Effect of apoE genotype on the hypolipidaemic response to pravastatin in an outpatient setting

Genetic Determinants of Response to Statins in Cardiovascular Diseases

Despite extensive efforts to identify patients with cardiovascular disease (CVD) who could most benefit from the treatment approach, patients vary in their benefit from therapy and propensity for adverse drug events. Genetic variability in individual responses to drugs (pharmacogenetics) is considered an essential determinant in responding to a drug. Thus, understanding these pharmacogenomic relationships has led to a substantial focus on mechanisms of disease and drug response. In turn, understanding the genomic and molecular bases of variables that might be involved in drug response is the main step in personalized medicine. There is a growing body of data evaluating drug-gene interactions in recent years, some of which have led to FDA recommendations and detection of markers to predict drug responses (e.g., genetic variant in VKORC1 and CYP2C9 genes for prediction of drug response in warfarin treatment). Also, statins are widely prescribed drugs for the prevention of CVD. Atorvastatin, fluvastatin, rosuvastatin, simvastatin, and lovastatin are the most common statins used to manage dyslipidemia. This review provides an overview of the current knowledge on the pharmacogenetics of statins, which are being used to treat cardiovascular diseases.

The Association between Apolipoprotein E Polymorphism and Response to Statins in Group of Hyperlipidemic Patients

BACKGROUND AND OBJECTIVE

APOE has an important role in lipids metabolism, and in the variability in low density lipoprotein (LDL) response to statins treatment between individuals. In this study, we aim to investigate the association between APOE polymorphism and response to statins in Jordanian hyperlipidemic patients at the diabetic clinic of Jordan University Hospital.

METHODS

One hundred and fifty two Jordanian Hyperlipidemic patients (52 males and 100 females) aged between 35-75 years were enrolled in this study. This study was approved by the Institutional Review Board (IRB) of Jordan University Hospital. The genotypes of the patients were identified by polymerase chain reaction followed by restriction fragment length polymorphism assay method (PCRRFLP).

RESULTS AND CONCLUSION

The study showed that there is an association between APOE polymorphism and response to statin therapy. Patients who were APOE ε4 carriers had lower response to statins compared to ε3 and ε2 carriers (p=0.002). In addition, we found that there was no significant association between APOE polymorphism and LDL baseline (p=0.214). No significant differences were found in APOE genotypes distribution between males and females (p=0.06). No significant association was found between age and APOE genotypes (p=0.347). A genotype screening test for dyslipidemic Jordanian patients is recommended to choose the appropriate treatment decisions, dosage, and to recognize the potential side effects of statin therapy.

Laboratory Medicine in the Clinical Decision Support for Treatment of Hypercholesterolemia: Pharmacogenetics of Statins

Statin responsiveness is an area of great research interest given the success of the drug class in the treatment of hypercholesterolemia and in primary and secondary prevention of cardiovascular disease. Interrogation of the patient's genome for gene variants will eventually guide anti-hyperlipidemic intervention. In this review, we discuss methodological approaches to discover genetic markers predictive of class-wide and drug-specific statin efficacy and safety. Notable pharmacogenetic findings are summarized from hypothesis-free genome wide and hypothesis-led candidate gene association studies. Physiogenomic models and clinical decision support systems will be required for DNA-guided statin therapy to reach practical use in medicine.

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.

No change of the lipid profile under the control of ApoE gene polymorphism in schizophrenics under paliperidone treatment

The present study tried to explore the effects of Paliperidone on the lipid profiles of schizophrenia patients. One hundred twenty-nine subjects diagnosed with schizophrenia were enrolled into this study and completed the lipid profile evaluation. Their blood samples were obtained on the morning following a 12-hours fast. Cholesterol and triglyceride (TG) levels in plasma were determined, and lipoproteins were determined by enzymatic methods. All participants provided written informed consent, and underwent additional venous blood withdrawal for DNA extraction for genetic study of the ApoE gene polymorphism. Under T test, TC, TG and HDL levels all declined after Paliperidone treatment although with no statistically significant difference. The ratios of TC/HDL declined after Paliperidone treatment, but without statistically significant difference. After GEE-I analysis, we found that ApoE4 genotype (β = 34.471; p < 0.001) had a positive effect on the total cholesterol (TC) level; female had positive effect on the high-density lipoprotein (HDL) level (β = 15.361; p = 0.003); and age had a positive effect on the TG level (β = 1.317; p = 0.030). Smoking (β = 0.961; p = 0.016) had a positive effect on the ratio of TC/HDL change. Lipid profiles were not increased after Paliperidone treatment under the control of ApoE gene polymorphism.

