Renin-angiotensin system gene polymorphisms: potential mechanisms for their association with cardiovascular diseases

G protein-coupled receptor (GPCR) pharmacogenomics

The field of pharmacogenetics, the investigation of the influence of one or more sequence variants on drug response phenotypes, is a special case of pharmacogenomics, a discipline that takes a genome-wide approach. Massively parallel, next generation sequencing (NGS), has allowed pharmacogenetics to be subsumed by pharmacogenomics with respect to the identification of variants associated with responders and non-responders, optimal drug response, and adverse drug reactions. A plethora of rare and common naturally-occurring GPCR variants must be considered in the context of signals from across the genome. Many fundamentals of pharmacogenetics were established for G protein-coupled receptor (GPCR) genes because they are primary targets for a large number of therapeutic drugs. Functional studies, demonstrating likely-pathogenic and pathogenic GPCR variants, have been integral to establishing models used for in silico analysis. Variants in GPCR genes include both coding and non-coding single nucleotide variants and insertion or deletions (indels) that affect cell surface expression (trafficking, dimerization, and desensitization/downregulation), ligand binding and G protein coupling, and variants that result in alternate splicing encoding isoforms/variable expression. As the breadth of data on the GPCR genome increases, we may expect an increase in the use of drug labels that note variants that significantly impact the clinical use of GPCR-targeting agents. We discuss the implications of GPCR pharmacogenomic data derived from the genomes available from individuals who have been well-phenotyped for receptor structure and function and receptor-ligand interactions, and the potential benefits to patients of optimized drug selection. Examples discussed include the renin-angiotensin system in SARS-CoV-2 (COVID-19) infection, the probable role of chemokine receptors in the cytokine storm, and potential protease activating receptor (PAR) interventions. Resources dedicated to GPCRs, including publicly available computational tools, are also discussed.

Association between ACE I/D genetic polymorphism and the severity of coronary artery disease in Vietnamese patients with acute myocardial infarction

Background

The severity of coronary artery disease is a prognostic factor for major adverse cardiovascular events in patients diagnosed with acute myocardial infarction. ACE I/D polymorphism is one of the genetic factors that may affect the severity of coronary artery disease. This study aimed to investigate the association between ACE I/D genotypes and the severity of coronary artery disease in patients with acute myocardial infarction.

Materials and methods

A single-center, prospective, observational study was conducted at the Department of Cardiology and Department of Interventional Cardiology, Cho Ray Hospital, Ho Chi Minh City, Vietnam from January 2020 to June 2021. All participants diagnosed with acute myocardial infarction underwent contrast-enhanced coronary angiography. The severity of coronary artery disease was determined by Gensini score. ACE I/D genotypes were identified in all subjects by using the polymerase chain reaction method.

Results

A total of 522 patients diagnosed with first acute myocardial infarction were recruited. The patients' median Gensini score was 34.3. The II, ID, and DD genotype rates of ACE I/D polymorphism were 48.9%, 36.4%, and 14.7%, respectively. After adjusting for confounding factors, multivariable linear regression analysis showed that the ACE DD genotype was independently associated with a higher Gensini score compared with the II or ID genotypes.

Conclusion

The DD genotype of the ACE I/D polymorphism was associated with the severity of coronary artery disease in Vietnamese patients diagnosed with first acute myocardial infarction.

Angiotensinogen Suppression: A New Tool to Treat Cardiovascular and Renal Disease

Multiple types of renin-angiotensin system (RAS) blockers exist, allowing interference with the system at the level of renin, angiotensin-converting enzyme, or the angiotensin II receptor. Yet, in particular, for the treatment of hypertension, the number of patients with uncontrolled hypertension continues to rise, either due to patient noncompliance or because of the significant renin rises that may, at least partially, overcome the effect of RAS blockade (RAS escape). New approaches to target the RAS are either direct antisense oligonucleotides that inhibit angiotensinogen RNA translation, or small interfering RNA (siRNA) that function via the RNA interference pathway. Since all angiotensins stem from angiotensinogen, lowering angiotensinogen has the potential to circumvent the RAS escape phenomenon. Moreover, antisense oligonucleotides and small interfering RNA require injections only every few weeks to months, which might reduce noncompliance. Of course, angiotensinogen suppression also poses a threat in situations where the RAS is acutely needed, for instance in women becoming pregnant during treatment, or in cases of emergency, when severe hypotension occurs. This review discusses all preclinical data on angiotensinogen suppression, as well as the limited clinical data that are currently available. It concludes that it is an exciting new tool to target the RAS with high specificity and a low side effect profile. Its long-term action might revolutionize pharmacotherapy, as it could overcome compliance problems. Preclinical and clinical programs are now carefully investigating its efficacy and safety profile, allowing an optimal introduction as a novel drug to treat cardiovascular and renal diseases in due time.

Familial Analysis of Epistatic and Sex-Dependent Association of Genes of the Renin-Angiotensin-Aldosterone System and Blood Pressure

BACKGROUND

Renin-angiotensin-aldosterone system genes have been inconsistently associated with blood pressure, possibly because of unrecognized influences of sex-dependent genetic effects or gene-gene interactions (epistasis).

METHODS AND RESULTS

We tested association of systolic blood pressure with single-nucleotide polymorphisms (SNPs) at renin (REN), angiotensinogen (AGT), angiotensin-converting enzyme (ACE), angiotensin II type 1 receptor (AGTR1), and aldosterone synthase (CYP11B2), including sex-SNP or SNP-SNP interactions. Eighty-eight tagSNPs were tested in 2872 white individuals in 809 pedigrees from the Victorian Family Heart Study using variance components models. Three SNPs (rs8075924 and rs4277404 at ACE and rs12721297 at AGTR1) were individually associated with lower systolic blood pressure with significant (P<0.00076) effect sizes ≈1.7 to 2.5 mm Hg. Sex-specific associations were seen for 3 SNPs in men (rs2468523 and rs2478544 at AGT and rs11658531 at ACE) and 1 SNP in women (rs12451328 at ACE). SNP-SNP interaction was suggested (P<0.005) for 14 SNP pairs, none of which had shown individual association with systolic blood pressure. Four SNP pairs were at the same gene (2 for REN, 1 for AGT, and 1 for AGTR1). The SNP rs3097 at CYP11B2 was represented in 5 separate pairs.

CONCLUSIONS

SNPs at key renin-angiotensin-aldosterone system genes associate with systolic blood pressure individually in both sexes, individually in one sex only and only when combined with another SNP. Analyses that incorporate sex-dependent and epistatic effects could reconcile past inconsistencies and account for some of the missing heritability of blood pressure and are generally relevant to SNP association studies for any phenotype.

A positive association between the human tissue kallikerin gene A2233C polymorphism and blood pressure response to benazepril

BACKGROUND

It is generally believed that essential hypertension is influenced by both genetic and environmental factors, as well as their interactions. Tissue kallikrein encoded by the tissue kallikrein gene (KLK1) is a key serine proteinase of kallikrein-kinin system, which is capable of generating potent vasactive peptides, kinins, by selective cleavage of the kininogen substrate. It was reported that the A2233 → C polymorphism in KLK1 gene is associated with essential hypertension. The aim of this study was to examine whether the molecular variations of KLK1 play role in determining the therapeutic response to benazepril, an ACE inhibitor.

