Synergistic effects of angiotensin-converting enzyme and angiotensin-II type 1 receptor gene polymorphisms on risk of myocardial infarction

Angiotensin-converting enzyme insertion/deletion gene polymorphism in a Tunisian healthy and acute myocardial infarction population

INTRODUCTION

The role of the insertion/deletion (I/D) polymorphism in the angiotensin-converting enzyme gene (ACE) on acute myocardial infarction (AMI) is controversial.

OBJECTIVES

To assess the effect of the ACE I/D polymorphism on AMI compared with the healthy controls and its relationship with serum ACE activity in a Tunisian population.

DESIGN AND METHODS

A total of 119 patients with AMI were compared with 238 healthy controls from the same geographical area. ACE genotyping was determined by polymerase chain reaction, and serum ACE activity was measured with N-[3-(2-furylacryloyl]-L-phenylalanyl-L-glycyl-L-glycine as substrate.

RESULTS

The ACE I/D polymorphism was significantly different between patients and controls (p < 0.0001). The frequencies of the DD genotype and the D allele were statistically higher in patients with AMI as compared with the controls and were associated with increased risk of AMI (DD vs. ID and II: odds ratio = 4.27, p < 0.0001, 95% confidence interval = 2.65-6.86; D vs. I: odds ratio = 3.15, p < 0.0001, 95% confidence interval = 2.26-4.40). This association was independent of other cardiovascular risk factors but dyslipidemia (p = 0.002) that was not represented in AMI patients with II genotype and in a lower extent with hypertension (p < 0.05). Serum ACE activity was significantly higher in AMI patients with ACE DD genotype compared with the subjects with ID or II genotype (p = 0.034) and was not correlated with other cardiovascular risk factors.

CONCLUSIONS

ACE DD genotype associated with higher serum ACE activity is increased in the studied population and might be clinically useful as markers to assess risk for AMI.

Genotypic interactions of renin-angiotensin system genes with diabetes type 2 in a Tunisian population

AIMS

To explore the role of genetic variants of angiotensinogen (AGT M235T), angiotensin-converting enzyme (ACE I/D), and angiotensin type 1 receptor (AT1R A1166C) as predictors of diabetes risk and to examine their combined effects on type 2 diabetes mellitus (T2DM) patients.

MAIN METHODS

One hundred and fourteen T2DM patients were compared to 175 healthy controls with similar age and sex.

KEY FINDINGS

The genotypic frequencies for all three genes alone were significantly associated with increased risk of developing diabetes. Logistic regression analysis of classic coronary risk factors and the genetic polymorphisms demonstrated that hypertension and ACE DD genotype were the most significant contributors to T2DM. For the renin-angiotensin system (RAS) genes, the risk of T2DM in individuals with one risk genotype was 1.9 (95%CI: 1.1-3.0, p=0.017) higher than those with zero risk genotype. Individuals who carried two risk genotypes had a 4.0 (95%CI 1.7-9.4, p=0.001) times higher risk of T2DM than those who did not carry any risk genotypes of the RAS genes. Most interestingly, the risk of T2DM for individuals with three risk genotypes was 26.2 (95%CI: 5.8-117.9, p<0.001) higher than those with zero risk genotype.

SIGNIFICANCE

The results of the present study imply that genotyping of renin-angiotensin system genes could become an important part of the clinical process of risk identification for T2DM in Tunisian population.

microRNAs in diseases: from candidate to modifier genes

Until recently, the search for genetic factors predisposing or causing Mendelian diseases focused almost exclusively on protein coding sequences. As essential components of the regulatory system of gene expression, microRNAs (miRNAs) hold great promises into elucidating a number of inherited diseases. The herein review focuses on the genetic variations, whether copy number variation (CNV) or single nucleotide polymorphism (SNP), alternatively at the levels of the miRNA gene itself and of its target genes. We consider miRNA as the candidate gene, or the regulator of a disease-causing gene, or the modifier gene. The best paradigms of the field are presented in both monogenic diseases and complex traits. The computational tools, which are essential into identifying miRNAs and characterizing miRNA targets, are overviewed.

Angiotensin II type 1 receptor gene polymorphism in myocardial infarction patients

Introduction. Acute myocardial infarction is commonly known as heart attack. It is a multifactorial disease influenced by environmental and genetic factors.The objective of the present study was to investigate the association of the angiotensin II type 1 receptor gene A/C polymorphism in South Indian myocardial infarction patients.

Subjects and methods. The present study included a total number of 221 subjects (107 myocardial infarction patients and 114 age- and sex-matched controls). Demographic and clinical characteristics were collected. Lipid profiles were estimated. DNA was isolated and the angiotensin II type 1 receptor gene A/C polymorphism was determined by polymerase chain reaction.

Results. Comparison of the lipid profiles between patients and controls showed that patients had statistically highly significant values (p=0.0001).The CC genotype of the angiotensin II type 1 receptor was not associated with myocardial infarction patients when compared to controls. CC vs. AA was χ2 = 2.08, odds ratio 2.30, 95% confidence interval 0.72 — 7.23, and p value was 0.14.

Conclusion. The angiotensin II type 1 receptor CC genotype is not a risk factor for myocardial infarction in patients in a South Indian population.

Analysis of segregation distortion and association of the bovine FGF2 with fertilization rate and early embryonic survival

Fibroblast growth factor 2 (FGF2) plays an important role in fertility and early embryo development. The objectives of this study were to test the association of FGF2 polymorphisms with fertilization success in cattle using an in vitro fertilization experimental system and to investigate the mechanisms leading to the presence of rare alleles of FGF2 in the Holstein population. A total of 7502 fertilizations were performed and a total of 5049 embryos were produced to collect fertilization and embryo survival records. A total of 444 ovaries, from which oocytes were aspirated and fertilized, were genotyped for two single nucleotide polymorphisms (SNPs) previously identified in FGF2 (g.23G>T and g.11646A>G). Frequency of the TT genotype of the g.23G>T SNP was low in the ovary population (5.4%) and in a different Holstein cattle population (6.6%) examined in this study. Single SNP analysis showed that both SNPs were associated with early embryonic survival rate. Two-way interaction analysis revealed significant association of epistatic interaction between the SNPs with fertilization rate. To test whether or not low frequency of allele T for the g.23G>T SNP in the population is a result of a fertilization failure of T oocytes, semen from six GG bulls was used to fertilize a total of 458 oocytes obtained from 19 GT ovaries. A significant segregation distortion was observed for 169 embryos genotyped for the g.23G>T SNP. We conclude that oocytes carrying the T allele show a reduced fertilization rate and that segregation distortion leads to rarity of the TT genotype in the population.

