Genetic determination of human essential hypertension

Association of home blood pressure with sleep and physical and mental activity, assessed via a wristwatch-type pulsimeter with accelerometer in adults

This study aimed to examine the associations between home blood pressure (HBP) and sleep and activity assessed using data obtained via a wristwatch-type pulsimeter with accelerometer (Pulsense®) using original software. We recruited 28 elderlies and 40 employees aged 24-81 years who were not on hypotensive agents and sleeping drugs. Sleep, activity, and HBP were measured consecutively over a 5-7-day period. Body mass index (BMI), base heart rate (HR₀), and age showed significant correlation with HBP in a simple and multiple linear regression analysis. HR₀ was positively, and log deep sleep duration, negatively correlated with HBP in the adjusted multiple linear regression analysis. Physical and mental activities were negatively correlated with systolic blood pressure (SBP) in a simple linear regression, but high physical and mental activities tend to reduce deep sleep duration. Self-recorded sleep duration had no relationship with HBP. In conclusion, HR₀, BMI, age, deep sleep duration, and activity showed relationships with HBP. Using this type of wristwatch and observing daily sleep and activity data with HBP measurement may have important clinical implication.

Renin gene rs1464816 polymorphism contributes to chronic kidney disease progression in ADPKD

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) is a monogenic disorder and is a common genetic cause of chronic renal failure in children and adults. The enzyme renin plays a key role in the RAAS cascade and an important role in the development of hypertension and progression of renal disease in ADPKD. The present study is aimed to investigate the potential modifier effect of REN gene polymorphisms on the progression of chronic kidney disease (CKD) in ADPKD.

METHODS

We analyzed 102 ADPKD patients and 106 healthy controls from the same geographic area. FRET-based KASPar single-nucleotide polymorphism (SNP) genotyping assays for REN gene tag-SNPs (rs2887284, rs2368564, rs1464816, rs7521667, rs10900555, rs6693954, rs6676670 and rs11571078) were performed. Cochran-Armitage trend test was used to assess the potential associations between these polymorphisms and CKD stages. Haplotype frequencies and LD measures were estimated by using the software Haploview. Mantel-Haenszel stratified analysis was used to explore confounding and interaction effects of these polymorphisms.

RESULTS

Of the eight tag-SNPs genotyped, the rs10900555 polymorphism deviated from the Hardy-Weinberg equilibrium in controls. The presence of ADPKD in general was not significantly associated with the REN tag-SNPs included in this study. Linkage disequilibrium analysis yielded three haplotype blocks and the haplotypes of the respective blocks are not statistically different between ADPKD and controls. In multivariate analysis, the rs1464816 TG genotype showed a significant association with the advancement of CKD in ADPKD (OR = 4.80; 95 % CI = 1.30-17.82; p = 0.019).

CONCLUSIONS

The present study provides evidence that the rs1464816 polymorphism in REN is associated with CKD progression in ADPKD.

Renin gene polymorphisms in bangladeshi hypertensive population

OBJECTIVE

Linkages of renin gene polymorphisms with hypertension have been implicated in several populations with contrasting results. Present study aims to assess the pattern of renin gene polymorphisms in Bangladeshi hypertensive individuals.

METHODOLOGY

Introns 1, 9 of renin gene and 4063 bases upstream of promoter sequence of renin gene were amplified from the genomic DNA of the total 124 (hypertensive and normotensive) subjects using respective primers. Polymerase chain reaction-based restriction fragment length polymorphisms were performed using BglI, MboI and TaqI restriction enzymes.

RESULTS

Homozygosity was common in renin gene regarding BglI (bb=48.4%, Bb=37.9%, BB=13.7%, χ (2) =1.91, P>0.05), TaqI (TT=81.5%, Tt=14.5%, tt=4.0%, χ (2) =7.50, P<0.01) and MboI (mm=63.7%, Mm=32.3%, MM=4.0%, χ (2) =0.00, P>0.05) polymorphisms among total study population. For BglI and TaqI genotype distribution, hypertensive subjects (BglI: χ (2) =6.66, P<0.05; TaqI: χ (2) = 10.28, P<0.005) significantly deviate from Hardy-Weinberg Equilibrium law compared to normotensive subjects (BglI: χ (2) =0.51, P>0.05; TaqI: χ (2) =0.20, P>0.05). On the other hand, with respect to MboI polymorphisms of renin gene, only normotensive subjects deviate from the law (patients: χ (2) =1.28, P>0.05; vs controls: χ (2) =6.81, P<0.01). In the context of allelic frequency, common T allele was clearly prevalent (T frequency=0.86, t frequency = 0.14) for TaqI, but rare alleles b and m were more frequent for both BglI (b frequency=0.69, B frequency=0.31) and MboI (m frequency=0.80 M frequency=0.20) polymorphisms, respectively.

