Determinants of variable response to simvastatin treatment: the role of common variants of SCAP, SREBF-1a and SREBF-2 genes

Evolutionary analysis of buffalo sterol regulatory element-binding factor (SREBF) family genes and their affection on milk traits

The sterol regulatory element-binding factor (SREBF) genes are a vital group of proteins binding to the sterol regulatory element 1 (SRE-1) regulating the synthesis of fatty acid. Two potential candidate genes (SREBF1 and SREBF2) have been identified as affecting milk traits. This study aims to identify the SREBF family of genes and find candidate markers or SREBF genes influencing lactation production in buffalo. A genome-wide study was performed and identified seven SREBF genes randomly distributed on 7 chromosomes and 24 protein isoforms in buffalos. The SREBF family of genes were also characterized in cattle, goat, sheep and horse, and using these all-protein sequences, a phylogenetic tree was built. The SREBF family genes were homologous between each other in the five livestock. Eight single nucleotide polymorphisms (SNPs) within or near the SREBF genes in the buffalo genome were identified and at least one milk production trait was associated with three of the SNP. The expression of SREBF genes at different lactation stages in buffalo and cattle from published data were compared and the SREBF genes retained a high expression throughout lactation with the trend being the same for buffalo and cattle. These results provide valuable information for clarifying the evolutionary relationship of the SREBF family genes and determining the role of SREBF genes in the regulation of milk production in buffalo.

Pharmacogenomics of statins: lipid response and other outcomes in Brazilian cohorts

Statins are inhibitors of 3-hydroxy-3-methylglutaryl-CoA reductase, a key enzyme in cholesterol biosynthesis, that are highly effective in reducing plasma low-density lipoprotein (LDL) cholesterol and decreasing the risk of cardiovascular events. In recent years, a multitude of variants in genes involved in pharmacokinetics (PK) and pharmacodynamics (PD) have been suggested to influence the cholesterol-lowering response. However, the vast majority of studies have analyzed the pharmacogenetic associations in populations in Europe and the USA, whereas data in other populations, including Brazil, are mostly lacking. This narrative review provides an update of clinical studies on statin pharmacogenomics in Brazilian cohorts exploring lipid-lowering response, adverse events and pleiotropic effects. We find that variants in drug transporter genes (SLCO1B1 and ABCB1) positively impacted atorvastatin and simvastatin response, whereas variants in genes of drug metabolizing enzymes (CYP3A5) decreased response. Furthermore, multiple associations of variants in PD genes (HMGCR, LDLR and APOB) with statin response were identified. Few studies have explored statin-related adverse events, and only ABCB1 but not SLCO1B1 variants were robustly associated with increased risk in Brazil. Statin-related pleiotropic effects were shown to be influenced by variants in PD (LDLR, NR1H2) and antioxidant enzyme (NOS3, SOD2, MTHFR, SELENOP) genes. The findings of these studies indicate that statin pharmacogenomic associations are distinctly different in Brazil compared to other populations. This review also discusses the clinical implications of pharmacogenetic studies and the rising importance of investigating rare variants to explore their association with statin response.

Effect of genetic polymorphisms in SREBF-SCAP pathway on therapeutic response to rosuvastatin in Saudi metabolic syndrome patients

AIM

Genetic variants contribute to statins' therapeutic variability. SREBF-SCAP pathway is a key player in lipid homeostasis. Hence, effect of SREBF-SCAP polymorphisms on therapeutic response was studied.

PATIENTS & METHODS

Metabolic syndrome patients of either sex were prescribed rosuvastatin 10 mg for 24 weeks. Clinical, anthropometric and lipid measurements were done before and after treatment. Genotyping was done by pyrosequencing.

