Tolerability of statins is not linked to CYP450 polymorphisms, but reduced CYP2D6 metabolism improves cholesteraemic response to simvastatin and fluvastatin

When the same treatment has different response: The role of pharmacogenomics in statin therapy

Statins, also known as HMG-CoA reductase inhibitors, are one of the most potently prescribed and thoroughly researched medications, predominantly utilized for managing cardiovascular diseases by modulating serum cholesterol levels. Despite the well-documented efficacy of statins in reducing overall mortality via attenuating the risk of cardiovascular diseases, notable interindividual variability in therapeutic responses persists as such variability could compromise the lipid-lowering efficacy of the drug, potentially increasing susceptibility to adverse effects or attenuating therapeutic outcomes.This phenomenon has catalysed a growing interest in the scientific community to explore common genetic polymorphisms within genes that encode for pivotal enzymes within the pharmacokinetic pathways of statins. In our review, we focus to provide insight into potentially clinically relevant polymorphisms associated with statins' pharmacokinetic participants and assess their consequent implications on modulating the therapeutic outcomes of statins among distinct genetic carrier.

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.

Associations between SLCO1B1, APOE and CYP2C9 and lipid-lowering efficacy and pharmacokinetics of fluvastatin: a meta-analysis

Objective: This meta-analysis was designed to investigate the associations between SLCO1B1, APOE and CYP2C9 and the lipid-lowering effects and pharmacokinetics of fluvastatin. Methods: Studies were searched from inception to March 2023, including three SNPs related to fluvastatin, SLCO1B1, CYP2C9 and APOE. Weighted mean differences and corresponding 95% CIs were analyzed to evaluate the associations between SNPs and outcomes. Results: SLCO1B1 521T>C was associated with lower total cholesterol and low-density lipoprotein reduction. Patients carrying 521CC or total cholesterol had a significantly higher area under the curve than those carrying 521TT, but no significant difference existed. Conclusion: CYP2C9 and SLCO1B1 may be associated with the efficacy and pharmacokinetics of fluvastatin.

Role of Drug-Gene Interactions and Pharmacogenetics in Simvastatin-Associated Pulmonary Toxicity

Introduction

Simvastatin has previously been associated with drug-induced interstitial lung disease. In this retrospective observational study, cases with non-specific interstitial pneumonia (NSIP) or idiopathic pulmonary fibrosis (IPF) with simvastatin-associated pulmonary toxicity (n = 34) were evaluated.

Objective

To identify whether variations in genes encoding cytochrome P450 (CYP) enzymes or in the SLCO1B1 gene (Solute Carrier Organic anion transporting polypeptide 1B1 gene, encoding the organic anion transporting polypeptide 1B1 [OATP1B1] drug transporter enzyme), and/or characteristics of concomitantly used drugs, predispose patients to simvastatin-associated pulmonary toxicity.

Methods

Characteristics of concomitantly used drugs and/or variations in the CYP or SLCO1B1 genes and drug–gene interactions were assessed. The outcome after withdrawal of simvastatin and/or switch to another statin was assessed after 6 months.

Results

Multiple drug use involving either substrates and/or inhibitors of CYP3A4 and/or three or more drugs with the potential to cause acidosis explained the simvastatin-associated toxicity in 70.5% (n = 24) of cases. Cases did not differ significantly from controls regarding CYP3A4, CYP2C9, or OATP1B1 phenotypes, and genetic variation explained only 20.6% (n = 7) of cases. Withdrawal of simvastatin without switching to another statin or with a switch to a hydrophilic statin led to improvement or stabilization in all NSIP cases, whereas all cases who were switched to the lipophilic atorvastatin progressed.

Conclusion

Simvastatin-associated pulmonary toxicity is multifactorial. For patients with this drug-induced pulmonary toxicity who need to continue taking a statin, switching to a hydrophilic statin should be considered.

ClinicalTrials.gov identifier

NCT00267800, registered in 2005.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40264-021-01105-8.

