Angiotensin II type 1 receptor gene polymorphism predicts development of hypertension and metabolic syndrome

Effects of AGT and AGTR1 Genetic Polymorphisms and Changes in Blood Pressure Over a Five-Year Follow-Up

Purpose

The renin-angiotensin system plays an important role in the central regulation of blood pressure (BP). Genetic variations of angiotensinogen (AGT) and angiotensin II type 1 receptor (AGTR1) may increase susceptibility to elevated BP and hypertension. This study investigated the effects of AGT rs699 and AGTR1 rs5186 single nucleotide polymorphisms (SNPs) on BP at baseline and at a 5-year follow-up.

Paticipants and Methods

The study population consisted of participants from the Electricity Generating Authority of Thailand cohort study (n=354); data were collected at baseline (2013) and 5 years later (2018). Genotyping of the two SNPs was performed using TaqMan® assay and statistical analyses were performed with SNPStats software.

Results

The frequencies of the two SNPs were within the Hardy-Weinberg equilibrium (p=0.22 for AGT rs699 and p=0.06 for AGTR1 rs5186). For each SNP, mutant genotypes were significantly associated with increased systolic BP and/or diastolic BP in the codominant and recessive models. Risk alleles of AGT rs699 and AGTR1 rs5186 were associated with increased odds of hypertension and hypertension with metabolic syndrome at follow-up.

Conclusion

Overall, our results suggest that polymorphisms of genes in the renin-angiotensin system increase susceptibility to the development and progression of hypertension and the development of the metabolic syndrome.

The HARVEST. Looking for optimal management of young people with stage 1 hypertension

In the last few decades there has been much debate about the management of low-risk stage 1 hypertension in youth. In this article, we review the main findings of the HARVEST cohort accrued over 30 years, highlighting the contribution of this study to the existing literature. Tachycardia and sympathetic overdrive were closely intertwined in our HARVEST participants, promoting the development of sustained hypertension, metabolic abnormalities, and increased susceptibility to vascular complications. Short-term blood pressure variability in this age group had a prognostic power even greater than that of average 24h blood pressure. In the HARVEST participants, changes in left ventricular anatomy and contractility were the earliest signs of hypertensive cardiac involvement, whereas left ventricular filling was only marginally affected. Our results highlighted the role of glomerular hyperfiltration in determining microalbuminuria and renal damage in the early stage of hypertension. The genetic approach provided an important contribution to risk stratification and patient management. The HARVEST confirmed the importance of maintaining a good lifestyle for preventing the onset of hypertension, diabetes and cardiovascular events. Isolated systolic hypertension in the first decades of life appeared as a heterogeneous condition. To establish whether antihypertensive drug treatment should be started in this condition the clinician should consider the individual cardiovascular risk profile, the level of office mean BP and central BP. Despite recent progress in our knowledge, systolic hypertension still represents a challenging issue for the clinician. Hopefully, the HARVEST will continue to contribute data that help to fill the present gaps in evidence.

Association of miR-155 and Angiotensin Receptor Type 1 Polymorphisms with the Risk of Ischemic Stroke in a Chinese Population

There is increasing evidence suggesting that dysregulation of miR-155 and its target angiotensin receptor type 1 (AT1R) are linked to the incidence of ischemic stroke (IS), but the underlying mechanisms remain to be clarified. In this study, we therefore sought to investigate how miR-155 and AT1R polymorphisms affect IS risk. We included 579 IS patients and 509 age-matched controls in the present analysis, genotyping individuals for the rs767649 polymorphism in miR-155, as well as for the rs1492099 and rs275653 polymorphisms in AT1R via iMLDR-TM genotyping technology. The allele and genotype frequencies for the assessed polymorphisms were comparable in IS patients and controls, without any detectable association between AT1R haplotype and IS risk. We conducted additional trial of ORG 10172 in acute stroke treatment-mediated stratification, which indicated that the AT1R rs1492099 T allele was linked to a decreased risk of large-artery atherosclerosis (LAA) stroke. We further found that those with the AT1R rs275653 AA genotype had a decreased risk of small-artery occlusion (SAO) strokes. We further confirmed elevated miR-155 expression in IS patients, but observed no link between the rs767649 polymorphism and expression of this microRNA. Similarly, rs1492099 and rs275653 polymorphisms did not impact AT1R expression levels. The miR-155 rs767649 polymorphism does not seem to be a key determinant of IS risk, whereas the AT1R rs1492099 polymorphism is linked to reduced LAA-stroke risk, and the rs275653 AA genotype is potentially protective against SAO strokes.

