Aldosterone synthase gene (CYP11B2) C-344T polymorphism in Caucasians from the Berlin Salt-Sensitivity Trial (BeSST)

Underestimated reactions and regulation patterns of adrenal cytochromes P450

Although cytochrome P450 (CYP) systems including the adrenal ones are being investigated since many years, there are still reactions and regulation patterns that have been underestimated ever since. This review discusses neglected ones to bring them into the focus of investigators working in the field. Novel substrates and reactions described for adrenal CYPs recently point to the fact that different from what has been believed for many years, adrenal CYPs are less selective than previously thought. The conversion of steroid sulfates, intermediates of steroid biosynthesis as well as of exogenous compounds are being discussed here in more detail and consequences for further studies are drawn. Furthermore, it was shown that protein-protein interactions may have an important effect not only on the activity of adrenal CYPs, but also on the product pattern of the reactions. It was found that, as expected, the stoichiometry of CYP:redox partner plays an important role for tuning the activity. In addition, competition between different CYPs for the redox partner and for electrons and possible alterations by mutants in the efficiency of electron transfer play an important role for the activity and product pattern. Moreover, the influence of phosphorylation and small charged molecules like natural polyamines on the activity of adrenal systems has been demonstrated in-vitro indicating a possible regulation of adrenal CYP reactions by affecting redox partner recognition and binding affinity. Finally, an effect of the genetic background on the consequences of mutations in adrenal CYPs found in patients was suggested from corresponding in-vitro studies indicating that a different genetic background might be able to significantly affect the activity of a CYP mutant.

CYP11B2 gene polymorphism and essential hypertension among Tibetan, Dongxiang and Han populations from northwest of China

Essential hypertension (EH) is a complex multifactorial condition influenced by both genetic and environmental factors; aldosterone synthase (CYP11B2) is a key enzyme which involves in the terminal steps of aldosterone synthesis. The result of relationship between C-344T of CYP11B2 polymorphism and EH was controversial. This study was undertaken to investigate the association of C-344T polymorphism with EH in the populations of Tibetan, Dongxiang and Han from northwest of China. A total of 2115 participants aged 18-70 years were enrolled in this study. In total, 1776 blood samples, including 545 Tibetan (305 hypertensive and 240 normotensive), 530 Dongxiang (254 hypertensive and 276 normotensive) and 701 Han (338 hypertensive and 363 normotensive), were analyzed successfully by using Snapshot minisequencing method, 30 samples were also performed by direct sequencing (5 hypertensive and 5 normotensive in each population, respectively). The frequencies of genotype and allele of CYP11B2 (C-344T) were not significantly different between EH group and control group in every ethnic population (p > 0.05). However, in female population of Tibetan, the frequencies of CC and CT genotype and C allele in EH group were higher than in control (p < 0.05) group. The frequencies of CC genotype and C allele in both the normotensive controls and EH patients in Tibetan population were higher than in Dongxiang and Han populations. Our study suggests that there is lack of association between C-344T polymorphism of CYP11B2 gene and EH in Dongxiang and Han populations, whereas the polymorphism was correlated with EH in female population of Tibetan.

Polymorphisms of three genes (ACE, AGT and CYP11B2) in the renin-angiotensin-aldosterone system are not associated with blood pressure salt sensitivity: A systematic meta-analysis

Many studies have suggested that polymorphisms of three key genes (ACE, AGT and CYP11B2) in the renin-angiotensin-aldosterone system (RAAS) play important roles in the development of blood pressure (BP) salt sensitivity, but they have revealed inconsistent results. Thus, we performed a meta-analysis to clarify the association. PubMed and Embase databases were searched for eligible published articles. Fixed- or random-effect models were used to pool odds ratios and 95% confidence intervals based on whether there was significant heterogeneity between studies. In total, seven studies [237 salt-sensitive (SS) cases and 251 salt-resistant (SR) controls] for ACE gene I/D polymorphism, three studies (130 SS cases and 221 SR controls) for AGT gene M235T polymorphism and three studies (113 SS cases and 218 SR controls) for CYP11B2 gene C344T polymorphism were included in this meta-analysis. The results showed that there was no significant association between polymorphisms of these three polymorphisms in the RAAS and BP salt sensitivity under three genetic models (all p > 0.05). The meta-analysis suggested that three polymorphisms (ACE gene I/D, AGT gene M235T, CYP11B2 gene C344T) in the RAAS have no significant effect on BP salt sensitivity.

Genomic epidemiology of blood pressure salt sensitivity

High blood pressure (BP) is a complex trait determined by genetic and environmental factors, as well as their interactions. Over the past few decades, there has been substantial progress elucidating the genetic determinants underlying BP response to sodium intake, or BP salt sensitivity. Research of monogenic BP disorders has highlighted the importance of renal salt handling in BP regulation, implicating genes and biological pathways subsequently identified in candidate gene studies of salt sensitivity. Despite these advancements, certain candidate gene findings await replication evidence, and some biological pathways warrant further investigation. Furthermore, results from genome-wide association studies (GWASs) and sequencing work have yet to be reported. GWAS will be valuable for uncovering novel mechanisms underlying salt sensitivity, whereas future sequencing efforts promise the discovery of functional variants related to this complex trait. Delineating the genetic architecture of salt sensitivity will be critical to understanding how genes and dietary sodium interact to influence BP.

Gene-sodium interaction and blood pressure: findings from genomics research of blood pressure salt sensitivity

High blood pressure (BP) is a complex trait determined by both genetic and environmental factors, as well as the interactions between these factors. Over the past few decades, there has been substantial progress in elucidating the genetic determinants underlying the BP response to sodium intake, or BP salt sensitivity. Research of monogenic BP disorders has highlighted the importance of renal salt handling in BP regulation, implicating genes and biological pathways related to salt sensitivity. Candidate gene studies have contributed important information toward understanding the genomic mechanisms underlying the BP response to salt intake, identifying genes in the renin-angiotensin-aldosterone system, renal sodium channels/transporters, and the endothelial system related to this phenotype. Despite these advancements, genome-wide association studies are still needed to uncover novel mechanisms underlying salt sensitivity, while future sequencing efforts promise the discovery of functional variants related to this complex trait. Delineating the genetic architecture of salt sensitivity will be critical to understanding how genes and dietary sodium interact to influence BP.

Relationship between -344T/C polymorphism in the aldosterone synthase gene and atrial fibrillation in patients with essential hypertension

INTRODUCTION

Aldosterone plays an important role in the pathogenesis of non-familial atrial fibrillation (AF). We tested the hypothesis that the -344T/C polymorphism in the aldosterone synthase gene may be associated with non-familial AF in Chinese patients with hypertension.

MATERIALS AND METHODS

We performed a 1:1 paired case-control study in 310 cases of hypertension with AF and same number matched controls. The -344T/C polymorphism was determined with polymerase chain reaction-restriction fragment length polymorphism.

