ACE (I/D) genotype as a predictor of the magnitude and duration of the response to an ACE inhibitor drug (enalaprilat) in humans

Angiotensin-Converting Enzyme Inhibitors Provide Better Long-Term Survival Benefits to Patients With AMI Than Angiotensin II Receptor Blockers After Survival Hospital Discharge

AIM

Renin-angiotensin-aldosterone system inhibitors (RASIs) are widely used in high-risk cardiovascular (CV) diseases, including acute myocardial infarction (AMI). However, it is not yet clear which class of RASIs provides specific benefits to patients with AMI. The present study aimed to evaluate whether angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin II type 1 receptor blockers (ARBs) had any different effects on long-term CV and all-cause mortality in patients with AMI who received either agent from admission and were discharged alive from the hospital.

METHODS

We analyzed data of patients with AMI from the Korea Acute Myocardial Infarction Registry-National Institutes of Health registry. Cardiovascular and all-cause mortality at 12 months after AMI were assessed.

RESULTS

Among 12 481 patients with AMI who were discharged alive, RASI treatment was as follows: ACEIs (n = 5910), ARBs (n = 4009), and no RASI (n = 2562). After adjustment for multiple factors, compared with no RASI therapy, ACEI therapy was associated with lower hazard ratios (HRs) for 1-year CV and total mortality rates, whereas ARB therapy was not. In a direct comparison, compared with ARB treatment, ACEI treatment was associated with lower HRs (95% confidence interval) for CV and total mortality: 0.562 (0.420-0.753) and 0.567 (0.451-0.713), respectively. The superiority of ACEI to ARB was also observed across several subgroups. The mortality differences between the 2 treatment groups were reproduced in a propensity-score matched analysis (n = 2855 each).

CONCLUSIONS

Our study of a recent AMI registry data revealed that ACEI therapy in patients with AMI was associated with better long-term survival benefits than ARB therapy.

ACE Phenotyping as a Guide Toward Personalized Therapy With ACE Inhibitors

Background:

Angiotensin-converting enzyme (ACE) inhibitors (ACEI) are widely used in the management of cardiovascular diseases but with significant interindividual variability in the patient’s response.

Objectives:

To investigate whether interindividual variability in the response to ACE inhibitors is explained by the “ACE phenotype”—for example, variability in plasma ACE concentration, activity, and conformation and/or the degree of ACE inhibition in each individual.

Methods:

The ACE phenotype was determined in plasma of 14 patients with hypertension treated chronically for 4 weeks with 40 mg enalapril (E) or 20 mg E + 16 mg candesartan (EC) and in 20 patients with hypertension treated acutely with a single dose (20 mg) of E with or without pretreatment with hydrochlorothiazide. The ACE phenotyping included (1) plasma ACE concentration; (2) ACE activity (with 2 substrates: Hip-His-Leu and Z-Phe-His-Leu and calculation of their ratio); (3) detection of ACE inhibitors in patient’s blood (indicator of patient compliance) and the degree of ACE inhibition (ie, adherence); and (4) ACE conformation.

Results:

Enalapril reduced systolic and diastolic blood pressure in most patients; however, 20% of patients were considered nonresponders. Chronic treatment results in 40% increase in serum ACE concentrations, with the exception of 1 patient. There was a trend toward better response to ACEI among patients who had a higher plasma ACE concentration.

Conclusion:

Due to the fact that “20% of patients do not respond to ACEI by blood pressure drop,” the initial blood ACE level could not be a predictor of blood pressure reduction in an individual patient. However, ACE phenotyping provides important information about conformational and kinetic changes in ACE of individual patients, and this could be a reason for resistance to ACE inhibitors in some nonresponders.

Personalized medicine and treatment approaches in hypertension: current perspectives

In the US, hypertension affects one in three adults. Current guideline-based treatment of hypertension involves little diagnostic testing. A more personalized approach to the treatment of hypertension might be of use. Several methods of personalized treatment have been proposed and vetted to varying degrees. The purpose of this narrative review is to discuss the rationale for personalized therapy in hypertension, barriers to its development and implementation, some influential examples of proposed personalization measures, and a view of future efforts.

Genomics in CKD: Is This the Path Forward?

Recent advances in genomics and sequencing technology have led to a better understanding of genetic risk in CKD. Genetics could account in part for racial differences in treatment response for medications including antihypertensives and immunosuppressive medications due to its correlation with ancestry. However, there is still a substantial lag between generation of this knowledge and its adoption in routine clinical care. This review summarizes the recent advances in genomics and CKD, discusses potential reasons for its underutilization, and highlights potential avenues for application of genomic information to improve clinical care and outcomes in this particularly vulnerable population.

Correlation of renin angiotensin system (RAS) candidate gene polymorphisms with response to Ramipril in patients with essential hypertension

Background:

The renin-angiotensin system (RAS) is an important facet of blood pressure regulation physiology. Treatment of essential hypertension targets the RAS using Angiotensin Converting Enzyme Inhibitors (ACEIs). However, ACEIs are not uniformly effective and show inter-individual pharmacodynamic variations.

Aim:

To assess the correlation between genetic polymorphisms in the genes coding for RAS components (angiotensin converting enzyme (ACE I/D), α-adducin (ADD1) and β₁-adrenoreceptor (β1-ADR)) and response to Ramipril.

Materials and Methods:

We recruited 120 patients with essential hypertension who were administered Ramipril monotherapy initially, followed by combination therapy, if needed, based on their responses. Relationship between genotypes of the three candidate genes and decrease in the blood pressure (BP) was analyzed.

Results:

One hundred and six patients were evaluable at the end of the study period and 21 different genotypes were observed among them. Seven of them were classified as responders after 8 weeks and at the end of 12 weeks, an additional 77 (72.64%) were deemed responders. 19/22 non-responders were treated with combination therapy and 7/19 (36.84%) showed a response to the same. There was a significant difference between the proportions of responders and non-responders among the genotypes of the ADD1 and β1-ADR genes (P = 0.005 and 0.003, respectively). The best predictors of response to Ramipril 5 mg daily were the II/GG/SS, II/TG/SS, II/GG/SG, ID/GG/SS, ID/GG/SG and ID/TT/SS and DD/GG/SS; II/GG/GG, II/TT/SG, ID/TG/SG, ID/TT/SG, DD/GG/SG and DD/GG/GG were moderately predictive and II/TT/SS, II/TG/GG, ID/TG/GG, DD/TG/SG and DD/TG/GG were poorly predictive of response.

Discussion:

Variable responses to Ramipril may be the result of genetic factors.

Conclusion:

Pre-prescription genotyping may help individualize treatment.

Exercise intensity modulates capillary perfusion in correspondence with ACE I/D modulated serum angiotensin II levels

During exercise the renin-angiotensin system is stimulated. We hypothesized that the increase in serum angiotensin II (AngII) levels after exercise is dependent on exercise intensity and duration and secondly that people with the ACE-II genotype will show a higher increase in AngII serum levels. We also assumed that perfusion of upper limbs is transiently reduced with maximal cycling exercise and that subjects with the ACE-II compared to the ACE-ID/DD genotype will have a higher capillary perfusion due to lower AngII levels. Ten healthy subjects completed a maximal exercise test, a 12-min exercise test at ventilatory threshold and a 3-min test at the respiratory compensation point. AngII serum levels and capillary recruitment of the skin in the third finger were measured before and after exercise and breath-by-breath gas exchange during exercise was assessed. Baseline levels of AngII levels were lower prior to the 3-min test which took place on average 5 days after the last exercise. A two-fold increase compared to baseline levels was found for AngII only immediately after the 3-min test and not after the maximal exercise test and 12-min of exercise. Subjects without the I allele showed a decrease in AngII values after the maximal test in contrast to subjects with the ACE-II/ID genotype. Subjects with the ACE-II genotype had a 1.8 times significant higher capillary perfusion in the finger after exercise. A trend was observed for a 34.3% decreased capillary recruitment in the ACE-ID/DD genotype after exercise. We conclude that the rise in AngII after exercise is intensity dependent and that variability in serum AngII and capillary perfusion is related to the ACE I/D polymorphism.