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.

Apolipoprotein E mRNA expression in mononuclear cells from normolipidemic and hypercholesterolemic individuals treated with atorvastatin

Background

Apolipoprotein E (apoE) is a key component of the lipid metabolism. Polymorphisms at the apoE gene (APOE) have been associated with cardiovascular disease, lipid levels and lipid-lowering response to statins. We evaluated the effects on APOE expression of hypercholesterolemia, APOE ε2/ε3/ε4 genotypes and atorvastatin treatment in Brazilian individuals. The relationship of APOE genotypes and plasma lipids and atorvastatin response was also tested in this population.

Methods

APOE ε2/ε3/ε4 and plasma lipids were evaluated in 181 normolipidemic (NL) and 181 hypercholesterolemic (HC) subjects. HC individuals with indication for lowering-cholesterol treatment (n = 141) were treated with atorvastatin (10 mg/day/4-weeks). APOE genotypes and APOE mRNA in peripheral blood mononuclear cells (PBMC) were analyzed by TaqMan real time PCR.

Results

HC had lower APOE expression than NL group (p < 0.05) and individuals with low APOE expression showed higher plasma total and LDL cholesterol and apoB, as well as higher apoAI (p < 0.05). Individuals carrying ε2 allele have reduced risk for hypercholesterolemia (OR: 0.27, 95% I.C.: 0.08-0.85, p < 0.05) and NL ε2 carriers had lower total and LDL cholesterol and apoB levels, and higher HDL cholesterol than non-carriers (p < 0.05). APOE genotypes did not affect APOE expression and atorvastatin response. Atorvastatin treatment do not modify APOE expression, however those individuals without LDL cholesterol goal achievement after atorvastatin treatment according to the IV Brazilian Guidelines for Dyslipidemia and Atherosclerosis Prevention had lower APOE expression than patients with desirable response after the treatment (p < 0.05).

Conclusions

APOE expression in PBMC is modulated by hypercholesterolemia and the APOE mRNA level regulates the plasma lipid profile. Moreover the expression profile is not modulated neither by atorvastatin nor APOE genotypes. In our population, APOE ε2 allele confers protection against hypercholesterolemia and a less atherogenic lipid profile. Moreover, low APOE expression after treatment of patients with poor response suggests a possible role of APOE level in atorvastatin response.

The association of apolipoprotein E polymorphism and lipid levels in children with a family history of premature coronary artery disease

BACKGROUND

Polymorphisms in the apolipoprotein E (apoE) gene may modulate lipoprotein metabolism and influence plasma lipid levels. Thus, they have been associated with relative risk of coronary artery disease (CAD).

OBJECTIVE

To evaluate the association of apolipoprotein E polymorphism and lipid levels in children with family history of premature coronary artery disease.

METHODS

The apoE genotypes, allele frequencie,s and plasma lipid levels were analyzed in 137 children. Among these children, 70 (study group) had and 67 (control group) did not have a parental history of premature CAD RESULTS: Total cholesterol (Tc) levels were greater in the study group (P = .04). The frequencies of ɛ3ɛ4 genotype and ɛ4 allele were significantly greater in the study group (P = 005 for both), Thɛ ɛ2 allele correlated negatively with Tc and low-density lipoprotein cholesterol levels, and ɛ4 had a positive correlation with Tc and low-density lipoprotein cholesterol levels.

CONCLUSIONS

Tc levels are influenced by apoE genotypes in childhood. Also, the frequency of the ɛ4 allele is greater in children with family history of premature CAD. The ɛ4 allele may be associated with an increased risk for development of atherosclerosis by elevated levels of Tc in children with family history of CAD. The evaluation of apoE gene polymorhisms may contribute to the assessment of cardiovascular risk in children with a family history of CAD.

Noninvasive assessment of atherosclerosis in apolipoprotein-e knockout mice by ultrasound biomicroscopy

Intima media thickness is a marker for human atherosclerosis. This study aimed to validate the hypothesis that atherosclerosis progression in vivo in mice can be visualized noninvasively using high-resolution ultrasound biomicroscopy (UBM), and to study the association between UBM characteristics and plasma lipids in the apolipoprotein-E knockout (ApoE-/-) mouse model. Four age groups of male ApoE-/- mice were used as atherosclerotic models, with age-matched male C57BL/6 mice used as controls. Plaque thickness and area measured by UBM correlated with histologic measurements (r = 0.81, r = 0.70, respectively; p < 0.001). Serum total cholesterol, low density lipoprotein cholesterol and triglycerides were higher in the ApoE-/- groups compared with controls (p < 0.01). Plaque thickness was correlated with total cholesterol (r = 0.505, p < 0.001). High-resolution UBM provides a noninvasive, accurate means of detecting atherosclerosis progression in vivo in mice and can detect changes in the early stage of atherosclerosis.