Risk and severity of psoriasis vulgaris in relation to angiotensin II type 1 receptor gene polymorphism and metabolic syndrome

Background

Psoriasis vulgaris is a chronic inflammatory and proliferative skin disease, characterized by the formation of itchy, erythematous skin patches or plaques. Patients with psoriasis are at an increased risk of developing metabolic syndrome, including obesity, hypertension, diabetes, and atherosclerosis. Recently, angiotensin II (Ang II) has been reported to be associated with the development of psoriasis. Ang II not only increases the blood pressure but is also a potent proinflammatory modulator and functions through interaction with angiotensin II type 1 receptor (AT1R). Moreover, it is hypothesized that the AT1R gene expression could be correlated with the severity of psoriasis and/or metabolic syndrome.

Aim

We examined the association of Ang II type 1 receptor (AT1R) A1166C gene polymorphisms and metabolic syndrome with the severity of psoriasis.

Patients and methods

The present case-control study included 25 patients with psoriasis vulgaris and 25 healthy subjects in Egypt. The psoriasis lesions in the patient group were assessed using the psoriasis area and severity index (PASI) score. The AT1R polymorphism A1166C (rs5186) was studied using restriction fragment length polymorphism (RFLP) and polymerase chain reaction (PCR) amplification of the gene from the whole blood sample in both groups. Serum lipid profile and blood sugar levels were assessed post 12 h and 8 h fasting, respectively, in both groups. The severity of metabolic syndrome was evaluated using the severity score.

Results

The results of the present study demonstrated that the AT1R A1166C gene polymorphisms increased the risk of developing psoriasis in the Egyptian population. We found that 70% of patients with AC genotype and 100% of patients CC genotype reported a PASI score >20 and were considered to be severe cases with a statistically significant difference as compared with patients with AA genotype (p=0.003). In addition, a high statistically significant difference (p=0.001) existed among AT1R genotypes with respect to the percentage of metabolic syndrome in psoriasis patients. Similarly, a statistically significant difference (p=0.004) among AT1R genotypes with respect to metabolic score was found, with the highest level of score and percentage observed in patients with CC genotype than in patients with AC genotype. The lowest level was present among those with AA genotype.

Conclusion

Patients with psoriasis expressing the C allele of AT1R1166 are susceptible to developing metabolic syndrome and have higher PASI scores as compared with patients carrying the A allele.

Angiotensin II Type 1 Receptor rs5186 Gene Variant Predicts Incident NAFLD and Associated Hypertension: Role of Dietary Fat-Induced Pro-Inflammatory Cell Activation

OBJECTIVES

Hypertension has been linked to the presence and severity of nonalcoholic fatty liver disease (NAFLD) through unclear mechanisms. The gain-of-function rs5186 A1166C variant in angtiotensin receptor type 1 (AGTR1) gene has been linked to hypertension, cardiovascular disease and metabolic syndrome. We assessed the impact of AGTR1 A1166C variant on NAFLD incidence and severity and on glucose and lipid metabolism and explored the underlying mechanisms.

METHODS

We followed up 314 healthy nonobese, nondiabetic, nonhypertensive, insulin-sensitive participants in a population-based study, characterized for AGTR1 rs5186 A1166C variant, adipokine profile, inflammatory and endothelial dysfunction markers. An independent cohort of 78 biopsy-proven nondiabetic NAFLD patients and controls underwent an oral glucose tolerance test with Minimal Model analysis of glucose homeostasis, and an oral fat tolerance test with measurement of plasma lipoproteins, adipokines, MCP-1, calprotectin, and nuclear factor-κB activation in circulating mononuclear cells.

RESULTS

AGTR1 A1166C polymorphism predicted 9.8-year incident NAFLD (odds ratio: 1.67, 95% CI: 1.26-2.21) and hypertension (odds ratio: 1.49, 95% CI: 1.12-2.63) and 9-year increase in cardiovascular disease risk and endothelial dysfunction markers. In the cross-sectional cohort, AGTR1 C allele carriers had higher insulin resistance. Despite comparable fasting lipid profiles, AGTR1 C allele carriers showed postprandial triglyceride-rich and cholesterol-rich VLDL lipoprotein accumulation, higher resistin, MCP-1 and calprotectin responses and nuclear factor-κB activation in mononuclear cells, and a blunted postprandial adiponectin response to fat, which predicted liver histology, hepatocyte apoptosis activation, insulin resistance, and endothelial dysfunction.

