Angiotensinogen gene polymorphism near transcription start site and blood pressure: role of a T-to-C transition at intron I

Gene Polymorphisms of the Renin-Angiotensin System and Bleeding Complications of Warfarin: Genetic-Based Machine Learning Models

This study aimed to investigate the effects of genetic variants and haplotypes in the renin–angiotensin system (RAS) on the risk of warfarin-induced bleeding complications at therapeutic international normalized ratios (INRs). Four single nucleotide polymorphisms (SNPs) of AGT, two SNPs of REN, three SNPs of ACE, four SNPs of AGTR1, and one SNP of AGTR2, in addition to VKORC1 and CYP2C9 variants, were investigated. We utilized logistic regression and several machine learning methods for bleeding prediction. The study included 142 patients, among whom 21 experienced bleeding complications. We identified a haplotype, H2 (TCG), carrying three single nucleotide polymorphisms (SNPs) of ACE (rs1800764, rs4341, and rs4353), which showed a significant relation with bleeding complications. After adjusting covariates, patients with H2/H2 experienced a 0.12-fold (95% CI 0.02–0.99) higher risk of bleeding complications than the others. In addition, G allele carriers of AGT rs5050 and A allele carriers of AGTR1 rs2640543 had 5.0- (95% CI 1.8–14.1) and 3.2-fold (95% CI 1.1–8.9) increased risk of bleeding complications compared with the TT genotype and GG genotype carriers, respectively. The AUROC values (mean, 95% CI) across 10 random iterations using five-fold cross-validated multivariate logistic regression, elastic net, random forest, support vector machine (SVM)–linear kernel, and SVM–radial kernel models were 0.732 (0.694–0.771), 0.741 (0.612–0.870), 0.723 (0.589–0.857), 0.673 (0.517–0.828), and 0.680 (0.528–0.832), respectively. The highest quartile group (≥75th percentile) of weighted risk score had approximately 12.0 times (95% CI 3.1–46.7) increased risk of bleeding, compared to the 25–75th percentile group, respectively. This study demonstrated that RAS-related polymorphisms, including the H2 haplotype of the ACE gene, could affect bleeding complications during warfarin treatment for patients with mechanical heart valves. Our results could be used to develop individually tailored intervention strategies to prevent warfarin-induced bleeding.

Regulators of Epithelial Sodium Channels in Aldosterone-Sensitive Distal Nephrons (ASDN): Critical Roles of Nedd4L/Nedd4-2 and Salt-Sensitive Hypertension

Ubiquitination is a representative, reversible biological process of the post-translational modification of various proteins with multiple catalytic reaction sequences, including ubiquitin itself, in addition to E1 ubiquitin activating enzymes, E2 ubiquitin conjugating enzymes, E3 ubiquitin ligase, deubiquitinating enzymes, and proteasome degradation. The ubiquitin–proteasome system is known to play a pivotal role in various molecular life phenomena, including the cell cycle, protein quality, and cell surface expressions of ion-transporters. As such, the failure of this system can lead to cancer, neurodegenerative diseases, cardiovascular diseases, and hypertension. This review article discusses Nedd4-2/NEDD4L, an E3-ubiquitin ligase involved in salt-sensitive hypertension, drawing from detailed genetic dissection analysis and the development of genetically engineered mice model. Based on our analyses, targeting therapeutic regulations of ubiquitination in the fields of cardio-vascular medicine might be a promising strategy in future. Although the clinical applications of this strategy are limited, compared to those of kinase systems, many compounds with a high pharmacological activity were identified at the basic research level. Therefore, future development could be expected.

The relationship between angiotensinogen gene polymorphisms and essential hypertension in a Northern Han Chinese population

Gene polymorphisms of the renin-angiotensin system are involved in the pathophysiology of hypertension. We genotyped 4 polymorphisms of angiotensinogen (AGT) gene A-20C (rs5050), A-6G (rs5051), C3889T (rs4762), and C4072T (rs699) by polymerase chain reaction-restriction fragment length polymorphism in 652 patients and 780 controls to examine the association of AGT and hypertension in a Northern Han Chinese population. There were significant differences in the distribution of genotypes and allele frequencies at C4072T between the patients and the controls (both P < .01); patients with CC genotype had a higher risk of hypertension (odds ratio = 1.7, 95% confidence interval 1.4-2.1). The distribution of genotypes at A-6G was significantly different between patients and controls (P < .05). No other significant differences in genotypes or frequencies were observed. No association was observed between the haplotypes of AGT and hypertension. The AGT-6A and 4072C alleles are associated with susceptibility to hypertension in this population.