Apolipoprotein E epsilon-4 polymorphism is associated with younger age at referral to a lipidology clinic and a poorer response to lipid-lowering therapy

Background

The risk of coronary heart disease (CHD) is related to environmental factors and genetic variants. Apolipoprotein E (apoE) polymorphisms are heritable determinants of total and low-density lipoprotein cholesterol, with some authors suggesting an association between the ε4 allele and CHD. We investigated the relationship between apoE genotype and age at referral to a specialized lipid clinic by the primary care physician and whether the benefits of treatment with statin differed between genotypes.

Methods

We assessed individual apoE genotypes and lipid blood profile in a total of 463 patients followed at a specialized lipid clinic due to dyslipidemia, with a 3-year median follow-up time. The primary care physician at the time of the referral had no access to the apoE genotyping results. Carriers of apoE ε4/ε2 genotype were excluded.

Results

The frequencies of ε2, ε3 and ε4 alleles were 7.8, 78.9 and 13.3%, respectively. There were no significant differences between genders. Although with similar lipid profiles and antidyslipidemic drug usage at baseline, ε4-carriers were referred to the clinic at a younger age (44.2 ± 14.7 years) compared with non-ε4 carriers (50.6 ± 13.8 years) (p < 0.001), with a substantially younger age of referral for homozygous E4/4 and for all genotypes with at least one copy of the ε4 allele (p < 0.001 for trend). Although both ε4 and non-ε4 carriers achieved significant reductions in total cholesterol during follow-up (p < 0.001 vs. baseline), the mean relative decrease in total cholesterol levels was higher in non-ε4 carriers (-19.9 ± 2.3%) compared with ε4 carriers (-11.8 ± 2.3%), p = 0.003.

Conclusion

Our findings support the concept that there is a reduced response to anti-dyslipidemic treatment in ε4 carriers; this can be a contributing factor for the earlier referral of these patients to our specialized lipid clinic and reinforces the usefulness of apoE genotyping in predicting patients response to lipid lowering therapies.

Clinical implications of pharmacogenetic variation on the effects of statins

The last decade has seen an increase in the trend of HMG-CoA reductase inhibitor (statin) usage in the Western world, which does not come as a surprise noting that the latest American Heart Association heart and stroke statistics indicate an alarming prevalence of 80  million Americans (one in three) with one or more forms of diagnosed cardiovascular disease (CVD). Meta-analysis of several large-scale, randomized clinical trials has demonstrated statins to be efficacious in significantly reducing CVD-associated mortality in both primary and secondary prevention. Despite their proven efficacy, statins have also gained attention with respect to adverse drug reactions (ADRs) of muscle myopathy, derangements in hepatic function and even ADRs classified as psychiatric in nature. The depletion of cholesterol within the myocyte cell wall and/or the depletion of key intermediates within the cholesterol synthesis pathway are hypothesized as possible mechanisms of statin-associated ADRs. However, pharmacogenetic variability may also be a risk factor for ADRs and can include, for example, enzymes, transporters, cell membrane receptors, intracellular receptors or components of ion channels that contribute to the pharmacokinetics or pharmacodynamics of response to a particular drug. The cytochrome P450 (CYP) enzymatic pathways that comprise the polymorphic genes, CYP2D6, CYP3A4 and CYP3A5, and also a hepatic transporter, solute carrier organic anion transporter (SLCO1B1), which is a single nucleotide polymorphism discovered to be associated with statin-induced myopathy through a genome-wide association study, are discussed with respect to their effect on altering the pharmacokinetic profile of statin metabolism. Variants of the Apolipoprotein E (APO-E) gene, polymorphisms in the cholesteryl ester transfer protein (CETP) gene, the HMG-CoA reductase gene and other proteins are discussed with respect to altering the pharmacodynamic profile of statins. Pharmacogenetics and its application in medicine to individualize drug therapy has been previously shown to be clinically and economically beneficial through quality-adjusted life-year assessment. Therefore, polymorphisms affecting the pharmacokinetic and pharmacodynamic profiles of statins, which are widely used in therapy, with their potential application in the personalized prescribing of statin therapy, need further research. In this review, we update the recent literature with respect to genetic polymorphisms that may influence the pharmacokinetics and pharmacodynamics of statin therapy, and consider the relevance of these findings to the efficacy of treatment, prevention of ADRs and what this may mean for patient tolerance and compliance.