Epistatic module detection for case-control studies: a Bayesian model with a Gibbs sampling strategy

The detection of epistatic interactive effects of multiple genetic variants on the susceptibility of human complex diseases is a great challenge in genome-wide association studies (GWAS). Although methods have been proposed to identify such interactions, the lack of an explicit definition of epistatic effects, together with computational difficulties, makes the development of new methods indispensable. In this paper, we introduce epistatic modules to describe epistatic interactive effects of multiple loci on diseases. On the basis of this notion, we put forward a Bayesian marker partition model to explain observed case-control data, and we develop a Gibbs sampling strategy to facilitate the detection of epistatic modules. Comparisons of the proposed approach with three existing methods on seven simulated disease models demonstrate the superior performance of our approach. When applied to a genome-wide case-control data set for Age-related Macular Degeneration (AMD), the proposed approach successfully identifies two known susceptible loci and suggests that a combination of two other loci -- one in the gene SGCD and the other in SCAPER -- is associated with the disease. Further functional analysis supports the speculation that the interaction of these two genetic variants may be responsible for the susceptibility of AMD. When applied to a genome-wide case-control data set for Parkinson's disease, the proposed method identifies seven suspicious loci that may contribute independently to the disease.

Association of genetic polymorphisms in the ACE, ApoE, and TGF beta genes with early onset ischemic heart disease

BACKGROUND

The genetic factors that contribute to ischemic heart disease (IHD) are poorly understood, and it is likely that multiple genes acting independently or synergistically contribute to the risk of IHD and outcome. The genes for angiotensin-converting enzyme (ACE) and apolipoprotein E (ApoE) have been implicated independently in the risk of IHD.

HYPOTHESIS

This study examined whether genetic polymorphisms in the ACE and ApoE genes are associated with early onset IHD. Polymorphisms in a third gene, transforming growth factor beta 2 (TGF beta 2), with a known role in wound repair and cardiac development, are also examined with respect to early onset IHD.

METHODS

In all, 101 patients with IHD and onset of disease before 55 years for men and 60 years for women, and 100 controls with angiographically confirmed normal coronary arteries were recruited for this study. The ACE, ApoE, and TGF beta 2 genotypes were determined by polymerase chain reaction amplification or Southern blotting and were compared with the patient's clinical and family histories.

RESULTS AND CONCLUSION

The frequency of the ACE D allele was significantly lower in the patient group (0.475) than in the control group (0.59, p = 0.03), which was attributed to a reduction in the number of patients with the DD genotype (patients: 24% DD, controls: 33% DD). Sudden cardiac death was also associated with the DD genotype. These data are consistent with the ACE D allele contributing to a fatal outcome. No association between the DD genotype and risk of myocardial infarction, presenting age, extent of vessel disease, family history, hypertension, or hypercholesterolemia was seen. Analysis of the ApoE genotype showed no association with early onset IHD. There was no evidence for a synergistic effect between the ACE and ApoE genotypes on the risk of early onset IHD. A polymorphism in the TGF beta 2 gene was rare and not associated with early onset IHD.

A random forest approach to the detection of epistatic interactions in case-control studies

BACKGROUND

The key roles of epistatic interactions between multiple genetic variants in the pathogenesis of complex diseases notwithstanding, the detection of such interactions remains a great challenge in genome-wide association studies. Although some existing multi-locus approaches have shown their successes in small-scale case-control data, the "combination explosion" course prohibits their applications to genome-wide analysis. It is therefore indispensable to develop new methods that are able to reduce the search space for epistatic interactions from an astronomic number of all possible combinations of genetic variants to a manageable set of candidates.

RESULTS

We studied case-control data from the viewpoint of binary classification. More precisely, we treated single nucleotide polymorphism (SNP) markers as categorical features and adopted the random forest to discriminate cases against controls. On the basis of the gini importance given by the random forest, we designed a sliding window sequential forward feature selection (SWSFS) algorithm to select a small set of candidate SNPs that could minimize the classification error and then statistically tested up to three-way interactions of the candidates. We compared this approach with three existing methods on three simulated disease models and showed that our approach is comparable to, sometimes more powerful than, the other methods. We applied our approach to a genome-wide case-control dataset for Age-related Macular Degeneration (AMD) and successfully identified two SNPs that were reported to be associated with this disease.

CONCLUSION

Besides existing pure statistical approaches, we demonstrated the feasibility of incorporating machine learning methods into genome-wide case-control studies. The gini importance offers yet another measure for the associations between SNPs and complex diseases, thereby complementing existing statistical measures to facilitate the identification of epistatic interactions and the understanding of epistasis in the pathogenesis of complex diseases.

The risk of coronary artery disease associated with cigarette smoking and hypercholesterolemia is additionally increased by the presence of the AT1R gene 1166C allele

Cigarette smoking and hypercholesterolemia influence the renin-angiotensin system (RAS) functions, including increased RAS-mediated vasoconstriction, mitogenic signaling, and angiotensin II type 1 receptor (AT1R) expression. We have explored the interactions of the AT1R gene 1166 A>C polymorphism and traditional risk factors using an epidemiological approach. The study cohort included 341 subjects; 172 were patients with angiographically confirmed coronary artery disease (CAD) and 169 were blood donors. The 1166 A>C polymorphism was genotyped using the PCR-RFLP method. We found a synergy of the 1166C allele with cigarette smoking (synergy indices: SI = 1.41, SIM = 1.33), LDL cholesterol levels > or = 3 mmol/l (SI = 1.25, SIM = 1.19), and elevated total cholesterol (> or =5 mmol/l) levels (SI = 1.15, SIM = 1.13). In each case, the estimated CAD risk was greater than that predicted by assuming the additivity and multiplication of effects. We conclude that the 1166C allele increases the risk of CAD associated with the presence of cigarette smoking and hypercholesterolemia.

Molecular genetics of myocardial infarction

Myocardial infarction (MI) is an important clinical problem because of its large contribution to mortality. The main causal and treatable risk factors for MI include hypertension, hypercholesterolemia or dyslipidemia, diabetes mellitus, and smoking. In addition to these risk factors, recent studies have shown the importance of genetic factors and interactions between multiple genes and environmental factors. Disease prevention is an important strategy for reducing the overall burden of MI, with the identification of markers for disease risk being key both for risk prediction and for potential intervention to lower the chance of future events. Although genetic linkage analyses of families and sib-pairs as well as candidate gene and genome-wide association studies have implicated several loci and candidate genes in predisposition to coronary heart disease (CHD) or MI, the genes that contribute to genetic susceptibility to these conditions remain to be identified definitively. In this review, we summarize both candidate loci for CHD or MI identified by linkage analyses and candidate genes examined by association studies. We also review in more detail studies that have revealed the association with MI or CHD of polymorphisms in MTHFR, LPL, and APOE by the candidate gene approach and those in LTA and at chromosomal region 9p21.3 by genome-wide scans. Such studies may provide insight into the function of implicated genes as well as into the role of genetic factors in the development of CHD and MI.