METHODS

A total of 331 hypertensive individuals were recruited and treated with benazepril for 15 days. A variant impact of KLK1 A2233C was revealed. Chi-square analysis showed that the hypertensive subjects with the mutation genotype (AC + CC) had a higher proportion in systolic blood pressure (SBP, 88.1% vs. 79.0%, χ² = 4.141, p = 0.042) and diastolic blood pressure (DBP, 91.1% vs. 79.2%, χ² = 9.336, p = 0.002), respectively, to benazepril medication in good responders than in poor responders. Logistic regression analysis indicated that the hypertensive subjects with AC + CC genotype were more sensitive to the benazepril therapy in SBP (OR=1.97, 95% CI: 1.02-3.80, p = 0.044) and DBP (OR = 1.91, 95% CI: 2.69-5.16, p = 0.003), as compared with those hypertensive subjects with AA genotype.

CONCLUSION

Our findings suggest that the A2233C polymorphism of KLK1 may be a marker of evaluation of hypertensive subjects' responses to angiotensin I converting enzyme inhibitors benazepril.

Epistatic interaction between common AGT G(-6)A (rs5051) and AGTR1 A1166C (rs5186) variants contributes to variation in kidney size at birth

Low nephron number has been recognised as an important cardiovascular risk factor and recently a strong correlation between renal mass and nephron number has been demonstrated in newborns. The aim of this study was to investigate individual, as well as combined, effects of common variants of genes which encode for major components of the renin-angiotensin system (REN G10601A, AGT G(-6)A, ACE I/D, AGTR1 A1166C) on kidney size in healthy, full-term newborns. A significant additive main effect of the ACE I/D polymorphism, as well as an additive-by-additive interaction between AGT G(-6)A and AGTR1 A1166C variants, were found. The variance attributed to the epistatic effect was 27.9 ml(2)/m(4), which accounted for 73.8% of the interaction variance (37.8 ml(2)/m(4)), 66.4% of the genetic variance (42.0 ml(2)/m(4)) and 4.4% to the total phenotypic variance (628 ml(2)/m(4)). No other statistically significant main or epistatic effects were detected. Our results highlight the importance of considering gene-gene interactions as part of the genetic architecture of congenital nephron number, even when the loci do not show significant single locus effects. Unravelling the genetic determinants of low nephron number, along with early molecular screening, may well help to identify children at risk for cardiovascular disease.

Neuromarkers of the common angiotensinogen polymorphism in healthy older adults: A comprehensive assessment of white matter integrity and cognition

The common angiotensinogen (AGT) M268T polymorphism (rs699; historically referred to as M235T) has been identified as a significant risk factor for cerebrovascular pathologies, yet it is unclear if healthy older adults carrying the threonine amino acid variant have a greater risk for white matter damage in specific fiber tracts. Further, the impact of the threonine variant on cognitive function remains unknown. The present study utilized multiple indices of diffusion tensor imaging (DTI) and neuropsychological assessment to examine the integrity of specific white matter tracts and cognition between individuals with homozygous genotypes of M268T (MetMet n=27, ThrThr n=27). Differences in subcortical hyperintensity (SH) volume were also examined between groups. Results indicated that the threonine variant was associated with significantly reduced integrity in the superior longitudinal fasciculus (SLF) and the cingulate gyrus segment of the cingulum bundle (cingulum CG) compared to those with the methionine variant, and poorer cognitive performance on tests of attention/processing speed and language. Despite these associations, integrity of these tracts did not significantly mediate relationships between cognition and genetic status, and SH did not differ significantly between groups. Collectively our results suggest that the threonine variant of M268T is a significant risk factor for abnormalities in specific white matter tracts and cognitive domains in healthy older adults, independent of SH burden.

Biomarkers of activation of renin-angiotensin-aldosterone system in heart failure: how useful, how feasible?

Renin-angiotensin-aldosterone system (RAAS), participated by kidney, liver, vascular endothelium, and adrenal cortex, and counter-regulated by cardiac endocrine function, is a complex endocrine system regulating systemic functions, such as body salt and water homeostasis and vasomotion, in order to allow the accomplishment of physiological tasks, such as orthostasis, physical and emotional stimuli, and to react towards the hemorrhagic insult, in tight conjunction with other neurohormonal axes, namely the sympathetic nervous system, the endothelin and vasopressin systems. The systemic as well as the tissue RAAS are also dedicated to promote tissue remodeling, particularly relevant after damage, when chronic activation may configure as a maladaptive response, leading to fibrosis, hypertrophy and apoptosis, and organ dysfunction. RAAS activation is a fingerprint of systemic arterial hypertension, kidney dysfunction, vascular atherosclerotic disease, and is definitely an hallmark of heart failure, which rapidly shifts from organ disease to a disorder of neurohormonal regulatory systems. Chronic RAAS activation is an indirect or direct target of most effective pharmacological treatments in heart failure, such as beta-blockers, inhibitors of angiotensin converting enzyme, angiotensin receptor blockers, direct renin inhibitors, and mineralocorticoid receptor blockers. Biomarkers of RAAS activation are available, with different feasibility and accuracy, such as plasma renin activity, renin, angiotensin II, and aldosterone, which all accompany the increasing clinical severity of heart failure disease, and are well recognized prognostic factors, even in patients with optimal therapy. Polymorphisms influencing the expression and activity of RAAS pathways have been recognized as clinically relevant biomarkers, likely influencing either the individual clinical phenotype, or the response to drugs. This solid, growing evidence strongly suggests the rationale for the use of biomarkers of the RAAS activation, as a guide to tailor individual therapy in the current practice, and their implementation as a rule-in marker for future trials on novel drugs in the heart failure setting.

Pharmacogenetics of the G protein-coupled receptors

Pharmacogenetics investigates the influence of genetic variants on physiological phenotypes related to drug response and disease, while pharmacogenomics takes a genome-wide approach to advancing this knowledge. Both play an important role in identifying responders and nonresponders to medication, avoiding adverse drug reactions, and optimizing drug dose for the individual. G protein-coupled receptors (GPCRs) are the primary target of therapeutic drugs and have been the focus of these studies. With the advance of genomic technologies, there has been a substantial increase in the inventory of naturally occurring rare and common GPCR variants. These variants include single-nucleotide polymorphisms and insertion or deletions that have potential to alter GPCR expression of function. In vivo and in vitro studies have determined functional roles for many GPCR variants, but genetic association studies that define the physiological impact of the majority of these common variants are still limited. Despite the breadth of pharmacogenetic data available, GPCR variants have not been included in drug labeling and are only occasionally considered in optimizing clinical use of GPCR-targeted agents. In this chapter, pharmacogenetic and genomic studies on GPCR variants are reviewed with respect to a subset of GPCR systems, including the adrenergic, calcium sensing, cysteinyl leukotriene, cannabinoid CB1 and CB2 receptors, and the de-orphanized receptors such as GPR55. The nature of the disruption to receptor function is discussed with respect to regulation of gene expression, expression on the cell surface (affected by receptor trafficking, dimerization, desensitization/downregulation), or perturbation of receptor function (altered ligand binding, G protein coupling, constitutive activity). The large body of experimental data generated on structure and function relationships and receptor-ligand interactions are being harnessed for the in silico functional prediction of naturally occurring GPCR variants. We provide information on online resources dedicated to GPCRs and present applications of publically available computational tools for pharmacogenetic studies of GPCRs. As the breadth of GPCR pharmacogenomic data becomes clearer, the opportunity for routine assessment of GPCR variants to predict disease risk, drug response, and potential adverse drug effects will become possible.

