Interactions between gender and the angiotensin type 1 receptor gene polymorphism

Age- and Gender-Related Differences in Renal Vascular Responses to Angiotensin II in Rats: The Role of the Mas Receptor

Background

Renal hemodynamic is influenced by both gender difference and age. Also, the Mas receptor (MasR) as one of the depressor components of the renin-angiotensin system which has more expression in females could postpone some dysfunctions associated with age, although the association between MasR and age in renal vascular responses to angiotensin II (Ang II) in male and female rats was well undefined. Therefore, the current study examined the effects of age and sex on systemic and renal vascular responses to graded doses of Ang II in Wistar rats with or without MasR antagonists (A779).

Materials and Methods

Anesthetized Wistar male and female rats with two age ranges of 8-12 and 24-28 weeks were exposed to cannulate venous and arterial vessels. After stability, mean arterial pressure (MAP), renal perfusion pressure (RPP), renal vascular resistance (RVR), and renal blood flow (RBF) were measured in response to the infusion of Ang II with or without A779.

Results

There were no significant differences in the base values of MAP, RPP, RBF, and RVR between the two genders in both the age ranges of 8-12 and 24-28 weeks. In addition, no significant gender difference was observed in the age ranges of the above mentioned parameters among the groups receiving vehicle or A779. Also, the infusion of vehicle or A779 could not significantly change the base values. On the other hand, the responses of RBF and RVR to Ang II revealed gender differences among 8-12-week groups (P < 0.05) but not in 24-28-week groups, while the blockade of MasR could not influence the responses in the age ranges.

Conclusion

It was concluded that age could impress sex difference in RBF and RVR responses to Ang II infusion and that MasR alone could not participate in these responses. In other words, MasR is not active under normal and acutely elevated Ang II levels.

SARS CoV2 infection _The longevity study perspectives

Like other infectious diseases, COVID-19 shows a clinical outcome enormously variable, ranging from asymptomatic to lethal. In Italy, like in other countries, old male individuals, with one or more comorbidity, are the most susceptible group, and show, consequently, the highest mortality, and morbidity, including lethal respiratory distress syndrome, as the most common complication. In addition, another extraordinary peculiarity, that is a surprising resistance to COVID-19, characterizes some Italian nonagenarians/centenarians. Despite having the typical COVID-19 signs and/or symptoms, such exceptional individuals show a surprising tendency to recover from illness and complications. On the other hand, long-lived people have an optimal performance of immune system related to an overexpression of anti-inflammatory variants in immune/inflammatory genes, as demonstrated by our and other groups. Consequently, we suggest long-lived people as an optimal model for detecting genetic profiles associated with the susceptibility and/or protection to COVID-19, to utilize as potential pharmacological targets for preventing or reducing viral infection in more vulnerable individuals.

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

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

Sex differences in abdominal aortic aneurysms

Abdominal aortic aneurysm (AAA) is a vascular disorder with a high case fatality rate in the instance of rupture. AAA is a multifactorial disease, and the etiology is still not fully understood. AAA is more likely to occur in men, but women have a greater risk of rupture and worse prognosis. Women are reportedly protected against AAA possibly by premenopausal levels of estrogen and are, on average, diagnosed at older ages than men. Here, we review the present body of research on AAA pathophysiology in humans, animal models, and cultured cells, with an emphasis on sex differences and sex steroid hormone signaling.

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

BACKGROUND

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

METHODS AND RESULTS

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

CONCLUSIONS

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

Angiotensin II Type 1 Receptor Gene A1166C Polymorphism Was Not Associated With Acute Coronary Syndrome in an Iranian Population

Background

There are very limited data for Iranian populations on the predisposing genetic factors for acute coronary syndrome (ACS).

Objectives

The objective of the present study was to investigate the association of the angiotensin II type 1 receptor (AT1R) gene polymorphism and ACS in an Iranian population.

