Renin–angiotensin system gene polymorphisms: relationship with blood pressure and microalbuminuria in telmisartan-treated hypertensive patients

Impact of Renin-Angiotensin-Aldosterone System (RAAS) Gene Polymorphism in Essential Hypertension and Antihypertensive Drug Therapy: A Review

Genetic, demographic and environmental factors all play a role in the frequency of an intricate multifactorial condition known as hypertension. Approximately 30% and 50% of BP fluctuation are influenced by genetic variability. Many genetic studies have confirmed the link between genetic variability and susceptibility to essential hypertension; hence, identifying genes associated with essential hypertension susceptibility will aid in understanding the pathophysiology and their influence on how an individual responds towards the antihypertensive therapy. There are also controversial results highlighted in some reports. This review summarises genetic variants of the renin-angiotensin-aldosterone system (RAAS), angiotensinogen (AGT) (M235T), angiotensin converting enzyme (ACE) (insertion/deletion), angiotensin II type 1 receptor (AT1R) (A1166C) and aldosterone synthase (C344T) that are known and might contribute towards the pathophysiology of essential hypertension. Furthermore, the review highlights the response of certain RAAS gene polymorphisms (renin, ACE and AT1R genes) to antihypertensive drugs.

Genetic polymorphisms influencing antihypertensive drug responses

Hypertension is a major contributor to cardiovascular disease and its associated morbidity and mortality. The low efficacy observed with some anti-hypertensive therapies has been attributed partly to inter-individual genetic variability. This paper reviews the major findings regarding these genetic variabilities that modulate responses to anti-hypertensive therapies such as angiotensin converting enzyme (ACE) inhibitors, angiotensin receptor blockers (ARBs), diuretics, calcium channel blockers (CCBs) and β-adrenoceptor blockers. The importance of studying these genetic polymorphisms stems from the goal to optimise anti-hypertensive therapy for each individual patient, aiming for the highest efficacy and lowest risk of adverse effects. It is important to recognise that environmental and epigenetic factors can contribute to the observed variations in drug responses. Owing to the multigenic and multifactorial nature of drug responses, further research is crucial for translating these findings into clinical practice and the establishment of reliable recommendations.

Clinical Pharmacogenetics of Angiotensin II Receptor Blockers in Iraq

Background

Clinical pharmacogenetics is a rapidly growing field that focuses on the study of genetic variations and their impact on drug metabolism, efficacy, and safety. Angiotensin II receptor blockers (ARBs) are commonly used to treat hypertension in Iraq but not all patients respond equally to these drugs.

Aim

This article aims to review the current evidence on the clinical pharmacogenetics of ARBs in Iraq and its implications for personalized medicine.

Materials and Methods

We conducted a literature review of studies on the genetic variations that affect the response to ARBs in Iraq. We also reviewed the prevalence of these genetic variants in the Iraqi population and discussed the potential clinical implications for personalized medicine.

Results

The most studied genetic variations associated with ARB response in Iraq are the angiotensin-converting enzyme gene insertion/deletion polymorphism and the angiotensin II type 1 receptor gene A1166C polymorphism. The angiotensin-converting enzyme gene insertion/deletion polymorphism is associated with variability in response to ARBs, while the angiotensin II type 1 receptor A1166C polymorphism is associated with an increased risk of cardiovascular events in patients treated with ARBs. The prevalence of these genetic variants in the Iraqi population varies widely depending on the region and ethnic group.

Conclusion

The clinical pharmacogenetics of ARBs in Iraq suggests that pharmacogenetic testing could improve the selection and dosing of ARBs in Iraqi patients, leading to better patient outcomes and cost-effective healthcare.

Antihypertensive and Target-Organ Protective Properties of Telmisartan and Hydrochlorothiazide Single-Pill Combination