RESULTS & CONCLUSION

No associations of SCAP and SREBF-1a genotypes with baseline lipids but significant associations with lipid reductions were observed. Significant effect of SCAP (GG; B = -8.16, p = 0.001); SREBF-1a (GG; B = -7.47, p = 0.001) and SREBF-1a (-delG; B = -7.42, p = 0.001) was observed on total cholesterol reduction. Additive trend was found between SCAP genotypes and lipid reductions. A total of 88% responders have SCAP 'G' allele (p = 0.001). Patients carrying SCAP (GG) and SREBF-1a (GG and -delG) have 9.5-, 8.6- and 14.6-times more likelihood of being responders (p < 0.05). 'G' allele in SCAP and SREBF-1a is significant predictor of rosuvastatin response.

Genetic variations in sterol regulatory element binding protein cleavage-activating protein (SCAP) are associated with blood pressure in overweight/obese Chinese children

OBJECTIVE

Previous studies demonstrated a role of variations in sterol regulatory element binding protein (SREBP) cleavage-activating protein (SCAP) in obesity and blood lipids. But the associations between SCAP polymorphisms and blood pressure (BP) are not clear. This study aimed to investigate the relationship between genetic variations in SCAP and BP phenotypes in a Chinese pediatric population.

METHODS

A case-control study on 702 high blood pressure (HBP) children and 1319 controls was conducted to explore the correlation between single nucleotide polymorphism markers (rs12487736 and rs12490383) of SCAP and BP phenotypes. The associations with continuous and categorical variables were examined by linear regression and logistic regression models under a dominant genetic model for the minor rs12487736 A allele and rs12490383 T allele.

RESULTS

The rs12487736 polymorphism was significantly associated with systolic BP (SBP) (β = 1.66, P = 0.003) and diastolic BP (DBP) (β = 1.35, P = 0.024) with age, age-squared, sex, study population and body mass index (BMI) adjusted under the dominant genetic model. The rs12490383 polymorphism was significantly associated with SBP (β = 1.71, P = 0.004) and SHBP (OR = 1.39, 95%CI: 1.04-1.86, P = 0.027). When analyzed by BMI categories, in the normal-weight children, no significant association between the SCAP polymorphisms and BP phenotypes was observed (all P > 0.05). However, in the overweight/obese children, rs12487736 was significantly associated with SBP (β = 1.6, P = 0.019) and SHBP (OR = 1.36, 95%CI: 1.02-1.82; P = 0.037), rs12490383 was associated with SBP (β = 2.04, P = 0.004) and SHBP (OR = 1.50, 95%CI: 1.10-2.05; P = 0.01).

CONCLUSIONS

This study demonstrated that SCAP rs12487736 and rs12490383 were significantly associated with SBP and SHBP in overweight/obese Chinese children. It provided the evidence for association of SCAP with SBP.

Effect of an SNP in SCAP gene on lipid-lowering response to rosuvastatin in Indian patients with metabolic syndrome

AIM

Statins treat dyslipidemia associated with metabolic syndrome. Genetic factors contribute to variable response. Sterol regulatory element-binding factors cleavage-activating protein (SCAP) pathway regulates lipid homeostasis, so effect of SNP in SCAP gene on rosuvastatin response was studied.

MATERIALS & METHODS

Metabolic syndrome patients with low-density lipoprotein-cholesterol ≥130 mg/dl, were prescribed rosuvastatin 5 mg for 3 months. Lipids were measured initially and finally, and genotyping done.

RESULTS & CONCLUSION

Sixty-three patients completed the study. Twenty-three were homozygous for AA while 40 were heterozygous. Significant association was found between post-treatment lipid values and SCAP genotypes but not with baseline values. Cholesterol (p = 0.002) and low-density lipoprotein-cholesterol (p = 0.008) were significantly reduced in patients carrying G allele as compared with AA. There was a significant effect of G allele on cholesterol reduction (p = 0.043). Out of total responders (achieving >23.58% total cholesterol reduction), 80.5% were 2386G carriers (GG+GA) and only 19.5% were homozygous for A allele (p = 0.0048). SCAP 2386A>G gene polymorphism is a significant predictor of hypolipidemic response.