Patients and Methods

This cross-sectional study was conducted among 263 subjects (97 men and 166 women). Patients (n = 128) aged 30 - 80 years with chest pain were recruited from the emergency department of Ghaem Hospital (Mashhad, Iran). A 12-lead electrocardiograph plus creatine kinase MB (CK-MB) levels were used as the basis for the diagnosis of myocardial ischemia. The control group was selected from age-matched healthy subjects (n = 135). Non-enzymatic kits were used for extraction of DNA from blood samples. Polymerase chain reaction (PCR) was performed to amplify the DNA fragments. For restriction fragment length polymorphism (RFLP) determination, the DdeI enzyme was used to digest the amplified DNA fragments. Statistical analyses were performed using SPSS version 13.0.

Results

There was no statistical difference in the genotype frequency of patients and healthy subjects with regard to age and gender (P > 0.05).

Conclusions

The AT1R A1166C polymorphism appeared not to be associated with the presence of ACS in the population studied.

Study of the association between the donors and recipients angiotensin-converting enzyme insertion/deletion gene polymorphism and the acute renal allograft rejection

Background: Angiotensin converting enzyme (ACE) is involved in various pathophysiological conditions including renal function. ACE levels are under genetic control.

Objectives: This study was designed to investigate the association between the donors and recipients ACE-I/D gene polymorphism and risk of acute rejection outcome in renal allograft recipients.

Patients and Methods: ACE-I/D polymorphism was determined in 200 donor-recipient pairs who had been referred to Afzalipour hospital in Kerman. ACE-I/D polymorphism was detected using polymerase chain reaction (PCR). Acute rejection (AR) during at least six months post-transplantation was defined as a 20% increase in creatinine level from the postoperative baseline in the absence of other causes of graft dysfunction which responded to antirejection therapy.

Results: The observed allele frequencies were II 9.8%, ID 35.6% and DD 44.4% in donors and II 9.8%, ID 35.1% and DD 52.7% in recipients. There were no significant association between ACE genotypes and AR episodes (OR_ID=0.96 [0.18-5.00] and OR_DD: 1.24 [0.25-6.07] for the donors) and (OR_ID: 0.29 [0.06-1.45] and OR_DD: 0.75 [0.19-2.90] for the recipients).

Conclusions: It seems that donor and recipient ACE-I/D genotype might not be a risk factor for acute renal allograft rejection. However, due to conflicting results from this and other studies, multicenter collaborative studies with more participants and concomitant evaluation of ACE polymorphism with other polymorphisms in renin–angiotensin system (RAS) are suggested to determine whether ACE genotypes are significant predictors of renal allograft rejection.

The "his and hers" of the renin-angiotensin system

Sex differences exist in the regulation of arterial pressure and renal function by the renin-angiotensin system (RAS). This may in part stem from a differential balance in the pressor and depressor arms of the RAS. In males, the ACE/AngII/AT(1)R pathways are enhanced, whereas, in females, the balance is shifted towards the ACE2/Ang(1-7)/MasR and AT(2)R pathways. Evidence clearly demonstrates that premenopausal women, as compared to aged-matched men, are protected from renal and cardiovascular disease, and this differential balance of the RAS between the sexes likely contributes. With aging, this cardiovascular protection in women is lost and this may be related to loss of estrogen postmenopause but the possible contribution of other sex hormones needs to be further examined. Restoration of these RAS depressor pathways in older women, or up-regulation of these in males, represents a therapeutic target that is worth pursuing.

A study on the polymorphisms of the renin-angiotensin system pathway genes for their effect on blood pressure levels in males from Algeria

INTRODUCTION

Several studies have assessed the relationship between blood pressure (BP) and polymorphisms within the genes encoding angiotensinogen (AGT), angiotensin II type 1 receptor (AT1R) and angiotensin-converting enzyme (ACE). However, considering the relatively large discrepancy in frequency and impact of these variants between ethnic groups and populations, still unavailable data from Algerian population are needed.

OBJECTIVE

Our purpose is to evaluate the association between the AGT M235T, AT1R +1166A/C and ACE I/D polymorphisms and variations in systolic (SBP), diastolic (DBP) and pulse pressure (PP) values.

METHODS

The associations with BP were assessed in a representative sample of 115 male subjects free of coronary heart disease (CHD). The AGT M235T, AT1R +1166A/C and ACE I/D polymorphisms were determined by PCR-ASO and PCR-RFLP analysis, respectively.