Physiogenomic analysis of statin-treated patients: domain-specific counter effects within the ACACB gene on low-density lipoprotein cholesterol?

AIM

Administered at maximal dosages, the most common statins--atorvastatin, simvastatin and rosuvastatin--lower low-density lipoprotein cholesterol (LDLC) by an average of 37-57% in patients with primary hypercholesterolemia. We hypothesized novel genetic underpinnings for variation in LDLC levels in the context of statin therapy.

MATERIALS & METHODS

Genotyping of 384 SNPs in 202 volunteers from a lipid outpatient clinic was accomplished and LDLC levels obtained from chart records. The SNPs were distributed across 222 genes representing physiological pathways such as general metabolism, cholesterol biochemistry, cardiovascular function, inflammation, neurobiology and cell proliferation. We discovered significant associations with LDLC levels for the rs34274 SNP (p < 0.0002) and for rs2241220 (p < 0.008) in the acetyl-coenzyme A carboxylase beta (ACACB) gene. When corrected for multiple testing, the false-discovery rate associated with rs34274 was 0.076 (significance threshold: 0.10) and for rs2241220 the false-discovery rate was 0.93 (not significant). The acetyl coenzyme A carboxylase beta enzyme synthesizes malonyl coenzyme A, an essential substrate for hepatic fatty acid synthesis and an inhibitor of fatty acid oxidation.

RESULTS

The SNPs were in weak linkage disequilibrium (D = 0.302). Minor alleles at these sites demonstrate opposing influences on LDLC; the C>T substitution at rs34724 is a risk marker and the C>T substitution at rs2241220 a protective marker for LDLC levels. These SNPs hypothetically influence enzymatic activity through different mechanisms, rs34274 through the PII promoter and rs2241220 via alteration of the protein's responsiveness to allosteric influence.

CONCLUSION

Physiogenomic evidence suggests a novel link between LDLC levels and the regulation of fatty acid metabolism. The findings complement previously discovered novel SNP relationships to myalgia (pain) and myositis (serum creatine kinase activity). By genotyping for myositis, myalgia and LDLC levels, a physiogenomic model may be developed to help clinicians maximize effectiveness and minimize side effects in prescribing statins.

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.

Identification of genetic variants associated with response to statin therapy

OBJECTIVE

The purpose of this study was to test the association between polymorphisms in genes involved in either LDL cholesterol (LDL-C) metabolism or statin pharmacokinetics and LDL-C reduction with statins.

METHODS AND RESULTS

49 tagging and candidate polymorphisms in 9 genes were genotyped in 1507 post-ACS subjects randomized to atorvastatin or pravastatin. Two polymorphisms (rs7412, rs429358) that define the epsilon2, epsilon3, and epsilon4 isoforms of apolipoprotein E were significantly associated with percent reduction in LDL-C with atorvastatin (epsilon2 carriers 53.8%, epsilon3/epsilon3 48.1%, and epsilon4 carriers 46.4%, respectively, P=0.00039) and replicated in the pravastatin arm (epsilon2 carriers 22.1%, epsilon3/epsilon3 21.8%, and epsilon4 carriers 16.6%, respectively, P=0.00038). The proportion of subjects achieving an LDL-C < or =70 mg/dL at day 30 was higher for epsilon2 than epsilon4 carriers (P=1.3 x 10(-5)). In the pravastatin group, the triallelic rs2032582 variant (G2677T/A) in ABCB1 was associated with the percent reduction in LDL-C (GG 23.3%, non-G heterozygote 20.3%, and non-G homozygote 17.4%, P=0.042).

CONCLUSIONS

Carriers of APOE epsilon2 versus epsilon4 had significantly greater LDL-C reduction with atorvastatin and with pravastatin, and more frequently achieved a guideline-recommended LDL-C < or =70 mg/dL. Polymorphisms in triallelic G2677T/A variant in ABCB1 were associated with the degree of LDL-C lowering with pravastatin.

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.

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.

[Lack of association between the APOE genotype and the response to statin treatment in patients with acute ischemic episodes]

BACKGROUND AND OBJECTIVE

APOE genotype has been shown to have an influence on lipid concentrations. However, its relation with response to lipid-lowering treatment is not well established. The aim of our work was to analyze whether this genotype is associated with changes in the lipid profile in response to statins treatment.