Association between CYP3A5 Polymorphism and Statin-Induced Adverse Events: A Systemic Review and Meta-Analysis

Purpose: Cytochrome P450 (CYP) is involved in the metabolism of statins; CYP3A5 is the main enzyme responsible for lipophilic statin metabolism. However, the evidence of the association between CYP3A5*3 polymorphism and the risk of statin-induced adverse events remains unclear. Therefore, this study aimed to perform a systematic review and meta-analysis to investigate the relationship between the CYP3A5*3 polymorphism and the risk of statin-induced adverse events. Methods: The PubMed, Web of Science, and EMBASE databases were searched for qualified studies published until August 2020. Observational studies that included the association between statin-induced adverse events and the CYP3A5*3 polymorphism were reviewed. The odds ratios (ORs) and 95% confidence intervals (CIs) were evaluated to assess the strength of the relationship. The Mantel-Haenszel method was used to provide the pooled ORs. Heterogeneity was estimated with I² statistics and publication bias was determined by Begg's and Egger's test of the funnel plot. Data analysis was performed using Review Manager (version 5.4) and R Studio (version 3.6). Results: In total, data from 8 studies involving 1614 patients were included in this meta-analysis. The CYP3A5*3 polymorphism was found to be associated with the risk of statin-induced adverse events (*3/*3 vs. *1/*1 + *1/*3: OR = 1.40, 95% CI = 1.08-1.82). For myopathy, the pooled OR was 1.30 (95% CI: 0.96-1.75). The subgroup analysis of statin-induced myopathy revealed a trend, which did not achieve statistical significance. Conclusions: This meta-analysis demonstrated that the CYP3A5*3 polymorphism affected statin-induced adverse event risk. Therefore, CYP3A5 genotyping may be useful to predict statin toxicity.

Pharmacogenomics for Primary Care: An Overview

Most of the prescribing and dispensing of medicines happens in primary care. Pharmacogenomics (PGx) is the study and clinical application of the role of genetic variation on drug response. Mounting evidence suggests PGx can improve the safety and/or efficacy of several medications commonly prescribed in primary care. However, implementation of PGx has generally been limited to a relatively few academic hospital centres, with little adoption in primary care. Despite this, many primary healthcare providers are optimistic about the role of PGx in their future practice. The increasing prevalence of direct-to-consumer genetic testing and primary care PGx studies herald the plausible gradual introduction of PGx into primary care and highlight the changes needed for optimal translation. In this article, the potential utility of PGx in primary care will be explored and on-going barriers to implementation discussed. The evidence base of several drug-gene pairs relevant to primary care will be outlined with a focus on antidepressants, codeine and tramadol, statins, clopidogrel, warfarin, metoprolol and allopurinol. This review is intended to provide both a general introduction to PGx with a more in-depth overview of elements relevant to primary care.

Correlation between single-nucleotide polymorphisms and statin-induced myopathy: a mixed-effects model meta-analysis

PURPOSE

A meta-analysis was performed to evaluate the correlation between single-nucleotide polymorphisms (SNPs) and risk of statin-induced myopathy (SIM).

METHODS

We retrieved the studies published on SIM until April 2019 from the PubMed, Embase, and Cochrane Library databases. We collected data from 32 studies that analyzed 10 SNPs in five genes and included 21,692 individuals and nine statins.

RESULTS

The analysis of the heterozygous (p = 0.017), homozygous (p = 0.002), dominant (p = 0.005), and recessive models (p = 0.009) of SLCO1B1 rs4149056 showed that this SNP increases the risk of SIM. Conversely, heterozygous (p = 0.048) and dominant models (p = 0.030) of SLCO1B1 rs4363657 demonstrated that this SNP is associated with a reduced risk of SIM. Moreover, an increased risk of SIM was predicted for carriers of the rs4149056 C allele among simvastatin-treated patients, whereas carriers of the GATM rs9806699 A allele among rosuvastatin-treated patients had a lower risk of SIM.

CONCLUSION

The meta-analysis revealed that the rs4149056 and rs4363657 SNPs in SLCO1B1 and the rs9806699 SNP in GATM are correlated with the risk of SIM.

Pharmacogenetics of Statin-Induced Myotoxicity

Statins, a class of lipid-lowering medications, have been a keystone treatment in cardiovascular health. However, adverse effects associated with statin use impact patient adherence, leading to statin discontinuation. Statin-induced myotoxicity (SIM) is one of the most common adverse effects, prevalent across all ages, genders, and ethnicities. Although certain demographic cohorts carry a higher risk, the impaired quality of life attributed to SIM is significant. The pathogenesis of SIM remains to be fully elucidated, but it is clear that SIM is multifactorial. These factors include drug-drug interactions, renal or liver dysfunction, and genetics. Genetic-inferred risk for SIM was first reported by a landmark genome-wide association study, which reported a higher risk of SIM with a polymorphism in the SLCO1B1 gene. Since then, research associating genetic factors with SIM has expanded widely and has become one of the foci in the field of pharmacogenomics. This review provides an update on the genetic risk factors associated with SIM.

