The association of common SNPs and haplotypes in the CETP and MDR1 genes with lipids response to fluvastatin in familial hypercholesterolemia

Major Genetic Drivers of Statin Treatment Response in African Populations and Pharmacogenetics of Dyslipidemia Through a One Health Lens

A One Health lens is increasingly significant to address the intertwined challenges in planetary health concerned with the health of humans, nonhuman animals, plants, and ecosystems. A One Health approach can benefit the public health systems in Africa that are overburdened by noncommunicable, infectious, and environmental diseases. Notably, the COVID-19 pandemic revealed the previously overlooked two-fold importance of pharmacogenetics (PGx), for individually tailored treatment of noncommunicable diseases and environmental pathogens. For example, dyslipidemia, a common cardiometabolic risk factor, has been identified as an independent COVID-19 severity risk factor. Observational data suggest that patients with COVID-19 infection receiving lipid-lowering therapy may have better outcomes. However, among African patients, the response to these drugs varies from patient to patient, pointing to the possible contribution of genetic variation in important pharmacogenes. The PGx of lipid-lowering therapies may underlie differences in treatment responses observed among dyslipidemia patients as well as patients comorbid with COVID-19 and dyslipidemia. Genetic variations in APOE, ABCB1, CETP, CYP2C9, CYP3A4, CYP3A5, HMGCR, LDLR, NPC1L1, and SLCO1B1 genes affect the pharmacogenomics of statins, and they have individually been linked to differential responses to dyslipidemia and COVID-19 treatment. African populations are underrepresented in PGx research. This leads to poor accounting of additional diverse genetic variants that could be important in understanding interindividual and between-population variations in therapeutic responses to dyslipidemia and COVID-19. This expert review examines and synthesizes the salient and priority PGx variations, as seen through a One Health lens in Africa, to improve and inform personalized medicine in both dyslipidemia and COVID-19.

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.

Association of CETP Gene Polymorphisms and Haplotypes with Cardiovascular Risk

Cholesteryl ester transfer protein (CETP) is known to influence HDL-C levels, potentially altering the profile of HDL subfractions and consequently cardiovascular risk (CVR). This study aimed to investigate the effect of five single-nucleotide polymorphisms (SNPs; rs1532624, rs5882, rs708272, rs7499892, and rs9989419) and their haplotypes (H) in the CETP gene on 10-year CVR estimated by the Systematic Coronary Risk Evaluation (SCORE), the Framingham Risk Score for Coronary Heart Disease (FRS_CHD) and Cardiovascular Disease (FRS_CVD) algorithms. Adjusted linear and logistic regression analyses were used to investigate the association of SNPs and 10 haplotypes (H1-H10) on 368 samples from the Hungarian general and Roma populations. The T allele of rs7499892 showed a significant association with increased CVR estimated by FRS. H5, H7, and H8 showed a significant association with increased CVR based on at least one of the algorithms. The impact of H5 was due to its effect on TG and HDL-C levels, while H7 showed a significant association with FRS_CHD and H8 with FRS_CVD mediated by a mechanism affecting neither TG nor HDL-C levels. Our results suggest that polymorphisms in the CETP gene may have a significant effect on CVR and that this is not mediated exclusively by their effect on TG and HDL-C levels but also by presently unknown mechanisms.

Pharmacogenomics Variability of Lipid-Lowering Therapies in Familial Hypercholesterolemia

The exponential expansion of genomic data coupled with the lack of appropriate clinical categorization of the variants is posing a major challenge to conventional medications for many common and rare diseases. To narrow this gap and achieve the goals of personalized medicine, a collaborative effort should be made to characterize the genomic variants functionally and clinically with a massive global genomic sequencing of "healthy" subjects from several ethnicities. Familial-based clustered diseases with homogenous genetic backgrounds are amongst the most beneficial tools to help address this challenge. This review will discuss the diagnosis, management, and clinical monitoring of familial hypercholesterolemia patients from a wide angle to cover both the genetic mutations underlying the phenotype, and the pharmacogenomic traits unveiled by the conventional and novel therapeutic approaches. Achieving a drug-related interactive genomic map will potentially benefit populations at risk across the globe who suffer from dyslipidemia.

Pharmacogenomics of statins and familial hypercholesterolemia

PURPOSE OF REVIEW

To collect evidence on statin pharmacogenomics, and review what is known in this field for familial hypercholesterolemia (FH) patients.

RECENT FINDINGS

There are well-known associations between specific single nucleotide polymorphisms involved in statin transport and metabolism and either adverse effects or altered lipid-lowering efficacy. However, the applicability of this knowledge is uncertain, especially in high-risk populations. There are alternative approaches to study plasma concentrations of statins and new insights on why some association studies fail to be replicated.

SUMMARY

Statin therapy recommendations are not always followed in primary and secondary prevention and, even when followed, patients often fail to reach therapeutic target values. Considering the stringent 2019 European Atherosclerosis Society and European Society of Cardiology recommended target lipid levels, as well as the persistently high cost for alternative lipid-lowering therapies such as PCSK9 inhibitors, the variability in low-density lipoprotein cholesterol reductions on statin therapy is still an important factor that needs to be addressed to ensure better cardiovascular disease risk management, especially for FH patients, who have not been well studied historically in this context.

