Has pharmacogenetics brought us closer to 'personalized medicine' for initial drug treatment of hypertension?

A rare genetic variant of BPIFB4 predisposes to high blood pressure via impairment of nitric oxide signaling

BPIFB4 is associated with exceptional longevity: four single-nucleotide polymorphisms distinguish the wild-type form from a longevity-associated variant conferring positive effects on blood pressure. The effect of a rare variant (RV; allele frequency, 4%) on blood pressure is unknown. Here, we show that overexpression of RV-BPIFB4 in ex-vivo mouse vessels impairs phosphorylation of endothelial nitric oxide synthase (eNOS), blunting acetylcholine-evoked vasorelaxation; in vivo, virally mediated overexpression of RV-BPIFB4 increases blood pressure, an action absent in eNOS-deficient mice. In humans, we found RV carriers to have increased diastolic blood pressure, a finding that was more marked in subjects on anti-hypertensive medication; moreover, recombinant RV-BPIFB4 protein impaired eNOS function in ex-vivo human vessels. Thus, RV-BPIFB4 acts directly on blood pressure homeostasis and may represent a novel biomarker of vascular dysfunction and hypertension.

Gene-environment interactions of selected pharmacogenes in arterial hypertension

Hypertension affects approximately 1 billion people worldwide. Owing to population aging, hypertension-related cardiovascular burden is expected to rise in the near future. In addition to genetic variants influencing the blood pressure response to antihypertensive drugs, several genes encoding for drug-metabolizing or -transporting enzymes have been associated with blood pressure and/or hypertension in humans (e.g., ACE, CYP1A2, CYP3A5, ABCB1 and MTHFR) regardless of drug treatment. These genes are also involved in the metabolism and transport of endogenous substances and their effects may be modified by selected environmental factors, such as diet or lifestyle. However, little is currently known on the complex interplay between environmental factors, endogenous factors, genetic variants and drugs on blood pressure control. This review will discuss the respective role of population-based primary prevention and personalized medicine for arterial hypertension, taking a pharmacogenomics' perspective focusing on selected pharmacogenes.

The IDEAL study : towards personalized drug treatment of hypertension

OBJECTIVE

To identify markers (phenotypic, genetic, or environmental) of blood pressure (BP) response profiles to angiotensin converting enzyme inhibitors (ACEIs) and diuretics.

METHODS

IDEAL was a crossover (two active and two wash out phases), double-blind, placebo-controlled trial. Eligible patients were untreated hypertensive, aged 25 to 70. After two visits, patients were randomized to one of four sequences. The main outcome was BP differences between the active treatment and placebo.

RESULTS

One hundred and twenty-four patients were randomised: mean age 53, men 65%, family history of hypertension 60%. Average BP fall at each visit before randomisation was about 2% of the initial level reflecting both a regression to the mean and a placebo effect.

CONCLUSION

The results are expected to improve knowledge in drug's mechanisms of action and pathophysiology of hypertension, and to help in personalizing treatment. The estimation of BP responses to each drug in standardized conditions provided a benefit to each participant.

Gene panels to help identify subgroups at high and low risk of coronary heart disease among those randomized to antihypertensive treatment: the GenHAT study

OBJECTIVE

To identify panels of genetic variants that predict treatment-related coronary heart disease (CHD) outcomes in hypertensive patients on one of four different classes of initial antihypertensive treatment. The goal was to identify subgroups of individuals on the basis of their genetic profile who benefit most from a particular treatment.

METHODS

Candidate genetic variants (n=78) were genotyped in 39 114 participants from Genetics of Hypertension Associated Treatment study, ancillary to Antihypertensive and Lipid Lowering Treatment to Prevent Heart Attack Trial. Antihypertensive and Lipid Lowering Treatment to Prevent Heart Attack Trial randomized hypertensive participants (≥55 years) to one of four treatments (amlodipine, chlorthalidone, doxazosin, lisinopril). The primary outcome was fatal CHD or nonfatal myocardial infarction (mean follow-up=4.9 years). A pharmacogenetic panel was derived within each of the four treatment groups. Receiver-operating characteristic (ROC) curves estimated the discrimination rate between those with and without a CHD event, on the basis of the addition of the genetic panel risk score.