DISCUSSION

AGTR1 A1166C variant affects liver disease, insulin resistance, and endothelial dysfunction in NAFLD, at least in part by modulating adipokine, chemokine, and pro-inflammatory cell activation in response to fat ingestion.

The Association between Angiotensin II Type 1 Receptor Gene A1166C Polymorphism and Non-alcoholic Fatty Liver Disease and Its Severity

BACKGROUND Genetic predisposition may have important role in pathogenesis of non-alcoholic fatty liver disease (NAFLD). Angiotensin II type I receptor (AGTR1) has been known to involve in the process of liver steatosis and fibrosis. This study aimed to investigate the association between AGTR1 A1166C polymorphism and NAFLD. METHODS A cross-sectional study was conducted during May 2014-May 2015 among healthy adults referring to our radiology clinic for abdominal sonography. AGTR1 A1166C polymorphism was evaluated in subjects with NAFLD and healthy individuals using allelic discrimination method. RESULTS 58 subjects with NAFLD were compared with 88 healthy individuals without NAFLD. The frequency of AA and CC genotypes of AGTR1 was significantly higher in patients with NAFLD compared with controls (p = 0.029 and 0.042, respectively). C allele was more detected in subjects with NAFLD compared with the healthy controls (OR: 2.1; 95% CI: 1.23-3.61, p = 0.006). CC genotype (OR: 10.62; 95% CI: 1.05-106.57, p = 0.045) and C allele (OR: 6.81; 95% CI: 1.42- 32.48, p = 0.016) were also predictors of severe fatty liver disease in our study population. CONCLUSION Our results provide the first evidence that AGTR1 gene A1166C polymorphism not only is associated with NAFLD and but also may predict its severity.

Further investigation of a quantitative trait locus for ascites on chromosome 9 in broiler chicken lines

Previously, we reported a genome wide association study (GWAS) that had shown association of a region between 11.8 and 13.6 Mbp on chromosome 9 with ascites phenotype in broilers. We had used microsatellite loci to demonstrate an association of particular genotypes for this region with ascites in experimental ascites lines and commercial broiler breeder lines. We identified two potential candidate genes, AGTR1 and UTS2D, within that chromosomal region for mediating the quantitative effect. We have now extended our analysis using SNPs for these genes to assess association with resistance or susceptibility to ascites in these same broiler lines. Surprisingly, in contrast to our previous GWAS and microsatellite data for this region, we find no association of the SNP genotypes or haplotypes in the region suggesting that the two genes might have limited association with the disease phenotype.

Estimation of the relationship between the polymorphisms of selected genes: ACE, AGTR1, TGFβ1 and GNB3 with the occurrence of primary vesicoureteral reflux

PURPOSE

Etiopathogenesis of VUR is composite and not fully understood. Many data indicate the importance of genetic predisposition. The aim of this study was to establish the relationship of selected polymorphisms: 14094 polymorphism of the ACE, polymorphism rs1800469 of TGFβ-1, rs5443 gene polymorphism of the GNB3 and receptor gene polymorphism rs5186 type 1 AGTR1 with the occurrence of the primary vesicoureteral reflux.

MATERIAL

The study included 190 children: 90 with the primary VUR confirmed with the voiding cystourethrogram and excluded secondary VUR and a control group of 100 children without a history of the diseases of the genitourinary tract.

METHODS

The study was planned in the scheme: "tested case versus control." Genomic DNA was isolated from the leukocytes of peripheral blood samples. The results were statistically analyzed in the Statistica 10 using χ ² test and analysis of the variance Anova.

RESULTS

Any of the four studied polymorphisms showed no difference in the distribution of genotypes between patients with primary vesicoureteral reflux and the control group. In patients with VUR and TT genotype polymorphism rs5443 GNB3 gene, the glomerular filtration rate was significantly higher than in patients with genotype CC or CT.

CONCLUSIONS

(1) No relationship was found between the studied polymorphisms (14094 ACE gene, rs1800469 gene TGFβ1, GNB3 gene rs5443, rs5186 AGTR1 gene) and the occurrence of primary vesicoureteral reflux. (2) TT genotype polymorphism rs5443 GNB3 gene may be a protective factor for the improved renal function in patients with primary vesicoureteral reflux in patients with genotype CC or CT.

AGTR1 rs3772622 gene polymorphism increase the risk of nonalcoholic fatty liver disease patients suffer coronary artery disease in Northern Chinese Han population

Background

Cardiovascular disease (CAD) responsible and nonalcoholic fatty liver disease (NAFLD) are both metabolic diseases, and they are mostly influenced by genetic factors. The aim of our study is to evaluate the relationship between angiotensin II type-1 receptor (AGTR1) gene rs3772622 polymorphisms and the risk of developing coronary artery disease (CAD) in Chinese patients with NAFLD.