Statin-Related Myotoxicity: A Comprehensive Review of Pharmacokinetic, Pharmacogenomic and Muscle Components

Statins are a cornerstone in the pharmacological prevention of cardiovascular disease. Although generally well tolerated, a small subset of patients experience statin-related myotoxicity (SRM). SRM is heterogeneous in presentation; phenotypes include the relatively more common myalgias, infrequent myopathies, and rare rhabdomyolysis. Very rarely, statins induce an anti-HMGCR positive immune-mediated necrotizing myopathy. Diagnosing SRM in clinical practice can be challenging, particularly for mild SRM that is frequently due to alternative aetiologies and the nocebo effect. Nevertheless, SRM can directly harm patients and lead to statin discontinuation/non-adherence, which increases the risk of cardiovascular events. Several factors increase systemic statin exposure and predispose to SRM, including advanced age, concomitant medications, and the nonsynonymous variant, rs4149056, in SLCO1B1, which encodes the hepatic sinusoidal transporter, OATP1B1. Increased exposure of skeletal muscle to statins increases the risk of mitochondrial dysfunction, calcium signalling disruption, reduced prenylation, atrogin-1 mediated atrophy and pro-apoptotic signalling. Rare variants in several metabolic myopathy genes including CACNA1S, CPT2, LPIN1, PYGM and RYR1 increase myopathy/rhabdomyolysis risk following statin exposure. The immune system is implicated in both conventional statin intolerance/myotoxicity via LILRB5 rs12975366, and a strong association exists between HLA-DRB1*11:01 and anti-HMGCR positive myopathy. Epigenetic factors (miR-499-5p, miR-145) have also been implicated in statin myotoxicity. SRM remains a challenge to the safe and effective use of statins, although consensus strategies to manage SRM have been proposed. Further research is required, including stringent phenotyping of mild SRM through N-of-1 trials coupled to systems pharmacology omics- approaches to identify novel risk factors and provide mechanistic insight.

The association between the SLCO1B1, apolipoprotein E, and CYP2C9 genes and lipid response to fluvastatin: a meta-analysis

OBJECTIVE

The aim of this study was to determine the impact of the SLCO1B1, apolipoprotein E (ApoE), and CYP2C9 genotypes on the lipid-lowering efficacy of fluvastatin.

METHODS

We performed electronic searches on the PubMed, Embase, and Cochrane Library databases to identify studies published through October 2017. Studies that reported the effect estimates with 95% confidence intervals (CIs) of total cholesterol (TC), triglyceride, low-density lipoprotein (LDL), and high-density lipoprotein were included so that the different genotype categories could be compared. Weighted mean difference (WMD) was used to summarize the effect estimates.

RESULTS

Six studies, involving a total of 1171 individuals, were included in the final analysis. We noted that the patient carrier SLCO1B1 521TT was associated with greater change in TC (WMD: -2.98; 95% CI: -5.12 to -0.84; P=0.006) and LDL (WMD: -5.58; 95% CI: -10.64 to -0.52; P=0.031) compared with 521TC or CC. Furthermore, the patient carrier ApoE*2/*3 showed more change in high-density lipoprotein compared with ApoE*3/*3 (WMD: 18.76; 95% CI: 8.97-28.55; P<0.001) and ApoE*3/*4 or *4/*4 (WMD: 22.51; 95% CI: 0.98-44.04; P=0.040). Finally, the CYP2C9 genotypes showed no correlation with the effects of fluvastatin on TC, triglyceride, and LDL.

CONCLUSION

The findings of this study suggested that the SLCO1B1 and ApoE polymorphisms could influence the lipid-lowering effect of fluvastatin, whereas the CYP2C9 genotypes were not associated with the therapeutic effects of fluvastatin.

Population genetic difference of pharmacogenomic VIP gene variants in the Lisu population from Yunnan Province

Individual differences in drug clinical response are related to pharmacogenomics. The genetic variation of drug-metabolizing enzymes, drug receptors, and their downstream protein genes is the main factor causing individual differences in drug response. The genetic backgrounds among different ethnic groups are quite different. In this study, we aimed to detect the distribution difference of genotype frequency in very important pharmacogenetic (VIP) gene variants in the Lisu.Using the chi-squared test, we compared the genotype frequencies of the VIP variants in 105 Lisu people with those in 26 populations from the 1000 Genome project separately. Bonferroni's multiple adjustment was also conducted (P < .05/(26*49)). Moreover, Arlequin v3.5 and Structure v2.3.4 software were used to analyze the genetic distance and genetic structure.There were 9, 9, 11, 12, 11, 11, 9, 17, 13, 13, 16, 5, 3, 5, 3, 4, 17, 14, 16, 17, 16, 10, 13, 12, 10, and 9 single nucleotide polymorphisms that differed in frequency distribution, when Lisu people compared with the 26 populations separately. Only CYP2E1 rs2070676 was different in the Lisu population compared with the 26 groups from the 1000 Genome project. PTGS2 rs5275 and CYP2D6 rs1065852 were different in the Lisu population compared with most of the populations. Additionally, genetic backgrounds of Lisu and Han Chinese in Beijing were closest according to the lowest F-statistics value and resemblance in genetic structures.Our results complete the information of the Lisu population in pharmacogenomics database.

