Pharmacogenomics and pharmacogenetics of cholesterol-lowering therapy

Association of HMGCR rs17671591 and rs3761740 with lipidemia and statin response in Uyghurs and Han Chinese

Background

Dyslipidemia plays a very important role in the occurrence and development of cardiovascular disease (CVD). Genetic factors, including single nucleotide polymorphisms (SNPs), are one of the main risks of dyslipidemia. 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) is not only the rate-limiting enzyme step of endogenous cholesterol production, but also the therapeutic target of statins.

Methods

We investigated 405 Han Chinese and 373 Uyghur people who took statins for a period of time, recorded their blood lipid levels and baseline data before and after oral statin administration, and extracted DNA from each subject for SNP typing of HMGCR rs17671591 and rs3761740. The effects of HMGCR rs17671591 and rs3761740 on lipid levels and the effect of statins on lipid lowering in Han Chinese and Uyghur ethnic groups were studied.

Results

In this study, for rs17671591, the CC vs. TT+CT model was significantly correlated with the level of LDL-C before oral statin in the Uyghur population, but there were no correlations between rs17671591 and the level of blood lipid before oral statin in the Han population. The CC vs. TT+CT and CT vs. CC+TT models were significantly correlated with the level of LDL-C after oral statin in the Uyghur population. There was no significant correlation between rs3761740 with blood lipids before and after oral statin in the Han population. For rs3761740, before oral statin, the CC vs. AA+CA model was significantly correlated with the level of LDL-C, and the CA vs. CC+AA model was significantly correlated with the level of total cholesterol (TC), low density lipoprotein cholesterol (LDL-C), and non-high density lipoprotein cholesterol (HDL-C) in the Uyghur population. After oral statin, the CC vs. AA+CA and CA vs. CC+AA models were significantly correlated with the level of TC, LDL-C, and apolipoprotein (APOB), and the C vs. A model was significantly correlated with the level of TC, triglyceride (TG), LDL-C, and APOB in the Uyghur population. Particularly, the CT vs. CC+TT model of rs17671591 was significantly correlated with the changes of LDL-C after oral statin in the Uyghur population. In this study, we also explored the association of rs17671591 and rs3761740 with the rate of dyslipidemia as a reference.

Conclusion

We found that HMGCR rs3761740 was correlated with the levels of TC, LDL-C, and non-HDL-C before and after oral statin in Uyghurs, but not with blood lipid levels in the Han population. In the Uyghur population, HMGCR rs17671591 was associated with the level of LDL-C before and after oral statin, and also affected the changes of LDL-C after oral statin.

Association of cytochromes P450 3A4*22 and 3A5*3 genotypes and polymorphism with response to simvastatin in hypercholesterolemia patients

BACKGROUNDS

Inter-individual variability in response to statin was mainly due to genetic differences. This study aimed to investigate the association of CYP3A4*22 (rs35599367), CYP3A5*3 (rs776746) single nucleotide polymorphism (SNP) with response to simvastatin in hypercholesterolemia patients conducted at King Abdulaziz University hospital (KAUH) in Jeddah, Saudi Arabia.

PATIENTS AND METHODS

A total of 274 participants were registered in the current study. Hypercholesterolemic patients taking simvastatin 20 mg (n = 148) and control subjects (n = 126) were tested for rs35599367 and rs776746 genotypes using Custom Taqman ® Assay Probes. Response to simvastatin in these patients was assessed by determination of low density lipoprotein (LDL-C), total cholesterol (TC) and by measuring statin plasma levels using Liquid Chromatography-Mass Spectrometry (LC-MS).

RESULTS

None of the participants carried a homozygous CYP3A4*22 mutant genotype, while 12 (4.4%) individuals had a heterozygous genotype and 262 (95.6%) had a wild homozygous genotype. The CYP3A5*3 allele was detected in the homozygous mutant form in 16 (5.8%) individuals, while 74 (27.0%) individuals carried the heterozygous genotype and 184 (67.2%) carried the wildtype homozygous genotype. Of the patient group, 15 (11%) were classified as intermediate metabolizers (IMs) and 133 (89%) as extensive metabolizers (EMs). Plasma simvastatin concentrations for the combined CYP3A4/5 genotypes were significantly (P<0.05) higher in the IMs group than in the EMs group. TC and plasma LDL-C levels were also significantly (P<0.05) higher in IMs than in EMs.

CONCLUSION

The present study showed associations between CYP3A4*22 (rs35599367) and CYP3A5*3 (rs776746) SNP combination genotypes with response to statins in hypercholesterolemia. Patients who had either a mutant homozygous allele for CYP3A5*3 or mutant homozygous and heterozygous alleles for CYP3A4*22 showed increased response to lower TC and LDL-C levels.

High-Risk Polymorphisms Associated with the Molecular Function of Human HMGCR Gene Infer the Inhibition of Cholesterol Biosynthesis

HMG-CoA reductase or HMGCR (3-hydroxy-3-methylglutaryl-CoA reductase) is a rate-limiting enzyme involved in cholesterol biosynthesis. HMGCR plays an important role in the possible occurrence of hypercholesterolemia leading to atherosclerosis and coronary heart disease. This enzyme is a major target for cholesterol-lowering drugs such as "statin" which blocks the synthesis of mevalonate, a precursor for cholesterol biosynthesis. This study is aimed at characterizing deleterious mutations and classifying functional single nucleotide polymorphisms (SNPs) of the HMGCR gene through analysis of functional and structural evaluation, domain association, solvent accessibility, and energy minimization studies. The functional and characterization tools such as SIFT, PolyPhen, SNPs and GO, Panther, I-Mutant, and Pfam along with programming were employed to explore all the available SNPs in the HMGCR gene in the database. Among 6815 SNP entries from different databases, approximately 388 SNPs were found to be missense. Analysis showed that seven missense SNPs are more likely to have deleterious effects. A tertiary model of the mutant protein was constructed to determine the functional and structural effects of the HMGCR mutation. In addition, the location of the mutations suggests that they may have deleterious effects because most of the mutations are residing in the functional domain of the protein. The findings from the analysis predicted that rs147043821 and rs193026499 missense SNPs could cause significant structural and functional instability in the mutated proteins of the HMGCR gene. The findings of the current study will likely be useful in future efforts to uncover the mechanism and cause of hypercholesterolemia. In addition, the identified SNPs of HMGCR gene could set up a strong foundation for further therapeutic discovery.

