Essential arterial hypertension and polymorphism of angiotensinogen M235T gene

Several candidate genes, chosen from the renin‐ angiotensin system, were examined for their association with essential hypertension. The genes of the renin‐ angiotensin system (RAS) are good candidates for such an approach because this system is well known to be involved in the control of blood pressure. One of these candidate genes is the gene encoding for angiotensinogen (the most important gene of the RAS associated with essential hypertension in the most population, is the gene for angiotensin‐converting enzyme‐ ACE). One DNA polymorphism within exon 2‐ with threonine instead of methionine at position 235 (M235T) was found to be significantly associated with hypertension. The objective of this study is the analysis of M235T polymorphism in angiotensinogen gene in Romanian patients with essential hypertension as well as controls. We examined 38 patients with essential hypertension and 21 normotensive patients. In order to identify the M235T angioteninogen variant, we used the following methods: DNA extraction, PCR amplification and enzymatic digestion of the PCR product using Tth IIII restriction endonuclease enzyme. In the study groups, the M235T variant (Met?Thr in aminoacid position 235) was found more frequently in hypertensive patients (81,57%), than in control subjects (66,66%). We identified 52,63% M235T heterozygotes in the hypertensive group compared with 47,61% in the control group, and 28,94% T235T homozygotes in the hypertensive group compared with 19,04% in the control group. The results of our study suggest an association of the M235T polymorphism in the gene encoding angiotensinogen with essential hypertension     

Variation at the M235T locus of the angiotensinogen gene and essential hypertension: a population-based case-control study from Rochester,Minnesota

A variant of the angiotensinogen gene, M235T, has been associated with essential hypertension in selected subjects from Paris, France and Salt Lake City, Utah. In the present report, we studied a population-based sample consisting of 104 subjects diagnosed with hypertension before age 60 and 195 matched normotensive individuals from Rochester, Minnesota. We determined whether there was a relationship between the M235T polymorphism of the angiotensinogen gene and the occurrence of essential hypertension using two methods. First, a contingency chi-square analysis was carried out to test for an association between the M235T polymorphism and hypertension status. Second, multivariable conditional logistic regression was used to determine whether variation at the M235T polymorphism was a significant predictor of the probability of having essential hypertension. We detected no statistically significant association between the M235T polymorphism and the occurrence of essential hypertension. In particular, the association was not significant in either gender or in a subset of severely hypertensive subjects requiring two or more anti-hypertensive medications. Furthermore, variation in the number of M235T alleles did not make a significant contribution to predicting the probability of having essential hypertension, either alone or in conjunction with other predictor variables. These results suggest that the contribution of variation in the angiotensinogen gene to the occurrence of essential hypertension is less than initially suspected, or may not be constant across populations.     

Angiotensinogen T174M and M235T Variants and Hypertension in the Hani and Yi Minority Groups of China

A case–control study of 538 individuals investigated whether the angiotensinogen gene (AGT) might be implicated in the pathogenesis of essential hypertension in the Hani and Yi populations of China. Genotypes for two diallelic DNA polymorphisms observed at amino acid residues 174 (T174M) and 235 (M235T) within the coding sequence were determined. M235T and T174M genotyping with PCR-RFLP was performed in 267 normotensive subjects and 271 hypertensive subjects. No significant difference was found between normotensives and hypertensives in genotype distribution and allele frequency for either M235T or T174M in the Hani or the Yi populations (P > 0.05). Relative to carriers of the 235T/235T and 174T/174T combination, the others had a significantly elevated risk of hypertension (OR = 1.62, 95% CI 1.02–2.59; P = 0.043) in the Hani population. The AGT M235T and T174M variants in combination may play a role in the genetic predisposition to develop essential hypertension in the Hani minority of China.     