RESULTS

For each treatment group, we identified a panel of genetic variants that collectively improved the prediction of CHD to a small but statistically significant extent. Chlorthalidone (A): NOS3 rs3918226; SELE rs5361; ICAM1 rs1799969; AGT rs5051; GNAS rs7121; ROC comparison, P=0.004; Amlodipine (B): MMP1 rs1799750; Factor5 (F5) rs6025; NPPA rs5065; PDE4D rs6450512; MMP9 rs2274756; ROC comparison, P=0.006; Lisinopril (C): AGT rs5051; PON1 rs705379; MMP12 rs652438; F12 rs1801020; GP1BA rs6065; PDE4D rs27653; ROC comparison, P=0.01; Doxazosin (D): F2 rs1799963; PAI1 rs1799768; MMP7 rs11568818; AGT rs5051; ACE rs4343; MMP2 rs243865; ROC comparison, P=0.007. Each panel was tested for a pharmacogenetic effect; panels A, B, and D showed such evidence (P=0.009, 0.006, and 0.001, respectively) and panel C did not (P=0.09).

CONCLUSION

Because each panel was associated with CHD in a specific treatment group but not the others, this research provides evidence that it may be possible to use gene panel scores as a tool to better assess antihypertensive treatment choices to reduce CHD risk in hypertensive individuals.

Polymorphisms, hypertension and thiazide diuretics

It is 10 years since the discovery of the human genome; however, the study of the influence of genetic variants on drug effect - pharmacogenomics - has so far failed to create a major impact on day-to-day prescription practices. In the present article we analyze the main findings in candidate gene variants, gene combinations and whole-genome scans in relation to diuretic treatment. A critical analysis of the main reasons for some contrasting results will be discussed. The hypertension phases, in clinical trials dealing with genes and related pathophysiological mechanisms, may account for these inconsistent findings. The use of previously untreated versus treated patients is addressed. Finally, a positive study with a new genetic molecular strategy is described.

Adducin- and ouabain-related gene variants predict the antihypertensive activity of rostafuroxin, part 2: clinical studies

Twenty years of genetic studies have not contributed to improvement in the clinical management of primary arterial hypertension. Genetic heterogeneity, epistatic-environmental-biological interactions, and the pathophysiological complexity of hypertension have hampered the clinical application of genetic findings. In the companion article, we furnished data from rodents and human cells demonstrating two hypertension-triggering mechanisms--variants of adducin and elevated concentrations of endogenous ouabain (within a particular range)--and their selective inhibition by the drug rostafuroxin. Here, we have investigated the relationship between variants of genes encoding enzymes for ouabain synthesis [LSS (lanosterol synthase) and HSD3B1 (hydroxy-δ-5-steroid dehydrogenase, 3β- and steroid δ-isomerase 1)], ouabain transport {MDR1/ABCB1 [ATP-binding cassette, sub-family B (MDR/TAP), member 1]}, and adducin activity [ADD1 (adducin 1) and ADD3], and the responses to antihypertensive medications. We determined the presence of these variants in newly recruited, never-treated patients. The genetic profile defined by these variants predicted the antihypertensive effect of rostafuroxin (a mean placebo-corrected systolic blood pressure fall of 14 millimeters of mercury) but not that of losartan or hydrochlorothiazide. The magnitude of the rostafuroxin antihypertensive effect was twice that of antihypertensive drugs recently tested in phase 2 clinical trials. One-quarter of patients with primary hypertension display these variants of adducin or concentrations of endogenous ouabain and would be expected to respond to therapy with rostafuroxin. Because the mechanisms that are inhibited by rostafuroxin also underlie hypertension-related organ damage, this drug may also reduce the cardiovascular risk in these patients beyond that expected by the reduction in systolic blood pressure alone.

Gender-specific association between ACE gene I/D polymorphism and blood pressure response to hydrochlorothiazide in Han Chinese hypertensive patients

To evaluate the interaction between the angiotensin-converting enzyme (ACE) gene insertion/deletion (I/D) polymorphism and gender with individual blood pressure response to hydrochlorothiazide (HCTZ) in hypertensives, we enrolled 829 mild-moderate hypertensive patients. All subjects were given HCTZ (12.5 mg) orally each day for 6 weeks. A total of 776 patients completed the study. There was statistically significant interaction between the effects of genotype and gender on systolic (P = 0.002) and diastolic (P = 0.048) response after adjusting for covariables. Moreover, in each gender, the genotype that was associated with the greatest blood pressure response to HCTZ (DD homozygotes in men and II homozygotes in women) was also associated with the greatest increase in serum ACE activity in response to HCTZ. The results suggest that the I/D polymorphism of the ACE gene is associated with interindividual differences in the blood pressure response to a low dose of a diuretic in a gender-specific manner in the Han Chinese population with hypertension.