Developments in renal pharmacogenomics and applications in chronic kidney disease

Chronic kidney disease (CKD) has shown an increasing prevalence in the last century. CKD encompasses a poor prognosis related to a remarkable number of comorbidities, and many patients suffer from this disease progression. Once the factors linked with CKD evolution are distinguished, it will be possible to provide and enhance a more intensive treatment to high-risk patients. In this review, we focus on the emerging markers that might be predictive or related to CKD progression physiopathology as well as those related to a different pattern of response to treatment, such as inhibitors of the renin–angiotensin system (including angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers; the vitamin D receptor agonist; salt sensitivity hypertension; and progressive kidney-disease markers with identified genetic polymorphisms). Candidate-gene association studies and genome-wide association studies have analyzed the genetic basis for common renal diseases, including CKD and related factors such as diabetes and hypertension. This review will, in brief, consider genotype-based pharmacotherapy, risk prediction, drug target recognition, and personalized treatments, and will mainly focus on findings in CKD patients. An improved understanding will smooth the progress of switching from classical clinical medicine to gene-based medicine.

Low-grade inflammation and ambulatory blood pressure response to antihypertensive treatment: the ALPHABET study

BACKGROUND

We examined whether the level of highsensitivity C-reactive protein (hsCRP), a marker of low-grade inflammation, predicted the response of clinic and ambulatory blood pressure (BP) to antihypertensive treatment.

METHODS

A randomized, open-label, multicenter trial was performed in 88 hypertensive patients (mean age = 63.4 years) allocated to receive losartan 50 mg or amlodipine 5 mg for 4 weeks, and each treatment was changed to losartan 50 mg/hydrochlorothiazide (HCTZ) 12.5 mg in combination or amlodipine 10 mg for a further 4 weeks. Clinic and ambulatory BP were measured before and after 8 weeks of treatment, and hsCRP was measured at baseline.

RESULTS

The patients were divided into groups with hsCRP levels above and below the median (0.47 mg/L) for the study population. In the total population, 24-hour systolic BP (SBP) (P = 0.03) and daytime SBP (P = 0.01) were significantly higher in the above-median hsCRP group after 8 weeks of treatment. In multivariable regression analysis, baseline hsCRP was a significant determinant of the percentage change in daytime SBP (β = 0.29; P = 0.02) in the total population. In the losartan/HCTZ treatment group, changes in 24-hour SBP, daytime SBP, and diastolic BP were significantly smaller in the above-median hsCRP group than the below-median hsCRP group, whereas the amlodipine group did not show these differences.

CONCLUSIONS

Baseline low-grade inflammation in patients with hypertension was associated with a poor ambulatory BP response, especially with losartan/HCTZ treatment. Initial measurement of hsCRP could be useful for selection of an appropriate antihypertensive drug.

Renin-angiotensin system, hypertension, and chronic kidney disease: pharmacogenetic implications

About 80% of CKD (chronic kidney disease) patients are hypertensive, and kidney function and blood pressure are clearly related to both physiologic and pathologic conditions in a "vicious cycle". In this pathologic scenario, there is a renin-angiotensin system (RAS) hyperactivity associated to progression of renal damage. Current guidelines indicate as the first choice of antihypertensive intervention, the pharmacologic blockade of the RAS. Nonetheless, both response to treatment and renal protection have considerable inter-individual variability. The main aims of this review are to describe the genetic characteristics of RAS components and to identify the possible pharmacogenetic implications for RAS-blocker drugs in the hypertension-CKD scenario. To date, RAS polymorphisms have not been consistently associated to antihypertensive response and studies focusing on CKD are scarce. Nonetheless, pharmacogenetic studies for the RAS-blocker drugs could still be further explored, especially with new generation tools and focusing not only on the antihypertensive response, but also on renal protection as well.

Drug-Disease Interactions: Losartan Effect Is Not Downregulated by Rheumatoid Arthritis

Inflammatory conditions, such as rheumatoid arthritis, reduce response to calcium channel and beta-adrenergic antagonists but not the angiotensin II type 1 receptor (AT(1)R) antagonist valsartan. Inflammation also reduces clearance of some drugs or active metabolite, thereby reducing response. Active (n = 14) and controlled rheumatoid arthritis (n = 12) and healthy subjects (n = 12) received losartan (100 mg). Blood pressures were measured, and samples were taken for pharmacokinetic and inflammatory mediator concentration determination. Active disease significantly increased arthritic index, nitric oxide, and Creactive protein. Although no between-group difference in plasma losartan concentration-time curves was observed, concentrations of the active metabolite, EXP 3174, were significantly reduced by arthritis. This, however, was not accompanied by reduced clinical response. One subject produced no detectable concentrations of EXP 3174 likely due to insufficient CYP2C9 activity. Despite reduced concentrations of the active metabolite, AT1R antagonists potency does not appear to be reduced by inflammation.

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.

Response to angiotensin-converting enzyme inhibition is selectively blunted by high sodium in angiotensin-converting enzyme DD genotype: evidence for gene-environment interaction in healthy volunteers

BACKGROUND

Renin-angiotensin-aldosterone system blockade is a cornerstone in cardiovascular protection. Angiotensin-converting enzyme (ACE)-DD genotype has been associated with resistance to angiotensin-converting enzyme inhibition (ACEi), but data are conflicting. As sodium intake modifies the effect of ACEi as well as the genotype-phenotype relationship, we hypothesize gene-environment interaction between sodium-status, the response to ACEi, and ACE genotype.

METHOD

Thirty-five male volunteers (26 ± 9 years; II n = 6, ID n = 18, DD n = 11) were studied during placebo and ACEi (double blind, enalapril 20 mg/day) on low [7 days 50 mmol Na/day (low salt)] and high [7 days 200 mmol Na/day (high salt)] sodium, with a washout of 6 weeks in-between. After each period mean arterial pressure (MAP) was measured before and during graded infusion of angiotensin II (Ang II).

RESULTS

During high salt, ACEi reduced MAP in II and ID, but not in DD [II: 88 (78-94) versus 76 (72-88); ID: 87 (84-91) versus 83 (79-87); both P < 0.05 and DD: 86 (82-96) versus 88 (80-90); ns, P < 0.05 between genotypes]. However, during low salt, ACEi reduced MAP in all genotype groups [II: 83 (78-89) versus 77 (72-83); ID: 88 (84-91) versus 82 (78-86); DD: 84 (80-91) versus 81 (75-85); all P < 0.05]. During high salt + ACEi, the Ang II response was blunted in DD, with an 18% rise in MAP during the highest dose versus 22 and 31% in ID and II (P < 0.05). Low salt annihilated these differences.

CONCLUSION

In healthy participants, the MAP response to ACEi is selectively blunted in DD genotype during high salt, accompanied by blunted sensitivity to Ang II. Low salt corrects both abnormalities. Further analysis of this gene-environment interaction in patients may contribute to strategies for improvement of individual treatment efficacy.

