Absence of an interaction between the angiotensin-converting enzyme insertion-deletion polymorphism and pravastatin on cardiovascular disease in high-risk hypertensive patients: the Genetics of Hypertension-Associated Treatment (GenHAT) study

Seventeen years of statin pharmacogenetics: a systematic review

AIM

We evaluated the evidence of pharmacogenetic associations with statins in a systematic review.

METHODS

Two separate outcomes were considered of interest: modification of low-density lipoprotein cholesterol (LDL-C) response and modification of risk for cardiovascular events.

RESULTS

In candidate gene studies, 141 loci were claimed to be associated with LDL-C response. Only 5% of these associations were positively replicated. In addition, six genome-wide association studies of LDL-C response identified common SNPs in APOE, LPA, SLCO1B1, SORT1 and ABCG2 at genome-wide significance. None of the investigated SNPs consistently affected the risk reduction for cardiovascular events.

CONCLUSION

Only five genetic loci were consistently associated with LDL-C response. However, as effect sizes are modest, there is no evidence for the value of genetic testing in clinical practice.

Characteristics associated with informed consent for genetic studies in the ACCORD trial

BACKGROUND

Prior studies found that some groups have lower genetic consent rates than others. Participant consent for genetic studies enables randomized trials to examine effects of interventions compared to control in participants with different genotypes.

METHODS

Unadjusted and multivariate associations between genetic consent rates and participant, study, and consent characteristics in 9573 participants approached for genetics consent in the multicenter Action to Control Cardiovascular Risk in Diabetes (ACCORD) trial, which used a layered genetics consent.

RESULTS

Eighty-nine percent of eligible participants consented to genetic studies ("Any Consent") and 64.7% consented to studies of any genes by any investigator ("Full Consent"), with similar rates in randomized groups. Controlling for multiple characteristics, African-Americans had lower consent rates than others (Any Consent Odds Ratio, OR = 0.62, p = 0.0004; Full Consent OR = 0.67, p < 0.0001). Those with high school or higher education level had higher rates than less than high school graduates (Full Consent ORs 1.41-1.69, p-values < 0.0001). Consent rates were lower when genetics consent was separate from the main trial consent on the same day (Any Consent OR 0.30; Full Consent OR 0.52, p values < 0.0001) or on a subsequent day (Any Consent OR 0.70, p = 0.0022; Full Consent OR 0.76, p = 0.0002).

CONCLUSION

High rates of consent for genetic studies can be obtained in complex randomized trials, with lower consent rates in African-Americans, in participants with less than high-school education, and for sharing samples with other investigators. A genetics consent separated from the main trial consent was associated with lower consent rates.

Review of the cost effectiveness of pharmacogenetic-guided treatment of hypercholesterolaemia

Hypercholesterolaemia is a highly prevalent condition that has major health and cost implications for society. Pharmacotherapy is an important and effective treatment modality for hypercholesterolaemia, with 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors ('statins') the most commonly used class of drugs. Over the past decade, there has been intensive research to identify pharmacogenetic markers to guide treatment of hypercholesterolaemia. This study aimed to review the evidence of incremental cost, effect and cost effectiveness of pharmacogenetic-guided treatment of hypercholesterolaemia. Three cost-effectiveness analyses (CEAs) were identified that studied the value of screening for genotypes of angiotensin I converting enzyme (ACE), cholesteryl ester transfer protein (CETP), and kinesin family member 6 (KIF6) prior to initiating statin therapy. For all three CEAs, a major limitation identified was the reproducibility of the evidence supporting the clinical effect of screening for the pharmacogenetic marker. Associated issues included the uncertain value of pharmacogenetic markers over or in addition to existing approaches for monitoring lipid levels, and the lack of evidence to assess the effectiveness of alternative therapeutic options for individuals identified as poor responders to statin therapy. Finally, the economic context of the market for diagnostic tests (is it competitive or is there market power?) and the practicality of large-scale screening programmes to inform prescribing in a complex and varied market may limit the generalizability of the results of the specific CEAs to policy outcomes. The genotype of solute carrier organic anion transporter family member 1B1 (SLCO1B1) has recently been associated with increased risk of muscle toxicity with statin therapy and the review identified that exploration of cost effectiveness of this pharmacogenetic marker is likely warranted.

