Variation in the region of the angiotensin-converting enzyme gene influences interindividual differences in blood pressure levels in young white males

Gene Polymorphism and Total Genetic Score in Martial Arts Athletes with Different Athletic Qualifications

The personalized approach in sports genetics implies considering the allelic variants of genes in polymorphic loci when adjusting the training process of athletes. The personalized approach is used both in sports genetics and in medicine to identify the influence of genotype on the manifestations of human physical qualities that allow to achieve high sports results or to assess the impact of genotype on the development and course of diseases. The impact of genes of the renin-angiotensin and kinin-bradykinin systems in the development of cardiovascular disease in athletes has not been defined. This study aims to determine the polymorphisms of four genes (ACE, BDKRB2, PPARGC1A and NOS3) and the total genetic score to reveal the predisposition to the formation of physical qualities in martial arts athletes with different athletic abilities. The products of these four genes are involved in the control of blood pressure. The allelic variants of these genes are associated with the development of the physical quality "endurance" and have an indirect influence on the formation of speed and power qualities. The total genetic score (TGS: from 0 to 100 arbitrary units) was calculated from the genotype score in each polymorphism. The athletes were divided into Group I with high and Group II with low qualifications depending on their sports success. Single nucleotide polymorphisms (SNPs) are identified through restriction endonucleases cleavage for PCR amplicons for discriminating between alleles of the target genes ACE (rs4646994), BDKRB2 (rs5810761), PPARGC1A (rs8192673) and NOS3 (rs1799983). Significant differences between the allelic variants of target genes and athletic ability were found between Group I and Group II for genotype G/G of NOS3 gene and genotypes Gly/Gly and Gly/Ser of PPARGC1A gene. The data obtained confirm that athletes with unfavourable genotypes are excluded in the screening phase because their endurance is not fully developed to the required level in martial arts. Martial arts athletes with the highest TGS have the highest skill level. Polymorphic loci of four genes whose products are involved in blood pressure control (ACE, BDKRB2, NOS3 and PPARGC1A) can be used in martial arts not only to determine predisposition to cardiovascular disease but also to predispose to the development of speed and power qualities and endurance. The total genetic score can serve as a tool for predicting athletic success.

Effects of Acute Aquatic High-Intensity Intermittent Exercise on Blood Pressure and Arterial Stiffness in Postmenopausal Women with Different ACE Genotypes

The present study investigated the effects of acute aquatic high-intensity intermittent jumping (HIIJ) on blood pressure (BP) and arterial stiffness in postmenopausal women with different angiotensin-converting enzyme genotypes (ACE). We recruited 12 postmenopausal women carrying the ACE deletion/deletion (DD) genotype and 61 carrying the insertion/insertion or insertion/deletion (II/ID) genotype. The participants performed 12 trials of 30 s, 75% heart rate reserve (HRR) jumping, and 60 s, 50% HRR recovery, and 3 trials of 40 s upper limb resistance exercises were performed as fast as possible. The heart rate (HR) and BP were measured before exercise, immediately, 10 min, and 45 min after exercise. The brachial-ankle pulse wave velocity (baPWV) was measured before and after exercise. The systolic blood pressure (SBP) of the DD genotype increased more significantly than those with the II/ID genotype post-exercise (30.8 ± 4.48 vs. 20.4 ± 2.00 mmHg, p = 0.038). The left and right sides of baPWV increased significantly after exercise (1444.8 ± 29.54 vs. 1473.4 ± 32.36 cm/s, p = 0.020; 1442.1 ± 30.34 vs. 1472.0 ± 33.09, p = 0.011), and there was no significant difference between the two groups. The HIIJ increased baPWV. The postmenopausal women with the DD genotype have a higher SBP increased post-exercise than those with II/ID genotype. These findings suggest that the aquatic exercise program has better effects in decreasing blood pressure in postmenopausal women with the II/ID genotype. Those with the DD genotype should pay attention to the risk of increasing blood pressure after aquatic HIIJ exercise.

Renin-angiotensin system gene polymorphisms and high blood pressure in Lithuanian children and adolescents

Background

Epidemiological studies have demonstrated the influence of environmental factors on HBP in the population of Lithuanian children, although the role of genetic factors in hypertension has not yet been studied. The aim of this study was to assess the distribution of AGTR1, AGT, and ACE genotypes in the Lithuanian child population and to determine whether these genotypes have an impact on HBP in childhood.

Methods

This cross-sectional study enrolled 709 participants aged 12–15 years. The subjects were genotyped for AGT (M235 T, rs699), AGTR1 (A1166C, rs5186), and ACE (rs4340) gene polymorphisms using real-time and conventional polymerase chain reactions. Blood pressure and anthropometric parameters were measured.

Results

The prevalence of HBP was 38.6% and was more frequently detected in boys than in girls (47.9% vs. 29.5%; p < 0.001). No significant differences in the frequencies of the AGT or AGTR1 genotypes or alleles between boys and girls were observed, except for ACE genotypes. The mean SBP value was higher in HBP subjects with ACE ID genotype compared to those with ACE II homozygotes (p = 0.04). No significant differences in BP between different AGT and AGTR1 genotype groups were found. Boys who carried the ACE ID + DD genotypes had higher odds of having HBP than carriers of the ACE II genotype did (controlling for the body mass index (BMI): OR_MH = 1.83; 95% CI, 1.11–3.02, p = 0.024; and controlling for waist circumference (WC): OR_MH = 1.76; 95% CI, 1.07–2.92, p = 0.035). These associations were not significant among girls. The same trend was observed in the multivariate analysis – after adjustment for BMI and WC, only boys with ACE ID genotype and ACE ID + DD genotypes had statistically significantly increased odds of HBP (aOR = 2.05; 95% CI, 1.19–3.53 (p = 0.01) and aOR = 1.82; 95% CI, 1.09–3.04 (p = 0.022), respectively).