Gene polymorphisms of the renin-angiotensin-aldosterone system and essential arterial hypertension in childhood

In order to investigate the contribution of candidate genes in the renin-angiotensin-aldosterone system (RAAS) in pathogenesis of essential arterial hypertension (EAH), the I/D polymorphism of ACE gene, the M235T polymorphism of the angiotensinogen gene, and the angiotensin II type 1 receptor (AGT,R) A1166C gene polymorphism in a group of children with EAH were analyzed. Fifty-scven children, aged 8-19 years. with the diagnosis of EAH were included in the association study and were compared with 57 subjects with normal blood pressure (the control group). Arterial hypertension was defined as systolic/diastolic blood pressure measurements higher than 95 age-gender-height percentile of the adopted reference values. A trend was found towards an association between the M235T angiotensinogen gene polymorphism and EAH in childhood in a dominant model (odds ratio (OR) 2.1; 95% confidence interval (CI) 0.9-5.1; P = 0.077), whereas the authors failed to demonstrate an association between the ACE I/D gene polymorphism, or the A1166C AGT1R gene polymorphism and EAH in childhood. Additionally, evidence was found of interaction between the angiotensinogen-TT genotype and obesity on the risk of EAH in childhood (OR 19.3; 95% CI 1.1-77.3; P = 0.014). In conclusion, the M235T angiotensinogen gene polymorphism is considered alone as well as in interaction with obesity to be risk factors for EAH in childhood.     

Cardiovascular diseases and molecular variants of the renin-angiotensin system components in Slovak population

Cardiovascular diseases associated with molecular variants of individual components of renin-angiotensin system are reported to constitute inherited predisposition in humans. Molecular variant frequencies are race- and population-dependent. We examined frequencies of the M235T variant of angiotensinogen gene and I/D polymorphism of gene for angiotensin-converting enzyme in Slovak population: in hypertensive patients, coronary heart disease (CHD), dilated cardiomyopathy (DCM) and myocardial infarction (MI) patients compared to healthy subjects. Frequency of M235T was significantly increased in hypertensive, CHD and DCM patients compared to controls (0.48 and 0.50 vs. 0.40, p < 0.001). Significant increase in D allele frequency compared to controls was observed in the group of patients after MI (0.58 vs. 0.50, p < 0.001), CHD (0.59 vs. 0.50, p < 0.001) and DCM (0.60 vs. 0.50, p < 0.001). These results correlate with other Caucasian populations. In Slovak population, M235T is associated with increased blood pressure and D allele of ACE gene is associated with MI, chronic CHD and DCM, rather than with hypertension. Our results suggest that in Slovak population, D alelle and M235T variant represent a risk factor for several cardiovascular diseases and these polymorphisms might have a cumulative effect on development of cardiovascular diseases.     

Insertion/Deletion Polymorphism on ACE Gene is Associated with Endothelial Dysfunction in Young Patients with Hypertension.

Endothelial dysfunction, insulin resistance (IR) and genetic predispositions are important risk factors of hypertension. Aim of our study was to test the hypothesis, whether insertion/deletion (I/D) polymorphism on the angiotensin converting enzyme (ACE) gene and M235T polymorphism on angiotesinogen gene (AGT) correlates with parameters of insulin sensitivity and plasminogen activator inhibitor (PAI-1) levels in newly diagnosed hypertensive patients as compared with normotensive controls. Blood pressure (BP), fasting plasma glucose, insulin, epinephrine, norepinephrine and PAI-1 concentrations were determined in 30 male patients with hypertension grade 1 (HT) and in 31 matched healthy subjects (NT). Insulin resistance was estimated using IR HOMA formula. Patients with HT had increased levels of PAI-1, norepinephrine, fasting plasma insulin levels, IR HOMA (p<0.001) compared to controls. Subjects (HT and NT) with DD and ID genotype had a significantly higher systolic BP (p<0.05) and PAI-1 compared to those with II genotype. Homozygous subjects 235T had a higher systolic BP and higher levels of epinephrine and norepinephrine than heterozygous or homozygous M235 (p<0.05). In conclusion, no association was found between M235T polymorphism and insulin resistance or PAI-1 levels, but results indicate relationship between I/D polymorphism of the ACE gene and plasma PAI-1 levels in the early stage of hypertension.     