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.

Multilocus analysis in candidate genes ACE, AGT, and AGTR1 and predisposition to peripheral arterial disease: role of ACE D/-240T haplotype

OBJECTIVE

Peripheral arterial disease (PAD) is a common manifestation of systemic atherosclerosis. Apart from traditional cardiovascular risk factors, several novel biologic mediators and genetic predisposing factors appear relevant in determining the atherogenetic process leading to PAD. Genes encoding for renin angiotensin system (RAS) components have been proposed as candidate in atherosclerosis. This study investigated four polymorphisms in angiotensinogen (AGT), angiotensin converting enzyme (ACE), and angiotensin II receptor type 1 (AGTR1), genes of RAS, in both predicting PAD and modulating the severity of the disease.

METHODS

The ACE I/D and -240A>T, AGT M235T, and AGTR1 1166A>C polymorphisms were analyzed in 281 PAD patients and in 485 controls comparable for age and sex.

RESULTS

The ACE D and -240T alleles both significantly influenced the predisposition to PAD. The ACE D, but not -240 T, allele remained associated with PAD after Bonferroni correction (P = .004) and adjustment for cardiovascular risk factors (P = .03). The ACE D allele influenced PAD predisposition with a dose-dependent effect (odds ratio for ACE ID vs II genotype, 1.77; P = .006; ACE DD vs II genotype, 2.15; P = .001). The haplotype reconstruction analysis for the ACE gene showed that the D/-240T haplotype significantly and independently influenced the predisposition to PAD (P = .02). In 190 PAD patients with no additional atherosclerotic localizations (isolated PAD), a significant association between ACE D and -240T alleles and PAD was observed. Only the ACE D allele remained associated with isolated PAD after Bonferroni correction (P = .02) and after adjustment for cardiovascular risk factors (P = .02). The haplotype reconstruction analysis for the ACE gene showed that the D/-240T, but not the D/-240A haplotype significantly influenced the predisposition to PAD (P = .0003). No influence of the polymorphisms analyzed on the severity of the disease, according to Rutherford categories, was found.

CONCLUSIONS

The present study contributes data to highlight the role of the ACED/-240T haplotype in predisposing to PAD, also in the absence of other atherosclerotic comorbidities.

Keeping pace with ACE: are ACE inhibitors and angiotensin II type 1 receptor antagonists potential doping agents?

In the decade since the angiotensin-converting enzyme (ACE) gene was first proposed to be a 'human gene for physical performance', there have been numerous studies examining the effects of ACE genotype on physical performance phenotypes such as aerobic capacity, muscle function, trainability, and athletic status. While the results are variable and sometimes inconsistent, and corroborating phenotypic data limited, carriers of the ACE 'insertion' allele (the presence of an alu repeat element in intron 16 of the gene) have been reported to have higher maximum oxygen uptake (VO2max), greater response to training, and increased muscle efficiency when compared with individuals carrying the 'deletion' allele (absence of the alu repeat). Furthermore, the insertion allele has been reported to be over-represented in elite athletes from a variety of populations representing a number of endurance sports. The mechanism by which the ACE insertion genotype could potentiate physical performance is unknown. The presence of the ACE insertion allele has been associated with lower ACE activity (ACEplasma) in number of studies, suggesting that individuals with an innate tendency to have lower ACE levels respond better to training and are at an advantage in endurance sporting events. This could be due to lower levels of angiotensin II (the vasoconstrictor converted to active form by ACE), higher levels of bradykinin (a vasodilator degraded by ACE) or some combination of the two phenotypes. Observations that individuals carrying the ACE insertion allele (and presumably lower ACEplasma) have an enhanced response to training or are over-represented amongst elite athletes raises the intriguing question: would individuals with artificially lowered ACEplasma have similar training or performance potential? As there are a number of drugs (i.e. ACE inhibitors and angiotensin II type 1 receptor antagonists [angiotensin receptor blockers--ARBs]) that have the ability to either reduce ACEplasma activity or block the action of angiotensin II, the question is relevant to the study of ergogenic agents and to the efforts to rid sports of 'doping'. This article discusses the possibility that ACE inhibitors and ARBs, by virtue of their effects on ACE or angiotensin II function, respectively, have performance-enhancing capabilities; it also reviews the data on the effects of these medications on VO2max, muscle composition and endurance capacity in patient and non-patient populations. We conclude that, while the direct evidence supporting the hypothesis that ACE-related medications are potential doping agents is not compelling, there are insufficient data on young, athletic populations to exclude the possibility, and there is ample, albeit indirect, support from genetic studies to suggest that they should be. Unfortunately, given the history of drug experimentation in athletes and the rapid appropriation of therapeutic agents into the doping arsenal, this indirect evidence, coupled with the availability of ACE-inhibiting and ACE-receptor blocking medications may be sufficiently tempting to unscrupulous competitors looking for a shortcut to the finish line.

Renin-angiotensin-aldosterone system (RAAS) pharmacogenomics: implications in heart failure management

Blockade of the renin-angiotensin-aldosterone system (RAAS) with ACE inhibitors has been a cornerstone of heart failure therapy for over 15 years. More recently, further blockade of RAAS with aldosterone antagonists and angiotensin receptor blockers (ARBs) has been studied. While these therapies have certainly improved outcomes in the treatment of heart failure, morbidity and mortality remain extremely high. Furthermore, polypharmacy and complex regimens of seven medications on average is the norm for management of heart failure. This results in increased costs, patient burden, and uncertainty as to the best course of therapy. The ability to personalize patients' therapeutic regimens using pharmacogenomics has the potential of providing more effective and efficient use of RAAS-modulating medications. This review highlights the implications of major RAAS pharmacogenetic studies, while outlining future directions for translation to practice.

The role of angiotensin-converting enzyme gene insertion/deletion polymorphism for blood pressure regulation in areca nut chewers

Areca tannin has been suggested as having a blood pressure regulatory effect through its ability to inhibit the pressor response to both angiotensin I and II. As genetic and environmental factors determine the susceptibility and development of diseases and no report has been published concerning the genetic interaction of metabolic effects in areca nut/betel quid (BQ) chewers, it is proposed that the cardiovascular effects of chronic BQ usage can be affected by the polymorphism of the angiotensin converting enzyme (ACE) gene. This is a cross-sectional community-based study. A total of 189 BQ chewing subjects and 256 non-chewing controls were studied. BQ chewing status was determined by using a structured questionnaire, and insertion/deletion (I/D) polymorphisms were determined by a polymerase chain reaction. BQ chewers with the DD genotype had significantly lower blood pressure, pulse pressure, and prevalence of hypertension compared with those of chewers with II or ID genotypes. Multiple stepwise regression analysis confirmed that the ACE I/D genotype was independently associated with systolic blood pressure (SBP). BQ chewers with the DD genotype accounted for a significant age, sex, and waist-to-hip ratio adjusted decrease in SBP (-5.9 mm Hg, P=0.021). This finding suggests that BQ chewing may be related to blood pressure regulation, which supports the hypothesis that concomitant genetic susceptibility and environmental factors determine the level of blood pressure.

Polymorphism modulates symptomatic response to antiarrhythmic drug therapy in patients with lone atrial fibrillation

BACKGROUND

The angiotensin-converting enzyme (ACE) deletion allele, ACE D, is associated with increased ACE activity and adverse outcomes in cardiovascular disease. Although activation of the renin-angiotensin-aldosterone system (RAAS) now appears to play a role in the pathophysiology of atrial fibrillation (AF), it remains to be determined if ACE genotype impacts response to conventional AAD therapy in patients with AF.