PATIENTS AND METHOD

A total of 222 consecutive patients with acute ischemic episodes and subjected to treatment with statins were included in a retrospective study. The patients' lipid profile was determined at the first visit to the Lipids Unit and after one year on a statin regime. APOE genotypes were determined by PCR-RFLP, and separated in three groups: E2 (E2 carriers), E4 (E4 carriers) and E3 (E3/E3). E2/E4 patients were not included in the study.

RESULTS

Relative frequencies of alleles epsilon2, epsilon3 and epsilon4 were 10.5%, 70.9% and 18.6% respectively. Significant differences among groups (p = 0.039) were observed for c-LDL concentrations. E2 group had lower c-LDL than E3 group (p = 0.017) and E4 group (p = 0.01). No significant differences in c-LDL, c-HDL and c-HDL/CT were observed among the three groups with regard to variation after statin treatment.

CONCLUSION

APOE genotype does not significantly affect the lipid response in patients with acute ischemic episodes after statin treatment.

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.

Apolipoprotein E genotypes are associated with lipid-lowering responses to statin treatment in diabetes: a Go-DARTS study

BACKGROUND

Apolipoprotein E (APOE) genotypes have been associated with variations in plasma-lipid levels and with response to statins, although the influence of APOE on the response to statins remains controversial, especially in patients with diabetes. We sought to evaluate the association of the APOE genotype with the low-density lipoprotein cholesterol (LDLc)-lowering response to statins, in a large population-based cohort of patients with diabetes.

METHODS AND RESULTS

A total of 1383 patients, commencing statins between 1990 and 2006, were identified from the Genetics of Diabetes Audit and Research in Tayside Scotland database. Statin response was determined both by the minimum LDLc achieved, and by the failure of the patients to reach a clinical target LDLc (< or =2 mmol/l). APOE genotype and potential confounding covariates were entered into the linear and logistic regression models.

RESULTS

We found an association of APOE genotypes with both baseline and treatment responses. E2 homozygotes achieved lower LDLc levels (mean 0.6; confidence interval: 0.1-1.1 mmol/l) than E4 homozygotes (mean 1.7; confidence interval: 1.4-1.9 mmol/l; P=2.96 x 10). Minimum LDLc was associated by a linear trend with genotype. This relationship remained statistically significant after adjustment for baseline LDLc, adherence, duration, dose, smoking, and age. None of the E2 homozygotes failed to reach the target LDLc, compared with 32% of the E4 homozygotes (P=5.3 x 10).

CONCLUSION

This study demonstrates the potential clinical value of the APOE genotype as a robust marker for LDLc responses to statin drugs, which might contribute to the identification of a particularly drug-resistant subgroup of patients. This marker provides information over and above baseline lipid levels.

The effect of apolipoprotein E polymorphism on the response to lipid-lowering treatment with atorvastatin or fenofibrate

Although the effect of apolipoprotein E gene polymorphism on the response to treatment with statins has been studied, the results are conflicting. Moreover, little is known about the possible effect of apolipoprotein E alleles on the response to treatment with fibrates. The purpose of this study was to evaluate the effect of apolipoprotein E polymorphism on lipid-lowering response to treatment with atorvastatin and fenofibrate in patients with different types of dyslipidemia. The study population included 136 patients with heterozygous familial hypercholesterolemia (type IIA dyslipidemia) treated with atorvastatin (20 mg/day) and 136 patients with either primary hypertriglyceridemia (type IV dyslipidemia) or mixed hyperlipidemia (type IIB dyslipidemia) treated with micronized fenofibrate (200 mg/day). Overall, no significant associations were detected between apolipoprotein E genotype and response to treatment with atorvastatin. In patients treated with fenofibrate, significant associations were noted between apolipoprotein E genotype and changes in apolipoprotein B, apolipoprotein E and triglyceride levels. Specifically, in apolipoprotein E2, apolipoprotein E3, and apolipoprotein E4 individuals, apolipoprotein B reductions were 22%, 17%, and 8%, respectively (P = .003); apolipoprotein E reductions were 45%, 20%, and 15%, respectively (P = .006); whereas triglyceride reductions reached 53%, 36%, and 33%, respectively (P = .033). In conclusion, apolipoprotein E genotype had no significant effect on the response to treatment with atorvastatin in patients with heterozygous familial hypercholesterolemia, but in patients with primary hypertriglyceridemia or mixed hyperlipidemia, there was a clear association between apolipoprotein E genotype and response to treatment with fenofibrate.