Methods

Genotype for AGTR1 rs3772622 in 574 NAFLD patients with CAD or 589 NAFLD patients without CAD, 332 CAD patients exclude NAFLD and 338 health control subjects were determined by sequencing and polymerase chain reaction analysis. Relevant statistical methods were employed to analyze the genotypes, alleles and the clinical date. Inter-group differences and associations were assessed statistically using t-tests and Chi square and logistic analyses. The relative risk of AGTR1 rs3772622 for NAFLD was estimated by logistic regression analysis.

Results

No significant difference in genotype and allele frequency of AGTR1 rs3772622 was found between the NAFLD without CAD population and the controls (P > 0.05). However, makeable difference was found when compared the CAD in patients with NAFLD and CAD free NAFLD patients (P < 0.001 OR = 2.09). Similarly, significant difference was found in AGTR1 rs3772622 genotype distribution between the groups of CAD patients and control (P = 0.046 OR = 1.71).

Conclusions

AGTR1 rs3772622 gene polymorphism was not associated with the risk of NAFLD, but could increase the risk of NAFLD patients suffering from CAD in the Chinese Han population. Deeply mechanisms underlying the association between AGTR1 rs3772622 gene polymorphism and the risk of CAD in NAFLD patients need more research.

Circulating microRNAs and hypertension--from new insights into blood pressure regulation to biomarkers of cardiovascular risk

Hypertension is a leading cause of cardiovascular morbidity and mortality worldwide, yet the molecular mechanisms underpinning the development of high blood pressure remain incompletely understood. MicroRNAs are small, non-coding RNA molecules approximately 22 nucleotides in length that act as post-transcriptional regulators of gene expression. We highlight, through a review of recent literature, that studies on circulating microRNAs have provided novel insights into blood pressure regulation. They have also complemented tissue-based and animal-based experiments in shedding new light on our understanding of established pathways in hypertension, such as the renin-angiotensin system. Despite a number of challenges, we believe microRNAs herald particular potential in becoming effective biomarkers of target-organ damage in hypertension.

Molecular and clinical analysis of TRPC6 and AGTR1 genes in patients with pulmonary arterial hypertension

BACKGROUND

Pulmonary arterial hypertension (PAH) is a rare and progressive vascular disorder characterized by increased pulmonary vascular resistance and right heart failure. The aim of this study was to analyze 5'UTR region in canonical transient receptor potential isoform 6 (TRPC6) and 3'UTR region in Angiotensin II type I receptor (AGTR1) genes in patients with idiopathic and associated PAH. Correlation among mutations and clinical and functional parameters was further analyzed.

METHODS

Analysis of TRPC6 and AGTR1 genes was performed by polymerase chain reaction (PCR) and direct sequencing. We used a non-parametric test to determine if significant differences were found between the groups studied and chi-square test to compare clinical and hemodynamic variables among genotypes.

RESULTS

Fifty five patients and fifty two controls were included in this study. We found statistically significant differences for c.1-361A > T (p = 0.0077), c.1-254C > G (p < 0.0001) and c.1-218C > T (p = 0.0021) in TRPC6 gene and c.1166A > C (p < 0.001) in AGTR1 gene, between patients and controls. Idiopathic PAH patients (IPAH) and controls presented significant differences for all 3 TRPC6 polymorphisms (p = 0.020), (p = 0.002) and (p = 0.008) respectively, and also showed differences for AGTR1 gene (p < 0.001). In associated PAH (APAH) patients we found statistical differences for c.1-254C > G (p < 0.001) and c.1-218C > T (p = 0.001) in TRPC6 gene and c.1166A > C (p = 0.001) in AGTR1 gene. Several clinical and hemodynamic parameters showed significant differences between carriers and non-carriers of these single nucleotide polymorphisms (SNPs). Nineteen patients were carriers of all 3 SNPs in TRPC6 gene and presented a more severe phenotype with differences in mean pulmonary arterial pressure (p = 0.016), systolic pulmonary arterial pressure (p = 0.040), cardiac index (p < 0.001) and 6 minute walking test (p = 0.049). 16 of these patients harbored the SNP in AGTR1 gene. These patients showed differences in age at diagnosis (p = 0.049), mean pulmonary arterial pressure (p = 0.033), cardiac index (p = 0.002) and 6 minute walking test (p = 0.039).

