Pharmacogenomics of hypertension:

Chromogranin A polymorphisms are associated with hypertensive renal disease

Chromogranin A is released together with epinephrine and norepinephrine from catecholaminergic cells. Specific endopeptidases cleave chromogranin A into biologically active peptide fragments, including catestatin, which inhibits catecholamine release. Previous studies have suggested that a deficit in this sympathetic "braking" system might be an early event in the pathogenesis of human hypertension. Whether chromogranin A (CHGA) polymorphisms predict end-organ complications of hypertension, such as end-stage renal disease, is unknown. Among blacks, we studied common genetic variants spanning the CHGA locus in 2 independent case-control studies of hypertensive ESRD. Two haplotypes were significantly more frequent among subjects with hypertensive ESRD: 1) in the promoter (5') region, G-462A-->T-415C-->C-89A, haplotype ATC (adjusted odds ratio = 2.65; P = 0.037), and 2) at the 3'-end, C11825T (3'-UTR, C+87T)-->G12602C, haplotype TC (adjusted odds ratio = 2.73, P = 0.0196). Circulating levels of catestatin were lower among those with hypertensive ESRD than controls, an unexpected finding given that peptide levels are usually elevated in ESRD because of reduced renal elimination. We found that the 3'-UTR + 87T variant decreased reporter gene expression, providing a possible mechanistic explanation for diminished catestatin. In summary, common variants in chromogranin A associate with the risk of hypertensive ESRD in blacks.

Polymorphisms of ACE2 gene are associated with essential hypertension and antihypertensive effects of Captopril in women

ACE2 appears to counterbalance the vasopressor effect of angiotensin I converting enzyme (ACE) in the reninangiotensin system. We hypothesized that ACE2 polymorphisms could confer a high risk of hypertension and have an impact on the antihypertensive response to ACE inhibitors. The hypothesis was tested in two casecontrol studies and a clinical trial of 3,408 untreated hypertensive patients randomized to Atenolol, Hydrochlorothiazide, Captopril, or Nifedipine treatments for 4 weeks. ACE2 rs2106809 T allele was found to confer a 1.6-fold risk for hypertension in women (95% confidence interval (CI), 1.132.06), whereas when combined with the effect of the ACE DD genotype, the risk was 2.34-fold (95% CI, 1.754.85) in two independent samples. The adjusted diastolic blood pressure response to Captopril was 3.3 mm Hg lower in ACE2 T allele carriers than in CC genotype carriers (P=0.019) in women. We conclude that the ACE2 T allele confers a high risk for hypertension and reduced antihypertensive response to ACE inhibitors.

Renal albumin excretion: twin studies identify influences of heredity, environment, and adrenergic pathway polymorphism

Albumin excretion marks early glomerular injury in hypertension. This study investigated heritability of albumin excretion in twin pairs and its genetic determination by adrenergic pathway polymorphism. Genetic associations used single nucleotide polymorphisms at adrenergic pathway loci spanning catecholamine biosynthesis, storage, catabolism, receptor action, and postreceptor signal transduction. We studied 134 single nucleotide polymorphisms at 46 loci for a total of >51,000 genotypes. Albumin excretion heritability was 45.2+/-7.4% (P=2x10(-7)), and the phenotype aggregated significantly with adrenergic, renal, metabolic, and hemodynamic traits. In the adrenergic system, excretions of both norepinephrine and epinephrine correlated with albumin. In the kidney, albumin excretion correlated with glomerular and tubular traits (Na(+) and K(+) excretion; fractional excretion of Na(+) and Li(+)). Albumin excretion shared genetic determination (genetic covariance) with epinephrine excretion, and environmental determination with glomerular filtration rate and electrolyte intake/excretion. Albumin excretion associated with polymorphisms at multiple points in the adrenergic pathway: catecholamine biosynthesis (tyrosine hydroxylase), catabolism (monoamine oxidase A), storage/release (chromogranin A), receptor target (dopamine D1 receptor), and postreceptor signal transduction (sorting nexin 13 and rho kinase). Epistasis (gene-by-gene interaction) occurred between alleles at rho kinase, tyrosine hydroxylase, chromogranin A, and sorting nexin 13. Dopamine D1 receptor polymorphism showed pleiotropic effects on both albumin and dopamine excretion. These studies establish new roles for heredity and environment in albumin excretion. Urinary excretions of albumin and catecholamines are highly heritable, and their parallel suggests adrenergic mediation of early glomerular permeability alterations. Albumin excretion is influenced by multiple adrenergic pathway genes and is, thus, polygenic. Such functional links between adrenergic activity and glomerular injury suggest novel approaches to its prediction, prevention, diagnosis, and treatment.

