Epistatic interaction between variations in the angiotensin I converting enzyme and angiotensin II type 1 receptor genes in relation to extent of coronary atherosclerosis

Association of AGTR1 (A1166C) and ACE (I/D) Polymorphisms with Breast Cancer Risk in North Indian Population

Renin angiotensin system (RAS) comprising Angiotensin converting enzyme (ACE), Angiotensin II (Ang II) and its receptor Angiotensin II receptor type I (AGTR1), plays a critical role in several diseases including cancer. A single nucleotide polymorphism (SNP) A1166C located in 3' untranslated region (UTR) of AGTR1 and an insertion/deletion (I/D) polymorphism present in intron 16 of ACE gene have been associated with many diseases, but their association with Breast cancer (BCa) is still debatable. Here, we for the first time investigated the association of these polymorphisms in a North Indian BCa cohort including 161 patients and 152 healthy women. The polymorphisms were evaluated by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) respectively. The association between these polymorphisms and BCa risk was estimated by calculating Odds Ratio (OR) and chi-square (χ2) test. The DD genotype/D allele of ACE (I/D) polymorphism and "AC and CC" genotype/C allele of AGTR1 (A1166C) polymorphism were associated with higher risk of BCa when evaluated independently. Furthermore, interaction analysis of "AC and CC" and DD genotype and combination of "C and D" alleles of both polymorphisms revealed significantly greater BCa risk than that observed independently. Conclusively, women harboring "AC or CC" genotype/C allele for AGTR1 (A1166C) polymorphism and DD genotype/D allele for ACE (I/D) polymorphisms have a predisposition to develop more aggressive disease with advanced staging and larger tumor size. Our study indicates importance of genetic screening based on these polymorphisms for women, who may have higher risk of BCa.

Association between the Angiotensin-Converting Enzyme (ACE) Genetic Polymorphism and Diabetic Retinopathy-A Meta-Analysis Comprising 10,168 Subjects

Aims-to address the inconclusive findings of the association of angiotensin-converting enzyme (ACE) insertion/deletion (I/D) polymorphism on risk of diabetic retinopathy (DR), a meta-analysis was conducted. Methods-we conducted a meta-analysis on 4252 DR cases and 5916 controls from 40 published studies by searching electronic databases and reference lists of relevant articles. A random-effects or fixed-effects model was used to estimate the overall and stratification effect sizes on ACE I/D polymorphism on the risk of DR. Results-we found a significant association between the ACE I/D polymorphism and the risk of DR for all genetic model (ID vs. II: OR = 1.14, 95% CI: 1.00-1.30; DD vs. II: OR = 1.38, 95% CI: 1.11-1.71; Allele contrast: OR = 1.17, 95% CI: 1.05-1.30; recessive model: OR = 1.24, 95% CI: 1.02-1.51 and dominant model: OR = 1.21, 95% CI: 1.06-1.38, respectively). In stratified analysis by ethnicity and DM type, we further found that the Asian group with T2DM showed a significant association for all genetic models (ID vs. II: OR = 1.14, 95% CI: 1.01-1.30; DD vs. II: OR = 1.54, 95% CI: 1.14-2.08; Allele contrast: OR = 1.26, 95% CI: 1.09-1.47; recessive model: OR = 1.42, 95% CI: 1.07-1.88 and dominant model: OR = 1.26, 95% CI: 1.07-1.49, respectively). Conclusion-our study suggested that the ACE I/D polymorphism may contribute to DR development, especially in the Asian group with type 2 diabetes mellitus (T2DM). Prospective and more genome-wide association studies (GWAS) are needed to clarify the real role of the ACE gene in determining susceptibility to DR.

Genetic polymorphisms of the renin-angiotensin system in preterm delivery and premature rupture of membranes

Introduction. Premature rupture of membranes (PRM) is a late pregnancy complication commonly associated with preterm delivery (PD).Although several markers related to the renin-angiotensin system (RAS) have been evaluated in certain pregnancy complications, only the angiotensin-converting enzyme (ACE) I/D variant has been studied in PD-PRM.The aim of this survey was to investigate the association of the polymorphisms (angiotensin II type 1 [AT1] receptor T174M and M235T, renin G2805A,ACE I/D and AT1-receptor A1166C) of the genes of RAS in women with PD-PRM.