The Effect of Haplotypes in the CETP and LIPC Genes on the Triglycerides to HDL-C Ratio and Its Components in the Roma and Hungarian General Populations

BACKGROUND

The triglycerides (TG) to high-density lipoprotein (HDL)-cholesterol (HDL-C) ratio (TG/HDL-C) is a well-known predictor for cardiovascular diseases (CVDs) with great heritability background. The cholesteryl ester transfer protein (CETP) and hepatic lipase (LIPC) gene affect TG/HDL-C ratio. This study aims to explore the association between haplotypes (H) in CETP (based on 5 single nucleotide polymorphisms (SNPs)) and LIPC (based on 6 SNPs) genes and the TG/HDL-C ratio and its components, among Roma and Hungarian general populations.

METHODS

The prevalence of haplotypes and their effect on HDL-C, TG and TG/HDL-C ratio were calculated in both populations and compared.

RESULTS

Ten haplotypes in CETP and 6 in LIPC gene were identified. Three haplotypes in CETP and 3 in LIPC have significant effect on HDL-C level, whereas two in CETP and 3 in LIPC on TG level. The H6 in CETP (β = 0.52, p = 0.015; odds ratio (OR) = 1.87, p = 0.009) and H5 in LIPC (β = 0.56, p < 0.001; OR = 1.51, p = 0.002) have a significant increasing effect on TG/HDL-C ratio and have shown higher prevalence among the Roma, as compared to Hungarian general population. The H2 in the CETP gene has a decreasing effect on the TG/HDL-C ratio (OR = 0.58, p = 0.019) and is significantly less frequent among the Roma.

CONCLUSIONS

Accumulation of harmful haplotypes in CETP and LIPC genes might have a role in the elevated TG/HDL-C ratio in the Roma population, which contributes to a higher risk in the development of cardiovascular diseases.

Interactions Between ABCB1 Genotype and Preoperative Statin Use Impact Clinical Outcomes Among Breast Cancer Patients

Multiple clinical trials investigate statins' effects in breast cancer. The ABCB1 genotype appears to influence statin response and toxicity in the cardiovascular setting. This exploratory study aimed to investigate the interplay between preoperative statin use, ABCB1 genotype, and tumor-specific expression of the statin target 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) in breast cancer. Preoperative statin use, ABCB1 C3435T genotype, and HMGCR expression in relation to outcome were analyzed in 985 primary breast cancer patients from a population-based prospective cohort in Sweden from 2002 to 2012. Preoperative statin use (n = 80) was not associated with ABCB1 C3435T genotype (n = 576), HMGCR expression (n = 848), or clinical outcomes. ABCB1 C3435T TT-carriers had lower risk of breast cancer events than any C-carriers (adjusted hazard ratio (HR_adj) 0.74; 95%CI 0.49, 1.12), but only in non-statin users (P_interaction = 0.042). Statin users with TT genotype had higher risk of distant metastasis (HR_adj 4.37; 95%CI 1.20, 15.91; P_interaction = 0.009) and shorter overall survival than other patients (HR_adj 3.77; 95%CI 1.37, 10.39; P_interaction = 0.019). In conclusion, there were nominally significant interactions between ABCB1 genotype and preoperative statin use on clinical outcomes, while preoperative statin use was not associated with outcomes. Since this is an exploratory study of the impact of the ABCB1 genotype in relation to statin use and clinical outcomes in the breast cancer setting, the results should be interpreted with caution and warrant replication in an independent cohort, preferably in a randomized setting. Since statin use is common in breast cancer patients, it would be of interest to further elucidate the clinical impact of the ABCB1 genotype in breast cancer.

ANGPTL4 variants and their haplotypes are associated with serum lipid levels, the risk of coronary artery disease and ischemic stroke and atorvastatin cholesterol-lowering responses

Background

This study aimed to assess the association between the angiopoietin-like protein 4 gene (ANGPTL4) single nucleotide polymorphisms (SNPs) and serum lipid levels, the risk of coronary artery disease (CAD) and ischemic stroke (IS), and response to atorvastatin therapy in a Southern Chinese Han population.

Methods

Genotypes of the ANGPTL4 rs4076317, rs7255436, rs1044250 and rs2967605 SNPs in 1,654 unrelated subjects (CAD, 568; IS, 537; and controls, 549) were determined by the Snapshot technology. Another group of 724 hyperlipidemic patients was selected and treated with atorvastatin calcium tablet 20 mg/day for 8 weeks.

Results

The rs2967605 CT/TT genotypes were associated with a decreased risk of CAD (adjusted OR = 0.68, 95% CI = 0.47-0.99, P = 0.043 for CT/TT vs. CC) and IS (adjusted OR = 0.55, 95% CI = 0.38-0.80, P = 0.020 for CT/TT vs. CC). There was no significant association between the four SNPs and angiographic severity of CAD. The subjects with the rs4076317 CG/CC genotypes in controls had higher total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) levels than the subjects with the GG genotype (P < 0.001; a P < 0.0018 was regarded statistically significant by the Bonferroni correction). The subjects with rs4076317CG/GG genotypes had lower TC and LDL-C levels than the subjects with CC genotype after atorvastatin treatment (P < 0.001).