Genetic information in the diagnosis and treatment of hypertension

Advancement in cardiovascular science should be measured by a number of new diagnostic and therapeutic options applied in clinical practice as a result of translational research. Hypertension genetics is a good example of such a successful transfer of knowledge from bench to bedside. There are genetic methods currently used as diagnostic tools in patients presenting with secondary forms of hypertension, including primary hyperaldosteronism, Cushing's syndrome, pheochromocytoma, and chronic kidney disease. Directed treatment that corrects pathophysiologic abnormalities is available for several monogenic forms of hypertension as a result of uncovering their underlying genetic mechanisms. Progress in hypertension pharmacogenetics and pharmacogenomics brings closer a perspective of personalized antihypertensive treatment and gene transfer strategies, which, although still considered as innovative approaches, may soon become options to treat, control, and, possibly, cure hypertension.

Functional variants of the angiotensinogen gene determine antihypertensive responses to angiotensin-converting enzyme inhibitors in subjects of African origin

OBJECTIVE

To determine whether the response to angiotensin-converting enzyme inhibitor (ACEI) monotherapy in subjects of African origin is determined by genetic variants within the angiotensinogen (AGT) gene.

METHODS

A total of 194 hypertensive patients of African ancestry were recruited from district clinics in Johannesburg, South Africa. Eighty patients received open-label ACEI (enalapril or lisinopril) monotherapy, and 114 open-label calcium antagonist (nifedipine) as a drug class comparator. Twenty-four hour ambulatory blood pressure (ABP) monitoring was performed at baseline (off medication) and after 2 months of therapy. DNA was analysed for functional variants (-217G-->A and -20A-->C) of the AGT gene. The impact of genotype on ABP responses to ACEI monotherapy or calcium antagonists; and on plasma aldosterone and renin levels after ACEI monotherapy was assessed.

RESULTS

Adjusting for baseline ABP and type of ACEI in the ACEI-treated group, the -217G-->A variant predicted ABP responses to ACEI (n = 77; P < 0.01), but not to nifedipine (n = 108). ACEI in patients with the AA genotype of the -217G-->A variant failed to elicit an antihypertensive response [change in ABP, mmHg: systolic blood pressure (SBP) +0.84 +/- 2.89, P = 0.78; diastolic blood pressure (DBP) -0.47 +/- 1.74, P = 0.79]. In contrast, those patients with at least one copy of the -217G allele developed a 7.23 +/- 1.55 and 5.38 +/- 1.12 mmHg decrease (P < 0.0001) in SBP and DBP, respectively, after ACEI administration. Similarly, the -20A-->C variant predicted ABP responses to ACEI monotherapy (P < 0.01) but not to nifedipine. Moreover, patients who were AA genotype for both variants failed to develop an antihypertensive response to ACEI (change in ABP, mmHg: SBP +1.06 +/- 3.05, P = 0.73; DBP -0.39 +/- 1.83, P = 0.83); whereas patients with at least one copy of both the -217G and the -20C allele developed substantial decreases in ABP (change in ABP, mmHg: SBP -14.08 +/- 3.72, P < 0.0001; DBP -9.62 +/- 2.74, P < 0.0001). Patients with at least one copy of the -217G allele demonstrated a significant reduction in the aldosterone-to-renin ratio (-0.098 +/- 0.035, P < 0.01), whereas in those patients who were -217AA genotype the ratio was unchanged (-0.03 +/- 0.16, P = 0.85).

CONCLUSION

Functional variants of the AGT gene contribute to the variability of antihypertensive responses to ACEI monotherapy in individuals of African ancestry, with genotype determining whether or not responses occur.