Conclusions

The evaluated polymorphisms of the AGT and AGTR1 genes did not contribute to the presence of HBP in the present study and may be seen as predisposing factors, while ACE ID genotypes were associated with significantly increased odds for the development of HBP in the Lithuanian child and adolescent population - especially in boys.

Interaction of ACE genotype and salt intake on hypertension among Chinese Kazakhs: results from a population-based cross-sectional study

OBJECTIVES

To explore the effect of interaction between ACE genotype and salt intake on hypertension among Chinese Kazakhs, and to compare applications of interactions between logistic model and generalised partially linear tree-based regression (GPLTR) model.

DESIGN

Population-based cross-sectional study.

SETTING

Hong Dun, North Xinjiang, China.

PARTICIPANTS

Non-consanguineous Chinese Kazakh participants (n=916, 342 men and 574 women) aged ≥30 years.

MAIN OUTCOME MEASURES

Association between ACE genotype and hypertension, association between salt intake and hypertension, and interaction of ACE genotype and salt intake on hypertension in two models.

RESULTS

Associations between salt intake and hypertension were different in ACE genotype of II and ID+DD. Under the logistic models, main and interaction effects were not observed for men, but effects were present in opposite directions for women (main effect of ACE: OR=0.20, p=0.003; interaction effect: OR=1.07, p=0.027). Under the GPLTR model, Bayesian information criterion trees included both salt intake and ACE genotype as split variables. Individuals with a salt intake ≥19.5 g/day and ID+DD genotypes had a 3.99-fold (p=0.004) higher risk of hypertension compared with the II genotype for men, whereas salt intake <20.1 g/day and ID+DD genotypes had an OR=0.55 (p=0.014) compared with the II genotype for women.

CONCLUSIONS

An interaction of ACE genotype and salt intake on hypertension was observed among Chinese Kazakhs but in different ways according to sex. The GPLTR model appears to be more suitable for an exploration of interactions in complex diseases.

Association of the polymorphism 12109g>A from the REN gene as a risk factor for preterm birth

INTRODUCTION

Preterm birth is the most important cause of neonatal mortality and morbidity. It is a multifactorial disease with different etiologies, including genetic factors. Genetic variability is represented by single nucleotide polymorphisms (SNPs) in genes of proteins involved in the contractile activity. We determine the association between SNP 12109G> A in REN associated with preterm birth and premature rupture of membrane.

MATERIALS AND METHODS

A study of cases ( N=112, 22-36 weeks of gestation; mean: 31, 95% confidence interval 30.7-32.2) and controls ( N=66; 38-40 weeks of gestation from the last menstrual period; mean: 39.8, 95% confidence interval 38.9-39.4) was performed. Genomic DNA was isolated in all patients from peripheral blood. The SNP 12109G> A ( Mbo I) in REN was typified by PCR-restriction fragment length polymorphism.

RESULTS

A significant difference in the case group for the SNP 12109G>A was observed. The A allele was increased in women with preterm birth (81% cases vs. 15% control, p<0.0000004). There was also a significant difference between genotypes, mainly an excess of G/A heterozygotes in women with preterm birth (60% cases vs. 23% controls). The phenotype 12109G> A has odds ratio 6.62 (95% confidence interval 3.14-14.15), which means a high risk of preterm birth/premature rupture of membrane in presence of allele A, both in homozygotes and in heterozygotes.

CONCLUSION

Allelic frequency of A of SNP 12109G>A was higher in women with preterm birth than in women with normal vaginal delivery and could be considered a risk factor.

Renal Haemodynamics are not Related to Genotypes in Offspring of Parents with Essential Hypertension

Introduction. The pathogenesis of essential hypertension (EH) has a major genetic component and is associated with renal abnormalities. Normotensive offspring of hypertensive parents are likely to develop EH and are a suitable population for identifying possible relations between genetic and renal abnormalities.

Methods. We investigated if renin-angiotensin-aldosterone system associated genotypes (angiotensinogen [M235T] and ACE [I/D]) are related to blood pressure (BP), renal haemodynamics and sodium excretion in sex and age-matched (18—35 years) healthy Caucasian offspring of either two parents with EH (n=101, EH-offspring) or two normotensive parents (n=50, controls). The alpha-adducin polymorphism (G460W) was also investigated.

Results. Compared to controls, BP, heart rate, renal vascular resistance (RVR) and urinary sodium excretion were, respectively, 5%, 7%, 15% and 20% higher in EH-offspring. In controls, the TT-genotype of the M235T angiotensinogen polymorphism was associated with higher BP and higher plasma angiotensinogen. By contrast, in EHoffspring the TT-genotype was associated with lower BP and unchanged plasma angiotensinogen. Plasma angiotensinogen correlated positively with BP in EH-offspring, with a similar tendency (p=0.08) in controls. The distributions of the three candidate polymorphisms were similar in EH-offspring and controls. There were no associations between any of the polymorphisms and any of the renal parameters measured.

Conclusion. The markedly greater RVR, proportionally larger than the greater BP, supports a role for RVR in the pathogenesis of EH. The lack of association between the candidate polymorphisms and the investigated parameters, even in this homogenous and for hypertension strongly predisposed group, suggests that the polymorphisms investigated do not play important roles in the pathogenesis of hypertension.