Single-nucleotide polymorphisms: a perspective of cardiovascular prevention

INTRODUCTION

several studies have evaluated the utilization of lipid biomarkers in an attempt to correlate them with clinical cardiovascular events. Nevertheless, the investigation of clinical conditions under specific plasmatic levels of lipoproteins for long periods presents limitations due to inherent difficulties that are related to the follow-up of individuals throughout their lives. Better understanding of the clinical response and occasional resistance to the action of hypolipidemic drugs in several clinic scenarios is also necessary.

OBJECTIVES

to determine the role of evaluation of single-nucleotide polymorphisms (SNPs) related to the metabolism of lipids, and its implications in different clinical scenarios.

METHODS

a search of the literature in English and Spanish languages was performed in Medline, Lilacs via Bireme, IBECS via Bireme, and Cochrane databases. The expected results included information regarding plasmatic lipid profile and SNPs, cardiovascular clinical outcomes and polymorphisms related to the effectiveness of statins in the treatment of hypercholesterolemia.

RESULTS

in order to perform this analysis, 19 studies were included from a total of 89 identified citations. The evaluation of the results suggests that low plasmatic levels of LDL-c are associated with a reduction in the risk of heart attacks, although this was not observed for the rise of plasmatic levels of HDL-c.

CONCLUSION

polymorphisms in different populations and clinical perspectives may bring important contributions for a better understanding and adequacy of plasmatic lipoproteins aiming at reducing cardiovascular risk.

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.

ESR1 polymorphisms and statin therapy: a sex-specific approach

Lipid-lowering therapy has shown a high degree of variability in clinical response and there is evidence that the variability in drug response between individuals is due to genetic factors. Thirteen single nucleotide polymorphisms (SNPs) within the ESR1 gene were evaluated with basal lipid and lipoprotein levels, as well as response to lipid-lowering therapy, in 495 hypercholesterolemic individuals of European descent receiving simvastatin or atorvastatin. Significant associations were detected between rs4870061 (P=0.040, corrected P-value (PC)=0.440), rs1801132 (P=0.002, PC=0.022) and the SNP rs3020314 (P=0.013, PC=0.143) with triglyceride (TG) baseline levels. The rs4870061 was also associated with high-density lipoprotein cholesterol (HDL-C) baseline levels (P=0.045, PC=0.495). Regarding statin efficacy, rs2234693 C/C was associated with greater HDL-C increase (P=0.037; PC=0.407) and rs3798577 T allele was associated with greater total cholesterol (TC) reduction (P=0.019; PC=0.209) and greater TG reduction (P=0.026; PC=0.286). These associations suggest that ESR1 polymorphisms are in part responsible for the TC, HDL-C and TG variation levels and this effect may be sex-specific.

APOE polymorphisms contribute to reduced atorvastatin response in Chilean Amerindian subjects

Genetic factors can determine the high variability observed in response to lipid-lowering therapy with statins. Nonetheless, the frequency of single nucleotide polymorphisms (SNPs) and their impact can vary due to ethnicity. Because the Chilean population carries a strong Amerindian background, the objective of this study was to evaluate the influence of apolipoprotein E (APOE) variants (rs429358, rs7412) and the 1959C>T SNP (rs5925) in the low-density lipoprotein receptor (LDLR) in response to atorvastatin treatment in hypercholesterolemic individuals. A hundred and thirty nine subjects undergoing statin therapy were included. Identification of Amerindian mtDNA haplogroups was determined by polymerase chain reaction (PCR) and PCR followed by restriction fragment length polymorphism (RFLP), respectively. SNPs were determined by PCR-RFLP. Out of the 139 individuals studied, 84.4% had an Amerindian background, according to mtDNA analysis. In relation to APOE variants, carriers of the E3/4 genotype presented lower cholesterol reduction compared to genotype E3/3 (LDL-C: -18% vs. -29%, p ˂ 0.001). On the other hand, the LDLR rs5925 SNP was not related to atorvastatin response (p = 0.5760). Our results suggest that APOE SNPs are potential predictors to atorvastatin therapy in Amerindian Chilean subjects.