CONCLUSIONS

PAH is a rare disease with pulmonary vascular remodeling caused in part by a heterogeneous constellation of genetic arrangements. This study seems to suggest that c.1-361A > T, c.1-254C > G and c.1-218C > T polymorphisms in TRPC6 gene and c.1166A > C polymorphism in AGTR1 could have a role in the development of this disease.

Association of angiotensin II type I and type II receptor genes polymorphisms with the presence of premature coronary disease and metabolic syndrome

Premature coronary artery disease (PCAD) is known to have a particularly strong genetic component. We aimed to investigate the association between angiotensin II receptor type 1 (ATR1) or type II (ATR2) genes polymorphisms and PCAD with or without metabolic syndrome in males. 132 male patients with PCAD and 132 controls were included in the study. ATR1 and ATR2 genes polymorphisms were analyzed by polymerase chain reaction. The present study revealed that ATR1 CC genotype and ATR2 G allele increased the risk of PCAD by 2.9 and 1.3 respectively as well as they increased susceptibility to metabolic syndrome by 4.5 and 2.3 respectively. The present study proved that diabetes, smoking, obesity, total cholesterol, triglycerides, LDLc and HDLc were independent risk factors for the development of PCAD. We concluded that ATR1 CC genotype and ATR2 G allele increased the susceptibility of Egyptian males to have PCAD. The increased susceptibility to have metabolic syndrome could be one of the mechanisms leading to the development of PCAD in subjects carrying one or both of these polymorphisms.

Variations of the angiotensin II type 1 receptor gene are associated with extreme human longevity

Longevity phenotype in humans results from the influence of environmental and genetic factors. Few gene polymorphisms have been identified so far with a modest effect on lifespan leaving room for the search of other players in the longevity game. It has been recently demonstrated that targeted disruption of the mouse homolog of the human angiotensin II type 1 receptor (AT1R) gene (AGTR1) translates into marked prolongation of animal lifespan (Benigni et al., J Clin Invest 119(3):524-530, 2009). Based on the above study in mice, here we sought to search for AGTR1 variations associated to reduced AT1 receptor protein levels and to prolonged lifespan in humans. AGTR1 was sequenced in 173 Italian centenarians and 376 younger controls. A novel non-synonymous mutation was detected in a centenarian. Two polymorphisms in AGTR1 promoter, rs422858 and rs275653, in complete linkage disequilibrium, were significantly associated with the ability to attain extreme old age. We then replicated the study of rs275653 in a large independent cohort of Japanese origin (598 centenarians and semi-supercentenarians, 422 younger controls) and indeed confirmed its association with exceptional old age. In combined analyses, rs275653 was associated to extreme longevity either at recessive model (P = 0.007, odds ratio (OR) 3.57) or at genotype level (P = 0.015). Significance was maintained after correcting for confounding factors. Fluorescence activated cell sorting analysis revealed that subjects homozygous for the minor allele of rs275653 had less AT1R-positive peripheral blood polymorphonuclear cells. Moreover, rs275653 was associated to lower blood pressure in centenarians. These findings highlight the role of AGTR1 as a possible candidate among longevity-enabling genes.

Phosducin rs12402521 polymorphism predicts development of hypertension in young subjects with overweight or obesity

BACKGROUND AND AIMS

The G-protein regulator phosducin has been shown to be associated with stress-dependent blood pressure, but whether obesity is a modulator of the relationship between phosducin and risk of hypertension is unknown. We studied the effect of two phosducin polymorphisms on risk of hypertension in 273 overweight or obese (Ov-Ob) young-to-middle-age participants from the HARVEST and 287 normal weight (NW) participants.

METHODS AND RESULTS

Genotyping of phosducin SNPs rs12402521 and rs6672836 was performed by real time PCR. For rs12402521, 64.6% of the participants were homozygous for the G allele, 27.9% heterozygous, and 7.5% homozygous for the A allele. During 7.7 years of follow-up, 339 subjects developed hypertension. In a Cox multivariable model, carriers of the A allele had a 1.28 (95% CI,1.00-1.63, p = 0.046) increased risk of hypertension. However, increased incidence of hypertension associated with A allele (AA + AG, 79% and GG, 59%, p = 0.001) was observed only among Ov-Ob individuals with a hazard ratio of 1.60 (95% CI, 1.13-2.21, p = 0.007) whereas in NW subjects the incidence of hypertension did not differ by genotype (56% in both groups). In the whole cohort, there was a significant interaction of phosducin genotype with body mass index on the risk of hypertension (p = 0.012). For SNP rs6672836 no association was found with incident hypertension. No haplotype effect was detected on the risk of hypertension.