Conclusions

The observed associations suggest that the ANGPTL4 variants have a potential role on serum lipid levels and atherosclerosis-related diseases in the Chinese Han population, especially the ANGPTL4 rs4076317 and rs2967605 SNPs.

Meta-analysis of genome-wide association studies of HDL cholesterol response to statins

BACKGROUND

In addition to lowering low density lipoprotein cholesterol (LDL-C), statin therapy also raises high density lipoprotein cholesterol (HDL-C) levels. Inter-individual variation in HDL-C response to statins may be partially explained by genetic variation.

METHODS AND RESULTS

We performed a meta-analysis of genome-wide association studies (GWAS) to identify variants with an effect on statin-induced high density lipoprotein cholesterol (HDL-C) changes. The 123 most promising signals with p<1×10-4 from the 16 769 statin-treated participants in the first analysis stage were followed up in an independent group of 10 951 statin-treated individuals, providing a total sample size of 27 720 individuals. The only associations of genome-wide significance (p<5×10-8) were between minor alleles at the CETP locus and greater HDL-C response to statin treatment.

CONCLUSIONS

Based on results from this study that included a relatively large sample size, we suggest that CETP may be the only detectable locus with common genetic variants that influence HDL-C response to statins substantially in individuals of European descent. Although CETP is known to be associated with HDL-C, we provide evidence that this pharmacogenetic effect is independent of its association with baseline HDL-C levels.

Statin-induced expression change of INSIG1 in lymphoblastoid cell lines correlates with plasma triglyceride statin response in a sex-specific manner

Statins are widely prescribed to lower plasma low-density lipoprotein (LDL) cholesterol levels. They also modestly reduce plasma triglyceride (TG), an independent cardiovascular disease risk factor, in most people. The mechanism and inter-individual variability of TG statin response is poorly understood. We measured statin-induced gene expression changes in lymphoblastoid cell lines derived from 150 participants of a simvastatin clinical trial and identified 23 genes (false discovery rate, FDR=15%) with expression changes correlated with plasma TG response. The correlation of insulin-induced gene 1 (INSIG1) expression changes with TG response (rho=0.32, q=0.11) was driven by men (interaction P=0.0055). rs73161338 was associated with INSIG1 expression changes (P=5.4 × 10⁻⁵) and TG response in two statin clinical trials (P=0.0048), predominantly in men. A combined model including INSIG1 expression level and splicing changes accounted for 29.5% of plasma TG statin response variance in men (P=5.6 × 10⁻⁶). Our results suggest that INSIG1 variation may contribute to statin-induced changes in plasma TG in a sex-specific manner.

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.

ABCB1 C3435T polymorphism and the lipid-lowering response in hypercholesterolemic patients on statins: a meta-analysis

BACKGROUND

A number of researches have evaluated the association between the ABCB1 polymorphism and the lipid-lowering response of statins, but the results have been inconclusive. To examine the lipid-lowering efficacy and safety associated with the ABCB1 C3435T polymorphism in hypercholesterolemic patients receiving statin, all available studies were included in this meta-analysis.

METHODS

A systematic search for eligible studies in the Cochrane library database, Scopus and PubMed was performed. Articles meeting the inclusion criteria were comprehensively reviewed, and the available data were accumulated by the meta-analysis.

RESULTS

The results indicated that the comparisons of CC+CT vs. TT were associated with a significant elevation of the serum HDL-C levels after statin treatment (CC+CT vs. TT: MD, 2.46; 95 % CI, 0.36 to 4.55; P = 0.02), and the ABCB1 C3435T variant in homozygotes was correlated with decreases in LDL-C (CC vs. TT: MD, 2.29; 95 % CI, 0.37 to 4.20; P = 0.02) as well as TC (CC vs. TT: MD, 3.05; 95 % CI, 0.58 to 5.53; P = 0.02) in patients treated with statin. However, we did not observe a significant association in the TG group or an association between other genetic models serum lipid parameters. In addition, statin treatment more than 5 months led to a higher risk of muscle toxicity.

CONCLUSIONS

The evidence from the meta-analysis demonstrated that the ABCB1 C3435T polymorphism may represent a pharmacogenomic biomarker for predicting treatment outcomes in patients on statins and that statin treatment for more than 5 months can increase the risk of myopathy.

Type of LDLR mutation and the pharmacogenetics of familial hypercholesterolemia treatment

Familial hypercholesterolemia (FH) is an autosomal dominant disease mainly caused by mutations in the low-density lipoprotein receptor (LDLR) gene. FH patients present a wide variability regarding response to drugs and they are usually undertreated. Here, we review studies that evaluated the association between the type of LDLR mutation and the response to lipid-lowering therapy. The main findings were that patients with a null LDLR mutation had: higher baseline LDL-C, higher LDL-C after drug therapy, lower proportion of patients within the LDL-C target value and higher frequencies of CVD. Thus, we conclude that FH patients harboring a null mutation have a trend to an increased risk, even if diagnosis is early established and lipid-lowering treatment instituted. It is suggested that these individuals may benefit from the use of newly approved lipid-lowering agents.

