chosen 39 patients with 79 lesions, additional intravascular ultrasound (IVUS) studies were performed to measure intimal hyperplasia cross-sectional area (CSA) and thickness. A general linear model with intraclass correlation was used to calculate the coefficient of correlation rho (rho = 1.0 indicates perfect correlation; rho = 0.0 indicates no correlation) of late loss, late loss index, intimal hyperplasia CSA, and intimal hyperplasia thickness. Multivariate analysis showed restenosis in the companion lesion (odds ratio 4.68, 95% confidence interval 1. 68-12.92, P = 0.003) and small minimal lumen diameter preintervention (odds ratio 0.28, 95% confidence interval 0.11-0.73, P = 0.009) to be predictors of restenosis. There was a weak correlation between multiple lesions within the same patient for late lumen loss rho = 0.28 (95% confidence interval 0.10-0.46, P < 0. 001) and late loss index. IVUS analysis demonstrated correlation of intimal hyperplasia CSA rho = 0.40 (95% confidence interval 0.06-0. 74, P = 0.009) and of intimal hyperplasia thickness. In conclusion, late loss and intimal hyperplasia demonstrate a correlation between multiple stented lesions within one patient. In addition to known lesion related factors, restenosis in a companion lesion is a predictor for restenosis. Cathet. Cardiovasc. Intervent. 51:266-272, 2000.

The Insertion/Deletion Polymorphism of the Angiotensin-Converting Enzyme Gene and the Risk for Restenosis After PTCA

The therapeutic benefit of percutaneous transluminal coronary angioplasty (PTCA) is limited by restenosis in about 30% of patients. The underlying mechanisms are currently not well understood. Besides clinical and angiographic variables, genetic factors may be involved. We determined the angiotensin I-converting enzyme (ACE) I/D genotype as a possible risk factor for restenosis in 511 consecutive patients who had undergone successful PTCA and follow-up angiography. Clinical and angiographic variables were also considered as possible predictors of restenosis. One hundred sixty patients had restenosis as defined by a greater than 50% progression of residual stenosis of the dilated segment at follow-up angiography. There were significantly more patients with the ACE DD genotype in the restenosis than in the no-restenosis group. This difference did not remain statistically significant in an analysis of covariance that included genetic and clinical variables. Patients who subsequently developed restenosis had a higher degree of stenosis and more severe lesions before PTCA as well as less residual stenosis immediately after PTCA. We conclude that the ACE DD genotype is not an independent risk factor for restenosis after PTCA.

Large-scale test of hypothesised associations between the angiotensin-converting-enzyme insertion/deletion polymorphism and myocardial infarction in about 5000 cases and 6000 controls. International Studies of Infarct Survival (ISIS) Collaborators

BACKGROUND

The original report of a possible association between myocardial infarction and the insertion/deletion (I/D) polymorphism of the gene for the angiotensin-1-converting enzyme (ACE) indicated a risk ratio for myocardial infarction with the DD genotype of 1.34 (95% CI 1.05-1.70), and the association was claimed to be particularly strong in a retrospectively defined low-risk subgroup (3.2 [95% CI 1.7-5.9). Subsequent investigations reached varying conclusions, but all were small, and much larger studies were needed.

METHODS

4629 myocardial infarction cases and 5934 controls were compared. Cases were UK men aged 30-54 years and women aged 30-64 years recruited on presentation to hospital with confirmed myocardial infarction. Controls were aged 30-64 years with no history of cardiovascular disease, but were siblings or children of myocardial infarction survivors, or spouses of such relatives. All risk-ratio calculations allow for this relatedness of some of the controls. An updated meta-analysis of previous studies was also conducted.

FINDINGS

The ACE DD genotype was found in 1359 (29.4%) of the myocardial infarction cases and in 1637 (27.6%) of the controls (risk ratio 1.10 [95% CI 1.00-1.21]). The association between myocardial infarction and the DD genotype did not seem to be stronger in the subgroup defined as low risk by previously used criteria (234 [28%] of 836 cases and 911 [28%] of 3253 controls: risk ratio 1.04 [95% CI 0.87-1.24]), or in any other subgroup. Nor was the ACE I/D genotype predictive of subsequent survival.