OBJECTIVES

The purpose of this study was to investigate whether response to antiarrhythmic drug (AAD) therapy in patients with AF is modulated by the ACE I/D polymorphism.

METHODS

We studied 213 patients (147 men, 66 women; ages 52 +/- 15 years) prospectively enrolled in the Vanderbilt AF Registry. AAD therapy outcome was defined prospectively as response if there was a >or=75% reduction in symptomatic AF burden or nonresponse if AF burden was unchanged, necessitating a change in drugs or therapy.

RESULTS

Lone AF (age <65 years, no identifiable cause) was present in 72 (34%) patients, whereas hypertension was the most common underlying disease in the remaining 141 (41%). AF was paroxysmal in 170 (80%) and persistent in 43 (20%). The frequencies of the DD, ID, and II genotypes were in Hardy-Weinberg equilibrium. Lone AF and DD/ID genotypes were highly significant predictors of failure of drug therapy (P <.005). In patients with lone AF, failure of drug response was 5%, 41%, and 47% in patients with II, ID, and DD genotypes, respectively, (P <.005, II vs. ID/DD).

CONCLUSIONS

These results provide further evidence for a role of RAAS activation in the pathophysiology of AF and point to a potential role for stratification of therapeutic approaches by ACE genotype.

Genetics of arterial hypertension and hypotension

Human hypertension affects affects more than 20% of the adult population in industrialized countries, and it is implicated in millions of deaths worldwide each year from stroke, heart failure and ischemic heart disease. Available evidence suggests a major genetic impact on blood pressure regulation. Studies in monogenic hypertension revealed that renal salt and volume regulation systems are predominantly involved in the genesis of these disorders. Mutations here affect the synthesis of mineralocorticoids, the function of the mineralocorticoid receptor, epithelial sodium channels and their regulation by a new class of kinases, termed WNK kinases. It has been learned from monogenic hypotension that almost all ion transporters involved in the renal uptake of Na(+) have a major impact on blood pressure regulation. For essential hypertension as a complex disease, many candidate genes have been analysed. These include components of the renin-angiotensin-aldosterone system, adducin, beta-adrenoceptors, G protein subunits, regulators of G protein signalling (RGS) proteins, Rho kinases and G protein receptor kinases. At present, the individual impact of common polymorphisms in these genes on the observed blood pressure variation, on risk for stroke and as predictors of antihypertensive responses remains small and clinically irrelevant. Nevertheless, these studies have greatly augmented our knowledge on the regulation of renal functions, cellular signal transduction and the integration of both. Together, this provides the basis for the identification of novel drug targets and, hopefully, innovative antihypertensive drugs.

Lone and secondary nonvalvular atrial fibrillation: role of a genetic susceptibility

BACKGROUND

An involvement of the renin angiotensin system in atrial fibrillation (AF) has been hypothesized, and ACE DD genotype has been suggested to influence the predisposition to AF. The aim of this study was to investigate the role of the ACE I/D polymorphism in relation to the different clinical forms of AF, lone and secondary nonvalvular atrial fibrillation (NVAF).

METHODS

510 consecutive patients with documented NVAF (106 patients had lone, and 404 secondary NVAF), and 520 controls with a negative history of cardiovascular disease have been studied.

RESULTS

A significant difference in allele frequency between lone and secondary NVAF (p=0.002) has been found. The ACE D allele was associated with the predisposition to lone NVAF under a dominant, recessive and additive model, both at univariate and multivariate analysis, after adjustment for age and gender (multivariate analysis: dominant OR=2.87, p=0.02; recessive OR=2.01, p=0.003; additive OR=4.47, p<0.0001). ACE D allele was significantly associated with secondary NVAF at both univariate and multivariate analysis under a recessive and additive, but not dominant, model (multivariate analysis: recessive OR=1.89, p=0.001; additive OR=2.50, p<0.0001).

CONCLUSIONS

This study highlights the role of ACE gene in predisposing to both lone and secondary NVAF, further contributing to penetrate the genetic mechanisms responsible for this complex disease. The clinical relevance of our results may be related to the possible characterization of subjects predisposed to NVAF in the absence of traditional risk factors, and to the use of ACE-inhibitors therapy able to improve the arrhythmogenic substrate.

Stand der Pharmakogenetik in der klinischen Arzneimitteltherapie

Individual differences in the effect and side effect of drugs are partly due to genetic factors (genetic polymorphisms). The responsible polymorphisms lie in genes encoding for drug metabolism and transport but also in direct and indirect drug targets. While genetic variants in pharmacokinetic structures exert effects on drug efficacy via the differences in drug exposure, polymorphisms in drug targets can directly affect clinical efficacy and may lead to a broad variation spectrum between inefficacy and severe side effects. However, at present, our knowledge on genetic variants in drug targets is less detailed than the knowledge on pharmacogenetic variability within drug metabolism. A goal of pharmacogenetic diagnostics implemented in clinical practice is to better predict the individual drug effects on the basis of molecular-genetic profiles. Therapy recommendations can be given as dose adjustments, in particular in the case of polymorphisms of drug metabolizing enzymes which will lead to less variable drug concentrations. At present there are few examples of the application of pharmacogenetic tests in Germany in order to improve and individualize drug therapy. The reasons for this are multifold. On the one hand it is due to the limited awareness of pharmacogenetics; on the other hand it may be due to the lack of fast and economical availability of the appropriate laboratory tests. The most important reason, however, may be that most results of pharmacogenetic research are so far not translated into therapeutically usable conclusions and therapy recommendations. Thus, testing for a genotype without concrete consequences for the drug therapy of an individual patient does not make sense. Pharmacogenetic research, thereby, stands in many cases at the threshold to clinical applicability and in many cases, for instance for the genotyping for thiopurine methyltransferase polymorphisms prior to azathioprine therapy or of dihydropyrimidine dehydrogenase polymorphisms prior to treatment with 5-fluorouracil, as well as for diagnostics of CYP2D6 before therapy with certain tricyclic antidepressants and neuroleptics, one would ask already today whether a such drug therapy is still responsible without pharmacogenetic diagnostics.

Sarcopenia – A Potential Target for Angiotensin-Converting Enzyme Inhibition?

Society is ageing. There has been a steady increase in the number of people aged 65 years and over throughout the 20th century and this trend is predicted to continue worldwide. This has resulted in an increase in the incidence of sarcopenia, which is a loss of muscle mass and function with age. Maintenance of muscular function into old age is critical to sustaining normal daily activity and functional independence. Sarcopenia is associated with increased morbidity and mortality. Till now most efforts to counteract sarcopenia have met with limited success. We postulate that targeting the renin-angiotensin system through angiotensin-converting enzyme (ACE) inhibition could play a role in countering sarcopenia. ACE inhibitors could work by preventing mitochondrial decline and improving endothelial function and muscle metabolism. We describe the literature to support our hypothesis that sarcopenia may be a potential therapeutic target for ACE inhibitors.

Pharmacogenomics of blood pressure response to antihypertensive treatment

PURPOSE IDENTIFICATION: Inter-individual variability in blood pressure response to treatment is well documented, but a clinically useful means to distinguish responders from non-responders has been elusive. With the advent of new technologies and genomic knowledge, more investigators are seeking to identify genetic determinants of blood pressure response to therapy.