Proteomics for diabetes research: an update and future perspectives

Diabetes is a common disease worldwide and can cause several complications, leading to systemic derangements and end-organ damage. Despite blood sugar control and adequate therapy with currently available drugs, diabetic complications remain a serious issue in clinical practice, indicating that our knowledge of diabetes and its complications is only at the tip of the iceberg. Better understanding of its pathogenesis and pathophysiology is crucial to achieve better therapeutic outcomes and to prevent its complications. This review provides an overview of proteomics and introduces proteomic technologies commonly used for diabetes research. Recent proteomic studies for the investigation of diabetes and its complications are summarized. Finally, the future perspectives for the field of proteomics in diabetes research are discussed.

Antihypertensive therapy, the alpha-adducin polymorphism, and cardiovascular disease in high-risk hypertensive persons: the Genetics of Hypertension-Associated Treatment Study

In a double-blind, outcome trial conducted in hypertensive patients randomized to chlorthalidone (C), amlodipine (A), lisinopril (L), or doxazosin (D), the alpha-adducin Gly460Trp polymorphism was typed (n=36 913). Mean follow-up was 4.9 years. Relative risks (RRs) of chlorthalidone versus other treatments were compared between genotypes (Gly/Gly+Gly/Trp versus Trp/Trp). Primary outcome was coronary heart disease (CHD). Coronary heart disease incidence did not differ among treatments or genotypes nor was there any interaction between treatment and genotype (P=0.660). Subgroup analyses indicated that Trp allele carriers had greater CHD risk with C versus A+L in women (RR=1.31) but not men (RR=0.91) with no RR gender differences for non-carriers (gender-gene-treatment interaction, P=0.002). The alpha-adducin gene is not an important modifier of antihypertensive treatment on cardiovascular risk, but women Trp allele carriers may have increased CHD risk if treated with C versus A or L. This must be confirmed to have implications for hypertension treatment.

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.

Improving pharmacotherapy outcomes by pharmacogenomics: from expectation to reality?

The genomic era is now a reality and the extraction of genomic information with a practical value in healthcare represents the next challenge following the completion of the Human Genome Project. To this end, the first pharmacogenomics test approved by the US Food & Drug Administration for assessing cytochrome P450 (CYP)2D6 and CYP2C19 genotype in the implementation of pharmacotherapy decisions in patients, is expected to improve pharmaceutical care outcomes, at least for drugs that are substrates or inhibitors of these enzymes. Furthermore, the progress already achieved and the experience gained in the fields of pharmacogenomics and personalized medicine has clearly demonstrated that an interdisciplinary approach could better serve the target of improving pharmacotherapy outcomes in routine clinical practice. Such an approach will obviously move drug prescription towards pharmacotyping, a stage where the drug selection and dosage process carried out by medical practitioners for any given patient will be advanced by genomic knowledge and information.

Preventing end stage renal disease in diabetic patients--genetic aspect (part I)

Diabetic nephropathy is a major cause of diabetes- related morbidity and mortality; however the clinical course of the disease and the renal prognosis is highly variable among individuals. The current review will discuss the genetic influence on the development of end stage renal disease (ESRD) in diabetic patients and potential improvements to the current treatment strategy to slow the loss of kidney function in these patients. In this first part, the growing evidence that glucose-induced activation of the intra-renal and systemic renin-angiotensin systems plays an essential role in processes leading to destruction of renal function is summarised. Genetic variations, especially the angiotensin-converting enzyme (ACE)/ID polymorphisms in the gene coding for ACE, are involved in activation of the renin-angiotensin system and seem to influence the clinical course of diabetic nephropathy during treatment with ACE inhibitors. In addition, this polymorphism may interact with other polymorphisms within the renin-angiotensin system, leading to high risk of ESRD. As new genetic approaches and methods develop, further understanding of diabetic nephropathy will evolve and genotyping will help prevent ESRD in diabetic patients.

Pharmacogenetic association of the angiotensin-converting enzyme insertion/deletion polymorphism on blood pressure and cardiovascular risk in relation to antihypertensive treatment: the Genetics of Hypertension-Associated Treatment (GenHAT) study

BACKGROUND

Previous studies have reported that blood pressure response to antihypertensive medications is influenced by genetic variation in the renin-angiotensin-aldosterone system, but no clinical trails have tested whether the ACE insertion/deletion (I/D) polymorphism modifies the association between the type of medication and multiple cardiovascular and renal phenotypes.