The most important result of the revision of the European and Russian guidelines for the management of arterial hypertension (AH) was a special focus on initializing antihypertensive treatment with single-pill combinations (SPCs) in majority patients with AH. Combination of the angiotensin II receptor blocker and thiazide diuretic is one of the possible first line SPCs in the absence of specific clinical conditions according to the new guidelines. In this regard, SPC of telmisartan and hydrochlorothiazide (HCT), worth special noticing in the classes of sartans and thiazide diuretics, since both drugs have a long clinical experience and large body of evidence of antihypertensive efficacy and safety, as well as telmisartan also has a number of superior target-organ protective and metabolic properties distinguishing it from other members of the class. In real clinical practice TANDEM study telmisartan and its SPC with HCT showed high antihypertensive efficacy and good tolerability in patients with all AH grades and with isolated systolic AH and allowed to achieve target blood pressure levels in the most of patients. Long-lasting effect is another essential characteristic of telmisartan, this feature allows to control blood pressure throughout the day, including the morning surge, which is the most “dangerous” in terms of cardiovascular risk. Telmisartan also provide powerful target-organ protection realized at the level of all AH target-organs. Finally, another unique pharmacological property of telmisartan and its combination with HCT is a favourable effect on the carbohydrate and lipid profile, which comprises of increasing tissue sensitivity to insulin, normalizing blood glucose levels, reducing blood total cholesterol, low-density lipoprotein cholesterol and triglycerides and thereby reducing risk of atherosclerosis development and progression. Telmisartan/HCT SPC should be recommended for wide use in hypertensive patients to control blood pressure, protect end-organs, improve prognosis and reduce cardiovascular risk due to its high antihypertensive efficacy, the ability to provide the large target-organ protection and a beneficial metabolic effect.

Association between angiotensin II type-1 receptor A1166C polymorphism and the presence of angiographically-defined coronary artery disease in an Iranian population

Background: There are reported associations between a polymorphism of the angiotensin II type 1 receptor (AT1R/A1166C) gene and coronary artery disease (CAD), hypertension, and myocardial infarction in some populations. Objective: Investigate the association between A1166C polymorphism and CAD in an Iranian population. Methods: Four hundred and thirteen patients with suspected CAD were recruited. Based on coronary angiography, the patients were classified into CAD+ (n=315) and CAD- (n=98) groups defined as >50% and <50% stenosis of any major coronary artery, respectively. One hundred and thirty-five healthy subjects were also recruited as the control group. The AT1R polymorphism was assessed using a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) based method. Results: A higher frequency of the AC and CC genotypes and lower frequency of the AA genotype was observed in both CAD+ and CAD- groups, compared with the control group (p <0.05). CAD+ and CAD- groups also had a higher frequency of the C allele than controls (p <0.01). There was no significant difference in genotype and allele frequencies between hypertensive and non-hypertensive patients (p > 0.05). In addition, the AT1R genotype frequencies did not differ significantly among different subgroups of CAD+ patients, based on the number of affected coronary vessels (p >0.05). Conclusion: The frequency AT1R/A1166C polymorphism was higher among patients with some degrees of coronary stenosis who are candidates of coronary angiography.

RAS Genetic Variants in Interaction with ACE Inhibitors Drugs Influences Essential Hypertension Control

BACKGROUNDS AND AIMS

Essential Hypertension (EH) is a common disorder associated with increased cardiovascular morbidity and mortality in Malaysia. To investigate how genetic polymorphisms of the renin-angiotensin-aldosterone system (RAS) influence EH control with angiotensin-converting enzyme inhibitor drugs (ACEI).

METHODS

A case-control, cross-sectional population-based nested study (n = 142) included hypertensive subjects treated with ACEI drugs, either lisinopril or enalapril (20 mg, once daily) as monotherapy for 24 weeks. In total seven possible polymorphisms of RAS genes were genotyped. The association between those polymorphisms and the changes in blood pressure were observed in the 24 week treatment.

RESULTS

Statistically significant associations of I, G, T, M and G alleles of ACE (I/D, G2350A), AGT (M235T, T175M and G-6A) respectively were observed in essential hypertensive subjects. The decrease in systolic blood pressure and diastolic blood pressure after 24 weeks of treatment of the patients carrying II, GG, and TT genotypes were greater than the groups carrying DD, AA, MM, MM and GG of I/D, G2350A, M235T, T174M and G-6A genotypes respectively. In contrast, No significant difference was observed between renin gene polymorphisms (Bg/I and MboI) and hypertensives.

CONCLUSIONS

Although this study shows a possible association of polymorphisms of RAS genes with the risk of non-control of HT in ACEI-treated patients and indicates the importance of all this system's components in regulating HT, it needs to be replicated in other data sources.