RESULTS

We showed no associations between the AGT M235T, AT1R +1166A/C nor the ACE I/D polymorphisms with variations in BP values. However, concerning the ACE I/D polymorphism, subjects carrying the ACE I allele tended to have higher SBP (+4.1 mmHg) and PP values (+3.2 mmHg) than DD subjects (adjusted p = 0.087 and p = 0.102, respectively).

CONCLUSION

The ACE I/D polymorphism needs further investigation in a larger Algerian study, especially concerning its putative impact on SBP and PP.

Between candidate genes and whole genomes: time for alternative approaches in blood pressure genetics

Blood pressure has a significant genetic component, but less than 3% of the observed variance has been attributed to genetic variants identified to date. Candidate gene studies of rare, monogenic hypertensive syndromes have conclusively implicated several genes altering renal sodium balance, and studies of essential hypertension have inconsistently implicated over 50 genes in pathways affecting renal sodium balance and other functions. Genome-wide linkage scans have replicated numerous quantitative trait loci throughout the genome, and over 50 single nucleotide polymorphisms (SNPs) have been replicated in multiple genome-wide association studies. These studies provide considerable evidence that epistasis and other interactions play a role in the genetic architecture of blood pressure regulation, but candidate gene studies have limited scope to test for epistasis, and genome-wide studies have low power for both main effects and interactions. This review summarizes the genetic findings to date for blood pressure, and it proposes focused, pathway-based approaches involving epistasis, gene-environment interactions, and next-generation sequencing to further the genetic dissection of blood pressure and hypertension.

Influence of renin-angiotensin system gene polymorphisms on the risk of ST-segment-elevation myocardial infarction and association with coronary artery disease risk factors

BACKGROUND

Recent advances in molecular biology have made it possible to identify numerous polymorphisms of the renin-angiotensin system, which play an important role in the etiology of cardiovascular disease.

OBJECTIVE

The aims of the study were (i) to assess the distribution of the angiotensin II type 1 receptor (AGTR1) gene 1166A/C polymorphism and two polymorphisms of the angiotensinogen (AGT) gene (Met235Thr and Thr174Met) in patients with ST-segment-elevation myocardial infarction (STEMI) who underwent coronary angiography, compared with healthy volunteers; (ii) to determine if there was any correlation between these polymorphisms and risk of STEMI; and (iii) to assess the association of the examined polymorphisms with such classic cardiovascular risk factors as hypertension, diabetes mellitus, obesity (based on a body mass index ≥25 kg/m2), smoking, dyslipidemia, and family history of cardiovascular disease.

METHODS

A total of 100 patients (mean age 57 ± 10 years [range 31-76 years]; 21% women) with diagnosed STEMI and a control group consisting of 95 healthy volunteers (mean age 38 ± 11 years [range 17-60 years]; 20% women) were investigated for the AGTR1 1166A/C polymorphism and two variants of AGT (Met235Thr and Thr174Met). All patients received standard therapy for STEMI.

RESULTS

There were significant differences in the distribution of genotypes and the AGT Met174 allele for AGT Thr174Met polymorphism between patients and healthy subjects (p < 0.05). The AGTR1 1166A/C polymorphism genotype frequencies were significantly different in patients with hypertension compared with normotensive individuals. Specifically, the AGTR1 1166 AA genotype was twice as common in patients with hypertension as in those without (67% vs 33%), while the AC and CC genotypes were found predominantly in normotensive patients (p = 0.0016). The variant 1166C allele was much more common in patients without hypertension (67%) than in patients with hypertension (33%; p = 0.0006). The variant AGT Thr235 allele was more common in patients without a family history of cardiovascular disease than in patients with this risk factor (p < 0.05). The odds ratio (OR) for STEMI in patients with the heterozygous AGT 174 Thr/Met genotype was increased to 1.884 (95% confidence interval [CI] 1.03, 3.446; p < 0.05), while the OR calculated for carriers of the AGT Met174 allele was 2.038 (95% CI 1.129, 3.68; p = 0.0182). Significant genotypic associations of combinations of renin-angiotensin system gene polymorphisms in STEMI were not observed.