STUDY SELECTION

We identified studies of candidate polymorphisms from an initial PubMed search using the MESH terms 'Hypertension: Drug Therapy' and 'Genetics' or 'Pharmacogenetics', limiting results to English-language publications on studies in human adults. We further identified specific polymorphisms of interest noted in earlier reviews and performed additional PubMed searches based on these candidate genes. Pertinent studies were further extracted from the references of studies already identified. We focused on clinical trials that measured blood pressure response to a medication or class of medications over a minimum of 4 weeks.

DATA EXTRACTION

We evaluated studies looking at blood pressure response to commonly used classes of antihypertensive medications by major genetic variants. RESULTS OF ANALYSIS: Although many studies show that blood pressure response to a given class of antihypertensive medications varies by genotype for different polymorphisms, none of the genotypes identified consistently predicted blood pressure response.

CONCLUSIONS

Common variants may influence response to diuretics, beta-blockers, angiotensin-converting enzyme inhibitors, and angiotensin receptor blockers, but studies of polymorphisms have generally yielded conflicting results. The inclusion of pharmacogenomic studies in large clinical trials and other more innovative investigative methods may provide greater clarity of the potential role for genotyping in the treatment of patients with hypertension.

Comparison of the effect of enalapril and losartan in conjunction with surgical coronary revascularisation versus revascularisation alone on systemic endothelial function

OBJECTIVES

To investigate the effect of enalapril, losartan, and surgical coronary revascularisation on endothelial function, and the role of the angiotensin converting enzyme (ACE) insertion (I)/deletion (D) polymorphism.

DESIGN

Randomised, controlled, blinded end point study.

SETTING

University tertiary referral cardiac centre.

PATIENTS AND INTERVENTIONS

49 men awaiting coronary artery bypass grafting (CABG) were randomly assigned to treatment with losartan, enalapril, or control for two months before and three months after surgery.

MAIN OUTCOME MEASURES

Endothelial function was blindly analysed by brachial artery flow mediated dilatation (FMD) and ACE I/D genotype was determined.

RESULTS

FMD was impaired at baseline (1.0-1.7%) and after five months had improved to 5.2% with enalapril (p = 0.015), 5.0% with losartan (p = 0.0004), and 3.0% with CABG alone (p = 0.05). Patients with the II genotype had lower baseline FMD than those with DI or DD (0.1% v 1.7%, p = 0.038) and after enalapril or losartan treatment had greater improvement in FMD (mean (SEM) 7.1 (1.1)%) than patients with DI (3.1 (1.3)%, p = 0.024) or DD genotype (3.1 (1.1)%, p = 0.02).

CONCLUSIONS

Enalapril and losartan, with surgical coronary revascularisation, significantly improve systemic endothelial function. Revascularisation alone produces a quantitatively smaller, but still significant, improvement. The ACE genotype significantly modulates this response. Patients with the II genotype have a more pronounced impairment in endothelial function at baseline and a greater improvement in response to treatment with these agents.

Emerging strategies and applications of pharmacogenomics

The rapid pace of genomic science advancements, including the completion of the human genome sequence, the extensive cataloguing of genetic variation and the acceleration of technologies to assess such variation, combined with clinical programmes with rich phenotypic data, serve as the foundation for the design and execution of pharmacogenomic studies which have an impact on the pharmaceutical pipeline from early discovery through to the marketplace. The authors discuss the required infrastructure to support pharmacogenomic studies and provide insight into the strategies and practical application to influence decision making in the pharmaceutical setting. Further, the influence of pharmacogenomics is currently affecting patient care in the oncology area and is highlighted as evident impact in the marketplace.

Angiotensinogen and angiotensin-converting enzyme gene copy number and angiotensin and bradykinin peptide levels in mice

OBJECTIVE

To test the hypothesis that changes in gene expression that may accompany angiotensinogen (AGT) and angiotensin-converting enzyme (ACE) gene polymorphism cause alteration in angiotensin and bradykinin peptide levels.

DESIGN

Mice with one or two genes for AGT and ACE allow assessment of the effects of modest alteration in AGT and ACE gene expression on angiotensin and bradykinin peptide levels.

METHODS

Angiotensin and bradykinin peptides were measured in the blood, kidney, heart, lung, adrenal, brain, and aorta of mice that were either wild-type (+/+), heterozygous (+/-) or null (-/-) for either the AGT or ACE gene.

RESULTS

Angiotensin I and angiotensin II were not detectable in blood or tissues of AGT -/- mice, which had increased bradykinin levels in kidney and lung. ACE -/- mice had markedly reduced angiotensin II levels and increased bradykinin levels in blood and tissues. However, despite reduced AGT and ACE gene expression, angiotensin and bradykinin peptide levels in AGT and ACE +/- mice were no different from the levels in wild-type mice.

CONCLUSION

Although the AGT and ACE genes are fundamental determinants of angiotensin and bradykinin peptide levels, compensatory mechanisms attenuate the effect of modest change in AGT and ACE gene expression on the levels of these peptides. Identification of these compensatory mechanisms may provide new candidate genes for investigation in humans.

ACE DD Genotype: A Predisposing Factor for Abdominal Aortic Aneurysm

OBJECTIVE

To examine the role of polymorphisms in angiotensin converting enzyme (ACE, I/D) and angiotensin II receptor (AT1R, A1166C) in the development of abdominal aortic aneurysm (AAA).

MATERIALS AND METHODS

We investigated 250 consecutive patients, 217 males and 33 females (median age 72, range 50-83), undergone AAA elective repair and 250 healthy controls, comparable for sex and age. ACE and AT1R polymorphisms were studied by PCR-RFLP analysis. The genotype distribution was in Hardy-Weinberg equilibrium for all polymorphisms.

RESULTS

The genotype distribution and allele frequency of ACE I/D, but not AT1R A1166C polymorphism were significantly different between patients and controls (ACE I/D: p=0.0002 and p<0.0001, respectively, and AT1R A1166C: p=0.6 and p=0.4, respectively). An association between the ACE DD genotype and the predisposition to AAA was found (OR DD vs. ID+II=1.9 95% CI 1.3-2.9, p<0.0001). Multivariate analysis adjusted for age, sex, traditional vascular risk factors and other atherosclerotic localizations, showed ACE DD genotype to be independently related to the disease (OR DD vs. ID+II=2.4, 95% CI 1.3-4.2 p=0.003).

CONCLUSIONS

Our findings document that ACE DD genotype represents a susceptibility factor for AAA.

T1198C Polymorphism of the Angiotensinogen Gene and Antihypertensive Response to Angiotensin-Converting Enzyme Inhibitors

This study examined the association between T1198C polymorphism of the angiotensinogen (AGT) gene and the blood pressure response to ACE inhibitors in a Chinese hypertensive cohort. After a 2-week single-blind placebo run-in period, benazepril (10-20 mg/day) or imidapril (5-10 mg/day) was administered for 6 weeks to 509 patients with mild-to-moderate essential hypertension. Polymerase chain reaction combined with restriction enzyme digestion was used to detect the polymorphism, and the patients were classified as having the TT, TC, or CC genotype. The achieved changes in systolic and diastolic blood pressure (SBP and DBP) were analyzed to determine their association with genotypes at the AGT gene locus. In the total 509 patients, the TT genotype was observed in 44 patients (8.7%), the TC genotype in 214 patients (42.0%), and the CC genotype in 251 patients (49.3%). The SBP reductions in patients with the TT genotype, TC genotype, and CC genotype were -15.3+/-12.7 mmHg, -14.0+/-12.7 mmHg, and -14.4+/-12.4 mmHg, respectively (p=0.809). The DBP reductions in patients with the TT genotype, TC genotype, and CC genotype were -8.5+/-8.1 mmHg, -8.3+/-7.5 mmHg, and -8.9+/-6.6 mmHg, respectively (p=0.638). There were no significant differences in the changes in SBP or DBP after treatment among the three genotype groups. In conclusion, these results suggest that the AGT genotype does not predict the blood pressure-lowering response to antihypertensive treatment with ACE inhibitors in Chinese hypertensive patients.