RESULTS

The distribution of the CYP11B2 genotypes (TT, TC and CC) was 41.9%, 50.6%, and 7.4% in AF patients, which was not different from controls (48.4%, 44.5%, and 7.1%, χ(2) = 2.675, p = 0.263). The difference between the C allele (32.3% vs. 29.4%) was also not significant between two groups (χ(2) = 1.661, p = 0.197). Logistic regression analysis showed that LAD and LVEDD (both p < 0.001), rather than the C allele of the CYP11B2 gene (p= 0.107) were significant predictors for AF. The LAD of C allele carriers is significantly larger than that of non-C allele carriers (p = 0.009).

CONCLUSIONS

Our results indicate that the -344T/C polymorphism in the aldostrone synthase gene is not associated with AF but it might be associated with atrial remodelling in hypertensives.

Association of the -344C/T aldosterone synthase (CYP11B2) gene variant with hypertension and stroke

Stroke is a complex disease caused by combination of multiple risk factors. Recent findings have suggested that stroke has a significant genetic component. Various types of genetic polymorphisms have been suggested to contribute to the risk of stroke. Gene polymorphisms of renin-angiontensin aldosterone system (RAAS) have been suggested to be risk factors for hypertension, cardiovascular diseases and stroke. In the present case-control study we investigated the association of -344C/T (rs1799998) [corrected] polymorphism in the promoter region of the human aldosterone (CYP11B2) gene with genetic predisposition to hypertension, ischemic stroke and stroke subtypes classified according to TOAST (Trial of Org 10172 in Acute Stroke Treatment) classification. Four hundred and three stroke patients (hypertensives:normotensives=219:184) and three hundred and ninety four, sex and age matched healthy controls (hypertensives:normotensives=118:276) were involved in the study. The region of interest in the CYP11B2 gene was amplified by polymerase chain reaction and genotypes determined by subjecting the PCR products to restriction digestion by the enzyme HaeIII. Significant difference was observed in the genotypic distribution and allelic frequency between the stroke patients and healthy controls. TT genotype and T allele associated significantly with hypertension and stroke (p<0.000 in hypertension and p=0.000 in case of stroke). A stepwise logistic regression analysis confirmed these findings. To establish that this polymorphism is associated with stroke independent of hypertension, we compared stroke patients without hypertension with normotensive controls. Significant difference was observed in genotypic distribution and allelic frequency between the two groups (p=0.000). Further evaluating the association of this polymorphism with stroke subtypes we found significant associations with intracranial large artery atherosclerosis, lacunar stroke and cardioembolic stroke (p=0.000 in each case). In conclusion our study suggests that -344T allele of CYP11B2 gene is an important risk factor for hypertension and ischemic stroke. However, this is a preliminary study and the results need to be confirmed in a larger cohort.

Associations of the -344 T>C and the 3097 G>A polymorphisms of CYP11B2 gene with hypertension, type 2 diabetes, and metabolic syndrome in a French population

BACKGROUND

Aldosterone can affect both blood pressure (BP) and glucose metabolism. We assessed the association of two polymorphisms -344 T>C and the 3097 G>A in the aldosterone synthase gene (CYP11B2) with prevalent and incident hypertension (HT), type 2 diabetes (T2D), and the metabolic syndrome (MetS).

METHODS

We studied the 5,212 participants to D.E.S.I.R. (Data from Epidemiologic Study on the Insulin Resistance syndrome), a cohort from French general population. Genotyping was done by a TaqMan assay. Analysis of covariance, multivariate logistic regression (adjusted for age, MetS components) and haplotype analysis were performed.

RESULTS

The prevalences and 9-year incidences were 16.7 and 36.1% for HT, 2.6 and 6.2% for T2D, and 19.3 and 25.1% for the MetS. Risk for incident HT was reduced with the AA genotype of 3097 G>A, adjusted odds ratios (OR): 0.67; p = 0.04. The prevalence of HT was lower in women carrying the C allele of -344 T>C, OR 0.75; p = 0.03 for the TC genotype and 0.69; p = 0.03 for the CC genotype. In men, incident T2D was associated with both polymorphisms, adjusted OR for -344 T>C: 1.63; p = 0.04 for TC genotype and 2.12; p = 0.008 for CC genotype; for the 3097 G>A: the AA genotype was associated with a lower risk, OR 0.23; p = 0.02. In men, incident MetS was associated with 3097 G>A, OR: 0.57; p = 0.02 for AA genotype. Significant associations between haplotype combinations and the prevalence or incidence of the three diseases were also found.

CONCLUSION

The -344 T>C and 3097 G>A polymorphisms in the CYP11B2 are associated with T2D, hypertension and the MetS in European subjects with gender variations.

A systemic review of the relationship between aldosterone synthase - 344 C/T polymorphism and hypertension in Han

Many studies reported the association between aldosterone synthase gene CYP11B2 polymorphism and essential hypertension in Chinese. So far, no meta- analysis was conducted between the etiology of essential hypertension and CYP11B2 -344 C/T polymorphism in Han Chinese, the majority (93% of the total population) in China. Recruited literature was based on searching the Cochrane Library, MEDLINE, EMBASE, the Chinese Biomedicine Database (CBM), CNKI, VIP, and reference lists of articles without language restrictions. Nine studies with case-control involving 4259 unselected essential hypertension patients and 3213 controls were included in the analysis. From the nine homogeneous studies with gender, age, and ethnicity matched controls, we found no significant association between the etiology of essential hypertension and the -344 C/T variant in Han Chinese with random effect models (for homozygous CC: odds ratio (OR), 1.04, 95% confidence interval (CI), 0.791.37, P = 0.79; for allele C: OR, 1.04, 95% CI, 0.921.18, P = 0.56). No significant association was observed between CYP11B2 -344 C/T polymorphism and hypertension susceptibility in both sexes. Current large sample analysis did not support the association between the etiology of essential hypertension and CYP11B2 - 344 C/T polymorphism in Han Chinese.

Identification of polymorphisms in the human 11beta-hydroxysteroid dehydrogenase type 2 gene promoter: functional characterization and relevance for salt sensitivity

Reduced activity of 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2) plays a role in essential hypertension and the sensitivity of blood pressure to dietary salt. Nonconservative mutations in the coding region are extremely rare and do not explain the variable 11beta-HSD2 activity. We focused therefore on the 5'-regulatory region and identified and characterized the first promoter polymorphisms. Transfections of variants G-209A and G-126A into SW620 cells reduced promoter activity and affinity for activators nuclear factor 1 (NF1) and Sp1. Chromatin immunoprecipitation revealed Sp1, NF1, and glucocorticoid receptor (GR) binding to the HSD11B2 promoter. Dexamethasone induced expression of mRNA and activity of HSD11B2. GR and/or NF1 overexpression increased endogenous HSD11B2 mRNA and activity. GR complexes cooperated with NF1 to activate HSD11B2, an effect diminished in the presence of the G-209A variant. When compared to salt-resistant subjects (96), salt-sensitive volunteers (54) more frequently had the G-209A variant, higher occurrence of alleles A4/A7 of polymorphic microsatellite marker, and higher urinary ratios of cortisol to cortisone metabolites. First, we conclude that the mechanism of glucocorticoid-induced HSD11B2 expression is mainly mediated by cooperation between GR and NF1 on the HSD11B2 promoter and, second, that the newly identified promoter variants reduce activity and cooperation of cognate transcription factors, resulting in diminished HSD11B2 transcription, an effect favoring salt sensitivity.