CONCLUSIONS

The most powerful predictive value for STEMI was represented by the Thr/Met genotype and the Met174 allele of the AGT Thr174Met gene polymorphism. In our study, in contrast to observations reported by other authors, the AA genotype of the AGTR1 1166A/C gene polymorphism - much more than other genotypes - was associated with hypertension.

Increased urinary protein excretion in the "normal" range is associated with increased renin-angiotensin system activity

Increased levels of albuminuria and proteinuria, both linked to augmented renin-angiotensin system (RAS) activity, are associated with adverse kidney and cardiovascular events. However, the relationship between variations in urinary albumin excretion (UAE) and total protein excretion (UTPE) in the normal range and RAS activity is unclear. We examined the association between UAE and UTPE and the hemodynamic response to angiotensin II (ANG II) challenge, a well-accepted indirect measure of RAS activity, in healthy individuals with normal UAE and UTPE. Forty subjects (15 men, 25 women; age 38 ± 2 yr; UAE, 3.32 ± 0.55 mg/day; UTPE, 56.8 ± 3.6 mg/day) were studied in high-salt balance. Blood pressure (BP), arterial stiffness determined by applanation tonometry, and circulating RAS components were measured at baseline and in response to graded ANG II infusion. The primary outcome was the BP response to ANG II challenge at 30 and 60 min. UAE was associated with a blunted diastolic BP response to ANG II infusion (30 min, P = 0.005; 60 min, P = 0.17), a relationship which remained even after adjustment (30 min, P < 0.001; 60 min, P = 0.035). Similar results were observed with UTPE (30 min, P = 0.031; 60 min, P = 0.001), even after multivariate analysis (30 min, P = 0.008; 60 min, P = 0.001). Neither UAE nor UTPE was associated with systolic BP, circulating RAS components, or arterial stiffness responses to ANG II challenge. Among healthy individuals with UAE and UTPE in the normal range, increased levels of these measures were independently associated with a blunted diastolic BP response to ANG II, indicating increased vascular RAS activity, which is known to be deleterious to both renal and cardiac function.

Association of angiotensin II type 1 receptor gene A1166C polymorphism with the presence of diabetes mellitus and metabolic syndrome in patients with documented coronary artery disease

BACKGROUND

There are relatively limited data available on the genetic susceptibility to diabetes mellitus and metabolic syndrome in the Iranian population. We have therefore investigated the association between the angiotensin II type I receptor gene polymorphism (AT(1)R/A1166C) and the presence of diabetes mellitus and metabolic syndrome in a well defined group of patients.

METHODS

Patients with angiographically defined coronary artery disease (CAD) (n=309) were evaluated for the presence of AT(1)R/A1166C polymorphism. These patients were classified into subgroups with (n=164, M/F: 109/55) and without (n=145, M/F: 84/61) diabetes mellitus. The AT(1)R polymorphism was assessed using a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) based method.

RESULTS

There was a higher frequency of polymorphic genotypes (AC+CC) in the diabetic compared with the non-diabetic group (p=0.01). When determined for each gender separately, this difference remained significant in the males (p=0.04) but not in females (p=0.09). With regard to the allele frequencies, the C allele was significantly higher and the A allele frequency was lower in the diabetic group (p=0.01). This remained significant after gender segregation for males (p=0.01) but not females. In the binary logistic regression analysis, only serum fasting glucose was found as the independent predictor for the presence of diabetes in the CAD patients (β=1.16, p<0.001 for total population and β=1.29, p<0.001 for male subjects). There was no significant difference in genotype or allele frequencies between subgroups with and without metabolic syndrome, this being unaffected by gender or the definition of metabolic syndrome used apart from a significantly lower frequency of C allele in male subjects with metabolic syndrome defined by the NCEP ATP III criteria (p=0.04).

CONCLUSION

The AT(1)R/A1166C polymorphism may be associated with the presence of diabetes mellitus in male subjects with documented CAD.