Apolipoprotein E genotype affects the response to lipid-lowering therapy in Chinese patients with type 2 diabetes mellitus

OBJECTIVE

To evaluate the effect of apolipoprotein E (apoE) genotype on baseline lipid levels and the response to hydroxy-methyl glutaryl coenzyme A reductase inhibitors (statins) therapy in Chinese patients with type 2 diabetes mellitus (DM).

RESEARCH DESIGN AND METHODS

We consecutively recruited Chinese patients with type 2 DM requiring lipid-lowering therapy according to current guidelines. Patients were started on either simvastatin 10 mg daily or given an equivalent dose of lovastatin 20 mg. After 12 weeks of statin therapy, patients had fasting lipid profiles repeated. ApoE genotyping was performed by restriction fragment length polymorphism (RFLP).

RESULTS

Ninety-six patients were studied. The epsilon3/epsilon3 genotype was in 62.5%, epsilon2/epsilon3 and epsilon3/epsilon4, 16.7 and 20.8%, respectively. After adjusting for confounding variables, baseline total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) levels were significantly higher in those with epsilon3/epsilon4 compared with epsilon2/epsilon3 genotype (6.7 vs. 5.5 mm for TC, 4.5 vs. 3.6 mm for LDL-C; p = 0.015 and p = 0.025, respectively). With statin therapy, epsilon3/epsilon4 patients had significantly greater LDL-C lowering compared with epsilon2/epsilon3 patients (48 vs. 27.7%; p = 0.04). There was no gender difference in baseline lipid parameters or response to statin therapy.

CONCLUSIONS

ApoE genotype accounts for interindividual variability of baseline cholesterol levels, and response to statin therapy in Chinese patients with type 2 DM.

Pharmacogenetics of chronic cardiovascular drugs: applications and implications

Cardiovascular disease continues to be a tremendous worldwide problem, and drug therapy is a major modality to attenuate its burden. At present, conditions such as hypertension, dyslipidaemia and heart failure are pharmacologically managed with an empirical trial-and-error approach. However, it has been suggested that this approach fails to adequately address the therapeutic needs of many patients, and pharmacogenetics has been offered as a tool to enhance patient-specific drug therapy. This review outlines pharmacogenetic studies of common cardiovascular drugs, such as diuretics, beta-blockers, angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, statins and warfarin, ultimately highlighting considerations for future research and practice.

A Module Map Showing Interaction between Apolipoprotein E and Phospholipase A2 Polymorphism in Lipid Profiles

OBJECTIVE

Establish a possible conceptual relationship among Apo E and PLA2 polymorphism and lipid profiles.

METHODS

Five hundred subjects aged 65 to 74 years were randomly selected from a community in southern Taiwan to assess the relationship between Apo E and PLA2 polymorphisms and lipid profiles. Two hundred fifty-six participants agreed to have venous blood drawn for DNA studies.

RESULTS

By multiple linear regression, the PLA2 A2 allele showed a statistically significant influence on LDL-C (p = 0.0097), and the Apo epsilon2 allele showed a statistically significant influence on HDL-C (p = 0.0004), however, the interaction between the PLA2 A2 allele and the Apo epsilon2 allele was found to be significant in the blood fraction of HDL-C (p = 0.0388) and LDL-C (p = 0.0002). Decreasing HDL-C and increasing LDL-C were found when the PLA2 A2 and Apo epsilon2 allele co-existed.

CONCLUSION

The presence of a physiologic balance contributes significantly to homeostatic and compensatory responses regulating blood HDL-C and LDL-C profiles. A module map of the generation-control cycle and conditional activity among Apo E, PLA2, and lipid levels is presented, and both behaviours and biological perspectives under the consilience model may suggest a new approach to many kinds of complex disorders.

Pharmacogenetic study of apolipoprotein E, cholesteryl ester transfer protein and hepatic lipase genes and simvastatin therapy in Brazilian subjects

BACKGROUND

In recent years, one of the focuses of genetic investigation in cardiology has been to identify the genetic factors associated with variable response to statin treatment. Polymorphisms in apolipoprotein E (APOE), cholesteryl ester transfer protein (CETP) and hepatic lipase (LIPC), proteins with major roles in lipid metabolism and homeostasis have been shown associated with lipid-lowering drugs response.

METHODS

One hundred forty-six hypercholesterolemic patients of European descent were prospectively enrolled and treated with simvastatin 20 mg per day for over 6 months. Ninety-nine subjects completed the 6-month follow-up. Plasma lipids and lipoproteins were measured before and throughout the study. APOE (E*2, E*3 and E*4), LIPC-250A > G and CETP TaqIB genotypes were determined by PCR and restriction mapping.