Molecular genetics of essential hypertension

Hypertension is a major public health problem in the developing as well as in developed countries due to its high prevalence and its association with coronary heart disease, renal disease, stroke, peripheral vascular disease, and related disorders. Essential hypertension (EH) is the most common diagnosis in this disease, suggesting that a monocausal etiology has not been identified. However, a number of risk factors associated with EH have also been identified such as age, sex, demographic, environmental, genetic, and vascular factors. Recent advances in molecular biological research had achieved clarifying the molecular basis of Mendelian hypertensive disorders. Molecular genetic studies have now identified mutations in several genes that cause Mendelian forms of hypertension in humans. However, none of the single genetic variants has emerged from linkage or association analyses as consistently related to the blood pressure level in every sample and in all populations. Besides, a number of polymorphisms in candidate genes have been associated with differences in blood pressure. The most prominent candidate has been the polymorphisms in the renin-angiotensin-aldosterone system. In total, EH is likely to be a polygenic disorder that results from inheritance of a number of susceptibility genes and involves multiple environmental determinants. These determinants complicate the study of blood pressure variations in the general population. The complex nature of the hypertension phenotype makes large-scale studies indispensable, when screening of familial and genetic factors was intended. In this review, recent genetic studies exploring the molecular basis of EH, including different molecular pathways, are highlighted.

The effect of puberty on diurnal sodium regulation

The aim of this study was to investigate the impact of sex and puberty stage on circadian changes in sodium excretion, sodium-regulating hormones, and hemodynamics. Thirty-nine healthy volunteers (9 prepuberty boys, 10 prepuberty girls, 10 puberty boys, and 10 puberty girls) were included. They all underwent a 24-h circadian in-patient study under standardized conditions regarding activity, diet, and fluid intake. Blood samples were drawn every 4 h, and the urine was collected in fractions. Blood pressure and heart rate were noninvasively monitored. Atrial natriuretic peptide (ANP), angiotensin II, aldosterone, and renin were measured in blood. Children in puberty had lower plasma levels of renin (P<0.05) and angiotensin II (P<0.05) and a 26% reduction in filtered sodium without changes in sodium excretion compared with prepuberty children. A circadian rhythm in sodium excretion, the renin-angiotensin system, ANP, and blood pressure was found with a midnight ANP peak (P<0.001), a nighttime decrease in hemodynamic parameters (P<0.001), an increase in plasma renin (P<0.001) and angiotensin II (P<0.001), and a decrease in sodium excretion (P<0.001) mainly on the basis of increased sodium reabsorption (P<0.001). The timing of the changes did not depend on sex or puberty group. There is a circadian rhythm of sodium excretion and sodium regulation in 7- to 15-yr-old children. This rhythm is similar in boys and girls. As an important new finding, puberty changes the plasma levels of renin and angiotensin II without changing the amount of sodium excreted or the day to night sodium excretion ratio.

The renal protective effect of angiotensin receptor blockers depends on intra-individual response variation in multiple risk markers

AIMS

Angiotensin receptor blockers (ARBs) are renoprotective and targeted to blood pressure. However, ARBs have multiple other (off-target) effects which may affect renal outcome. It is unknown whether on-target and off-target effects are congruent within individuals. If not, this variation in short term effects may have important implications for the prediction of individual long term renal outcomes. Our aim was to assess intra-individual variability in multiple parameters in response to ARBs in type 2 diabetes.

METHODS

Changes in systolic blood pressure (SBP), albuminuria, potassium, haemoglobin, cholesterol and uric acid after 6 months of losartan treatment were assessed in the RENAAL database. Improvement in predictive performance of renal outcomes (ESRD or doubling serum creatinine) for each individual using ARB-induced changes in all risk markers was assessed by the relative integrative discrimination index (RIDI).

RESULTS

SBP response showed high variability (mean -5.7 mmHg, 5(th) to 95(th) percentile -36.5 to +24.0 mmHg) between individuals. Changes in off-target parameters also showed high variability between individuals. No congruency was observed between responses to losartan in multiple parameters within individuals. Using individual responses in all risk markers significantly improved renal risk prediction (RIDI 30.4%, P < 0.01) compared with using only SBP changes. Results were successfully replicated in two independent trials with irbesartan, IDNT and IRMA-2.

CONCLUSIONS

In this post hoc analysis we showed that ARBs have multiple off-target effects which vary between and within individuals. Combining all ARB-induced responses beyond SBP provides a more accurate prediction of who will benefit from ARB therapy. Prospective trials are required to validate these findings.

The ACE I/D polymorphism is associated with nitric oxide metabolite and blood pressure levels in healthy Mexican men

The I/D insertion/deletion polymorphism of the angiotensin-converting enzyme has been related to hypertension. This polymorphism also seems to have gender related implications. Angiotensin II contributes to the production and release of oxygen reactive species that react with nitric oxide, inactivating its effects.

OBJECTIVE

To establish whether the ACE I/D polymorphism correlates with nitric oxide plasma metabolites in healthy men and women.

METHODS

Among 896 subjects between 18 and 30 years of age range, 138 fulfilled inclusion criteria. The polymorphism was identified by polymerase chain reaction, and blood nitric oxide metabolites were analyzed following the method described by Bryan.

RESULTS

Both systolic and diastolic arterial pressures were higher in men than in women (107/67 vs. 101/65 mm Hg, p<0.001). In terms of the ACE gene, there were differences in the concentration of nitric oxide metabolites in men with the I/D and D/D genotypes when compared to carriers of the I/I genotype (33.55 and 29.23 vs. 53.74 pmol/ml; p=<0.05), while there were no significant differences in women when compared by genotype. Men with the D/D genotype had higher systolic blood pressure than I/D carriers (111 vs. 104 mm Hg, p<0.05). We observed no arterial blood pressure differences in women when grouped by ACE genotype.

CONCLUSIONS

The ACE D/D genotype was associated with nitric oxide metabolite levels and systolic blood pressure in clinically healthy men while it had no effect in women.

Insertion/deletion polymorphism of the angiotensin-converting enzyme gene and the risk of hypertension among residents of two cities, South-South Nigeria

BACKGROUND

Hypertension is a public health challenge due to its high prevalence, and is a major risk factor for cardiovascular diseases. This study was designed to determine the frequency of the I/D polymorphism of the angiotensin-converting enzyme gene and its association with hypertension in a sample population of Calabar and Uyo, South-South Nigeria.