Risk and preventive factors of low-dose aspirin-induced gastroduodenal injuries: a comprehensive review

The risk of peptic ulcer complications, particularly bleeding, is increased in association with the use of low-dose aspirin (LDA). Risk factors for upper gastrointestinal (GI) ulcer or bleeding among LDA users include a history of prior GI events, older age, chronic renal failure, combined antithrombotic therapy and nonsteroidal anti-inflammatory drugs (NSAIDs). Helicobacter pylori and aspirin seem to be independent risk factors for peptic ulcer and bleeding. The studies report conflicting findings about the effect of H. pylori infection on NSAID-related ulcers, and proton-pump inhibitors (PPIs) seem to be superior to eradication only to prevent recurrent ulcer bleeding with LDA. Previous studies indicate that hypoacidity related to corpus atrophy, as well as taking PPIs and co-treatment with angiotensin type 1 receptor blockers (ARBs) and statins seem to reduce peptic ulcer among LDA users. In addition, the interleukin-1β (IL-1β)-511 T allele and angiotensinogen (AGT)-20 CC, which work as the high-producer allele of IL-1β and AGT, are significantly associated with ulcer or ulcer bleeding. The SLCO1B1*1b haplotype, which has the highest transport activity, may diminish the preventive effect of statins or ARBs. The data are still lacking and further prospective studies are needed to identify the specific risk or protective factors for upper GI ulcer and its complications associated with LDA.

A-6G and A-20C polymorphisms in the angiotensinogen promoter and hypertension risk in Chinese: a meta-analysis

Background

Numerous studies in Chinese populations have evaluated the association between the A-6G and A-20C polymorphisms in the promoter region of angiotensinogen gene and hypertension. However, the results remain conflicting. We carried out a meta-analysis for these associations.

Methods and Results

Case–control studies in Chinese and English publications were identified by searching the MEDLINE, EMBASE, CNKI, Wanfang, CBM, and VIP databases. The random-effects model was applied for dichotomous outcomes to combine the results of the individual studies. We finally selected 24 studies containing 5932 hypertensive patients and 5231 normotensive controls. Overall, we found significant association between the A-6G polymorphism and the decreased risk of hypertension in the dominant genetic model (AA+AG vs. GG: P = 0.001, OR = 0.71, 95%CI 0.57–0.87, P_{heterogeneity} = 0.96). The A-20C polymorphism was significantly associated with the increased risk for hypertension in the allele comparison (C vs. A: P = 0.03, OR = 1.14, 95%CI 1.02–1.27, P_{heterogeneity} = 0.92) and recessive genetic model (CC vs. CA+AA: P = 0.005, OR = 1.71, 95%CI 1.18–2.48, P_{heterogeneity} = 0.99). In the subgroup analysis by ethnicity, significant association was also found among Han Chinese for both A-6G and A-20C polymorphisms. A borderline significantly decreased risk of hypertension between A-6G and Chinese Mongolian was seen in the allele comparison (A vs. G: P = 0.05, OR = 0.79, 95%CI 0.62–1.00, P_{heterogeneity} = 0.84).

Conclusion

Our meta-analysis indicated significant association between angiotensinogen promoter polymorphisms and hypertension in the Chinese populations, especially in Han Chinese.

Renin-angiotensin system associated with risk of upper GI mucosal injury induced by low dose aspirin: renin angiotensin system genes' polymorphism

BACKGROUND

We have previously shown that co-treatment of angiotensin type 1 receptor (AT1R) blocker (ARB) or angiotensin converting enzyme (ACE) inhibitor seem to reduce peptic ulcer among patients taking low dose aspirin. It is reported that a series of renin-angiotensin system (RAS) gene polymorphisms significantly influence the rate of the gene transcription.

AIM

The aim of this study was to examine the genotypes of RAS genes related to the risk of peptic ulcer and ulcer bleeding among patients taking low dose aspirin.

METHODS

Patients taking 100 mg of aspirin who were planning to undergo endoscopy for surveillance or who had history of recent upper GI ulcer bleeding were included. ACE (Ins/Del), angiotensinogen (AGT; G-217A, A-20C, A-6G, T174 M, M235T), and AT1R (T-713G, C-521T, A1166C) genotypes were determined by PCR or PCR-RFLP.