RESULTS

After a 6-month follow-up, no differences among genotypes in the percentage variation in lipid and lipoprotein concentrations for APOE and LIPC SNPs were observed. After adjustment for covariates, CETP B2B2 homozygotes showed a greater HDL-cholesterol increase compared to B1B2 and B1B1 subjects (14.1% vs. 1.7% and 1.3%, P < 0.05, respectively).

CONCLUSION

Our study demonstrates that individual plasma HDL-cholesterol response to simvastatin is mediated, in part, by the CETP gene locus, with the B2 homozygotes having more benefit in HDL-C improvement than carriers of B1 allele.

Baseline levels of low-density lipoprotein cholesterol and lipoprotein (a) and the AvaII polymorphism of the low-density lipoprotein receptor gene influence the response of low-density lipoprotein cholesterol to pravastatin treatment

To investigate some individual and genetic factors that may influence the response of low-density lipoprotein cholesterol (LDL-C) to pravastatin treatment, we recruited 440 subjects with hypercholesterolemia (mean age, 57 years; 43% men) from 21 primary health care centers-outpatient clinics into a prospective, multicentered intervention trial. Pravastatin (20 mg/d) was prescribed for 16 weeks. The main outcome was the percentage variation in LDL-C concentration relative to baseline. Blood analyses and genotyping were performed centrally. The results indicated that LDL-C decreased by 20.5% (range, +21% to -66%) after pravastatin treatment. Baseline concentration of LDL-C (the higher the concentration, the greater the decrease), lipoprotein (a) levels (the lower the concentration, the greater the response), and Ava II polymorphism of the LDL-receptor gene significantly influenced the hypolipemic effect ( P < .001, P = .014, and P = .004, respectively). These 3 factors combined explained 10.6% of the variation in LDL-C response. Age, sex, smoking habit, alcohol consumption, body mass index, and apolipoprotein E genotype had no significant effect on response. We conclude that baseline levels of LDL-C and lipoprotein (a) together with the Ava II polymorphism of the LDL-receptor gene have a significant influence on the LDL-C response to pravastatin treatment in patients monitored in a standard primary health care outpatient clinic setting.

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.

HMG-CoA reductase inhibitor pharmacogenomics: overview and implications for practice

HMG-CoA reductase inhibitors (statins) are widely prescribed and recommended as first-line therapy for most patients with hypercholesterolemia or established coronary heart disease. However, there is interpatient variability in lipid-lowering response to statins that is not explained by initial cholesterol levels and inadequate dosing alone. Genetic polymorphisms may contribute. This review discusses the potential contribution of polymorphisms in genes encoding proteins involved in drug metabolism and transport, cholesterol biosynthesis, lipid metabolism and others to lipid responses to statins.

Pharmacogenetics of lipid diseases

The genetic basis for most of the rare lipid monogenic disorders have been elucidated, but the challenge remains in determining the combination of genes that contribute to the genetic variability in lipid levels in the general population; this has been estimated to be in the range of 40-60 per cent of the total variability. Therefore, the effect of common polymorphisms on lipid phenotypes will be greatly modulated by gene-gene and gene-environment interactions. This approach can also be used to characterise the individuality of the response to lipid-lowering therapies, whether using drugs (pharmacogenetics) or dietary interventions (nutrigenetics). In this regard, multiple studies have already described significant interactions between candidate genes for lipid and drug metabolism that modulate therapeutic response--although the outcomes of these studies have been controversial and call for more rigorous experimental design and analytical approaches. Once solid evidence about the predictive value of genetic panels is obtained, risk and therapeutic algorithms can begin to be generated that should provide an accurate measure of genetic predisposition, as well as targeted behavioural modifications or drugs of choice and personalised dosages of these drugs.

Haplotypes of the cholesteryl ester transfer protein gene predict lipid-modifying response to statin therapy

Cholesteryl ester transfer protein (CETP) plays a central role in high-density lipoprotein (HDL) metabolism. Single nucleotide polymorphisms (SNPs) and haplotypes in the CETP gene were determined in 98 patients with untreated dyslipidemias and analyzed for associations with plasma CETP and plasma lipids before and during statin treatment. Individual CETP SNPs and haplotypes were both significantly associated with CETP enzyme mass and activity. However, only certain CETP haplotypes, but not individual SNPs, significantly predicted the magnitude of change in HDL cholesterol (HDL-C) and triglycerides. After adjusting for covariates and multiple testing, the TTCAAA haplotype showed a gene-dose effect in predicting the HDL-C increase (P=0.03), while the TTCAAAGGG and AAAGGG haplotypes predicted a decrease in triglycerides (P=0.04 both). This is the first study to demonstrate that SNP haplotypes derived from allelic SNP combinations in the CETP gene were more informative than single SNPs in predicting the response to lipid-modifying therapy with statins.