Angiotensin II type 1 receptor A1166C gene polymorphism and essential hypertension in Calabar and Uyo cities, Nigeria

OBJECTIVES:

The angiotensin II protein is a vasoconstrictor that exerts most of its influence through the angiotensin II type 1 receptor (AT₁R). Inconsistent association between the A1166C polymorphism of the AT₁R gene and hypertension has been reported among various populations but not among the peoples of Calabar and Uyo. This study was designed to determine the frequency of the A1166C polymorphism of the AT₁R gene and its association with hypertension in a sample population of Calabar and Uyo.

MATERIALS AND METHODS:

A population-based case control design consisting of total of 1224 participants, 612 each of patients and controls were randomly recruited from hypertension clinics and the general population. Genotyping of the A1166C allele of the AT₁R gene to identify variants was performed using polymerase chain reaction and restriction enzyme digestion. Multiple regressions were applied to test whether the A1166 genotypes were predictors of hypertension.

RESULTS:

99% of the study population had the wild type AA genotype, and 1% was AC heterozygous carriers of the A1166C polymorphism.

CONCLUSION:

The A1166C polymorphism was not a predictor of hypertension in the sample population of Calabar and Uyo.

Genetic influences of angiotensin-converting enzyme inhibitor response: an opportunity for personalizing therapy?

The angiotensin-converting enzyme (ACE) inhibitors are a cornerstone drug therapy in the current treatment of patients with hypertension, stable coronary artery disease and heart failure. Individualizing therapy of ACE inhibitors with clinical risk factors in low-risk patients with stable coronary artery disease is not feasible. The concept of pharmacogenetics, by studying patient factors more individually, offers a first glimpse in the quest for the 'holy grail' of personalized medicine. As such, genetic targets in the direct pharmacodynamic pathway of ACE inhibitors, the renin-angiotensin-aldosterone system, is a plausible candidate for such an approach. In the past few decades, results of pharmacogenetic studies were scarce and inconsistent. However, recently the first reports of larger pharmacogenetic studies are now confirming that the 'pharmacogenetic approach' might be feasible in the future. The current review focuses on the recent developments in pharmacogenetic research in response to ACE inhibitors in patients with stable coronary artery disease.

Individualised therapy of angiotensin converting enzyme (ACE) inhibitors in stable coronary artery disease: overview of the primary results of the PERindopril GENEtic association (PERGENE) study

In patients with stable coronary artery disease (CAD) without overt heart failure, ACE inhibitors are among the most commonly used drugs as these agents have been proven effective in reducing the risk of cardiovascular events. Considerable individual variations in the blood pressure response to ACE inhibitors are observed and as such heterogeneity in clinical treatment effect would be likely as well. Assessing the consistency of treatment benefit is essential for the rational and cost-effective prescription of ACE inhibitors. Information on heterogeneities in treatment effect between subgroups of patients could be used to develop an evidence-based guidance for the installation of ACE-inhibitor therapy. Obviously, therapy should only be applied in those patients who most likely will benefit. Attempts to develop such treatment guidance by using clinical characteristics have been unsuccessful. No heterogeneity in risk reduction by ACE inhibitors has been observed in relation to relevant clinical characteristics. A new approach to such 'guided-therapy' could be to integrate more patient-specific characteristics such as the patients' genetic information. If proven feasible, pharmacogenetic profiling could optimise patients' benefit of treatment and reduce unnecessary treatment of patients. Cardiovascular pharmacogenetic research of ACE inhibitors in coronary artery disease patients is in a formative stage and studies are limited. The PERGENE study is a large pharmacogenetic substudy of the EUROPA trial, aimed to assess the achievability of pharmacogenetic profiling. We provide an overview of the main results of the PERGENE study in terms of the genetic determinants of treatment benefit and blood pressure response. The main results of the PERGENE study show a pharmacogenetic profile related to the treatment benefit of perindopril identifying responders and non-responders to treatment.

Association between polymorphisms of the renin angiotensin system and carotid stenosis

OBJECTIVE

Carotid stenosis is a common manifestation of systemic atherosclerosis. Apart from traditional risk factors, genetic determinants, such as polymorphisms of the renin angiotensin system (RAS), may be relevant in modulating the atherosclerotic process leading to carotid stenosis. In this study, we investigated the role of angiotensin-converting enzyme (ACE) I/D and -240A>T, angiotensinogen (AGT) M235T, and angiotensin type 1 receptor (AGTR1) 1166A > C polymorphisms in modulating the susceptibility to the disease.

METHODS

Eight hundred twenty-one consecutive patients with severe carotid stenosis (≥70%) and 847 control subjects were investigated.

RESULTS

A significant difference in genotype distribution (P < .0001) and allele frequency (P < .0001) between patients and controls for the ACE I/D polymorphism, but not for the other single-nucleotide polymorphisms investigated, was observed. The ACE D allele frequency was significantly higher in patients without traditional risk factors in comparison with that observed in those with at least one risk factor (0.71 vs 0.61; P = .04). The ACE D allele significantly influenced carotid stenosis under dominant, recessive, and additive model of inheritance at both univariate (P < .0001) and multivariate analysis (P < .0001). When the combined effect of RAS unfavorable alleles was considered, patients carrying less than three alleles had a lower risk of carotid stenosis (odds ratio [OR], 0.79 [0.63-0.99]; P = .05), while carriers of more than four unfavorable alleles had an increased risk (OR, 1.44 [1.12-1.84]; P = .004), in comparison with subjects carrying three or four unfavorable alleles. ACE D allele frequency was similar in patients with and without additional atherosclerotic localizations (0.61 vs 0.62, respectively).

CONCLUSIONS

Our findings evidence a role for ACE I/D polymorphism in influencing the susceptibility to carotid stenosis, even in the absence of traditional risk factors. Interestingly, our findings provided further information concerning the role of this polymorphism in modulating the atherosclerotic process apart from its different localizations.

Tagging SNPs in REN, AGTR1 and AGTR2 genes and response of renin activity, angiotensin II and aldosterone concentrations to antihypertensive treatment in Kazakans

HYPOTHESIS

Polymorphisms of REN, AGTR1 and AGTR2 may be associated with responses of renin-angiotensin-aldosterone system (RAAS) activity phenotypes to angiotensin-converting enzyme inhibitor (ACEI) antihypertensive treatment.

MATERIALS AND METHODS

A total of 400 first diagnosed Kazak hypertensives were randomly allocated to two groups and received a 3-week course of either captopril and atenolol as monotherapy under double blinding. Genotype-phenotype association analyses were performed by covariance analyses between baseline level and responses of blood pressure, renin, angiotensin II and aldosterone concentrations with tagging single nucleotide polymorphisms (SNPs) in REN, AGTR1 and AGTR2 genes. A false discovery rate method was used to adjust multiple testing.

RESULTS

After adjustment for multiple testing, we found that the G allele of rs6676670 (T/G) in intron 1 of REN was significantly associated with higher baseline aldosterone concentrations (p < 0.0001, explained variance (EV) = 2.3%). Significant associations after adjustments were also found between the A allele of rs2887284, with higher baseline renin activity (p = 0.022, EV = 1.0%), higher responses of renin (p = 0.018 EV = 5.4%), and higher responses of angiotensin II (p = 0.0255, EV = 3.13%) to the treatment of ACEI. The carriers of the A allele of rs2887284 appeared to be more sensitive to the ACEI treatment.

CONCLUSION

rs2887284 in intron 9 of REN is associated with the response of renin and angiotensin II levels to ACEI treatment.

The association of hypertension with renin-angiotensin system gene polymorphisms in the Lebanese population

AIM

The study objective was to examine the association of hypertension in the Lebanese population with three renin-angiotensin system gene polymorphisms (RAS): angiotensin-converting enzyme (ACE), angiotensinogen (AGT) and angiotensin-receptor type 1 (AT1R).