RAS gene polymorphisms, classical risk factors and the advent of coronary artery disease in the Portuguese population

Background

Several polymorphisms within the renin-angiotensin system cluster of genes have been associated with the advent of coronary artery disease (CAD) or related pathologies. We investigated the distribution of 5 of these polymorphisms in order to find any association with CAD development and distinguish if any of the biochemical and behavioural factors interact with genetic polymorphisms in the advent of the disease.

Methods

ACE I/D (rs4340), ACE A11860G (rs4343), AT1R A1166C (rs5186), AGT T174M (rs4762) and AGT M235T (rs699) gene polymorphisms were PCR-RFLP analysed in 298 CAD patients and 510 controls from Portugal. Several biochemical and behavioural markers were obtained.

Results

ACE I/D DD and ACE11860 GG genotypes are risk factors for CAD in this population. The simultaneous presence of ACE I/D I and ACE11860 A alleles corresponds to a significant trend towards a decrease in CAD incidence. We found several synergistic effects between the studied polymorphisms and classical risk factors such as hypertension, obesity, diabetes and dyslipidaemia: the presence of the DD genotype of ACE I/D (and also ACE11860 GG) increases the odds of developing CAD when associated to each one of these classical risk factors, particularly when considering the male and early onset CAD subgroup analysis; AGT235 TT also increases the CAD risk in the presence of hypertension and dyslipidaemia, and AT1R1166 interacts positively with hypertension, smoking and obesity.

Conclusion

ACE polymorphisms were shown to play a major role in individual susceptibility to develop CAD. There is also a clear interaction between RAS predisposing genes and some biochemical/environmental risk factors in CAD onset, demonstrating a significant enhancement of classical markers particularly by ACE I/D and ACE11860.

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Genetics of sudden cardiac arrest

Sudden cardiac arrest (SCA) due to ventricular arrhythmias is a major cause of mortality in western populations with up to 450,000 deaths in the United States each year. Although environmental factors clearly contribute to the determinants of SCA, familial aggregation studies and advances in the molecular genetics of inherited arrhythmias suggest that genetic factors confer susceptibility to SCA in the general population. Research in this area typically has focused on association of common genetic variants with intermediate phenotypes that predispose to SCA risk, such as QT interval, but few studies have examined genetic risk factors for SCA. We review the evidence for genetic susceptibility to SCA in the general population and focus on the studies published to date that have explored genetic risk factors.

Genetic polymorphisms of the RAS-cytokine pathway and chronic kidney disease

Chronic kidney disease (CKD) in children is irreversible. It is associated with renal failure progression and atherosclerotic cardiovascular (CV) abnormalities. Nearly 60% of children with CKD are affected since birth with congenital or inherited kidney disorders. Preliminary evidence primarily from adult CKD studies indicates common genetic risk factors for CKD and atherosclerotic CV disease. Although multiple physiologic pathways share common genes for CKD and CV disease, substantial evidence supports our attention to the renin angiotensin system (RAS) and the interlinked inflammatory cascade because they modulate the progressions of renal and CV disease. Gene polymorphisms in the RAS-cytokine pathway, through altered gene expression of inflammatory cytokines, are potential factors that modulate the rate of CKD progression and CV abnormalities in patients with CKD. For studying such hypotheses, the cooperative efforts among scientific groups and the availability of robust and affordable technologies to genotype thousands of single nucleotide polymorphisms (SNPs) across the genome make genome-wide association studies an attractive paradigm for studying polygenic diseases such as CKD. Although attractive, such studies should be interpreted carefully, with a fundamental understanding of their potential weaknesses. Nevertheless, whole-genome association studies for diabetic nephropathy and future studies pertaining to other types of CKD will offer further insight for the development of targeted interventions to treat CKD and associated atherosclerotic CV abnormalities in the pediatric CKD population.

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.

Pharmacogenomics of G protein-coupled receptor signaling: insights from health and disease

The identification and characterization of the processes of G protein-coupled receptor (GPCR) activation and inactivation have refined not only the study of the GPCRs but also the genomics of many accessory proteins necessary for these processes. This has accelerated progress in understanding the fundamental mechanisms involved in GPCR structure and function, including receptor transport to the membrane, ligand binding, activation and inactivation by GRK-mediated (and other) phosphorylation. The catalog of G(s)alpha and Gbeta subunit polymorphisms that result in complex phenotypes has complemented the effort to catalog the GPCRs and their variants. The study of the genomics of GPCR accessory proteins has also provided insight into pathways of disease, such as the contributions of regulator of G protein signaling (RGS) protein to hypertension and activator of G protein signaling (AGS) proteins to the response to hypoxia. In the case of the G protein-coupled receptor kinases (GRKs), identified originally in the retinal tissues that converge on rhodopsin, proteins such as GRK4 have been identified that have been subsequently associated with hypertension. Here, we review the structure and function of GPCR and associated proteins in the context of the gene families that encode them and the genetic disorders associated with their altered function. An understanding of the pharmacogenomics of GPCR signaling provides the basis for examining the GPCRs disrupted in monogenic disease and the pharmacogenetics of a given receptor system.

Genetic polymorphisms contribute to acute kidney injury after coronary artery bypass grafting

BACKGROUND

Acute kidney injury is one of the most serious complications after cardiac surgery. Genetic polymorphisms are reported to be associated with postoperative renal impairment. The aim of this study was to investigate the relationship between selected gene polymorphisms and acute kidney injury after cardiac surgery.

METHODS

Two hundred forty-eight elective coronary artery bypass grafting procedure patients were enrolled in the study. Angiotensin-converting enzyme (ACE) II, ID, and DD, apolipoprotein E (APO E), and angiotensin II type 1 receptor (AGTR1) A1166C genotypes were detected by polymerase chain reaction. Plasma levels of ACE were analyzed by enzyme-linked immunosorbent assay. Acute kidney injury after cardiac surgery was graded according to the RIFLE (risk, injury, failure, loss, and end-stage kidney disease) classification.

RESULTS

In our study, 21.8% of patients had acute renal impairment after cardiac surgery. Among the 54 patients with acute kidney injury, ACE D allele frequency was 0.620. The plasma levels of ACE were significantly higher in the D allele carriers (P = .018). Three of the 54 patients with acute kidney injury were APO E epsilon 4 allele carriers (P = .002). AGTR1 C allele carriers constituted 46% of all patients with postoperative acute kidney injury. There was no statistically significant difference between A allele homozygotes and C allele carriers with respect to postoperative renal dysfunction (P > .05).

CONCLUSIONS

The present findings support the hypothesis that ACE I/D and APO E gene polymorphisms may play a role in the development of acute kidney injury after cardiac surgery. However, AGTR1 does not have a unique association with postoperative renal impairment.