Gene-drug interaction in stroke

Stroke is the third cause of mortality and one of most frequent causes of long-term neurological disability, as well as a complex disease that results from the interaction of environmental and genetic factors. The focus on genetics has produced a large number of studies with the objective of revealing the genetic basis of cerebrovascular diseases. Furthermore, pharmacogenetic research has investigated the relation between genetic variability and drug effectiveness/toxicity. This review will examine the implications of pharmacogenetics of stroke; data on antihypertensives, statins, antiplatelets, anticoagulants, and recombinant tissue plasminogen activator will be illustrated. Several polymorphisms have been studied and some have been associated with positive drug-gene interaction on stroke, but the superiority of the genotype-guided approach over the clinical approach has not been proved yet; for this reason, it is not routinely recommended.

Correlation between common genetic variants and risk factors associated with prediction of cardiovascular diseases in dyslipidemic patients

AIMS

The aim of the study was to investigate genetic variants predicting cardiovascular events in patients with dyslipidemia and compare its relationship with common risk factors including hyperlipidemia, metabolic syndrome, history of acute myocardial infarction, thrombosis, obesity, and smoking.

MATERIALS AND METHODS

Five hundred two individuals divided into six groups corresponding with the risk factors and a control group of normolypidemic patients were analyzed for the presence of eight mutations and polymorphisms (endothelial nitric oxide synthase -786T → C and G894T; lymphotoxin A C804A; angiotensin-converting enzyme [ACE] ins/del; human platelet antigen 1 a/b; beta-fibrinogen -455G → A; apolipoprotein B [ApoB] R3500Q; APOE E2/E3/E4) using the ViennaLab CVD Strip assay.

RESULTS

ACE deletions are the most frequent genetic variants in risk groups of dyslipidemic patients (from 58% in cardiovascular events to 51% in smokers). We found a strong relationship between genetic variants and risk factors. G894T is significantly associated with smoking (value of odds ratio [OR] = 1.62, p = 0.04), and ACE deletions are negatively associated with cardiovascular events (OR = 0.62, p = 0.03).

CONCLUSION

Significant associations between genetic variants predicting cardiovascular events and common risk factors in dyslipidemic patients were found.

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.

Pharmacogenetics of cardiovascular drug therapy

In developed countries cardiovascular disease is one of the leading causes of death. Cardiovascular drugs such as platelet aggregation inhibitors, oral anticoagulants, antihypertensives and cholesterol lowering drugs are abundantly prescribed to reduce risk of cardiovascular disease. Notable interindividual variation exists in the response to these pharmacotherapeutic interventions, which can be partially explained by factors such as gender, age, diet, concomitant drug use and environmental factors. Notwithstanding, a great part of this variability remains unknown. To a smaller or larger extent, genetic variability may contribute to the variability in response to these cardiovascular drugs. This review gives an overview of pharmacogenetic studies of genes that were reported to be associated with four commonly prescribed drugs/drug classes (platelet aggregation inhibitors, coumarins, antihypertensives and statins) and were studied at least 2 times with a similar outcome measure. In the field of cardiovascular drug therapy, polymorphisms in candidate genes such as the cycloxygenase-1, vitamin K reductase complex subunit 1, CYP2C9, alpha adducin and 3-hydroxy-3-methylglutaryl-CoA reductase have received a great amount of interest in the pharmacogenetics of aspirin, coumarins, antihypertensives and statins respectively. However, only variations in VKORC1 and CYP2C9 have consistently been associated with drug response (coumarins) and have clinical implications. Clinical trials should provide evidence for the effectiveness of genotyping before this procedure will be a part of every day anticoagulant therapy. In spite of the tremendous amount of publications in this field, there is no reason to advocate for genetic testing for any other drugs cardiovascular drug therapy yet. Current approaches in pharmacogenetic research do not seem to lead to results that meet our expectations of individualized medicine. Therefore, new approaches are needed addressing issues and challenges such as the number of SNPs studied, study power, study design and application of new statistical methods in (pharmaco-)genetic analysis.