Design. Deoxyribonucleic acid samples from 89 Mexican Mestizo women with PD and PRM and 224—288 controls were studied. Polymorphisms were analysed by polymerase chain reaction-sequence specific primer assays. restricted fragment length polymorphism or sequence specific prim assays.

Results. For all loci , genotype distribution was in agreement with Hardy—Weinberg expectations in the control group. Significant intergroup difference (case vs. control) was seen for angiotensinogen (AGT) M235T polymorphism, with an increased allele M235 in affected cases (50% vs. 40% in controls).Analysis of two- locus haplotype agrees with an independent segregation of physically unlinked genes. Haplotype AGT 174T-235M was also increased (50 % vs. 40% in controls).

Conclusions. Physically unlinked genes involved in RAS segregate independently. The AGT 174—235 region is associated with PD-PRM in this population.

High Incidence of ACE/PAI-1 in Association to a Spectrum of Other Polymorphic Cardiovascular Genes Involving PBMCs Proinflammatory Cytokines in Hypertensive Hypercholesterolemic Patients: Reversibility with a Combination of ACE Inhibitor and Statin

Cardiovascular diseases (CVDs) are significantly high in the Lebanese population with the two most predominant forms being atherosclerosis and venous thrombosis. The purpose of our study was to assess the association of a spectrum of CVD related genes and combined state of hypertension hypercholesterolemia (HH) in unrelated Lebanese. Twelve polymorphisms were studied by multiplex PCR and reverse hybridization of DNA from 171 healthy individuals and 144 HH subjects. Two genes were significantly associated with HH: ACE (OR: 9.20, P<0.0001) and PAI-1 (OR: 2.29, P = 0.007), respectively with the occurrence of the risky alleles “Del” and “4G”. The frequencies of the Del and 4G alleles were found to be 0.98 and 0.90 in the HH group versus 0.84 and 0.79 in the healthy group, respectively. Serum ACE activity and PAI-I increased significantly with Del/Del and 4G/5G genotypes. The co-expression of Del/4G(+/+) was detected in 113 out of 171 (66.0%) controls and 125 out of 144 (86.8%) HH subjects. Del/4G(-/-) was detected in only 6 (3.5%) controls and undetected in the HH group. Three venous thrombosis related genes [FV(Leiden), MTHFR(A1298C) and FXIII(V34L)] were significantly related to the prominence of the co-expression of Del/4G(+/+). A range of 2 to 8 combined polymorphisms co-expressed per subject where 5 mutations were the most detected. In Del/4G(+/+) subjects, peripheral blood mononuclear cells (PBMCs) produced significant elevated levels of IFN-γ and TNF-α contrary to IL-10, and no variations occurred for IL-4. ACE inhibitor (ramipril) in combination with statin (atorvastatin) and not alone reversed significantly the situation. This first report from Lebanon sheds light on an additional genetic predisposition of a complex spectrum of genes involved in CVD and suggests that the most requested gene FVL by physicians may not be sufficient to diagnose eventual future problems that can occur in the cardiovascular system. Subjects expressing the double mutations (Del/4G) are at high risk for the onset of CVDs.

Angiotensin converting enzyme gene polymorphism is associated with severity of coronary artery disease in men with high total cholesterol levels

This study examines whether renin-angiotensin-aldosterone system gene polymorphisms: ACE (encoding for angiotensin converting enzyme) c.2306-117_404 I/D, AGTR1 (encoding for angiotensin II type-1 receptor) c.1080*86A>C and CYP11B2 (encoding for aldosterone synthase) c.-344C>T are associated with the extension of coronary atherosclerosis in a group of 647 patients who underwent elective coronary angiography. The extension of CAD was evaluated using the Gensini score. The polymorphisms were determined by PCR and RFLP assays. The associations between genotypes and the extent of coronary atherosclerosis were tested by the Kruskal-Wallis test, followed by pairwise comparisons using Wilcoxon test. The population has been divided into groups defined by: sex, smoking habit, past myocardial infarction, BMI (>, ≤ 25), age (>, ≤ 55), diabetes mellitus, level of total cholesterol (>, ≤ 200 mg/dl), LDL cholesterol (>, ≤ 130 mg/dl), HDL cholesterol (>, ≤ 40 mg/dl), triglycerides (>, ≤ 150 mg/dl). Significant associations between the ACE c.2306-117_404 I/D polymorphism and the Gensini score in men with high total cholesterol levels (P(Kruskal-Wallis) = 0.008; P(adjusted) = 0.009), high level of LDL cholesterol (P(Kruskal-Wallis) = 0.016; P(adjusted) = 0.028) and low level of HDL cholesterol (P(Kruskal-Wallis) = 0.04; P(adjusted) = 0.055) have been found. No association between the AGTR1 c.1080*86A>C and CYP11B2 c.-344C>T and the Gensini score has been found. These results suggest that men who carry ACE c.2306-117_404 DD genotype and have high total cholesterol, high LDL cholesterol and low HDL cholesterol levels may be predisposed to the development of more severe CAD.