Can modulators of apolipoproteinB biogenesis serve as an alternate target for cholesterol-lowering drugs?

Understanding the molecular defects underlying cardiovascular disease is necessary for the development of therapeutics. The most common method to lower circulating lipids, which reduces the incidence of cardiovascular disease, is statins, but other drugs are now entering the clinic, some of which have been approved. Nevertheless, patients cannot tolerate some of these therapeutics, the drugs are costly, and/or the treatments are approved for only rare forms of disease. Efforts to find alternative treatments have focused on other factors, such as apolipoproteinB (apoB), which transports cholesterol in the blood stream. The levels of apoB are regulated by endoplasmic reticulum (ER) associated degradation as well as by a post ER degradation pathway in model systems, and we suggest that these events provide novel therapeutic targets. We discuss first how cardiovascular disease arises and how cholesterol is regulated, and then summarize the mechanisms of action of existing treatments for cardiovascular disease. We then review the apoB biosynthetic pathway, focusing on steps that might be amenable to therapeutic interventions.

Pharmacogenetic Foundations of Therapeutic Efficacy and Adverse Events of Statins

Background: In the era of precision medicine, more attention is paid to the search for predictive markers of treatment efficacy and tolerability. Statins are one of the classes of drugs that could benefit from this approach because of their wide use and their incidence of adverse events. Methods: Literature from PubMed databases and bibliography from retrieved publications have been analyzed according to terms such as statins, pharmacogenetics, epigenetics, toxicity and drug–drug interaction, among others. The search was performed until 1 October 2016 for articles published in English language. Results: Several technical and methodological approaches have been adopted, including candidate gene and next generation sequencing (NGS) analyses, the latter being more robust and reliable. Among genes identified as possible predictive factors associated with statins toxicity, cytochrome P450 isoforms, transmembrane transporters and mitochondrial enzymes are the best characterized. Finally, the solute carrier organic anion transporter family member 1B1 (SLCO1B1) transporter seems to be the best target for future studies. Moreover, drug–drug interactions need to be considered for the best approach to personalized treatment. Conclusions: Pharmacogenetics of statins includes several possible genes and their polymorphisms, but muscular toxicities seem better related to SLCO1B1 variant alleles. Their analysis in the general population of patients taking statins could improve treatment adherence and efficacy; however, the cost–efficacy ratio should be carefully evaluated.

Impact of CYP2D6, CYP3A5, CYP2C19, CYP2A6, SLCO1B1, ABCB1, and ABCG2 gene polymorphisms on the pharmacokinetics of simvastatin and simvastatin acid

OBJECTIVE

The effects of various polymorphisms in cytochrome P450 (CYP) enzyme and transporter genes on the pharmacokinetics (PK) of simvastatin were evaluated in healthy Korean men.

METHODS

Plasma concentration data for simvastatin and simvastatin acid were pooled from four phase I studies comprising 133 participants. The polymorphisms CYP2D6*4, CYP2D6*5, CYP2D6*14, CYP2D6*41, CYP3A5*3, CYP2C19*2, CYP2C19*3, CYP2A6*7, and CYP2A6*9; SLCO1B1 rs4149056, rs2306283, and rs4149015; ABCB1 rs1128503, rs2032582, and rs1045642; and ABCG2 rs2231142 were evaluated in each participant. Noncompartmental PK results were compared by genotype.

RESULTS

CYP2D6*5 and CYP2D6*14 were found to be associated with a higher area under the curve (AUC) for simvastatin, whereas the AUC of simvastatin acid was significantly increased in patients with the SLCO1B1 rs4149056, ABCG2 rs2231142, and CYP2D6*41 allele variants. Patients with the CYP2D6*41 variant showed a higher peak serum concentration (Cmax) of both simvastatin and simvastatin acid. The SLCO1B1 rs4149056 and rs4149015 polymorphisms were associated with an increased AUC ratio (i.e. ratio of simvastatin acid to simvastatin), whereas the SLCO1B1 rs4149056 and CYP2D6*5 variants were related to a higher Cmax ratio.