INTERPRETATION

This study involved many more cases than any previously reported study of this question, but did not confirm the existence of any substantial association. In an updated meta-analysis of these results with those of previously published studies, the risk ratio for myocardial infarction with the DD genotype seems to lie in the range 1.0 to about 1.1. Although an increase in risk of up to about 10-15% cannot be ruled out, substantially more extreme risks can be. Moreover, there are not especially strong associations in the subgroups previously selected for emphasis. These findings illustrate the need for some studies of candidate genes to involve much larger populations than is customary, without undue emphasis on retrospectively defined subgroups.

[Genetic risk factors for myocardial infarct]

Interactions of genetic and environmental risk factors influence the susceptibility to coronary artery disease (CAD) and myocardial infarction. In myocardial infarction occurring at young age, genetics of this multifactorial disease may be the leading factor. A number of candidate genes have been implicated in the pathogenesis of CAD and myocardial infarction. Mutations in the DNA sequence (gene polymorphisms) have been identified that appear to play a crucial role in blood pressure regulation, lipid metabolism, endothelial function, in the pathophysiology of coagulation or thrombosis, or in interventional cardiology by interfering with restenosis development. Genetic polymorphisms seem to be clinically important because they not only potentiate the individual risk under certain circumstances, but they also determine safety and effectiveness of commonly prescribed drugs. Understanding the complexity and functional relevance of genetic risk factors will be useful in early detection and treatment of individuals that are exposed to higher risk for myocardial infarction. Thus it is important to include genetic risk factors in the concept of the classical risk factor theory. Potentially in future a genetic risk profile including relevant polymorphisms may be an essential part of the clinicians' knowledge in primary and secondary prevention of coronary artery disease.

Genetic risk factors and restenosis after percutaneous coronary interventions

Restenosis is the major limitation of percutaneous coronary interventions. Depending on the form of intervention and patients' characteristics, 20 to 50% of the treated patients incur significant restenosis. Restenosis is caused by a complex and only partially understood cascade of events. Thrombus formation at the injury site, formation of the neointima as a result of the migration and proliferation of smooth muscle cells (SMC) and extracellular matrix production, as well as constrictive remodeling of the vessel wall contribute by a variable degree to restenosis. Restenosis is not a random event but it affects selectively a certain subset of patients. These patients have some peculiar characteristics that help to identify the presence of a higher risk for restenosis. Conventional patient-related factors account only for a relatively small portion of the predictive power, much more contribution comes from lesion and procedural characteristics. There is increasing evidence that inherited factors may explain at least part of the excessive risk for restenosis observed in certain patients. Evidence exists that gene polymorphisms may lead to quantitative or functional alterations of the respective gene products. Recent studies have also found significant associations between several polymorphic alleles encoding for proteins with a relevant role in the process of lumen renarrowing and restenosis after percutaneous coronary interventions. The best studied polymorphisms in this regard are those of the genes encoding for angiotensin-converting enzyme and platelet glycoprotein-IIIa. Completed or ongoing studies have focused on polymorphisms of genes encoding for proteins interfering with lipid metabolism, hemostasis, nitric oxide production, inflammatory mechanisms, SMC proliferation and matrix production. The results of this research will have considerable pathophysiological and therapeutical implications for the battle against restenosis.

Pharmacogenetic analysis of the effect of angiotensin-converting enzyme inhibitor on restenosis after percutaneous transluminal coronary angioplasty

Angiotensin-converting enzyme (ACE) inhibitors are reported to prevent neointimal formation after balloon injury in animal models, but in most prospective studies in humans, ACE inhibitors failed to prevent restenosis after percutaneous transluminal coronary angioplasty (PTCA). The ACE genotype assigned by an insertion/deletion (I/D) polymorphism is known to affect the potency of ACE inhibitors in several renal diseases. The authors attempted to clarify whether the effect of ACE inhibitors on restenosis might be modified by the ACE genotype. A total of 126 patients was randomly and prospectively assigned to the control group and the imidapril group. In the imidapril group, patients received 5 mg imidapril daily, starting 1 day before PTCA and continuing for 3 to 6 months. Forty-six control (65 vessels) and 32 imidapril patients (43 vessels) completed the study. The minimal lumen diameter before and after the procedure did not differ significantly among the groups with the three genotypes (II, ID, and DD) in both the control and imidapril groups. Late luminal loss during the follow-up period was not related to the ACE genotype in the control group but was significantly related in the imidapril group (II, 0.63+/- 0.19 mm; ID + DD, 1.12+/-0.14 mm, p<0.05). Furthermore, in the II genotype, imidapril significantly reduced late loss and restenosis rate as defined by most of the frequently used definitions. In conclusion the ACE I/D polymorphism may influence the effect of ACE inhibitors in preventing restenosis after PTCA.