RESULTS

Four hundred twenty-five patients were enrolled including 68 patients with peptic ulcer and 20 patients with ulcer bleeding. Co-treatment of ARB was significantly associated with peptic ulcer and ulcer bleeding. AGT-20 CC (adjusted OR 4.94, 95% CI 1.21-20.2) was significantly associated with ulcer bleeding. The CC genotype of AT1R-521 was significantly associated with peptic ulcer only in the subgroup taking neither ACE inhibitor nor ARB.

CONCLUSIONS

Co-treatment of ARB reduces peptic ulcer and bleeding among patients taking low dose aspirin. RAS may play an important role in the development of upper GI mucosal injury induced by low dose aspirin.

Obesity and the renin- angiotensin-aldosterone system

The renin-angiotensin-aldosterone system (RAAS) is a key regulator of cardiovascular function. RAAS activity is upregulated in obesity despite concurrent renal sodium retention, which is a hallmark and principle determinant of obesity-associated hypertension. The contribution of adipose tissue to increased angiotensinogen and aldosterone plasma levels in obesity is probably due to the secretion of angiotensinogen and, as yet, unidentified aldosterone secretagogues by adipocytes. Increased circulating renin activity, on the other hand, is probably due to increased sympathetic activity in the obese. Modest weight reduction significantly reduces RAAS activity by uncertain mechanisms. Pharmacological blockade of the RAAS yielded promising results, both with regard to cardiovascular function and metabolic complications of obesity. These studies suggest that the activated RAAS is a prime pharmacological target for reducing the cardiometabolic risk in obese patients.

Detection and characterization of DNA variants in the promoter regions of hundreds of human disease candidate genes

Understanding genetic variation might reveal the cause of individual susceptibility to a variety of complex diseases such as asthma, diabetes, and cancer. Current efforts to identify functional DNA variants have essentially been oriented toward single nucleotide polymorphisms (SNPs) found in coding regions of candidate genes since they have direct impact on the structure and function of the affected proteins. Abnormal expression of finely regulated genes could also lead to disequilibria in different metabolic pathways and/or biological processes. Thus investigation of SNPs in the promoter regions (pSNPs) of genes should improve our knowledge of the etiology of complex diseases. Unfortunately, little is known about the nature and the prevalence of pSNPs. We have analyzed 197 genes targeting the promoter region, arbitrarily defined as a 2-kb genomic segment upstream of the transcription initiation site, by screening by dHPLC for the presence of SNPs in a worldwide panel of 40 individuals. As a result 1838 pSNPs were detected, 75% of which modify (by either gain or loss) putative binding sites of known transcription factors. We also examined the distribution of these pSNPs among features such as conserved regions, repeats, and dinucleotides as well as Gene Ontology terms. This report supports the functional relevance of several of the pSNPs investigated and suggests a putative impact on disease susceptibility.

Significance of urinary angiotensinogen in essential hypertension as a function of plasma renin and aldosterone status

OBJECTIVE

This study was performed to test the significance of urinary angiotensinogen (UAGT) in essential hypertensive patients stratified as a function of plasma renin and aldosterone.

METHODS AND RESULTS

A sample of 248 essential hypertensives, investigated under their usual sodium diet and either off-medication or under a standardized treatment, was separated into two groups on the basis of upright plasma active renin and aldosterone medians. Patients with plasma active renin and aldosterone below medians are referred to as the low renin-aldosterone essential hypertensive group (LRA-EH). Others subjects are defined as other essential hypertensives (O-EH). Blood pressure (BP) was recorded by 24-h ambulatory monitoring. UAGT was measured by a specific enzyme-linked immunosorbent assay for total angiotensinogen. Because UAGT was markedly increased in the presence of overt proteinuria (>/= 300 mg/24 h), proteinuric patients (n = 29) were excluded from subsequent analyses. UAGT was a significant predictor of systolic and diastolic BP in LRA-EH females (P < 0.01 and P = 0.05, respectively) but not in males. By contrast, urinary sodium excretion (P < 0.001) and maintenance of treatment (P = 0.002) were significant predictors of systolic BP in males. These correlations were not observed in O-EH, whether males or females.

CONCLUSIONS

In the present study, UAGT stands as a strong predictor of BP in women with low plasma renin/aldosterone, suggesting an involvement of the tubular renin-angiotensin system in these subjects. Higher sodium intake or the need to maintain treatment may account in part for the lack of a similar relationship in males.

