The effectiveness of hydroxy-methylglutaryl coenzyme A reductase inhibitors (statins) in the elderly is not influenced by apolipoprotein E genotype

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.

In search for genetic determinants of clinically meaningful differential cardiovascular event reduction by pravastatin in the PHArmacogenetic study of Statins in the Elderly at risk (PHASE)/PROSPER study

BACKGROUND

Statin therapy is widely used in the prevention and treatment of cardiovascular events and is associated with significant risk reductions. However, there is considerable variation in response to statin therapy both in terms of LDL cholesterol reduction and clinical outcomes. It has been hypothesized that genetic variation contributes importantly to this individual drug response.

METHODS AND RESULTS

We investigated the interaction between genetic variants and pravastatin or placebo therapy on the incidence of cardiovascular events by performing a genome-wide association study in the participants of the PROspective Study of Pravastatin in the Elderly at Risk for vascular disease--PHArmacogenetic study of Statins in the Elderly at risk (PROSPER/PHASE) study (n = 5244). We did not observe genome-wide significant associations with a clinically meaningful differential cardiovascular event reduction by pravastatin therapy. In addition, SNPs with p-values lower than 1 × 10(-4) were assessed for replication in a case-only analysis within two randomized placebo controlled pravastatin trials, CARE (n = 711) and WOSCOPS (n = 522). rs7102569, on chromosome 11 near the ODZ4 gene, was replicated in the CARE study (p = 0.008), however the direction of effect was opposite. This SNP was not associated in WOSCOPS. In addition, none of the SNPs replicated significantly after correcting for multiple testing.

CONCLUSIONS

We could not identify genetic variation that was significantly associated at genome-wide level with a clinically meaningful differential event reduction by pravastatin treatment in a large prospective study. We therefore assume that in daily practice the use of genetic characteristics to personalize pravastatin treatment to improve prevention of cardiovascular disease will be limited.

Pharmacogenetics of statins: achievements, whole-genome analyses and future perspectives

Statins are the most commonly prescribed class of drug worldwide and therapy is highly effective in reducing low-density lipoprotein cholesterol levels and cardiovascular events. However, there is large variability in clinical response to statin treatment. Recent research provides evidence that genetic variation contributes to this variable response to statin treatment. Until recently, pharmacogenetic studies have used mainly candidate gene approaches to investigate these effects. Since candidate gene studies explain only a small part of the observed variation and results have often been inconsistent, genome-wide association (GWA) studies may be a better approach. In this paper the most important candidate gene studies and the first published GWA studies assessing statin response are discussed. Moreover, we describe the PHASE study, an EU-funded GWA study that will investigate the genetic variation responsible for the variation in response to pravastatin in a large randomized clinical trial.

Effect of apolipoprotein E polymorphism on statin-induced decreases in plasma lipids and cardiovascular events

Hypercholesterolemia or dyslipidemia is an independent risk factor for cardiovascular disease and statins (inhibitors of a key enzyme of cholesterol synthesis, 3-hydroxymethyl glutaryl coenzyme A reductase) are the drugs of choice for decreasing plasma cholesterol. It has been estimated that genetic factors can explain 40%-60% of final cholesterol concentrations and approximately 70% of the efficacy of statin treatment. The gene most often analyzed in the context of statin efficacy is the gene for apolipoprotein E (APOE). This review summarizes evidence of the association between variations in the APOE gene locus and the response of plasma lipids to statin therapy. Although the results are not consistent, carriers of the APOE4 allele seems to be less responsive to statins than carriers of APOE2 and APOE3 alleles. This effect is partially context-dependent (gene-gender interactions; gene-nutrition and gene-smoking interactions have not yet been studied) and the absolute differences vary between different population groups.

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.

Genetic determinants of response to statins

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

APOE gene polymorphisms and response to statin therapy

Published studies investigating the role of APOE gene on lipid response (total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C) and triglycerides) to statin treatment have reported inconsistent results. A meta-analysis was conducted to estimate the lipid response to statin treatment among APOE genetic variants (e2 carriers, e3e3 homozygotes and e4 carriers). Twenty-four studies were included in the meta-analyses. The pooled mean reduction (Delta mu) in TC from baseline was significant for all variants (e2 carriers: Delta mu=-27.7% (-32.5 to -22.8%), e3e3: Delta mu=-25.3% (-28.0 to -22.6%) and e4 carriers: Delta mu=-25.1% (-29.3 to -21.0%)). Significant changes in LDL-C, HDL-C and triglyceride levels were also noted for all genotypes, although these changes did not differ significantly among genotypic groups. There was significant heterogeneity among the studies. Given these non-significant effects of APOE genotypes on lipid responses, there is little reason to consider the use of APOE genetic testing for guiding treatment with statins.