The epistasis between vascular homeostasis genes is apparent in essential hypertension

OBJECTIVE

The epistasis influence of vascular homeostasis genes is vital to multigenetic diseases. This study was designed to perceive the possible role of epistasis in the etiology of essential hypertension.

METHODS

We investigated seven polymorphisms of ACE, CYP11B2 and NOS3 epistatically, and SBP, DBP, MAP, ACE activity, plasma aldosterone concentration (PAC) and NOx level in 860 age- and ethnicity-matched unrelated north-Indian subjects.

RESULTS

The hypertension risk in individuals with interacted-genotypes (IwIw+IwIc)+(4aa), (IcIc)+(4bb+4ba) and IcIc+4aa of the CYP11B2 and NOS3 was significantly higher with odds ratio 5.5 (95% CI=2.9-10.6, P<0.0001), 2.4 (95% CI=1.4-4.1, P<0.0008) and 7.5 (95% CI=1.6-34.8, P=0.010), respectively. The odds ratio for hypertension with interacted-haplotypes (-344T/Ic)+(-922A/-786T/4a/894G) and (-344T/Ic)+(-922G/-786C/4a/894G) of CYP11B2 and NOS3 was 5.3 (95% CI=2.0-14.2, P=0.005) and 3.9 (95% CI=1.4-10.4, P=0.04), respectively; whereas for the protective interacted-haplotypes (-344T/Iw)+(-922A/-786T/4b/894G), the odds ratio was 0.7 (95% CI=0.5-0.9, P=0.03). While the interacted-genotypes, IcIc+4aa correlated with higher SBP and MAP (P=0.006; P=0.04), the interacted-haplotypes, (-344T/Ic)+(-922A/-786T/4a/894G) and (-344T/Ic)+(-922G/-786C/4a/894G) correlated with higher MAP and lower NOx level (P=0.02 and P=0.03, respectively), and the protective interacted-haplotypes (-344T/Iw)+(-922A/-786T/4b/894G) correlated with lower PAC and MAP (P=0.024 and P=0.018, respectively).

CONCLUSIONS

The epistasis between CYP11B2 and NOS3 and its correlation with varied clinical and biochemical parameters signify its possible contribution in the complex etiology of hypertension.

Angiotensin-converting enzyme gene polymorphism is associated with proliferative diabetic retinopathy: a meta-analysis

The association of angiotensin-converting enzyme (ACE) gene polymorphism with diabetic retinopathy (DR) was investigated in many studies with conflicting results. To shed light on these inconclusive findings, a meta-analysis of all available studies relating I (insert)/D (delete) polymorphism to the risk of developing DR was conducted. This meta-analysis included genotype data on 2,342 cases with DR and 2,048 controls free of DR. Summary odds ratios were estimated. Potential sources of heterogeneity and bias were explored. Overall, in allelic genetic model, heterogeneity between studies was nonsignificant (P = 0.12). No publication bias was observed in the regression asymmetry test (τ = 0.84, P = 0.41). There was no significant association between this variant and DR. In additional analysis, the association of I/D variant with retinopathy was nonsignificant both in patients with type 1 diabetes (T1D) (1.01 [95% CI: 0.79-1.29]) and in patients with type 2 diabetes (T2D) (1.12 [95% CI: 0.93-1.35]). Significant association was not also observed between I/D variant and the background diabetic retinopathy (BDR). For the I/D polymorphism and its relationship to proliferative diabetic retinopathy (PDR), the dominant model showed nonsignificant heterogeneity among studies (P = 0.52; I (2) = 0%), and the fixed estimate pooled odd ratio (OR) JOP was significant, at 1.37 [95% CI: 1.02-1.84]. No association was observed between ACE I/D variant and DR, irrespective of the diabetic type. There was moderate evidence of its relationship to PDR, while its relationship to BDR was not found. Studies exploring the association between ACE I/D polymorphism and BDR or PDR may help us better understand the genetics of DR.