Single nucleotide polymorphisms predict the change in left ventricular mass in response to antihypertensive treatment

BACKGROUND

Our aim was to determine whether the change in left ventricular (LV) mass in response to antihypertensive treatment could be predicted by multivariate analysis of single nucleotide polymorphisms (SNPs) in candidate genes reflecting pathways likely to be involved in blood pressure control.

METHODS

Patients with mild to moderate primary hypertension and LV hypertrophy were randomized in a double-blind fashion to treatment with either the angiotensin II type 1 receptor antagonist irbesartan (n = 48) or the beta1 adrenoreceptor blocker atenolol (n = 49). A microarray-based minisequencing system was used for genotyping 74 SNPs in 25 genes. These genotypes were related to the change in LV mass index by echocardiography, after 12 weeks treatment as monotherapy, using stepwise multiple regression analysis.

RESULTS

The blood pressure reductions were similar and significant in both treatment groups. Two SNPs in two separate genes (the angiotensinogen T1198C polymorphism, corresponding to the M235T variant and the apolipoprotein B G10108A polymorphism) for those treated with irbesartan, and the adrenoreceptor alpha2A A1817G for those treated with atenolol, significantly predicted the change in LV mass. The predictive power of these SNPs was independent of the degree of blood pressure reduction.

CONCLUSION

SNPs in the angiotensinogen, apolipoprotein B, and the alpha2 adrenoreceptor gene predicted the change in LV mass during antihypertensive therapy. These results illustrate the potential of using microarray-based technology for SNP genotyping in predicting individual drug responses.

Role of two angiotensinogen polymorphisms in blood pressure variation

Genetic analysis of hypertension has yielded inconsistent results, making it difficult to draw clear conclusions regarding the impact of specific variants on blood pressure regulation. Among the most studied of the candidate genes for blood pressure regulation is angiotensinogen (AGT), but as with other candidate loci associations with blood pressure have been inconsistent. We examined the contributions of two AGT polymorphisms (T174M and M235T) to detect the effects of each on blood pressure variation, using single-site and two-site analyses. We analysed data from a study of 177 subjects from Accra, Ghana. We observed significant single-locus associations of the T174M polymorphism with average systolic (SBP) and diastolic blood pressure (DBP) when age was used as a covariate (P<0.001 and P=0.010, respectively). Also, we observed a significant association of the M235T polymorphism with SBPs and DBPs (P<0.001 and P=0.014, respectively). Finally, we observed a simultaneous significant association of the two polymorphisms with SBP and DBP (P<0.001 and P=0.026, respectively), although the two-loci model is not significantly better than either single-locus model. However, for SBP the two-loci model is marginally better (P=0.08 in comparison to both single-locus models). These results suggest that variants at these two AGT sites together, in conjunction with age, may be significantly associated with elevated SBP, whereas the single-site models are as good models of DBP. It is possible that earlier inconsistent results with these AGT polymorphisms with hypertension in African-derived populations may have resulted from an 'incomplete' model in the different study populations. Given the inconclusive nature of our two-loci results, this possibility requires further investigation.

Genotyping the -6A/G functional polymorphism in the core promoter region of angiotensinogen gene by microchip electrophoresis

Angiotensinogen (AGT) gene has been regarded as one of the candidate genes for essential hypertension. In our study, the role of AGT gene as a putatively predisposing gene for hypertension was evaluated by genotyping a A (-6) G polymorphism in the core promoter region in 123 patients with essential hypertension and 103 healthy controls. A microchip electrophoresis method coupled with polymorphism chain reaction (PCR)-restriction fragment length polymorphism (RFLP) assay was used for genotyping the A (-6) G single-nucleotide polymorphism. The separation and detection of the digested PCR amplicons were completed just in 280 s or less. The genotype frequency fulfilled the criteria of the Hardy-Weinbery equilibrium (X2 = 3.067, P > 0.05). The results showed a higher frequency of the -6 A allele (0.70) in the normotensive subjects, which is higher than those reported in Germany (0.47) and Czech (0.40) populations, but similar to that found in Japanese populations (0.73). The frequencies of genotype AA, AG, and GG were 0.46, 0.49, and 0.05 in hypertensive subjects, and 0.44, 0.53, and 0.03 in control subjects. There is no significant difference in the distributions of the genotype and allele between the two groups (X2 = 0.88, P > 0.05; X2 = 0.024, P > 0.05). These findings differ from some of the results obtained in other ethnic groups, indicating the potential importance of ethnic origin in the assessment of genetic risk identifiers for a complex disease.