Association of the C−344T aldosterone synthase gene variant with essential hypertension: a meta-analysis

BACKGROUND

The CYP11B2 gene (CYP11B2) encoding aldosterone synthase has been associated with essential hypertension and some, but not all, studies have reported that the C-344T variant may influence the risk of the disease.

OBJECTIVE

We performed a systematic review of the literature by means of a meta-analysis to evaluate the influence of the C-344T CYP11B2 polymorphism on arterial hypertension and intermediate phenotypes.

METHODS

From 485 reports, we included 42 observational studies, case-control and cohort at baseline. Fixed and random effect models were used to pool data from individual studies.

RESULTS

From 19 heterogeneous studies including 5343 essential hypertensive and 5882 control subjects, we found a significant association between hypertension and the C-344T variant in fixed but not in random effect models [for homozygous CC: odds ratio (OR), 0.834; 95% confidence interval (CI), 0.760-0.914; P < 0.0001, n = 11 225]. Besides, homozygous CC subjects had lower plasma renin activity (D, -0.161; 95% CI, -0.279 to -0.043; P < 0.01, n = 1428) but no difference in plasma aldosterone levels (D, -0.006; 95% CI, -0.081 to 0.07; P = 0.88, n = 2872). Limiting the quantitative analysis of blood pressure to 13 studies including only untreated individuals, no significant association was found for systolic arterial blood pressure (D, 0.042; 95% CI, -0.057 to 0.141; P = 0.41, n = 1775) and diastolic arterial blood pressure (D, 0.026; 95% CI, -0.073 to 0.125; P = 0.61, n = 1775).

CONCLUSION

Homozygous individuals for the -344C CYP11B2 allele are at 17% lower risk of hypertension with respect to homozygous TT subjects.

Aldosterone Synthase Gene T-344C Polymorphism, Sodium and Blood Pressure in a Free-Living Population: A Community-Based Study

There have been few epidemiological studies on the gene-environmental interaction between the aldosterone synthase gene (CYP11B2) T-344C polymorphism and sodium in relation to blood pressure in a free-living general population. We hypothesized a priori that persons with the T allele of CYP11B2 would have elevated blood pressure levels in response to a higher sodium intake, and thus the association between the T-344C polymorphism and blood pressure would be more evident among persons with a high sodium intake than among those with a low sodium intake. Study subjects were 2,823 men and women aged 30-74 in a Japanese community. We examined the associations between the T-344C polymorphism and blood pressure levels, stratified by sodium variables estimated by 24-h urinary sodium excretion and a dietary questionnaire. There was no significant difference in blood pressure levels among the CC, TC and TT groups for either or both sexes. However, among persons with higher sodium excretion, mean systolic blood pressure levels tended to be higher in those with the TC (+3.0 mmHg, p=0.06) and TT (+2.9 mmHg, p=0.07) genotypes than in those with the CC genotype, but this tendency was not seen among those with lower sodium excretion (-4.0 mmHg, p=0.03 for TC vs. CC; -3.0 mmHg, p=0.11 for TT vs. CC; p for interaction =0.006). In conclusion, we found no association between CYP11B2 and blood pressure for total subjects or for persons with a higher sodium intake. However, a possible gene-blood pressure association among persons with higher sodium intake needs to be explored further.

C-344T polymorphism of the aldosterone synthase gene and blood pressure in the elderly: a population-based study

OBJECTIVES

Whether the C-344T polymorphism of the aldosterone synthase gene is important for blood pressure control remains controversial. It has been proposed that an association between this polymorphism and blood pressure might be evident in elderly subjects. The aim of the present study was to test this hypothesis in an epidemiological context.

DESIGN

A cross-sectional epidemiological evaluation of a highly homogeneous unselected general population of elderly Caucasians.

METHODS

Lifestyle, medical history, anthropometrics, skinfold thickness, supine blood pressure, heart rate and biochemical measures were recorded in 437 subjects aged > or = 65 years living in a secluded valley. All were genotyped for C-344T allele status and underwent measurements of plasma aldosterone and renin.

RESULTS

The C-344T genotypic frequency did not deviate from Hardy-Weinberg equilibrium. The aldosterone to renin ratio was 19% lower in the CC than in the TT genotype. Systolic blood pressure was significantly lower in subjects with the CC genotype, higher in the TT (+9.6 mmHg versus CC) and intermediate in the CT (+7.9 mmHg versus CC). Adjustment for age, gender, smoking and antihypertensive treatment did not affect this association. Diastolic blood pressure did not differ across genotypes. A significant increase of systolic blood pressure with increasing age and with increasing skinfold thickness was observed in the TT homozygotes but not in the C-carriers.

CONCLUSIONS

These data support the concept that the C-344T polymorphism plays a role in controlling systolic blood pressure and the age-related increase in systolic blood pressure in response to age and to body fat, possibly through differences in modulation of aldosterone synthesis.

Pharmacogenomics of blood pressure response to antihypertensive treatment

PURPOSE IDENTIFICATION: Inter-individual variability in blood pressure response to treatment is well documented, but a clinically useful means to distinguish responders from non-responders has been elusive. With the advent of new technologies and genomic knowledge, more investigators are seeking to identify genetic determinants of blood pressure response to therapy.

STUDY SELECTION

We identified studies of candidate polymorphisms from an initial PubMed search using the MESH terms 'Hypertension: Drug Therapy' and 'Genetics' or 'Pharmacogenetics', limiting results to English-language publications on studies in human adults. We further identified specific polymorphisms of interest noted in earlier reviews and performed additional PubMed searches based on these candidate genes. Pertinent studies were further extracted from the references of studies already identified. We focused on clinical trials that measured blood pressure response to a medication or class of medications over a minimum of 4 weeks.

DATA EXTRACTION

We evaluated studies looking at blood pressure response to commonly used classes of antihypertensive medications by major genetic variants. RESULTS OF ANALYSIS: Although many studies show that blood pressure response to a given class of antihypertensive medications varies by genotype for different polymorphisms, none of the genotypes identified consistently predicted blood pressure response.