CONCLUSION

The CYP2D6*5, CYP2D6*14, CYP2D6*41, CYP3A5*3, SLCO1B1 rs4149056 and rs4149015, and ABCG2 rs2231142 genetic polymorphisms are associated with the PK of both simvastatin and simvastatin acid. This could potentially be used as a basis for individualized simvastatin therapy by predicting the clinical outcomes of this treatment.

Statin-associated myopathy: from genetic predisposition to clinical management

Statin-associated myopathy (SAM) represents a broad spectrum of disorders from insignificant myalgia to fatal rhabdomyolysis. Its frequency ranges from 1-5 % in clinical trials to 15-20 % in everyday clinical practice. To a large extent, these variations can be explained by the definition used. Thus, we propose a scoring system to classify statin-induced myopathy according to clinical and biochemical criteria as 1) possible, 2) probable or 3) definite. The etiology of this disorder remains poorly understood. Most probably, an underlying genetic cause is necessary for overt SAM to develop. Variants in a few gene groups that encode proteins involved in: i) statin metabolism and distribution (e.g. membrane transporters and enzymes; OATP1B1, ABCA1, MRP, CYP3A4), ii) coenzyme Q10 production (e.g. COQ10A and B), iii) energy metabolism of muscle tissue (e.g. PYGM, GAA, CPT2) and several others have been proposed as candidates which can predispose to SAM. Pharmacological properties of individual statin molecules (e.g. lipophilicity, excretion pathways) and patients´ characteristics influence the likelihood of SAM development. This review summarizes current data as well as our own results.

Genetic and immunologic susceptibility to statin-related myopathy

Statin-related myopathy (SRM) undermines drug adherence that is critical for achieving the benefits of lipid-lowering therapy. While the exact mechanism of SRM remains largely unknown, recent evidence supports specific genetic and immunologic influence on the development of intolerance. Genes of interest include those involved in the pharmacokinetics of statin response (i.e. drug metabolism, uptake transporters, and efflux transporters), pharmacodynamics (i.e. drug toxicity and immune-mediated myopathy), and gene expression. We examine the influence of genetic and immunologic variation on the pharmacokinetics, pharmacodynamics, and gene expression of SRM.

Creatine kinase elevation caused by a combination of fluvastatin and telmisartan in a patient heterozygous for the CYP2C9*3 and ABCC2 -24C > T variants: a case report

Background

Genetic factors as predictor of the individual outcome of drug therapy is one aim of personalized medicine approaches.

Case presentation

We report a drug metabolism based analysis of genetic polymorphisms in a Caucasian patient receiving fluvastatin and telmisartan experiencing myotoxicity (myalgia and moderate creatine kinase elevation).

Conclusions

The obtained findings suggest that heterocygocity of cytochrome P450 CYP2C9*3 variant in combination with multidrug resistance-associated protein MRP2 -24C > T functions as risk factor predisposing to experience drug-drug interaction combing those drugs.

The potential applications of Apolipoprotein E in personalized medicine

Personalized medicine uses various individual characteristics to guide medical decisions. Apolipoprotein (ApoE), the most studied polymorphism in humans, has been associated with several diseases. The purpose of this review is to elucidate the potential role of ApoE polymorphisms in personalized medicine, with a specific focus on neurodegenerative diseases, by giving an overview of its influence on disease risk assessment, diagnosis, prognosis, and therapy. This review is not a systematic inventory of the literature, but rather a summary and discussion of novel, influential and promising works in the field of ApoE research that could be valuable for personalized medicine. Empirical evidence suggests that ApoE genotype informs pre-symptomatic risk for a wide variety of diseases, is valuable for the diagnosis of type III dysbetalipoproteinemia, increases risk of dementia in neurodegenerative diseases, and is associated with a poor prognosis following acute brain damage. ApoE status appears to influence the efficacy of certain drugs, outcome of clinical trials, and might also give insight into disease prevention. Assessing ApoE genotype might therefore help to guide medical decisions in clinical practice.

Genetic factors affecting statin concentrations and subsequent myopathy: a HuGENet systematic review

Statins, 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase inhibitors, have proven efficacy in both lowering low-density-lipoprotein levels and preventing major coronary events, making them one of the most commonly prescribed drugs in the United States. Statins exhibit a class-wide side effect of muscle toxicity and weakness, which has led regulators to impose both dosage limitations and a recall. This review focuses on the best-characterized genetic factors associated with increased statin muscle concentrations, including the genes encoding cytochrome P450 enzymes (CYP2D6, CYP3A4, and CYP3A5), a mitochondrial enzyme (GATM), an influx transporter (SLCO1B1), and efflux transporters (ABCB1 and ABCG2). A systematic literature review was conducted to identify relevant research evaluating the significance of genetic variants predictive of altered statin concentrations and subsequent statin-related myopathy. Studies eligible for inclusion must have incorporated genotype information and must have associated it with some measure of myopathy, either creatine kinase levels or self-reported muscle aches and pains. After an initial review, focus was placed on seven genes that were adequately characterized to provide a substantive review: CYP2D6, CYP3A4, CYP3A5, GATM, SLCO1B1, ABCB1, and ABCG2. All statins were included in this review. Among the genetic factors evaluated, statin-related myopathy appears to be most strongly associated with variants in SLCO1B1.