CONCLUSION

Thus, we report that Bangladeshi hypertensive subjects did not show any distinct pattern of renin gene polymorphisms compared to their healthy control subjects with regard to their genotypic and allelic frequencies.

Role of the renin-angiotensin-aldosterone system and the glutathione S-transferase Mu, Pi and Theta gene polymorphisms in cardiotoxicity after anthracycline chemotherapy for breast carcinoma

BACKGROUND

Anthracyclines are among the most active drugs against breast cancer, but can exert cardiotoxic effects eventually resulting in congestive heart failure (CHF). Identifying breast cancer patients at high risk of developing cardiotoxicity after anthracycline therapy would be of value in guiding the use of these agents.

AIMS

We determined whether polymorphisms in the renin-angiotensin-aldosterone system (RAAS) and in the glutathione S-transferase (GST) family of phase II detoxification enzymes might be useful predictors of left ventricular ejection fraction (LVEF) kinetics and risk of developing CHF. We sought correlations between the development of cardiotoxicity and gene polymorphisms in 48 patients with early breast cancer treated with adjuvant anthracycline chemotherapy.

METHODS

We analyzed the following polymorphisms: p.Met235Thr and p.Thr174Met in angiotensinogen (AGT), Ins/Del in angiotensin-converting enzyme (ACE), A1166C in angiotensin II type-1 receptor (AGTR1A), c.-344T>C in aldosterone synthase (CYP11B2), p.Ile105Val in GSTP1. Additionally, we analyzed the presence or absence of the GSTT1 and GSTP1 genes. A LVEF <50% was detected at least once during the 3 years of follow-up period in 13 out of 48 patients (27.1%).

CONCLUSION

RAAS gene polymorphisms were not significantly associated with the development of cardiotoxicity. GSTM1may be useful as a biomarker of higher risk of cardiotoxicity, as demonstrated in our cohort of patients (p=0.147).

Genetic polymorphisms influence runners' responses to the dietary ingestion of antioxidant supplementation based on pequi oil (Caryocar brasiliense Camb.): a before-after study

Genes have been implicated in the levels of oxidative stress, lipids, CVD risk, immune reactivity, and performance. Pequi oil (Caryocar brasiliense) has shown anti-inflammatory and hypotensive effects, besides reducing exercise-induced DNA, tissue damages, and anisocytosis. Given that diet can interact with the human genome to influence health and disease, and because genetic variability can influence response to diet, we aim to investigate the influence of 12 gene polymorphisms on inflammatory markers, postprandial lipids, arterial pressure, and plasma lipid peroxidation of runners (N = 125), before and after 14 days of 400 mg pequi-oil supplementation, after races under closely comparable conditions. Arterial pressure was checked before races; blood samples were taken immediately after racing to perform leukogram and plateletgram, Tbars assay, lipid, and CRP dosages and genotyping. CAT, GST-M1/T1, CRP-G1059C, and MTHFR-C677T polymorphisms influenced post-pequi-oil responses in leukogram; Hp and MTHFR-C677T, in plateletgram; Hp, ACE, GSTT1, and MTHFR-A1298C, in lipid profile; MTHFR-A1298C, in C-reactive protein (CRP) levels; and Hp and MnSOD, in Tbars assay. Differences between ACE genotypes in leukogram and total cholesterol disappeared after pequi, and the same occurred for Hp and MnSOD in Tbars assay and for MTHFR-A1298C with CRP levels. Because genetic inheritance is one of the factors that drive atherosclerosis-related lipid abnormalities, results can contribute to a greater understanding of the influence of genetic polymorphisms in situations that push up free radicals. Knowledge is also expanded on how antioxidant supplementation affects an individual's genes and how athletic genetic makeup can affect the way a person responds to antioxidant supplements.