CONCLUSIONS

Common variants may influence response to diuretics, beta-blockers, angiotensin-converting enzyme inhibitors, and angiotensin receptor blockers, but studies of polymorphisms have generally yielded conflicting results. The inclusion of pharmacogenomic studies in large clinical trials and other more innovative investigative methods may provide greater clarity of the potential role for genotyping in the treatment of patients with hypertension.

Correlation between left ventricular mass and urinary sodium excretion in specific genotypes of CYP11B2

BACKGROUND

Aldosterone has essential roles in regulating intravascular volume and blood pressure, and is suggested to influence cardiac structure. However, the association of polymorphisms in the aldosterone synthase gene (CYP11B2) with hypertension or cardiac hypertrophy remains controversial.

OBJECTIVE

To evaluate the distribution of polymorphisms in the CYP11B2 gene and the possible associations between genotypes and blood pressure, urinary excretion of aldosterone or electrolytes and echocardiographic measurements, in a Japanese population.

METHODS AND RESULTS

We examined the association of two common diallelic polymorphisms within CYP11B2, one in the promoter -344T/C and the other an intron 2 gene conversion, with blood pressure, 24-h urinary excretion of aldosterone and electrolytes, and echocardiographic measurements, in a Japanese population. We confirmed significant linkage disequilibrium between these polymorphic loci and ethnic differences in frequency of the alleles. The -344C and -344T haplotypes apparently diverged before the intron conversion polymorphism was generated on the latter haplotype. Allele frequencies did not differ between 535 normotensive and 360 hypertensive individuals or between hypertensive individuals with higher and lower concentrations of renin. The only significant correlation was a positive correlation of left ventricular mass with 24-h urinary excretion of sodium, which occurred only in individuals with the -344CC genotype or the intron 2 conversion (-/-) genotype.

CONCLUSIONS

The -344CC or intron 2 conversion (-/-) genotype in CYP11B2 may be a risk factor for developing sodium-sensitive cardiac hypertrophy. Ethnic differences in the distribution of CYP11B2 genotypes combined with differences in salt intake might account for inconsistencies between previous reports.

Genetics of human hypertension

Hypertension is a complex genetic disorder caused by interplay between several "risk" genes and environmental factors (genetic heritability approximately 30%). Most genetic studies of hypertension use a candidate gene approach and two conclusions have been made: there is no association or linkage with the genes studied, or the hypertension phenotype is heterogeneous and subgroups with hypertension related to certain polymorphisms cannot be identified because of background noise. Studies using intermediate phenotypes suggest the latter is most likely. Another problem is the reliability of gene structure assessment: usually only one or two gene polymorphisms are assessed. The use of intermediate phenotypes and dense mapping of candidate genes would provide a better approach for identifying genotype-phenotype correlations, which might enable the use of genotypes to identify more-specific therapeutic and preventative measures for hypertensives.

Genetic predisposition to salt-sensitivity: a systematic review

PURPOSE

To assess the role of genetic polymorphisms in salt sensitivity of blood pressure.

DATA IDENTIFICATION

We conducted a systematic review by searching the Medline literature from March 1993 to June 2003. Each paper was scrutinized and data concerning study population, method of salt sensitivity testing, blood pressure measurement, definition of salt sensitivity, and effects were extracted.

STUDY SELECTION AND DATA EXTRACTION

A total of 23 studies met the inclusion criteria. There was considerable heterogeneity in the method of salt sensitivity testing among the studies. Due to these differences, it was impossible to perform pooled analyses by genetic variants. Detailed investigation was done on the alpha-adducin Gly460Trp, ACE I/D, angiotensinogen M235T, G protein beta 3 C825T, aldosterone synthase gene and 11 beta-hydroxysteroid dehydrogenase type 2 G534A polymorphism.

RESULTS AND CONCLUSIONS

Our analysis shows that the 460Trp variant of the alpha-adducin polymorphism is probably associated with a sodium-sensitive form of hypertension, while the polymorphisms of the angiotensin II type 1 receptor gene and the -344C/T variant of the aldosterone synthase gene are not associated with this phenotype. In view of the lack of standardization in salt sensitivity testing, we propose uniformity in study design in these type of studies.

Association of peripheral and central arterial wave reflections with the CYP11B2 ???344C allele and sodium excretion

OBJECTIVE

Angiotensin II and aldosterone, generated by the angiotensin-converting enzyme (ACE) and aldosterone synthase (CYP11B2), respectively, not only regulate sodium and water homeostasis, but also influence vascular remodeling in response to high blood pressure. In the European Project on Genes in Hypertension (EPOGH), we therefore investigated whether the ACE I/D and CYP11B2 C-344T polymorphisms influence early arterial wave reflections, a measure of vascular stiffness.

METHODS

We measured the peripheral and central augmentation index of systolic blood pressure by applanation tonometry at the level of the radial artery in 622 subjects (160 families and 64 unrelated individuals) randomly recruited from three European populations, whose average urinary sodium excretion ranged from 196 to 245 mmol/day. In multivariate analyses, with sodium excretion analyzed as a continuous variable, we explored the phenotype-genotype associations by means of generalized estimating equations and the quantitative transmission disequilibrium test.

RESULTS

The peripheral and central augmentation indexes were significantly higher in CYP11B2 -344C allele carriers than in -344T homozygotes. In offspring, early wave reflections increased with the transmission of the -344C allele. This effect of the CYP11B2 polymorphism occurred in subjects with a higher than median urinary sodium excretion (210 mmol/day). The ACE I/D polymorphism did not influence augmentation of systolic blood pressure.

CONCLUSIONS

The CYP11B2 C-344T polymorphism affects arterial stiffness. However, sodium intake seems to modulate this genetic effect.

Racial and Ethnic Differences in Microalbuminuria Prevalence in a Diabetes Population: The Pathways Study

The objective of this study was to determine whether racial or ethnic differences in prevalence of diabetic microalbuminuria were observed in a large primary care population in which comparable access to health care exists. A cross-sectional analysis of survey and automated laboratory data 2969 primary care diabetic patients of a large regional health maintenance organization was conducted. Study data were analyzed for racial/ethnic differences in microalbuminuria (30 to 300 mg albumin/g creatinine) and macroalbuminuria (>300 mg albumin/g creatinine) prevalence among diabetes registry-identified patients who completed a survey that assessed demographics, diabetes care, and depression. Computerized pharmacy, hospital, and laboratory data were linked to survey data for analysis. Racial/ethnic differences in the odds of microalbuminuria and macroalbuminuria were assessed by unconditional logistic regression, stratified by the presence of hypertension. Among those tested, the unadjusted prevalence of micro- or macroalbuminuria was 30.9%, which was similar among the various racial/ethnic groups. Among those without hypertension, microalbuminuria was twofold greater (odds ratio [OR] 2.01; 95% confidence interval [CI] 1.14 to 3.53) and macroalbuminuria was threefold greater (OR 3.17; 95% CI 1.09 to 9.26) for Asians as compared with whites. Among those with hypertension, adjusted odds of microalbuminuria were greater for Hispanics (OR 3.82; 95% CI 1.16 to 12.57) than whites, whereas adjusted odds of macroalbuminuria were threefold greater for blacks (OR 3.32; 95% CI 1.26 to 8.76) than for whites. For most racial/ethnic minorities, hypertriglyceridemia was significantly associated with greater odds of micro- and macroalbuminuria. Among a large primary care population, racial/ethnic differences exist in the adjusted prevalence of microalbuminuria and macroalbuminuria depending on hypertension status. In this setting, racial/ethnic differences in early diabetic nephropathy were observed despite comparable access to diabetes care.