Evaluation of sexual dimorphism in the efficacy and safety of simvastatin/atorvastatin therapy in a southern Brazilian cohort

BACKGROUND

Dyslipidemia is the primary risk factor for cardiovascular disease, and statins have been effective in controlling lipid levels. Sex differences in the pharmacokinetics and pharmacodynamics of statins contribute to interindividual variations in drug efficacy and toxicity.

OBJECTIVE

To evaluate the presence of sexual dimorphism in the efficacy and safety of simvastatin/atorvastatin treatment.

METHODS

Lipid levels of 495 patients (331 women and 164 men) were measured at baseline and after 6 ± 3 months of simvastatin/atorvastatin treatment to assess the efficacy and safety profiles of both drugs.

RESULTS

Women had higher baseline levels of total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C) compared with men (p < 0.0001). After treatment, women exhibited a greater decrease in plasma TC and LDL-C levels compared with men. After adjustment for covariates, baseline levels of TC and LDL-C influenced more than 30% of the efficacy of lipid-lowering therapy (p < 0.001), regardless of sex. Myalgia [with or without changes in creatine phosphokinase (CPK) levels] occurred more frequently in women (25.9%; p = 0.002), whereas an increase in CPK and/or abnormal liver function was more frequent in in men (17.9%; p = 0.017).

CONCLUSIONS

Our results show that baseline TC and LDL-C levels are the main predictors of simvastatin/atorvastatin therapy efficacy, regardless of sex. In addition, they suggest the presence of sexual dimorphism in the safety of simvastatin/atorvastatin. The effect of sex differences on receptors, transporter proteins, and gene expression pathways needs to be better evaluated and characterized to confirm these observations.

Pharmacogenomics of sterol synthesis and statin use in schizophrenia subjects treated with antipsychotics

OBJECTIVE

Patients with schizophrenia treated with antipsychotics often develop metabolic side effects including dyslipidemia. Antipsychotics potentially upregulate gene expression of a lipid metabolism pathway protein called SREBP via SREB transcription factors (SREBFs). Genetic variation within SREBF may contribute to dyslipidemias and lipid medication efficacy within schizophrenia.

RESULTS

A cross-sectional study of 157 patients were genotyped for SREBF1 (rs11868035) and SREBF2 (rs1057217) variants, and assessed for fasting lipids. The cohort's mean age was 46.6 years, was 64% male and 86% were using atypical antipsychotics. When stratified by statin use, those receiving a statin and carrying the SREBF1 T allele exhibited higher total cholesterol levels (p = 0.01), triglyceride levels (p = 0.04) and low-density lipoprotein levels (p = 0.03). A regression analysis controlling for gender differences in lipids showed that the SREBF1 T allele and statin interaction remained only for total cholesterol levels (F[4,149] = 5.8; p < 0.0001).

CONCLUSION

For schizophrenia individuals with the SREBF1 rs11868035 T allele, incomplete response to statin medications may be seen. Future investigations may allow for personalizing dyslipidemia treatment based on pharmacogenetics within schizophrenia.

The gene-gene interaction of INSIG-SCAP-SREBP pathway on the risk of obesity in Chinese children