Polymorphisms of the angiotensinogen gene and the outcome of microalbuminuria in essential hypertension: a 3-year follow-up study

BACKGROUND

The objective of this study was to analyse the relationship of polymorphisms of the angiotensinogen (AGT) gene with the changes in microalbuminuria during 3 years of antihypertensive treatment in a group of young adults with essential hypertension.

METHODS

Essential hypertensives, less than 50 years old, never previously treated with antihypertensive drugs and in the absence of diabetes mellitus were included. After the initial evaluation, patients were treated using only nonpharmacological measures (n=23), only beta-blockers (n=26), only angiotensin-converting enzyme inhibitors (ACEi) (n=57) or a combination of treatments (n=25). The office blood pressure, biochemical profile and urinary albumin excretion (UAE) were measured at the beginning and then yearly. The polymorphism A-6G of the AGT gene located in the promoter region was analysed.

RESULTS

In total, 131 patients, 35 (27%) microalbuminurics, were included. Although no significant differences in systolic blood pressure (SBP), diastolic blood pressure (DBP), fasting glucose and UAE were observed among genotypes at the initial examination, during the 3 years of antihypertensive treatment the slope values for the DBP, fasting glucose and UAE differed significantly despite no differences in the distribution of treatments being present. The subjects carrying the AA-6 genotype had the largest DBP decrease, but the lowest UAE reduction and the highest slope of glucose. Out of 35 initially microalbuminuric patients, 24 became normoalbuminuric and the lowest reduction rates were observed in subjects who carried the allele A-6. No interaction between the type of treatment and genotype was observed on the changes in UAE, BP or glucose values. In the subset of 57 patients treated with ACEi, the changes in UAE, BP and glucose had the same trend as was observed in the total population.

CONCLUSIONS

Subjects carrying the AA genotype of the A-6G AGT gene polymorphism are resistant to a reduction of microalbuminuria. Whether this can be attributed to a predisposition to glucose metabolic disturbance or not needs to be confirmed in further studies.

The G???217A variant of the angiotensinogen gene affects basal transcription and is associated with hypertension in a Taiwanese population

OBJECTIVE

Polymorphisms of the angiotensinogen (AGT) gene, especially in the promoter region, are in linkage concordance and are associated with hypertension. In this study, we examined the role of AGT promoter polymorphisms, including G-217A, A-6G and M235T variants, and their promoter function in essential hypertension in Taiwanese populations.

DESIGN

An association study was conducted to assess the genotype distribution between hypertensive patients and normotensive subjects. We also used a transient transfection assay to examine basal transcriptional activity of G-217A and A-6G variants in a mammalian cell system.

METHODS

Hypertensive subjects (390) and normotensive controls (388) of Taiwanese ethnicity were genotyped for the AGT G-217A, A-6G and M235T variants. Promoter activity was studied by cloning the promoter region (-614 to +41 bp) of AGT into the pSEAP2-Basic reporter vector and performing a transient transfection assay in HuH7 and HepG2 cells.

RESULTS

The G-217A variant of the AGT gene was significantly associated with hypertension (P = 0.0047), but the A-6G and M235T polymorphisms were not (P = 0.17 and P = 0.33, respectively). Furthermore, the recessive model of homozygous genotype (-217AA) conferred a high risk for hypertension (odds ratio 3.64) in this population. The -217A variant expressed higher transcriptional activity than -217G in vitro.

CONCLUSIONS

Our study showed a significant association between the -217A variant of the AGT gene and hypertension. This variant plays a functional role in basal transcription of AGT, and may confer a risk for hypertension in Taiwanese populations.

Angiotensinogen gene variation and renoprotective efficacy of renin-angiotensin system blockade in IgA nephropathy

BACKGROUND

Blockade of the renin-angiotensin system (RAS) is well documented to be renoprotective; however, not all patients with glomerulonephritis respond well to this therapy. The interindividual variation in response to the RAS blockade may be in part genetically determined, whereas the results have been controversial.

METHODS

We investigated whether the therapeutic efficacy of angiotensin-converting enzyme (ACE) inhibitors and/or angiotensin receptor blocker on renal prognosis is modified by the angiotensinogen gene (AGT) polymorphism in immunoglobulin A nephropathy (IgAN). In total, 259 patients with histologically proven IgAN were analyzed for clinical manifestations, renal survival, and their associations with AGT A(-20)C and M235T.