Impact of genetic polymorphisms on the efficacy of HMG-CoA reductase inhibitors

Although pharmacologic treatment for cholesterol reduction represents an advance in cardiovascular and atherosclerosis treatment, the benefits of such therapy are still limited because of interindividual variability in the response to these drugs. Disease severity, treatment adherence, physiologic conditions, biologic conditions, and the patient's genetic profile could be cited as important factors in the evaluation of interindividual variability. In regard to the latter consideration, three large groups of genes could be investigated: (i) genes that code for proteins involved in metabolism and/or drug transport, thereby influencing the pharmacokinetics of these compounds; (ii) genes that code for proteins involved in the mechanism of action and/or in the metabolic pathway of drug action, and which therefore influence pharmacodynamics; and (iii) genes that code for proteins involved in direct development of the disease or in intermediate phenotypes. In this review we discuss pharmacogenetic studies of the HMG-CoA reductase inhibitors (statins) and the implications of pharmacogenetic considerations for predicting treatment efficacy and reducing the adverse effects of these drugs. Once new studies have been performed and most of the genetic variability associated with drug action has been revealed, the great challenge will be to apply this knowledge in clinical medicine.

Pharmacogenomic importance of pravastatin

In developed countries, cardiovascular disease is one of the leading causes of death. Among other statins, pravastatin is abundantly prescribed to reduce risk of coronary artery disease by lowering cholesterol. Genetic factors are thought to be partly responsible for the interindividual variation in the response to pravastatin. This article reviews the most important studies conducted on the pharmacogenetics of pravastatin. Currently there is no evidence to advocate pharmacogenetic testing before initiating therapy.

Pharmacogenomics of statin response

PURPOSE OF REVIEW

Although statin therapy has been shown to reduce substantially the risk for cardiovascular disease in multiple patient subgroups, there is wide inter-individual variation in statin efficacy, in terms of both plasma lipoprotein response and clinical outcome.

RECENT FINDINGS

A number of studies have reported that polymorphisms in genes affecting statin pharmacodynamics and pharmacokinetics are associated with measures of statin efficacy, but the magnitude of variation in statin response that could be explained by these associations is small. Genome-wide association studies may yield a more comprehensive set of markers for predicting statin efficacy and muscle toxicity. For the results of these analyses to have clinical value, however, there remains a need to replicate findings in multiple populations, to connect effects on LDL and other biomarkers with clinical outcomes, and to determine whether the associations apply to each individual statin.

SUMMARY

Satisfying these requirements for clinical applicability will be challenging, but discovery of specific genotypes that influence statin efficacy and characterization of their functional effects in cellular or animal model systems may enhance our understanding of determinants of cardiovascular disease risk. They may also allow us to identify pathways that may be targeted to yield effective prevention and treatment.

ACE genotype, risk and causal relationship to stroke: Implications for treatment

The angiotensin-converting enzyme (ACE) catalyzes the formation of angiotensin II and the breakdown of bradykinin into inactive products. The insertion/deletion (I/D) polymorphism affects the activity of the enzyme, with the DD genotype being responsible for the highest activity of the enzyme. Meta-analysis of 11 studies including white persons showed that the DD genotype was a risk factor for ischemic stroke. No such correlation was found in an Asian population. Studies on different etiologies or intermediate phenotypes of ischemic stroke did not bring univocal results. There are still no convincing data on whether the I/D polymorphism of the ACE gene is a risk factor for spontaneous intracerebral hemorrhage and intracranial aneurysms, ruptured or unruptured. Several pharmacogenetic studies analyzed the influence of the ACE I/D polymorphism on the response to acute stroke therapy (thrombolysis) or prevention strategies (lifestyle modification and treatment of vascular risk factors). Presently, however, there is no consensus on whether the efficacy of these therapies is affected by the ACE gene I/D polymorphism.