Effect of Metformin and Simvastatin in Inhibiting Proadipogenic Transcription Factors

Obesity is a multifactorial chronic disease characterized by the excessive accumulation of fat in adipose tissue driven by hypertrophy and hyperplasia of adipocytes through adipogenesis. Adipogenesis plays a key role in the development of obesity and related metabolic disorders, which makes it potential target for the therapeutic approach to obesity. An increasing number of studies confirm the pleiotropic action of the combined treatment with metformin and statins, suggesting their anti-hypertensive, anti-inflammatory, and anti-adipogenic effect. The aim of this study was to analyze the effect of different doses of metformin (MET) and simvastatin (SIM) on the expression of key transcription factors of adipogenesis. Mouse 3T3-L1 preadipocytes were induced to differentiation in adipogenic medium with sustained MET and SIM treatment to assess the effect on adipogenesis. Nine days after initiating adipogenesis, the cells were prepared for further experiments, including Oil Red O staining, RT-PCR, Western blotting, and immunocytochemistry. Treating the cells with the combination of MET and SIM slightly reduced the intensity of Oil Red O staining compared with the control group, and down-regulated mRNA and protein expression of PPARγ, C/EBPα, and SREBP-1C. In conclusion, the inhibitory effect of MET and SIM on adipocyte differentiation, as indicated by decreased lipid accumulation, appears to be mediated through the down-regulation of adipogenic transcription factors, peroxisome proliferator-activated receptor γ (PPARγ), CCAAT/enhancer binding pro-tein α (C/EBPα), and sterol regulatory element-binding protein 1 (SREBP-1C).

Use of Pharmacogenetic Information in the Treatment of Cardiovascular Disease

BACKGROUND

In 1964, Robert A. O'Reilly's research group identified members of a family who required remarkably high warfarin doses (up to 145 mg/day, 20 times the average dose) to achieve appropriate anticoagulation. Since this time, pharmacogenetics has become a mainstay of cardiovascular science, and genetic variants have been implicated in several fundamental classes of medications used in cardiovascular medicine.

CONTENT

In this review, we discuss genetic variants that affect drug response to 3 classes of cardiovascular drugs: statins, platelet P2Y12 inhibitors, and anticoagulants. These genetic variations have pharmacodynamic and pharmacokinetic effects and have been shown to explain differences in drug response such as lipid lowering, prevention of cardiovascular disease, and prevention of stroke, as well as incidence of adverse events such as musculoskeletal side effects and bleeding. Several groups have begun to implement pharmacogenetics testing as part of routine clinical care with the goal of improving health outcomes. Such strategies identify both patients at increased risk of adverse outcomes and alternative strategies to mitigate this risk as well as patients with “normal” genotypes, who, armed with this information, may have increased confidence and adherence to prescribed medications. While much is known about the genetic variants that underlie these effects, translation of this knowledge into clinical practice has been hampered by difficulty in implementing cost-effective, point-of-care tools to improve physician decision-making as well as a lack of data, as of yet, demonstrating the efficacy of using genetic information to improve health.

SUMMARY

Many genetic variants that affect individual responses to drugs used in cardiovascular disease prevention and treatment have been described. Further study of these variants is needed before successful implementation into clinical practice.

Fluvastatin Suppresses Mast Cell and Basophil IgE Responses: Genotype-Dependent Effects

Mast cell (MC)- and basophil-associated inflammatory diseases are a considerable burden to society. A significant portion of patients have symptoms despite standard-of-care therapy. Statins, used to lower serum cholesterol, have immune-modulating activities. We tested the in vitro and in vivo effects of statins on IgE-mediated MC and basophil activation. Fluvastatin showed the most significant inhibitory effects of the six statins tested, suppressing IgE-induced cytokine secretion among mouse MCs and basophils. The effects of fluvastatin were reversed by mevalonic acid or geranylgeranyl pyrophosphatase, and mimicked by geranylgeranyl transferase inhibition. Fluvastatin selectively suppressed key FcεRI signaling pathways, including Akt and ERK. Although MCs and basophils from the C57BL/6J mouse strain were responsive to fluvastatin, those from 129/SvImJ mice were completely resistant. Resistance correlated with fluvastatin-induced upregulation of the statin target HMG-CoA reductase. Human MC cultures from eight donors showed a wide range of fluvastatin responsiveness. These data demonstrate that fluvastatin is a potent suppressor of IgE-mediated MC activation, acting at least partly via blockade of geranyl lipid production downstream of HMG-CoA reductase. Importantly, consideration of statin use for treating MC-associated disease needs to incorporate genetic background effects, which can yield drug resistance.

HMGCR rs17671591 SNP Determines Lower Plasma LDL-C after Atorvastatin Therapy in Chilean Individuals

Lipid-lowering response to statin therapy shows large interindividual variability. At a genome-wide significance level, single nucleotide polymorphisms (SNPs) in PCSK9 and HMGCR have been implicated in this differential response. However, the influence of these variants is uncertain in the Chilean population. Hence, we aimed to evaluate the contribution of PCSK9 rs7552841 and HMGCR rs17671591 SNPs as genetic determinants of atorvastatin response in Chilean hypercholesterolaemic individuals. One hundred and one hypercholesterolaemic patients received atorvastatin 10 mg/day for 4 weeks. Plasma lipid profile (TC, HDL-C, LDL-C and TG) was determined before and after statin treatment, and SNPs were identified by allelic discrimination using TaqMan(®) SNP Genotyping Assays. Adjusted univariate and multivariate analyses' models were used for statistical analyses, and a p-value <0.05 was considered significant. From baseline (week 0) to the study end-point (week 4), significant reductions were observed in plasma TC, LDL-C and TG (p < 0.001), while HDL-C levels were increased (p < 0.001). Multivariate analysis showed no association between lipid levels and atorvastatin therapy for the PCSK9 variant. However, the HMGCR rs17671591 T allele contributed to basal HDL-C concentration variability along with a higher increase in this lipid fraction after statin medication. In addition, this allele determined greater plasma LDL-C reductions after therapy with atorvastatin. Our data suggest that the HMGCR rs17671591 polymorphism can constitute a genetic marker of lower plasma LDL-C and enhanced HDL-C concentration after atorvastatin therapy in the Chilean population.