METHODS

A total of 270 subjects (124 hypertensive vs 146 normotensive) were genotyped for ACE insertion (I)/deletion (D), AGT (M235T), and AT(1)R (A1166C) gene polymorphisms by polymerase chain reaction and restriction fragment length polymorphism.

RESULTS

The studied genes showed no deviation from Hardy-Weinberg equilibrium. No association could be reported with the ACE I/D polymorphism, although the D allele frequency was high (77%) in patients. AGT TT genotype prevalence was found to be lower in hypertensive versus normotensive subjects (p<0.0001). AT(1)R CC and AC genotypes were significantly more frequent in hypertensive than normotensive subjects (p<0.0001).

CONCLUSION

The first conducted study on the RAS gene polymorphisms in Lebanese hypertensive patients demonstrated a possible association of the AGT T and AT(1)R C alleles with hypertension.

Gene variation in resistant hypertension: multilocus analysis of the angiotensin 1-converting enzyme, angiotensinogen, and endothelial nitric oxide synthase genes

Resistant hypertension, a complex multifactorial hypertensive disease, is triggered by genetic and environmental factors and involves multiple physiological pathways. Single genetic variants may not reveal significant associations with resistant hypertension because their effects may be dependent on gene-gene or gene-environment interactions. We examined the interaction of angiotensin I-converting enzyme (ACE), angiotensinogen (AGT), and endothelial nitric oxide synthase (NOS3) polymorphisms with environmental factors (gender, age, body mass index, glycemia, total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglycerides, estimated glomerular filtration rate, and urinary sodium excretion) in 70 resistant, 80 well-controlled hypertensive patients, and 70 normotensive controls. All subjects were genotyped for ACE insertion/deletion (rs1799752); AGT M235T (rs699), and NOS3 Glu298Asp (rs 1799983). Multifactorial associations were tested using two statistical methods: the traditional parametric method (adjusted logistic regression analysis) and gene-gene and gene-environment interactions evaluated by multifactor dimensionality reduction analyses. While adjusted logistic regression found no significant association between the studied polymorphisms and controlled or resistant hypertension, the multifactor dimensionality reduction analyses showed that carriers of the AGT 235T allele were at increased risk for resistant hypertension, especially if they were older than 50 years. The AGT 235T allele constituted an independent risk factor for resistant hypertension.

Tailored therapy of ACE inhibitors in stable coronary artery disease: pharmacogenetic profiling of treatment benefit

Angiotensin-converting enzyme (ACE) inhibitors are among the most commonly used drugs in stable coronary artery disease as these agents have been proven to be effective for reducing the risk of cardiovascular morbidity and mortality. As with other drugs, individual variation in treatment benefit is likely. Such heterogeneity could be used to target ACE-inhibitor therapy to those patients most likely to benefit from treatment. However, prior attempts to target ACE-inhibitor therapy to those patients who are most likely to benefit of such prophylactic treatment in secondary prevention using clinical characteristics or the level of baseline risk appeared not to be useful. A new approach of 'tailored therapy' could be to integrate more patient-specific characteristics, such as the genetic information of patients. Pharmacogenetic research of ACE inhibitors in coronary artery disease patients is at a formative stage, and studies are limited. The Perindopril Genetic association (PERGENE) study is a large pharmacogenetic substudy of the randomized placebo-controlled European trial On Reduction of Cardiac Events with Perindopril in Patients with Stable Coronary Artery disease (EUROPA) trial, aimed to assess the feasibility of pharmacogenetic profiling of ACE-inhibitor therapy by perindopril. This article summarizes the recent findings of the PERGENE study and pharmacogenetic research of the treatment benefit of perindopril in stable coronary artery disease.

RAS polymorphisms in cancerous and benign breast tissue

Recent information has revealed new roles in the angiogenic processes linked to the rennin-angiotensin system. To date few studies have been done on the association between RAS genes and cancer and the majority focus mainly on angiotensin I-converting enzyme (ACE). For breast cancer there are three reports that include the angiotensin II receptor, subtype 1 (AGTR1), only one for angiotensinogen (AGT) and none for renin gene (REN). In the present study we investigate whether REN (Bgll), AGT (M235T), ACE (A245T, Indel), and AGTR1 (A1166C) are associated with breast cancer. Polymorphisms were analysed by PCR and RFPLs or sequence specific assay in three groups: breast cancer, benign breast disease (BBD) and general population. REN polymorphism shows that homozygous for A allele have an increased risk for BBD. Differences in M235T genotype frequencies were significant with less heterozygous in breast cancer. With different risk values ACE indel was associated with BBD and breast cancer. Association of AGTR1 was observed only in the breast cancer group, where C allele carriers present a reduced risk. Results of this work supports previous observations on the possible involvement of this system in breast cancer but it also suggests a role in benign disease.

Angiotensin-converting enzyme genotype and encephalopathy in Chernobyl cleanup workers

BACKGROUND AND PURPOSE

To identify, using a genetic model, a key role for the renin-angiotensin system (RAS) in the development of dyscirculatory encephalopathy (DE) in Chernobyl cleanup workers (CCW). The insertion/deletion polymorphism of the angiotensin-converting enzyme (ACE) gene denotes a substantial individual variation in RAS activity with the D-allele being associated with higher ACE activity.

METHODS

Ninety-three male, Caucasian CCW were recruited from those under regular review at the All-Russia Centre of Emergency and Radiation Medicine, St. Petersburg. The presence or absence of DE was determined using existing institutional guidelines. ACE genotype was determined using internationally accepted methodologies.

RESULTS

Angiotensin-converting enzyme genotype distribution in 59 subjects with DE was II: 10 (17%), ID: 31 (53%), DD: 18 (30%), D-allele frequency 56.8%. Whereas in those without the condition the distribution was II: 12 (35%), ID: 19 (56%), DD 3 (9%) and D-allele frequency 35.9% (P = 0.02).

CONCLUSIONS

These data are the first to identify an association between the ACE D-allele and DE in CCW. They provide evidence of a significant role for the RAS in the development of DE and suggest that clinical trials of ACE inhibition would be profitable in this group.

G protein-coupled receptor pharmacogenetics

Common G protein-coupled receptor (GPCR) gene variants that encode receptor proteins with a distinct sequence may alter drug efficacy without always resulting in a disease phenotype. GPCR genetic loci harbor numerous variants, such as DNA insertions or deletions and single-nucleotide polymorphisms that alter GPCR expression and function, thereby contributing to interindividual differences in disease susceptibility/progression and drug responses. In this chapter, these pharmacogenetic phenomena are reviewed with respect to a limited sampling of GPCR systems, including the beta(2)-adrenergic receptors, the cysteinyl leukotriene receptors, and the calcium-sensing receptor. In each example, the nature of the disruption to receptor function that results from each variant is discussed with respect to the regulation of gene expression, expression on cell surface (affected by receptor trafficking, dimerization, desensitization/downregulation), or perturbation of receptor function (by altering ligand binding, G protein coupling, and receptor constitutive activity). Despite the breadth of pharmacogenetic knowledge available, assessment for genetic variants is only occasionally applied to drug development projects involving pharmacogenomics or to optimizing the clinical use of GPCR drugs. The continued effort by the basic science of pharmacogenetics may draw the attention of drug discovery projects and clinicians alike to the utility of personalized pharmacogenomics as a means to optimize novel GPCR drug targets.

A1166C polymorphism of the angiotensin AT1 receptor (AT1R) gene alters endothelial response to statin treatment

BACKGROUND

The function of vascular endothelium is influenced by several factors: low-density lipoprotein (LDL) cholesterol, oxidative stress and the reninangiotensin system.