Aldosterone synthase gene (CYP11B2) C-344T polymorphism, plasma aldosterone, renin activity and blood pressure in a multi-ethnic population

BACKGROUND

The aldosterone synthase gene (CYP1B2) locus is a candidate region involved in the development of hypertension.

OBJECTIVE

To study the relationship between the C-344T CYP1B2 polymorphism, plasma aldosterone, renin activity and blood pressure in a multi-ethnic population.

DESIGN

Population-based, cross-sectional study of 1313 middle-aged men and women (456 white, 441 of African origin and 416 South Asian). Anthropometry, blood pressure, biochemistry, questionnaire data and timed urine collections were taken with standardized techniques. All were genotyped for the C-344T CYP11B2 polymorphism.

RESULTS

The frequency of the C allele was significantly lower in people of African origin (0.21) than in white (0.46) and South Asian (0.43) (P < 0.001). After adjustment for age, sex and ethnicity the TT genotype was associated with 14% higher plasma aldosterone levels, 3.7 mmHg higher systolic and 2.1 mmHg higher diastolic blood pressure than CC (P for linear trend < 0.05). No significant interactions with age, sex, ethnicity, body mass index (BMI) and fractional excretion of sodium were found in the associations between genotype and both blood pressure and aldosterone levels. In a sub-sample of participants in which plasma renin activity was measured (n = 457), a significant excess of T alleles was found in those with a raised (>/= 750) aldosterone-to-renin ratio (ARR).

CONCLUSION

In this multi-ethnic population, the C-344T CYP1B2 polymorphism is associated with blood pressure, plasma aldosterone levels and ARR. Although significant differences in allele frequencies were found between groups, ethnicity does not explain the results.

Association between aldosterone synthase (CYP11B2) polymorphism and left ventricular mass in human essential hypertension

OBJECTIVES

The aim of our study was to evaluate the relationship between aldosterone synthase gene polymorphism and cardiac dimensions in essential hypertension.

BACKGROUND

Higher aldosterone synthase messenger ribonucleic acid levels in the human heart are accompanied by increased intracardiac aldosterone production, a phenomenon that is associated with cardiac fibrosis and hypertrophy. Recent evidence suggests that a polymorphism (-344C/T) in the promoter region of the aldosterone synthase gene is associated with increased constitutive aldosterone production.

METHOD

Relationships between M-mode echocardiographic cardiac dimensions and aldosterone synthase -344C/T polymorphism were studied in 210 never-treated, middle-aged patients (age 41.6 +/- 1.4 years) affected by mild to moderate essential hypertension. Among these patients, 48 had the genotype -C344C, 97 had -C344T, and 65 had -T344T. Patients in the three groups were similar in terms of age, gender, body mass index, and blood pressure.

RESULTS

Left ventricular (LV) mass and thickness were positively correlated with the number of T alleles: LV mass (CC, CT, and TT, respectively: 168 +/- 6.9, 179 +/- 5.2, and 193 +/- 6.9 g; p = 0.03), LV septal thickness (0.99 +/- 0.02, 1.03 +/- 0.02, and 11.08 +/- 0.03 cm, p = 0.04), PWT (0.93 +/- 0.03, 0.95 +/- 0.01, and 1.03 +/- 0.02 cm; p = 0.002), and relative wall thickness (38.3 +/- 1.2%, 38.8 +/- 0.8%, and 42.8 +/- 1.1%; p = 0.004). This trend was confirmed by linear regression, suggesting a "major gene" behavior for the T allele. Multiple regression analysis showed that this effect was independent of anthropometric and clinical factors, including adrenal aldosterone.

CONCLUSIONS

Our data suggest that -344C/T polymorphism affects LV mass and thickness in essential hypertension, independent of adrenal aldosterone. A role for intracardiac aldosterone synthesis is hypothesized.

CYP11B2 Polymorphisms and Home Blood Pressure in a Population-Based Cohort in Japanese: the Ohasama Study

Genetic polymorphisms of the aldosterone synthase gene (CYP11B2) have been major targets of studies into the genetic factors involved in hypertension. We have identified three genetic variants of CYP11B2, -344C/T at the promoter region, a conversion in intron 2 from the CYP11B2 sequence to the CYP11B1 sequence, and R173K in exon 3, in the Japanese population. -344C/T and R173K were in complete linkage disequilibrium in CYP11B2, and -344C/T was in strong, but not complete, linkage disequilibrium with the polymorphism in intron 2. Thus, two genetic polymorphisms, -344C/T and the gene conversion in intron 2, were investigated in association with home blood pressure (BP) values and clinical parameters in 1,242 subjects aged 40 and over in Ohasama, a rural Japanese community. Hypertension was defined as being treated with antihypertensive medication and/or having home BP values of more than 135 mmHg in systole and/or 85 mmHg in diastole. The results demonstrated that the -344T allele was significantly associated with increased prevalence of hypertension (p=0.015 in multiple logistic regression analysis, adjusted by age, gender, BMI, and smoking status), though BP level was unaltered. This allele was also significantly related to the prevalence of cardiovascular diseases in the older population (60 < or = age, p=0.014). The resting polymorphism, a gene conversion in CYP11B2 intron 2, was not associated with any clinical parameters. Therefore, -344C/T polymorphism in CYP11B2 was considered an independent genetic factor possibly associated with hypertension or atherosclerotic diseases in the Japanese population.

RAAS escape: a real clinical entity that may be important in the progression of cardiovascular and renal disease

Interruption of the renin-angiotensin-aldosterone system (RAAS) at different levels is target-organ protective in several disease states; however, complete blockade is unlikely to be achieved due to escape mechanisms whenever blockade is attempted, incomplete knowledge of the role of all elements of the RAAS, and lack of pharmacotherapy against some elements that have been shown to contribute to disease states. Aldosterone has been overlooked as a mediator of RAAS escape and a key factor in target-organ injury despite the use of available RAAS blockers. Aldosterone is thought to play a role in the development of hypertension, alteration in vascular structure, vascular smooth muscle hypertrophy, endothelial dysfunction, structural renal injury, proteinuria, left ventricular remodeling, collagen synthesis, and myocardial fibrosis. Aldosterone receptor antagonists have been shown to antagonize all these effects in experimental models. Clinical trials with aldosterone antagonists showed an improvement in survival and left ventricular mass index in patients with congestive heart failure, and a reduction in urinary protein excretion and left ventricular mass index in patients with type 2 diabetes and early nephropathy who developed aldosterone synthesis escape. Consequently, aldosterone receptor antagonists may have specific benefits for reducing target-organ injury, particularly if there is evidence of RAAS escape.