The angiotensinogen gene M235T polymorphism and acute myocardial infarction risk: a meta-analysis of 22 studies

Angiotensinogen, one of the most important proteins in the renin–angiotensin system, plays a key role in the progress of coronary heart disease and myocardial infarction (MI). Many studies have investigated the association between angiotensinogen gene M235T polymorphism and MI risk, but the results were inconsistent. We performed a meta-analysis of 22 studies on M235T polymorphism and MI risk published before November 2012. This meta-analysis included a total of 4,606 MI cases and 4,918 controls. Overall, the per-allele odds ratio (OR) of the 235T variant for total MI risk was 1.04 (95 % CI 0.92–1.17). When a recessive model was evaluated, the OR was 1.06 (95 % CI 0.96–1.17) and under a dominant model, the OR was 0.96 (95 % CI 0.82–1.11). Under pairwise comparisons, non-significant associations were found between M235T polymorphism and MI risk (MT vs. MM, OR, 0.96, 95 % CI 0.87–1.06; TT vs. MM, OR, 1.03, 95 % CI 0.83–1.28). Subgroup analyses in the different ethnic groups and different control sources were performed and no significant association was found also. Based on the available evidence, no association between M235T polymorphism and MI risk was observed, even in the sub-analysis concerning different races and control sources. The direction of further research should focus not only on the simple relationship of M235T polymorphism and MI risk, but also on gene–gene and gene-environment interaction.     

Impact of angiotensin-converting enzyme, angiotensinogen, endothelial NO synthase, and bradykinin receptor B2 gene polymorphisms on myocardium in patients with hypertension and in athletes

We investigated the role of gene polymorphisms in angiotensin-converting enzyme (ACE), angiotensinogen, endothelial NO (eNO) synthase, and bradykinin receptor B2 in determining the cardiovascular system structure and function in hypertension and "athletic heart" syndrome. Using a PCR-based method, 114 hypertensive patients and 94 athletes were genotyped for I/D polymorphism of ACE, M235T angiotensinogen (ANG), Glu298 Asp endothelial synthase (eNOS), and type 2 receptor for bradykinin (BDKR2). Echocardiography and a 24 hour blood pressure monitoring being performed. The (+)-allel of BDKR2 gene was associated with the left ventricular hypertrophy and greater wall thickness in athletes and hypertensive subjects. The hypertensive patients, that were homozygous for Glu298 allele of eNOS, demonstrated a lower level of diastolic blood pressure than did those with Glu298 Asp and Asp298 Asp genotypes. At the same time, the ACE and AND gene polymorphisms displayed no association with the cardiac structure and function.     

Gene variation in resistant hypertension: multilocus analysis of the angiotensin 1-converting enzyme, angiotensinogen, and endothelial nitric oxide synthase genes

Resistant hypertension, a complex multifactorial hypertensive disease, is triggered by genetic and environmental factors and involves multiple physiological pathways. Single genetic variants may not reveal significant associations with resistant hypertension because their effects may be dependent on gene-gene or gene-environment interactions. We examined the interaction of angiotensin I-converting enzyme (ACE), angiotensinogen (AGT), and endothelial nitric oxide synthase (NOS3) polymorphisms with environmental factors (gender, age, body mass index, glycemia, total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglycerides, estimated glomerular filtration rate, and urinary sodium excretion) in 70 resistant, 80 well-controlled hypertensive patients, and 70 normotensive controls. All subjects were genotyped for ACE insertion/deletion (rs1799752); AGT M235T (rs699), and NOS3 Glu298Asp (rs 1799983). Multifactorial associations were tested using two statistical methods: the traditional parametric method (adjusted logistic regression analysis) and gene-gene and gene-environment interactions evaluated by multifactor dimensionality reduction analyses. While adjusted logistic regression found no significant association between the studied polymorphisms and controlled or resistant hypertension, the multifactor dimensionality reduction analyses showed that carriers of the AGT 235T allele were at increased risk for resistant hypertension, especially if they were older than 50 years. The AGT 235T allele constituted an independent risk factor for resistant hypertension.     