Lipid attainment among patients newly treated with lipid-altering drugs

OBJECTIVE

Guidelines for preventing and treating patients with coronary artery disease have traditionally focused on reducing low-density lipoprotein cholesterol (LDL-C). Current treatments are effective; however, previous studies have identified a significant proportion of patients that are not achieving the recommended lipid levels. New guidelines were introduced November 2013. The objective of this study was to examine recent practice patterns and factors related to initiating treatment for hypercholesterolemia, which provides a comparative baseline to the introduction of new guidelines.

RESEARCH DESIGN AND METHODS

We conducted a retrospective cohort analysis utilizing laboratory results of lipid profiles and medical claims from January 2007 to September 2011 to identify patients with elevated LDL-C and diagnoses of hypercholesterolemia without prior pharmacotherapy. Pharmacotherapy dispensed, treatment modifications, LDL-C-goal attainment, and potential drug intolerance were evaluated.

RESULTS

Overall, among newly treated patients, 70.9% achieved the recommended LDL-C level within the first year of treatment; however, only 19.4% of those with coronary heart disease (CHD) or CHD risk equivalents achieved the more aggressive LDL-C goal of <70 mg/dL (1.8 mmol/L). LDL-C goals were generally achieved with the use of statins; however, a majority of patients underwent treatment modification(s) (e.g., discontinuation or restart). More than half of the patients diagnosed with elevated LDL-C did not initiate pharmacotherapy.

LIMITATIONS

Data was unavailable for inpatient hospitalizations, family history of cardiovascular diseases, body weight, and height, and likely under-reporting of smoking within claims data.

CONCLUSIONS

Newly treated patients with elevated LDL-C results generally achieved the recommended and risk-specific LDL-C goal with the use of lipid-altering drugs; however, there still exists a notable population of patients with CHD or CHD risk equivalents who were not treated to goal and a significant number of patients who do not receive lipid-lowering pharmacotherapy. New therapies and prescribing practices are warranted to adequately address these two patient populations.

Mechanisms and assessment of statin-related muscular adverse effects

Statin-associated muscular adverse effects cover a wide range of symptoms, including asymptomatic increase of creatine kinase serum activity and life-threatening rhabdomyolysis. Different underlying pathomechanisms have been proposed. However, a unifying concept of the pathogenesis of statin-related muscular adverse effects has not emerged so far. In this review, we attempt to categorize these mechanisms along three levels. Firstly, among pharmacokinetic factors, it has been shown for some statins that inhibition of cytochrome P450-mediated hepatic biotransformation and hepatic uptake by transporter proteins contribute to an increase of systemic statin concentrations. Secondly, at the myocyte membrane level, cell membrane uptake transporters affect intracellular statin concentrations. Thirdly, at the intracellular level, inhibition of the 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase results in decreased intracellular concentrations of downstream metabolites (e.g. selenoproteins, ubiquinone, cholesterol) and alteration of gene expression (e.g. ryanodine receptor 3, glycine amidinotransferase). We also review current recommendations for prescribers.

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.

Novel CYP3A4 intron 6 single nucleotide polymorphism is associated with simvastatin-mediated cholesterol reduction in the Rotterdam Study

OBJECTIVES

CYP3A4 is involved in the oxidative metabolism of many drugs and xenobiotics including the HMG-CoA reductase inhibitor simvastatin. The objective of this study was to investigate whether a new CYP3A4 functional single nucleotide polymorphism (SNP) in intron 6 (CYP3A4*22) modifies the effect of simvastatin on total cholesterol (TOTc) or LDL cholesterol (LDLc) reduction in a population-based cohort study.

METHODS

In a total of 80 incident simvastatin users, the association between the CYP3A4 intron 6 C>T SNP (rs35599367) and reduction in cholesterol levels was analyzed using linear regression analysis and adjusting for potential confounding factors.

RESULTS

The CYP3A4*22 allele was associated with a trend towards a stronger simvastatin lipid-lowering response, as reflected by the greater reduction in both TOTc and LDLc levels when compared with homozygous wild type. We observed that the CYP3A4*22 allele carriers had an increased reduction in TOTc and LDLc: -0.25 mmol/l (95% confidence interval [CI(95%)]=[-0.52; 0.01], P=0.058) and -0.29 mmol/l (CI(95%)=[-0.58; 0.01], P=0.054) when compared with homozygous CC. When we adjusted the model for potential confounding factors, the corresponding reduction in TOTc was -0.31 mmol/l (CI(95%)=[-0.59;-0.04], P=0.028) and for LDLc -0.34 mmol/l (CI(95%)=[-0.66; -0.02], P=0.034) greater for CYP3A4*22 allele carriers when compared with homozygotes wild type.

CONCLUSION

The CYP3A4*22 intron 6 SNP T-variant allele was associated with reduced CYP3A4 activity, resulting in a better lipid lowering response to simvastatin, when data were adjusted for confounding factors. This observation is a step towards the clarification of the reasons of interindividual variability in statins response and may potentially lead to improved tailoring of simvastatin therapy.

Use of NBD-cholesterol to identify a minor but NPC1L1-independent cholesterol absorption pathway in mouse intestine