Pharmacogenomics of heart failure: a systematic review

BACKGROUND

Heart failure (HF) and multiple HF-related phenotypes are heritable. Genes implicated in the HF pathophysiology would be expected to influence the response to treatment.

METHODS

We conducted a series of systematic literature searches on the pharmacogenetics of HF therapy to assess the current knowledge on this field.

RESULTS

Existing data related to HF pharmacogenomics are still limited. The ADRB1 gene is a likely candidate to predict response to β-blockers. Moreover, the cytochrome P450 2D6 coding gene (CYP2D6) clearly affects the pharmacokinetics of metoprolol, although the clinical impact of this association remains to be established.

CONCLUSION

Given the rising prevalence of HF and related costs, a more personalized use of HF drugs could have a remarkable benefit for patients, caregivers and healthcare systems.

Review: Potential protective effects of telmisartan on renal function deterioration

Experimental and clinical evidence is now available that antagonism of angiotensin II (Ang II) with both angiotensin-converting enzyme inhibitors and Ang II receptor antagonists (AIIAs) is effective in slowing the rate of renal functional loss in patients affected by proteinuric kidney diseases.Among AIIAs, telmisartan has been shown to be characterised by a potent and long lasting antihypertensive effect that may be associated with another specific effect of this molecule, the partial agonism of the peroxisome-activated receptor-gamma.Although this action has also been observed with other AIIAs, telmisartan seems to exert a more effective and specific action as in such a way to influence beneficially adipocyte metabolism, diabetes onset and insulin resistance. Recently, we have demonstrated, at the experimental and clinical level, that sustained blockade of Ang II biological activity with this class of compounds can potentially reduce the progression of renal dysfunction and in some circumstances induce the regression of renal functional and structural changes. In this review we analyse available experimental and clinical data that suggest that blocking Ang II with telmisartan may effectively ameliorate renal dysfunction in patients affected by the now frequently observed condition termed metabolic syndrome.

A Physiologic Approach to the Pharmacogenomics of Hypertension

Hypertension is a multifactorial condition with diverse physiological systems contributing to its pathogenesis. Individuals exhibit significant variation in their response to antihypertensive agents. Traditional markers, such as age, gender, diet, plasma renin level, and ethnicity, aid in drug selection. However, this review explores the contribution of genetics to facilitate antihypertensive agent selection and predict treatment efficacy. The findings, reproducibility, and limitations of published studies are examined, with emphasis placed on candidate genetic variants affecting drug metabolism, the renin-angiotensin system, adrenergic signalling, and renal sodium reabsorption. Single-nucleotide polymorphisms identified and replicated in unbiased genome-wide association studies of hypertension treatment are reviewed to illustrate the evolving understanding of the disease's complex and polygenic pathophysiology. Implementation efforts at academic centers seek to overcome barriers to the broad adoption of pharmacogenomics in the treatment of hypertension. The level of evidence required to support the implementation of pharmacogenomics in clinical practice is considered.

Role of single nucleotide polymorphisms in pharmacogenomics and their association with human diseases

Global statistical data shed light on an alarming trend that every year thousands of people die due to adverse drug reactions as each individual responds in a different way to the same drug. Pharmacogenomics has come up as a promising field in drug development and clinical medication in the past few decades. It has emerged as a ray of hope in preventing patients from developing potentially fatal complications due to adverse drug reactions. Pharmacogenomics also minimizes the exposure to drugs that are less/non-effective and sometimes even found toxic for patients. It is well reported that drugs elicit different responses in different individuals due to variations in the nucleotide sequences of genes encoding for biologically important molecules (drug-metabolizing enzymes, drug targets and drug transporters). Single nucleotide polymorphisms (SNPs), the most common type of polymorphism found in the human genome is believed to be the main reason behind 90% of all types of genetic variations among the individuals. Therefore, pharmacogenomics may be helpful in answering the question as to how inherited differences in a single gene have a profound effect on the mobilization and biological action of a drug. In the present review, we have discussed clinically relevant examples of SNP in associated diseases that can be utilized as markers for "better management of complex diseases" and attempted to correlate the drug response with genetic variations. Attention is also given towards the therapeutic consequences of inherited differences at the chromosomal level and how associated drug disposition and/or drug targets differ in various diseases as well as among the individuals.