Background. Childhood obesity has become a global public health problem in recent years. This study aimed to explore the association of genetic variants in INSIG-SCAP-SREBP pathway with obesity in Chinese children. Methods. A case-control study was conducted, including 705 obese cases and 1,325 nonobese controls. We genotyped 15 single nucleotide polymorphisms (SNPs) of five genes in INSIG-SCAP-SREBP pathway, including insulin induced gene 1 (INSIG1), insulin induced gene 2 (INSIG2), SREBP cleavage-activating protein gene (SCAP), sterol regulatory element binding protein gene 1 (SREBP1), and sterol regulatory element binding protein gene 2 (SREBP2). We used generalized multifactor dimensionality reduction (GMDR) and logistic regression to investigate gene-gene interactions. Results. Single polymorphism analyses showed that SCAP rs12487736 and rs12490383 were nominally associated with obesity. We identified a 3-locus interaction on obesity in GMDR analyses (P = 0.001), involving 3 genetic variants of INSIG2, SCAP, and SREBP2. The individuals in high-risk group of the 3-locus combinations had a 79.9% increased risk of obesity compared with those in low-risk group (OR = 1.799, 95% CI: 1.475–2.193, P = 6.61 × 10⁻⁹). Conclusion. We identified interaction of three genes in INSIG-SCAP-SREBP pathway on risk of obesity, revealing that these genes affect obesity more likely through a complex interaction pattern than single gene effect.

Genetic markers associated to dyslipidemia in HIV-infected individuals on HAART

This study evaluated the impact of 9 single nucleotide polymorphisms (SNPs) in 6 candidate genes (APOB, APOA5, APOE, APOC3, SCAP, and LDLR) over dyslipidemia in HIV-infected patients on stable antiretroviral therapy (ART) with undetectable viral loads. Blood samples were collected from 614 patients at reference services in the cities of Porto Alegre, Pelotas, and Rio Grande in Brazil. The SNPs were genotyped by conventional polymerase chain reaction (PCR) and real-time PCR. The prevalence of dyslipidemia was particularly high among the protease inhibitors-treated patients (79%). APOE (rs429358 and rs7412) genotypes and APOA5 −1131T>C (rs662799) were associated with plasma triglycerides (TG) and low-density-lipoprotein cholesterol levels (LDL-C). The APOA5 −1131T>C (rs662799) and SCAP 2386A>G (rs12487736) polymorphisms were significantly associated with high-density-lipoprotein cholesterol levels. The mean values of the total cholesterol and LDL-C levels were associated with both the APOB SP Ins/Del (rs17240441) and APOB XbaI (rs693) polymorphisms. In conclusion, our data support the importance of genetic factors in the determination of lipid levels in HIV-infected individuals. Due to the relatively high number of carriers of these risk variants, studies to verify treatment implications of genotyping before HAART initiation may be advisable to guide the selection of an appropriate antiretroviral therapy regimen.

An anti-PCSK9 antibody reduces LDL-cholesterol on top of a statin and suppresses hepatocyte SREBP-regulated genes

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a promising therapeutic target for treating coronary heart disease. We report a novel antibody 1B20 that binds to PCSK9 with sub-nanomolar affinity and antagonizes PCSK9 function in-vitro. In CETP/LDLR-hemi mice two successive doses of 1B20, administered 14 days apart at 3 or 10 mpk, induced dose dependent reductions in LDL-cholesterol (≥ 25% for 7-14 days) that correlated well with the extent of PCSK9 occupancy by the antibody. In addition, 1B20 induces increases in total plasma antibody-bound PCSK9 levels and decreases in liver mRNA levels of SREBP-regulated genes PCSK9 and LDLR, with a time course that parallels decreases in plasma LDL-cholesterol (LDL-C). Consistent with this observation in mice, in statin-responsive human primary hepatocytes, 1B20 lowers PCSK9 and LDLR mRNA levels and raises serum steady-state levels of antibody-bound PCSK9. In addition, mRNA levels of several SREBP regulated genes involved in cholesterol and fatty-acid synthesis including ACSS2, FDPS, IDI1, MVD, HMGCR, and CYP51A1 were decreased significantly with antibody treatment of primary human hepatocytes. In rhesus monkeys, subcutaneous (SC) dosing of 1B20 dose-dependently induces robust LDL-C lowering (maximal ~70%), which is correlated with increases in target engagement and total antibody-bound PCSK9 levels. Importantly, a combination of 1B20 and Simvastatin in dyslipidemic rhesus monkeys reduced LDL-C more than either agent alone, consistent with a mechanism of action that predicts additive effects of anti-PCSK9 agents with statins. Our results suggest that antibodies targeting PCSK9 could provide patients powerful LDL lowering efficacy on top of statins, and lower cardiovascular risk.