Statin therapy correlated CYP2D6 gene polymorphism and hyperlipidemia

PURPOSE

To investigate the distribution of statin therapy correlated gene polymorphism allele CYP2D6*10 (C188T) in Ningxia Hui nationality and to discuss the relationship between the gene polymorphism allele CYP2D6*10 (C188T) and the lipid-lowering efficacy of simvastatin and hyperlipidemia.

MATERIALS AND METHODS

One hundred and fifty healthy people (80 males and 70 females) and 200 hyperlipidemia patients (105 males and 95 females) were recruited at Ningxia People's Hospital. Genotypes were determined by using allele-specific amplification (ASA-PCR) in 150 healthy controls and 200 patients with hyperlipidemia. Relationships between genotypes and lipid levels and the lipid-lowering efficacy of simvastatin were analyzed.

RESULTS

The distribution frequency of the CYP2D6*10 allele was 47.6% in the Ningxia Hui nationality. There was no significant correlation between the CYP2D6*10 allele and hyperlipidemia. At 8 weeks after treatment with simvastatin, total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) levels were more obviously decreased with the CC genotype than the CT and TT genotypes, with significant differences.

CONCLUSION

Distribution of the gene polymorphism of CYP2D6*10 is ethnically and geographical different. The allele T of CYP2D6*10 is not related to hyperlipidemia. CC expression seemed to increase the lipid-lowering effects of simvastatin. The hyperlipidemia patients with CC genotype should take lower doses of simvastatin than those with CT/TT genotype in the Ningxia Hui population.

Pharmacogenetics of Statin-Induced Myopathy: A Focused Review of the Clinical Translation of Pharmacokinetic Genetic Variants

Statins are the most commonly prescribed drugs in the United States and are extremely effective in reducing major cardiovascular events in the millions of Americans with hyperlipidemia. However, many patients (up to 25%) cannot tolerate or discontinue statin therapy due to statin-induced myopathy (SIM). Patients will continue to experience SIM at unacceptably high rates or experience unnecessary cardiovascular events (as a result of discontinuing or decreasing their statin therapy) until strategies for predicting or mitigating SIM are identified. A promising strategy for predicting or mitigating SIM is pharmacogenetic testing, particularly of pharmacokinetic genetic variants as SIM is related to statin exposure. Data is emerging on the association between pharmacokinetic genetic variants and SIM. A current, critical evaluation of the literature on pharmacokinetic genetic variants and SIM for potential translation to clinical practice is lacking. This review focuses specifically on pharmacokinetic genetic variants and their association with SIM clinical outcomes. We also discuss future directions, specific to the research on pharmacokinetic genetic variants, which could speed the translation into clinical practice. For simvastatin, we did not find sufficient evidence to support the clinical translation of pharmacokinetic genetic variants other than SLCO1B1. However, SLCO1B1 may also be clinically relevant for pravastatin- and pitavastatin-induced myopathy, but additional studies assessing SIM clinical outcome are needed. CYP2D6*4 may be clinically relevant for atorvastatin-induced myopathy, but mechanistic studies are needed. Future research efforts need to incorporate statin-specific analyses, multi-variant analyses, and a standard definition of SIM. As the use of statins is extremely common and SIM continues to occur in a significant number of patients, future research investments in pharmacokinetic genetic variants have the potential to make a profound impact on public health.

The pharmacogenomics of statins

The statin class of cholesterol-lowering drugs have been used for decades to successfully lower plasma cholesterol concentrations and cardiovascular risk. Adverse effects of statins are generally considered mild, but increase with age of patients and polypharmacy. One aspect of statin therapy that is still difficult for prescribers to predict is the individual's response to statin therapy. Recent advances in the field of pharmacogenomics have indicated variants of candidate genes that affect statin efficacy and safety. In this review, a number of candidates that affect statin pharmacokinetics and pharmacodynamics are discussed. Some of these candidates, in particular those involved in import and efflux of statins, have now been linked to increased risk of side effects. Furthermore, pharmacogenomic studies continue to reveal new players that are involved in the fine-tuning of the complex regulation of cholesterol homeostasis and response to statins.