Do genetic variants of the Renin-Angiotensin system predict blood pressure response to Renin-Angiotensin system-blocking drugs?: a systematic review of pharmacogenomics in the Renin-Angiotensin system

The concept of “pharmacogenomics” or “pharmacogenetics” promises to offer the ultimate in personalized medicine, and the renin-angiotensin system (RAS) is one of the most plausible candidates for the application of this approach in the area of hypertension. For the past two decades, genetic variants of the RAS have been tested for association with blood pressure response, but the results have been inconsistent. The problems have been attributed to many issues, but the most fundamental concern is thought to be the statistical power of the studies. Therefore, we have tried to put together a new systematic review using a database search including only recent reports with adequate numbers of subjects, and 11 reports were identified. From the results, we were able to draw conclusions with nearly consistent findings that the conventional genetic variants of the system (i.e., the ACE I/D, AGT M235T, AT1 A1166C, and AT2 variant) are not associated with antihypertensive effects by RAS blockade, at least by one individual SNP. By contrast, significant associations have been reported (by one report each) for AGT rs7079, AT1 haplotype, REN, and ACE2. For these variants, further evaluations and confirmation are anticipated.

AT1 Receptor Gene Polymorphisms in relation to Postprandial Lipemia

Background. Recent data suggest that the renin-angiotensin system may be involved in triglyceride (TG) metabolism. We explored the effect of the common A1166C and C573T polymorphisms of the angiotensin II type 1 receptor (AT1R) gene on postprandial lipemia.Methods. Eighty-two subjects measured daytime capillary TG, and postprandial lipemia was estimated as incremental area under the TG curve. The C573T and A1166C polymorphisms of the AT1R gene were determined.Results. Postprandial lipemia was significantly higher in homozygous carriers of the 1166-C allele (9.39±8.36 mM*h/L) compared to homozygous carriers of the 1166-A allele (2.02±6.20 mM*h/L) (P<0.05). Postprandial lipemia was similar for the different C573T polymorphisms.Conclusion. The 1166-C allele of the AT1R gene seems to be associated with increased postprandial lipemia. These data confirm the earlier described relationships between the renin-angiotensin axis and triglyceride metabolism.

Association between angiotensin II type 1 receptor gene polymorphism and metabolic syndrome in a young female Iranian population

BACKGROUND AND AIMS

The overall prevalence of obesity and metabolic syndrome (MetS) is increasing among children and adolescents and can predispose to type II diabetes mellitus and cardiovascular disease. There are reported associations between an angiotensin II type I receptor gene polymorphism (AT(1)R/A1166C) with hypertension, myocardial infarction, insulin resistance and cardiovascular disease risk. In the present study, we aimed to investigate whether the AT(1)R/A1166C polymorphism was associated with MetS among adolescent Iranian girls.

METHODS

A total of 350 adolescent girls aged 15-17 years from high schools and different educational zones of Mashhad city participated in this population-based, genetic association study. Of these individuals, 101 patients had MetS (defined by the NCEP-ATP III criteria); the remaining 249 age-matched girls were considered as the control group. All subjects were genotyped for the AT(1)R/A1166C polymorphism using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique.

RESULTS

Frequencies of the AA, AC and CC genotypes were 164 (65.9%), 80 (32.1%) and 5 (2.0%) in the control group and 79 (78.2%), 20 (19.8%) and 2 (2.0%) in patients, which were not consistent with the Hardy-Weinberg equilibrium (p <0.05 and p <0.001, respectively). Frequency of the AT(1)R C allele was found to be significantly lower in patients compared with controls (p <0.05).

CONCLUSIONS

Our findings suggested that the 1166C allele of AT(1)R gene may be associated with a decreased risk of MetS in adolescent Iranian females.

Genetic polymorphisms related to the renin-angiotensin-aldosterone system and response to antihypertensive drugs

IMPORTANCE OF THE FIELD

Only 23 - 41% of hypertensive patients receiving antihypertensive drugs achieve adequate blood pressure control. Multiple physiological systems regulate blood pressure and variation in genes involved in these systems may account for enhanced or diminished blood pressure lowering response to antihypertensive therapy.

AREAS COVERED IN THIS REVIEW

We explored explanations for variation in blood pressure response to antihypertensive drugs by linking genetic polymorphisms in renin-angiotensin-aldosterone system (RAAS) genes to antihypertensive drug response on intermediate parameters (e.g., potassium excretion, aldosterone levels). A MEDLINE search (1966 - 2008) was performed to identify publications reporting effects of genetic polymorphisms in the RAAS on antihypertensive drug response with regard to intermediate parameters.