The MYLIP p.N342S polymorphism is associated with response to lipid-lowering therapy in Brazilian patients with familial hypercholesterolemia

Supplemental Digital Content is available in the text.

Background

A previous study reported that the myosin regulatory light chain interacting protein (MYLIP) might serve as a novel therapeutic class for treating dyslipidemia. It contributes to variations in the levels of circulating low-density lipoprotein cholesterol (LDL-C), promoting the degradation of LDL–LDLR, thus limiting absorption. The effect of genetic variation in the MYLIP gene in a disease scenario characterized by mutations in the LDLR gene has not been previously evaluated.

Objective

The aim of this study was to assess the effect of the p.N342S variant on the response to lipid-lowering therapy in Brazilian patients with heterozygous familial hypercholesterolemia (FH).

Patients and methods

A total of 156 patients with heterozygous FH were followed up for 12 months and received lipid-lowering therapy (different doses of atorvastatin with the addition of ezetimibe in over half the patients of each genotype group). Cholesterol data were assessed, and analysis of the MYLIP rs9370867 (p.N342S) genotypes was carried out by melting curve analysis.

Results

Baseline total cholesterol and baseline LDL-C levels were not different between genotypes. After 1 year of treatment, LDL-C responses (expressed as mg/dl and as %) were significantly different among genotypes (AA: −79±68 and −39±27, GA: −60±79 and −27±32, and GG: −30±83 and −15±38; P=0.02 and 0.005, respectively). In addition, FH patients carrying the AA genotype were more likely to achieve LDL-C levels of less than 130 mg/dl after 1 year of treatment (75.0%) compared with patients with the GG and GA genotypes (34.5 and 34.8%, respectively; P=0.001).

Conclusion

Our study indicates that MYLIP p.N342S might be a pharmacogenetic marker for lipid-lowering therapy in patients with FH.

Recent advances in the understanding and care of familial hypercholesterolaemia: significance of the biology and therapeutic regulation of proprotein convertase subtilisin/kexin type 9

Familial hypercholesterolaemia (FH) is an autosomal co-dominant disorder that markedly raises plasma low-density lipoprotein-cholesterol (LDL-C) concentration, causing premature atherosclerotic coronary artery disease (CAD). FH has recently come under intense focus and, although there is general consensus in recent international guidelines regarding diagnosis and treatment, there is debate about the value of genetic studies. Genetic testing can be cost-effective as part of cascade screening in dedicated centres, but the full mutation spectrum responsible for FH has not been established in many populations, and its use in primary care is not at present logistically feasible. Whether using genetic testing or not, cholesterol screening of family members of index patients with an abnormally raised LDL-C must be used to determine the need for early treatment to prevent the development of CAD. The metabolic defects in FH extend beyond LDL, and may affect triacylglycerol-rich and high-density lipoproteins, lipoprotein(a) and oxidative stress. Achievement of the recommended targets for LDL-C with current treatments is difficult, but this may be resolved by new drug therapies. Lipoprotein apheresis remains an effective treatment for severe FH and, although expensive, it costs less than the two recently introduced orphan drugs (lomitapide and mipomersen) for homozygous FH. Recent advances in understanding of the biology of proprotein convertase subtilisin/kexin type 9 (PCSK9) have further elucidated the regulation of lipoprotein metabolism and led to new drugs for effectively treating hypercholesterolaemia in FH and related conditions, as well as for treating many patients with statin intolerance. The mechanisms of action of PCSK9 inhibitors on lipoprotein metabolism and atherosclerosis, as well as their impact on cardiovascular outcomes and cost-effectiveness, remain to be established.

Do MDR1 and SLCO1B1 polymorphisms influence the therapeutic response to atorvastatin? A study on a cohort of Egyptian patients with hypercholesterolemia

BACKGROUND

Statins are among the most prescribed drugs worldwide to reduce the risk of cardiovascular events. Interindividual variability in drug response is a major clinical problem and is of concern during drug development. Statins, such as atorvastatin, are taken orally and access to their site of action in the liver is greatly facilitated by both intestinal and hepatic transporters.

OBJECTIVE

To examine the impact of polymorphisms of the multidrug resistance 1(MDR1) and solute carrier organic anion transporter 1B1 (SLCO1B1) genes on the therapeutic response to atorvastatin as well as the presence of gender-gene interaction.

METHODS

Serum lipid levels were determined at baseline and 4 weeks following 40 mg/day atorvastatin treatment in 50 Egyptian hypercholesterolemic patients (27 males and 23 females). Identification of MDR1 C3435T and SLCO1B1 A388G gene polymorphisms was performed using a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method.