Relations of blood pressure to angiotensinogen gene T174M polymorphism and alcohol intake

To clarify the interactive effects of alcohol intake and angiotensinogen gene codon 174 (T174M) polymorphisms on blood pressure in Japanese male workers. On the basis of data from health examinations, nutrition survey and T174M genotype analysis conducted for 185 Japanese male workers at 2000, the prevalence of high-normal blood pressure (HNBP) and hypertension were compared between the four subgroups crossed by two T174M genotype categories ('TT' type, and 'TM or MM' type) and two alcohol intake categories (less than 13.7 g per day, and 13.7 g or more per day). Furthermore, for 95 subjects who had been normotensive at 1998 among them, risk of development into HNBP or hypertension at 2000 were compared across the four subgroups. The findings showed that the HNBP prevalence adjusted for age, body mass index, smoking habits and sodium intake in 2000 was significantly (p=0.03) greater in 'TM or MM' type (57.9%) than in 'TT' type (24.9%) in subjects with 13.7 g or more of daily alcohol intake, whereas no difference in this parameter was found between the two genotypes in those with less than 13.7 g of daily alcohol intake (18.2% and 18.3%, respectively). The risk for development into HNBP at 2000 was also greatest in 'TM or MM' type with 13.7 g or more of daily alcohol intake among the four subgroups, although there were not significant differences between the four subgroups. The prevalence of hypertension or development risk for hypertension did not significantly differ between the four subgroups. Therefore, it can be seen that alcohol drinking might be specifically associated with the HNBP in M allele carriers of angiotensinogen gene T174M polymorphism.     

Polymorphism T174M of the angiotensinogen gene in Siberian populations

The level of T174M polymorphism of the angiotensinogen gene (AGT) was studied for the first time in Siberian populations. The frequency of allele M was found to be 7% in Russians, 6% in Tuvinians, and 4% in Buryats. In the Mongoloid population of Siberia (Tuvinians and Buryats), the genotypic frequencies deviated from Hardy-Weinberg equilibrium (P < 0.05). The studied polymorphism of the AGT gene determined in Siberian populations was compared with that of other ethnic groups in the world population, and genetic distinctions were estimated. Only the Buryat population was found to differ significantly from the French, English, and Chinese in the frequency of allele M. No association between the T174M polymorphism of the AGT gene and pathological pregnancy (gestosis) was revealed in Buryat women.     

Nine polymorphisms of angiotensinogen gene in the susceptibility to essential hypertension

Even if the importance of angiotensinogen (AGT) gene has been known in gene targeting animals and humans genetic studies, its precise mechanism and the interaction among AGT gene variants, plasma AGT concentration and risk for hypertension remain uncertain. We examined whether AGT gene variants predispose to hypertension via an increase of plasma AGT concentration. Plasma AGT concentration was estimated from plasma angiotensin I which was cleaved by an excess amount of human renin and measured by RIA. Using 9 AGT gene variants which included new polymorphisms (G-152A and T+31C), we examined the association with hypertension and with plasma concentration by a case-control study. Haplotype analysis revealed that G-6A, T+31C and M235T polymorphisms were in absolute linkage disequilibrium and were associated with hypertension but not with plasma AGT level. On the other hand, -1074t;T235 haplotype was associated with an increase of AGT level but not with hypertension. In the haplotype analysis, only H3 haplotype frequency, which contained G-6, T+31 and M235 alleles, was significantly increased in normotensive subjects, suggesting that this haplotype is associated with a hypotensive effect. According to combined haplotype analysis of diallele and microsatellite markers, it remains a possibility that M235T, T+31C, G-6A, A-20C and G-1074T polymorphisms may play an important role in increased risk for essential hypertension. Our results suggest that the positive association between AGT polymorphism and hypertension is not simply explained by an increase of plasma AGT concentration.     

Nucleotide Diversity and Haplotype Structure of the Human Angiotensinogen Gene in Two Populations

Variation in the angiotensinogen gene, AGT, has been associated with variation in plasma angiotensinogen levels. In addition, the T235M polymorphism in the AGT product is associated with an increased risk of essential hypertension in multiple populations, making AGT a good example of a quantitative-trait locus underlying susceptibility to a common disease. To better understand genetic variation in AGT, we sequenced a 14.4-kb genomic region spanning the entire AGT and identified 44 single-nucleotide polymorphisms (SNPs). Forty-two SNPs were observed both in 88 white and in 77 Japanese unselected subjects. Six major haplotypes accounted for most of the variation in this region, indicating less allelic complexity than in many other genomic regions. Although the two populations were found to share all of the major AGT haplotypes, there were substantial differences in haplotype frequencies. Pairwise linkage disequilibrium (LD), measured by the D', r(2), and d(2) statistics, demonstrated a general pattern of decline with increasing distance, but, as expected in a small genomic region, individual LD values were highly variable. LD between T235M and each of the other 39 SNPs was assessed in order to model the usefulness of LD to detect a disease-associated mutation. Among the Japanese subjects, 13 (33%) of the SNPs had r(2) values >0.1, whereas this statistic was substantially higher for the white subjects (occurring in 35/39 [90%]). LD between a hypertension-associated promoter mutation, A-6G, and 39 SNPs was also measured. Similar results were obtained, with 33% of the SNPs showing r(2)>0.1 in the Japanese subjects and 92% of the SNPs showing r(2)>0.1 in the white subjects. This difference, which occurs despite an overall similarity in LD patterns in the two populations, reflects a much higher frequency of the M235-associated haplotype in the white sample. These results have important implications for the usefulness of LD approaches in the mapping of genes underlying susceptibility to complex diseases.     