Statin myotoxicity: a review of genetic susceptibility factors

The 3-hydroxy-3-methylglutaryl coenzyme A (HMGCoA) reductase inhibitors (statins) are among the most common medications prescribed worldwide, but their efficacy and toxicity vary between individuals. One of the major factors contributing to intolerance and non-compliance are the muscle side-effects, which range from mild myalgia through to severe life-threatening rhabdomyolysis. One way to address this is pharmacogenomic screening, which aims to individualize therapy to maximize efficacy whilst avoiding toxicity. Genes encoding proteins involved in the metabolism of statins as well as genes known to cause inherited muscle disorders have been investigated. To-date only polymorphisms in the SLCO1B1 gene, which encodes the protein responsible for hepatic uptake of statins, and the COQ2 gene, important in the synthesis of coenzyme Q10, have been validated as being strongly associated with statin-induced myopathy. The aim of this review is to summarize studies investigating genetic factors predisposing to statin myopathy and myalgia, as the first step towards pharmacogenomic screening to identify at risk individuals.

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.

Clinical response to statins: mechanism(s) of variable activity and adverse effects

Statins represent a major advance in the treatment of hypercholesterolemia, a significant risk factor for atherosclerosis. There is, however, notable interindividual variation in the cholesterolemic response to statins, and the origin of this variability is poorly understood; pharmacogenetics has attempted to determine the role of genetic factors. Myopathy, further, has been reported in a considerable percentage of patients, but the mechanisms underlying muscle injury have yet to be fully characterized. Most statins are the substrates of several cytochrome P450s (CYP). CYP polymorphisms may be responsible for variations in hypolipidemic activity; inhibitors of CYPs, e.g. of CYP3A4, can significantly raise plasma concentrations of several statins, but consequences in terms of clinical efficacy are not uniform. Pravastatin and rosuvastatin are not susceptible to CYP inhibition but are substrates of the organic anion-transporting polypeptide (OATP) 1B1, encoded by the SLCO1B1 gene. Essentially all statins are, in fact, substrates of membrane transporters: SLCO1B1 polymorphisms can decrease the liver uptake, as well as the therapeutic potential of these agents, and may be linked to their muscular side-effects. A better understanding of the mechanisms of statin handling will help to minimize adverse effects and interactions, as well as to improve their lipid-lowering efficiency.

Statin induced myotoxicity

Statins are an effective treatment for the prevention of cardiovascular diseases and used extensively worldwide. However, myotoxicity induced by statins is a common adverse event and a major barrier to maximising cardiovascular risk reduction. The clinical spectrum of statin induced myotoxicity includes asymptomatic rise in creatine kinase concentration, myalgia, myositis and rhabdomyolysis. In certain cases, the cessation of statin therapy does not result in the resolution of muscular symptoms or the normalization of creatine kinase, raising the possibility of necrotizing autoimmune myopathy. There is increasing understanding and recognition of the pathophysiology and risk factors of statin induced myotoxicity. Careful history and physical examination in conjunction with selected investigations such as creatine kinase measurement, electromyography and muscle biopsy in appropriate clinical scenario help diagnose the condition. The management of statin induced myotoxicity involves statin cessation, the use of alternative lipid lowering agents or treatment regimes, and in the case of necrotizing autoimmune myopathy, immunosuppression.

Statin dose in Asians: is pharmacogenetics relevant?

Historically the efficacy and safety of statins has mostly been studied in western populations. Few such studies have been carried out in Asians until recent years. These studies revealed interesting similarities and differences for statin use between Asians and Caucasians. One clinically important question subsequently raised is whether Asians need lower statin doses compared with Caucasians. Many practicing physicians believe that statin doses are lower in Asians because of the generally lower bodyweight and BMI. Whether this belief is based on sound scientific evidence needs to be reviewed. Furthermore, since the decision of optimal dose is based on both efficacy and safety, both of which may be impacted by genetic factors, one may ask whether pharmacogenetics plays a role in the dose difference, if such a difference exists. There is a clinical need to critically and comprehensively article the literature to answer these questions, and summarize future directions of research in the field. This article serves the above purpose.

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.

The genetics of statin-induced myopathy

OBJECTIVE

Our goal was to use genetic variants to identify factors contributing to the muscular side effects of statins.

BACKGROUND

Statins (3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors) are usually well tolerated medications, but muscle symptoms, ranging from mild myalgia to clinically important rhabdomyolysis are an important side effect of these drugs and a leading cause of noncompliance. Recent results suggest that genetic factors increase the risk of statin-related muscle complaints. We performed a systematic review of the medical literature to determine genetic factors associated with statin myopathy.

