Apolipoprotein E polymorphism affects the response to pravastatin on plasma apolipoproteins in diabetic patients

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.

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.

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 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.

Obesity and alcohol modulate the effect of apolipoprotein E polymorphism on lipids and insulin

OBJECTIVE

To assess the interaction between apolipoprotein (apo) E polymorphism, alcohol consumption, and BMI on insulin, lipid, and lipoprotein levels in men.

RESEARCH METHODS AND PROCEDURES

Cross-sectional study of 266 healthy men without hypolipidemic or antidiabetic drug treatment. BMI, apo E polymorphisms, insulin, and lipid and lipoprotein levels were assessed. Alcohol consumption was assessed by questionnaire. epsilon2/epsilon4 carriers were excluded from the analysis.

RESULTS

On bivariate analysis, epsilon2 carriers had lower levels of total and low-density lipoprotein cholesterol and higher levels of apo E and lipoparticle B:E than epsilon3 carriers, the opposite being found for epsilon4 carriers compared with epsilon3 carriers; epsilon4 carriers also had significantly higher insulin levels. On multivariate analysis, significant interactions (p < 0.04) between apo E alleles and increased BMI were found for total and low-density lipoprotein cholesterol and insulin levels, the increase in those parameters with BMI being stronger among epsilon4 carriers than among epsilon3 or epsilon2 carriers. Significant interactions (p < 0.02) between apo E alleles and alcohol consumption were also found for apo B levels, which increased in epsilon2 carriers but remained relatively stable in epsilon3 and tended to decrease in epsilon4 carriers.

DISCUSSION

These data suggest that effects of apo E alleles on lipids and insulin levels are partly dependent on environmental variables such as BMI and alcohol intake. These findings highlight the importance of gene x environment interactions on the deleterious effect of obesity on cardiovascular risk factors.

Effect of apolipoprotein E alleles and angiotensin-converting enzyme insertion/deletion polymorphisms on lipid and lipoprotein markers in middle-aged men and in patients with stable angina pectoris or healed myocardial infarction

The effects of the apolipoprotein E epsilon and angiotensin-converting enzyme insertion/deletion alleles on lipid levels and hypolipidemic drug treatment was assessed in 400 men with stable angina pectoris or healed myocardial infarction and 338 healthy controls. The data indicate that epsilon4 carriers have increased total and low-density lipoprotein cholesterol levels, that the epsilon4 allele unfavorably decreases the efficiency of statin treatment, and that the angiotensin-converting enzyme insertion/deletion polymorphism exerts no significant effect, with the exception of an increase in apolipoprotein E levels.

Pharmacogenomics of drugs affecting the cardiovascular system

The variability in drug response originates partly from genetics, with possible consequences for drug efficacy, adverse effects, and toxicity. Until now, pharmacogenetics mainly indicated the best known source of variability, that is, the variability caused by drug metabolism. However, simultaneous progress in the knowledge of biochemical targets of drugs and of the human genome, together with the development of new technologies, revealed many new sources of human genetic variation, e.g., in receptors or transporters. Drugs are metabolized by various polymorphic phase I enzymes, including cytochromes P450 (CYP). Among them, the most relevant for the metabolism of cardiovascular drugs are CYP3A4, CYP2C9 or CYP2C19, and CYP2D6. The role of phase II enzymes is limited with regard to cardiovascular drugs biotransformation, but some polymorphisms (glutathion-S-transferase; GSH-T) are linked to cardiovascular risk. Phase III proteins or transporters, especially from the ABC family, must also be considered, as their polymorphisms affect cholesterol and other sterols transport. Among pharmacological targets, some proteins were identified as involved in interindividual variations in the response to cardiovascular drugs. Some examples are apolipoprotein E, angiotensin-converting enzyme, and the beta-adrenergic receptor. From the risk concept emphasizing impaired metabolism and adverse effects, we now moved to an approach, which is a personalized, genotype-dependent adaptation of therapy.

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

BACKGROUND

Considerable variability exists in the plasma lipid and lipoprotein response to statin treatment due, in part, to genetic factors. The gene for apolipoprotein E (ApoE) is polymorphic and the different genotypes modulate baseline lipid levels. The objective of the present study was to evaluate the effect of the apoE genotype on the lipoprotein response to pravastatin treatment in an outpatient population followed-up in several different clinics across Spain. Subjects and methods. Subjects (n=401; 56% female; mean age 57 years), who were hypercholesterolaemic despite a diet poor in saturated fat and cholesterol, were treated according to NCEP-ATP II guidelines. Plasma lipids and lipoproteins were measured centrally before and after 16 weeks of treatment with 20 mg day-1 of pravastatin.

RESULTS

ApoE genotype distributions were 3.2% with varepsilon2/3, 73.1% with varepsilon3/3 and 22.4% with varepsilon3/4 or varepsilon4/4. ApoE genotype did not have any effect on baseline lipid levels except on triglycerides such that the carriers of the varepsilon2 allele had concentrations significantly greater than those subjects with varepsilon3/3 genotype and carriers of the varepsilon4 allele after adjustment for age, gender and body mass index (BMI) (P < 0.001). Once adjusted for age, gender, BMI and baseline lipid levels, the apoE polymorphism did not significantly influence the plasma lipid and lipoprotein response to pravastatin.