Polymorphisms of the renin-angiotensin system are associated with blood pressure, atherosclerosis and cerebral white matter pathology

BACKGROUND

The renin-angiotensin system is involved in the development of hypertension, atherosclerosis and cardiovascular disease. We studied the association between the M235T polymorphism of the angiotensinogen gene (AGT) and the C573T polymorphism of the angiotensin II type 1 receptor (AT1R) and blood pressure, carotid atherosclerosis and cerebrovascular disease.

METHODS

We genotyped over 6000 subjects from the Rotterdam Study and more than 1000 subjects from the Rotterdam Scan Study. We used logistic regression and univariate analyses, adjusting for age and sex with, for AGT, the MM and, for AT1R, the TT genotype as reference.

RESULTS

We found that AGT-235T increased systolic (p for trend = 0.03) and diastolic blood pressure (p for trend = 0.04). The prevalence of carotid plaques was increased 1.25-fold (95% CI 1.02-1.52) in AGT-TT carriers. There was a significant increase in mean volume deep subcortical white matter lesions (WML) for AGT-TT carriers (1.78 ml vs 1.09 ml in the reference group; p = 0.008). A significant interaction was found between AGT and AT1R, further increasing the effect on periventricular and subtotal WML (p for interaction = 0.02). We found a non-significant increased risk of silent brain infarction for AGT-TT carriers and AT1R-CC carriers, but no effect on stroke.

CONCLUSION

We found an association between AGT and blood pressure, atherosclerosis and WML. Also, we found synergistic effects between AGT and AT1R on the development of WML. These findings raise the question of whether the renin-angiotensin system may be a therapeutic target for the prevention of cerebral white matter pathology.

The human angiotensin II type 1 receptor +1166 A/C polymorphism attenuates microRNA-155 binding

The adverse effects of angiotensin II (Ang II) are primarily mediated through the Ang II type 1 receptor (AT1R). A silent polymorphism (+1166 A/C) in the human AT1R gene has been associated with cardiovascular disease, possibly as a result of enhanced AT(1)R activity. Because this polymorphism occurs in the 3'-untranslated region of the human AT1R gene, the biological importance of this mutation has always been questionable. Computer alignment demonstrated that the +1166 A/C polymorphism occurred in a cis-regulatory site, which is recognized by a specific microRNA (miRNA), miR-155. miRNAs are noncoding RNAs that silence gene expression by base-pairing with complementary sequences in the 3'-untranslated region of target RNAs. When the +1166 C-allele is present, base-pairing complementarity is interrupted, and the ability of miR-155 to interact with the cis-regulatory site is decreased. As a result, miR-155 no longer attenuates translation as efficiently as demonstrated by luciferase reporter and Ang II radioreceptor binding assays. In situ hybridization experiments demonstrated that mature miR-155 is abundantly expressed in the same cell types as the AT1R (e.g. endothelial and vascular smooth muscle). Finally, when human primary vascular smooth muscle cells were transfected with an antisense miR-155 inhibitor, endogenous human AT1R expression and Ang II-induced ERK1/2 activation were significantly increased. Taken together, our study demonstrates that the AT1R and miR-155 are co-expressed and that miR-155 translationally represses the expression of AT1R in vivo. Therefore, our study provides the first feasible biochemical mechanism by which the +1166 A/C polymorphism can lead to increased AT1R densities and possibly cardiovascular disease.

Late ventricular remodeling in non-reperfused acute myocardial infarction in humans is predicted by angiotensin II type 1 receptor density on blood platelets

BACKGROUND

Ventricular remodeling after myocardial infarction (MI) is largely dependent on renin-angiotensin system activity, which is determined by angiotensin II concentration and angiotensin II type 1 receptor (AT(1)R) density in target tissues. We have recently shown that AT(1)R density in the acute phase of MI determines post-MI ventricular remodeling at discharge (8 days). The aim of this study was to test whether this correlation is retained in a longer follow-up (6 months), in the same group of patients.

METHODS

In 48 patients with first acute MI who did not undergo reperfusion therapy, angiotensin AT(1)R density on blood platelets (a presumable marker of cardiovascular AT(1)R density) was assessed 13+/-5 h after the onset of MI, using radioligand binding assay. Echocardiographic indices of left ventricular function and dimensions were used as measures of ventricular remodeling.

RESULTS

6 months after the infarction patients who at baseline had AT(1)R density above median (N=17) as compared to those with AT(1)R density below median (N=20) had higher left ventricular end-systolic volume index (LVESVI, 41.3+/-2.7 vs. 33.2+/-2.3) and lower ejection fraction (LVEF 48.1+/-1.8 vs. 54.7+/-2.0). Moreover LVESVI positively and LVEF negatively correlated with AT(1)R density although the strength of these correlations was weaker than at discharge. Infarct size as reflected by a single troponin T measurement and post-MI therapy did not differ between high- and low-AT(1)R groups: over 85% patients received ACE-inhibitor, beta-blocker and statin.

CONCLUSIONS

High AT(1)R density on blood platelets (a presumable marker of cardiovascular AT(1)R density) drawn in the acute phase of MI predicts poorer left ventricular systolic function in 6-month follow up. This suggests that modern therapy offers suboptimal blockade of renin-angiotensin system activity in the setting of MI.

Quantitative trait loci associated with blood pressure of metabolic syndrome in the progeny of NZO/HILtJxC3H/HeJ intercrosses

In a previous study in 15 inbred mouse strains, we found highest and lowest systolic blood pressures in NZO/HILtJ mice (metabolic syndrome) and C3H/HeJ mice (common lean strain), respectively. To identify the loci involved in hypertension in metabolic syndrome, we performed quantitative trait locus (QTL) analysis for blood pressure with direction of cross as a covariate in segregating F2 males derived from NZO/HILtJ and C3H/HeJ mice. We detected three suggestive main-effect QTLs affecting systolic and diastolic blood pressures (SBP and DBP). We analyzed the first principle component (PC1) generated from SBP and DBP to investigate blood pressure. In addition to all the suggestive QTLs (Chrs 1, 3, and 8) in SBP and DBP, one suggestive QTL on Chr 4 was found in PC1 in the main scan. Simultaneous search identified two significant epistatic locus pairs (Chrs 1 and 4, Chrs 4 and 8) for PC1. Multiple regression analysis revealed three blood pressure QTLs (Bpq10, 100 cM on Chr 1; Bpq11, 6 cM on Chr 4; Bpq12, 29 cM on Chr 8) accounting for 29.4% of blood pressure variance. These were epistatic interaction QTLs constructing a small network centered on Chr 4, suggesting the importance of genetic interaction for development of hypertension. The blood pressure QTLs on Chrs 1, 4, and 8 were detected repeatedly in multiple studies using common inbred nonobese mouse strains, implying substantial QTL independent of development of obesity and insulin resistance. These results enhance our understanding of complicated genetic factors of hypertension in metabolic diseases.