Haplotype analysis of aldosterone synthase gene (CYP11B2) polymorphisms shows association with essential hypertension

OBJECTIVE

The CYP11B2 locus is an important candidate region in essential hypertension (HT). We therefore investigated CYP11B2 polymorphisms T-344C, T4986C and A6547G for association with essential HT. This included haplotype analysis and measurement of plasma aldosterone levels.

METHODS

The three single nucleotide polymorphisms were genotyped by polymerase chain reaction-restriction fragment length polymorphism analysis of genomic DNA from 146 HT and 291 normotensive (NT) white subjects of Anglo-Celtic descent, in whom parental blood pressure status was the same as the subjects'. Genotype and allele frequencies in HTs and NTs were compared by chi2 analysis. Linkage disequilibrium and haplotype frequencies were estimated by the program 'snphap'. Phenotype-genotype relationships were tested using one-way analysis of variance.

RESULTS

The T-344C variant was associated with HT (chi2 = 7.4, P = 0.0064). This association was confined to female HTs (P = 0.0061 for genotypes, P = 0.0013 for alleles). A strong association with HT was also seen for the A6547G variant (P = 0.0015), being greatest in females (P < 0.0001). No association was seen for the T4986C variant. Haplotype analysis of the three single nucleotide polymorphisms across eight different haplotype combinations showed a significant association with HT (chi2 = 24, seven degrees of freedom, P < 0.001). No significant tracking of plasma aldosterone with genotype was observed.

CONCLUSION

The T-344C and A6547G, but not the T4986C, variants of the aldosterone synthase gene are associated with HT in females of the Anglo-Celtic population studied. This was reinforced by haplotype analysis.

Renin-angiotensin-aldosterone system and G-protein beta-3 subunit gene polymorphisms in salt-sensitive essential hypertension

Approximately 50% of hypertensive patients are salt sensitive (they increase their Blood Pressure in response to sodium intake or volume expansion). Mechanisms underlying salt sensitivity are not completely elucidated although there is evidence that they may be genetically determined. The aim of this study is to establish the relation among some genetic polymorphisms of the renin-angiotensin system (RAAS) and the beta-3 subunit of the protein G and salt sensitivity. We studied 102 essential hypertensive patients, stage 1-2 and without target organ damage. Salt sensitivity was assessed by the rapid protocol of Weinberger. We determined by polymerase Chain reaction techniques the following polymorphisms: insertion/deletion (I/D) of the angiotensin-converting enzyme (ACE), A1166C of the angiotensin II type 1 receptor (AT1R), -344C/T and intron 2 conversion (IC) of the aldosterone synthase (CYP11B2), and C825T of the beta-3 subunit of the protein G (GNB3). 41 patients (40.19%) were salt sensitive. The distribution of the different polymorphisms was similar in both groups of patients, but subjects carriers of the W allele of the CYP11B2 IC polymorphism had a greater risk for salt sensitivity as compared with no carriers (37 of 41, 90.2% vs 4 of 41, 9.8%, OR 3.02, P<0.05). Although there is no association between salt sensitivity and the different studied genotypes of the RAAS and of the GNB3, our data show a greater risk for salt sensitivity among carriers of the W allele of the CYP11B2 1C polymorphism.

Genotyping of Essential Hypertension Single-Nucleotide Polymorphisms by a Homogeneous PCR Method with Universal Energy Transfer Primers

Background: Human hypertension is a complex, multifactorial disease with a heritability of more than 30–50%. A genetic screening test based on analysis of multiple single-nucleotide polymorphisms (SNPs) to assess the likelihood of developing hypertension would be helpful for disease management.

Methods: Tailed allele-specific primers were designed to amplify by PCR six biallelic SNP loci [three in G protein-coupled receptor kinase type 4 (GRK4): R65L, A142V, and A486V; two in angiotensinogen: −6G→A and M235T; and one in aldosterone synthase: −344C→T] associated with essential hypertension. PCRs of SNP loci were coupled (via a common sequence of 21 nucleotide tails) to incorporate Universal Amplifluor™ primers labeled with fluorescein or sulforhodamine in a homogeneous format. Use of Amplifluors in SNP PCRs produced labeled amplicons, the fluorescence of which was quantified by a microplate reader and then analyzed via an Excel macro to provide genotypes for all six SNP loci. Unique restriction endonucleases were identified for five SNP loci that could independently confirm homogeneous PCR results when needed.

Results: We developed six homogeneous PCR assays that were set up, performed, and fluorometrically analyzed in 96-well microplates. Allele frequencies were determined for six SNPs in 60 Italian hypertensive patients and a control group of 60 normotensive persons. A significant correlation (P = 0.034) between one SNP [GRK4 (A486V)] and the hypertensive patients was observed. Genotyping results for five of six SNPs were confirmed by digesting corresponding amplicons with locus-specific restriction endonucleases.

Conclusions: We developed a simple and homogeneous fluorescent protocol that has been used to determine the SNP genotype for six loci in a population of hypertensive and normotensive persons. We also observed a significant association (P = 0.034) between one SNP (A486V) and an Italian population of mildly hypertensive patients.

Positive association of CYP11B2 gene polymorphism with genetic predisposition to essential hypertension

Predispositions to essential hypertension and cardiovascular diseases are possibly associated with gene polymorphisms of the renin-angiotensin system. Gene polymorphisms of angiotensinogen and angiotensin-converting enzyme genes have been suggested to be risk factors for hypertension and myocardial infarction. Concerning the polymorphism of aldosterone synthase (CYP11B2) gene, earlier studies have shown inconsistent results in terms of its relation to hypertension. In the present case-control study, we investigated the association of -344T/C polymorphism in the promoter region of human CYP11B2 gene with genetic predisposition to hypertension. The genotype of -344T/C polymorphism was determined in essential hypertension subjects (n=250) and normotensive subjects (n=221). The distributions of three genotypes (TT, TC, and CC) were significantly different between the hypertensive and the normotensive groups (chi(2)=9.61, P=0.008). Namely, the frequency of C allele was higher in the hypertensive patients than in the normotensive subjects (34.2 vs 26.5%, P=0.010). Our data suggest that the -344C allele of CYP11B2 gene polymorphism is associated with the genetic predisposition to develop essential hypertension.