Common sequence variants in pharmacodynamic and pharmacokinetic pathway-related genes conferring LDL cholesterol response to statins

AIMS

This study assessed the association between pharmacokinetic- and pharmacodynamic-related genes and individual responses to low-density lipoprotein cholesterol (LDL-C) change by statins in a Chinese population.

MATERIALS & METHODS

A total of 386 patients with primary hypercholesterolemia were treated with statins for 9 months. The 62 haplotype-tagging SNPs of ten candidate genes were genotyped. Treating LDL-C reduction as an outcome variable, we performed multiple linear regression models in various modes of inheritance to test the effects of SNP and haplotype variants.

RESULTS

After correction for the multiple tests, only rs12916 in HMGCR and rs9902941 in SREBF1 remained significant. For rs12916 in the HMGCR gene, individuals with CC genotype showed a reduction of 56.9 mg/dl for LDL-C, with the reduction increasing to 60.1 and 62.5 mg/dl among individuals carrying CT and TT, respectively (p-value for additive model = 0.006). For the HMGCR gene, subjects carrying the CCGTCCA haplotype had a significant increase of LDL-C (adjusted mean -7.2 +/- 2.3 mg/dl; p-value for global test = 0.002). For the ABCG8 gene, subjects carrying the ATTATCGAC haplotype had a significant reduction of LDL-C (adjusted mean -13.0 +/- 4.6 mg/dl; p-value for global test = 0.005).

CONCLUSION

Our results indicated a strong association of sequence variants of HMGCR, SREBF1 and ABCG8 genes with the reduction of LDL-C after statin treatment in a Chinese population. Future studies on the genes of drug-metabolism enzymes and transporters are warranted.

Expression of sterol regulatory element-binding transcription factor (SREBF) 2 and SREBF cleavage-activating protein (SCAP) in human atheroma and the association of their allelic variants with sudden cardiac death

Background

Disturbed cellular cholesterol homeostasis may lead to accumulation of cholesterol in human atheroma plaques. Cellular cholesterol homeostasis is controlled by the sterol regulatory element-binding transcription factor 2 (SREBF-2) and the SREBF cleavage-activating protein (SCAP). We investigated whole genome expression in a series of human atherosclerotic samples from different vascular territories and studied whether the non-synonymous coding variants in the interacting domains of two genes, SREBF-2 1784G>C (rs2228314) and SCAP 2386A>G, are related to the progression of coronary atherosclerosis and the risk of pre-hospital sudden cardiac death (SCD).

Methods

Whole genome expression profiling was completed in twenty vascular samples from carotid, aortic and femoral atherosclerotic plaques and six control samples from internal mammary arteries. Three hundred sudden pre-hospital deaths of middle-aged (33–69 years) Caucasian Finnish men were subjected to detailed autopsy in the Helsinki Sudden Death Study. Coronary narrowing and areas of coronary wall covered with fatty streaks or fibrotic, calcified or complicated lesions were measured and related to the SREBF-2 and SCAP genotypes.

Results

Whole genome expression profiling showed a significant (p = 0.02) down-regulation of SREBF-2 in atherosclerotic carotid plaques (types IV-V), but not in the aorta or femoral arteries (p = NS for both), as compared with the histologically confirmed non-atherosclerotic tissues. In logistic regression analysis, a significant interaction between the SREBF-2 1784G>C and the SCAP 2386A>G genotype was observed on the risk of SCD (p = 0.046). Men with the SREBF-2 C allele and the SCAP G allele had a significantly increased risk of SCD (OR 2.68, 95% CI 1.07–6.71), compared to SCAP AA homologous subjects carrying the SREBF-2 C allele. Furthermore, similar trends for having complicated lesions and for the occurrence of thrombosis were found, although the results were not statistically significant.