Epistasis between calpain 1 and its inhibitor calpastatin within breeds of cattle

The calpain gene family and its inhibitors have diverse effects, many related to protein turnover, which appear to affect a range of phenotypes such as diabetes, exercise-induced muscle injury, and pathological events associated with degenerative neural diseases in humans, fertility, longevity, and postmortem effects on meat tenderness in livestock species. The calpains are inhibited by calpastatin, which binds directly to calpain. Here we report the direct measurement of epistatic interactions of causative mutations for quantitative trait loci (QTL) at calpain 1 (CAPN1), located on chromosome 29, with causative mutations for QTL variation at calpastatin (CAST), located on chromosome 7, in cattle. First we identified potential causative mutations at CAST and then genotyped these along with putative causative mutations at CAPN1 in >1500 cattle of seven breeds. The maximum allele substitution effect on the phenotype of the CAPN1:c.947G>C single nucleotide polymorphism (SNP) was 0.14 sigma(p) (P = 0.0003) and of the CAST:c.155C>T SNP was also 0.14 sigma(p) (P = 0.0011) when measured across breeds. We found significant epistasis between SNPs at CAPN1 and CAST in both taurine and zebu derived breeds. There were more additive x dominance components of epistasis than additive x additive and dominance x dominance components combined. A minority of breed comparisons did not show epistasis, suggesting that genetic variation at other genes may influence the degree of epistasis found in this system.

Association of AGTR1 with 18-month treatment outcome in late-life depression

OBJECTIVE

Converging lines of evidence implicate vascular factors in late-life depression, and argue that late-life depression is a distinct entity among the mood disorders. The A1166C polymorphism in the angiotensin II receptor, vascular type 1 (AGTR1) gene has been associated with a range of vascular diseases. This study investigated the association of AGTR1 genotype on 18-month treatment outcome in late-life depression.

METHODS

In a large, prospective cohort study, patients with late-life depression received individualized treatment using a standardized algorithm. The authors genotyped participants at the AGTR1 A1166C single nucleotide polymorphism (SNP) using standardized methodology, then used survival analysis to estimate the impact of A1166C and demographic variables on time to remission during 18 months of follow-up.

RESULTS

The hazard ratio for AGTR1 homozygous C/C status was 0.37. The A1166C SNP showed evidence for genotypic and allelic association in a comparison of remitted and unremitted/censored subjects.

CONCLUSION

Consistent with its association with numerous vascular disorders, AGTR1 is associated with treatment outcome in late-life depression. Further studies are needed to replicate this finding, and to investigate the impact of other genetic markers of vascular disease on late-life depression outcome.

Renin-angiotensin-aldosterone system polymorphisms: a role or a hole in occurrence and long-term prognosis of acute myocardial infarction at young age

Background

The renin-angiotensin-aldosterone system (RAAS) is involved in the cardiovascular homeostasis as shown by previous studies reporting a positive association between specific RAAS genotypes and an increased risk of myocardial infarction. Anyhow the prognostic role in a long-term follow-up has not been yet investigated.

Aim of the study was to evaluate the influence of the most studied RAAS genetic Single Nucleotide Polymorphisms (SNPs) on the occurrence and the long-term prognosis of acute myocardial infarction (AMI) at young age in an Italian population.

Methods

The study population consisted of 201 patients and 201 controls, matched for age and sex (mean age 40 ± 4 years; 90.5% males). The most frequent conventional risk factors were smoke (p < 0.001), family history for coronary artery diseases (p < 0.001), hypercholesterolemia (p = 0.001) and hypertension (p = 0.002). The tested genetic polymorphisms were angiotensin converting enzyme insertion/deletion (ACE I/D), angiotensin II type 1 receptor (AGTR1) A1166C and aldosterone synthase (CYP11B2) C-344T. Considering a long-term follow-up (9 ± 4 years) we compared genetic polymorphisms of patients with and without events (cardiac death, myocardial infarction, revascularization procedures).

Results

We found a borderline significant association of occurrence of AMI with the ACE D/I polymorphism (DD genotype, 42% in cases vs 31% in controls; p = 0.056). DD genotype remained statistically involved in the incidence of AMI also after adjustment for clinical confounders.

On the other hand, during the 9-year follow-up (65 events, including 13 deaths) we found a role concerning the AGTR1: the AC heterozygous resulted more represented in the event group (p = 0.016) even if not independent from clinical confounders. Anyhow the Kaplan-Meier event free curves seem to confirm the unfavourable role of this polymorphism.

Conclusion

Polymorphisms in RAAS genes can be important in the onset of a first AMI in young patients (ACE, CYP11B2 polymorphisms), but not in the disease progression after a long follow-up period. Larger collaborative studies are needed to confirm these results.

Pharmacogenomics of Renin Angiotensin System Inhibitors in Coronary Artery Disease

Renin Angiotensin System (RAS) inhibitors comprise some of the most commonly used medications in coronary artery disease (CAD) and its related syndromes. Unfortunately, significant inter-patient variability seems likely in response to these agents; of which, the influence of genetic determinants is of interest. This review summarizes the available RAS inhibitor pharmacogenomic studies which have evaluated RAS polymorphisms that either elucidate mechanism via surrogate endpoint measurements, or predict efficacy via clinical outcomes in CAD related syndromes.Regardless of the endpoint, none of the RAS genotypes conclusively predicts efficacy of RAS inhibitors. In fact, the results of the pharmacogenomic studies were often in direct conflict with one another. Varied results appear due to methodological limitations (e.g., inadequate study power, genotyping error, methods of endpoint measurement), study conceptualization (e.g., overestimating the contribution of polymorphism to disease, lack of haplotype approach), and differences between studies (e.g., genotype frequency, study subject characteristics, the specific medication and dose used). Thus investigators should consider the various methodological limitations to improve upon the current approach to RAS inhibitor pharmacogenomic research in the vast CAD population.

The ACE-DD genotype is associated with endothelial dysfunction in postmenopausal women

OBJECTIVE

To evaluate the effects of the angiotensin-converting enzyme (ACE) insertion/deletion (I/D), the angiotensinogen M235T and the angiotensin II type 1 receptor A1166C polymorphisms, and hormone therapy used on endothelial function in postmenopausal women without manifestation of coronary artery disease.

DESIGN

Sixty-four postmenopausal women (42 hormone therapy users and 22 hormone therapy nonusers) without clinical manifestation of coronary artery disease were evaluated using external vascular ultrasonography to measure endothelium-dependent (hyperemic response, flow-mediated dilatation) and -independent (nitroglycerin) dilatation. Genotypes were determined by polymerase chain reaction amplification.

RESULTS

Women with the ACE-DD genotype displayed a lower flow-mediated dilatation compared to those with the ACE-II genotype (8.4% +/- 3.9% vs 12.6% +/- 5.4%, P = 0.04). Endothelial function was not associated with the angiotensinogen M235T and anglotensin II type 1 receptor A1166C polymorphisms. ACE polymorphism seems to modulate endothelial function among postmenopausal women without hormone therapy (8.2% +/- 5.1% vs 18.4% +/- 5.9% for the DD and the II genotype, respectively, P = 0.02). However, in hormone therapy users, flow-mediated dilatation was similar according to the ACE genotypes.