METHODS AND RESULTS

We used a double-blind, active-controlled randomized trial of antihypertensive treatment that included hypertensives > or =55 years of age with > or =1 risk factor for cardiovascular disease. ACE I/D genotypes were determined in 37 939 participants randomized to chlorthalidone, amlodipine, lisinopril, or doxazosin treatments and followed up for 4 to 8 years. Primary outcomes included fatal coronary heart disease (CHD) and/or nonfatal myocardial infarction. Secondary outcomes included stroke, all-cause mortality, combined CHD, and combined cardiovascular disease. Fatal and nonfatal CHD occurred in 3096 individuals during follow-up. The hazard rates for fatal and nonfatal CHD and the secondary outcomes were similar across antihypertensive treatments. ACE I/D genotype group was not associated with fatal and nonfatal CHD (relative risk of DD versus ID and II, 0.99; 95% CI, 0.91 to 1.07) or any secondary outcome. The 6-year hazard rate for fatal and nonfatal CHD in the DD genotype group was not statistically different from the ID and II genotype group by type of treatment. No secondary outcome measure was statistically different across antihypertensive treatment and ACE I/D genotype strata.

CONCLUSIONS

ACE I/D genotype group was not a predictor of CHD, nor did it modify the response to antihypertensive treatment. We conclude that the ACE I/D polymorphism is not a useful marker to predict antihypertensive treatment response.

Genomics, proteomics and integrative "omics" in hypertension research

PURPOSE OF REVIEW

During the past few years, genomics, proteomics and other "omics" fields have been applied extensively to several areas of biomedical research. This review provides an overview and summarizes the current status of applications of these omics fields to essential and secondary hypertension. Some perspectives of these fields for future hypertension research are discussed.

RECENT FINDINGS

Genome-wide scans applying to essential hypertension have demonstrated numerous chromosomal regions with significant and/or suggestive evidence of linkage. The consistency of these results among several different studies is, however, problematic; probably because of the variability in number of families, ethnicity, family types, phenotyping strategy, study design and statistical analyses in those studies. Findings from such studies will be more valuable when more-complete sets of data and their integration are available. Proteomics is in its early phase in hypertension research, but has shown some significant data on the pathophysiology of hypoxia-induced and renovascular hypertension. Recently, integrative omics and systems biology have been emerging and seem to be the ideal approach for future hypertension research.

SUMMARY

Genomics, proteomics and integrative omics have demonstrated their potential in hypertension research to better understand the pathogenesis and pathophysiology of hypertension. In addition, they may contribute to identification of new therapeutic targets, biomarker discovery, prediction of therapeutic response, personalized treatment regimens, better therapeutic outcome and ultimately prevention of the disease.

Drug-gene interactions between genetic polymorphisms and antihypertensive therapy

Genetic factors may influence the response to antihypertensive medication. A number of studies have investigated genetic polymorphisms as determinants of cardiovascular response to antihypertensive drug therapy. In most candidate gene studies, no such drug-gene interactions were found. However, there is observational evidence that hypertensive patients with the 460 W allele of the alpha-adducin gene have a lower risk of myocardial infarction and stroke when treated with diuretics compared with other antihypertensive therapies. With regard to blood pressure response, interactions were found between genetic polymorphisms for endothelial nitric oxide synthase and diuretics, the alpha-adducin gene and diuretics, the alpha-subunit of G protein and beta-adrenoceptor antagonists, and the ACE gene and angiotensin II type 1 (AT(1)) receptor antagonists. Other studies found an interaction between ACE inhibitors and the ACE insertion/deletion (I/D) polymorphism, which resulted in differences in AT(1) receptor mRNA expression, left ventricular hypertrophy and arterial stiffness between different genetic variants. Also, drug-gene interactions between calcium channel antagonists and ACE I/D polymorphism regarding arterial stiffness have been reported. Unfortunately, the quality of these studies is quite variable. Given the methodological problems, the results from the candidate gene studies are still inconclusive and further research is necessary.

Pharmacogenetics of antihypertensive drug response

Pharmacogenetics is a discipline of molecular medicine that investigates the genetic basis of individual variation of drug responses. Before the era of the human genome project and the subsequent progress in genomic research, this field was primarily restricted to the investigation of the genetics of drug-metabolizing enzymes as they account for individual differences in pharmacokinetics and tolerability of drugs. In the current genomic era, pharmacogenetic research is applied to all fields of drug treatment in clinical medicine, including hypertension research. In contrast to the traditional approach, however, the influence of individual genetic variation on the efficacy of a drug (ie, the pharmacodynamic response) is the major focus of pharmacogenetic research and its clinical applicability. Therefore, the identification of individual genetic variation influencing the blood pressure-lowering effect of an antihypertensive compound and the implementation of this knowledge into clinical practice is the major goal of pharmacogenetic research in the field of hypertension. In this article, some important, recent research work and progress on the pharmacogenetics of antihypertensive drug responses are reviewed and evaluated.