METHODS

We tested the hypothesis that polymorphisms A1166C of the angiotensin AT1 receptor (AT1R) gene, C242T and A640G of the pphox22 gene (p22 phox is an essential component of NADH/NADPH oxidases) and G894T of the endothelial nitric oxide (NO) synthase (eNOS) gene influence endothelial function and its reaction to statin treatment. In 44 patients with coronary artery disease or hypercholesterolemia (not on lipid-lowering treatment), lipid profile and endothelial function (brachial artery flow-mediated dilation, FMD) were measured at baseline and after treatment with statins for 8-12 weeks. All subjects were genotyped for the above-mentioned polymorphisms.

RESULTS

None of the polymorphisms significantly predicted baseline FMD. Patients with the C allele of A1166C showed smaller changes in FMD in comparison with patients with the AA genotype (-0.044+/-0.439% vs. 0.386+/-0.599%; p=0.016). None of the other polymorphisms significantly influenced changes in FMD.

CONCLUSIONS

The C allele of AT1R A1166C is associated with significantly lower endothelial response to statin treatment.

Renin-angiotensin-system gene polymorphisms and depression

Given the abundance of the renin-angiotensin system (RAS) components in the brain, their importance in behavior and cognition, and the data that implicates them in the etiology and treatment of depression, it is possible that those RAS gene polymorphisms associated with increased RAS activity may also be associated with depression. The frequencies of common polymorphisms of genes encoding for components of the RAS, namely angiotensinogen (M235T), angiotensin converting enzyme (ACE) (insertion, I; deletion, D), angiotensin receptor type I (A1166C), and angiotensin receptor type II (C3123A) were determined in DNA extracted from buccal cells from a Lebanese population of 132 depressed patients and their first-degree relative case-controls. The angiotensin receptor type 1 (A1166C) CC genotype was significantly associated with depression (p=0.036). None of the other common RAS-associated polymorphisms were significantly associated. The results support the hypothesis that increased RAS activity may increase relative risk of depression in that the angiotensin receptor type 1 (A1166C) CC genotype is associated with increased responsiveness to angiotensin II.

Synergistic expression of angiotensin-converting enzyme (ACE) and ACE2 in human renal tissue and confounding effects of hypertension on the ACE to ACE2 ratio

Angiotensin-converting enzyme (ACE) 2, a newly emerging component of the renin-angiotensin system, is presumed to be a counterregulator against ACE in generating and degrading angiotensin II. It remains to be elucidated how mRNA levels of these two genes are quantitatively regulated in the kidney and also what kind of clinicopathological characteristics could influence the gene expressions in humans. Seventy-eight cases of biopsy-proven renal conditions were examined in detail. Total RNA from a small part of each renal cortical biopsy specimen was reverse transcribed, and the resultant cDNA was amplified for ACE, ACE2, and glyceraldehyde-3-phosphate dehydrogenase with a real-time PCR system. Then we investigated the relationship between clinicopathological variables and mRNA levels adjusted for glyceraldehyde-3-phosphate dehydrogenase. Statistically significant correlation was not observed between any clinicopathological variables and either of the gene expressions by pairwise comparison. However, a strong correlation was observed between the gene expressions of ACE and those of ACE2. Moreover, the ACE to ACE2 ratio was significantly higher in subjects with hypertension (HT) than that in subjects without HT. Whereas parameters of renal function, e.g. urinary protein excretion (UPE) and creatinine clearance (Ccr), are not significantly related to the ACE to ACE2 ratio as a whole, the HT status may reflect disease-induced deterioration of renal function. That is, UPE and Ccr of subjects with HT are significantly different from those without HT, in which a significant correlation is also observed between UPE and Ccr. Finally, stepwise regression analysis further revealed that only the HT status is an independent confounding determinant of the ACE to ACE2 ratio among the variables tested. Our data suggest that ACE2 might play an important role in maintaining a balanced status of local renin-angiotensin system synergistically with ACE by counterregulatory effects confounded by the presence of hypertension. Thus, ACE2 may exert pivotal effects on cardiovascular and renal conditions.

Absence of an interaction between the angiotensin-converting enzyme insertion-deletion polymorphism and pravastatin on cardiovascular disease in high-risk hypertensive patients: the Genetics of Hypertension-Associated Treatment (GenHAT) study

BACKGROUND

The aim of this study was to determine whether the angiotensin-converting enzyme (ACE) insertion-deletion (ID) polymorphism interacts with pravastatin to modify the risk of coronary heart disease (CHD) and other cardiovascular end points in a large clinical trial.

METHODS

GenHAT is an ancillary study of the ALLHAT. The ACE ID genotyped population in the lipid-lowering arm of ALLHAT included 9467 participants randomly assigned to pravastatin (n = 4741) or to usual care (n = 4726). The efficacy of pravastatin in reducing the risk of primary outcome (all-cause mortality) and secondary outcomes (fatal CHD and nonfatal myocardial infarction, cardiovascular disease [CVD] mortality, CHD, stroke, other CVD, non-CVD mortality, stroke, and heart failure) was compared between the genotype strata (dominant model ID + II vs DD, additive model II vs ID vs DD), by examining an interaction term in a Cox proportional hazards model.

RESULTS

The relative risk of fatal CHD and nonfatal myocardial infarction among subjects randomized to pravastatin compared with subjects randomized to usual care was similar in subjects with the II genotype (hazard ratio [HR] 0.84, 95% CI 0.59-1.18), the ID genotype (HR 0.84, 95% CI 0.68-1.03), and the DD genotype (HR 0.99, 95% CI 0.77-1.27).

CONCLUSIONS

We found no evidence that the ACE ID genotype was a major modifier of the efficacy of pravastatin in reducing the risk of cardiovascular events.

ACE phenotyping as a first step toward personalized medicine for ACE inhibitors. Why does ACE genotyping not predict the therapeutic efficacy of ACE inhibition?

Angiotensin (Ang)-converting enzyme (ACE) inhibitors are widely used for the treatment of cardiovascular diseases. Not all patients respond to ACE inhibitors, and it has been suggested that genetic variation might be a useful marker to predict the therapeutic efficacy of these drugs. In particular, the ACE insertion (I)/deletion (D) polymorphism has been investigated in this regard. Despite a decade of intensive research involving the genotyping of thousands of patients, we still do not know whether ACE genotyping helps in predicting the success of ACE inhibition. This review critically addresses the concept that predictive information on therapeutic efficacy of ACE inhibitors might be obtained based on ACE genotyping. It answers the following questions: Do higher ACE levels really result in higher Ang II levels? Is ACE the only converting enzyme in humans? Does ACE inhibition affect ACE expression? Why does ACE have 2 catalytically active domains? What is the relevance of ACE inhibitor-induced signaling through membrane-bound ACE? The review ends with the proposal that ACE phenotyping may prove to be a better first step toward personalized medicine for ACE inhibitors than ACE genotyping.

The kallikrein-kinin system: current and future pharmacological targets

The kallikrein-kinin system is an endogenous metabolic cascade, triggering of which results in the release of vasoactive kinins (bradykinin-related peptides). This complex system includes the precursors of kinins known as kininogens and mainly tissue and plasma kallikreins. The pharmacologically active kinins, which are often considered as either proinflammatory or cardioprotective, are implicated in many physiological and pathological processes. The interest of the various components of this multi-protein system is explained in part by the multiplicity of its pharmacological activities, mediated not only by kinins and their receptors, but also by their precursors and their activators and the metallopeptidases and the antiproteases that limit their activities. The regulation of this system by serpins and the wide distribution of the different constituents add to the complexity of this system, as well as its multiple relationships with other important metabolic pathways such as the renin-angiotensin, coagulation, or complement pathways. The purpose of this review is to summarize the main properties of this kallikrein-kinin system and to address the multiple pharmacological interventions that modulate the functions of this system, restraining its proinflammatory effects or potentiating its cardiovascular properties.