CONCLUSIONS

Our findings suggest that ACE-I/D polymorphism is related to endothelial dysfunction in postmenopausal women. Furthermore, a potential interaction between estrogen users and ACE polymorphism on endothelial function may be present.

Angiotensin-converting enzyme gene polymorphism and allele frequencies in the lebanese population: prevalence and review of the literature

We studied the distribution of the D/D, I/D, and I/I genotypes of the angiotensin-converting enzyme (ACE) in a sample of healthy Lebanese individuals to assess their prevalence and compare them with other populations. ACE genotypes were determined using the Cardiovascular Disease (CVD) StripAssay, which is based on a Polymerase Chain Reaction-Reverse hybridization technique. DNA from 133 unrelated healthy donors from our HLA-bank was used. The prevalence of D/D, I/D, and I/I genotypes was found to be 39.1, 45.1, and 15.8% respectively, with D and I allelic frequency of 61.7 and 38.3%, respectively. The sampled Lebanese population showed ACE genotypic distributions similar to Caucasians; however, with tendency towards harboring high D allele frequency together with a low I allele frequency just like the Spanish population. This first report from Lebanon will serve as a baseline statistical data for future investigations of the prevalence of ACE genotypes in association with various clinical entities notably cardiovascular diseases. The medical literature was also reviewed in this context.

Type 1 angiotensin receptor pharmacology: signaling beyond G proteins

Drugs that inhibit the production of angiotensin II (AngII) or its access to the type 1 angiotensin receptor (AT₁R) are prescribed to alleviate high blood pressure and its cardiovascular complications. Accordingly, much research has focused on the molecular pharmacology of AT₁R activation and signaling. An emerging theme is that the AT₁R generates G protein dependent as well as independent signals and that these transduction systems separately contribute to AT₁R biology in health and disease. Regulatory molecules termed arrestins are central to this process as is the capacity of AT₁R to crosstalk with other receptor systems, such as the widely studied transactivation of growth factor receptors. AT₁R function can also be modulated by polymorphisms in the AGTR gene, which may significantly alter receptor expression and function; a capacity of the receptor to dimerize/oligomerize with altered pharmacology; and by the cellular environment in which the receptor resides. Together, these aspects of the AT₁R “flavour” the response to angiotensin; they may also contribute to disease, determine the efficacy of current drugs and offer a unique opportunity to develop new therapeutics that antagonize only selective facets of AT₁R function.

The Effect of Angiotensin II Type-1 Receptor Gene Polymorphisms on Doppler Blood Flow Parameters of Carotid and Brachial Arteries in Patients with Myocardial Infarction

BACKGROUND

Genetic influence on Doppler blood flow parameters of carotid and brachial arteries (BA) is uncertain. We investigated the relationship between the angiotensin II type-1 receptor (AT1R) gene polymorphism and the blood flow characteristics of common carotid arteries (CCA) and BA by color Doppler ultrasound (CDUS) in patients with a first anterior acute myocardial infarction (AMI).

METHODS AND RESULTS

Sixty-seven patients (15 women and 52 men), aged 25-77 years, with anterior AMI were studied. The AT1R genotypes were established. Based on the polymorphism of the AT1R, they were classified into three groups: AT1R AA genotype (Group1, n = 42 patients), AT1R AC genotype (Group 2, n = 17 patients), and AT1R CC genotype (Group 3, n = 8 patients). Peak-systolic velocity (PSV) and end-diastolic velocity (EDV) of right and left CCA, PSV of right BA, and intimal-medial thickness (IMT) of both CCA were measured by CDUS. All results evaluated statistically. The AT1R genotypes were distributed as follows: 63% AA, 25% AC, and 12% CC. PSV of BA and both CCA were higher in patients with CC and AC than AA (P < 0.05). Also, IMT of both CCA were also higher in the same groups (P < 0.05).

CONCLUSIONS

Our results suggest that AT1R gene polymorphism influences Doppler blood flow parameters of both BA and CCA, and IMT of CCA. Although further studies are required.

Renin–angiotensin system gene polymorphisms: association with susceptibility to Henoch–Schonlein purpura and renal involvement

The clinical course of Henoch-Schönlein Purpura (HSP) in children is variable, with some patients having a much more rapidly progressing course than others. We investigated whether polymorphisms of the renin-angiotensin system (RAS) genes are involved in HSP. Three RAS genotypes were examined in 114 children with HSP and in 164 healthy children: the angiotensin I converting enzyme (ACE) insertion/deletion polymorphism, the M235T mutation in the angiotensinogen gene (Agt), and the A1166C in the angiotensin II type I receptor (AT1R) gene. Significant differences were observed between HSP patients and control group in the frequency of ACE and Agt genotypes (p=0.004 and p=0.003, respectively). The TT genotype of Agt gene was associated with a 3.5-fold increased risk for Henoch-Schönlein nephritis (HSN) compared with the MM/MT genotype (odds ratio, 3.5; 95% confidence interval, 1.2-10.4). There was a trend to a higher prevalence of the TT genotype of the Agt gene among patients with nephrotic range proteinuria when compared to the patients with mild proteinuria, although the difference did not reach a statistical significance. The results of this study suggest that polymorphisms of ACE gene and Agt gene likely influence the risk of developing HSP. However, among the three genes of the RAS studies, only Agt gene was associated with the susceptibility to HSN. RAS gene polymorphisms studied are not associated with the presence of nephrotic range proteinuria. Additional studies are warranted to verify the correlation between RAS gene polymorphisms and susceptibility to HSP.

Evaluation of the angiotensin-converting enzyme insertion/deletion polymorphism and the risk of ischaemic stroke

Angiotensin-converting enzyme (ACE) gene polymorphism has been associated with increased incidence of stroke in some populations, although contradictory results have been reported. The aim of this study was to determine the allelic frequency and the genotypic distribution for ACE gene polymorphism in Turkish patients with ischemic stroke compared to appropriate healthy controls and to correlate the genetic findings with stoke type. One hundred and eight patients with ischemic stroke versus 79 healthy controls were studied for the presence of ACE gene polymorphism detected by PCR. Genotypes were defined as DD, II and ID according to the presence of the D (deletion) and I (insertion) alleles. There was no statistically significant difference in either the genotypic distribution or allelic frequency between the patients versus healthy controls (chi2 = 0.105; df = 1; p = 0.430). There was also no significant difference for ACE genotype distribution and allelic frequency within the stroke group classified according to Bamford criteria (chi2 = 4.827; df = 3; p = 0.185). Our data supports lack of association between DD genotype and/or D allele and ischemic stroke or subtypes of ischaemic stroke in the Turkish population.