Impact of angiotensin-converting enzyme gene polymorphism on neurohormonal responses to high- versus low-dose enalapril in advanced heart failure

BACKGROUND

The impact of angiotensin-converting enzyme (ACE) gene polymorphism on neurohormonal dose response to ACE inhibitor therapy is unclear.

METHODS

ACE Insertion (I) or Deletion (D) genotype was determined in 74 patients with chronic heart failure who were randomly assigned to receive either high-dose or low-dose enalapril over a period of 6 months. Monthly pre-enalapril and post-enalapril neurohormone levels (serum ACE activity (sACE), plasma angiotensin II (A-II), plasma renin activity (PRA), and serum aldosterone (ALDO) were compared between genotype subgroups and between patients who received high- or low-dose enalapril within each genotype subgroup.

RESULTS

At baseline, predose/postdose sACE and postdose PRA were significantly higher in the DD genotype. At 6-month follow-up, postdose sACE was reduced in a dose-dependent fashion in all three genotypes (P < .05). However, predose and postdose ALDO and A-II levels did not differ between each genotype subgroup at baseline or by enalapril dose within each genotype subgroup. ALDO escape and A-II reactivation were not affected by ACE genotype or enalapril dosage.

CONCLUSIONS

Predose sACE were consistently higher in the DD genotype when compared with ID or II subgroups. Despite a dose-dependent suppression of sACE, there were no observed statistically significant differences in ALDO and A-II suppression or escape with escalating doses of enalapril within each subgroup.

Pharmacogenetics‐Based New Therapeutic Concepts

Pharmacogenetics, one of the fields of clinical pharmacology, studies how genetic factors influence drug response. If hereditary traits are taken into account appropriately before starting drug treatment, the type of drug and its dosage can be tailored to the individual patient's needs. Pharmacogenetics adds a considerable amount of stringency to the doctor's therapeutic approach. Today, it is the relationship between dosage requirements and genetic variations in drug metabolizing enzymes like cytochrome P450 (CYP) 2D6 and CYP2C19, or in drug transporters like p-glycoprotein, that is substantiated best. A standard dose will bring about more adverse effects than usual if enzymatic activity is lacking or feeble. Sometimes, however, therapeutic response might be better due to higher concentrations: proton pump inhibitors for eradication of Helicobacter pylori are more efficacious in carriers of a deficient CYP2C19 variant. The drug's interaction with its target (e.g. receptor) also depends on genetic factors. In some cases genetic tests can help distinguish between responders and non-responders of a specific drug treatment. The first pharmacogenetic tests are already on the market.

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.

Effects of perindopril treatment on hemostatic function in patients with essential hypertension in relation to angiotensin converting enzyme (ACE) and plasminogen activator inhibitor-1 (PAI-1) gene polymorphisms

BACKGROUND AND AIM

An imbalance in the hemostatic system is a frequent finding in untreated essential hypertension (HT), and it has been shown that treatment with angiotensin converting entyme (ACE) inhibitors improves hemostatic function. In order to elucidate the role of genetic factors, we studied hemostasis in patients with untreated and treated HT and correlated the results with ACE I/D and plasminogen activator enhibitor-1 (PAI-1) 4G/5G gene polymorphisms.

METHODS AND RESULTS

Forty-three males with HT (mean age 31.7 +/- 6.8 years) were compared with 34 age and gender-matched controls. All of the patients were treated with perindopril (4 mg/day) and, after one and six months of therapy, their levels of plasma fibrinogen (Fb), t-PA antigen, PAI-1 antigen, von Willebrand factor (vWF), ACE activity and blood pressure were measured. ACE and PAI-1 genotypes were identified by means of the polymerase chain reaction on DNA isolated from peripheral blood lymphocytes. Untreated patients had significantly higher levels of Fb, PAI-1 (p < 0.01) and t-PA (p < 0.05) regardless of their ACE or PAI-1 genotypes. Perindopril reduced blood pressure regardless of ACE or PAI-1 genotype (p < 0.001). ACE II homozygotes showed the greatest decrease in ACE activity (p < 0.01) and a significant reduction in Fb levels (p < 0.05) after just one month of treatment. Analysis of the group as a whole revealed an increase in t-PA antigen levels after six months of treatment, regardless of ACE or PAI-1 genotype (p < 0.01).

CONCLUSIONS

Our results show that essential hypertension predisposes to the procoagulant state characterized by hyperfibrinogenemia and hypofibrinolysis. Perindopril reduced fibrinogen levels in ACE II homozygotes due to its more potent inhibitory action on the renin-angiotensin system in such patients. It improved fibrinolysis by increasing t-PA levels regardless of ACE and PAI-1 genotype.

Relationship between polymorphism of the angiotensin-converting enzyme gene and the response to angiotensin-converting enzyme inhibition in hypertensive patients

The aim of this study was to investigate the relationship between polymorphism of the anglotensin-converting enzyme (ACE) gene and the blood pressure response to ACE inhibition in a hypertensive cohort. Imidapril (5-10 mg/day) or benazepril (10-20 mg/day) was administered for 6 weeks to 517 essential hypertensives. ACE gene polymorphism was examined by the polymerase chain reaction (PCR) method and the patients were classified as having the 190-bp deletion homozygous (DD) genotype, the 490-bp insertion homozygous (II) genotype, or the 490-bp insertion, 190-bp deletion heterozygous (ID) genotype. The achieved change in systolic and diastolic blood pressure (SBP and DBP) was analyzed for association with genotypes at the ACE gene locus. The DD genotype was observed in 132 patients (25.5%), the ID genotype in 255 patients (49.3%), and the II genotype in 130 patients (25.2%). The SBP reductions in the patients with the DD genotype, II genotype, and ID genotype were -14.5 +/- 12.7 mmHg, -14.3 +/- 13.1 mmHg and -14.0 +/- 12.2 mmHg, respectively (p = 0.94). The DBP reductions in the patients with the DD genotype, II genotype, and ID genotype were -8.7 +/- 7.4 mmHg, -8.7 +/- 7.7 mmHg and -8.5 +/- 6.7 mmHg, respectively (p = 0.96). There was no significant association between the ACE gene polymorphisms and the response to ACE inhibition. These results suggest that ACE genotype does not predict the blood pressure-lowering response to antihypertensive treatment with ACE inhibition.

Rheumatoid arthritis does not reduce the pharmacodynamic response to valsartan

Inflammatory conditions decrease the cardiovascular response to calcium channel and beta-adrenergics blockers due, likely, to down-regulation of the receptors mediated by pro-inflammatory mediators such as C-reactive protein (CRP), nitric oxide (NO), and tumor necrosis factor. The purpose of this investigation was to determine whether down-regulation is also evident in angiotensin II type 1 receptors (AT(1)R) during varying inflammatory states. Normotensive subjects were divided into three groups according to the severity of disease: 14 with active rheumatoid arthritis, 12 with controlled rheumatoid arthritis, and 12 healthy control subjects. The AT(1)R antagonist valsartan (160 mg) was given to all the subjects, and blood samples were taken for pharmacokinetic analysis. The systolic, diastolic, and mean arterial pressures were determined at all blood collection times. The degree of inflammation was measured using joint swelling, NO, and CRP. Plasma valsartan concentration was measured using high-performance liquid chromatography (HPLC). Patients with active disease had significantly higher joint swelling, NO, and CRP than other groups. Plasma valsartan concentration-time curves were remarkably similar in all groups. No reduced response was noticed. Our preliminary observation suggests a need for further studies to examine the possibility of AT(1)R antagonists as alternatives to other cardiovascular drugs so that their potency may be reduced by inflammation.