The importance of Niemann-Pick C1 Like-1 (NPC1L1) protein in intestinal absorption of dietary sterols, including both cholesterol and phytosterols, is well documented. However, the exact mechanism by which NPC1L1 facilitates cholesterol transport remains controversial. This study administered 22-(N(-7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)-23,24-bisnor-5-cholen-3β-ol (NBD-cholesterol) and [(3)H]cholesterol to Npc1l1(+/+) and Npc1l1(-/-) mice to determine whether NPC1L1 facilitates dietary sterol uptake by enterocytes and/or participates in intracellular sterol delivery to the endoplasmic reticulum (ER) for lipoprotein assembly before secretion into plasma circulation. Results showed that [(3)H]cholesterol absorption was reduced but not abolished in Npc1l1(-/-) mice compared with Npc1l1(+/+) mice. In the presence of Pluronic L-81 to block pre-chylomicron exit from the ER, significant amounts of [(3)H]cholesterol were found to be associated with lipid droplets in the intestinal mucosa of both Npc1l1(+/+) and Npc1l1(-/-) mice, and the intracellular [(3)H]cholesterol can be esterified to cholesteryl esters. These results provided evidence indicating that the main function of NPC1L1 is to promote cholesterol uptake from the intestinal lumen but that it is not necessary for intracellular cholesterol transport to the ER. Surprisingly, NBD-cholesterol was taken up by intestinal mucosa, esterified to NBD-cholesteryl esters, and transported to plasma circulation to similar extent between Npc1l1(+/+) and Npc1l1(-/-) mice. Ezetimibe treatment also had no impact on NBD-cholesterol absorption by Npc1l1(+/+) mice. Thus, NBD-cholesterol absorption proceeds through an NPC1L1-independent and ezetimibe-insensitive sterol absorption mechanism. Taken together, these results indicate that NBD-cholesterol can be used to trace the alternative cholesterol absorption pathway but is not suitable for tracking NPC1L1-mediated cholesterol absorption.

Cholesteryl ester transfer protein gene and effectiveness of lipid lowering of atorvastatin

Cholesteryl ester transfer protein (CETP) plays a key role in lipid metabolism. Thus, variations in the CETP gene may be clinically relevant. Newly started atorvastatin users (n=212) were genotyped for CETP genetic variants (TaqIB and I405V). Homozygotes for B1 allele of TaqIB polymorphism had lower plasma high density lipoprotein cholesterol (HDL-C) compared with B1B2 or B2B2 genotypes (p=0.03, for each). Homozygotes for I allele of I405V polymorphism had lower plasma HDL-C compared with IV or VV genotypes (p=0.001, for each). In the whole population, the B1 carriers increased HDL-C levels by 4% after atorvastatin treatment, compared with B2 carriers, where a 4% decrease occurred (p=0.03). Also homozygotes for B1 allele decreased triglyceride levels to a lesser, though not significant, degree compared to B1B2 or B2B2 genotypes. CETP TaqIB or I405V polymorphisms seem to modify the lipid lowering response to atorvastatin treatment. This knowledge may help design more effective hypolipidaemic treatment.

Rhabdomyolysis: historical background, clinical, diagnostic and therapeutic features

Rhabdomyolysis, a term used to describe the rapid breakdown of striated muscle, is characterized by rupture and necrosis of muscle fibers. This process results in the release of cell breakdown products into the bloodstream and extracellular space. Although direct muscle injury remains the most common cause of muscle injury, additional causes include hereditary enzyme disorders, drugs, toxins, endocrinopathies, malignant hyperthermia, neuroleptic malignant syndrome, heatstroke, hypothermia, electrolyte alterations, diabetic ketoacidosis and non-ketotic hyperosmolar coma, severe hypo- or hyperthyroidism and bacterial or viral infections. The classic triad of symptoms includes muscle pain, weakness and dark urine, although more than 50% of the patients do not complain of muscle pain or weakness. Additional systemic symptoms include fever, general malaise, tachycardia, nausea and vomiting. The laboratory diagnosis is based essentially on the measurement of creatine kinase in serum or plasma. Plasma and urine myoglobin measurement might be useful in the early stages of the syndrome and for identifying a subset of patients with minor skeletal muscle injury. Patient monitoring is pivotal (the mortality rate is as high as 8%), and should be focused on preventing the detrimental consequences, that often include renal disease and coagulopathy. In the pre-hospital setting, forced hydration with 1.5-2 L of sterile saline solution should be started immediately, followed by 1.5-2 L/h. Following hospital admission, continuous hydration should be ensured, alternating the saline solution with a 5% glucose solution. In the presence of myoglobinuria, urine should be alkalinized by use of sodium bicarbonate solution. Clin Chem Lab Med 2010;48:749-56.

A single nucleotide polymorphism in the 3-hydroxy-3-methylglutaryl-coenzyme A reductase gene ( HMGCR) influences the serum triacylglycerol relationship with dietary fat and fibre in the European Prospective Investigation into Cancer and Nutrition in Norfolk (EPIC-Norfolk) study

The objective of the present study was to investigate the influence of the single nucleotide polymorphism (rs17238540) at the 3-hydroxy-3-methylglutaryl-coenzyme A reductase gene (HMGCR) on the relationship between serum lipids and dietary fat and fibre (NSP). FFQ and pyrosequencing were used to assess cross-sectional dietary intake and HMGCR genotype in a population study with data for serum lipids available. Genotype frequencies and allele distributions for 23 011 participants were: TT 95.65 %, TG 4.29 % and GG 0.06 %; T 97.8 % and G 2.2 %. In regression analyses, the TG+GG group showed a significant positive relationship between TAG and SFA intake (+0.11 (95 % CI 0.02, 0.20) mmol TAG/l; P = 0.017; per 3 % SFA energy increase) while the TT individuals showed no change in the TAG levels related to SFA intake ( - 0.0007 (95 % CI - 0.02, 0.02) mmol TAG/l; P = 0.99). TG+GG individuals showed an inverse relationship between TAG and fibre intake higher ( - 0.14 (95 % CI - 0.22, - 0.05) mmol TAG/l than the TT group ( - 0.04 (95 % CI - 0.06, - 0.02) mmol TAG/l). In both cases the respective coefficient regressions of TAG were different between the genotype groups (Z = 2.27, P = 0.023 for SFA intake; Z = 2.19, P = 0.029 for fibre intake). Individuals carrying the G allele may show a greater response in lower TAG levels with reduced SFA intake and increased fibre intake compared with those homozygous for the T allele. The effectiveness of different dietary interventions to control serum lipids may vary according to HMGCR genotype.