MATERIALS AND METHODS

A population-based case control design consisting of total of 1224 participants, 612 each of patients and controls, were randomly recruited from hypertension clinics and the general population. The I/D polymorphism was investigated using polymerase chain reaction. Multiple regression and odds ratio (OR) was applied to test whether the ID genotypes were predictors of hypertension.

RESULTS

The I/D genotype frequencies were 73(12%), 262(43%) and 277(45%); 74(12%), 303(50%) and 235(38%) for the II, ID, DD genotype in patient and control groups, respectively. A higher frequency of the ID genotype was observed in controls of which 208(61%) were females. By multiple regression analysis, age was a predictor for SBP in patients, r = 0.596, and DBP in controls, r = 0.555. Gender, Body mass index, I/D genotypes were not significant predictors for hypertension but the I/D polymorpism was associated with an increased risk for hypertension with an OR of 1.15 95%CI (0.924-1.456).

CONCLUSION

The I/D polymorphism of the angiotensin-converting enzyme gene was a risk factor for hypertension in the sample population of Calabar and Uyo. This research will form baseline information for subsequent molecular studies in this population.

Angiotensin converting enzyme insertion/deletion polymorphism is associated with increased adiposity and blood pressure in obese children and adolescents

BACKGROUND

The insertion/deletion polymorphism in the gene encoding the angiotensin-converting enzyme (ACE I/D) was associated with arterial hypertension and obesity in adults, but the data in children are scarce and yielded contrasting results. We assessed the impact of the ACE I/D on blood pressure and obesity related traits in a Brazilian cohort of obese children and adolescents.

METHODS AND RESULTS

ACE I/D was genotyped in 320 obese children and adolescents (64% of girls) aged 7-16years, referred for a weight-loss program. We observed an association of the D-allele with blood pressure and with pre-hypertension/hypertension in boys (odds ratio 2.44, 95% C.I. 1.34-4.68, p=0.005 for a codominant model). The D-allele, insulin resistance and body fat mass had independent and additive effects and explained 14% of the variance of pre-hypertension/hypertension. The BMI, waist circumference, and body fat mass were significantly higher in DD/ID boys than in II boys (p<0.005). Allelic associations with obesity related traits were independent of the association with blood pressure. No genotype associations were observed in girls.

CONCLUSIONS

The D-allele of the ACE I/D polymorphism was associated with arterial hypertension and with obesity related traits in boys, but not in girls, in a cohort of obese children and adolescents. These associations were independent of each other, as well as of the effects of other confounding traits such as insulin secretion, insulin sensitivity and glucose tolerance. Our results are in agreement with experimental evidences suggesting that the renin-angiotensin system plays a role in the regulation of visceral adipose tissue accumulation.

Between candidate genes and whole genomes: time for alternative approaches in blood pressure genetics

Blood pressure has a significant genetic component, but less than 3% of the observed variance has been attributed to genetic variants identified to date. Candidate gene studies of rare, monogenic hypertensive syndromes have conclusively implicated several genes altering renal sodium balance, and studies of essential hypertension have inconsistently implicated over 50 genes in pathways affecting renal sodium balance and other functions. Genome-wide linkage scans have replicated numerous quantitative trait loci throughout the genome, and over 50 single nucleotide polymorphisms (SNPs) have been replicated in multiple genome-wide association studies. These studies provide considerable evidence that epistasis and other interactions play a role in the genetic architecture of blood pressure regulation, but candidate gene studies have limited scope to test for epistasis, and genome-wide studies have low power for both main effects and interactions. This review summarizes the genetic findings to date for blood pressure, and it proposes focused, pathway-based approaches involving epistasis, gene-environment interactions, and next-generation sequencing to further the genetic dissection of blood pressure and hypertension.

The higher exercise intensity and the presence of allele I of ACE gene elicit a higher post-exercise blood pressure reduction and nitric oxide release in elderly women: an experimental study

BACKGROUND

The absence of the I allele of the angiotensin converting enzyme (ACE) gene has been associated with higher levels of circulating ACE, lower nitric oxide (NO) release and hypertension. The purposes of this study were to analyze the post-exercise salivary nitrite (NO2-) and blood pressure (BP) responses to different exercise intensities in elderly women divided according to their ACE genotype.

METHODS

Participants (n = 30; II/ID = 20 and DD = 10) underwent three experimental sessions: incremental test - IT (15 watts workload increase/3 min) until exhaustion; 20 min exercise 90% anaerobic threshold (90% AT); and 20 min control session without exercise. Volunteers had their BP and NO2- measured before and after experimental sessions.

RESULTS

Despite both intensities showed protective effect on preventing the increase of BP during post-exercise recovery compared to control, post-exercise hypotension and increased NO2- release was observed only for carriers of the I allele (p < 0.05).

CONCLUSION

Genotypes of the ACE gene may exert a role in post-exercise NO release and BP response.

Gene variants of the renin–angiotensin system and hypertension: from a trough of disillusionment to a welcome phase of enlightenment?

There is substantial evidence to suggest that BP (blood pressure) is an inherited trait. The introduction of gene technologies in the late 1980s generated a sharp phase of over-inflated prospects for polygenic traits such as hypertension. Not unexpectedly, the identification of the responsible loci in human populations has nevertheless proved to be a considerable challenge. Common variants of the RAS (renin–angiotensin system) genes, including of ACE (angiotensin-converting enzyme) and AGT (angiotensinogen) were some of the first shown to be associated with BP. Presently, ACE and AGT are the only gene variants with functional relevance, where linkage studies showing relationships with hypertension have been reproduced in some studies and where large population-based and prospective studies have demonstrated these genes to be predictors of hypertension or BP. Nevertheless, a lack of reproducibility in other linkage and association studies has generated scepticism that only a concerted effort to attempt to explain will rectify. Without these explanations, it is unlikely that this knowledge will translate into the clinical arena. In the present review, we show that many of the previous concerns in the field have been addressed, but we also argue that a considerable amount of careful thought is still required to achieve enlightenment with respect to the role of RAS genes in hypertension. We discuss whether the previously identified problems of poor study design have been completely addressed with regards to the impact of ACE and AGT genes on BP. In the context of RAS genes, we also question whether the significance of ‘incomplete penetrance’ through associated environmental, phenotypic or physiological effects has been duly accounted for; whether appropriate consideration has been given to epistatic interactions between genes; and whether future RAS gene studies should consider variation across the gene by evaluating ‘haplotypes’.