WHAT THE READER WILL GAIN

With regard to the ACE insertion/deletion and the angiotensinogen -217G/A polymorphism variation in blood pressure response could be explained by effects on intermediate parameters. However, most studies that were identified with our search varied in study design, population and outcome, which complicate adequate comparisons.

TAKE HOME MESSAGE

Little evidence is available that explains these pharmacogenetic interactions. In the future, a better understanding of these mechanisms should provide a more solid evidence base for the individualized hypertension treatment based on genetic variation.

New standards in hypertension and cardiovascular risk management: focus on telmisartan

Blockade of the renin–angiotensin system is an important approach in managing high blood pressure, and has increasingly been shown to affect cardiovascular disease processes mediated by angiotensin II throughout the cardiovascular and renal continua. Telmisartan is an angiotensin II receptor blocker (ARB) displaying unique pharmacologic properties, including a longer half life than any other ARB, that result in large and sustained reductions of blood pressure. In patients with mild-to-moderate hypertension, telmisartan has proved superior to other antihypertensive agents (valsartan, losartan, ramipril, perindopril, and atenolol) in controlling blood pressure particularly towards the end of the dosing interval. There is also clinical evidence that telmisartan reduces left ventricular hypertrophy, reduces arterial stiffness and the recurrence of atrial fibrillation, and confers renoprotection. The ONgoing Telmisartan Alone and in combination with Ramipril Global Endpoint Trial (ONTARGET^®) study has demonstrated that telmisartan has similar cardiovascular protective effects to ramipril in a large, high-risk patient population but was better tolerated. The powerful and sustained blood pressure control apparent in clinical trials, together with cardiovascular protection and tolerability demonstrated in ONTARGET^® means that telmisartan may be a preferred option for patients with hypertension.

Genetic variant of the Renin-Angiotensin system and diabetes influences blood pressure response to Angiotensin receptor blockers

OBJECTIVE Recent studies have proven the favorable effects of angiotensin receptor blockers (ARBs) on cardiovascular and renal disorders. However, determinants of the response to ARBs remain unclear. We substantiated the hypothesis that genetic variants of the renin-angiotensin system (RAS) have significant impacts on the response to ARBs. RESEARCH DESIGN AND METHODS Subjects comprised 231 consecutively enrolled hypertensive individuals including 45 type 2 diabetic subjects. Five genetic variants of the RAS, i.e., renin (REN) C-5312T, ACE insertion/deletion, angiotensinogen M235T, angiotensin II type 1 receptor A1166C, and angiotensin II type 2 receptor C3123A were assayed by PCR and restriction fragment-length polymorphism. A dose of 40-160 mg/day of valsartan was administered for 3 months as a monotherapy. RESULTS Changes in diastolic blood pressure significantly differed between genotypes of REN C-5312T: 10.7-mmHg reduction (from 95.9 +/- 12.9 to 85.2 +/- 11.4) in CC versus 7.0-mmHg reduction (from 94.7 +/- 14.0 to 87.7 +/- 12.6) in CT/TT (P = 0.02 for interactive effects of valsartan and genotype). Responder rates also differed between the genotypes: 72.8% in CC versus 58.0% in CT/TT (P = 0.03). Univariate analysis indicated a significant association of response to valsartan with blood pressure, diabetes, plasma aldosterone concentration, and CC homozygotes of REN C-5312T. Finally, multiple logistic regression analysis revealed that systolic blood pressure, CC homozygotes of REN C-5312T, and diabetes were independent predictors for responders with odds ratios (95% CI) of 2.49 (1.41-4.42), 2.03 (1.10-3.74), and 0.48 (0.24-0.96), respectively. CONCLUSIONS This study provides strong support that a genetic variant of REN C-5312T and diabetes contribute to the effects of ARBs and are independent predictors for responder. Thus, in treatment of hypertension with ARBs, a new possibility for personalized medicine has been shown.