Seasonal blood pressure variation and its relationship to environmental temperature in healthy elderly Japanese studied by home measurements

The purpose of the present study was to examine seasonal blood pressure variation and its relationship to environmental temperature in healthy elderly Japanese, as studied by home measurements. Fifteen healthy elderly Japanese (79.3 +/- 5.9 yrs) measured their blood pressure at home each morning for more than 25 times per month for 3 years. Monthly mean outdoor temperatures were obtained from the Takamatsu meteorological Observatory. The highest levels of systolic and diastolic blood pressure measured at home were observed in February (129 +/- 14 and 81 +/- 13 mmHg). The lowest levels of systolic and diastolic blood pressure measured at home were observed in August (117 +/- 11 and 73 +/- 10 mmHg). Likewise, the lowest and highest means of outdoor temperature were observed in February (5.0 degrees C) and August (29.2 degrees C), respectively. Hence, both systolic and diastolic blood pressure demonstrated a close inverse correlation with the means of outdoor temperature (r = -0.973, p < 0.001 and r = -0.985, p < 0.001, respectively). A 1 degree C decrease in the mean outdoor temperature was associated with rises of 0.43 mmHg in systolic blood pressure (SBP) and 0.29 mmHg in diastolic blood pressure (DBP). Seasonal variations in home blood pressure and outdoor temperature showed complete correspondence in healthy elderly Japanese, with the blood pressures being inversely related to the ambient temperature. These seasonal home blood pressure variations should be kept in mind when controlling blood pressure in elderly patients.

Investigation of Major Genetic Polymorphisms in the Renin-Angiotensin-Aldosterone System in Subjects with Young-Onset Hypertension Selected by a Targeted-Screening System at University

Although polymorphisms in renin-angiotensin-aldosterone (RAA) system genes for angiotensinogen (AGT M235T), angiotensin-converting enzyme (ACE I/D), angiotensin II type 1 receptor (AT1 A/C1166), and aldosterone synthase (CYP11B2-344T/C) have been major targets for genetic investigation in association with essential hypertension (EH), the influence of these genetic factors is still to be determined. Because patients with young-onset EH are thought to possess a stronger genetic background than EH patients who show elevated BP relatively late in life, the targeted screening of hypertensive students in Tohoku University was completed for the selection of subjects for genetic investigation. Out of 16,434 students (12,794 males and 3,670 females) younger than 30, 22 students showed a high blood pressure (BP) (systolic and diastolic BP of 140 and/or 90 mmHg or greater, respectively, on two occasions and more than 135 and/or 85 mmHg, respectively, at a third measurement during casual BP measurements at the Tohoku University Health Center. These 22 students were asked to measure their BP at home (HBP). Six of the students had a systolic HBP of more than 135 mmHg and/or a diastolic HBP of more than 85 mmHg, and these students subsequently received medical examinations at Tohoku University Hospital and were diagnosed with EH. Genotyping for the four major genetic polymorphisms mentioned above was performed on the six students with EH and on 12 of the remaining 16 students whose HBP was within the normal range (white coat hypertension: WCH). Neither the EH nor the WCH students showed a different distribution of genotypes and allelic frequencies, compared to those found in the general Japanese population. Hence, the present study suggests that none of the major genetic polymorphisms in the RAA system strongly influence the onset of EH.

Hyperaldosteronism in pregnancy

Aldosterone is a key regulator of electrolyte and water homeostasis and plays a central role in blood pressure regulation. Hormonal changes during pregnancy, among them increased progesterone and aldosterone production, lead to the required plasma volume expansion of the maternal body as an accommodation mechanism for fetus growth. This review discusses the regulation of aldosterone production by aldosterone synthase (CYP11B2); the impact on aldosterone secretion due to the presence of a chimeric gene originating from a crossover between CYP11B1 and CYP11B2 in glucocorticoid remediable aldosteronism (GRA) — the inherited form of hypertension; enhanced aldosterone production in aldosterone-producing adenoma (APA); and idiopathic hyperaldosteronism (IHA). Features of hyperaldosteronism are also found in patients with apparent mineralocorticoid excess (AME), in which glucocorticoids exacerbate activation of the mineralocorticoid receptor (MR) because of a defect in the 11β-hydroxysteroid dehydrogenase type 2 enzyme. Regulation of aldosterone production and tissue-specific activation of the mineralocorticoid receptor are prerequisites for optimal control of body fluids and blood pressure during pregnancy and contribute largely to the wellbeing of the mother-to-be.