RESULTS

The renal prognosis of 110 patients, who received ACE inhibitors/angiotensin receptor blocker during their clinical course, was significantly better than those without ACE inhibitors/angiotensin receptor blockers despite higher blood pressures and heavier proteinuria. The Cox proportional hazards regression model showed an increased hazard ratio (HR) for urinary protein (more than 1.0 g/day) of 3.346 (P = 0.0001), hypertension of 1.949 (P = 0.01), deteriorated renal function of 3.040 (P < 0.0001), no ACE inhibitor/angiotensin receptor blocker administration of 2.725 (P = 0.0004), and the T235 and C(-20) haplotype of 1.608 (P = 0.0322). Only in patients carrying at least one M235 and A(-20) haplotype did the administration of ACE inhibitors/angiotensin receptor blockers have no significant effect on the prognosis of renal function (Kaplan-Meier, log rank test, chi2 = 0.700; P = 0.4028), whereas it was significant in patients who had other haplotypes of AGT (chi2 = 11.805; P = 0.0006).

CONCLUSION

This study provides evidence that the M235T and A(-20)C genotype of AGT can influence the therapeutic efficacy of a RAS blockade on the renal survival in IgAN.

A(-20)C polymorphism of the angiotensinogen gene and progression of IgA nephropathy

BACKGROUND

The M235T polymorphism of the angiotensinogen gene (AGT) is associated with an increased risk of primary hypertension, which may then lead to progressive renal disease. Recent studies showed that nucleotide substitution in the 5' upstream core promoter region of AGT affects the basal transcription rate of the gene.

METHODS

To evaluate the role of AGT polymorphisms in the progression of IgA nephropathy (IgAN), we analyzed the association of A(-20)C and M235T polymorphisms with renal prognosis in histologically-proven IgAN patients using the Kaplan-Meier method and Cox proportional hazards regression model.

RESULTS

The incidence of hypertension during the course was associated with T235, but not with C(-20). The renal survival rate for 137 patients with creatinine clearance (C(Cr)) of 70 mL/min or greater at the time of renal biopsy, and follow-up time of two years or more was significantly lower in the patients with C(-20) (P = 0.008). The Cox proportional hazards regression model showed an increased hazard ratio (HR) for urinary protein (more than 2 g/day) of 28.3 (95% CI, 7.3 to 109.8; P < 0.001), hypertension at the time of renal biopsy of 4.6 (95% CI, 1.8 to 11.9; P = 0.002), and C(-20) of 3.6 (95% CI, 1.5 to 8.7; P = 0.004).

CONCLUSION

This work provides evidence that the C(-20) polymorphism of AGT, a subset of T235 alleles, is associated with progression of renal dysfunction in IgAN.

Body weight changes and the A-6G polymorphism of the angiotensinogen gene

BACKGROUND

The objective of the study was to analyze the relationship of polymorphisms of the angiotensinogen gene with changes in body weight during 3 y of antihypertensive treatment, in a group of young adults with essential hypertension.

METHODS

Essential hypertensives, less than 50 y old, never previously treated with antihypertensive drugs and in the absence of diabetes mellitus were included. After the initial evaluation, patients were treated using only non-pharmacological measures (n=29), beta-blockers (n=40) or angiotensin-converting enzyme inhibitors (n=66). Resting blood pressure, biochemical profile and body weight at the beginning and yearly were measured. The polymorphism A-6G of the angiotensinogen gene located in the promoter region was analyzed.

RESULTS

One-hundred and thirty-five patients were included. Genotypes of the A-6G polymorphism of the AGT gene were in Hardy-Weinberg equilibrium (AA 34, AG 63, GG 38). No significant differences were observed among genotypes in terms of age, body mass index, body weight, systolic or diastolic blood pressure. No significant differences in the genotype distribution or in the allele frequencies were observed, although the A allele was most frequent among the obese subjects. During the 3 y of antihypertensive treatment, there was a trend to increase weight despite the dietary recommendations. The slopes of body weight over time, adjusted by age and baseline BMI, differed significantly among the homozygote genotypes (P=0.006). The highest were for those with the AA genotype and the lowest for the GG genotype (1.180+/-0.25 and -0.128+/-0.24 kg/y; P=0.0001). The influence of the genotype in the changes on body weight remained significant after considering its interaction with the kind of antihypertensive treatment, although among subjects carrying the AA genotype those treated with ACEi showed the least body weight change. Furthermore, A-6G genotypes had the largest influence on weight changes, accounting for 19% of the variance, when age, sex and initial body mass index were included in the model.

