X-linked angiotensin II type 2 receptor gene polymorphism -1332A/G in male patients with essential hypertension

Exploring AT2R and its polymorphism in different diseases: An approach to develop AT2R as a drug target beyond hypertension

The Angiotensin II type 2 receptor (AT2R) is one of the critical components of the renin-angiotensin system (RAS), which performs diverse functions like inhibiting cell differentiation, cell proliferation, vasodilatation, reduces oxidative stress and inflammation. AT2R is relatively less studied in comparison to other components of RAS despite its uniqueness (sex-linked) and diverse functions. The AT2R is differentially expressed in different tissues, and its gene polymorphisms are associated with several diseases. The molecular mechanism behind the association of AT2R and its gene polymorphisms with the diseases remains to be fully understood, which hinders the development of AT2R as a drug target. Single nucleotide polymorphisms (SNPs) in AT2R are found at different locations (exons, introns, promoter, and UTR regions) and were studied for association with different diseases. There may be different mechanisms behind these associations as some AT2R SNP variants were associated with differential expression, the SNPs (A1675G/A1332G) affect the alternate splicing of AT2R mRNA, A1332G genotype results in shortening of the AT2R mRNA and subsequently defective protein. Few SNPs were found to be associated with the diseases in either females (C4599A) or males (T1334C). Several other SNPs were expected to be associated with other similar/related diseases, but studies have not been done yet. The present review emphasizes on the significance of AT2R and its polymorphisms associated with the diseases to explore the precise role of AT2R in different diseases and the possibility to develop AT2R as a potential drug target.

Angiotensin II type 2 receptor gene polymorphisms and serum angiotensin-converting enzyme level in Egyptian children with systemic lupus erythematosus

Background

There are no reports about the association of angiotensin II type 2 receptor ( AT2R) gene polymorphisms and susceptibility to systemic lupus erythematosus (SLE) in children.

Objective

The objective of this research is to study AT2R gene polymorphisms in exon 3 (C1593A) and intron 1 (A1675G) in Egyptian children with SLE and its correlation with disease manifestations and serum angiotensin-converting enzyme (ACE) level.

Methods

Typing of AT2R gene polymorphisms was conducted in 123 children with SLE in comparison with 100 healthy controls using the restriction fragment length polymorphism method.

Results

Significant differences were found between SLE patients and controls for A-containing genotypes (CA + AA) and A-allele frequencies of AT2R in exon 3 (C1593A) ( p = 0.01, odds ratio (OR) = 2.5, 95% confidence interval (CI) = 1.3–5.05; p = 0.01, OR = 2.2, 95% CI = 1.2–4.1, respectively). G-containing genotypes (AG + GG) and G allele of AT2R in intron 1 (A1675G) were more frequent in SLE patients compared to controls ( p = 0.01, OR = 2.3, 95% CI = 1.2–4.5; p = 0.02, OR = 2.1, 95% CI = 1.2–3.7, respectively). Serum ACE level was significantly higher in SLE patients than in controls ( p < 0.001). There was no association between AT2R gene polymorphisms and ACE level in serum. Moreover, there was no association between AT2R gene polymorphisms and SLE clinical manifestations.

Conclusion

AT2R gene polymorphisms can be considered risk factors for SLE development in Egyptian children.

A promoter polymorphism in APJ gene is significantly associated with blood pressure changes and hypertension risk in Chinese women

The aim of this study was to interrogate the gender-specific association of 5 well-defined polymorphisms in apelin/APJ system with both blood pressure changes and hypertension risk in a northeastern Chinese population. This is a population-based case-control study, including 650 hypertensive patients and 645 normotensive controls. Data were analyzed by STATA and Haplo.Stats. The genotype distributions of 5 study polymorphisms were in Hardy-Weinberg equilibrium in both genders. The rs7119375 and rs10501367 were completely linked. The genotypes (P = 0.001) and alleles (P < 0.001) of rs7119375 differed significantly between patients and controls in women. Carriers of rs7119375-AA genotype had significant higher systolic blood pressure (SBP) than carriers of rs7119375-GG genotype in both patients and controls of female gender (P < 0.01). Moreover, carriers of rs7119375-A allele were 1.80 times more likely to develop hypertension relative to carriers of rs7119375-GG genotype after adjusting for age, body mass index and glucose (odds ratio: 1.80; 95% confidence interval: 1.03–3.16; P = 0.040). Further allele combination analysis supported the leading contribution of rs7119375 to hypertension risk. Our findings demonstrated that the mutation of promoter polymorphism rs7119375 in APJ gene was significantly associated with elevated SBP and increased hypertension risk in Chinese women.