CONCLUSION

These data suggest that phosducin rs12402521 polymorphism is an important genetic predictor of obesity-related hypertension. In Ov-Ob carriers of the A allele aggressive nonpharmacological measures should be implemented.

Genetic susceptibility to non-necrotizing erysipelas/cellulitis

BACKGROUND

Bacterial non-necrotizing erysipelas and cellulitis are often recurring, diffusely spreading infections of the skin and subcutaneous tissues caused most commonly by streptococci. Host genetic factors influence infection susceptibility but no extensive studies on the genetic determinants of human erysipelas exist.

METHODS

We performed genome-wide linkage with the 10,000 variant Human Mapping Array (HMA10K) array on 52 Finnish families with multiple erysipelas cases followed by microsatellite fine mapping of suggestive linkage peaks. A scan with the HMA250K array was subsequently performed with a subset of cases and controls.

RESULTS

Significant linkage was found at 9q34 (nonparametric multipoint linkage score (NPL(all)) 3.84, p=0.026), which is syntenic to a quantitative trait locus for susceptibility to group A streptococci infections on chromosome 2 in mouse. Sequencing of candidate genes in the 9q34 region did not conclusively associate any to erysipelas/cellulitis susceptibility. Suggestive linkage (NPL(all)>3.0) was found at three loci: 3q22-24, 21q22, and 22q13. A subsequent denser genome scan with the HMA250K array supported the 3q22 locus, in which several SNPs in the promoter of AGTR1 (Angiotensin II receptor type I) suggestively associated with erysipelas/cellulitis susceptibility.

CONCLUSIONS

Specific host genetic factors may cause erysipelas/cellulitis susceptibility in humans.

Single nucleotide polymorphisms in G protein signaling pathway genes in preeclampsia

Preeclampsia is a pregnancy specific disorder and a risk factor for later cardiovascular disease. The cause and detailed pathophysiology remains unknown. G protein signaling is involved in a variety of physiological processes, including blood pressure regulation. We assessed whether distributions of 3 single nucleotide polymorphisms in genes coding for components of G protein signaling pathways that have been associated with hypertension differ between women with preeclampsia and normotensive pregnant women; the G protein β3 subunit gene (GNB3) C825T polymorphism (rs5443), the angiotensin II type 1 receptor gene (AGTR1) 3'UTR A1166C polymorphism (rs5186), and the regulator of G protein signaling 2 gene (RGS2) 3'UTR C1114G polymorphism (rs4606). Two separate Norwegian study populations were used; a large population based study and a smaller, but clinically well-described pregnancy biobank. A descriptive study of 43 women with eclampsia was additionally included. In the population-based study, an increased odds of preeclampsia (odds ratio, 1.21; [95% confidence interval, 1.05-1.40]; P=0.009) and recurrent preeclampsia (odds ratio, 1.43; [95% confidence interval, 1.06-1.92];, P=0.017) was found in women carrying the rs4606 CG or GG genotype. In early-onset preeclamptic patients with decidual spiral artery biopsies available (n=24), the rs4606 CG or GG genotype was more frequent in those with acute atherosis (resembling early stage of atherosclerosis) compared with those without: odds ratio, 15.0; (95% confidence interval, 2.02-111.2); P=0.004. No association was found between preeclampsia and the rs5443 or the rs5186. The genotype distribution in eclamptic women was not different from preeclamptic women. In conclusion, RGS2 rs4606 may affect the risk and progression of preeclampsia.

Contemporary approaches to genetic influences on hypertension

PURPOSE OF REVIEW

Essential hypertension has long been considered to be primarily 'genetic,' though recent studies have only revealed minor contributions to blood pressure. Technology has advanced tremendously in the recent years, with much focus on DNA studies utilizing both candidate gene and genome-wide association studies. However, many new areas that need continued investigation have arisen.

RECENT FINDINGS

In addition to DNA studies, genetic studies are actively pursuing previously unexplored areas of potential variation, such as that which occurs posttranscriptionally in RNA and posttranslationally in protein structure. Advances have also been made in animal models and systems biology for large-scale integrative approaches. However, many other areas need continued investigation in the genetics of hypertension, including improved phenotyping and trait definition, gene-by-gene interactions (epistasis), and gene-by-environment interactions. 'Next generation' sequencing will assist researchers in performing more extensive genetic studies even more quickly, especially on unusual (rare) genetic variants.