Angiotensinogen and angiotensin-I converting enzyme gene polymorphisms and the risk of coronary artery disease in Chinese

The homozygous deletion allele (DD) of the angiotensin-I converting enzyme (ACE) gene and the T235 homozygote of the angiotensinogen (AGT) gene have been reported to be correlated with an increased prevalence of coronary artery disease (CAD) and myocardial infarction (MI). The importance of the DD genotype and T235 homozygote as genetic risk factors for CAD in Chinese remains uncertain. This study included 426 patients who underwent coronary angiography and 180 healthy subjects without clinical evidence of CAD. Coronary angiography identified 268 patients with CAD (CAD group) and 158 patients without CAD. The healthy subjects and patients without angiographic evidence of CAD constituted the control group. Three polymorphisms were studied: an insertion/deletion (I/D) polymorphism of the ACE gene and the T174 M and M235T polymorphisms of the AGT gene. No association was found between any of the three studied polymorphisms and the risk of CAD or MI in Chinese using univariate or multivariate analysis. In multivariate analysis, the relative risks were 1.20 (95% confidence interval = 0.91–1.61, P = 0.20) for the DD genotype, 1.05 (95% CI = 0.82–1.35, P = 0.69) for the T174 homozygote, and 1.19 (95% CI = 0.91–1.55, P = 0.20) for the T235 homozygote. Similarly, no significant difference was found in the frequencies of the DD genotype and the T174 and T235 homozygotes between the control group, the CAD group, the non-MI group, and the MI group when analyzed according to sex, age, or degree of risk. Our data suggest that neither the DD genotype of the ACE I/D polymorphism nor the T174 and T235 homozygotes of the AGT gene confer significant risk for CAD or MI in Chinese. Received: 18 December 1996 / Accepted: 27 February 1997     

Body Fat,Resting and Exercise Blood Pressure and the Angiotensinogen M235T Polymorphism: The Heritage Family Study

RANKINEN, T., JACQUES GAGNON, LOUIS PÉRUSSE, TREVA RICE, ARTHUR s. LEON, JAMES s. SKINNER, JACK H. WILMORE, D. C. RAO, AND CLAUDE BOUCHARD. Body fat, resting and exercise blood pressure and the angiotensinogen M235T polymorphism: the Heritage family study. Obes Res. Objective: The association of resting and exercise blood pressure (BP) and fat mass with the angiotensinogen (AGT) M235T polymorphism was investigated in 522 sedentary Caucasian subjects from 99 families. Research Methods and Procedures: Resting BP was measured on two separate days, three times each day, and the mean of six valid measurements was used. Exercise BP was measured during a cycle ergometer test at a constant power output (50 W). Body composition was derived from underwater weighing and the AGT M235T polymorphism was typed with a polymerase chain reaction-based method. Results: Neither resting nor exercise BP was associated with the AGT genotypes. In mothers, the homozygotes for the T allele showed 8. 8 kg and 7. 1 kg greater (p = 0. 017) age-adjusted body fat mass (FM) than the MM homozygotes and heterozygotes, respectively. Sixty-nine percent of all TT homozygotes were found in the highest FM tertile, whereas only 16% of the MM homozygotes fell in the same tertile (p = 0. 008). Moreover, a significant interaction was seen between FM and T-allele carrier status in women with regard to resting diastolic BP (p = 0. 002). Among women with a FM≥24 kg, carriers of the T allele showed a 6. 3 mmHg higher diastolic blood pressure (DBP) than non-carriers whereas no difference was found in women with a FM less than 24 kg. A similar trend toward an interaction term was evident with resting systolic blood pressure (p = 0. 011) and exercise DBP (p = 0. 012). Body fat was not associated with the AGT polymorphism in fathers or in offspring. Discussion: These data suggest that the AGT M235T polymorphism is associated with body fatness in women, and that the relationship between DBP and AGT M235T polymorphism is dependent on FM in middle-aged sedentary normotensive women.     