Conclusion

The results suggest that the allelic variants (SREBF-2 1784G>C and SCAP 2386A>G) in the cholesterol homeostasis regulating SREBF-SCAP pathway may contribute to SCD in early middle-aged men.

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.

Atorvastatin effects on SREBF1a and SCAP gene expression in mononuclear cells and its relation with lowering-lipids response

BACKGROUND

The transcription factors SREBP1 and SCAP are involved in intracellular cholesterol homeostasis. Polymorphisms of these genes have been associated with variations on serum lipid levels and response to statins that are potent cholesterol-lowering drugs. We evaluated the effects of atorvastatin on SREBF1a and SCAP mRNA expression in peripheral blood mononuclear cells (PBMC) and a possible association with gene polymorphisms and lowering-cholesterol response.

METHODS

Fifty-nine hypercholesterolemic patients were treated with atorvastatin (10 mg/day for 4 weeks). Serum lipid profile and mRNA expression in PBMC were assessed before and after the treatment. Gene expression was quantified by real-time PCR using GAPD as endogenous reference and mRNA expression in HepG2 cells as calibrator. SREBF1 -36delG and SCAP A2386G polymorphisms were detected by PCR-RFLP.

RESULTS

Our results showed that transcription of SREBF1a and SCAP was coordinately regulated by atorvastatin (r=0.595, p<0.001), and that reduction in SCAP transcription was associated with the 2386AA genotype (p=0.019). Individuals who responded to atorvastatin with a downregulation of SCAP had also a lower triglyceride compared to those who responded to atorvastatin with an upregulation of SCAP.

CONCLUSION

Atorvastatin has differential effects on SREBF1a and SCAP mRNA expression in PBMC that are associated with baseline transcription levels, triglycerides response to atorvastatin and SCAP A2386G polymorphism.

Effect of pretreatment with statins on ischemic stroke outcomes

BACKGROUND AND PURPOSE

Statins reduce the risk of stroke in at-risk populations and may improve outcomes in patients taking statins before an ischemic stroke (IS). Our objectives were to examine the effects of pretreatment with statins on poor outcome in IS patients.

METHODS

Over a 6-month period all acute IS admissions were prospectively identified in 15 hospitals participating in a statewide acute stroke registry. Poor stroke outcome was defined as modified Rankin score >/=4 at discharge (ie, moderate-severe disability or death). Multivariable logistic regression models and matched propensity score analyses were used to quantify the effect of statin pretreatment on poor outcome.

RESULTS

Of 1360 IS patients, 23% were using statins before their stroke event and 42% had a poor stroke outcome. After multivariable adjustment, pretreatment with statins was associated with lower odds of poor outcome (OR=0.74, 95% CI 0.52, 1.02). A significant interaction (P<0.01) was found between statin use and race. In whites, statins were associated with statistically significantly lower odds of poor outcome (OR=0.61, 95% CI 0.42, 0.86), but in blacks statins were associated with a nonstatistically significant increase in poor outcome (OR=1.82, 95% CI 0.98, 3.39). Matched propensity score analyses were consistent with the multivariable model results.

CONCLUSIONS

Pretreatment with statins was associated with better stroke outcomes in whites, but we found no evidence of a beneficial effect of statins in blacks. These findings indicate the need for further studies, including randomized trials, to examine differential effects of statins on ischemic stroke outcomes among whites and blacks.

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.

SREBP-2 and SCAP isoforms and risk of early onset myocardial infarction

BACKGROUND

Cholesterol metabolism is mediated, in part, by the sterol-regulatory element binding proteins (SREBPs) that are activated by a SREBP cleavage-activating protein (SCAP). We examined whether coding variations in the interacting domains of both genes, are related to early-onset MI risk in a population-based case-control study from western Washington State.

METHODS

Cases were 257 women, aged 18-59 years, and 320 men, aged 18-49 years, with first acute non-fatal MI; controls were 353 women and 311 men, similar in age, identified from the community who had no history of clinical CHD or stroke. Genotyping of the SREBF-2 G1784C polymorphism (SREBP-2-595A/G isoforms), and the SCAP A2386G polymorphism (SCAP-796I/V isoforms), were performed.