Adherence to and dosing of beta-hydroxy-beta-methylglutaryl coenzyme A reductase inhibitors in the general population differs according to apolipoprotein E-genotypes

Discontinuation and poor adherence to therapy are major problems during long-term treatment, particularly with cholesterol lowering drugs. Several studies have indicated that the cholesterol lowering effect of statins differs according to apolipoprotein (apo)E genotypes. Low-density lipoprotein-cholesterol lowering capacity appears to be smaller in subjects with the epsilon(4) allele. To assess whether the use of statins in daily practice differs according to apoE genotypes, we used data from the Rotterdam Study, a population-based prospective cohort study in the Netherlands, which started in 1990 and included 7983 subjects aged 55 years or more. During follow-up, there were 798 subjects who started to use statins. We used a Cox proportional hazard model to determine the rate of discontinuation in the first 3 years of statin use. Subjects on statin therapy with epsilon(2)epsilon(2) and epsilon(4)epsilon(4) genotypes showed a trend towards higher dosages than subjects with the other genotypes. Relative to subjects with the epsilon(2)epsilon(3) genotype, those with the epsilon(4)epsilon(4) genotype had a risk of 2.28 [95% confidence interval (CI) 1.02-5.12] to discontinue statins within 3 years. In women, this relative risk was 1.70 (CI 0.53-5.42) versus 3.18 (CI 1.01-10.03) in men. The apoE genotype is associated with discontinuation of statins. This suggests that subjects who are genetically prone to develop hypercholesterolemia show the highest risk of discontinuation of treatment.

Apolipoprotein and apolipoprotein receptor genes, blood lipids and disease

PURPOSE OF REVIEW

Apolipoproteins and their receptors are the main controllers of lipid metabolism and, as such, have a major impact not only on the risk of cardiovascular disease but also on the development and degeneration of the central nervous system. Variations in the genes coding for these apolipoproteins and their receptors and the interaction with the environment determine individual susceptibility to metabolic disturbances, the response to dietary or pharmacological intervention and, finally, to disease.

RECENT FINDINGS

This review will focus on recent findings, such as the latest concepts regarding apolipoprotein E in neurodevelopment, the newly identified apolipoprotein A-V and its influence in triglyceride metabolism, and the improved understanding of apolipoprotein A-I and HDL metabolism in the light of the discovery of the ABC family of transporters. Other key aspects of lipoprotein metabolism and cardiovascular disease risk such as apolipoprotein B-100, the LDL receptor, apolipoprotein C-III or apolipoprotein (a) will be updated.

SUMMARY

Variations in these genes will be analysed in relation to plasma lipid levels, their interactions with diet, treatment or other environmental stimuli, and their influence on the risk of cardiovascular disease and neurological disorders.

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

We aimed to assess whether the effectiveness of statins in the prevention of myocardial infarction, stroke and total mortality is influenced by apolipoprotein E (apoE) genotype in an elderly population. We used data from the Rotterdam Study, a prospective population-based cohort study in the Netherlands which started in 1990 and included 7983 subjects aged 55 years and older. Subjects who were treated with cholesterol lowering drugs at baseline or with a serum total cholesterol > or = 6.5 mmol/l at baseline were included. We compared the incidence of myocardial infarction, stroke and total mortality in subjects who received > or = 2 years of statin treatment with that in subjects who had been treated for less than 2 years, and in untreated subjects, using a Cox proportional hazard model with cumulative statin use defined as time-dependent covariates. The adjusted relative risk of all-cause mortality was 0.79 [95% confidence interval (CI) 0.51-1.22] and of myocardial infarction and stroke 0.50 (95% CI 0.28-0.91) for subjects treated with statins for > or = 2 years compared to untreated subjects. The adjusted relative risks for subjects with the epsilon4 allele were 0.91 (95% CI 0.45-1.84) for all-cause mortality and 0.63 (95% CI 0.23-1.78) for myocardial infarction and stroke. In subjects without the epsilon4 allele, adjusted relative risks were 0.71 (95% CI 0.41-1.24) for all-cause mortality and 0.46 (95% CI 0.22-0.95) for myocardial infarction and stroke. We found a protective effect of statins on the risk of myocardial infarction and stroke that was independent of apoE genotype. The protective effect of statins on total mortality was not statistically significant, but did not seem to differ between subjects with different apoE genotypes.