Pharmacogenetics and cardiovascular disease management

Patients differ in their response to drugs. Part of this variability may reflect genetically-determined characteristics of target genes or metabolizing enzymes. A knowledge of an individual's genetic makeup could allow drug therapy to be targeted at those most likely to benefit.

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.

Single nucleotide polymorphisms in the apolipoprotein B and low density lipoprotein receptor genes affect response to antihypertensive treatment

BACKGROUND

Dyslipidemia has been associated with hypertension. The present study explored if polymorphisms in genes encoding proteins in lipid metabolism could be used as predictors for the individual response to antihypertensive treatment.

METHODS

Ten single nucleotide polymorphisms (SNP) in genes related to lipid metabolism were analysed by a microarray based minisequencing system in DNA samples from ninety-seven hypertensive subjects randomised to treatment with either 150 mg of the angiotensin II type 1 receptor blocker irbesartan or 50 mg of the beta1-adrenergic receptor blocker atenolol for twelve weeks.

RESULTS

The reduction in blood pressure was similar in both treatment groups. The SNP C711T in the apolipoprotein B gene was associated with the blood pressure response to irbesartan with an average reduction of 19 mmHg in the individuals carrying the C-allele, but not to atenolol. The C16730T polymorphism in the low density lipoprotein receptor gene predicted the change in systolic blood pressure in the atenolol group with an average reduction of 14 mmHg in the individuals carrying the C-allele.

CONCLUSIONS

Polymorphisms in genes encoding proteins in the lipid metabolism are associated with the response to antihypertensive treatment in a drug specific pattern. These results highlight the potential use of pharmacogenetics as a guide for individualised antihypertensive treatment, and also the role of lipids in blood pressure control.

From pharmacogenetics to personalized medicine: a vital need for educating health professionals and the community

The field of pharmacogenetics will soon celebrate its 50th anniversary. Although science has delivered an impressive amount of information in these 50 years, pharmacogenetics has suffered from lack of integration into clinical practice. There are several reasons for this, including the unmet need for education at medical schools and the lack of awareness about the impact of genetic medicine on healthcare in the community. Recently, the FDA announced that it considers pharmacogenomics one of three major opportunities on the critical path to new medical products. This notion by the FDA is filling the regulatory void that existed between drug developers and drug users. However, in order to bring pharmacogenetic testing to the prescription pad successfully, healthcare professionals and policy makers, as well as patients, need to have the necessary background knowledge for making educated treatment decisions. To effectively move pharmacogenetics into everyday medicine, it is therefore imperative for scientists and teachers in the field to take on the challenge of disseminating pharmacogenetic insights to a broader audience.

Pharmacogenomics of primary hypertension--the lessons from the past to look toward the future

A number of recent reviews have addressed the issue of the pharmacogenomics of primary hypertension and related complications by considering the data on the genotype-drug response relationship. Here we mainly discuss the methodological aspects of this issue, trying to integrate 'traditional' clinical and experimental pathophysiology and therapy-pharmacology with the 'new' genetics. Such integration is indispensable to: a). define the appropriate 'context' (genetic background, environment, age, gender, phase of hypertension, previous therapy etc.) in which a given genotype-drug response relationship should be tested (it is indeed likely that many discrepancies among published data originate from context's interference); b). assign the correct clinical meaning to the results obtained by statistics and functional genetics methodologies; c). define a novel clinical entity caused by a disease favoring allele, alone or in combination with other alleles, with a consistent clinical picture, prognosis and responsiveness to the appropriate drug; d). estimate the size of the population target amenable to benefit from a therapeutic intervention developed according to the pharmacogenomics' principles; e). develop a novel drug that selectively interferes with the sequence of events triggered by the genetic mechanism(s) underlying the clinical entity. Peculiar to this strategy is to look for consistency among findings gathered from different 'contexts' after having properly accounted for the context's dependency of the results.