Decreased ubiquinone availability and impaired mitochondrial cytochrome oxidase activity associated with statin treatment

In order to investigate the potential involvement of mitochondrial electron transport chain (ETC) dysfunction in myotoxicity associated with 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor (statin) treatment, assessment was made of ETC activity and ubiquinone status in two patients experiencing myopathy following treatment with simvastatin (40 mg/day) and cyclosporin (patient 1) and simvastatin (40 mg/day) and itraconazole (patient 2). Analysis of skeletal muscle biopsies revealed a decreased ubiquinone status (77 and 132; reference range: 140-580 pmol/mg) and cytochrome oxidase (complex IV) activity (0.006 and 0.007 reference range: 0.014-0.034). To assess statin treatment in the absence of possible pharmacological interference from cyclosporin or itraconazole, primary astrocytes were cultured with lovastatin (100 microM). Lovastatin treatment resulted in a decrease in ubiquinone (97.9 +/- 14.9; control: 202.9 +/- 18.4 pmol/mg; p < 0.05), and complex IV activity (0.008 +/- 0.001; control: 0.011 +/- 0.001; p < 0.05) relative to control. These data, coupled with the patient findings, indicate a possible association between statin treatment, decreased ubiquinone status, and loss of complex IV activity.

Pharmacogenetic predictors of statin-mediated low-density lipoprotein cholesterol reduction and dose response

BACKGROUND

There is interindividual variation in low-density lipoprotein cholesterol (LDLc) lowering by statins and limited study into the genetic associations of the dose dependant LDLc lowering by statins.

METHODS AND RESULTS

Five hundred nine patients with hyperlipidemia were randomly assigned atorvastatin 10 mg, simvastatin 20 mg, or pravastatin 10 mg (low-dose phase) followed by 80 mg, 80 mg, and 40 mg (high-dose phase), respectively. Thirty-one genes in statin, cholesterol, and lipoprotein metabolism were sequenced and 489 single nucleotide polymorphisms with minor allele frequencies >2% were tested for associations with percentage LDLc lowering at low doses using multivariable adjusted general linear regression. Significant associations from the analysis at low dose were then repeated at high-dose statins. At low doses, only 1 single nucleotide polymorphism met our experiment-wide significance level, ABCA1 rs12003906. Twenty-six subjects carried the minor allele of rs12003906, which was associated with an attenuated LDLc reduction (LDLc reduction in carriers versus noncarriers -24.1+/-2.6% versus -32.2+/-1.5%; P=0.0001). In addition, we replicated the association with the APOE epsilon3 allele and a reduced LDLc reduction. At high doses, carriers of the minor allele of ABCA1 rs12003906 and the APOE epsilon3 allele improved their LDLc reduction but continued to have a diminished LDLc reduction compared with noncarriers (-30.5+/-4.0% versus -42.0+/-2.4%; P=0.005) and (-38.5+/-1.9% versus -45.3+/-2.8%; P=0.009), respectively.

CONCLUSIONS

An intronic single nucleotide polymorphism in ABCA1 and the APOE epsilon3 allele are associated with reduced LDLc lowering by statins and identify individuals who may be resistant to maximal LDLc lowering by statins.

CYP3A53A allele is associated with reduced lowering-lipid response to atorvastatin in individuals with hypercholesterolemia

BACKGROUND

The cytochrome P450 isoenzyme 3A5 (CYP3A5) has an important role on biotransformation of xenobiotics. CYP3A5 SNPs have been associated with variations on enzyme activity that can modify the metabolism of several drugs.

METHODS

In order to evaluate the influence of CYP3A5 variants on response to lowering-cholesterol drugs, 139 individuals with hypercholesterolemia were selected. After a wash-out period of 4 weeks, individuals were treated with atorvastatin (10 mg/day/4 weeks). Genomic DNA was extracted by a salting-out procedure. CYP3A5*3C, CYP3A5*6 and CYP3A5*1D were analyzed by PCR-RFLP and DNA sequencing.

RESULTS

>Frequencies of the CYP3A5*3C and CYP3A5*1D alleles were lower in individuals of African descent (*3C: 47.8% and *1D: 55.2%) than in non-Africans (*3C: 84.9% and *1D 84.8%, p<0.01). Non-Africans carrying *3A allele (*3C and *1D combined alleles) had lower total and LDL-cholesterol response to atorvastatin than non-*3A allele carriers (p<0.05).

CONCLUSION

CYP3A5*3A allele is associated with reduced cholesterol-lowering response to atorvastatin in non-African individuals.

Effect of ScrF I polymorphism in the 2nd intron of the HMGCR gene on lipid-lowering response to simvastatin in Chinese diabetic patients

OBJECTIVE

To investigate whether ScrF I polymorphism in the 2nd intron of the HMG-COA reductase gene (HMGCR) influences serum lipid levels and whether this polymorphism affects the efficiency of the cholesterol lowering HMG-CoA reductase inhibitor, simvastatin.

METHODS

One hundred sixty-eight patients with type 2 diabetes mellitus (T2DM) prospectively received simvastatin as a single-agent therapy (20mg day-1 p.o.) for 12 weeks. Serum lipid levels were determined before and after simvastatin treatment. Genotyping was performed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP).

RESULTS

Subjects with the AA homozygotes had significantly higher serum very low-density lipoprotein cholesterol (VLDL-C) levels than those with the aa homozygotes. In addition, in 168 patients with T2DM who took 20mg simvastatin, the VLDL-C lowering effect by simvastatin in subjects with the aa homozygotes was significantly lower than in those with the Aa heterozygotes and AA homozygotes.

CONCLUSIONS

Simvastatin treatment significantly decreased plasma lipids in all patients (P<0.01). Importantly, we demonstrate that ScrF I polymorphism of the HMGCR gene in patients with T2DM groups is associated with significant elevation of serum VLDL-C levels. Subjects with the AA homozygotes had significantly higher serum high VLDL-C levels than those with the Aa heterozygotes and aa homozygotes (AA: 2.18+/-0.51; Aa: 2.04+/-0.59, aa: 1.86+/-0.43, P<0.05 for comparison among three genotypes and P<0.01 for difference between AA and aa). Furthermore, this polymorphism tends to show an enhanced response to an HMG-CoA reductase inhibitor in terms of the cholesterol-lowering effect. In 168 patients with T2DM who took 20mg simvastatin, the VLDL-C lowering effect by simvastatin in subjects with the AA homozygotes was significantly lower than in those with the Aa heterozygotes and aa homozygotes (the reduction in serum VLDL-C levels; 37.03+/-5.67 versus 28.97+/-4.96, P<0.01; 34.62+/-5.87 versus 28.97+/-4.96, P<0.05). These results suggest that the HMGCR gene may serve as a modifier gene for hypercholesterolemia in Chinese diabetic patients.