Association and Interaction Effect of AGTR1 and AGTR2 Gene Polymorphisms with Dietary Pattern on Metabolic Risk Factors of Cardiovascular Disease in Malaysian Adults

Gene-diet interaction using a multifactorial approach is preferred to study the multiple risk factors of cardiovascular disease (CVD). This study examined the association and gene-diet interaction effects of the angiotensin II type 1 receptor (AGTR1) gene (rs5186), and type 2 receptor (AGTR2) gene (rs1403543) polymorphisms on metabolic risk factors of CVD in Malaysian adults. CVD parameters (BMI, blood pressure, glycated hemoglobin, total cholesterol (TC), triglycerides, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol (HDL-C), and TC/HDL-C ratio), and constructed dietary patterns “vegetables, fruits, and soy diet” (VFSD), and “rice, egg, and fish diet” (REFD) were obtained from previous studies. Genotyping analysis was performed by real-time PCR using Taqman probes. The subjects were 507 adults (151 Malays; 179 Chinese; and 177 Indians). Significant genetic associations were obtained on blood lipids for rs5186 in Malays and Chinese, and rs1403543 in Chinese females. The significant gene-diet interaction effects after adjusting for potential confounders were: rs5186 × VFSD on blood pressure in Malays (p = 0.016), and in Chinese on blood lipids for rs5186 × REFD (p = 0.009–0.023), and rs1403543 × VFSD in female subjects (p = 0.001–0.011). Malays and Chinese showed higher risk for blood pressure and/or lipids involving rs5186 and rs1403543 SNPs together with gene-diet interactions, but not Indians.

AT2R -1332 G:A polymorphism and its interaction with AT1R 1166 A:C, ACE I/D and MMP-9 -1562 C:T polymorphisms: risk factors for susceptibility to preeclampsia

The possible association of angiotensin type 2 receptor (AT2R) -1332 G:A polymorphism with susceptibility to preeclampsia was studied in 252 women consisted of 155 women with preeclampsia and 97 healthy pregnant women. Also, the interaction of this polymorphism with angiotensin type 1 receptor (AT1R) 1166 A:C, angiotensin converting enzyme insertion/deletion (ACE I/D) and also with matrix metalloproteinase-9 (MMP-9) -1562 C:T polymorphism was investigated. The AT2R -1332 G:A polymorphism was detected using PCR-RFLP method. Significantly higher frequencies of GG+GA genotype and G allele of AT2R were observed in mild (80.2%, p=0.003 and 47.5%, p=0.012, respectively) and severe (77.8%, p=0.034 and 48.1%, p=0.026, respectively) preeclampsia compared to controls (60.8% and 35.1%, respectively). The presence of G allele was associated with 1.69-fold increased risk of preeclampsia (p=0.005). In severe preeclamptic women, systolic and diastolic blood pressures in the presence of GG+GA genotype were significantly higher compared to those in the presence of AA genotype. The concomitant presence of both alleles of AT2R G and AT1R C was associated with 1.3 times increased risk of mild preeclampsia (p=0.03). There was an interaction between AT2R G and ACE D alleles that significantly increased the risk of mild and severe preeclampsia by 1.38- and 1.3-fold, respectively. Also, interaction between MMP-9 T and AT2R G alleles increased the risk of severe preeclampsia 1.39-fold (p=0.028). Our study demonstrated that the G allele of AT2R -1332 G:A polymorphism is associated with an increased risk of preeclampsia. Also, epistatic interaction of G allele and each allele of the AT1R C, ACE D and MMP-9 T was associated with the risk of preeclampsia. Our findings suggest that the renin-angiotensin system (RAS) variants and gene-gene interactions affect the risk of preeclampsia.

Angiotensin II type-2 receptor-specific effects on the cardiovascular system

The renin-angiotensin system (RAS) is intricately involved in cardiovascular homeostasis. It is well known that angiotensin II, the key effector in RAS, contributes to a range of cardiovascular pathologies and diseases via angiotensin II type-1 receptor (AT1R) activation. However, the role of angiotensin II type-2 receptor (AT2R) regulation is less well understood. Recent studies describe the role of the AT2R on cardiovascular function in normal and pathologic conditions. The data describe an important role of AT2R in blood pressure regulation, cardiac hypertrophy and fibrosis, myocardial infarction and vascular homeostasis.