Interaction of angiotensin I-converting enzyme insertion-deletion polymorphism and daily salt intake influences hypertension in Japanese men

The contribution of angiotensin I-converting enzyme insertion-deletion polymorphism (ACE I/D) to salt-sensitivity hypertension has been extensively studied by means of salt-loading tests, but whether or not the interaction with daily salt intake affects blood pressure still remains to be clarified. We therefore conducted a cross-sectional study of 284 Japanese male workers (age range, 20-64 years) to examine the effect of ACE I/D genotype and daily salt intake on hypertension. Blood pressure was measured and the ACE I/D was identified by polymerase chain reaction (PCR). Daily salt intake was calculated from a food frequency questionnaire (FFQ). In multivariate analyses, we explored the interaction of ACE I/D and salt intake by means of logistic regression analysis and multiple linear regression analysis. ACE I/D per se was not associated with blood pressure levels or hypertension. ACE I/D interacted with daily salt intake and correlated with hypertension (p for interaction = 0.047). In the ID+II genotype, hypertension was increased by high salt intake (p = 0.005), while in the DD genotype it was not (p = 0.257). The interaction was more prominent in the overweight group (p = 0.039) than in non-overweight group. In the overweight group, high salt intake induced a 10.5 mmHg higher diastolic blood pressure in the ID+II genotype than in the DD genotype (p = 0.042). Our results suggest that ACE I/D and daily salt intake constitute a gene-environment interaction, which may be further modulated by overweight.

Kidney Dysfunction and Hypertension: Role for Cadmium, P450 and Heme Oxygenases?

Cadmium (Cd) is a metal toxin of continuing worldwide concern. Daily intake of Cd, albeit in small quantities, is associated with a number of adverse health effects which are attributable to distinct pathological changes in a variety of tissues and organs. In the present review, we focus on its renal tubular effects in people who have been exposed environmentally to Cd at levels below the provisional tolerable intake level set for the toxin. We highlight the data linking such low-level Cd intake with tubular injury, altered abundance of cytochromes P450 (CYPs) in the kidney and an expression of a hypertensive phenotype. We provide updated knowledge on renal and vascular effects of the eicosanoids 20-hydroxyeicosatetraenoic acid (20-HETE) and eicosatrienoic acids (EETs), which are biologically active metabolites from arachidonate metabolism mediated by certain CYPs in the kidney. We note the ability of Cd to elicit "oxidative stress" and to alter metal homeostasis notably of zinc which may lead to augmentation of the defense mechanisms involving induction of the antioxidant enzyme heme oxygenase-1 (HO-1) and the metal binding protein metallothionein (MT) in the kidney. We hypothesize that renal Cd accumulation triggers the host responses mediated by HO-1 and MT in an attempt to protect the kidney against injurious oxidative stress and to resist a rise in blood pressure levels. This hypothesis predicts that individuals with less active HO-1 (caused by the HO-1 genetic polymorphisms) are more likely to have renal injury and express a hypertensive phenotype following chronic ingestion of low-level Cd, compared with those having more active HO-1. Future analytical and molecular epidemiologic research should pave the way to the utility of induction of heme oxygenases together with dietary antioxidants in reducing the risk of kidney injury and hypertension in susceptible people.

Renal Sodium Handling for Body Fluid Maintenance and Blood Pressure Regulation

Renal sodium handling is an essential physiologic function in mammal for body fluid maintenance and blood pressure regulation. Recent advances in molecular biology have led to the identification of kidney-specific sodium transporters in the renal tubule, thereby supplying vast information for renal physiology as well as systemic physiology. Renal urinary concentration for body fluid maintenance is accomplished by counter current multiplication in the distal tubule. Sodium transport in the thick ascending limb of Henle (TAL) is the initial process of this system. We have demonstrated that renal urinary concentration is regulated in part by the expression of the Na(+)-K(+)-2Cl(-) co-transporter (BSC1) in TAL, by showing two mechanisms of BSC1 expression: pitressin vasopressin (AVP)-dependent and AVP-independent mechanisms. Two additional findings, namely, a lack of the ability to increase BSC1 expression leads to urinary concentrating defect and an enhanced BSC1 expression underlies the edema-forming condition, confirm the close association between sodium handling in TAL and body fluid accumulation. The lines of evidence from our genetic studies of the general Japanese population suggest the importance of mendelian hypertension genes in the genetic investigation of essential hypertension. Because those genes directly or indirectly regulate sodium transport by the Na-Cl co-transporter or the epithelial sodium channel in the distal convoluted tubule to the collecting duct (distal tubular segments after TAL), sodium handling in this part of the renal tubule may be, at least in part, involved in blood pressure regulation. The unveiling of such physiologic roles of sodium handling based on the sodium transporters or on the tubular segments may lead to a better understanding of systemic physiology as well as to the development of novel therapy for body fluid or blood pressure disorders.