Angiotensin-converting enzyme gene polymorphism is associated with type 2 diabetes: a meta-analysis

The association of angiotensin-converting enzyme gene polymorphism with type 2 diabetes was investigated in many studies with conflicting results. To clarify this conflict, we performed a meta-analysis on recent previous reports on ACE gene polymorphism and its correlation to type 2 diabetes. A total of 15,166 subjects from 24 studies were included in this meta-analysis. Summary odds ratios (ORs) were estimated. Potential sources of heterogeneity and bias were explored. The D variant was associated with a 14% increased risk of T2D relative to the I variant (OR 1.14; 95% CI: 1.04-1.24). In subgroup analysis, Caucasian and East Asians showed significant association. No association was found in the Turkish groups. No publication bias was observed in this meta-analysis by using the Egger method (tau = 1.63, P = 0.12), as well as the Begg's test (z = 1.66, P = 0.10). Cumulative meta-analysis for the allelic contrast showed a trend of association as information accumulated. These data suggested that the variant of ACE I/D had a moderate positive association with type 2 diabetes.

Interaction of G-protein beta3 subunit and nitric oxide synthase gene polymorphisms on carotid artery intima-media thickness in young adults: the Bogalusa Heart Study

BACKGROUND

G-protein beta3 subunit (GNB3) gene C825T and endothelial nitric oxide (eNOS) gene G894T polymorphisms both influence arterial structure and function. However, information is scant regarding the interaction of these genes on arterial wall thickness.

METHODS

This aspect was examined in 654 white and black subjects, aged 25-43 years (72.9% white, 39.3% male). Arterial wall thickness was assessed in terms of the average intima-media thickness (IMT) of common carotid, internal carotid, and carotid bulb segments by B-mode ultrasonography.

RESULTS

Frequencies of T allele of the GNB3 C825T polymorphism (0.718 vs. 0.304, P < 0.0001) and G allele of the eNOS G894T polymorphism (0.868 vs. 0.661, P < 0.0001) were higher in blacks compared to whites. In a multivariate model including gender, age, mean arterial pressure, body mass index, triglycerides/HDL cholesterol ratio, insulin resistance index, smoking, and/or race, there was no significant genotypic effect on carotid IMT with respect to GNB3 C825T or eNOS G894T polymorphisms among whites, blacks, and total sample. However, the carriers of TT genotype of the GNB3 C825T and T allele of the eNOS G894T had a significantly lower carotid IMT among blacks (P = 0.003) and the total sample (P = 0.006).

CONCLUSION

These results indicate that the genetic variations of the eNOS gene in combination with the GNB3 gene jointly influence carotid artery wall thickening process in young adults, especially in blacks.

Parallel effects of genetic variation in ACE activity in baboons and humans

Like humans, savannah baboons (Papio sp.) show heritable interindividual variation in complex physiological phenotypes. One prominent example of such variation involves production of the homeostatic regulator protein angiotensin converting enzyme (ACE), which shows heritable variation in both baboons and humans. In humans, this phenotypic variation is associated with an Alu insertion-deletion polymorphism in the ACE gene, which explains approximately half of the variation in serum ACE activity. We identified a similar Alu insertion-deletion polymorphism in the baboon ACE homologue and measured its frequency in a wild population and a captive population of baboons. We also analyzed the contribution of ACE genotype at this indel to variation in serum ACE activity in the captive population. When conditioned on weight, a known factor affecting ACE activity in humans, age and ACE genotype both accounted for variance in ACE activity; in particular, we identified a significant nonadditive interaction between age and genotype. A model incorporating this interaction effect explained 21.6% of the variation in residual serum ACE activity. Individuals homozygous for the deletion mutation exhibited significantly higher levels of ACE activity than insertion-deletion heterozygotes at younger ages (10-14 years), but showed a trend towards lower levels of ACE activity compared with heterozygotes at older ages (> or =15 years). These results demonstrate an interesting parallel between the genetic architecture underlying ACE variation in humans and baboons, suggesting that further attention should be paid in humans to the relationship between ACE genetic variation and aging.