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

BACKGROUND AND AIMS

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Angiotensin receptor gene polymorphisms and 2-year change in hyperintense lesion volume in men

This longitudinal study examined the relationship between 2-year change in white matter hyperintense lesion (WML) volume and polymorphisms in genes coding for the angiotensin-II type 1 and type 2 receptors, AGTR1 A1166C and AGTR2 C3123A, respectively. 137 depressed and 94 non-depressed participants aged >or=60 years were enrolled. Standard clinical evaluations were performed on all participants and blood samples obtained for genotyping. 1.5-T MRI (magnetic resonance imaging) data were obtained at baseline and approximately 2 years later. These scans were processed using a semi-automated segmentation process, which allowed for the calculation of WML volume at each time point. Statistical models were tested for the relationship between change in WML volume and genotype, while also controlling for age, sex, diagnostic strata, baseline WML volume and comorbid cerebrovascular risk factors. In men, AGTR1 1166A allele homozygotes exhibited significantly less change in WML volume than 1166C carriers. We also found that men reporting hypertension (HTN) with the AGTR2 3123C allele exhibit less change in WML volume than hypertensive men with the 3123A allele, or men without HTN. There were no significant relationships between these polymorphisms and change in WML volume in women. No significant gene-gene or gene-depression interactions were observed. Our results parallel earlier observed gender differences of the relationship between other renin-angiotensin system polymorphisms and HTN. Further work is needed to determine whether these observed relationships are secondary to polymorphisms affecting response to antihypertensive medication, and whether antihypertensive medications can slow WML progression and lower the risk of morbidity associated with WMLs.

Sex differences in acute ANG II-mediated hemodynamic responses in mice

Male sex is associated with higher blood pressure and greater renal injury, perhaps related to greater sensitivity to ANG II. In anesthetized male and female C57BLK/6 mice, we assessed responses of mean arterial pressure (MAP) and renal vascular resistance (RVR; Transonic flow probe) to acute bolus injections of ANG II (0.3-3.0 microg/kg iv) and phenylephrine (PE; 30-300 microg/kg) during low-, normal-, and high-sodium diets. The role of reactive oxygen species was determined by coadministration of tempol. ANG II type 1 and type 2 (AT1 and AT2) receptor and endothelial nitric oxide synthase (NOS3) expression were determined in dissected kidney vessels. While no difference was found on the low-sodium (LS) diet, MAP and RVR responses to ANG II were greater in males during the normal-sodium (NS) and high-sodium (HS) diets (e.g., RVR response at ANG II 3.0 microg/kg during NS: +329 +/- 22 vs. +271 +/- 28 mmHg.ml(-1).min, P = 0.029, effect size = 0.75). Tempol had no effect on the sex-dependent responses on any of the diets. On the LS diet, AT1 and AT2 receptor expression was higher in males. No sex differences were found on the NS diet. On the HS diet, AT1 was higher, and NOS3 expression was lower in males. Acute responses to ANG II are greater in male mice during NS and HS diets, which is, in part, related to differences in AT1, AT2, and NOS3 expression in kidney vessels. Mouse models will be useful to study the role of sex differences in ANG II sensitivity for cardiovascular and renal disease.

Angiotensin II type 1 receptor polymorphisms and susceptibility to hypertension: a HuGE review

The angiotensin II type 1 receptor (AGTR1) plays an integral role in blood pressure control, and is implicated in the pathogenesis of hypertension. Polymorphisms within this gene have been extensively studied in association with hypertension; however, findings are conflicting. To clarify these data, we conducted a systematic review of association studies of AGTR1 polymorphisms and hypertension, and performed a meta-analysis of the rs5186 variant. Results show that the currently available literature is too heterogeneous to draw meaningful conclusions. The definition of hypertension and gender composition of individual studies helps to explain this heterogeneity. Although the structure and splicing pattern of AGTR1 would suggest a likely effect of polymorphisms within the promoter region on gene function, few studies have been conducted thus far. In conclusion, there is insufficient evidence that polymorphisms in the AGTR1 gene are risk factors for hypertension. However, most studies are inadequately powered, and larger well-designed studies of haplotypes are warranted.