RESULTS

Treatment with atorvastatin resulted in a mean reduction of total cholesterol (TC), low density lipoprotein cholesterol (LDL-C), and triglyceride (TG) of 8.7 %, 9.2 %, and 4.1 %, respectively, and a mean increase of high density lipoprotein cholesterol (HDL-C) of 1 %. Baseline and post-treatment HDL-C levels were statistically significantly higher in the MDR 1 TT homozygotes when compared with the CC wild type. The percentage change in TC, LDL-C, TG, and HDL-C did not show any statistically significant difference when compared among the different MDR 1 C3435T or SLCO1B1 A388G genotypes. The SLCO1B1 GG homozygotes showed a decrease in TG, whereas there was an increase in TG following atorvastatin treatment in AA and AG carriers in females; however, males did not show any statistically significant difference. There was no statistically significant association between either the coronary artery disease (CAD) risk factors (family history of CAD, hypertension, diabetes mellitus, smoking) or concomitant medications with the percentage change in different lipid parameters.

CONCLUSION

MDR1 C3435T was associated with baseline and post-treatment HDL-C variation. SLCO1B1 A388G showed gender-related effects on TG change following atorvastatin treatment. None of the comorbidities or the concomitant medications influenced the percentage change of lipid parameters following atorvastatin treatment. The results of this study may lead to an improved understanding of the genetic determinants of lipid response to atorvastatin treatment.

Association between statin-induced creatine kinase elevation and genetic polymorphisms in SLCO1B1, ABCB1 and ABCG2

PURPOSE

Treatment with statins requires close monitoring of serum creatine kinase (CK) levels to prevent myopathy, a common and potentially serious dose-dependent adverse effect of these drugs. We have investigated the correlation between elevated CK levels and polymorphisms in the genes encoding transporters involved in statin disposition.

METHODS

Patients with and without statin-induced elevated serum CK levels were genotyped for polymorphisms in SLCO1B1 (SLCO1B1 A388G and SLCO1B1 T521C), ABCB1 (ABCB1 C1236T and ABCB1 C3435T) and ABCG2 (ABCG2 C421A).

RESULTS

Patients carrying SLCO1B1 T521C or ABCB1 C1236T single nucleotide polymorphisms (SNPs) had an odds ratio (OR) for statin-induced elevated serum CK levels of 8.86 (p<0.01) and 4.67 (p<0.05), respectively, while patients carrying the SLCO1B1 A388G SNP had an OR of 0.24 (p<0.05). An arbitrary score based on genotype combination discriminated patients with and without CK elevation at a specificity of 97 % and a sensitivity of 39 %.

CONCLUSION

Genotyping of the SLCO1B1, ABCB1 and ABCG2 genes deserves consideration as a clinical approach to improve statin safety while concomitantly reducing the burden of blood tests for CK measurements.

Pharmacogenomics of high-density lipoprotein-cholesterol-raising therapies

High levels of HDL cholesterol (HDL-C) have traditionally been linked to lower incidence of cardiovascular disease, prompting the search for effective and safe HDL-C raising pharmaceutical agents. Although drugs such as niacin and fibrates represent established therapeutic approaches, HDL-C response to such therapies is variable and heritable, suggesting a role for pharmacogenomic determinants. Multiple genetic polymorphisms, located primarily in genes encoding lipoproteins, cholesteryl ester transfer protein, transporters and CYP450 proteins have been shown to associate with HDL-C drug response in vitro and in epidemiologic studies. However, few of the pharmacogenomic findings have been independently validated, precluding the development of clinical tools that can be used to predict HDL-C response and leaving the goal of personalized medicine to future efforts.

Associations of ABCB1 and IL-10 genetic polymorphisms with sirolimus-induced dyslipidemia in renal transplant recipients

BACKGROUND

Hyperlipidemia is a common adverse effect of sirolimus (SRL). We previously showed significant associations of ABCB1 3435C>T and IL-10 -1082G>A with log-transformed SRL dose-adjusted weighted-normalized trough. We further examined to see whether these polymorphisms were also associated with SRL-induced dyslipidemia.

METHODS

Genotyping was performed for ABCB1 1236C>T, 2677 G>T/A, and 3435C>T; CYP3A4 -392A>G; CYP3A5 6986A>G and 14690G>A; IL-10 -1082G>A; TNF -308G>A; and ApoE ε2, ε3, and ε4 alleles. The longitudinal changes of total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), and triglyceride (TG) levels after SRL treatment before statin therapy were analyzed by a linear mixed-effects model, with adjustments for selected covariates for each lipid.

RESULTS

Under the dominant genetic model, ABCB1 3435C>T was associated with TC (P=0.0001) and LDL-C (P<0.0001) values after SRL administration. Mean TC and LDL-C levels were 26.9 and 24.9 mg/dL higher, respectively, in ABCB1 3435T carriers than 3435CC homozygotes at an average SRL trough concentration of 4 ng/mL without concomitant medication. ABCB1 1236C>T under the recessive model and IL-10 -1082G>A under the dominant model were associated with log-transformed TG values (P=0.0051 and 0.0436, respectively). Mean TG value was 25.1% higher in ABCB1 1236TT homozygotes compared with ABCB1 1236C carriers and was 12.4% higher in IL-10 -1082AA homozygotes than -1082G carriers.

CONCLUSIONS

ABCB1 polymorphisms were found to be associated with lipid responses to SRL treatment, confirming the role of ABCB1 gene in SRL pharmacokinetics and pharmacodynamics. Further studies are necessary to define the role of ABCB1 and IL-10 polymorphisms on SRL-induced dyslipidemia in renal transplantation.