Effects of ACE gene insertion/deletion polymorphism on response to spironolactone in patients with chronic heart failure

BACKGROUND

Angiotensin-converting enzyme (ACE) is involved in the pathophysiology of chronic heart failure, and its activity is determined in part by a polymorphism of the ACE gene. We hypothesized that the benefits of spironolactone, which inhibits downstream elements of ACE-mediated abnormalities, may depend on ACE genotype.

METHODS

We randomly assigned 93 chronic heart failure patients to treatment with spironolactone (n = 47) or to a control group (n = 46) and followed them for 12 months. Genotype for the insertion/deletion polymorphism of the ACE gene was determined by polymerase chain reaction. An echocardiographic examination was performed at baseline and at the end of the 12 months.

RESULTS

The mean (+/- SD) age of the 93 patients was 62 +/- 9 years, and the mean New York Heart Association class was 2 +/- 1. The genotype was DD in 26 patients (28%). Forty-seven patients were assigned to spironolactone treatment (mean dose, 32 +/- 16 mg). In the treated group, only patients with a non-DD genotype showed significant improvement in left ventricular ejection fraction (3.0%; 95% confidence interval [CI]: 1.2% to 4.8%; P = 0.002), end-systolic volume (-23 mL; 95% CI: -36 to -11; P = 0.0005), and end-diastolic volume (-27 mL; 95% CI: -43 to -12; P = 0.001). In the multivariate analysis, the estimated net effect of treatment was 29 mL better (95% CI: -20 to 78 mL) for end-diastolic volume, 20 mL better (95% CI: -18 to 58 mL) for end-systolic volume, but 1.4% worse (95% CI: -3.4% to 6.2%) for left ventricular ejection fraction in patients with non-DD versus DD genotypes.

CONCLUSION

The effects of spironolactone treatment on left ventricular systolic function and remodeling may in part depend on ACE genotype.

Vascular injury in systemic sclerosis: Angiotensin-converting enzyme insertion/deletion polymorphism

The microvascular involvement in systemic sclerosis (SSc) is characterized by endothelial damage and smooth muscle cell migration in the intima. The vascular pathologic modifications in SSc are strikingly similar to those of atherosclerosis. SSc also is characterized by an accelerated macrovascular disease. The gene encoding for angiotensin-converting enzyme (ACE) is a 21-kb, 26-exon gene, localized on chromosome 17 (17q23). Polymorphic sites are an insertion/deletion (I/D) that consists of three genotypes: DD and II homozygotes, and ID heterozygote. ACE gene polymorphisms have been linked to vascular disorders (coronary artery disease, hypertension, cerebrovascular disease, hypertrophic cardiomyopathy, and diabetic or nondiabetic nephropathy). In particular, the possession of ACE D allele was associated with an increased risk of developing malignant vascular injury. ACE D allele frequency of the I/D polymorphism was associated with an increased risk of SSc, suggesting a genetic contribution to the disease. The discrepancy between the high prevalence of D allele and reduced ACE plasma levels in SSc demonstrate the lack of knowledge on the regulation and function of renin-angiotensin system in SSc.

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.

Angiotensin-converting enzyme-gene polymorphism is associated with collagen I synthesis and QT dispersion in essential hypertension

AIM

This study tested the hypothesis that abnormal QT dispersion, an indicator of arrhythmogenic risk, is associated with angiotensin-converting enzyme (ACE) gene polymorphism and abnormalities of collagen metabolism.

METHODS

A total of 132 patients with untreated essential hypertension (EHT) were recruited. QT dispersion corrected by heart rate (QTc) on a 12-lead electrocardiogram, ACE genotype, left ventricular mass index (LVMI) and E/A ratio using echocardiogram, plasma ACE activity and serum propeptide type I C-terminal procollagen (PICP) concentration, a marker of myocardial fibrosis, were determined. A normal control group (NC) of 200 normotensive subjects was used for comparison of QT dispersion.

RESULTS

Number of EHT patients with ACE genotype I/I, I/D and D/D was 61, 52 and 19, respectively. LVMI and E/A ratio were similar in the three groups. Compared with subjects with I/I or I/D genotype, subjects with D/D showed higher plasma ACE activity (I/I: 13 +/- 0.6, I/D: 17 +/- 0.9, and D/D: 21 +/- 1.1 nmol/min per ml, mean +/- SE, P05) and serum PICP concentration (I/I: 106 +/- 5.4, I/D: 106 +/- 4.9, D/D: 140 +/- 12.1 ng/ml, P < 0.01). QTc dispersion was larger in the three hypertensive subgroups than in NC, and was the largest in EHT with D/D (NC: 0.037 +/- 0.001, I/I: 0.056 +/- 0.003, I/D: 0.055 +/- 0.002, D/D: 0.069 +/- 0.004 s, P < 0.05).

CONCLUSION

ACE D/D genotype could be associated with an elevation of serum PICP concentration possibly leading to myocardial fibrosis and increased QT dispersion.

Pharmacogenomics of drugs affecting the cardiovascular system

The variability in drug response originates partly from genetics, with possible consequences for drug efficacy, adverse effects, and toxicity. Until now, pharmacogenetics mainly indicated the best known source of variability, that is, the variability caused by drug metabolism. However, simultaneous progress in the knowledge of biochemical targets of drugs and of the human genome, together with the development of new technologies, revealed many new sources of human genetic variation, e.g., in receptors or transporters. Drugs are metabolized by various polymorphic phase I enzymes, including cytochromes P450 (CYP). Among them, the most relevant for the metabolism of cardiovascular drugs are CYP3A4, CYP2C9 or CYP2C19, and CYP2D6. The role of phase II enzymes is limited with regard to cardiovascular drugs biotransformation, but some polymorphisms (glutathion-S-transferase; GSH-T) are linked to cardiovascular risk. Phase III proteins or transporters, especially from the ABC family, must also be considered, as their polymorphisms affect cholesterol and other sterols transport. Among pharmacological targets, some proteins were identified as involved in interindividual variations in the response to cardiovascular drugs. Some examples are apolipoprotein E, angiotensin-converting enzyme, and the beta-adrenergic receptor. From the risk concept emphasizing impaired metabolism and adverse effects, we now moved to an approach, which is a personalized, genotype-dependent adaptation of therapy.