Detection of gene x gene interactions in genome-wide association studies of human population data

Empirical evidence supporting the commonality of gene x gene interactions, coupled with frequent failure to replicate results from previous association studies, has prompted statisticians to develop methods to handle this important subject. Nonparametric methods have generated intense interest because of their capacity to handle high-dimensional data. Genome-wide association analysis of large-scale SNP data is challenging mathematically and computationally. In this paper, we describe major issues and questions arising from this challenge, along with methodological implications. Data reduction and pattern recognition methods seem to be the new frontiers in efforts to detect gene x gene interactions comprehensively. Currently, there is no single method that is recognized as the 'best' for detecting, characterizing, and interpreting gene x gene interactions. Instead, a combination of approaches with the aim of balancing their specific strengths may be the optimal approach to investigate gene x gene interactions in human data.

Exploring joint effects of genes and the clinical efficacy of morphine for cancer pain: OPRM1 and COMT gene

Pain is a complex human trait. It is likely that the interaction of multiple genes, each with a small individual effect, along with the effect of environmental factors, influences the clinical efficacy of opioids rather than a single gene alone. Polymorphisms in genes coding for the mu-opioid receptor (A118G) and catechol-O-methyl transferase (Val158Met) may be important modulators of opioid efficacy. We assessed joint effects of the OPRM1 and COMT genes in predicting morphine dose for cancer pain relief. We used genotype and clinical data from a pharmacokinetic study of morphine in 207 inpatients treated with stable morphine dose for at least 3 days by Palliative Medicine Specialists. Results showed significant variation in morphine dose requirement by genotype groups: carriers of COMT Val/Val and Val/Met genotype required 63% and 23%, respectively, higher morphine dose compared to carriers of Met/Met genotype (p=0.02). Carriers of OPRM1 GG genotype required 93% higher morphine dose compared to carriers of AA genotypes (p=0.012). When we explored for joint effects, we found that carriers of the OPRM1 AA and COMT Met/Met genotype required the lowest morphine dose to achieve pain relief (87 mg/24 h; 95%CI=57,116) and those with neither Met/Met nor AA genotype needed the highest morphine dose (147 mg/24 h; 95%CI=100,180). The significant joint effects for the Met/Met and AA genotypes (p<0.012) persisted, even after controlling for demographic and clinical variables in the multivariable analyses. Future studies are needed to further characterize the joint effects of multiple genes, along with demographic and clinical variables, in predicting opioid dose.

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.

Angiotensin II type I receptor gene polymorphism: anthropometric and metabolic syndrome traits

BACKGROUND

The renin angiotensin system is important in the regulation of vascular tone and fluid and electrolyte balance. The angiotensin converting enzyme gene (ACE) genotype has been shown to affect exercise response and glucose load response dependent on birth weight. Angiotensin II type I receptor (AGTR1) A1166C has previously been associated with the development of hypertension and coronary disease, but its metabolic effects have not been investigated.

METHOD

AGTR1 A1166C was genotyped by allele specific PCR in 378 individuals from Hertfordshire, UK, who had been characterised for metabolic syndrome traits.

RESULTS

Genotype counts were: AA, 183; AC, 170; CC, 25, consistent with Hardy-Weinberg equilibrium. The CC genotype was associated with significantly lower body mass index (by 1.7 units) in men (p = 0.03), and the same magnitude effect in women with significant lower weight in both genders (p = 0.01), also lower waist circumference and waist-hip ratio (p = 0.01) in men, with a trend for lower waist circumference in women also. Additionally, the CC genotype and/or C allele was associated with lower fasting glucose and insulin, and 30 and 120 min glucose in men (respectively, p = 0.08, 0.04, 0.01, 0.06). Lower means of systolic blood pressure, pulse pressure, cholesterol, and fasting triglyceride were also observed for the CC genotype in both genders though these were not statistically significant.

CONCLUSIONS

The AGTR1 1166 CC genotype appears to predispose to favourable anthropometric and metabolic traits, relative to cardiovascular risk.

