APOA1 polymorphisms are associated with variations in serum triglyceride concentrations in hypercholesterolemic individuals

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.

Soluble P-selectin, procalcitonin, transforming growth factor (TGF)-β and apo-proteins in association with the components of metabolic syndrome in obese individuals

BACKGROUND & AIMS

Metabolic syndrome (MetS) is a clinical disorder with widespread prevalence. In the current study, we aimed to investigate the association between serum soluble P-selectin, procalcitonin, transforming growth factor (TGF)-β and apo-proteins with the components of metabolic syndrome in obese individuals.

MATERIAL AND METHODS

Sixty two obese patients with MetS and sixty five obese apparently healthy controls were participated in the current case-control study. The participants' anthropometric assessments and systolic and diastolic blood pressure (SBP and DBP) were measured. Serum lipids and the concentrations of ox-LDL, P-selectin, procalcitonin, TGF-β and apo-proteins were measured with commercial ELIZA kits.

RESULTS

Serum TG and TC were significantly higher in obese subjects with MetS; while TGF-β, procalcitonin, apoprotein B and insulin concentrations were higher in obese non- MetS group. In obese subjects with MetS, procalcitonin was in positive association with ox-LDL and apoprotein-B was in positive association with HDL. In obese subjects without MetS, apoprotein -B was in positive association with WC and HDL and WC.

CONCLUSION

The current study found several associations between serum lipids and PCT and serum apo-proteins in obese individuals either with or without MetS. Further studies with large sample size are warranted to better elucidate the observed relationships and underlying mechanism.

TRIAL REGISTRATION

Not Applicable.

Association of apolipoprotein A1 -75 G/A polymorphism with susceptibility to the development of acute lung injury after cardiopulmonary bypass surgery

Introduction

Apolipoprotein A1 (apoA1) is the major apoprotein constituent of high density lipoprotein (HDL) which exerts innate protective effects in systemic inflammation. However, its role in the acute lung injury (ALI) or acute respiratory distress syndrome (ARDS) has not been well studied. The objective of this study was to investigate the potential association between APOA1 -75 G/A polymorphism and the development of ALI after cardiopulmonary bypass (CPB) surgery.

Materials and methods

A hospital-based case–control study was conducted in patients with ALI (n = 300), patients without ALI (n = 300) and healthy controls (n = 300). Polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) assay was applied to assess the APOA1 -75 G/A genotypes.

Results

Patients with ALI had a significantly higher frequency of APOA1 -75 AA genotype [odds ratio (OR) =1.75, 95% confidence interval (CI) = 1.04, 2.92; P = 0.03] than patients without ALI. APOA1 -75 AA genotype (OR =3.47, 95% CI = 1.60, 7.52; P = 0.002) and A allele (OR =1.92, 95% CI = 1.24, 2.96; P = 0.003) were the significant independent prognostic factors for the 30-day survival rate of patients with ALI after CPB surgery.

Conclusion

Our study suggested that APOA1 -75 AA genotype was associated with a higher ALI risk after CPB surgery. Patients with the APOA1 -75 AA genotype and A allele had higher 30-day mortality of ALI after CPB surgery. Additional studies are needed to confirm this finding.

Pharmacogenomics of high-density lipoprotein-cholesterol-raising therapies

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

Statin regulation of CYP3A4 and CYP3A5 expression

CYP3A4 and CYP3A5 are cytochrome P450 enzymes that are highly expressed in the liver and gut and metabolize endogenous compounds and xenobiotics. Statins are cholesterol-lowering drugs that are extensively metabolized by CYP3A4 and CYP3A5. The bioavailability of statins is affected by CYP3A4 and CYP3A5 and glucuronidases metabolism as well as uptake and efflux transporters that affect drug disposition. CYP3A4 and CYP3A5 variants have been demonstrated to influence the pharmacokinetics, efficacy and safety of statins. Inducers and inhibitors of CYP3A4 and CYP3A5 play an important role in reducing statin efficacy and increase the risk of adverse effects, respectively. Statins have been demonstrated to increase CYP3A expression in vitro, most likely because they are ligands to nuclear receptors (pregnane X receptor and constitutive androsterone receptor) that form heterodimers with retinoid X receptors and bind to responsive elements in the CYP3A4 and CYP3A5 promoter regions. This special report outlines the earlier studies on variability of response to statins owing to CYP3A variants and highlights findings on the induction of CYP3A4 and CYP3A5 expression by statins.

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.

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.

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.