Human microRNA-155 on chromosome 21 differentially interacts with its polymorphic target in the AGTR1 3' untranslated region: a mechanism for functional single-nucleotide polymorphisms related to phenotypes

Animal microRNAs (miRNAs) regulate gene expression through base pairing to their targets within the 3' untranslated region (UTR) of protein-coding genes. Single-nucleotide polymorphisms (SNPs) located within such target sites can affect miRNA regulation. We mapped annotated SNPs onto a collection of experimentally supported human miRNA targets. Of the 143 experimentally supported human target sites, 9 contain 12 SNPs. We further experimentally investigated one of these target sites for hsa-miR-155, within the 3' UTR of the human AGTR1 gene that contains SNP rs5186. Using reporter silencing assays, we show that hsa-miR-155 down-regulates the expression of only the 1166A, and not the 1166C, allele of rs5186. Remarkably, the 1166C allele has been associated with hypertension in many studies. Thus, the 1166C allele may be functionally associated with hypertension by abrogating regulation by hsa-miR-155, thereby elevating AGTR1 levels. Since hsa-miR-155 is on chromosome 21, we hypothesize that the observed lower blood pressure in trisomy 21 is partially caused by the overexpression of hsa-miR-155 leading to allele-specific underexpression of AGTR1. Indeed, we have shown in fibroblasts from monozygotic twins discordant for trisomy 21 that levels of AGTR1 protein are lower in trisomy 21.

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.

Endothelial Nitric Oxide Synthase Gene/Gender Interactions and the Renal Hemodynamic Response to Angiotensin II

Endothelial function is dependent on the generation of nitric oxide (NO) by the enzyme endothelial NO synthase (eNOS). One functional coding polymorphism of the eNOS gene (G894-->T) is associated with reduced enzyme activity, increased coronary heart disease, and the development of end-stage renal failure. Because gender and renin-angiotensin system activation also play key roles in the development of renal and cardiovascular disease and because NO plays a role in the response to angiotensin II (AngII), it was hypothesized that the eNOS gene G894-->T polymorphism would be a determinant of the systemic and renal vascular response to AngII. Fifty young, healthy, normotensive individuals who were on a controlled sodium and protein diet for 1 wk underwent assessment of BP and renal hemodynamic function at baseline and during AngII infusion (4 ng/kg per min for 45 min). Participants were genotyped for the eNOS gene G894-->T polymorphism and then segregated into groups on the basis of gender and genotype (GG versus GT/TT). Baseline values for renal blood flow, effective renal plasma flow, and GFR were lower in men with the T allele compared with men who were homozygous for the G allele (P = 0.03), but the polymorphism was not associated with renal hemodynamic function in women. The BP responses to AngII were similar in men and women regardless of genotype. Both multivariate linear regression and analysis of covariance (ANCOVA) revealed a relationship between gender and genotype. Men with the GT/TT genotype exhibited a significantly greater decrease in GFR (P = 0.04) in response to AngII than did those with the GG genotype. This association was not observed in women. The eNOS gene G894-->T polymorphism is a determinant of both baseline renal hemodynamic function and the hemodynamic response to AngII in men but not in women.

Renin-angiotensin-aldosterone system in brain infarction and vascular death

The renin-angiotensin-aldosterone system has functions that may contribute to brain infarction (BI). In 459 matched pairs of white patients and control subjects, we measured plasma angiotensin-converting enzyme (ACE) levels, seven polymorphisms (angiotensinogen T174M and M235T, ACE I/D and 4656 2/3CT repeat [rpt], angiotensin II type 1 receptor A1166C and A153G, and aldosterone synthase CYP11B2), and evaluated 5-year poststroke mortality. Mean plasma ACE levels (+/-standard error) were significantly greater in patients than control subjects (37.5 +/- 0.9 vs 33.9 +/- 0.9), in patients with lacunar stroke, and in patients with no previous vascular (cerebrovascular or cardiovascular) history. The risk for BI increased with tertiles of plasma ACE, without an interaction with hypertension. After adjustments, the association disappeared except among patients with cardioembolic BI and those without previous vascular events. Among the polymorphisms, there was a weak association of BI with angiotensin II type 1 receptor 1166C, a weak protective effect with angiotensinogen 174M, and a strong association of angiotensinogen 235T with 5-year vascular mortality. These results suggest that renin-angiotensin-aldosterone system activity and genes contribute to cerebrovascular disease and poststroke vascular death in white patients.