Insertion/deletion polymorphism of angiotensin converting enzyme gene in Kawasaki disease

Polymorphism of angiotensin converting enzyme (ACE) gene is reported to be associated with ischemic heart disease, hypertrophic cardiomyopathy, and idiopathic dilated cardiomyopathy. In this study, we investigated the relationship between Kawasaki disease and insertion/deletion polymorphism of ACE gene. Fifty five Kawasaki disease patients and 43 healthy children were enrolled. ACE genotype was evaluated from each of the subjects' DNA fragments through polymerase chain reaction (PCR). Frequencies of ACE genotypes (DD, ID, II) were 12.7%, 60.0%, 27.3% in Kawasaki group, and 41.9%, 30.2%, 27.9% in control group respectively, indicating low rate of DD and high rate of ID genotype among Kawasaki patients (p<0.01). Comparing allelic (I, D) frequencies, I allele was more prevalent in Kawasaki group than in control group (57.3% vs. 43.0%, p<0.05). In Kawasaki group, both genotype and allelic frequencies were not statistically different between those with coronary dilatations and those without. ACE gene I/D polymorphism is thought to be associated with Kawasaki disease but not with the development of coronary dilatations.

Effect of hypertension on angiotensin-(1–7) levels in rats with different angiotensin-I converting enzyme polymorphism

To determine circulating angiotensin-(1-7) [Ang-(1,7)] levels in rats with different angiotensin converting enzyme (ACE) genotypes and to evaluate the effect of hypertension on levels of this heptapeptide, plasma levels of angiotensin II (Ang II) and Ang-(1-7) were determined by HPLC and radioimmunoassay in (a) normotensive F0 and F2 homozygous Brown Norway (BN; with high ACE) or Lewis (with low ACE) rats and (b) in hypertensive F2 homozygous male rats (Goldblatt model). Genotypes were characterized by PCR and plasma ACE activity measured by fluorimetry. Plasma ACE activity was 2-fold higher (p < 0.05) in homozygous BN compared to homozygous Lewis groups. In the Goldblatt groups, a similar degree of hypertension and left ventricular hypertrophy was observed in rats with both genotypes. Plasma Ang II levels were between 300-400% higher (p < 0.05) in the BN than in the Lewis rats, without increment in the hypertensive animals. Plasma Ang-(1-7) levels were 75-87% lower in the BN rats (p < 0.05) and they were significantly higher (p < 0.05) in the hypertensive rats from both genotypes. Plasma levels of Ang II and Ang-(1-7) levels were inversely correlated in the normotensive rats (r = -0.64; p < 0.001), but not in the hypertensive animals. We conclude that there is an inverse relationship between circulating levels of Ang II and Ang-(1-7) in rats determined by the ACE gene polymorphism. This inverse relation is due to genetically determined higher ACE activity. Besides, plasma levels of Ang-(1-7) increase in renovascular hypertension.

The G protein-coupled receptors: pharmacogenetics and disease

Genetic variation in G-protein coupled receptors (GPCRs) is associated with a wide spectrum of disease phenotypes and predispositions that are of special significance because they are the targets of therapeutic agents. Each variant provides an opportunity to understand receptor function that complements a plethora of available in vitro data elucidating the pharmacology of the GPCRs. For example, discrete portions of the proximal tail of the dopamine D1 receptor have been discovered, in vitro, that may be involved in desensitization, recycling and trafficking. Similar in vitro strategies have been used to elucidate naturally occurring GPCR mutations. Inactive, over-active or constitutively active receptors have been identified by changes in ligand binding, G-protein coupling, receptor desensitization and receptor recycling. Selected examples reviewed include those disorders resulting from mutations in rhodopsin, thyrotropin, luteinizing hormone, vasopressin and angiotensin receptors. By comparison, the recurrent pharmacogenetic variants are more likely to result in an altered predisposition to complex disease in the population. These common variants may affect receptor sequence without intrinsic phenotype change or spontaneous induction of disease and yet result in significant alteration in drug efficacy. These pharmacogenetic phenomena will be reviewed with respect to a limited sampling of GPCR systems including the orexin/hypocretin system, the beta2 adrenergic receptors, the cysteinyl leukotriene receptors and the calcium-sensing receptor. These developments will be discussed with respect to strategies for drug discovery that take into account the potential for the development of drugs targeted at mutated and wild-type proteins.

Genetic variants in the angiotensin I-converting-enzyme (ACE) and angiotensin II receptor (AT1) gene and clinical outcome in depression

The insertion/(I)/deletion (D) polymorphism of the angiotensin-converting enzyme gene (ACE) is of increasing interest in etiology and treatment of various neuropsychiatric disorders. The present study aimed to replicate own earlier findings that depressive patients with the ACE D-allele are responding better to treatment with antidepressants than those with the II genotype. We further investigated a common polymorphism (A1166C) in the angiotensin II receptor gene (AT1) to examine a possibly combined influence. A sample of 273 patients with major depression, being treated with different classes of antidepressants, was enrolled in the study. Genotyping was carried out using a polymerase chain reaction and snapshot method, respectively, and the severity of depression was monitored using the HAMD-17 scale before and after 4 weeks of treatment. The ACE II genotypes showed poorer improvement in HAMD-17 scale after 4 weeks of treatment (ANOVA: F=4.49, p=0.01) than carriers with one or two D-alleles. Similarly, more than 70% of the AT1 CC homozygotes had a 50% reduction in the HAMD-17 scale within 4 weeks of treatment. Our data might further suggest that patients with a haplotype combining the CC and DD/ID genotypes respond better to treatment than those with either single allele. These results should however be replicated in future research.

Weight Gain after Liver Transplantation and the Insertion/Deletion Polymorphism of the Angiotensin-Converting Enzyme Gene

BACKGROUND

Subjects who carry the D allele of the angiotensin-converting enzyme (ACE) gene have higher plasma and tissue angiotensin II levels, possibly concurrent with the development of obesity. In transplant recipients, treatment with calcineurin antagonists would magnify these effects. The present study verifies whether the allelic variants of ACE are a factor involved in excess weight gain after liver transplantation.

METHODS

A consecutive series of 108 liver transplant recipients (73 males) were studied. Recipient ACE genotypes, determined by a polymerase chain reaction-based method, were related to body mass changes 1 year after transplant.

RESULTS

Body mass index (BMI) increased from the pretransplant value of 25.1+/-3.3 kg/m2 to 25.9+/-3.5 kg/m2 (P<0.005). The difference was mainly attributable to recipients carrying 1 D allele or more (N=88) in whom the BMI increased from 25.3+/-3.1 kg/m2 to 26.3+/-3.3 kg/m2 (P<0.005). A BMI of 25 kg/m or greater was measured in 30 of 45 deletion/deletion homozygotes and 25 of 43 insertion/deletion heterozygotes; in contrast, 14 of 20 insertion/insertion homozygotes had a normal body mass (P<0.01). Among patients with normal body mass pretransplant (N=56), none of 13 insertion/insertion homozygotes reached a BMI value 25 kg/m or greater posttransplant (P<0.005). At multivariate analysis, pretransplant body mass and carriage of 1 D allele or more were independent predictors of body mass gain greater than 2 kg/m.