Pharmacogenetic interactions and their potential effects on genetic analyses of blood pressure

BACKGROUND

In observational studies, analyses of blood pressure (BP) typically require some correction for the use of antihypertensive medications by study participants. Different approaches to correcting for treatment have been compared, but the impact of pharmacogenetic interactions that influence the efficacy of antihypertensive treatments on estimates of genetic main effects has not been considered. This work demonstrates the potential influence of pharmacogenetic interactions in genetic analyses of BP.

METHODS

A simulation study is conducted to test the influence of pharmacogenetic interactions on approaches to the analysis of BP. Results from three plausible scenarios are presented.

RESULTS

Informative BP approaches (Fixed Treatment Effect, Non-parametric adjustment, Censored Normal Regression) perform well when there is no pharmacogenetic interaction, but yield biased estimates of the main effects of particular genetic variants when pharmacogenetic interactions exist. Substitution approaches (Binary Trait, Fixed Substitution, Random Substitution, Median Method) are unaffected by pharmacogenetic interactions, but consistently perform sub-optimally.

CONCLUSIONS

We recommend that the Informative BP approaches remain the most appropriate methods to use in practice, but stress that caution is required in the interpretation of their results-especially when an interaction between treatment and a genetic variant of interest is suspected. We make some suggestions as to how to check for possible interactions and confirm the results from genetic analyses of BP, but warn that these should be reviewed when data on real pharmacogenetic interactions become available.

Interaction of ACE and CYP11B2 genes on blood pressure response to hydrochlorothiazide in Han Chinese hypertensive patients

To valuate whether angiotensin converting enzyme (ACE) gene insertion/deletion (I/D) polymorphism and aldosterone synthase (CYP11B2) gene -344T/C polymorphism are associated with individual response to hydrochlorothiazide (HCTZ) in the Han Chinese population with essential hypertension. We enrolled 829 mild/moderate hypertensive patients and 12.5 mg of HCTZ was given daily. After 6 weeks, the results showed that the ACE I/D polymorphism, not the CYP11B2 -344T/C polymorphism, was associated with systolic blood pressure (SBP) response to HCTZ (P = 0.009) in the Han Chinese population with essential hypertension, with no interaction.

Safe and effective medicines for all: is personalized medicine the answer?

An improvement in drug treatment and clinical outcome is one of the major challenges in clinical medicine. The development of evidence-based standards of care has led to a significant improvement, but, by definition, strictly standardized cohorts in clinical trials have to ignore individual differences. Personalized medicine is defined as the application of genomic and molecular data to better target the delivery of healthcare, facilitate the discovery and clinical testing of new products, and help determine a person's predisposition to a particular disease or condition. After the deciphering of the human genome, however, the high expectations in individualized medicine were not always fulfilled. However, personalized medicine has become indispensable in the treatment of malignant diseases and there is increasing evidence for its benefit in other areas. This article outlines the impact of pharmacogenetics and pharmacogenomics, especially with regard to personalized medicine, in major medical indications and reflects the obstacles and chances taken in current daily practice.

Pharmacogenomics of antihypertensive drugs: past, present and future

Hypertension pharmacogenomics holds the promise of leading to individualized drug treatment approaches for the approximately 1 billion individuals worldwide with hypertension. Prior to 2000, the literature on hypertension pharmacogenomics was quite limited. The last decade has seen a substantial growth in the literature, with several examples of genes that appear to play an important role in antihypertensive response. The last decade has also made apparent the numerous challenges in hypertension pharmacogenomics, and addressing those challenges will be important. Moving forward, it seems clear that collaboration among researchers to allow replication or joint analyses will be essential in advancing the field, as will the use of genome-wide association approaches. The next decade should clearly define the clinical potential for hypertension pharmacogenomics.

The Pharmacogenomics of Anti-Hypertensive Therapy

Hypertension is a major public health problem, but measures to reduce blood pressure and thus cardiovascular risk are complicated by the high prevalence of treatment resistance, despite the availability of multiple drugs. Drug side-effects contribute considerably to suboptimal blood pressure control. Clinicians must often rely on empirical methods to match patients with effective drug treatment. Hypertension pharmacogenomics seeks to find genetic predictors of response to drugs that lower blood pressure and to translate this knowledge into clinical practice. In this review we summarise the current status of hypertension pharmacogenetics from monogenic hypertension to essential hypertension and discuss the issues that need to be considered in a hypertension pharmacogenomic study.