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.

A/C1166 gene polymorphism of the angiotensin II type 1 receptor (AT1) and ambulatory blood pressure: the Ohasama Study

We previously investigated the relation between hypertension and each of three major genetic polymorphisms in the renin-angiotensin (AGT)-aldosterone system (R-A-A), AGT M235T, angiotensin convert enzyme (ACE) I/D, and CYP11B2 -344C/T, by means of ambulatory blood pressure (ABP) monitoring in a general Japanese population (the Ohasama Study). A/C1166 gene polymorphism in the 3' untranslated region of the angiotensin II type 1 receptor (AT1) gene is the final remaining major target in R-A-A to be examined in the Ohasama Study population. In the present study, the AT1 A/C1166 polymorphism was genotyped by the TaqMan polymerase chain reaction (PCR) method or restriction fragment length polymorphism (RFLP) in 802 Japanese subjects aged 40 and over, who were previously genotyped for the AGT M235T, ACE D/I, CYP11B2 -344C/T polymorphisms. The AA genotype, AC genotype, and CC genotype were present in 678 (84.5%), 121 (15.1%), and 3 (0.4%) of subjects, respectively. Since the frequency of the C allele was quite low (0.079), the genotypes were classified according to the presence or absence of the C allele. Although daytime blood pressure (BP) was higher in subjects with the C allele, the difference was not statistically significant after adjusting for age, gender, body mass index, and smoking status. No significant difference was noted in the prevalence of cardiovascular diseases or nocturnal BP decline between the two groups. These results indicated that AT1 A/C1166 polymorphism was not associated with any clinical parameters associated with hypertension or atherosclerosis in the Japanese population.

T+31C polymorphism (M235T) of the angiotensinogen gene and home blood pressure in the Japanese general population: the Ohasama Study

The angiotensinogen (AGT) gene polymorphism M235T (a methionine to threonine amino acid substitution) has been investigated in association with essential hypertension (EHT) based on conventional measurement of blood pressure (BP); however, the results have been inconsistent. Recently, we have been conducting lines of genetic analysis on a general population of Ohasama Town in Iwate Prefecture, Japan, who measured their BP at home (Ohasama genetic analysis and home BP project). We here assessed the association between AGT M235T polymorphism and hypertension within the same population (1,245 subjects aged 40 years and over). AGT M235T polymorphism was determined by genotyping the AGT T+31C polymorphism, which has complete disequilibrium with the AGT M235T polymorphism. We defined subjects as hypertensive if they were being treated with antihypertensive medication and/or had home BP values of more than 135 mmHg in systole and/or 85 mmHg in diastole. The genotype frequencies were similar to those in previous Japanese studies. There was no significant difference among the genotypes in home BP values (p = 0.63/0.74 for systolic/diastolic blood pressure) or in prevalence of hypertension (MM: 44.7%; MT: 42.3%; TT: 39.6%; p = 0.61). No difference was noted in the frequency of familial history of hypertension. Pulse pressure, however, was significantly different among the genotypes (p = 0.049), and this association was prominent in the older (age260) population (p = 0.0018), but not noted in the younger population (60 > age > or = 40). In conclusion, the present analysis confirmed the lack of a significant effect of AGT M235T polymorphism on blood pressure level, but the difference in pulse pressure in the older population suggests that further investigations of this polymorphism should be made in the Japanese population.