RESULTS

After adjustment for age and race, the SREBP-2-595A isoform was associated with increased MI risk among men (OR=1.63, 95% CI=1.26-2.12). In contrast, there was little evidence for an association among women in a multiplicative model. However, compared to SREBP-2-595G homozygotes, homozygote women for the SREBP-2-595A isoform were at nearly two-fold increased risk (OR=1.95, 95% CI=1.07-3.54). Overall, SCAP genotypes were neither associated with MI in men nor in women. However, in men, SCAP genotypes were found to modify the association between SREBF-2 and MI (p-value for interaction=0.01).

CONCLUSION

The SREBP-2-595A isoform was associated with an increased risk of early-onset MI in U.S. men. The SCAP polymorphism appeared to modify the associations of SREBF-2 genotype with MI risk among men. These novel findings require confirmation in other populations.

The relationship of sterol regulatory element-binding protein cleavage-activation protein and apolipoprotein E gene polymorphisms with metabolic changes during weight reduction

Sterol regulatory element-binding protein cleavage-activating protein (SCAP) and apolipoprotein E (apo E) regulate cellular and plasma lipid metabolism. Therefore, variations in the corresponding genes might influence weight reduction and obesity-associated metabolic changes. We investigated the relationships of SCAP (Ile796Val) and apo E polymorphisms on metabolic changes during weight reduction by using a 12-week very low-energy diet. Body composition, serum lipids, plasma glucose, and insulin were assessed in 78 healthy premenopausal women (initial body mass index, 34 +/- 4 kg/m(2); age, 40 +/- 4 years) before and after the intervention. The SCAP genotype groups did not differ in the responses of any parameters measured during weight reduction. Apo E did not differentiate the weight loss, but the changes in total and low-density lipoprotein cholesterol for the genotype groups apo E epsilon2/3, epsilon3/3, as well as epsilon3/4 and epsilon4/4 combined were -0.94 +/- 0.56 and -0.59 +/- 0.32, -0.71 +/- 0.49 and -0.49 +/- 0.45, and -0.55 +/- 0.47 and -0.37 +/- 0.39 mmol/L, respectively (P < .05 for both). In conclusion, neither the SCAP Ile796Val nor the apo E polymorphism was associated with weight loss in obese premenopausal women. However, the apo E-but not SCAP genotype-seems to be one of the modifying factors for serum cholesterol concentrations during very low-energy diet in obese premenopausal women.

Pharmacogenetics and pharmacogenomics of cholesterol-lowering therapy

PURPOSE OF REVIEW

To summarize recent findings on pharmacokinetics, pharmacodynamics, drug-drug interactions and influence of lifestyle heterogeneity on adverse events in cholesterol-lowering therapy

RECENT FINDINGS

The prevention of cardiovascular disease is critically dependent on lipid-lowery therapy, including statins, cholesterol absorption inhibitors, fibrates and nicotinic acid. Statins are the most prescribed drugs in lipid lowering therapy with variability in response and almost one third of the patients do not meet their treatment goals. The severe adverse effects of treatment with cerivastatin stimulated the search for new genes and gene variations affecting pharmacokinetics, drug-drug interactions and pharmacodynamics. Moreover, instead of monotherapy, combined therapy of statins with ezetemibe and niacin was considered. This led to the identification of CD13, NPC1L1 and HM74A as new targets and CYP2C8 and glucuronidation enzymes as potential targets for drug-drug interactions. Moreover multiple polymorphic sites and pleiotrophic gene targets were reinvestigated in larger cohorts and the relevant pathogenetic factors start to evolve.

SUMMARY

Statin therapy is widely used and well tolerated by the majority of patients. To further reduce potential adverse effects and to increase efficacy, combined therapy concepts with ezetimibe or niacin are underway.