METHODS

We identified English language articles relating statin myopathy and genetic diseases and gene variants via a PubMed search. Articles pertinent to the topic were reviewed in detail.

RESULTS/CONCLUSIONS

Our review suggests that some patients are susceptible to statin myopathy because of pre-existing subclinical inherited muscular disorders, or genetic variation in statin uptake proteins encoded by SLCO1B1 or the cytochrome P enzyme system. Variations in genes affecting pain perception and polymorphism in vascular receptors may also contribute to statin myopathy. None of the variants identified in this review suggested novel metabolic mechanisms leading to statin myopathy.

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.

Cardiovascular pharmacogenomics and individualized drug therapy

The goal of individualized drug therapy requires physicians to be able to accurately predict an individual's response to a drug. Both genetic and environmental factors are known to influence drug response. 'Pharmacogenetics' is the study of the role of inheritance in variation in drug response phenotypes. Pharmacogenetics is now moving genome-wide to become 'pharmacogenomics', resulting in the recognition of novel biomarkers for individual variation in drug response. This article reviews the development, promise and challenges facing pharmacogenomics, using examples of drugs used to treat or prevent cardiovascular disease.

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.

Genetic determinants of statin-associated myopathy

Lipid-lowering drugs, especially 3-hydroxy-3-methylglutaryl coenzyme A inhibitors (statins), are widely used in the treatment of patients with increased risk of cardiovascular disease, with well-documented benefits. However, in rare cases, lipid-lowering drugs may cause myopathy or rhabdomyolysis, the risk of which is increased by certain drug–drug interactions. Polymorphisms of metabolizing pathways, including CYP, and efflux transporters, such as MDR1 and SLCO1B1, may cause intersubject variability in plasma statin levels and therefore may be responsible for susceptibility to myopathy. The aim of this review is to summarize selected genetic polymorphisms that predispose to statin-related myopathy (including combined studies of myopathy and myalgia). Genome-wide studies suggest that there is a strong candidate variant within the SLCO1B1 gene (rs4149056) for statin-associated myopathy in a UK (European) population. An enhanced understanding of statin-related myopathy may lead to safer drug development and use.

Molecular basis for statin-induced muscle toxicity: implications and possibilities

Statins are widely used to treat hypercholesterolemia, a known risk factor for atherosclerosis. These drugs can lead to a number of side effects in muscle, including rhabdomyolysis; however, the mechanism of muscle injury is poorly defined. We review the clinical characteristics of this diverse syndrome, as well as the biochemical mechanisms that might provide an explanation for the toxicity of these agents. New findings implicating atrogin-1, a gene required for muscle atrophy, in the pathophysiology of statin-induced muscle injury are discussed, as well as implications of these novel discoveries.

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.

Statin adverse effects : a review of the literature and evidence for a mitochondrial mechanism

HMG-CoA reductase inhibitors (statins) are a widely used class of drug, and like all medications, have potential for adverse effects (AEs). Here we review the statin AE literature, first focusing on muscle AEs as the most reported problem both in the literature and by patients. Evidence regarding the statin muscle AE mechanism, dose effect, drug interactions, and genetic predisposition is examined. We hypothesize, and provide evidence, that the demonstrated mitochondrial mechanisms for muscle AEs have implications to other nonmuscle AEs in patients treated with statins. In meta-analyses of randomized controlled trials (RCTs), muscle AEs are more frequent with statins than with placebo. A number of manifestations of muscle AEs have been reported, with rhabdomyolysis the most feared. AEs are dose dependent, and risk is amplified by drug interactions that functionally increase statin potency, often through inhibition of the cytochrome P450 3A4 system. An array of additional risk factors for statin AEs are those that amplify (or reflect) mitochondrial or metabolic vulnerability, such as metabolic syndrome factors, thyroid disease, and genetic mutations linked to mitochondrial dysfunction. Converging evidence supports a mitochondrial foundation for muscle AEs associated with statins, and both theoretical and empirical considerations suggest that mitochondrial dysfunction may also underlie many nonmuscle statin AEs. Evidence from RCTs and studies of other designs indicates existence of additional statin-associated AEs, such as cognitive loss, neuropathy, pancreatic and hepatic dysfunction, and sexual dysfunction. Physician awareness of statin AEs is reportedly low even for the AEs most widely reported by patients. Awareness and vigilance for AEs should be maintained to enable informed treatment decisions, treatment modification if appropriate, improved quality of patient care, and reduced patient morbidity.

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.