Implications of pharmacogenetics for individualizing drug treatment and for study design

Adverse drug reactions and ineffective drug treatment are responsible for a large health care burden. Considerable variability in drug response makes the prediction of the individual reaction difficult. Pharmacogenetics can help to individualize drug treatment in accordance with the genetic make-up of the patient. Drug response is best understood as a complex interplay between pharmacokinetics, pharmacodynamics, and other disease-associated factors. There are a large number of genetic variants in the enzymes of phase I and phase II drug metabolism, in drug transporters, and drug targets, all of which account for differences in drug response. The polymorphisms in the cytochrome P450 enzyme system have been investigated most extensively. Genotype-based dose adjustment which should ensure "bioequivalent" drug concentrations in all patients has been derived from pharmacokinetic parameters, but this approach will have to be verified in prospective studies. Drug transport has recently been recognized as a further crucial determinant in pharmacokinetics. The effect of genetics on disease susceptibility and drug treatment has been studied quite extensively; however, hardly any of this progress is at present reflected in routine health care. The integration of pharmacogenetic factors in clinical trials requires novel considerations for study design and data interpretation. It is to be hoped that the new science bioinformatics will (a) help us identify the contribution of genetics to disease and treatment response and will (b) create data-processing devices which help the physician in the face of the enormously expanding scientific knowledge in selecting the best individually adapted treatment for the patient.

Gender, ethnicity and genetics in cardiovascular disease: part 1: Basic principles

Prior to 1993, most drug efficacy and safety trials were conducted in white males, although gender and racial differences in pharmacodynamics and pharmacokinetics have been documented since the early 1900s. Over the last 2 decades, supported by the FDA and legislation, attempts to include more women and minorities in clinical drug trials have been made, with limited success. Yet, there are important differences in pathophysiology and pharmacogenetics, as well as pharmacotherapeutic effectiveness. This is the first of 2 articles that review the basic scientific principles of such differences. In particular, genetic polymorphisms of cardiovascular candidate genes and drug metabolism are described. The pharmacodynamic and pharmacokinetic variations among genders and ethnicities are summarized.

Correlation of Angiotensin-converting enzyme gene polymorphism with effect of antihypertensive therapy by Angiotensin-converting enzyme inhibitor

BACKGROUND

The correlation of the angiotensin-converting enzyme insertion/deletion polymorphism with essential hypertension shown in previous studies is controversial, and the responses of hypertensive patients with different angiotensin-converting enzyme genotypes to treatment with an angiotensin-converting enzyme inhibitor merits investigation.

METHODS

Eighty-nine patients with essential hypertension and 102 normotensive subjects were included in this study. All subjects were genotyped by polymerase chain reaction for the insertion/deletion polymorphism of the angiotensin-converting enzyme gene. Blood pressure was measured before and after taking Benazepril 10 mg, once daily, for 2 months.

RESULTS

The genotype and allele frequencies were similar (chi(2) = 0.64, P =.73; chi(2) = 0.36, P =.55, respectively). The reduction of both systolic and diastolic blood pressure in the DD genotype was significantly greater than in the II genotype (10.13 +/- 4.91 vs 5.37 +/- 2.79, P <.01; 7.47 +/- 3.50 vs 4.71 +/- 2.40, P <.05, respectively).

CONCLUSIONS

No significant association of angiotensin-converting enzyme gene polymorphism with essential hypertension was found. Angiotensin-converting enzyme gene polymorphism might be related to the antihypertensive response to an angiotensin-converting enzyme inhibitor in hypertensive patients.

Angiotensin converting enzyme DD genotype is associated with hypertensive crisis

OBJECTIVE

The genetic background of hypertensive crisis is unknown. We examined the association of polymorphisms in genes involved in the renin-angiotensin-aldosterone-system with hypertensive crisis.

DESIGN

Population-based case-control study.

SETTING

Emergency department at a tertiary care university hospital.

PATIENTS

A total of 182 patients with essential hypertension who were admitted to an emergency department for treatment of hypertensive crisis and 182 age- and sex-matched healthy individuals.

INTERVENTIONS

None.

MEASUREMENTS

Analysis of polymorphisms in genes coding for angiotensinogen (AJT 704T-->C), angiotensin II receptor 1 (AGTR1 1166A-->C), renin (REN 2646G-->A), renin-binding protein (RENBP 61T-->C), alpha-adducin (ADD1 1378G-->T), beta-2-adrenergic receptor (ADRB2 46A-->G, 79C-->G), and angiotensin I converting enzyme (ACE I/D) was performed by polymerase chain reaction and restriction fragment length polymorphism analysis. MAIN RESULTS Among patients, the ACE I/D polymorphism showed a deviation from Hardy-Weinberg equilibrium (p =.01). In controls, all polymorphisms were in the Hardy-Weinberg equilibrium. The frequency of the DD genotype was increased in patients (n = 70, 38.5%) vs. controls (n = 51; 28.0%;p =.03; odds ratio, 1.61; 95% confidence interval, 1.03-2.50), which was due to the DD genotype in 40 male patients (44%) vs. 23 in male controls (25.3%;p =.004; odds ratio, 3.48; 95% confidence interval, 1.47-8.30). There were no differences in genotype distributions among other polymorphisms.

CONCLUSION

We demonstrate a possible association of the DD genotype with hypertensive crisis in men.

Pharmacogenomics in cardiovascular diseases

Considerable heterogeneity exists in the way individuals respond to medications, in terms of both efficacy and safety. Inherited differences in the absorption, metabolism, excretion, and target for drug therapy have important effects on drug efficacy and safety. Pharmacogenomics aims to discover new therapeutic targets and understand genetic polymorphisms that determine the safety and efficacy of medications. The goal of pharmaco-genomics is customization of drug therapy with administration of a medication in an optimum dose that will be safe and effective with reduction in morbidity and mortality.

Enhanced responses of blood pressure, renal function, and aldosterone to angiotensin I in the DD genotype are blunted by low sodium intake

Angiotensin-converting enzyme (ACE) activity is increased in the DD genotype, but the functional significance for renal function is unknown. Blunted responses of BP and proteinuria to ACE inhibition among DD renal patients during periods of high sodium intake were reported. It was therefore hypothesized that sodium status affects the phenotype in the ACE I/D polymorphism. The effects of angiotensin I (AngI) and AngII among 27 healthy subjects, with both low (50 mmol sodium/d) and liberal (200 mmol sodium/d) sodium intakes, were studied. Baseline mean arterial pressure (MAP) values, renal hemodynamic parameters, and renin-angiotensin system parameters were similar for all genotypes with either sodium intake level. With liberal sodium intake, the increases in MAP, renal vascular resistance, and aldosterone levels during AngI infusion (8 ng/kg per min) were significantly higher for the DD genotype, compared with the ID and II genotypes (all parameters presented as percent changes +/- 95% confidence intervals), with mean MAP increases of 22 +/- 2% (DD genotype), 13 +/- 5% (ID genotype), and 12 +/- 6% (II genotype) (P < 0.05), mean increases in renal vascular resistance of 100.1 +/- 19.7% (DD genotype), 73.0 +/- 16.3% (ID genotype), and 63.2 +/- 16.9% (II genotype) (P < 0.05), and increases in aldosterone levels of 650 +/- 189% (DD genotype), 343 +/- 71% (ID genotype), and 254 +/- 99% (II genotype) (P < 0.05). Also, the decrease in GFR was more pronounced for the DD genotype, with mean decreases of 17.9 +/- 4.7% (DD genotype), 8.8 +/- 3.4% (ID genotype), and 6.4 +/- 5.9% (II genotype) (P < 0.05). The effective renal plasma flow, plasma AngII concentration, and plasma renin activity values were similar for the genotypes. In contrast, with low sodium intake, the responses to AngI were similar for all genotypes. The responses to AngII were also similar for all genotypes, with either sodium intake level. In conclusion, the responses of MAP, renal hemodynamic parameters, and aldosterone concentrations to AngI are enhanced for the DD genotype with liberal but not low sodium intake. These results support the presence of gene-environment interactions between ACE genotypes and dietary sodium intake.