AT1 receptor A1166C and AT2 receptor -1332A/G gene polymorphisms: efficient genotyping by single-tube PCR

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.

The association between angiotensin II type 1 receptor A1166C gene polymorphism and the risk of essential hypertension: a meta-analysis

Background

Since first reported having the association with essential hypertension, angiotensin II type 1 receptor (AT1R) A1166C was globally investigated worldwide. However, controversy was found. Furthermore, previous meta-analyses did not adequate to clarify the precise correlation due to some limitations. Therefore, we aimed to perform a meta-analysis concerning the association between AT1R A1166C single-nucleotide polymorphism (SNP) and the risk of essential hypertension with eliminating the limitations of previous studies.

Methods

A meta-analysis was conducted from February to March 2019. Some information related to sample size of hypertension and control groups and genotype frequencies of hypertension and control groups were extracted from each study. Data were analyzed using fixed or random effect model to determine the overall correlation.

Results

A total of 45 papers consisting of 11911 cases and 1340 controls were enrolled for the study. Our overall analysis showed that C allele and AC genotype of AT1R A1166C was associated with 1.18-fold and 1.15-fold respectively increased risk of essential hypertension, while the decreased risk of essential hypertension was observed in A allele and AA genotype. In sub-group analysis, increased risk of essential hypertension was found in C allele, AC genotype, and CC genotype of both Asian population and PCR-RFLP sub-groups, while decreased risk was observed in A allele and AA genotype.

Conclusions

Our meta-analysis reveals that AT1R A1166C remains a valuable SNP having an association with the risk of essential hypertension.

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.

Expression profiling of the AT2R mRNA in affected tissue from children with CAKUT

OBJECTIVES

Congenital anomalies of the kidney and urinary tract (CAKUT) are common causes of chronic renal failure in children. The angiotensin II receptor type 2 (AT2R) is one of proposed candidate genes for CAKUT, but the expression was never explored in humans. The aim was to establish the AT2R gene expression in human CAKUT concerning -1332A/G polymorphism, which might affect alternative splicing.

DESIGN AND METHODS

Forty-eight patients with CAKUT constitute the basis of this study. Genotyping for -1332A/G, RT-PCR for AT2R gene expression and confirmation sequencing were performed.

RESULTS

The expression of Ex 1/2/3 and Ex 1/3 transcript splice variants of the AT2R mRNA were detected in human CAKUT tissue. The pattern was observed independently of A to G transition.

CONCLUSIONS

The expression of AT2R mRNA in human CAKUT was established for the first time and was not affected by -1332A/G polymorphism in children with CAKUT.

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

BACKGROUND

The role of AT2R in regulation of blood pressure (BP) was mainly investigated in animal models. It is proposed to be a negative regulator of BP. X-linked AT2R -1332 A/G polymorphism has been denoted as functional. This polymorphism was associated with certain cardiovascular phenotypes in hypertensive patients, but it was poorly investigated in essential hypertension. The aim of our study was to evaluate possible association of -1332 A/G gene polymorphism with essential hypertension in males from Serbian population.

METHODS

The study group included 304 men of Caucasian origin, 190 normotensive (NT) and 114 hypertensive (HT), free of cardiovascular disorders. Genotyping was done by PCR RFLP method.

RESULTS

G/- genotype was in association with HT (OR 1.6, CI=1.0-2.6, p=0.04). Stratification by age (<40 years, mean 31.65+/-5.29 and >40 years, mean 51.36+/-8.32) pronounced significance only in older males (OR 2.4, CI=1.2-5.0, p=0.02). After adjustment for confounding factors the OR for hypertension remained unchanged and significant (adjusted OR 2.3, CI=1.0-5.4, p=0.04).

CONCLUSION

Hemizygosity for the G allele was found to be susceptibility factor for hypertension in males. Still, clarifying the role of AT2R in development of human hypertension requires further replication studies in larger and different populations.

Risk factors of atherosclerosis: A review of genetic epidemiology data from a Serbian population

Determining common risk factors for the onset and progression of atherosclerosis and cardiovascular diseases, which are known to be multi-factorial and polygenic diseases, represents a challenge for medicine in the future. In recent years, there have been breakthroughs in the determination of pathogenesis, risk estimating methodologies, modifications of genetic risk in prophylaxis and in establishing new therapeutic targets in pharmacology. The role of genetic epidemiology is to provide necessary data about genetic characteristics of different populations, as well as gene-gene and gene-environment interactions, that lead to the development of diseases. The aim is to define high-risk haplotypes and primary targets for a new generation of pharmaceutical products and tools designed for the diagnosis and therapy of these disorders. The present review provides examples from the authors' genetic epidemiology studies regarding the association of candidate genes with risk factors of atherosclerosis, such as dyslipidemias, hypertension and diabetes mellitus, in a Serbian population, along with basic assumptions that come with this type of research. The main results of these studies are discussed, as well as problems that should be taken into consideration in future evaluations of disease risk in a population.