Genetic variation of the renin-angiotensin system and chronic kidney disease progression in black individuals in the atherosclerosis risk in communities study

The renin-angiotensin system (RAS) regulates BP and may affect chronic kidney disease (CKD) through induction of tissue growth and fibrosis. The angiotensinogen (AGT) promoter G(-6) allele lowers transcription and is inversely associated with hypertension. In white individuals, the A1166C 3'-UTR variant of angiotensin II type 1 receptor (AT1R) has been associated with CKD. CKD associations with these RAS genes are uncertain in high-risk black populations. A prospective population-based study of CKD risk was conducted among 3706 black individuals without severe renal dysfunction at baseline (serum creatinine > or =177 micromol/L [2.0 mg/dl] for men, > or =159 micromol/L [1.8 mg/dl] for women) to examine associations with AGT and AT1R. Incident CKD progression was defined as kidney disease hospitalization or increase in serum creatinine level > or =35 micromol/L (0.4 mg/dl) above baseline. During mean follow-up of 10.2 yr, CKD progression incidence rate (per 1000 person-years) was 8.2 (n = 312 cases). Risk was lower for AGT G(-6) carriers compared with A(-6) (incidence 6.9 versus 9.0; log-rank P = 0.03) and nonsignificantly higher among AT1R C1166 carriers. Adjusting for hypertension and major CKD risk factors, AGT G(-6)decreased risk (relative risk 0.75; 95% confidence interval 0.57 to 0.98). AT1R C1166 increased risk only among those with hypertension (relative risk 1.65; 95% confidence interval 1.14 to 2.39). The AGT G(-6)A polymorphism may play a role in CKD progression in black individuals, consistent with in vitro effects on AGT levels and renal remodeling but independent of BP. The AT1R C1166 allele may increase susceptibility but only in the presence of hypertension.

Effects of Angiotensin II Type 1 Receptor Gene Polymorphisms on Insulin Resistance in a Japanese General Population: The Tanno-Sobetsu Study

Although gene polymorphisms in the renin-angiotensin system (RAS) are predisposing factors for cardiovascular diseases, the precise mechanisms and interactions among confounding factors have not been clarified. We investigated whether genetic variants of RAS are involved in insulin sensitivity in a Japanese general population. During a medical checkup in 2001, participants (n=550) were recruited from among the residents of the towns of Tanno and Sobetsu, and written informed consent was obtained to participate in the genetic analysis and the epidemiological study. The insertion/deletion (lID) polymorphism of the angiotensin-converting enzyme gene (ACE), the Met235Thr polymorphism of the angiotensinogen gene (AGT), and the A1166C polymorphism of the angiotensin II type 1 receptor gene (AGTR1) were determined by gel electrophoresis or the TaqMan PCR method. We assessed insulin sensitivity using the homeostasis model assessment insulin resistance (HOMA-IR). The RAS gene polymorphisms were not associated with log-transformed values of HOMA-IR, whereas borderline association (p=0.02) was found between the A1166C polymorphism and dichotomous categorization of insulin resistance (defined as HOMA-IR > or =1.73). Our results suggested that the A1166C polymorphism of AGTR1 might affect insulin resistance by altering the responsiveness to angiotensin II signaling, though this mechanism is as yet inconclusive. Further study is required to confirm these findings in a larger, multi-ethnic population.

Association Between A/C1166 Gene Polymorphism of the Angiotensin II Type 1 Receptor and Biventricular Functions in Patients With Acute Myocardial Infarction

BACKGROUND

Although there have been several association studies of angiotensin II type 1 receptor (AT1R, A/C1166) gene polymorphism in clinical endpoints such as myocardial infarction (MI), hypertension, aortic stiffness, and left ventricular mass, the relationship between AT1R polymorphism and biventricular function in acute anterior MI has not been studied before.

METHODS AND RESULTS

The study group comprised 132 consecutive patients who were admitted to the coronary care unit with their first acute anterior MI. Systolic and diastolic diameters, volumes, inflow properties, ejection fraction and myocardial performance index of both ventricles were measured. AT1R polymorphism was determined using polymerase chain reaction amplification. Based on A/C1166 polymorphism of AT1R, the patients were classified into 3 groups: group 1, A/A (n=91) genotype, group 2 A/C (n=28), and group 3 C/C (n=13) genotype. When the left ventricular and right ventricular echocardiographic functions were compared, all parameters of the 3 groups were found to be similar. No difference was detected in either the genotype distribution or allele frequencies between the patients and the controls for AT1R.

CONCLUSIONS

The results suggest that A/C1166 polymorphism of AT1R did not influence the risk of either acute MI or biventricular function after anterior MI.

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.

ACE-DD genotype is associated with the occurrence of acute coronary syndrome in postmenopausal women

The insertion/deletion (I/D) polymorphism of the angiotensin converting enzyme (ACE), the A1166C polymorphism in the angiotensin type 1 receptor (AT1R), and the M235T polymorphism of the angiotensinogen gene are associated with cardiovascular disease mostly in men. Few data are available on the effects of these genetic variations in postmenopausal women according to hormone replacement therapy (HRT) use. In this case-control study, we determine the frequency of mutant alleles in the ACE I/D, M235T and A1166C polymorphisms in postmenopausal Caucasian women with and without a diagnosis of acute coronary syndrome (ACS). Data from 198 women with ACS (63+/-10 years) and 149 controls (62+/-7 years) showed that ACE-DD genotype was more prevalent in women with ACS compared to controls (30% vs. 19%, P<0.05). There was no difference in genotype distributions for either the M235T or the A1166C polymorphisms between groups. The difference in ACE genotype distribution between ACS women and controls was driven by current HRT users with 30% of ACS and 15% of controls carrying the ACE-DD genotype (P<0.05). The oligenic combination of ACE-DD and M235T-TT genotypes was higher in ACS compared to controls. Among carriers of M235T-TT, 7% of ACS and 1% of controls also had the ACE-DD genotype, P<0.05. Thus, the ACE-DD genotype may be associated with ACS in postmenopausal women, particularly in HRT users.

Negative epistasis between the malaria-protective effects of alpha+-thalassemia and the sickle cell trait

The hemoglobinopathies, disorders of hemoglobin structure and production, protect against death from malaria. In sub-Saharan Africa, two such conditions occur at particularly high frequencies: presence of the structural variant hemoglobin S and alpha(+)-thalassemia, a condition characterized by reduced production of the normal alpha-globin component of hemoglobin. Individually, each is protective against severe Plasmodium falciparum malaria, but little is known about their malaria-protective effects when inherited in combination. We investigated this question by studying a population on the coast of Kenya and found that the protection afforded by each condition inherited alone was lost when the two conditions were inherited together, to such a degree that the incidence of both uncomplicated and severe P. falciparum malaria was close to baseline in children heterozygous with respect to the mutation underlying the hemoglobin S variant and homozygous with respect to the mutation underlying alpha(+)-thalassemia. Negative epistasis could explain the failure of alpha(+)-thalassemia to reach fixation in any population in sub-Saharan Africa.