CONCLUSIONS

Carriage of the D allele of the ACE gene is a strong, independent risk factor for excess weight gain after liver transplantation.

Association between plasma activities of semicarbazide-sensitive amine oxidase and angiotensin-converting enzyme in patients with type 1 diabetes mellitus

AIMS/HYPOTHESIS

Plasma semicarbazide-sensitive amine oxidase (SSAO) is elevated in patients with type 1 and type 2 diabetes and has been implicated in the pathophysiology of diabetic late complications. The regulation of SSAO production remains unknown. We studied correlations between plasma SSAO activity and parameters associated with diabetic late complications.

METHODS

Plasma SSAO was measured in a well-characterised group of 287 patients with type 1 diabetes. Standard statistical methods were used to investigate correlations with clinical parameters and components of the renin-angiotensin system.

RESULTS

Overall, plasma SSAO was elevated, at 693+/-196 mU/l (mean+/-SD; normal controls 352+/-102 mU/l). Plasma SSAO was higher in the group with late complications or hypertension, and in patients treated with ACE-inhibitors. In univariate analysis a significant positive correlation (p<0.001, r=0.27) was found between plasma SSAO and serum ACE activity in patients untreated with ACE inhibitors or angiotensin II receptor antagonists (n=221), but plasma SSAO did not differ by ACE I/D genotype. Plasma SSAO correlated positively with duration of diabetes, HbA(1)c and plasma renin, and negatively with plasma angiotensinogen and body mass index. A multiple regression analysis including these variables resulted in serum ACE activity (p<0.001), ACE genotype (negatively, p<0.001) and HbA(1)c (p=0.023) as explaining variables.

CONCLUSIONS/INTERPRETATION

Results suggest that a common factor is involved in the regulation of both plasma SSAO and serum ACE, which is different from the genetic determination of ACE activity.

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.

Association of angiotensinogen haplotypes with angiotensinogen levels but not with blood pressure or coronary artery disease: the Ludwigshafen Risk and Cardiovascular Health Study

Angiotensinogen and its cleaved forms angiotensin I and angiotensin II are important regulators of blood pressure. The gene for angiotensinogen (AGT) carries two common polymorphisms, T207M and M268T (previously described as T174M and M235T). To investigate the role of haplotypes formed by these polymorphisms for angiotensinogen levels we examined blood pressure, coronary artery disease (CAD), myocardial infarction (MI), and AGT genotypes and haplotypes in 2,575 patients with angiographically documented CAD and 731 individuals in whom CAD had been ruled out by angiography. Three haplotypes, designated as Hap1 (T207, M268), Hap2 (T207, T268) and Hap3 (M207, T268), accounted for more than 99% of alleles. The AGT Hap2 haplotype was significantly associated with angiotensinogen levels; one additional Hap2 allele accounted for an approx. 8% increase in angiotensinogen. This association was stronger than that of either single polymorphism. AGT genotypes or haplotypes were not related to hypertension, CAD or MI. We conclude that a common haplotype of the angiotensinogen gene is linked to angiotensinogen levels but has no major impact on blood pressure, hypertension, or cardiovascular risk.

Angiotensin-related genes in patients with panic disorder

Enhanced respiratory variability and decreased heart rate variability have repeatedly been observed in patients with panic disorder. Prompted by the notion that angiotensin may be involved in the control of respiration, heart rate variability, and anxiety-like behavior, we investigated the putative association between polymorphisms in three angiotensin-related genes and panic disorder-angiotensinogen (AGT), angiotensin converting enzyme (ACE), and angiotensin II (ANG II) receptor type 1 (ATr1) in 72 patients with panic disorder and 504 controls. Allele and genotype distribution of the ATr1 A1166C allele and the AGT M235T did not differ between patients and controls. With respect to the ACE I/D polymorphism, the I allele was found to be more frequent in male (chi(2) = 8.042, df = 1, P = 0.005), but not female, panic disorder patients than in controls. The results of this investigation provide preliminary evidence for the suggestion that angiotensin-related genes may be associated with panic disorder in men.

Neutral endopeptidase and angiotensin I converting enzyme insertion/deletion gene polymorphism in humans

Neutral endopeptidase (NEP) hydrolyses angiotensins (Ang) I and II and generates angiotensin-(1-7) [Ang-(1-7)]. In humans, the insertion/deletion (I/D) angiotensin-I converting enzyme (ACE) gene polymorphism determined plasma ACE levels by 40%. In rats, a similar polymorphism determines ACE levels which are inversely associated to NEP activity. The objective of this study is to evaluate the relationship between ACE expression and plasma NEP activity in normotensive subjects and in hypertensive patients. In total, 58 consecutive patients with hypertension, evaluated in our Hypertension Clinic, were compared according to their ACE I/D genotypes with 54 control subjects in terms of both plasma ACE activity and NEP activities. Plasma ACE activity was elevated 51 and 70% in both DD ACE groups (normotensives and hypertensives) compared with their respective ID and II ACE groups (P<0.001). A significant effect of the ACE polymorphism and of the hypertensive status on ACE activity was observed (P<0.001). In normotensive DD ACE subjects, NEP activity was 0.30+/-0.02 U/ml, whereas in the normotensive II ACE and in the normotensive ID ACE subjects NEP activity was increased 65 and 48%, respectively (P<0.001). In the hypertensive DD ACE patients, NEP activity was 0.47+/-0.03 U/mg. An effect of the I/D ACE genotypes on NEP activity (P<0.04) and an interaction effect between the I/D ACE genotype and the hypertensive status were also observed (P<0.001). These results are consistent with a normal and inverse relationship between the ACE polymorphism and NEP activity in normotensive humans (as is also observed in rats). This normal relationship is not observed in hypertensive patients.

Transforming growth factor-beta 1 production is correlated with genetically determined ACE expression in congenic rats: a possible link between ACE genotype and diabetic nephropathy

Genetic background appears to modulate the development of diabetic vascular complications. In particular, polymorphisms in the ACE gene have been associated with diabetic nephropathy and, in some studies, macrovascular complications. However, the links between ACE gene polymorphism and factors implicated in diabetes complications remain unknown. The aim of this study was to determine whether the ACE genotype could modify factors, such as transforming growth factor (TGF)-beta 1, involved in the complications of diabetes. For this purpose, congenic rats (L.BNAce10), differing from the LOU strain in only a small segment of chromosome 10 containing the ACE locus, were generated. These congenic rats have plasma ACE levels twice as high as the donor strain. Diabetes was induced in rats of both strains, and its effects on ACE and TGF-beta 1 expressions were evaluated in lungs and kidneys. In lung, the main source of ACE production, ACE mRNA levels and activity were higher in L.BNAce10 rats than in LOU rats. Diabetes increased ACE lung expression in rats of both strains in a similar manner. TGF-beta 1 expression was also higher in lungs of L.BNAce10 compared with LOU rats and was also increased by diabetes. Furthermore, a strong correlation was found between TGF-beta 1 and ACE expressions. In renal arterioles, ACE and TGF-beta mRNA expressions were higher in L.BNAce10 rats than LOU rats (both diabetic and nondiabetic). In these vessels, there was also a correlation between ACE and TGF-beta 1 expressions. Urine TGF-beta 1 concentration depended on the genotype and was further increased by diabetes. These results show that TGF-beta 1 expression is correlated with ACE expression and suggest that this growth factor could be a link between ACE gene polymorphism and diabetic vascular complications.