Genetic variants predisposing to cardiovascular disease

PURPOSE OF REVIEW

The goal of this review is to provide an update on the most recent and relevant findings in the area of genotype-phenotype associations as well as the relationships between genetic factors and cardiovascular disease risk markers and events. In addition, emphasis will be placed on the methodological problems associated with studying the genetics of complex disorders, specifically cardiovascular diseases.

RECENT FINDINGS

Genes associated with cardiovascular disease predisposition have been examined, including traditional cardiovascular disease candidate genes, such as ACE, AGT, eNOS, PON and MTHFR, new loci that have recently been added to the growing list of cardiovascular disease candidate genes (i.e. MEF2A, ALOX5, LTA, APOM, PDE4D), and genes that have been shown to be at the intersection of several age-related disorders through interaction with one another or with environmental factors (i.e. APOA5, APOE, PPARgamma, LPL and LIPC).

SUMMARY

During the last year, tremendous effort has been made in elucidating new genes associated with cardiovascular disease predisposition. For the most part, however, major breakthroughs have not been made, primarily due to the poor replication of results among studies, as a consequence of poor experimental design. Nevertheless, we have increased our understanding of the complexity of cardiovascular disease and the relevance of gene-environment interactions as the ultimate drivers of the individual predisposition to the disease. It is essential, therefore, that present and future genetic studies in this area take into consideration the inclusion of high-quality environmental data in the analytical process to test the clinical usefulness of a genetic marker as a risk predictor.

Genetic polymorphisms of the renin-angiotensin system in end-stage renal disease

BACKGROUND

End-stage renal disease (ESRD) is a complex phenotype resulting from underlying kidney diseases of different etiologies as well as from environmental and genetic factors. The responsible genes influencing the development and rate of progression to ESRD have yet to be defined. We examined an association of the three renin-angiotensin system (RAS) gene polymorphisms with renal disease and progression to ESRD in dialyzed patients.

METHODS

Genotyping was performed in 745 ESRD patients and 520 control subjects for the angiotensin-converting enzyme (ACE) I/D, angiotensinogen (AGT) M235T and angiotensin II type 1 receptor (AT1R) A1166C gene polymorphisms using polymerase chain reaction and gel analysis.

RESULTS

Allele and genotype frequencies of the ACE polymorphism did not differ significantly between ESRD patients and controls. The patient group showed an increased frequency of the T allele of the AGT polymorphism (P = 0.02) and the C allele and CC genotype of the AT1R polymorphism (P<0.01). There was an association of the AT1R gene polymorphism with the progression of renal disease to end-stage failure. The time from diagnosis to the onset of ESRD was significantly shorter in patients carrying the C allele than in subjects with the homozygous AA genotype (4.7 years vs 12.6 years, P<0.001). The observed effect was not associated with hypertension in studied subjects.

CONCLUSION

The results of our study demonstrate the association between the AT1R A/C polymorphism and renal disease progression. The CC/AC genotype of this polymorphism might serve as a predictor for early ESRD and might be useful in planning therapeutic strategies for individual patients.

Exonization of AluYa5 in the human ACE gene requires mutations in both 3' and 5' splice sites and is facilitated by a conserved splicing enhancer

Ancient Alu elements have been shown to be included in mature transcripts by point mutations that improve their 5′ or 3′ splice sites. We have examined requirements for exonization of a younger, disease-associated AluYa5 in intron 16 of the human ACE gene. A single G>C transversion in position −3 of the new Alu exon was insufficient for Alu exonization and a significant inclusion in mRNA was only observed when improving several potential splice donor sites in the presence of 3′ CAG. Since complete Alu exonization was not achieved by optimizing traditional splicing signals, including the branch site, we tested whether auxiliary elements in AluYa5 were required for constitutive inclusion. Exonization was promoted by a SELEX-predicted heptamer in Alu consensus sequence 222–228 and point mutations in highly conserved nucleotides of this heptamer decreased Alu inclusion. In addition, we show that Alu exonization was facilitated by a subset of serine/arginine-rich (SR) proteins through activation of the optimized 3′ splice site. Finally, the haplotype- and allele-specific ACE minigenes generated similar splicing patterns in both ACE-expressing and non-expressing cells, suggesting that previously reported allelic association with plasma ACE activity and cardiovascular disease is not attributable to differential splicing of introns 16 and 17.

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.