Polymorphisms of the renin-angiotensin system and the severity of fibrosis in chronic hepatitis C virus infection

Patients with chronic hepatitis C virus (HCV) infection vary in their rates of fibrosis progression. The renin-angiotensin system (RAS) regulates fibrosis. Polymorphisms in the genes of the RAS may contribute to the outcome of renal and cardiovascular disease. We studied four RAS gene polymorphisms in 195 patients with chronic HCV infection. Patients were grouped by Ishak stage of fibrosis on liver biopsy: group 1 (fibrosis score 0 or 1; n = 97), group 2 (fibrosis score 2 or 3; n = 73) and group 3 (fibrosis score 4-6; n = 25). Polymorphisms of the angiotensinogen (AGT) gene (M235T and AT-6), the angiotensin I converting enzyme gene and the type 1 angiotensin II receptor gene were assayed. There was no difference in the distribution of these polymorphisms of the RAS between the fibrosis groups. There did not appear to be any increased prevalence of fibrosis if two or even three of the polymorphisms associated with increased RAS effect were present. On multivariate analysis factors significantly associated with fibrosis were necroinflammatory activity (P < 0.001) and age (P < 0.001). No association was identified between these four RAS polymorphisms and fibrosis in chronic HCV infection.

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.

Genetic contribution to the acute effects of angiotensin II type 1 receptor blockade

OBJECTIVE

Clinical observations point towards heterogeneity in patients' responses to antihypertensive drugs. As our earlier work showed that angiotensin II (AngII) sensitivity is associated with the A1166C polymorphism of the AngII type 1 receptor (AT1R) gene, we conducted the present study in which the responses to acute AT1R blockade were evaluated.

METHODS

After 7 days of low and high sodium diet, the hormonal as well as systemic and renal hemodynamic responses to acute AT1R blockade with EXP3174 (active metabolite of losartan) were studied in 15 AA and 14 CC essential hypertensive patients. By means of platelet-binding studies the baseline AT1R density (Bmax) and affinity (KD) was tested.

RESULTS

During low and high salt diet, baseline Bmax and KD were comparable between both genotype groups. At baseline, during low salt diet, CC patients had significantly lower glomerular filtration rate and a trend towards lower effective renal plasma flow (ERPF) compared to AA patients. Blood pressure responses to EXP3174 during high salt were significantly blunted in CC patients compared to AA patients (mean arterial pressure: 1.8 versus 7.5%; P < 0.05). During low salt the increase in ERPF (12.9 versus 16.1%; P = 0.08), as well as the decrease in filtration fraction (9.0 versus 14.0%; P = 0.05) and renal vascular resistance (7.5 versus 15.1%; P = 0.06) were blunted in CC patients compared to AA patients. Humoral effects did not differ between the groups.

CONCLUSION

This study shows that the systemic and renal hemodynamic responses to acute AT1R blockade are, at least in part, genetically determined.

Polymorphism in angiotensin II receptor genes and hypertension

Molecular variants of individual components of the renin-angiotensin system (RAS) have been thought to contribute to an inherited predisposition towards essential hypertension. The angiotensin II type 1 receptor (AT-1) mediates the major pressor and trophic actions of angiotensin II (Ang II) and at least 50 different polymorphisms have been described in the AT-1 gene (AT(1)R gene); in particular, the C allele of the +1166A/C polymorphism has been associated with the severe form of essential hypertension, but the role of this polymorphism is still ambiguous in pathologies related to high Ang II levels, such as deterioration of renal function, arterial stiffness and hypertrophic cardiomyopathy. A relationship was suggested between AT 1R A1166C polymorphism and the humoral and renal haemodynamic responses to losartan, an AT-1 blocker, as well as with enhanced Ang II vascular reactivity or sensitivity. Polymorphism has also been described in angiotensin II type 2 receptor (AT-2) gene, AT-2 being the mediator for vasodilatation, natriuresis and apoptosis of smooth muscle cells; associations were found between some of these polymorphisms and both hypertension and left ventricular structure. Further evaluation in adequately powered studies is necessary for full assessment of the allelic markers in genes for RAS components, as well as to allow determination of a predisposition to hypertension or related diseases and selection of an appropriate antihypertensive drug for an individual.

The paradoxical association of common polymorphisms of the renin-angiotensin system genes with risk of myocardial infarction

BACKGROUND

The insertion/deletion polymorphism of the angiotensin-converting enzyme (ACE) and the A1166C polymorphism of the angiotensin-II AT1 receptor (AT1R) have been extensively investigated as possible risk factors for myocardial infarction (MI).

DESIGN AND METHODS

Genetic association, case-control study, specifically designed to investigate the association of the above-mentioned polymorphisms with risk of MI in a homogeneous, low coronary risk, Caucasian population. The study population consisted of 1603 consecutive patients with acute MI who were recruited from nine clinics, located in three cities, and 699 unrelated adults who were randomly selected from the city catalogues.

RESULTS

In univariate analysis, the DD genotype was found to be more prevalent among controls (40.8 vs. 35.2%, P=0.011). In multivariate analysis adjusted for age, gender, smoking status, diabetes mellitus, hypercholesterolaemia, hypertension and family history of coronary artery disease, the presence of the DD genotype was independently and negatively associated with risk of AMI (RR=0.743, 95% CI=0.595-0.927, P=0.008). The CC genotype was not found to be significantly associated with risk of MI, either in univariate (6.2 vs. 6.4%, P=0.856), or in multivariate analysis adjusted for the same confounders (RR=0.743, 95% CI=0.473-1.167, P=0.197).

CONCLUSIONS

Contrary to previous reports, in this study the DD genotype of the ACE gene, but not the CC genotype of the AT1R gene, was associated with a lower risk of MI. Our results emphasize the complexity of genotype-phenotype interactions in the pathogenesis of ischaemic heart disease and question the previously hypothesized role of the DD genotype on risk of acute myocardial infarction.

Links between dietary salt intake, renal salt handling, blood pressure, and cardiovascular diseases

Epidemiological, migration, intervention, and genetic studies in humans and animals provide very strong evidence of a causal link between high salt intake and high blood pressure. The mechanisms by which dietary salt increases arterial pressure are not fully understood, but they seem related to the inability of the kidneys to excrete large amounts of salt. From an evolutionary viewpoint, the human species is adapted to ingest and excrete <1 g of salt per day, at least 10 times less than the average values currently observed in industrialized and urbanized countries. Independent of the rise in blood pressure, dietary salt also increases cardiac left ventricular mass, arterial thickness and stiffness, the incidence of strokes, and the severity of cardiac failure. Thus chronic exposure to a high-salt diet appears to be a major factor involved in the frequent occurrence of hypertension and cardiovascular diseases in human populations.