Regulation of the angiotensin-converting enzyme activity by a time-course hypoxia in the carotid body

Chronic hypoxia activates a local angiotensin-generating system in the carotid body. Here, we test the hypothesis that the activity of the critical enzyme for this system, angiotensin-converting enzyme (ACE), in the carotid body is subject to regulation by a time-course hypoxia. Results from the carotid body assays showed that ACE activity was markedly increased under the hypoxic stress of 7-, 14-, 21-, and 28-day exposures. The changes in ACE activity of 7-day (15.00 vs. 30.95 x 10(-5) nmol.microg(-1).min(-1)), 14-day (8.73 vs. 30.25 x 10(-5) nmol.microg(-1).min(-1)), and 21-day (11.41 vs. 31.83 x 10(-5) nmol.microg(-1).min(-1)) hypoxia treatments were enhanced significantly. However, ACE activity in 28-day (13.18 vs. 24.53 x 10(-5) nmol.microg(-1).min(-1)) hypoxia treatment was observed to increase insignificantly when compared with results in the respective control groups. Captopril inhibited all rises in ACE activity in both the control and experimental groups. Results clearly indicate an activation of the enzymatic activity of ACE, the critical enzyme for determining the conversion of angiotensin I into the physiologically active angiotensin II, by chronic hypoxia in the carotid body. An increase in the ACE activity may increase the local production of angiotensin II in the carotid body and thus its agonist action at the AT1 receptor. This may be important in the modulation of cardiopulmonary adaptation in the hypoxic ventilatory response as well as for electrolyte and water homeostasis during chronic hypoxia.

Genetic polymorphism of the renin???angiotensin???aldosterone system and arterial hypertension in the Italian population

OBJECTIVE

To detect the association of single polymorphisms of the renin-angiotensin-aldosterone system (RAAS), or different combinations thereof, with hypertension.

DESIGN AND METHODS

The GENIPER database is the result of a collaborative effort of 13 Italian research centres to collect genomic DNA in subjects well characterized in terms of blood pressure status. A total of 2461 subjects (normotensive = 611; hypertensive = 1850) were selected and genotyped for the angiotensin-converting enzyme insertion/deletion (ACE I/D), angiotensinogen (AGT) T/C704, angiotensin receptor type 1 (AT1) A/C1166 and aldosterone synthase (ALDO) T/C-344 genetic variants.

RESULTS

Allele frequencies were homogeneous over the Italian territory, with the relevant exception of the ACE I/D, the D allele being significantly less frequent in the northern region (61%) than in the rest of the country (67%; P < 0.0001). When comparing allele and genotype distributions in normotensives and hypertensives, the latter presented a small but statistically significant increase of the C allele of AGT T/C704, the A allele of AT1 A/C1166 and the T allele of ALDO T/C-344 polymorphisms (P = 0.018, P = 0.037 and P = 0.015, respectively), with similar trends all over the country. A step-wise logistic regression analysis confirmed these findings, by entering in the model as independent predictors of blood pressure status of AGT T/C704 (P = 0.013), ALDO T/C-344 (P = 0.032) and AT1 A/C1166 polymorphisms (P = 0.075), but not ACE I/D (P = 0.996). We also found some evidence of an additive effect of individual genetic variants of the RAAS, modulating at different levels the same functional pathway, on the risk of developing hypertension, but no synergistic interaction was observed.

CONCLUSIONS

Our results suggest that some allelic variants of RAAS genes carry a small but identifiable risk of developing arterial hypertension.

Levels of plasma angiotensin-(1-7) in patients with hypertension who have the angiotensin-I-converting enzyme deletion/deletion genotype

In patients with hypertension who have the DD-ACE genotype (higher angiotensin-converting enzyme [ACE] activity), plasma levels of angiotensin-(1-7) are 4 times lower than in patients with the II-ACE genotype (lower ACE levels). Angiotensin II levels are similar in both groups.

Local renin-angiotensin systems: the unanswered questions

The concept of local renin-angiotensin systems has been introduced almost 20 years ago to explain the beneficial blood pressure-independent effects of ACE inhibitors and AT(1) receptor antagonists in cardiovascular diseases. In the past decade, research has focussed on the local effects of angiotensin II rather than on the mechanism(s) of its local generation. This review addresses several of the unanswered questions with regard to tissue angiotensin II generation, focussing in particular on the heart and vascular wall: (1) what is the origin of the renin that is required to generate angiotensin II locally, (2) where does tissue angiotensin generation occur (intra- versus extracellular), (3) what is the importance of alternative (non-renin, non-ACE) angiotensin-generating enzymes, (4) do ACE inhibitors and AT(1) receptor antagonists exert local effects that are renin-angiotensin system independent (thereby incorrectly leading to the conclusion that they interfere with the local generation or effects of angiotensin II), and (5) to what degree do differences in tissue angiotensin generation underlie the association between cardiovascular diseases and renin-angiotensin system gene polymorphisms?

Variations of human adrenomedullin gene and its relation to cardiovascular diseases

The studies concerning the structure and variations of the human adrenomedullin (AM) gene are reviewed, and their relations to the gene function and genetic predisposition to cardiovascular diseases are discussed. The genomic human AM gene is composed of four exons, and the whole nucleotide sequence corresponding to mature AM resides in the fourth exon. In chromosomal sublocalization, the AM gene is located in the distal portion of the short arm of chromosome 11 (11p15.1-3). Analysis of the promoter region of the AM gene has revealed that two transcription factors, nuclear factor for interleukin-6 expression (NF-IL6) and activator protein 2 (AP-2), participate in the regulation of AM gene expression. It is surmised that NF-IL6 mediates inflammatory stimuli and AP-2 mediates signals of phospholipase C and protein kinase C activation. In addition to these factors, hypoxia induces AM gene expression via the hypoxia inducible factor-1 (HIF-1) binding site. The 3'-end of the AM gene is flanked by a microsatellite marker of cytosine adenine (CA) repeats. In Japanese, there are four types of alleles with different CA-repeat numbers: 11, 13, 14 and 19. It is suggested that existence of the 19-repeat allele is associated with genetic predispositions to develop essential hypertension and diabetic nephropathy.

Angiotensinogen 235T allele "dosage" is associated with blood pressure phenotypes

The genetic mechanisms underlying interindividual blood pressure variation among humans may reflect, at least in part, clustering of functional gene variants belonging to complex blood pressure control systems. In this study, we investigated the association of specific functional gene variants of the renin-angiotensin system, ACE (I/D) and angiotensinogen (M/T) genes, with blood pressure phenotypes (systolic, mean, diastolic, and pulse pressure), in an ethnically mixed urban population in Brazil. Individuals (n=1421) were randomly selected from the general population of the Vitoria City Metropolitan area. Neither gender, age, smoking status, total cholesterol, triglycerides, HDL-cholesterol, LDL-cholesterol, VLDL-cholesterol, or diabetes was associated with ACE or AGT polymorphism in univariate analysis. No association was found between ACE variants and blood pressure phenotypes. However, a statistically significant association was revealed between the AGT 235T variant and all blood pressure phenotypes, consistent with an additive/codominant mode of action even after adjustment for age and gender (P<0.01). Genotypic analysis contemplating both ACE and AGT variants in the same model did not show any significant interaction between both genetic polymorphisms. In addition, the AGT 235T allele was significantly associated with hypertension in a recessive model, which remained as an independent risk factor for hypertension even after adjustment for age, gender, and ethnicity (OR, 1.33; 95% CI, 1.04 to 1.70). Taken together, these data indicate a linear relation between AGT 235T allele number ("dosage") and blood pressure in an ethnically mixed urban population and confirmed its role as an independent risk factor for hypertension for men and women when in homozygosity.