Angiotensin-converting enzyme gene insertion/deletion polymorphism frequency in normotensive children with a positive family history of essential hypertension

AIM

To evaluate the possible relationship between blood pressure (BP) and angiotensin-converting enzyme (ACE) gene insertion/deletion (I/D) polymorphism in normotensive children with a positive family history of essential hypertension (EHT).

MATERIAL AND METHODS

Three hundred seventy-six randomly selected normotensive schoolchildren (147 boys, 229 girls) between the ages of seven and 17 years were enrolled. Children were subdivided into a 'first-degree relative group' and a 'second-degree relative group' according to the presence of EHT in parents or grandparents, respectively. BP was measured twice from the right arm and the systolic BP, diastolic BP and mean BP were recorded. ACE gene I/D polymorphism was performed from all studied children and frequency od DD, ID and ID allele were analysed in each study group.

RESULTS

Allelic frequencies of the DD genotype of the ACE gene were higher in children with a positive history in the first- (36.2%) and second-degree (38.3%) relatives for EHT than the controls (30.7%) (P < 0.05 for both). Children with a positive family history of EHT and a DD genotype, had significantly higher SBP, DBP and MBP levels (P < 0.05) than the children with ID or II genotypes.

CONCLUSION

We found that the ACE gene DD genotype was common and that BP levels were higher in Turkish children with a positive family history of EHT and DD genotype. Because the presence of DD allele might be the one of the potential contributor of EHT pathogenesis, further studies needed in large cohort for long term follow-up for EHT in children with DD allele.

Multi-locus interactions of vascular homeostasis genes in essential hypertension: a gender-based study

BACKGROUND

Studies on genes of endothelial and vascular homeostasis are inadequate in females.

METHODS

We investigated the role of 7 variants of ACE, AGT and NOS3 and their correlation with NO(x) levels and ACE activity in hypertension susceptibility in 910 case-controls of both genders.

RESULTS

Prevalence of alleles D of ACE I/D; -6A of AGT -6G/A; -786C, 894T and 4a of NOS3 -786T/C, 894G/T and 4b/4a polymorphisms was observed in patients (P< or =0.05). The 3 genotypes-combinations containing 6+5 wild-type alleles of AGT and NOS3 were significantly less prevalent in patients (P< or =0.0003). The haplotypes 235T/174T/-6A of AGT (P=4E-3) and -786T/894G/4a and -786C/894G/4a of NOS3 (P=2E-3, P=0.011, respectively) were significantly more prevalent in patients. The AGT and NOS3 findings were similar in males. Genotypes-combinations with 6+5 wild-type alleles of AGT correlated with higher NO(x) levels (P=0.03). The NOS3 genotypes-combinations having 6 and 6+5 wild-type alleles correlated with decreased ACE activity (P=0.025, P=0.0015, respectively) and increased NO(x) levels (P=0.001, P=0.0001, respectively) in patients. In gene-gene interactions, ACE D allele associated with < or =4 wild-type alleles containing genotypes-combinations of AGT and NOS3 in patients (P< or =0.04).

CONCLUSION

Within gene and between genes interactions of variants influence ACE activity and NO(x) levels and associate with EH.

ACE I/D genotype, adiposity, and blood pressure in children

Background

Angiotensin converting enzyme (ACE) is a possible candidate gene that may influence both body fatness and blood pressure. Although several genetic studies have been conducted in adults, relatively few studies have examined the contribution of potential candidate genes, and specifically ACE I/D, on adiposity and BP phenotypes in childhood. Such studies may prove insightful for the development of the obesity-hypertension phenotype early in life. The purpose of this study was to examine differences in body fatness and resting blood pressure (BP) by ACE I/D genotype, and determine if the association between adiposity and BP varies by ACE I/D genotype in children.

Methods

152 children (75 girls, 77 boys) were assessed for body composition (% body fat) using dual energy x-ray absorbtiometry and resting BP according to American Heart Association recommendations. Buccal cell samples were genotyped using newly developed PCR-RFLP tests for two SNPs (rs4341 and rs4343) in complete linkage disequilibrium with the ACE I/D polymorphism. Partial correlations were computed to assess the ociations between % body fat and BP in the total sample and by genotype. ANCOVA was used to examine differences in resting BP by ACE I/D genotype and fatness groups.

Results

Approximately 39% of youth were overfat based on % body fat (>30% fat in girls, 25% fat in boys). Body mass, body mass index, and fat-free mass were significantly higher in the ACE D-carriers compared to the II group (p < 0.05). BP was not significantly different by ACE I/D genotypes. In the total sample, correlations between adiposity and BP ranged from 0.30 to 0.46, and were not significantly different between genotypes. When grouped by genotype and body fat category, the overfat D-carrier subjects had significantly higher SBP and MAP compared to the normal fat D-carrier and normal fat II groups (p < 0.05).

Conclusion

ACE D-carriers are heavier than ACE II children; however, BP did not differ by ACE I/D genotype but was adversely influenced in the overfat D-carriers. Further studies are warranted to investigate the genetics of fatness and BP phenotypes in children.