Angiotensin II type I receptor gene and myocardial infarction

OBJECTIVES

The present study aimed to assess the effect of haplotype variation in angiotensin II type I receptor (AGTR1) gene on the risk of myocardial infarction (MI) in Chinese males.

METHODS

We used 48 patients to identify the putative functional polymorphisms in AGTR1 gene by direct sequencing. The program tagSNPs was used to identify an optimal set of tagging single nucleotide polymorphisms (SNPs). These selected SNPs were then genotyped in 419 male patients with MI and 400 age-matched male controls. The program haplo.stats was used to investigate the relationship between the haplotypes and MI.

RESULTS

Sixteen polymorphisms in AGTR1 gene were identified. Based on the linkage disequilibrium pattern among these SNPs, six polymorphisms, SNP1, SNP6-SNP7 and SNP13-SNP15, were selected as haplotype tagging SNPs and further genotyped. Single SNP analyses indicated that the SNP1, SNP6 and SNP13 were significantly associated with MI, adjusted for covariates. Haplotype-based association analyses identified the frequency of haplotype AGATAA was lower in cases than in controls (P = 0.006). In comparison, three haplotypes (AAATAA, TAGCAA and AAACAG) were found to significantly increase the risk of MI with adjusted odds ratio equal to 1.33, 1.75 and 2.64, respectively (P = 0.029, 0.026 and 0.015).

CONCLUSIONS

Our study suggests that common genetic variations in the AGTR1 gene may affect the risk of MI in Chinese males, and that there might be several functional variants in AGTR1 gene and the combined effect of these variants seemed to have a larger effect on the risk of MI in Chinese males.

Angiotensin in atherosclerosis

PURPOSE OF REVIEW

While it is well established that angiotensin II promotes cardiovascular and renal disorders, recent evidence has indicated a pivotal role in atherosclerotic disease which is distinguished by the central abnormality of lipid accumulation within the vascular wall.

RECENT FINDINGS

Studies published in the last year show that angiotensin II activity is increased in atherosclerosis, but even a transient elevation in angiotensin II potentiates the disease. The downstream hormone, aldosterone, has vasculopathic effects in conjunction with, as well as independently of, angiotensin II. The mechanism for angiotensin II injury includes potentiation of damage by known risk factors such as hypertension, hyperlipidemia, diabetes and insulin resistance, falling estrogens and inflammation. In addition, angiotensin II has direct effects on cellular proliferation, hypertrophy, apoptosis, and synthesis/degradation of matrix proteins and collagen that underlie development and progression of atherosclerosis as well as stability of the plaque. Antagonism of angiotensin II actions, therefore, offers the possibility of interfering with these direct and indirect effects and lessening the progression of atherosclerosis, stabilizing vulnerable plaques, and even reversing the disease.

SUMMARY

Angiotensin is increased in atherosclerosis, and increased angiotensin II amplifies atherosclerosis by modulating individual risk factors as well as by directly affecting lipid metabolism, the vascular response to lipid accumulation, and plaque stability. Antagonism of angiotensin II actions not only lessens the progression of atherosclerosis, but stabilizes the plaque and may even cause regression of the disease.

Angiotensin-converting enzyme gene insertion/deletion polymorphism in children with Henoch-Schonlein purpua nephritis

This study investigated the relationship between angiotensin-converting enzyme (ACE) gene insertion/deletion polymorphism and the occurrence, severity, prognosis of HSPN. The polymorphism of ACE gene in 103 HSPN cases and 100 healthy children was studied by using the polymerase chain reactions (PCR). Its relation to the clinical manifestation, pathological classification and prognosis of HSPN was analyzed accordingly. The results showed that: (1) there was a significantly higher frequency for DD genotype in HSPN children (P<0.01); (2) DD genotype was more frequently seen in HSPN children with gross hematuria and massive proteinuria (P<0.05), while DI genotype was more common in HSPN children group with renal insufficiency (P<0.05); (3) although mesangial proliferative lesion was most frequently observed in 21 biopsied HSPN children, and DD genotype frequency was still higher in children with severe pathology (Class III IV); (4) II genotype was significantly frequent in HSPN children with complete remission in the follow-up of 32 HSPN children. It was concluded that the deletion allele of ACE gene might play a role, at least to some extent, in the occurrence, deterioration and progression in juvenile HSPN.