SUMMARY

Hypertension appears to have many genetic contributions from each regulatory area ranging from DNA to RNA to protein to postprotein to interactive influences of the environment on genes. New technologies have enabled such research to advance in the recent years. However, for this complex trait of hypertension, continued efforts must progress in all of these areas as well as in increased modeling and sequencing, so that the knowledge may be united for a comprehensive understanding of this common disease, such that diagnosis and treatment options in hypertensive patients and those at risk are facilitated.

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.

HFE H63D, C282Y and AGTR1 A1166C polymorphisms and brain white matter lesions in the aging brain

Incidental white matter lesions (WML) are a common neuroradiological finding in elderly people and have been linked to dementia and depression. Various mechanisms including hypoxia and increased production of reactive oxygen species (ROS) are implicated in the etiology of WML. The hemochromatosis (HFE) gene p.H63D and p.C282Y polymorphisms have been linked to dysregulation of iron metabolism and increased levels of ROS, whereas Angiotensin II receptor 1 (AGTR1) c.1166A → C polymorphism is known as a vascular risk factor. These genetic polymorphisms were characterized in brains donated to the UK MRC Cognitive Function and Ageing Study (CFAS) to assess their potential role in the risk for development of age-related WML. The study cohort comprised 258 brain donated to CFAS. WML severity was assessed in the postmortem brain donations using magnetic resonance imaging (MRI) scans and scored using the Scheltens' scale. Polymerase chain reaction (PCR) amplification of extracted DNA followed by restriction enzyme digestion was used to genotype the samples. Genotypes were validated using direct sequencing in a smaller sample. The results show that HFE p.H63D polymorphism is not associated with WML severity in the whole cohort. However, there is a significant association of the D allele with severity of WML in noncarriers of the APOE ε4 allele. No association is demonstrated between the HFE p.C282Y nor the AGTR1 c.1166A → C polymorphisms and WML severity. The HFE gene appears to be a genetic risk factor for severe aging WML independently of the APOE ε4 genotype. This would support the role of iron-related oxidative stress, in addition to previously studied factors, e.g., hypoxia as potential risk factors for developing prominent aging WML.

Interplay between miR-155, AT1R A1166C polymorphism, and AT1R expression in young untreated hypertensives

BACKGROUND

A silent polymorphism (+1166 A/C single-nucleotide polymorphism) localized in the 3'-UTR (untranslated region) of the human angiotensin II type-1 receptor (AT1R) has been associated with hypertension and cardiovascular complications. The +1166 A/C is recognized by a specific microRNA-155 (miR-155), which is base-pairing complementary with the +1166 A-allele but not with the mutant +1166 C allele. Aim of our study was to investigate the interplay between miR-155 and AT1R protein expression.

METHODS

Sixty-four subjects were selected for the +1166 A/C from the cohort of hypertensives (n = 573) of the Hypertension and Ambulatory Recording Venetia Study (HARVEST): 25 were homozygous for the 1166 A allele, 20 heterozygous, and 19 homozygous for the 1166 C allele.

RESULTS

miR-155 expression was significantly decreased in subjects with CC genotype in comparison to AA and AC genotype. AT1R protein expression was significantly increased in the CC group in comparison to AA and AC (P < 0.01) although AT1R mRNA expression was not significantly different in the three groups. AT1R protein expression was positively correlated with systolic and diastolic blood pressure and negatively correlated with miR-155 expression level. Plasma transforming growth factor-β1 (TGF-β1) may have a modulator role in the interplay between miR-155 and AT1R protein expression as it was correlated negatively with miR-155 expression and positively with AT1R protein expression in subjects with CC genotype.

CONCLUSION

The interplay between miR-155 expression, +1166C polymorphism, and AT1R protein expression may have a role in the regulation of blood pressure.

Early inflammatory and metabolic changes in association with AGTR1 polymorphisms in prehypertensive subjects

BACKGROUND

The Seventh Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure in 2003 created a prehypertension category for persons with blood pressures ranging from systolic blood pressure (SBP) of 120-139 mm Hg or diastolic blood pressure (DBP) from 80 to 89 mm Hg, due to increased risk of cardiovascular disease.

METHODS

Our study utilized the University of California-San Diego (UCSD) Twin Hypertension Cohort. We measured comprehensive plasma cholesterol levels and metabolic (glucose, insulin, leptin) and inflammatory markers (interleukin-6 (IL-6), C-reactive protein (CRP), free fatty acids) to determine the differences between normotensive and prehypertensive subjects. Additionally, we determined whether angiotensin II receptor type-1 (AGTR1) polymorphisms, previously associated with hypertension, could predict prehypertension.