Effect of angiotensin-converting enzyme gene polymorphism on left ventricular remodeling after anteroseptal infarction

BACKGROUND AND HYPOTHESIS

Genetic influence on cardiac remodeling is uncertain. The purpose of this study is to determine the effects of polymorphism of the angiotensin-converting enzyme (ACE) gene on cardiac remodeling after myocardial infarction.

METHODS

The subjects were 43 patients with old anteroseptal myocardial infarction. Based on the polymorphism of the ACE gene, they were classified into a deletion group of 25 patients (D/D genotype in 4 and D/I genotype in 21) and an insertion group of 18 patients (all I/I genotype). Echocardiograms were used to determine left ventricular end-diastolic and end-systolic diameters, interventricular septal and posterior wall thicknesses, left ventricular mass, left atrial diameter, and left ventricular ejection fraction. Blood concentrations of atrial and brain natriuretic peptide were also measured.

RESULTS

Left ventricular end-systolic and end-diastolic dimensions, left ventricular mass, and levels of both atrial and brain natriuretic peptide were significantly higher in the deletion group. In contrast, septal thickness, posterior wall thickness, and ejection fraction showed no differences between the two groups.

CONCLUSIONS

In patients with old anteroseptal infarction, ACE gene polymorphism of the D/D and D/I genotypes has a stronger influence on left ventricular remodeling than polymorphism of the I/I genotype.

Influence of angiotensin-converting enzyme gene polymorphism on development of athlete's heart

BACKGROUND AND HYPOTHESIS

Genetic influence on development of athlete's heart is uncertain. This study investigated whether angiotensin-converting enzyme (ACE) gene polymorphism influenced development of athlete's heart.

METHODS

Forty-three participants in a 100-km ultramarathon were classified on the basis of ACE gene polymorphism into a deletion group (n = 26) and an insertion group (n = 17). Echocardiograms were recorded to determine left ventricular end-diastolic and end-systolic diameters, interventricular septal thickness, left ventricular posterior wall thickness, left ventricular mass, and ejection fraction.

RESULTS

Left ventricular end-diastolic diameter (65.5 +/- 4.0 mm) and left ventricular mass (369.5 +/- 73.9 g) were significantly larger in the subjects with deletion than in those with insertion (57.4 +/- 4.2 mm, 306.5 +/- 93.7 g). However, no significant differences in the other parameters were noted.

CONCLUSIONS

In long-distance runners, ACE gene polymorphism of the D/D and D/I genotypes has a stronger influence on left ventricular hypertrophy than polymorphism of the I/I genotype.

Genetic influences on 24 h blood pressure profiles in a hypertensive population: role of the angiotensin-converting enzyme insertion/deletion and angiotensin II type 1 receptor A1166C gene polymorphisms

OBJECTIVE

Data on the association of the ACE I/D and AT1R A1166C polymorphisms with hypertension are conflicting. Most studies, however, have focused on office blood pressure (BP) only. The objective of the present study was to investigate the association of BP with the angiotensin-converting enzyme insertion/deletion (ACE I/D) and angiotensin II type 1 receptor A1166C (AT1R A1166C) polymorphisms by means of both office and ambulatory blood pressure monitoring (ABPM).

METHODS AND RESULTS

A total of 348 hypertensive patients participated in this study. Office BP did not differ between the various ACE or AT1R genotype groups. However, ambulatory BP and BP load were positively associated with the ACE I/D polymorphism. This was more apparent in men than in women. There were no differences in heart rate, BP variability, and amount of dipping. The AT1R A1166C polymorphism showed no consistent association with blood pressure (load).

CONCLUSION

From these data we conclude that frequent measuring of blood pressure by ABPM is crucial to find an association of the ACE D allele with various aspects of blood pressure.

Sex-specific genetic architecture of human disease

Sexual dimorphism in anatomical, physiological and behavioural traits are characteristics of many vertebrate species. In humans, sexual dimorphism is also observed in the prevalence, course and severity of many common diseases, including cardiovascular diseases, autoimmune diseases and asthma. Although sex differences in the endocrine and immune systems probably contribute to these observations, recent studies suggest that sex-specific genetic architecture also influences human phenotypes, including reproductive, physiological and disease traits. It is likely that an underlying mechanism is differential gene regulation in males and females, particularly in sex steroid-responsive genes. Genetic studies that ignore sex-specific effects in their design and interpretation could fail to identify a significant proportion of the genes that contribute to risk for complex diseases.

Association of renin-angiotensin system and natriuretic peptide receptor A gene polymorphisms with hypertension in a Hellenic population

Introduction. Hypertension results from the interaction of genetic and environmental factors. Since the renin-angiotensin and the natriuretic peptide systems contribute to blood pressure regulation, variations in the relative genes are candidates for the development of hypertension.

Materials and methods. In 194 hypertensives and 304 controls of Hellenic origin, the possible association between the (CA)n repeat polymorphism of angiotensinogen (AGT), the 250 bp insertion/deletion (I/D) of angiotensin-converting enzyme (ACE), the tetranucleotide repeat polymorphism (TCTG)n of renin, and the (CT)n repeat polymorphism of the natriuretic peptide receptor A (NPRA) and hypertension was assessed.

Results. No association between AGT and NPRA polymorphisms and hypertension was observed. The presence of ID or DD genotype of ACE was associated with an increased risk for hypertension compared with the II genotype (OR: 1.782 [95% CI: 1.032—3.077]), whereas the LL genotype of the renin gene was associated with a decreased risk compared with the SS genotype (OR: 0.174 [95% CI: 0.044—0.689]). However, after adjustment for confounding factors only the latter association remained.

Conclusions. In the present study conducted in a homogeneous Hellenic population, no associations betweenAGT,ACE, and NPRA gene polymorphisms and hypertension were found. The presence of a significant negative association between the LL polymorphism of the renin gene and hypertension requires further confirmation.