CONCLUSIONS

In a group of young adult hypertensive subjects, there was a trend to increase weight despite dietary recommendations. Subjects with the AA genotype were those with the largest weight gain, but this effect was modified by the antihypertensive treatment.

[Renin-angiotensin system genetic polymorphisms and essential hypertension in the Spanish population]

BACKGROUND

The goal of this study was to analyse the association between essential hypertension and the main genetic polymorphisms at the renin-angiotensin system in the Spanish population.

PATIENTS AND METHOD

Case-control study including 185 essential hypertensive subjects(age [SD] 39.6 [7.5] years, 52% women, systolic blood pressure 151.2 [17.4] mmHg, diastolic blood pressure 96.0 [9.4] mmHg) and 350 sex- and age-matched normotensive individuals selected from a sample of the general population of the Comunidad Valenciana, Spain (age 39.4 [8.0] years, 51.7% women, systolic blood pressure 116.0 [12.0] mmHg, diastolic blood pressure 69.6 [8.5] mmHg). A PCR was performed to determine I/D angiotensin converting enzyme (ACE) gene polymorphism, A-6G and M235T angiotensinogen gene polymorphism and A1166C polymorphism of the angiotensin II type 1 receptor.

RESULTS

There were no differences between cases and controls with regard to genotypic and allelic distributions. In hypertensive patients,there were no differences in genotypic or allelic distributions after considering the presence or absence of a familial history of hypertension or comparing tertiles of systolic and diastolic blood pressure values. Only in women, the combination of a C allele of A1166C polymorphism with an A-6G angiotensinogen polymorphism A allele (p = 0.007), or an M235T angiotensinogen polymorphism T allele (p = 0.007), was associated with a higher risk of hypertension.

CONCLUSIONS

We found no association between essential hypertension risk and I/D ACE gene, M235T and A-6G angiotensinogen gene, or A1166C angiotensin II type 1 receptor gene polymorphisms. An epistatic effect was observed in young women between angiotensin II type 1 receptor polymorphisms and angiotensinogen polymorphisms.

Polymorphisms in the angiotensinogen gene are associated with carotid intimal-medial thickening in females from a community-based population

BACKGROUND

Polymorphisms within genes of the renin-angiotensin system have been associated with an increased risk of cardiovascular disease. We investigated the association of polymorphisms in the angiotensinogen (AGT) and angiotensin II receptor type 1 (AGTR1) genes with increased intima-media thickness (IMT) and the presence of plaques in carotid arteries.

METHODS

Subjects (1111) from the Perth Carotid Ultrasound Disease Assessment Study (CUDAS) were genotyped for three polymorphisms: two in the promoter of the AGT gene, G-6A and A-20C; and one in the AGTR1 gene, A1166C.

RESULTS

Using multivariate generalised linear models, the AGT-6A allele (P<0.001) and the AGT-20C allele (P<0.03) were significantly associated with increased mean carotid IMT in females but not in males when adjusted for conventional risk factors. The AGTR1 A1166C polymorphism did not show any significant relationship to mean IMT. Results suggest that the I allele of the angiotensin converting enzyme insertion/deletion polymorphism may interact with the AGT-6G allele to increase mean carotid IMT in the population as a whole. None of the polymorphisms investigated were significantly associated with the presence of carotid plaques.

CONCLUSION

This study shows that polymorphisms in the angiotensinogen gene are associated with an increased risk of carotid intimal-medial wall thickening in females.

Angiotensinogen in essential hypertension: from genetics to nephrology

There is general consensus that genetic variation accounts in part for individual susceptibilities to essential hypertension. In marked contrast to classic mendelian disorders, in which genetic alterations produce a gain or loss of function, genetic determinants of essential hypertension, high blood pressure of unknown cause, are expected to be small, achieving significance through the cumulative effects of environmental exposure over the course of a lifetime. Whether and how genetic factors that contribute to common diseases can be identified remain unclear. Research on a link between angiotensinogen and essential hypertension illustrates a path that began in genetics and is now leading toward nephrology. Various challenges encountered along the way may prove to be characteristic features of genetic investigations of the pathogenesis of common diseases. The implication of a gene by statistical analysis is only the beginning of a protracted process of functional analysis at increasing levels of biologic integration. The ultimate goal is to develop an understanding of the manner in which genetic variation at a locus can affect a physiologic parameter and to extract from this inference new knowledge of significance for the prevention or treatment of disease.