Elite athletes and the gene for angiotensin-converting enzyme

The deletion (D) allele of the gene for angiotensin-converting enzyme (ACE) is associated with higher plasma and tissue levels of the enzyme and has also been related to a variety of cardiovascular complications, particularly myocardial infarction. On the basis of indirect evidence, we hypothesized that inheritance of the D allele would contribute to elite athletic ability. Over a period of 4 yr, 120 Caucasian athletes who were national (Australian) representatives in sports demanding a high level of aerobic fitness were recruited. Their ACE genotypes were compared with those of a community control group recruited randomly from the electoral roll. There was no difference in ACE genotype frequencies between the two groups. The DD genotype frequency was 30% in athletes and 29% in the control group, and the II genotype frequency was 22.5 and 22%, respectively. The results do not exclude the possibility that ACE genotype could be related to some attribute relating to a specific type of elite athletic ability or that there may be a difference between genders. Larger studies are desirable.

PIa1/a2 polymorphism of glycoprotein IIIa and risk of coronary artery disease and restenosis following coronary angioplasty

Glycoprotein IIIa (GpIIIa), a platelet protein that mediates platelet aggregation and thrombus formation, has attained recent widespread interest following a report that a common genetic variant of GpIIIa, known as Pla2, is an inherited risk factor for the development of premature coronary artery disease (CAD). We determined the frequency of the Pla2 allele in 589 prospectively recruited subjects aged <50 years presenting with symptomatic CAD with or without myocardial infarction and documented by coronary angiography (group I), 207 subjects investigated prospectively for restenosis 6 months after coronary balloon angioplasty (group II), and 570 control subjects without a history of angina or myocardial infarction, randomly selected from the community. Detection of the Pla2 allele was based on MspI digestion of polymerase chain reaction (PCR) amplified deoxyribonucleic acid (DNA) spanning the Pla1/a2 locus. The accuracy of genotyping was verified with a second independent method based on BstXI digestion of DNA amplified with mutagenic PCR primers. The frequency of the Pla2 allele was similar (p >0.1) in group I (170 of 1,178, 14%), group II (49 of 414, 12%), and control subjects (160 of 1,140, 14%). Among group I subjects, there was no relation (p >0.1) between the Pla2 allele frequency and the number of coronary vessels with >50% diameter obstruction, and current or previous myocardial infarction; among group II subjects, there was no difference between those with and without restenosis after angioplasty (26 of 242 and 23 of 172, respectively, p >0.1). We conclude that the Pla2 allele is not associated with a significantly elevated risk of premature CAD, myocardial infarction, or restenosis after coronary angioplasty.

Apolipoprotein E polymorphism does not predict risk of restenosis after coronary angioplasty

A recent report has suggested that the E4 allele of apolipoprotein (apo) E increases the risk of restenosis after percutaneous transluminal coronary angioplasty (PTCA) and also that it interacts synergistically with the deletion (D) allele of the angiotensin-converting enzyme (ACE) to increase the risk sixteen-fold. To investigate this further, we genotyped 231 subjects with successful PTCA who underwent planned repeat angiography at 4 months to assess the degree of restenosis. Subjects carrying the apo E4 allele (n = 71) were well matched with non-carriers (n = 160) for clinical and pre- and post-PTCA angiographic features. We found no increase in either apo E4 allele frequency (18.4% versus 15.6%, P = 0.42) or apo E4 homozygosity (2/106 versus 5/125, P = 0.30) in those with restenosis compared with those without. The relative risk of restenosis for apo E4 carriers was 1.11 (95% CI = 0.87-1.42). In apo E4 carriers, restenosis frequency was similar in those also carrying the ACE D allele and those without (28/55 (50.9%) versus 9/16 (56.2%), P = 0.71) and there was no significant increase in restenosis risk in carriers of both the apo E4 and ACE D alleles compared to the rest (odds ratio 1.30, 95% CI 0.68-2.50, P = 0.39). We conclude that in our cohort, the apo E4 allele does not either independently or acting synergistically with the ACE D allele increase the risk of restenosis after PTCA, and that apo E genotyping will not be a useful predictor of risk before the procedure.