Interaction of gender, hypertension, and the angiotensinogen gene haplotypes on the risk of coronary artery disease in a large angiographic cohort

There is increasing evidence suggesting the importance of evaluating gene-environment interactions in the genetic study of coronary artery disease (CAD). We investigated the association of multiple single nucleotide polymorphisms in the angiotensinogen (AGT) gene with CAD, considering the interaction between the genetic and non-genetic factors, using a larger and ethnically homogeneous angiographic cohort. A total of 1254 consecutive patients who underwent cardiac catheterization (735 with CAD and 519 without) were recruited. T174M (rs4762), M235T (rs699), G-6A, A-20C, G-152A, and G-217A polymorphisms of the AGT gene were genotyped. We used a regression approach based on a generalized linear model to evaluate haplotype effects defined by the multilocus data and detection of gene-environment interaction by incorporating interaction terms in the model. We found significant differences in global AGT gene haplotype profile between patients with and without CAD (the global score statistic=25.411, P=0.008). Significant interactions between AGT gene haplotypes, gender and hypertension were detected. We also used haplotype counting to directly estimate the odds ratio of each AGT gene haplotype, and found that the effects of haplotypes were markedly different in subgroups defined by gender and hypertension, providing strong evidence of gene-environment interaction. Female gender synergistically enhances (or male gender reverses) the effects of AGT gene haplotypes on the risk of CAD in the presence of hypertension. In conclusion, the effect of AGT gene haplotypes on the risk of CAD was significantly increased in women with hypertension, which highlights the importance of evaluating gene-environment interactions in the genetic study of CAD.

The geographic distribution of the ACE II genotype: a novel finding

Angiotensin converting enzyme (ACE) gene polymorphism insertion (I) or deletion (D) has been widely studied in different populations, and linked to various functional effects and associated with common diseases. The purpose of the present study was to investigate the relationship between the ACE I/D frequency in different populations and geographic location; ACE I/D allele frequency in the Lebanese population and ACE II genotype contribution to the geographic trend were also identified. Five hundred and seventy healthy volunteers were recruited from the Lebanese population. Genomic DNA was extracted from buccal cells, and amplified by polymerase chain reaction; products were then identified by gel electrophoresis. The frequencies of the different ACE I/D genotypes were determined and tested for Hardy-Weinberg equilibrium (HWE). To assess the relationship between ACE I/D frequency and geographic location, and to identify how the Lebanese population contributes to the geographic trend in ACE I/D frequencies, Eurasian population samples and Asians were incorporated in the analyses from the literature. The frequency of the I allele in the Lebanese population was 27% and the corresponding II genotype was at a frequency of 7.37% (in HWE; P=0.979). The ACE I allele and genotype frequencies show an association with longitude, with frequencies increasing eastwards and westwards from the Middle East.

Effects of angiotensin-converting enzyme gene polymorphism and serum vitamin D levels on ambulatory blood pressure measurement and left ventricular mass in Turkish hypertensive population

INTRODUCTION

Regulation of angiotensin converting enzyme (ACE) and angiotensin II (ang-II) levels is under genetic control. 1,25(OH)2 vitamin D3 treatment has been shown to reduce the ang-II level, reduce myocardial hypertrophy and to decrease blood pressure. This study was designed to examine the effect of ACE gene polymorphisms on 24-h ambulatory blood pressure measurement (24 h) values, vitamin D levels and target organ damage in hypertensive patients.

METHODS

This study was carried on 118 patients with essential hypertension (female/male: 70/48, mean age: 49.1+/-7.6 years, hypertension duration: 56+/-40.5 months). All patients were assessed for target organ damage; the eye by retinal examination, the heart with echocardiography and the kidney with blood and 24-h urine analysis. 24-h ambulatory blood pressure measurement was performed in all patients. PCR amplification was employed to detect ACE genotypes.

RESULTS

ACE genotypes were as follows: DD (n=49) 41.5%; ID (n=37) 31.4% and II (n=32) 27.1%. No difference was present between groups of ACE polymorphism when 24-h ambulatory blood pressure measurement values, retinal vascular changes and microalbuminuria were taken into account. Statistically significant left ventricular mass index levels were obtained in the DD group when compared with the non-DD (ID+II) group (P : 0.009). Positive correlations have been noted between left ventricular mass index and day/night and early morning systolic pressures. A negative correlation exists between serum 25 (OH) vitamin D levels and 24-h ambulatory blood pressure measurement values (P<0.05).

CONCLUSIONS

The presence of the D allele is linked with a higher risk for left ventricular mass index in the Turkish hypertensive population.

Angiotensin I-converting enzyme insertion-related genotypes and allele are associated with higher susceptibility of endometriosis and leiomyoma

Endometriosis and leiomyoma display features similar to malignancy, requiring neovascularization to proliferation and growth. Altered vascular-related genes might be related to the development of endometriosis and leiomyoma. Polymorphisms of the angiotensin-converting enzyme (ACE) insertion/deletion (I/D) genes have been linked with some vascular diseases. This study investigates whether ACE I/D gene polymorphisms could be used as markers of susceptibility in endometriosis and leiomyoma. Women were divided into three groups: (1) endometriosis (n = 125); (2) leiomyoma (n = 120); (3) normal controls (n = 128). Genomic DNA was obtained from peripheral leukocyte. ACE I/D gene polymorphisms in intron 16 were amplified by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) Genotypes and allelic frequencies in both groups were compared. We observed the genotype distribution and allele frequency of ACE I/D gene polymorphisms in both groups were significantly different. Proportions of ACE*I homozygote/heterozygote/D homozygote in both groups were: (1) 50.4/24/25.6%; (2) 25/23.33/51.67%; (3) 10.2/29.7/60.1%. Proportions of I/D alleles in each group were: (1) 62.4/37.6%; (2) 36.7/63.3%; (3) 25/75%. We concluded that ACE*I/D gene polymorphisms are associated with endometriosis and leiomyoma susceptibilities. ACE*I-related genotypes and allele are strongly related to the occurrence of endometriosis and moderately related to the occurrence of leiomyoma.