A-6G variant of the angiotensinogen gene and essential hypertension in Han, Tibetan, and Yi populations

To investigate the relationship between the A-6G variant in the promoter of the angiotensinogen gene and essential hypertension in Han, Tibetan, and Yi populations. All patients with essential hypertension were selected by WHO criteria. And the polymorphism of the A-6G variant was determined by PCR/RFLP. The data were analyzed by t test and chi2 test. There was no significant difference in the genotype or allele frequencies between normotensives and hypertensives in the Han, Tibetan, and Yi populations, respectively. However, when the subjects were divided into male and female subgroups, the genotype distributions among hypertensives and normotensives of the Tibetan female group were as follows: AA, 37% vs. 48%; AG, 52% vs. 48%; GG, 11% vs. 4%, respectively and the frequency of the G allele was significantly higher in hypertensives than in normotensives in the Tibetan female group (0.37 vs. 0.28, chi2=4.25, p<0.05). In addition, we observed that there was a significant difference between the Han and Tibetan normotensive groups in the distributions of the allele and genotype frequencies of the A-6G variant. The frequency of the G allele was 0.29 and 0.17 in the Tibetan normotensive and Han groups, respectively (p<0.001). The G allele of the A-6G variant was associated with hypertension in the Tibetan females, but not in the Yi or Han females. And we confirmed that there was a significant difference in the prevalence of the allele frequencies of the A-6G variant between the Han and Tibetan normotensive groups.

From genetics to mechanism of disease liability

The molecular basis of single-gene Mendelian disorders resulting from gain or loss of function is being clarified at a rapid pace. Progress in the genetics of common disease, by contrast, has been frustratingly limited, as we discuss by reference to essential hypertension (EH). The application of standard genetic paradigms to hypertension research has yielded remarkable findings. Arterial pressure (AP) variation in laboratory rats has been correlated with various genes. Likewise, rare Mendelian hypertension syndromes are increasingly understood in molecular terms. The implications of these findings for EH have proven to be modest, however. Genetic methods have been applied to investigate directly essential hypertension in humans, with mixed results. The power of such methods to identify genetic determinants of EH has been questioned. The issues confronting the genetic analysis of EH are discussed by drawing from our ongoing work along the hypothesis that molecular variants of the angiotensinogen gene may constitute inherited predispositions to the condition. Simply establishing correlation is already a daunting task. Far more challenging yet is to establish causation for a physiological phenotype, that is, to understand the mechanism by which a genetic factor may predispose to essential hypertension. Susceptibility imparted by genetic variation, modest and quantitative, modulates response to environmental exposure over time. The product of the gene under examination may be highly pleiotropic, being involved with multiple physiological processes in multiple tissues. Finally, as physiological phenotypes are defined at the level of the entire organism, ultimate demonstration of genetic determination may require specific genetic manipulations in entire organisms.

Genetic polymorphisms in the renin-angiotensin system: relevance for susceptibility to cardiovascular disease

The renin-angiotensin system plays an important role in the pathogenesis of cardiovascular disease. Cloning of the human genes coding for the angiotensin-converting enzyme, angiotensinogen, and angiotensin II type 1 receptor has led to the discovery of several polymorphisms, which may be implicated in the pathogenesis of cardiovascular disease. The deletion/insertion (D/I) polymorphism of the angiotensin-converting enzyme gene is associated with hypertension in men, left ventricular hypertrophy in untreated hypertensive patients, various atherosclerotic cardiovascular complications, and microvascular disorders. The M235T polymorphism of the angiotensinogen gene may be associated with a higher risk of hypertension. The A1166C polymorphism of the angiotensin II type 1 receptor gene is probably correlated with hypertension and through an epistatic interaction with the D/I polymorphism of the angiotensin-converting enzyme gene possibly also with coronary heart disease. Several other gene polymorphisms, in particular those in the promoter area of the angiotensinogen gene, have been studied in relation to cardiovascular disease. Based on the insights gained from the reports summarized in this review article, population-based genetic studies of nuclear families are currently being conducted in Belgium and in the People's Republic of China with blood pressure and hypertension as the main outcome variables.