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

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

Statins and myotoxicity: a therapeutic limitation

Hydroxymethylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors represent the most successful class of drugs for the treatment of hypercholesterolaemia and dyslipidaemia implicated in the pathogenesis of coronary heart disease and atherosclerosis. However, the popular profile of statins in terms of efficacy has been maligned by its adverse events. The myotoxicity, ranging from mild myopathy to serious rhabdomyolysis, associated with HMG-CoA reductase inhibitors, during treatment of hypercholesterolaemia is of paramount importance. Rhabdomyolysis is a rare but idiosyncratic muscle wasting disorder of different etiologies. Statin-associated rhabdomyolysis causes skeletal muscle injury by self-perpetuating events leading to fatal irreversible renal damage through a series of biochemical reactions. Preferential distribution and action of statins in liver could be the key to minimise myotoxicity concerns. Hepato-specific distribution of statins is governed by various factors such as physicochemical properties, pharmacokinetic properties and selective transporter-mediated uptake in liver rather in extrahepatic cells. The interactions of statins with concomitant drugs of different classes merit attention for their safety profile. Although pharmacokinetic as well as pharmacodynamic interactions have been implicated in pathophysiology of statin-induced muscle wasting, the underlying mechanism is not clearly understood. Besides, pharmacokinetic and phramcodynamic factors, statin-associated myotoxcity may also implicate pharmacogenomic factors. The pharmacogenomics characterised by CYP polymorphism and other genetic factors is responsible for inter-individual variations to efficacy and tolerability of statins. The pathophysiological mechanisms may include statin-induced differences in cholesterol:phospholipid ratio, isoprenoid levels, small GTP binding proteins and apoptosis. However, the present understanding of pathophysiological mechanisms, does not offer a reliable approach to address the same at preclinical level. Although statin-associated myotoxicity affects compliance, quality of life of patient and discontinuation rate, yet the low incidence of myotoxicty including rhabdomyolysis and less severity of commonly occurring myopathy and myalgia do not raise doubts about the clinical efficacy and tolerability of statins. Medical management of myotoxicity seems to be pivotal for the proper compliance of patients with statin treatment. The appropriate and judicious use of drugs would substantially reduce the likelihood of developing clinically important myopathy.

Effects of statins on the adipocyte maturation and expression of glucose transporter 4 (SLC2A4): implications in glycaemic control

AIMS/HYPOTHESIS

Hyperlipidaemia often occurs in patients with type 2 diabetes mellitus. Though HMG-CoA reductase inhibitors (statins) are widely used for controlling hypercholesterolemia, atorvastatin has also been reported to have an adverse effect on glucose metabolism. Based on these findings, the aim of this study was to investigate the effects of statins on adipocytes, which play pivotal roles in glucose metabolism.

METHODS

In 3T3-L1 cells, effects of statins on adipocyte maturation were determined morphologically. Protein and mRNA levels of SLC2A4 and adipocyte marker proteins were determined by immunoblotting and RT-PCR, respectively. Type 2 diabetic NSY mice were treated with atorvastatin for 15 weeks, followed by glucose and insulin tolerance tests and examination of SLC2A4 expression in white adipose tissue (WAT). Seventy-eight Japanese subjects with type 2 diabetes and hypercholesterolaemia were treated with atorvastatin (10 mg/day), and its effects on lipid and glycaemic profiles were measured 12 weeks after treatment initiation.

RESULTS

Treatment with atorvastatin inhibited adipocyte maturation, SLC2A4 and C/EBPalpha expressions and insulin action in 3T3-L1 cells. Atorvastatin also attenuated SLC2A4 and C/EBPalpha expressions in differentiated 3T3-L1 adipocytes. These effects were reversed by L. mevalonate or geranylgeranyl pyrophosphate. In NSY mice, atorvastatin accelerated glucose intolerance as a result of insulin resistance and decreased SLC2A4 expression in WAT. In addition to improving hyperlipidaemia, atorvastatin treatment significantly increased HbA(1c) but not fasting glucose levels in diabetic patients, and this effect was greater in the non-obese subgroup.

CONCLUSIONS/INTERPRETATION

These results demonstrate that atorvastatin attenuates adipocyte maturation and SLC2A4 expression by inhibiting isoprenoid biosynthesis, and impairs glucose tolerance. These actions of atorvastatin could potentially affect the control of type 2 diabetes.

The L162V polymorphism at the peroxisome proliferator activated receptor alpha locus modulates the risk of cardiovascular events associated with insulin resistance and diabetes mellitus: The Veterans Affairs HDL Intervention Trial (VA-HIT)

BACKGROUND

The Veterans Affairs HDL Intervention Trial (VA-HIT) showed that gemfibrozil, which activates peroxisome proliferator-activator receptor alpha (PPARalpha), significantly reduced the risk of cardiovascular (CV) events in men with low HDL cholesterol (< 40 mg/dl) and established coronary heart disease. Treatment was particularly beneficial in those with insulin resistance (IR) or diabetes mellitus (DM). We hypothesized that the association between a functional polymorphism at the PPARA locus (L162V) and the risk of a CV event, as well as response to fibrate therapy, might be greatest in those with either IR or DM (DM/IR) in VA-HIT.

METHODS AND RESULTS

A total of 827 men (placebo, n = 413; gemfibrozil, n = 414) from the VA-HIT were genotyped. This population included a high proportion of subjects with DM/IR. In VA-HIT, the PPARA V162 allele was associated with reduced levels of HDL cholesterol and the presence of DM/IR at baseline. It was also associated with reduced risk of CV events in those with DM/IR but not in those with neither (DM/IR *PPARA genotype, P = 0.005). Among subjects with DM/IR, treatment with gemfibrozil reduced CV events in non-carriers from 29.9 to 17.8% and carriers of the V162 allele from 14.7 to 4.8%. In contrast, carriers of the V162 allele with no DM/IR who were treated with gemfibrozil experienced significantly more CV events than did those who received placebo (20.6% versus 13.6%; P = 0.01).

CONCLUSIONS

The effect of the L162V polymorphism at the PPARA locus on CV risk depends on the presence of DM/IR. Among subjects treated with gemfibrozil, the V162 allele was associated not only with reduced CV risk in subjects with DM/IR, but also with significantly increased CV risk in the absence of these traits, identifying this genetic variant as a potential marker for predicting which subjects may have a favorable response to fibrate therapy.