Significance of genetic polymorphisms of the renin–angiotensin–aldosterone system in cardiovascular and renal disease

The angiotensin converting enzyme (ACE) is a component of the renin–angiotensin–aldosterone system (RAAS). The RAAS – involved primarily in blood pressure and sodium homeostasis – is activated in many renal and cardiovascular diseases, and therapy with ACE inhibitors and other blockers of the RAAS has proven to be clinically beneficial. Plasma and tissue levels of ACE are at least partially determined by a genetic polymorphism based on the presence (insertion [I]) or absence (deletion [D]) of a 287 base pair element in intron 16. In particular Asian subjects with the DD genotype (and increased ACE activity) have been reported to be at higher risk for cardiovascular disorders and nephropathy. Numerous studies evaluated the role of the ACE I/D polymorphism as well as other genetic variants of the RAAS in the context of RAAS inhibitor therapy. However, as race and environmental factors, such as salt intake also affect treatment response most studies were underpowered leading to conflicting results.

Renin-angiotensin system and alpha-adducin gene polymorphisms and their relation to responses to antihypertensive drugs: results from the GENRES study

BACKGROUND

Polymorphisms in genes coding for components of the renin-angiotensin system (RAS) and alpha-adducin (ADD1) have been reported to be associated with blood pressure (BP) responses to antihypertensive agents. The results, however, have not been consistent and most of the earlier studies have been small and lacked placebo-control. Therefore, the association of common polymorphisms in these genes with BP responses to four different antihypertensive drugs was analyzed in a controlled study.

METHODS

The study included 208 hypertensive Finnish men from the GENRES study. All of them used amlodipine 5 mg, bisoprolol 5 mg, hydrochlorothiazide (HCT) 25 mg, and losartan 50 mg daily, each for 4 weeks as a monotherapy in a double-blind, randomized, study. The treatment periods were separated by 4-week placebo periods. Both 24-h ambulatory (ABP) and office BP (OBP) measurements were carried out. The polymorphisms analyzed were ADD1 Gly460Trp, angiotensinogen (AGT) Met235Thr, angiotensin converting enzyme (ACE) insertion/deletion (I/D), and angiotensin II type 1 receptor (AGTR1) 1166A/C.

RESULTS

The presence of 460Trp allele of ADD1, previously suggested to be a marker of thiazide responsiveness, did not predict a better response to HCT. There was no significant association of AGT Met235Thr, ACE I/D, and AGTR1 1166A/C polymorphisms with BP responses to the study drugs. ADD1 460Trp and AGT 235Thr alleles were associated with higher systolic white coat effect (WCE) during the placebo periods (P values 0.03 and 0.01, respectively).

CONCLUSIONS

Common polymorphisms of ADD1, AGT, ACE, and AGTR1 do not markedly predict BP responses to amlodipine, bisoprolol, HCT, and losartan, at least in white hypertensive men.

Effects of AGTR1 A1166C gene polymorphism in patients with heart failure treated with candesartan

BACKGROUND

The benefits of angiotensin II receptor blockers (ARBs) in patients with heart failure who are treated with standard pharmacotherapy, including an angiotensin-converting enzyme (ACE) inhibitor, were demonstrated in 2 large randomized trials. It is currently impossible to determine which patient will benefit from the addition of an ARB.

OBJECTIVE

To explore the impact of selected candidate genes on the hemodynamic, neurohormonal, and antiinflammatory effects of candesartan in patients with heart failure who are already being treated with an ACE inhibitor.

METHODS

We investigated the impact of 10 candidate genetic polymorphisms on the effects of candesartan in patients with heart failure who are treated with an ACE inhibitor. We evaluated their impact on acute (2 wk) and long-term (24 wk) changes in blood pressure and N-terminal proB-type natriuretic peptide (NT-proBNP) and high sensitivity C-reactive protein (hsCRP) during treatment with candesartan.

RESULTS

Thirty-one patients were included. Homozygotes of the AGTR1 A1166 allele (n = 13) had a greater decrease in systolic (-9.1 +/- 4.7 vs 1.1 +/- 3.3 mm Hg; p = 0.04 by analysis of variance [ANOVA], adjusting for dose) and diastolic blood pressure (-5.1 +/- 1.5 vs 1.9 +/- 1.9 mm Hg; p = 0.005 by ANOVA, adjusting for dose) compared with C1166 allele carriers (n = 18) following 2 weeks of treatment. After 6 months of treatment, C1166 carriers experienced a greater decrease in NT-proBNP (-151.4 [-207; -19.8] ng/L vs 147.3 [-61.3; 882.9] ng/L; p = 0.03) and hsCRP (-0.8 [-2.2; -0.03] mg/L) vs 0.2 [-1.8; 5.3] mg/L; p = 0.09) compared with patients carrying the AA1166 genotype. No other significant association was found.