Blood pressure response to strength training may be influenced by angiotensinogen A-20C and angiotensin II type I receptor A1166C genotypes in older men and women

OBJECTIVES

To determine the influence of angiotensinogen (AGT) A-20C, M235 T, and angiotensin II type 1 receptor (AGTR1) A1166C genotypes on resting blood pressure (BP) response to strength training (ST) in older men and women.

DESIGN

Prospective intervention study with retrospective genotyping.

SETTING

University of Maryland Exercise Physiology Laboratory.

PARTICIPANTS

Seventy sedentary, healthy older men (n=34) and women (n=36).

INTERVENTION

Approximately 23 weeks of ST performed 3 days per week.

MEASUREMENTS

Resting BP was measured on six separate occasions before and after ST for each subject. AGT and AGTR1 genotyping was performed retrospectively from each subject's genomic deoxyribonucleic acid.

RESULTS

Systolic BP decreased in C-allele carriers at the AGT A-20C locus with ST (122+/-1 to 116+/-2 mmHg, P<.05), which was significantly greater than the decrease in the A homozygotes (126+/-1 to 123+/-1 mmHg, P<.05). At the AGTR1 A1166C locus, diastolic BP decreased to a greater extent in the C-allele carriers (76+/-1 to 70+/-2 mmHg, P<.05) than in the A homozygotes (75+/-1 to 72+/-1 mmHg, P<.05).

CONCLUSION

The AGT A-20C and AGTR1 A1166C genotypes may influence resting BP response to ST, such that C-allele carriers at each of these loci reduce their resting BP in response to ST to a greater extent than A homozygotes.

The impact of renin-angiotensin system polymorphisms on physiological and pathophysiological processes in humans

PURPOSE OF REVIEW

The renin-angiotensin system plays a central role in health and disease but the determinants of renin-angiotensin system activity have not been fully elucidated. Physiologic genomics continues to be an active area of research that emphasizes definition of phenotype and clarification of non-genomic factors that influence the genotype-phenotype correlation. A common variant of the angiotensinogen gene (T235) predicts elevated levels of circulating angiotensinogen, and polymorphisms of this gene have been linked to physiologic responses and to the risk of cardiovascular disease. The angiotensin-converting-enzyme gene insertion/deletion polymorphism, although not considered functional, has been associated with physiologic responses and disease risk in hypertension and diabetes. A polymorphism of the angiotensin type 1 receptor gene, A1166C, has been the focus of several physiologic studies. These authors will focus on mechanistic studies in normal humans and those with diabetes mellitus or hypertension that examine the impact of these polymorphisms on physiologic responses.

RECENT FINDINGS

Recent studies provide divergent results. Many have shown that mediating factors interfere with the genotype-phenotype correlation. Studies in normal individuals and in those with diabetes mellitus have shown that sodium status and glycemia can alter the impact of genotype. In individuals with essential hypertension, the pathway between genotype and physiology can be disrupted by gender and/or race.

SUMMARY

Divergent results in many studies may be attributable to various non-genomic and environmental influences on the pathway between gene polymorphism and physiology. Clarification of these factors should allow a better understanding of genotype-phenotype correlation.

The metabolic syndrome: A crossroad for genotype-phenotype associations in atherosclerosis

The metabolic syndrome comprises a set of metabolic and physiologic risk factors associated with elevated cardiovascular disease risk. The expression of each one of its major factors (hypertriglyceridemia, low high-density lipoprotein cholesterol levels, hypertension, abdominal obesity, and insulin resistance) has been found to be the result of complex interactions between genetic and environmental factors. Moreover, obesity may play a major role in triggering the metabolic syndrome by interacting with genetic variants at candidate genes for dyslipidemia, hypertension, and insulin resistance. In support of this hypothesis, several studies at multiple candidate genes have already demonstrated the significance of these interactions; however, the data and their reliability are still very limited, and in many cases replication studies are still lacking in the literature. Therefore, more studies with better epidemiologic design and standardized adiposity measures are needed to estimate the contribution of body weight and fat distribution to the genetic predisposition to the metabolic syndrome, which is the most common cardiovascular disease risk factor in industrialized societies.