Lipid-lowering effect of fluvastatin in relation to cytochrome P450 2C9 variant alleles frequently distributed in the Czech population

Background

CYP2C9*3 allele has been reported to correlate with increased plasma concentration of fluvastatin active form in healthy volunteers. We analyzed the correlation between the CYP2C9 genotype and cholesterol-lowering effect of fluvastatin in human hypercholesterolemic patients.

Material/Methods

The study was prospective, without any interventions to standard procedures of hypolipidemic treatment. CYP2C9 genotype was determined by PCR–RFLP assay in 87 patients on concomitant fluvastatin therapy, in 48 patients on monotherapy, and in a control group of 254 healthy volunteers of Czech nationality. Biochemical and clinical data were collected before the initiation of fluvastatin treatment and 12 weeks later.

Results

The frequency of CYP2C9 alleles did not differ significantly among groups of patients and volunteers. The most frequently observed allele was CYP2C9*2.

Treatment with 80 mg of fluvastatin daily of 48 patients on monotherapy for 12 weeks resulted in mean low-density lipoprotein cholesterol (LDL-C) reduction by 25%, mean serum total cholesterol (TC) reduction by 21%, and mean triglyceride (TG) reduction by 28%. The CYP2C9*1/*3 genotype was associated with a decrease in LDL-C levels (by 40.0% for CYP2C9*1/*3, but only by 22.4% for CYP2C9*1/*1), and with the reduction of TC (by 28.6% in CYP2C9*1/*3 versus 20.2% in CYP2C9*1/*1).

Conclusions

In hypercholesterolemic patients, LDL-C serum concentration was decreased more significantly in fluvastatin-treated subjects bearing the CYP2C9*1/*3 genotype compared to CYP2C9*1/*1 genotype. However, due to rare occurrence of some CYP genotypes, it was impossible to report a definitive positive genotype-fluvastatin effect association.

Gene-wide characterization of common quantitative trait loci for ABCB1 mRNA expression in normal liver tissues in the Chinese population

In order to comprehensively screen genetic variants leading to differential expression of the important human ABCB1 gene in the primary drug-metabolizing organ, ABCB1 mRNA expression levels were measured in 73 normal liver tissue samples from Chinese subjects. A set of Tag SNPs. were genotyped. In addition, imputation was performed within a 500 kb region around the ABCB1 gene using the reference panels of 1,000 Genome project and HapMap III. Bayesian regression was used to assess the strength of associations by compute Bayes Factors for imputed SNPs. Through imputation and linkage disequilibrium analysis, the imputed loci rs28373093, rs1002205, rs1029421, rs2285647, and rs10235835, may represent independent and strong association signals. rs28373093, a polymorphism 1.5 kb upstream from the ABCB1 transcription start site, has the strongest association. 2677 G>A/T and 3435C>T confer a clear gene-dosage effect on ABCB1 mRNA expression. The systematic characterization of gene-wide common quantitative trait loci associated with ABCB1 mRNA expression in normal liver tissues would provide the candidate markers to ABCB1-relevant clinical phenotypes in Chinese population.

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.

The C3435T polymorphism in ABCB1 influences atorvastatin efficacy and muscle symptoms in a high-risk vascular cohort

OBJECTIVE

The CC genotype of the C3435T polymorphism in ABCB1 is associated with increased P-glycoprotein expression, reduced low-density lipoprotein cholesterol (LDL-C) response to atorvastatin, and a reduced area-under-the-curve in pharmacokinetic studies. We sought to assess the relationship between 1) genotype and Atorvastatin efficacy, independently of variation in cholesterol metabolism and 2) genotype and myalgia.

METHODS

High-risk vascular patients were genotyped and treated with atorvastatin 80 mg for 6 weeks. The lipid panel and percent LDL-C reduction with atorvastatin were related to C3435T genotype. Genotypes and allele frequency were assessed in patients with and without myalgia.

RESULTS

A total of 117 patients were recruited and genotyped. Of these, 98 completed the study with adequate atorvastatin adherence, and 10 reported myalgia. T and C allele frequencies were 0.63 and 0.37, respectively. A 6-week course of atorvastatin (80 mg/day) reduced LDL-C by 58% ± 11% (mean ± SD). Patients with the CC genotype showed less LDL-C reduction with atorvastatin compared with the TT/TC genotype (53% vs 59%, respectively, P = .034), and this finding was independent of variation in cholesterol metabolism (P = .045 after correction for desmosterol and cholestanol/cholesterol ratio). The T allele was more frequent in patients with myalgia than those without (0.80 vs 0.62) and the C allele less frequent (0.20 vs 0.38, P = .043).

CONCLUSION

In patients treated with atorvastatin, the CC genotype at the C3435T polymorphism in ABCB1 is associated with reduced atorvastatin efficacy independently of cholesterol metabolism. The T allele is more frequent and the C allele less frequent in patients with myalgia.