CONCLUSIONS

The results of this proof-of concept study provide the first evidence that the AGTR1 A1166C polymorphism could influence the response to candesartan in patients with heart failure who are receiving ACE inhibitors. Validation of these exploratory findings in larger populations is required before use of the AGTR1 A1166C genotype can be incorporated into clinical practice.

Angiotensin converting enzyme insertion/deletion polymorphism and renoprotection in diabetic and nondiabetic nephropathies

Despite the huge amount of studies looking for candidate genes, the ACE gene remains the unique, well-characterized locus clearly associated with pathogenesis and progression of chronic kidney disease, and with response to treatment with drugs that directly interfere with the renin angiotensin system (RAS), such as angiotensin converting enzyme (ACE) inhibitors and angiotensin II receptor antagonists (ARA). The II genotype is protective against development and progression of type I and type II nephropathy and is associated with a slower progression of nondiabetic proteinuric kidney disease. ACE inhibitors are particularly effective at the stage of normoalbuminuria or microalbuminuria in both type I and type II diabetics with the II genotype, whereas the DD genotype is associated with a better response to ARA therapy in overt nephropathy of type II diabetes and to ACE inhibitors in male patients with nondiabetic proteinuric nephropathies. The role of other RAS or non-RAS polymorphisms and their possible interactions with different ACE I/D genotypes are less clearly defined. Thus, evaluating the ACE I/D polymorphism is a reliable tool to identify patients at risk and those who may benefit the most of renoprotective therapy with ACE inhibitors or ARA. This may guide pharmacologic therapy in individual patients and help design clinical trials in progressive nephropathies. Moreover, it might help optimize prevention and intervention strategies at population levels, in particular, in countries where resources are extremely limited and 1 million patients continue to die every year of cardiovascular or renal disease.

Pharmacogenomics and antihypertensive drugs: a path toward personalized medicine

Pharmacogenomics focuses on genes and the transcriptome and proteome. It has the potential to enhance healthcare management by improving disease diagnosis and implementing treatments adapted to each patient. Previously, pharmacogenetics of candidate genes focused on clinical research. It is now extended by using genome-wide approaches to elucidate the inherited basis of differences between individuals in their response to drugs. We summarize relevant polymorphisms of genes involved in the pharmacokinetics and pharmacodynamics of antihypertensive drugs and we give an overview of the state of pharmacogenomic research in hypertension medicine. Even if things are getting better, current pharmacogenetic studies still lack power, adequate selection of candidate genes and knowledge of their functions at the physiological level. Finally, some specific end point phenotypes (i.e., peptides or proteins related to the metabolic cycle targeted by the drug) should be integrated to propose data that are easily applicable to personalized medicine.

Exploring design-related bias in clinical studies on receptor genetic polymorphism of hypertension

BACKGROUND AND OBJECTIVES

Although several candidate genes of Renin-Angiotensin-Aldosterone System (RAAS) have been investigated, the gene-drug relationship remains unclear. The objective was to appraise the elements of research methodology and explore potential biases, which may be contributing to discordant results in the gene-drug interaction assessment for RAAS.

METHODS

Systematic review of studies involving candidate polymorphisms, searching PubMed, and EMBASE.

RESULTS

Sixteen studies were identified. Nine studies had a genomic evaluation as the primary question. Six studies investigated more than one gene. A gene-drug interaction was evaluated in two studies and only one of the studies had a placebo arm for accurately exploring the interaction. Almost, 90% of the studies had sample sizes of less than 500 patients. Four studies combined the allele frequencies of the heterozygotes group with one of the homozygotes groups. Almost one quarter of the studies combined different therapeutics in one group. Five studies included patients in one group from previous studies in which selection criteria were not quite similar.

CONCLUSION

Most studies contain several methodological limitations. Also biases driven from patient selection, combining different alleles, combining different therapeutics, and combining end points may have occurred in these studies. These limitations and biases may contribute to inconsistency of the results of these studies.