Interaction between the C(-344)T polymorphism of CYP11B2 and age in the regulation of blood pressure and plasma aldosterone levels: cross-sectional and longitudinal findings of the Olivetti Prospective Heart Study

OBJECTIVE

To study the interaction between the C(-344)T polymorphism and known determinants (age, body mass and dietary sodium) of blood pressure and plasma aldosterone.

DESIGN

Cross-sectional and longitudinal (1980-1995) survey of male workers in southern Italy.

SETTING

Medical centre of the Olivetti factories.

PARTICIPANTS

In 1995, the C(-344)T polymorphism was characterized in 811 untreated men. A subgroup of 280 participants already seen in 1980 was the object of longitudinal analysis.

MAIN OUTCOME MEASURES

Blood pressure, demographic, anthropometric and biochemical variables (serum and urinary electrolytes and plasma aldosterone) and frequency of the C(-344)T polymorphism.

RESULTS

In the whole population, there was no difference among genotypes for any of the variables examined. However, multiple regression showed a significant interaction between age (but not body mass or sodium intake) and genotype with regard to systolic (P = 0.03) and diastolic ( P= 0.02) pressure variability independently of covariates. Diastolic pressure increased linearly with age in carriers of the T allele (TT, P<0.001 and TC, P= 0.005), but not in CC homozygotes ( P= 0.848). In T carriers - but not in CC homozygotes - blood pressure and serum potassium increased and plasma aldosterone and serum sodium decreased across quintiles of age (P< 0.001 for all trends). In the longitudinal study, diastolic pressure increased significantly over time only in T carriers (TC+TT: +2.6 +/- 0.6, versus CC: -0.4 +/- 1.5 mmHg, P= 0.04).

CONCLUSION

Inter-individual variation of blood pressure and plasma aldosterone is affected by the interaction of C(-344)T polymorphism and ageing, thus supporting a role for this variant in mechanisms affecting blood pressure regulation.

Aldosterone synthase gene (CYP11B2) C-334T polymorphism, ambulatory blood pressure and nocturnal decline in blood pressure in the general Japanese population: the Ohasama Study

OBJECTIVE

The C-344T polymorphism in the 5'-flanking region of the aldosterone synthase (CYP11B2) gene has been suggested to be associated with hypertension and disturbed circadian blood pressure (BP) rhythm through its effect on aldosterone synthesis. However, previous findings on this topic have been inconsistent.

DESIGN

A cross-sectional study.

SUBJECTS AND METHODS

We investigated the CYP11B2 C-344T genotype in 802 subjects, aged 40 and over, in a Japanese community, who gave written informed consent and were monitored for 24 h ambulatory BP.

RESULTS

The frequencies of the CC, CT, and TT genotypes in these Japanese subjects were 0.14, 0.44, and 0.42, showing a higher frequency of the T allele (0.64) than in Caucasians. Although there was no significant difference in 24 h ambulatory BP levels among the genotypes, the nocturnal decline in BP was significantly greater in the CC homozygous subjects than in other subjects (P = 0.0065 for systolic and P = 0.031 for diastolic decline in nocturnal BP). Detailed analyses demonstrated that this association was significant only in aged (60 years and over) or male subjects. The prevalence of previous cardiovascular disease was significantly less in these subjects with the CC genotype than in those with the TC and TT genotypes, although age, body mass index, male gender, smoking, use of alcohol and antihypertensive medication did not differ among the three genotypes. There was no significant difference among the three genotypes in biochemical and hormonal parameters.

CONCLUSION

Although the C-344 T polymorphism of CYP11B2 did not directly influence the level of 24 h BP, the CC genotype was associated with decreased nocturnal BP in elderly or male Japanese. Since prevalence of previous cardiovascular disease was significantly less in homozygous CC subjects, greater nocturnal BP decline in this genotype appears to be beneficial in the circadian BP rhythm.

Haplotypes of aldosterone synthase (CYP11B2) gene in the general population of Japan: the Ohasama study

Since the identification of a chimeric aldosterone synthase which induces mendelian hypertension, polymorphisms in aldosterone synthase (CYP11B2) has been one of major targets for molecular analyses in association with hypertension. To date, four polymorphic variants of CYP11B2, -344T/C at promoter region, a gene conversion in intron 2, 2713A/G (in exon 3) which converts from Lys to Arg at codon 173 (K173R), and 4986T/C (in exon7) which converts from Val to Ala at codon 386 (V386A), have been identified in Caucasian population. Then, linkage disequilibrium between -344T/C polymorphism and a gene conversion in intron 2 or K173R mutation has been described, suggesting the presence of genetic haplotypes in Caucasians. Since the presence of a gene conversion in intron 2 or V386A mutation was still unknown in the Japanese population, all these polymorphisms were examined together to determine the CYP11B2 haplotypes of Japanese, using DNA samples from 1290 participants of the Ohasama study, who represent the general population of a rural community of northern Japan. Molecular analyses demon- strated the presence of a gene conversion of intron 2, but the absence of V386A mutation in Japanese population. The complete linkage disequilibrium between -344T/C polymorphism and K173R mutation was noted. Although -344T allele was linked either with a gene conversion in intron 2 or with normal intron 2, -344C allele was completely linked with normal intron 2. These results indicate the presence of 3 allelic haplotypes of CYP11B2, -344C with normal intron 2 and 173R, -344T with normal intron 2 and 173K, and -344T with converted intron 2 and 173K, in the general Japanese population. The frequency (total 1.0) was 0.35, 0.53, and 0.12, respectively. The presence of allelic haplotypes is considered to be an additional genetic information to individual polymorphism of CYP11B2 to determine the linkage between CYP11B2 polymorphisms and hypertension.

Molecular basis of salt sensitivity in human hypertension. Evaluation of renin-angiotensin-aldosterone system gene polymorphisms

We analyzed the association between salt sensitivity in essential hypertension and 8 genetic polymorphisms in 6 genes of the renin-angiotensin aldosterone system. Seventy-one patients with essential hypertension were classified as salt sensitive or salt resistant by means of the 24-hour ambulatory blood pressure (BP) change to high salt intake. The polymorphisms evaluated correspond to the following genes: ACE (I/D), angiotensinogen (M235T), angiotensin II type 1 receptor (A1166C), 11beta-Hydroxysteroid dehydrogenase type 2 (11betaHSD2) (G534A), aldosterone synthase (C-344T and Intron 2 conversion), and the mineralocorticoid receptor (G3514C and A4582C); all were determined using standard polymerase chain reaction methods. Thirty-five patients (49%) were classified as salt sensitive. We analyzed the BP response to high salt intake among genotypes and found a significant association for ACE I/D and 11betaHSD2 G534A polymorphisms. Patients homozygous for the insertion allele of the ACE gene (II) had a significantly higher BP increase with high salt intake than did patients homozygous for the deletion allele (DD). Heterozygous patients (ID) exhibited an intermediate response. The prevalence of salt-sensitive hypertension was also significantly higher (P=0.003) in II (68%) and DI patients (59%) compared with DD hypertensives (19%). With respect to 11betaHSD2 G534A, patients with the GG genotype had a significantly higher systolic BP increase with high salt intake than did GA patients. In addition, plasma renin activity suppression in response to high salt was significantly greater in GA patients than in GG patients. The prevalence of salt-sensitive hypertension was 14.3% in GA patients and 50.8% in GG patients (P=0.067). In conclusion, the I allele of ACE I/D polymorphism is significantly associated to salt-sensitive hypertension. The BP response to high salt intake was different among genotypes of ACE I/D and 11betaHSD G534A, suggesting that these polymorphisms may be potentially useful genetic markers of salt sensitivity.