Localization of genes for V+LDL plasma cholesterol levels on two diets in the opossum Monodelphis domestica

Plasma cholesterol levels among individuals vary considerably in response to diet. However, the genes that influence this response are largely unknown. Non-HDL (V+LDL) cholesterol levels vary dramatically among gray, short-tailed opossums fed an atherogenic diet, and we previously reported that two quantitative trait loci (QTLs) influenced V+LDL cholesterol on two diets. We used hypothesis-free, genome-wide linkage analyses on data from 325 pedigreed opossums and located one QTL for V+LDL cholesterol on the basal diet on opossum chromosome 1q [logarithm of the odds (LOD) = 3.11, genomic P = 0.019] and another QTL for V+LDL on the atherogenic diet (i.e., high levels of cholesterol and fat) on chromosome 8 (LOD = 9.88, genomic P = 5 x 10(-9)). We then employed a novel strategy involving combined analyses of genomic resources, expression analysis, sequencing, and genotyping to identify candidate genes for the chromosome 8 QTL. A polymorphism in ABCB4 was strongly associated (P = 9 x 10(-14)) with the plasma V+LDL cholesterol concentrations on the high-cholesterol, high-fat diet. The results of this study indicate that genetic variation in ABCB4, or closely linked genes, is responsible for the dramatic differences among opossums in their V+LDL cholesterol response to an atherogenic diet.

No significant effect of ABCB1 haplotypes on the pharmacokinetics of fluvastatin, pravastatin, lovastatin, and rosuvastatin

AIMS

This study aimed to investigate possible effects of ABCB1 genotype on fluvastatin, pravastatin, lovastatin, and rosuvastatin pharmacokinetics.

METHODS

In a fixed-order crossover study, 10 healthy volunteers with the ABCB1 c.1236C/C-c.2677G/G-c.3435C/C (CGC/CGC) genotype and 10 with the c.1236T/T-c.2677T/T-c.3435T/T (TTT/TTT) genotype ingested a single 20-mg dose of fluvastatin, pravastatin, lovastatin, and rosuvastatin. Plasma fluvastatin, pravastatin, and lovastatin concentrations were measured up to 12 h and plasma and urine rosuvastatin concentrations up to 48 and 24 h, respectively.

RESULTS

The ABCB1 genotype had no significant effect on the pharmacokinetics of any of the investigated statins. The geometric mean ratio (95% confidence interval) of the area under the plasma concentration-time curve from 0 h to infinity (AUC(0-infinity)) in participants with the TTT/TTT genotype to that in those with the CGC/CGC genotype was 0.96 (0.77, 1.20; P= 0.737) for fluvastatin, 0.92 (0.53, 1.62; P= 0.772) for pravastatin, 0.83 (0.36, 1.90; P= 0.644) for lovastatin, 1.25 (0.72, 2.17; P= 0.400) for lovastatin acid, and 1.10 (0.73, 1.65; P= 0.626) for rosuvastatin. The AUC(0-infinity) of lovastatin acid correlated significantly with that of rosuvastatin (r= 0.570, P= 0.009), but none of the other AUC(0-infinity) pairs showed a significant correlation.

CONCLUSIONS

These data suggest that the ABCB1 c.1236C-c.2677G-c.3435C and c.1236T-c.2677T-c.3435T haplotypes play no significant role in the interindividual variability in the pharmacokinetics of fluvastatin, pravastatin, lovastatin, and rosuvastatin.

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.

Common variation in the CETP gene and the implications for cardiovascular disease and its treatment: an updated analysis

Human plasma contains cholesteryl ester transfer protein (CETP) which, besides other functions, enables the transfer of cholesteryl esters in plasma from high-density lipoproteins (HDL) towards triglyceride-rich lipoproteins, thereby contributing to lower HDL cholesterol. Variations in the CETP gene, including the intronic TaqIB polymorphism (rs708272), are common in the population. Although HDL cholesterol is approximately 10% higher in TaqIB B2B2 than in B1B1 carriers, the association of this polymorphism with cardiovascular disease has not been unequivocally established. We present an updated pooled analysis concerning the association of cardiovascular disease with the TaqIB polymorphism, including only studies that predominantly comprise Caucasian subjects. The distribution of this CETP genotype was observed to be different in population-based studies (n = 10,526) compared with studies in populations selected by high cardiovascular risk (n = 10,947), with B2B2 carriers being less frequent among cases from high-risk populations compared with cases from population-based studies (p = 0.0009 for the difference in genotype distribution). In population-based studies, the odds ratio (OR) for cardiovascular disease was found to be 1.45 (95% CI: 1.07–1.95) in B2B2 compared with B1B1 carriers, contrasting the lower OR of 0.84 (95% CI: 0.74–0.96) in B2B2 versus B1B1 carriers from high-risk populations. Thus, it is possible that in the general population, the B2 allele is associated with higher cardiovascular risk, despite higher HDL cholesterol. Our analysis agrees with the contention that selection towards a lower frequency of B2B2 homozygotes may have occurred in selected populations, which would result in a apparently protective effect of the B2 allele when determined in high-risk populations. We also evaluated whether the TaqIB polymorphism would predict efficacy of lipid-lowering treatment with respect to plasma lipids and cardiovascular outcome, but the results of published studies were contradictory. Likewise, no definite conclusion can be made at present concerning the effect of this CETP polymorphism on the lipid response to diet intervention.