Differential roles of Angiotensinogen and Angiotensin Receptor type 1 polymorphisms in breast cancer risk

While angiotensinogen (AGT) seems to have anti proliferative properties, angiotensin II (ATII) is a potent growth factor and it mediates its actions through the angiotensin type 1 receptor (AGTR1). In the AGT gene, the M235T polymorphism has been associated with the variation in angiotensinogen levels and in the AGTR1 gene; the C573T variant is associated with different pathologies. We aimed to evaluate the relationship of these two variants and the risk of breast cancer. These polymorphisms were genotyped in 3787 women participating the Rotterdam Study. We performed a logistic regression and a disease free survival analysis by genotype. The logistic regression yielded an odds ratio of 1.4 (95% CI: 1.1-1.9) for the MM genotype carriers versus the T allele carriers. The breast cancer free survival by AGT genotype was significantly reduced in MM genotype carriers compared to non-carriers (hazard ratio (HR) = 1.5; 95% CI: 1.1-2.2). We did not find any association of the AGTR1 polymorphism and breast cancer risk or disease free survival. Our results suggest that AGT plays a role in breast cancer risk in postmenopausal women, whereas the role of AGTR1 needs further studying.

Prevention of loss of renal function over time in patients with diabetic nephropathy

Management of hypertension is the mainstay of prevention and treatment of diabetic renal disease; evidence suggests that tight blood pressure control slows renal disease progression in established diabetic nephropathy. Inhibition of the renin-angiotensin-aldosterone system (RAAS) has renoprotective effects over and above those achieved by lowering systemic blood pressure. To date, however, no long-term study using hard end points has directly compared current mechanisms for RAAS inhibition, angiotensin II receptor blockade (ARB) and angiotensin-converting enzyme (ACE) inhibition. This issue was addressed in the recently published Diabetics Exposed to Telmisartan and Enalapril (DETAIL) study, a head-to-head comparison of telmisartan and enalapril in 250 patients with hypertension and type 2 diabetes mellitus and early-stage nephropathy. After 5 years' treatment, change in glomerular filtration rate (GFR), the primary efficacy end point, was equivalent in the 2 treatment groups, as were all secondary end points. The expected steep decline in GFR in the first year was followed by a lesser decrease in the second year and then almost complete stabilization of renal function at > or =3 years. Over 5 years, no patient went into end-stage renal disease or required dialysis. There were also no increases in albumin excretion rate, nor was there an increase in creatinine beyond 200 mumol/L. Incidence of cardiovascular morbidity and mortality was extremely low in both treatment groups, a remarkable outcome given that almost 50% of patients had evidence of cardiovascular disease at randomization. Inhibition of the RAAS should play a major part in management of patients with type 2 diabetes with nephropathy, for which both telmisartan and enalapril provide long-term renoprotection.

Pharmacogenetics of antihypertensive treatment

Hypertension is a common disorder associated with increased cardiovascular morbidity and mortality. Unfortunately, in the US only about one-third of those who are aware of their hypertensive status have their blood pressure adequately controlled. One reason for this is the variable and unpredictable response individuals have to pharmacologic treatment. Clinicians often resort to "trial-and-error" to match patients with effective drug treatment. Hypertension pharmacogenetics seeks to find genetic predictors of drug response. To date, more than forty studies have investigated associations between genetic polymorphisms and response to antihypertensive drugs. Angiotensin-converting enzyme inhibitors and beta blockers have been most frequently studied, followed by angiotensin II blockers, diuretics, adrenergic alpha-agonists, and calcium channel blockers. Renin-angiotensin-aldosterone system genes have been the most widely studied, with the angiotensin-converting enzyme I/D variant being typed in about one-half of all hypertension pharmacogenetic studies. In total, 160 possible gene polymorphism-drug interactions have been explored, with about one-quarter of these showing that genes predict drug response. However, disparate and conflicting findings have been the rule rather than the exception, and the discovery of clinically relevant antihypertensive drug-response genes remains elusive. While there is a growing enthusiasm that pharmacogenetics of hypertension is important, the translation of pharmacogenetic findings to clinical practice in the future will depend on additional studies to enhance our pharmacogenetics knowledge base, the availability of pharmacogenetic screening tests that are affordable and easy to implement in clinical practice, a cohort of clinicians who are trained to interpret genetic test results, and health care systems that pay for them. Caution regarding the future of hypertension pharmacogenetics is warranted.