AT2R -1332 G:A polymorphism and diabetic nephropathy in type 2 diabetes mellitus patients

Introduction: The rennin-angiotensin system (RAS) plays a central role in the regulation of sodium metabolism, vascular tone, blood pressure, renal hemodynamics, and vascular modeling and is activated by hyperglycemiaObjectives: In the present study the influence of AT2R -1332 G:A polymorphism on the risk of T2DM and its complications in a population from Western Iran has been investigated.

Patients and Methods: In a case-control study, 70 individuals with type 2 diabetes mellitus (T2DM) including normo-, micro- and macro-albuminuric patients and 112 healthy subjects from the Kermanshah province were studied to investigate the association between the angiotensin type 2 receptor (AT2R) -1332 G:A variants with the risk of T2DM and its complications. The genotypes of the AT2R were detected using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. Analysis of AT2R -1332 G:A polymorphism indicated the absence of association between this polymorphism with T2DM and diabetic nephropathy.

Results: Analysis of AT2R -1332 G:A polymorphism indicated the absence of association between this polymorphism with T2DM and diabetic nephropathy. In females with diabetic nephropathy a significantly higher frequency of AA genotype (50%) was detected compared to those without nephropathy (13.3%, p=0.015). The presence of A allele of AT2R was associated with significantly (p=0.029) increased risk of coronary artery disease (CAD) in diabetic patients without nephropathy.

Conclusion: Our study indicated an association between the AT2R -1332 G:A polymorphism and the risk of diabetic nephropathy in females only. Also, the A allele was associated with the risk of CAD in those diabetic patients without nephropathy.

Angiotensin II type 2 receptor gene polymorphisms in cardiovascular disease

Considerable progress in our understanding of the role of the angiotensin II type 2 (AT(2)) receptor in the development of cardiac hypertrophy and coronary artery disease has been achieved using in vitro and in vivo animal models. Our understanding in humans, however, has been hindered by the lack of availability of specific AT(2) receptor agonists and antagonists suitable for human study. Nevertheless, an alternative approach involving genotyping humans for a functional polymorphism within the AT(2) receptor gene (-1332G/A) has been used in several association studies to elucidate the pathogenic role of the AT(2) receptor in cardiovascular disease. Both the A allele and the G allele have independently been associated with left ventricular remodelling. However, the methods of measuring left ventricular mass, sodium balance, age and degree of remodelling appear to influence the outcome. An association of carriers of the G allele and premature coronary artery disease has also been established, particularly in males presenting with stenotic atherosclerosis requiring revascularisation. At the molecular level, it remains unclear as to whether carriers of the G allele express more or fewer AT(2) receptors when compared to carriers of the A allele. Consequently, it is presently not possible to definitively interpret the role of the AT(2) receptor in human cardiovascular disease from these association studies.

Lack of association between the promoter polymorphism of the MTNR1A gene and adolescent idiopathic scoliosis

STUDY DESIGN

A genetic association study to investigate variation of the melatonin receptor 1A (MTNR1A) gene in adolescent idiopathic scoliosis (AIS) patients.

OBJECTIVE

To determine whether the MTNR1A gene promoter polymorphism is associated with the predisposition and/or disease severity of AIS.

SUMMARY OF BACKGROUND DATA

An involvement of the dysfunction of the melatonin pathway in the etiopathogenesis of AIS has been implicated in several studies. Recently, our group has found that the promoter polymorphism of the melatonin receptor 1B (MTNR1B) gene was associated with the occurrence of AIS. Hence, it is of interest to determine whether the promoter polymorphism of the MTNR1A gene could also associated with the occurrence or curve severity of AIS.

METHODS

A total of 226 AIS girls and 277 normal controls were recruited. SNP rs2119882 in the promoter region (-369 bp) of the MTNR1A gene was selected for the present study. Genotyping was performed by PCR-RFLP. Statistical analysis of genotype frequencies between case and control was performed by chi test. One-way ANOVA was used in comparison of mean maximum Cobb angles with different genotypes in case-only analysis.

RESULTS

Genotype and allele frequencies were comparable between case and control for SNP rs2119882 (P > 0.05). The mean maximum Cobb angles of different genotypes were similar with each other for SNP rs2119882.

CONCLUSIONS

Promoter polymorphism of the MTNR1A gene was not associated with the occurrence or curve severity of AIS. The MTNR1A gene may not be involved in the etiopathogenesis of AIS.