ABC multidrug transporters: structure, function and role in chemoresistance

Three ATP-binding cassette (ABC)-superfamily multidrug efflux pumps are known to be responsible for chemoresistance; P-glycoprotein (ABCB1), MRP1 (ABCC1) and ABCG2 (BCRP). These transporters play an important role in normal physiology by protecting tissues from toxic xenobiotics and endogenous metabolites. Hydrophobic amphipathic compounds, including many clinically used drugs, interact with the substrate-binding pocket of these proteins via flexible hydrophobic and H-bonding interactions. These efflux pumps are expressed in many human tumors, where they likely contribute to resistance to chemotherapy treatment. However, the use of efflux-pump modulators in clinical cancer treatment has proved disappointing. Single nucleotide polymorphisms in ABC drug-efflux pumps may play a role in responses to drug therapy and disease susceptibility. The effect of various genotypes and haplotypes on the expression and function of these proteins is not yet clear, and their true impact remains controversial.

Pharmacogenetics of response to statins

The 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase inhibitors (statins) are among the most commonly prescribed drugs worldwide. On average, statins improve lipid profiles and have been shown to have ancillary beneficial effects on inflammation, platelet activity, and endothelial function. However, variability in drug response exists regardless of the measured phenotype, and genetic variability may be a contributing factor. Recently, there has been an interesting shift in statin pharmacogenetic studies. Novel study designs have been employed and nontraditional candidate genes have been investigated in relation to both lipid and nonlipid responses to statins. This review outlines earlier pharmacogenetic studies and highlights newly published findings that expand on previous work. Furthermore, a framework is provided in which the necessary next steps in research are described, with the ultimate goal of translating pharmacogenetic findings into clinically meaningful changes in patient care.

Isolation of microarray-grade total RNA, microRNA, and DNA from a single PAXgene blood RNA tube

We have developed a procedure for isolation of microRNA and genomic DNA in addition to total RNA from whole blood stabilized in PAXgene Blood RNA tubes. The procedure is based on automatic extraction on a BioRobot MDx and includes isolation of DNA from a fraction of the stabilized blood and recovery of small RNA species that are otherwise lost. The procedure presented here is suitable for large-scale experiments and is amenable to further automation. Procured total RNA and DNA was tested using Affymetrix Expression and single-nucleotide polymorphism GeneChips, respectively, and isolated microRNA was tested using spotted locked nucleic acid-based microarrays. We conclude that the yield and quality of total RNA, microRNA, and DNA from a single PAXgene blood RNA tube is sufficient for downstream microarray analysis.

A novel BRCA-1 mutation in Arab kindred from east Jerusalem with breast and ovarian cancer

BACKGROUND

The incidence of breast cancer (BC) in Arab women is lower compared to the incidence in the Jewish population in Israel; still, it is the most common malignancy among Arab women. There is a steep rise in breast cancer incidence in the Arab population in Israel over the last 10 years that can be attributed to life style changes. But, the younger age of BC onset in Arab women compared with that of the Jewish population is suggestive of a genetic component in BC occurrence in that population.

METHODS

We studied the family history of 31 women of Palestinian Arab (PA) origin affected with breast (n = 28), ovarian (n = 3) cancer. We used denaturing high performance liquid chromatography (DHPLC) to screen for mutations of BRCA1/2 in 4 women with a personal and family history highly suggestive of genetic predisposition.

RESULTS

A novel BRCA1 mutation, E1373X in exon 12, was found in a patient affected with ovarian cancer. Four of her family members, 3 BC patients and a healthy individual were consequently also found to carry this mutation. Of the other 27 patients, which were screened for this specific mutation none was found to carry it.

CONCLUSION

We found a novel BRCA1 mutation in a family of PA origin with a history highly compatible with BRCA1 phenotype. This mutation was not found in additional 30 PA women affected with BC or OC. Therefore full BRCA1/2 screening should be offered to patients with characteristic family history. The significance of the novel BRCA1 mutation we identified should be studied in larger population. However, it is likely that the E1373X mutation is not a founder frequent mutation in the PA population.

ABCB1 genotype and PGP expression, function and therapeutic drug response: a critical review and recommendations for future research

The product of the ABCB1 gene, P-glycoprotein (PGP), is a transmembrane active efflux pump for a variety of drugs. It is a putative mechanism of multidrug resistance in a range of diseases. It is postulated that ABCB1 polymorphisms contribute to variability in PGP function, and that therefore multidrug resistance is, at least in part, genetically determined. However, studies of ABCB1 genotype or haplotype and PGP expression, activity or drug response have produced inconsistent results. This critical review of ABCB1 genotype and PGP function, including mRNA expression, PGP-substrate drug pharmacokinetics and drug response, highlights methodological limitations of existing studies, including inadequate power, potential confounding by co-morbidity and co-medication, multiple testing, poor definition of disease phenotype and outcomes, and analysis of multiple drugs that might not be PGP substrates. We have produced recommendations for future research that will aid clarification of the association between ABCB1 genotypes and factors related to PGP activity.