RESULTS

A total of 455 white subjects were included in the study (mean age 37.1 years). Prehypertensive subjects were older with greater body mass index (BMI) than the normotensives, and after adjusting for sex and age, had greater plasma glucose, insulin, and IL-6. The common AGTR1 A1166C (rs5186) polymorphism in the 3'-UTR region, particularly the presence of the 1166C allele, which fails to downregulate gene expression, predicted greater likelihood of being in the prehypertension group and higher SBP. A lesser-studied polymorphism in intron-2 of AGTR1 (A/G; rs2276736) was associated with plasma high-density lipoprotein (HDL) and apolipoprotein A-1. In a subgroup analysis of nonobese subjects (N = 405), similar associations were noted.

CONCLUSION

Prehypertensive subjects already exhibit early pathophysiologic changes putting them at risk of future cardiovascular disease, and AGTR1 may also contribute to this increased risk. Further investigation is needed to confirm these findings and the precise molecular mechanisms of action.

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.

Investigation of ACE, ACE2 and AGTR1 genes for association with nephropathy in Type 1 diabetes mellitus

BACKGROUND

Polymorphisms in ACE and AGTR1 genes have been assessed in multiple studies for association with diabetic nephropathy; however, results are conflicting. The ACE2 gene has not been studied extensively for association with diabetic nephropathy.

METHODS

We investigated variants in ACE, ACE2 and AGTR1 for association with nephropathy in a case-control group (1467 participants with Type1 diabetes, case subjects n=718; control subjects n=749) of white descent with grandparents born in the British Isles. All recruited individuals were carefully phenotyped and genotyping was performed using Sequenom, Taqman and gel electrophoresis methods. The χ(2) -test for contingency tables was used to compare genotype and allele frequencies in case and control groups.

RESULTS

No departure from Hardy-Weinberg equilibrium was observed in cases or controls. Two variants within the ACE gene (rs4293, P(allelic) =0.02, P(genotypic) =0.008; rs4309, P(allelic) =0.02, P(genotypic) =0.01) were significantly associated with nephropathy at the 5% level. No variant remained statistically significant following adjustment for multiple comparisons. No single nucleotide polymorphisms in the ACE2 or AGTR1 genes were significantly associated with nephropathy when analysed either by genotype or allele frequencies.

CONCLUSIONS

Our independent case-control study provides no evidence that common variants in ACE, ACE2 and AGTR1 play a major role in genetic susceptibility to diabetic nephropathy in a white population with Type1 diabetes.

Cardiovascular Disease, Single Nucleotide Polymorphisms; and the Renin Angiotensin System: Is There a MicroRNA Connection?

Essential hypertension is a complex disorder, caused by the interplay between many genetic variants, gene-gene interactions, and environmental factors. Given that the renin-angiotensin system (RAS) plays an important role in blood pressure (BP) control, cardiovascular regulation, and cardiovascular remodeling, special attention has been devoted to the investigation of single-nucleotide polymorphisms (SNP) harbored in RAS genes that may be associated with hypertension and cardiovascular disease. MicroRNAs (miRNAs) are a family of small, ∼21-nucleotide long, and nonprotein-coding RNAs that recognize target mRNAs through partial complementary elements in the 3′-untranslated region (3′-UTR) of mRNAs and inhibit gene expression by targeting mRNAs for translational repression or destabilization. Since miRNA SNPs (miRSNPs) can create, destroy, or modify miRNA binding sites, this review focuses on the hypothesis that transcribed target SNPs harbored in RAS mRNAs, that alter miRNA gene regulation and consequently protein expression, may contribute to cardiovascular disease susceptibility.

Haplotype-based case-control study of the human AGTR1 gene and essential hypertension in Han Chinese subjects

OBJECTIVES

Essential hypertension is considered to be a multifactorial trait resulting from the combined influence of environmental and genetic determinants. The aim of the study is to assess the association between the human AGTR1 gene and essential hypertension (EH) using a haplotype-based case-control study in Han Chinese subjects.

DESIGN AND METHODS

Seven tag SNPs and the A1166C polymorphism of the AGTR1 gene were genotyped in 510 hypertension subjects and 510 normotensive subjects using PCR-RFLP method.

RESULTS

Single SNP analyses indicated that the rs12695895 was significantly associated with hypertension, adjusted for covariates. Compared with the other haplotypes, Hap4 (AGGACTT) which carry the susceptible rs12695895 A allele was found to significantly increase the risk of EH with odds ratios equal to 1.84 (p=0.0002).

CONCLUSIONS

The present results indicate that rs12695895 might be a genetic marker for EH and Hap4 (AGGACTT) was associated with hypertension in Han Chinese population.