CONCLUSION

ApoE genotype appears not to influence the hypolipidaemic effect of pravastatin in patients monitored in a general outpatient setting.

Apolipoprotein E genotypes and response of plasma lipids and progression-regression of coronary atherosclerosis to lipid-lowering drug therapy

OBJECTIVES

We sought to examine the association of apolipoprotein (apo) E genotypes with baseline plasma lipid levels and severity of coronary artery disease (CAD), as well as the response to treatment with fluvastatin in the Lipoprotein and Coronary Atherosclerosis Study (LCAS).

BACKGROUND

Apo E genotypes have been associated with plasma lipid levels and CAD. However, the influence of apo E genotypes on the response of plasma lipids and CAD progression or regression to statin treatment in patients with mildly to moderately elevated cholesterol remains unknown.

METHODS

Apo E genotypes were determined by polymerase chain reaction and restriction mapping. Plasma lipids were measured at baseline and 12 weeks after therapy with fluvastatin or placebo in 320 subjects. In 287 subjects, quantitative coronary angiography was performed at baseline and after 2.5 years of treatment.

RESULTS

Subjects with the 3/3 genotype had greater reductions in total cholesterol (20.4% vs. 15.4%, p = 0.01) and low density lipoprotein (LDL) cholesterol (28.8% vs. 22.7%, p = 0.03) than did the subjects with the 3/4 or 4/4 genotype. In contrast, subjects with the 2/3 genotype (n = 10) had a greater increase in high density lipoprotein cholesterol (19.1%) than did the subjects with the 3/3 genotype (4.3%, p = 0.002) and those with the 3/4 or 4/4 genotype (7.0%, p = 0.02). Subjects with the 3/4 or 4/4 genotype had an increased frequency of previous angioplasty, but other measures of baseline CAD severity and baseline lipids did not differ significantly among the genotypes, nor did CAD progression or clinical events.

CONCLUSIONS

Although subjects with the epsilon4 allele had less reduction in LDL cholesterol with fluvastatin, they had similar benefit in terms of CAD progression.

Apolipoprotein E polymorphisms and concentration in chronic diseases and drug responses

Apolipoprotein (apo) E is an important circulating and tissue protein involved in cholesterol homeostasis and many other functions. The common polymorphism in the coding region of the gene, four polymorphisms in the promoter region, other additional single nucleotide polymorphisms, as well as several apo E variants have been identified. The common coding polymorphism strongly influences the lipid metabolism and the circulating concentration of apo E itself. This polymorphism is at the origin of the implication of apo E in cardiovascular and neurodegenerative diseases, but also of the relation of apo E with longevity. Probably due to its many metabolic and functional consequences, apo E polymorphism has been shown to influence the responses of patients to several drugs (fibrates, statins, hormone replacement therapy, anti-Alzheimer drugs) or environmental interventions (black tea, alcohol, diet). Apo E genotyping may be clinically helpful in defining the risk of patients and their responses to therapeutics. Finally, circulating apo E concentration appears to be altered in diseases and can be modulated by some of the drugs cited above. This parameter can thus also give interesting clinical information and could be a therapeutic target, providing it is validated. At the present time, we cannot exclude that apo E concentration may be the most prominent apo E parameter to be considered in health and disease, while apo E polymorphisms would represent only secondary parameters influencing apo E concentration.

Pravastatin. A reappraisal of its pharmacological properties and clinical effectiveness in the management of coronary heart disease

Pravastatin is an HMG-CoA reductase inhibitor which lowers plasma cholesterol levels by inhibiting de novo cholesterol synthesis. Pravastatin produces consistent dose-dependent reductions in both total and low density lipoprotein (LDL)-cholesterol levels in patients with primary hypercholesterolaemia. Favourable changes in other parameters such as total triglyceride and high density lipoprotein (HDL)-cholesterol levels are generally modest. Combination therapy with other antihyperlipidaemic agents such as cholestyramine further enhances the efficacy of pravastatin in patients with severe dyslipidaemias. Available data suggest that pravastatin is effective in elderly patients and in patients with hypercholesterolaemia secondary to diabetes mellitus or renal disease. The benefit of cholesterol-lowering in terms of patient outcomes is currently an area of considerable interest. Recently completed regression studies (PLAC I, PLAC II, KAPS and REGRESS) show that pravastatin slows progression of atherosclerosis and lowers the incidence of coronary events in patients with mild to moderately severe hypercholesterolaemia and known coronary heart disease. Large scale primary (WOSCOPS) and secondary (CARE) prevention studies, moreover, demonstrate that pravastatin has beneficial effects on coronary morbidity and mortality. In WOSCOPS, all-cause mortality was reduced by 22%. Pravastatin is generally well tolerated by most patients (including the elderly), as evidenced by data from studies of up to 5 years in duration. As with other HMG-CoA reductase inhibitors, myopathy occurs rarely (< 0.1% of patients treated with pravastatin): approximately 1 to 2% of patients may present with raised serum levels of hepatic transaminases. Thus, with its favourable effects on cardiovascular morbidity/mortality and total mortality, pravastatin should be considered a first-line agent in patients with elevated cholesterol levels, multiple risk factors or coronary heart disease who are at high risk of cardiovascular morbidity.