Molecular basis for hypertension in the "type II variant" of apparent mineralocorticoid excess.

The syndrome of apparent mineralocorticoid excess (AME) is a heritable form of hypertension in which cortisol acts as a potent mineralocorticoid. The type I variant results in a severe clinical and biochemical phenotype and arises because of mutations in the gene encoding the type 2 isozyme of 11beta-hydroxysteroid dehydrogenase (11beta-HSD2), an enzyme responsible for the peripheral inactivation of cortisol to cortisone. Only mild abnormalities of cortisol metabolism have been found in the type II variant of AME, suggesting that it may be a separate gene defect. In an extensive consanguineous Sardinian pedigree affected with "type II" AME, a novel homozygous point mutation (C945T) was found in the human 11beta-HSD2 gene in four affected individuals. Thirteen family members were heterozygous for the resultant R279C amino acid substitution. The LOD score of linkage of the mutation to the disease was 3.23. Expression of the 11beta-HSD2 mutant cDNA resulted in an enzyme with reduced maximum velocity, but similar substrate affinity, compared with activity of the wild-type cDNA. Affected individuals were >30 years of age and had both mineralocorticoid hypertension and evidence of impaired metabolism of cortisol to cortisone. The heterozygote state was phenotypically normal but was associated with subtle defects in cortisol metabolism. AME represents a spectrum of mineralocorticoid hypertension with severity reflecting the underlying genetic defect in the 11beta-HSD2 gene; classification into distinct subtypes is inappropriate. Hypertensive populations should be screened to identify the prevalence of milder defects in 11beta-HSD2 in patients currently labeled as having "essential" hypertension.     

Hereditary deafness in Kirov oblast: estimation of the incidence rate and DNA diagnosis in children

Genetic analysis of hereditary deafness (HD) has been performed in the city of Kirov and ten rural districts of Kirov oblast (administrative region). The analysis employed the methods used in audiology, medical genetic counseling, and DNA diagnosis. Deafness has been established to be hereditary in 143 children from 100 unrelated families. The incidence rates of isolated and syndromic HDs in the period studied (1995-2001) have been estimated at 1.25 and 0.36 per 1000 newborns, respectively, the total incidence rate of all HD forms being 1.61 per 1000 newborns (1 case per 621 newborns). DNA analysis for the detection of seven frequent mutations in the genes GJB2 (the 35delG, 167delT, 235delC, and M34T mutations), GJB6 (the del(GJB6-D13S1854) and del(GJB6-D13S1830) mutations), and TMC1 (the R34X mutation) has been performed in families with isolated neurosensory deafness. Molecular genetic analysis has detected mutations in 51 children (48.6%); in 54 children (51.4%), no mutations have been found. The following genotypes have been identified in children with HD: 35delG/35delG in 32 probands (30.5%), 35delG/+ in 16 probands (15.2%), 35delG/235delC in 1 proband (0.95%), M34T/+ in 1 proband (0.95%), and M34T/35delG in 1 proband (0.95%). The 167delT mutation has not been found. The frequency of the 35delG mutation in the GJB2 gene has been estimated to be 39.05%. In the group with a family history of HD, mutations have been found in 66.7% of patients; in the group without a family history of HD, in 37.5% of patients. No mutation has been found in the GJB6 or TMC1 gene. Molecular genetic analysis has been performed in a family with clinically diagnosed Treacher Collins-Franceschetti syndrome. Sequencing has been used to find the 748-69C>T polymorphism in intron 6 (in the homozygous state) and the 3635C>G mutation in exon 23 leading to the substitution of glycine for alanine at position 1176 of the amino acid sequence (Ala1176Gly, in the heterozygous state), which have not been described before.