Effects of three candidate genes on prevalence and incidence of hypertension in a Caucasian population

BACKGROUND

The genes encoding angiotensin converting enzyme (ACE, I/D), alpha-adducin (ADD, Gly460Trp) and aldosterone synthase (AS, -344C/T) share the potential of influencing blood pressure (BP) via sodium homeostasis. However, most studies in humans focused on single-gene effects and disregarded epistasis, the suppression or potentiation of a gene by other non-allelic genes.

METHODS

We studied the singular and combined effects of the aforementioned candidate genes: (1) in relation to BP, plasma renin activity (PRA) and urinary aldosterone in 1461 subjects randomly selected from a Caucasian population; and (2) in relation to the incidence of hypertension in a subgroup of 678 initially normotensive subjects followed up for 9.1 years (median).

RESULTS

In cross-sectional analyses, AS/CC homozygosity was associated with slightly lower systolic BP (-1.32 mmHg; P = 0.08). AS/TT homozygotes showed both lower PRA and higher urinary aldosterone excretion (P < or = 0.05). In multiple-gene analyses, compared with the whole study population, ADD/Trp subjects had a higher relative risk of hypertension in the presence of the AS/T allele (1.29; P = 0.05), whereas in combination with AS/CC homozygosity ADD/Trp subjects had the smallest relative risk (0.48; P = 0.003). Hypertension developed in 229 subjects (36.6 cases per 1000 person-years). ACE/DD homozygosity, in comparison with the other ACE genotypes, was associated with increases in the incidence of hypertension, which amounted to 31% (P = 0.005) in single-gene analyses, to 59% (P = 0.004) in carriers of the ADD/Trp allele and to 122% (P = 0.0007) in AS/CC subjects. Among subjects who had both the ADD/Trp allele and the AS/CC genotype, ACE/DD homozygotes manifested a 252% (P = 0.001) higher incidence of hypertension.

CONCLUSIONS

Epistatic interactions between the ACE, ADD and AS genes contribute to the prevalence and incidence of hypertension in Caucasians. The clinical relevance of the risk-conferring haplotypes identified in our prospective study was underscored by their positive predictive values, which under the assumption of a 20% life-time risk of hypertension, ranged from 29.8-40.1%.

Lack of association between genetic polymorphism of CYP11B2 and hypertension in Japanese: the Suita Study

Aldosterone synthase (CYP11B2) is a key enzyme in the biosynthesis of aldosterone. Recently, a polymorphism in the 5'-flanking region of the CYP11B2 gene [T(-344)C] has been reported to be associated with blood pressure and plasma aldosterone levels. We investigated the association between this polymorphism and hypertension in a large population-based sample of 4,000 Japanese. The genotype distribution in hypertensive subjects (n=1,535) was compared to that in normotensive subjects (n=2,514). In subjects not receiving antihypertensive medication, the influence of the genotype on blood pressure values adjusted for clinical covariates was analyzed. All analyses were performed separately for men and women. The genotype distribution did not differ between hypertensive and normotensive subjects in either men (frequency of C allele: 30.3% vs. 31.4%, p=0.48) or women (31.5% vs. 31.7%, p=0.93). There were no significant differences in systolic blood pressure, diastolic blood pressure, or pulse pressure among the three genotypes in either men or women who had not received hypertensive medication. Our data suggest that the T(-344)C polymorphism of CYP11B2 is unlikely to influence blood pressure status in the Japanese population.

Genetic determination of human essential hypertension

Recent advances in genetic determination of human essential hypertension (EHT) are discussed by reviewing the candidate genes. Candidate genes have been selected based on genetic information from classical linkage analysis (affected sib-pair analysis) or mendelian hypertension (autosomal dominant inheritance of hypertension). Most of these genes are, directly or indirectly, coupled to salt handling of the kidney, being included in the renin-angiotensin system (RAS), steroid-hormone metabolism, and renal sodium transporters. Angiotensinogen (AGT) gene in RAS was first described as a strong candidate associated with the onset of hypertension, since sib-pair linkage analysis has demonstrated the trait loci for hypertension which includes the coding region for AGT. M235T polymorphism of AGT has been studied extensively in many populations including Japanese, and the results suggest a weak, but significant linkage with hypertension. The presence (insertion [I]) or absence (deletion [D]) of 287bp in intron 16 of angiotensin converting enzyme gene has also been examined in RAS, and the results suggest D polymorphism as a risk factor for hypertension in men. Other components in RAS, such as renin, angiotensinogen II type I receptor, or kallikrein have also been studied, but the available information is still incomplete. Genetic investigations of mendelian hypertension has identified the genetic mechanisms for glucocorticoid remediable aldosteronism, apparent mineral corticoid excess, and Liddle's syndrome as chimeric gene duplications of CYP11B1 (aldosterone synthase gene) and CYP11B2 (11beta-hydroxylase gene), mutations in the gene of 11beta-hydroxysteroid dehydrogenase type 2 that catalyzes the conversion of cortisol to cortisone, and mutations in beta or gamma subunit of epithelial sodium channel (ENaC), respectively. Subsequently, genetic variants of CYP11B2 and beta or gamma subunit of ENaC have been found, suggesting the -344C polymorphism of CYP11B2, 594S variant of betaENaC, and two rare variants of gammaENaC as risk factors for EHT. In spite of the extensive research, haplotypes in individual populations remain to be elucidcated in most candidate genes. Even casual conclusions of possible linkage with EHT need to be further examined with better determinations of phenotypes, such as ambulatory and home blood pressure monitoring or identification of onset of hypertension in cohort studies.

Salt and blood pressure

A substantial amount of new information concerning salt-sensitivity of blood pressure in humans has appeared in the recent past. This review discusses recent studies examining two techniques used for the assessment of salt sensitivity as well as several studies attempting to identify specific genetic factors associated with variations in the blood pressure responses to alterations in sodium and extracellular fluid volume. New observations related to the demographics, physiology, and mechanisms for these varied responses are also presented.