Genetic polymorphisms in the beta-subunit of the epithelial sodium channel (βENaC) gene in the Japanese population

BACKGROUND

Mutations have been found only in exons 8 and 12 of the β-subunit of the epithelial sodium channel (βENaC), but the presence of other mutations in the remaining exons remains to be determined in the Japanese population. New cases with the V434M mutation should be identified because the identified individuals have high plasma sodium concentration

METHODS

Exons 1 to 7 and 9 to 11 were screened by using single-strand conformational polymorphism (SSCP) in 200 subjects (100 normotensive and 100 hypertensive) randomly selected from 1245 participants in a community-based cohort study (Ohasama study) in northern Japan

RESULTS

Four novel mutations were detected in exons 5, 6, and 7, and one of them was the novel missense mutation, P369H in exon 6. Then extended investigation of this mutation, together with those of V434M and P592S, which were identified in our previous studies, was performed in 1245 subjects. The final frequency of these mutations was 1/1245 for P369H, 5/1245 for V434M, and 5/1245 for P592S. Although a significant association with hypertension was not achieved, 3 of the 5 subjects with V434M were diagnosed as hypertensive. Plasma sodium concentrations were significantly high and plasma renin activity tended to be low in subjects with V434M. The only subject with P369H showed slightly elevated diastolic pressure, but no other abnormal characteristics were noted in the subjects with P369H or P592S CONCLUSIONS: Genetic polymorphisms of βENaC in the Japanese population were determined. Clinical features in those with the V434M mutation suggest the presence of physiological effects of this mutation on plasma sodium regulation.

Angiotensin-converting enzyme I/D polymorphism and hypertension: the Ohasama study

OBJECTIVE

Angiotensin-converting enzyme (ACE) I/D polymorphism in intron 16 of the ACE gene was analyzed in a general Japanese population in relation to self-blood pressure (BP) measurement at home (home BP) and ambulatory BP monitoring (ABPM) to determine the association between genetic variants of this polymorphism and hypertension.

DESIGN

A cross-sectional study.

METHODS AND RESULTS

We genotyped the ACE I/D polymorphism in 1245 subjects with home BP and 803 subjects with ABPM in Ohasama, a rural community in Japan. All the subjects were 40 years of age and over, and gave written informed consent for the present genetic analysis. Hypertensive subjects were defined as those receiving antihypertensive drugs and those who had a home BP higher than 135 mmHg in systole and/or higher than 85 mmHg in diastole. The frequencies of the II, ID, and DD genotypes in these Japanese subjects were 0.45, 0.45, and 0.10, indicating a lower frequency of the D allele (0.33) than in Caucasians. There was no significant difference of BP level, prevalence of hypertension or nocturnal decline in BP among the genotypes. There were no differences in the prevalence of previous cardiovascular disease, age, body mass index, male gender, smoking, or biochemical and hormonal parameters among the three genotypes.

CONCLUSION

The present results indicate the absence of direct effects of the ACE D-allele on BP level, prevalence of hypertension, prevalence of cardiovascular disease, and circadian BP variation. We conclude there is little association between ACE I/D polymorphism and hypertension in the general Japanese population.

Genotypes of the betaENaC gene have little influence on blood pressure level in the Japanese population

The gene for the beta-subunit of the epithelial sodium channel (betaENaC) is one of the most prominent candidate genes being analyzed for an association with human essential hypertension. It is known that a deletion or alteration of PY motif in exon 12 of betaENaC is responsible for Liddle's syndrome. Although the localization of genetic polymorphisms of betaENaC is unique to each population, intensive analysis of individuals of white and African ancestry has demonstrated that genetic variants are localized in exons 8 and 12, with two frequent polymorphisms, G442V in exon 8 and T594M in exon 12. These two mutations are both found in individuals of African ancestry, and might be associated with elevated blood pressure (BP). Previously, we have screened the last two-thirds of exon 12 in the Japanese population, and demonstrated the absence of the T594M mutation and the presence of a novel P592S mutation. In the present study, we further examined the rest of exon 12 and exon 8 in a general population from Ohasama, Japan (the Ohasama Study), using single-strand conformational polymorphism (SSCP) analysis. We screened 803 subjects randomly selected from the representative participants, who measured their home and casual BP. The PCR products presenting a shift in SSCP gels, as well as controls, were directly sequenced by autoanalyzer to identify the mutation. A novel gel shift was noted in exon 12 (n = 8) and sequencing identified a polymorphism at codon Ser 520, leading to no change in amino acid sequence (G77576C TCG-->TCC). In exon 8, all three SSCP variants were heterogynous for V434M (GTG-->ATG), which is coincident with a rare polymorphism in whites. The G442V mutation, however, was absent from the Japanese population. A novel mutation of exon 12 was not associated with a significant difference in clinical features. These results indicate that Japanese people possess three polymorphisms in exon 12, all of which are unique, and one in exon 8. These genetic variants of betaENaC may not influence the BP level of Japanese people.

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.