Lovastatin-Induced Apoptosis in Macrophages through the Rac1/Cdc42/JNK Pathway

Statins, inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A reductase, have been used successfully in the treatment of hypercholesterolemia for more than a decade. Statins also exhibit overall clinical benefits on cardiovascular diseases independent of their effects on lowering serum cholesterol levels. These beneficial effects of statin therapy are believed to be due, at least in part, to the anti-inflammatory and immunomodulatory roles of statins. Statin treatment reduces the levels of inflammatory markers, decreases the activation and recruitment of immune cells, and delays the progression of atherosclerosis, a chronic inflammatory disease. However, little is known about the direct impact of statins on immune cells, particularly on macrophages. We report that lovastatin, a member of the statin family, effectively induces apoptosis in macrophages. Further investigation of the molecular mechanism has revealed that Rac1 and Cdc42, the small GTPase family members, may play an important role in lovastatin-induced macrophage apoptosis. Moreover, the activation of the JNK pathway may contribute to this event. Our findings provide a better understanding of the molecular basis underlying the anti-inflammatory clinical benefits of statin therapy in cardiovascular diseases.

Statin response and pharmacokinetics variants

Despite statin therapy being effective in the primary and secondary prevention of coronary heart disease, the benefit of treatment varies between individuals. Interindividual variations in pharmacokinetics play a central role in the cause of variability of drug disposition, and, in turn, the drug's clinical efficacy. Exploring genetic variations that influence pharmacokinetics may lead clinicians to apply the most efficient and safe drug therapy. So far, variants in eight candidate genes related to pharmacokinetics of statins have been investigated as the potential determinant of drug responsiveness or adverse event risk. All reported data remains inconclusive, but it has been suggested that combined analysis of more than two different polymorphisms, or a combination of genetic association and studies using in vitro recombinant expression techniques, may be more informative in predicting the specific phenotype of a genetic variant. Future studies using these approaches could provide more striking evidence, which may be sufficient to justify genetic analysis regarding pharmacokinetic variants in the clinical practice of statin therapy.

Pharmacogenomics in cardiovascular disease: the role of single nucleotide polymorphisms in improving drug therapy

Pharmacogenomics is the study of how an individual's genetic inheritance affects the body's response to drugs. Pharmacogenomics holds the promise that drugs might one day be tailor-made for individuals and adapted to an individual's genetic makeup. Several studies have shown that both adverse and beneficial responses to cardiovascular drugs can be influenced by single nucleotide polymorphisms in genes coding for metabolising enzymes, drug transporters and drug targets. Despite the large amount of data about gene-drug interactions, the translation of pharmacogenomics in clinical practise is slow. To improve this, there is a need of new technology and large prospective trials allowing for simultaneous analysis of multiple genetic variants in molecular pathways that could affect drug disposition and action.

Pharmacogenomics and cardiovascular drugs: need for integrated biological system with phenotypes and proteomic markers

Personalized medicine is based on a better knowledge of biological variability, considering the important part due to genetics. When trying to identify involved genes and their products in differential cardiovascular drug responses, a five-step strategy is to be followed: 1) Pharmacokinetic-related genes and phenotypes (2) Pharmacodynamic targets, genes and products (3) Cardiovascular diseases and risks depending on specific or large metabolic cycles (4) Physiological variations of previously identified genes and proteins (5) Environment influences on them. After summarizing the most well-known genes involved in drug metabolism, we will take as example of drugs, the statins, considered as very important drugs from a Public-Health standpoint, but also for economical reasons. These drugs respond differently in human depending on multiple polymorphisms. We will give examples with common ApoE polymorphisms influencing the hypolipemic effects of statins. These drugs also have pleiotropic effects and decrease inflammatory markers. This illustrates the need to separate clinical diseases phenotypes in specific metabolic pathways, which could propose other classifications, of diseases and related genes. Hypertension is also a good example of clinical phenotype which should be followed after various therapeutic approaches by genes polymorphisms and proteins markers. Gene products are under clear environmental expression variations such as age, body mass index and obesity, alcohol, tobacco and dietary interventions which are the first therapeutical actions taken in cardiovascular diseases. But at each of the five steps, within a pharmacoproteomic strategy, we also need to use available information from peptides, proteins and metabolites, which usually are the gene products. A profiling approach, i.e., dealing with genomics, but now also with proteomics, is to be used. In conclusion, the profiling, as well as the large amount of data, will more than before render necessary an organized interpretation of DNA, RNA as well as proteins variations, both at individual and population level.

Pharmacogenetics of response to statins: Where do we stand?

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

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

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

Mechanistic and epidemiologic considerations in the evaluation of adverse birth outcomes following gestational exposure to statins

The cholesterol-lowering "statin" drugs are contraindicated in pregnancy, but few data exist on their safety in human gestation. We reviewed case reports for patterns suggesting drug-related effects on prenatal development and considered a variety of mechanisms by which such effects, if confirmed, might occur. This uncontrolled case series included all FDA reports of statin exposures during gestation, as well as others from the literature and from manufacturers. Exposures and outcomes were reviewed and were tabulated by individual drug. Age-specific rates of exposure to each drug among women of child-bearing age were estimated. Of 214 ascertained pregnancy exposures, 70 evaluable reports remained after excluding uninformative cases. Among 31 adverse outcomes were 22 cases with structural defects, 4 cases of intrauterine growth restriction, and 5 cases of fetal demise. There were two principal categories of recurrent structural defects: cerivastatin and lovastatin were associated with four reports of severe midline CNS defects; simvastatin, lovastatin, and atorvastatin were all associated with reports of limb deficiencies, including two similar complex lower limb defects reported following simvastatin exposure. There were also two cases of VACTERL association among the limb deficiency cases. All adverse outcomes were reported following exposure to cerivastatin, simvastatin, lovastatin, or atorvastatin, which are lipophilic and equilibrate between maternal and embryonic compartments. None were reported following exposure to pravastatin, which is minimally present in the embryo. Statins reaching the embryo may down-regulate biosynthesis of cholesterol as well as many important metabolic intermediates, and may have secondary effects on sterol-dependent morphogens such as Sonic Hedgehog. The reported cases display patterns consistent with dysfunction of cholesterol biosynthesis and Sonic Hedgehog activity. Controlled studies are needed to investigate the teratogenicity of individual drugs in this class.