Pharmacogenetics of apolipoprotein E gene during lipid-lowering therapy: lipid levels and prevention of coronary heart disease

A non-optimal plasma concentration of lipids is among the major modifiable risk factors of atherosclerosis. Therefore, the prevention of cardiovascular disease by means of lipid-lowering therapy with statins and other agents is of great importance for patient groups where a lifestyle change, for example, diet modification, does not lead to adequately reduced lipid levels. The response of low-density-lipoprotein cholesterol (LDL-C) levels to statin therapy is highly variable. This is partly attributed to hereditary variation in genes involved in pharmacokinetics, pharmacodynamics and lipid metabolism. The pharmacogenetics of lipid-lowering therapy have been investigated for more than 40 different genes. The gene for apolipoprotein E (APOE) has been the most frequently studied, particularly regarding the epsilon2/epsilon3/epsilon4 polymorphism. Those with the epsilon4 allele seem to have the poorest and those with the epsilon2 allele the strongest response to statins with regards to LDL-C levels. In addition, the epsilon2 carriers may reach the LDL-C treatment goals more frequently than epsilon4 carriers. Few studies have investigated the interaction of the APOE epsilon2/epsilon3/epsilon4 polymorphism and lipid-lowering therapy in relation to the course of coronary heart disease; the results are contradictory and so far inconclusive. This review summarizes the pharmacogenetic findings related to the influence of APOE gene variation on lipid responses and the prevention of coronary heart disease during lipid-lowering therapy.

Pharmacogenetics of response to statins: Where do we stand?

Cardiovascular disease is one of the leading causes of death, especially in developed countries. Blood cholesterol lowering by way of statin therapy is a common risk-lowering therapy. The risk reduction for coronary artery disease for patients using statins is 27%. These reductions, however, are average effects for all patients included in the trials. There is notable interindividual variation in response to statins, and the origins of this variation are poorly understood. Pharmacogenetics seeks to determine the role of genetic factors in variation of drug response. In patients with primary hypercholesterolemia, 23 studies have examined the effects of genetic polymorphisms at 20 different loci on the lipid response to statin treatment, and 18 studies examined genetic polymorphisms involved in the benefits of statin therapy in the prevention of cardiovascular disease. Even though many studies have been performed, few results have been replicated. It is our contention that larger sample sizes and consideration of multiple genes are needed in the field of pharmacogenetics of statin response.

Pharmacogenetics of HMG-CoA reductase inhibitors: exploring the potential for genotype-based individualization of coronary heart disease management

Despite the benefit of statin therapy in the prevention of coronary heart disease, a considerable inter-individual variation exists in its response. It is well recognized that genetic variation can contribute to differences in drug disposition and, consequently, clinical efficacy at the population level. Pharmacogenetics, exploring genetic polymorphisms that influence response to drug therapy, may one day allow the clinician to customize treatment strategies for patients in order to improve the success rate of drug therapies. To date, 41 studies have investigated the relationships between common genetic variants and response to statin therapy in terms of lipid effects and clinical outcomes; 16 candidate genes involved in lipoprotein metabolism and 3 in pharmacokinetics. APOE is the most extensively studied locus, and absolute difference in LDL cholesterol reduction across genotypes remained 3-6%. Moreover, none of the associations was striking enough to justify genetic analysis in clinical practice. Reported data have suggested that larger studies (>1000 participants) or combination analyses with >2 different polymorphisms would enable us to find clinically or biologically meaningful difference, which could be assumed as >10% absolute difference, and that genes influencing cholesterol biosynthesis in the liver, such as ABCG5/G8, CYP7A1, HMGCR, would be good candidates for future studies.

The key role of apolipoprotein E in atherosclerosis

Apolipoprotein E is a multifunctional protein that is synthesized by the liver and several peripheral tissues and cell types, including macrophages. The protein is involved in the efficient hepatic uptake of lipoprotein particles, stimulation of cholesterol efflux from macrophage foam cells in the atherosclerotic lesion, and the regulation of immune and inflammatory responses. Apolipoprotein E deficiency in mice leads to the development of atherosclerosis and re-expression of the protein reduces the extent of the disease. This review presents evidence for the potent anti-atherogenic action of apolipoprotein E and describes our current understanding of its multiple functions and regulation by factors implicated in the pathogenesis of cardiovascular disease.

Genetically defined hyperlipidemia

The unraveling of genetic defects associated with disorders in lipid metabolism has contributed to the understanding of lipoprotein metabolism and the pathophysiological consequences of a particular mutation. The translation, however, of a single genetic defect into the individual's risk of cardiovascular disease and subsequent treatment strategies is an extremely complex issue that involves the identification of multiple additional determinants, including genetic, metabolic and environmental factors. The discovery of these factors, including genetic determinants of drug efficacy, provides insight into the interaction between regulatory systems traditionally thought to be unrelated and may, in the future, lead to a more complete diagnostic and therapeutic appreciation of the individual patient.