Effect of genetic polymorphism of OATP-C (SLCO1B1) on lipid-lowering response to HMG-CoA reductase inhibitors

The effect of genetic polymorphism of human organic anion transporting polypeptide C (OATP-C) on the lipid-lowering response to 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase inhibitors was assessed. A retrospective study was conducted on 66 patients who underwent treatment of hyperlipidemia with HMG-CoA reductase inhibitors in a municipal hospital in a community-based cohort of Ehime prefecture in the southern part of Japan. Plasma lipid concentrations before and after administration were analyzed in patients in relation to the 521T/C (Val-174-->Ala) polymorphism in the OATP-C gene (TT: n=44 (66.7%), TC: n=20 (30.3%), CC: n=0 (0.0%), undetermined: n=2 (3.0%)). Total cholesterol level was significantly lowered after treatment with HMG-CoA reductase inhibitors in all patients (p<0.001); moreover, subjects with the 521C allele showed an attenuated total-cholesterol-lowering effect compared with those homozygous for the 521T allele (-22.3+/-8.7% vs. -16.5+/-10.5%, p<0.05). These data suggest that the 521T/C polymorphism of the OATP-C gene modulates the lipid-lowering efficacy of HMG-CoA reductase inhibitors.

Cardiovascular pharmacogenomics

There is large interpatient variability in the response to drugs, including cardiovascular drugs. Thus, while some patients achieve the desired therapeutic response from their drug therapy, others do not. There is also a subset of patients who will experience adverse effects, which can range from bothersome to life threatening. Research in recent years has provided compelling evidence that in many cases, genetics contributes importantly to this variable drug response. Thus, pharmacogenomics is a field focused on unravelling the genetic determinants of variable drug response. Examples from the literature of genetic associations with drug efficacy and toxicity are described to provide insight into the field, including the roles of genetic variability in drug-metabolizing enzymes and drug targets. There is also a detailed discussion of the experimental approaches used in cardiovascular pharmacogenomics. Current research is largely focused on a limited candidate gene approach, which allows for description of significant genetic associations with variable response, but often does not explain the genetic basis of variable drug response enough to be useful clinically. As such, there is a move towards genome-wide approaches, and the various technologies available to obtain genomic data are discussed. Cardiovascular pharmacogenomics has the potential for leading to improvements in the use of cardiovascular drug therapy, through selection of the most appropriate drug therapy in an individual based on their genetic information. It will probably be a decade or more before genetic information is widely used in drug therapy decisions, but it seems clear that important findings in the area will continue to expand and the experimental approaches will continue to evolve.

In vitro biomarker discovery for atherosclerosis by proteomics

The purpose of this study was to identify in vitro and then prioritize a tractable set of protein biomarker candidates of atherosclerosis that may eventually be developed to measure the extent, progression, regression, and stability of atherosclerotic lesions. A study was conducted using an in vitro"foam cell" model based on the stimulation of differentiated THP1 cells with oxidized low-density lipoprotein (oxidized LDL) as compared with low-density lipoprotein (LDL). Analysis of the proteins contained in the cell supernatant using proteome scanning technology identified 59 proteins as being increased, 57 with no statistically measurable difference, and 17 decreasing in abundance following treatment with oxidized LDL, as compared with LDL. From the up-regulated list, proteins were prioritized based on their analytical confidence as well as their relevance to atherosclerosis pathways. Within the group of increased abundance, seven families of proteins were of particular interest: fatty acid-binding proteins, chitinase-like enzymes, cyclophilins, cathepsins, proteoglycans, urokinase-type plasminogen activator receptor, and a macrophage scavenger receptor.

Pharmacogenomics and drug response in cardiovascular disorders

There are a total of 17 families of drugs that are used for treating the heterogeneous group of cardiovascular diseases. We propose a comprehensive pharmacogenomic approach in the field of cardiovascular therapy that considers the five following sources of variability: the genetics of pharmacokinetics, the genetics of pharmacodynamics (drug targets), genetics linked to a defined pathology and its corresponding drug therapies, the genetics of physiologic regulation, and environmental–genetic interactions. Examples of the genetics of pharmacokinetics are presented for phase I (cytochromes P450) and phase II (conjugating enzymes) drug-metabolizing enzymes and for phase III drug transporters. The example used to explain the genetics of pharmacodynamics is glycoprotein IIIa and the response to antiplatelet effects of aspirin. Genetics linked to a defined pathology and its corresponding drug therapies is exemplified by ADRB1, ACE, CETP and APOE and drug response in metabolic syndrome. The examples of cytochrome P450s, APOE and ADRB2 in relation to ethnicity, age and gender are presented to describe genetics of physiologic regulation. Finally, environmental–genetic interactions are exemplified by CYP7A1 and the effects of diet on plasma lipid levels, and by APOE and the effects of smoking in cardiovascular disease. We illustrate this five-tiered approach using examples of cardiovascular drugs in relation to genetic polymorphism.

Genomic and non-genomic interactions of PPARalpha with xenobiotic-metabolizing enzymes

The hypolipidemic properties of fibrates, synthetic activators of the nuclear receptor, peroxisome proliferator-activated receptor alpha (PPARalpha), have been studied extensively. Recent observations indicate, however, that PPARalpha also functions as a regulator of endobiotic and xenobiotic metabolism in rodents and humans. Activators of PPARalpha affect xenobiotic-metabolizing enzymes (XMEs) at different levels. At the genomic level, the expression of numerous cytochrome P450 (CYP) and phase II conjugating genes is altered in a species-distinct manner on treatment with PPARalpha activators. As a result of such regulatory processes, PPARalpha affects the homeostasis of both its own natural ligands and other compounds including bile acids. At the non-genomic level, PPARalpha activators can act as competitive inhibitors for inactivating other molecules, leading to drug-drug interactions. These global effects of PPARalpha activators on the activity of XMEs are of physiological and pharmaceutical importance, and demonstrate that thorough studies of the actions on XMEs of each novel PPARalpha agonist are warranted.