Insertion/deletion gene polymorphism of the angiotensin-converting enzyme and blood pressure changes in older adults. The Rotterdam study

The insertion/deletion (I/D) polymorphism of the angiotensin converting enzyme (ACE) gene may be involved in determining blood pressure changes. The aim of the present study was to assess the relationship between the ACE I/D gene and the change of blood pressure levels during follow-up. We calculated the difference between mean levels of SBP, DBP and PP obtained during the two observations as follows: BP mean levels obtained at third phase minus the BP mean levels at baseline and subsequently we investigated the association of the ACE I/D polymorphism and the mean changes of SBP, DBP and PP levels. The study was conducted within the Rotterdam Study, a population-based cohort study including subjects aged 55 years and older. Information on the II, ID and DD genotypes of the ACE gene and mean change of blood pressure levels were available in 3966 subjects. In adjusted models, subjects with the D allele had higher mean changes of systolic and pulse pressure (PP) than subjects with the I allele. The mean changes of systolic blood pressure were 6.1 (4.7-7.5), 8.2 (7.5-9.3) and 7.4 (5.9-8.5) mm Hg in subjects with the II, ID and DD genotype, respectively. The corresponding mean changes of PP through genotypes were 4.3 (3.3-5.4), 6.0 (5.3-6.7) and 5.9 (4.9-6.9) mm Hg, respectively. No difference was found for mean change of diastolic blood pressure among genotypes. In conclusion, the results of this population-based study show that the ACE ID/DD genotypes are associated with increased mean changes of systolic and PP.

Endothelin-1 gene and endothelial nitric oxide synthase gene polymorphisms in adolescents with juvenile and obesity-associated hypertension

Hypertension is an increasing public health problem all over the world. Essential hypertension accounts for more than 90% of cases of hypertension. It is a complex genetic, environmental and demographic trait. New method in molecular biology has been proposed a number of candidate genes, but the linkage or association with hypertension has been problematic (lack of gene-gene and gene-environment interaction). It is well known that genetic influences are more important in younger hypertensives, because children are relatively free from the common environmental factors contributing to essential hypertension. The association studies compare genotype ferquencies of the candidate gene between patient groups and the controls, in pathways known to be involved in blood pressure regulation. This study examined three polymorphisms of these factors encoding genes (ET-1 G+5665T (Lys198Asn), endothelial nitric oxide synthase (eNOS) T-786C promoter polymorphism and 27-bp repeat polymorphism in intron 4) in adolescents with juvenile essential and obesity-associated hypertension. Significant differences were found in the G/T genotype of the ET-1 polymorphism in the hypertensive and obese+hypertensive patients (body mass index (BMI) > 30). A strong association was detected between the BMI and the polymorphism of the ET-1 gene. It seems that ET-1 gene polymorphism plays a role in the development of juvenile hypertension associated with obesity. Although no significant differences were seen in the case of the eNOS promoter polymorphism and the eNOS 4th intron 27-bp repeat polymorphism. It seems that eNOS may play a role, but this is not the main factor in the control of blood pressure; it is rather a fine regulator in this process. This study with adolescents facilitates an understanding of the genetic factors promoting juvenile hypertension and obesity.

Genetics of arterial hypertension and hypotension

Human hypertension affects affects more than 20% of the adult population in industrialized countries, and it is implicated in millions of deaths worldwide each year from stroke, heart failure and ischemic heart disease. Available evidence suggests a major genetic impact on blood pressure regulation. Studies in monogenic hypertension revealed that renal salt and volume regulation systems are predominantly involved in the genesis of these disorders. Mutations here affect the synthesis of mineralocorticoids, the function of the mineralocorticoid receptor, epithelial sodium channels and their regulation by a new class of kinases, termed WNK kinases. It has been learned from monogenic hypotension that almost all ion transporters involved in the renal uptake of Na(+) have a major impact on blood pressure regulation. For essential hypertension as a complex disease, many candidate genes have been analysed. These include components of the renin-angiotensin-aldosterone system, adducin, beta-adrenoceptors, G protein subunits, regulators of G protein signalling (RGS) proteins, Rho kinases and G protein receptor kinases. At present, the individual impact of common polymorphisms in these genes on the observed blood pressure variation, on risk for stroke and as predictors of antihypertensive responses remains small and clinically irrelevant. Nevertheless, these studies have greatly augmented our knowledge on the regulation of renal functions, cellular signal transduction and the integration of both. Together, this provides the basis for the identification of novel drug targets and, hopefully, innovative antihypertensive drugs.

Angiotensin-Converting Enzyme Gene 2350 G/A Polymorphism Is Associated with Left Ventricular Hypertrophy but Not Essential Hypertension

The angiotensin-converting enzyme (ACE) gene (ACE) is one of the most studied candidate genes related to essential hypertension (EH) and left ventricular hypertrophy (LVH). ACE rs4343 synonymous coding polymorphism (2350 G/A) is known among the polymorphisms of this gene to have the most significant effect on plasma ACE concentrations. The aim of the present study was to investigate the association of this polymorphism with EH and LVH in 440 subjects (246 EH patients and 194 controls) from a Chinese Han population. In this study, 2350 G/A genotypes were identified by polymerase chain reaction and restriction digestion in all study participants, and left ventricular mass was assessed by 2-mode echocardiography in 178 untreated EH patients. There was no significant difference in either genotype distribution (p=0.3659) or allele frequency (p=0.1453) between EH and control groups. In addition, the 2350 G/A polymorphism had no effect on blood pressure in either controls or untreated EH patients. The distribution of genotypes differed significantly when patients with LVH were examined, i.e., 14.71% GG, 54.41% GA, and 30.88% AA patients had this complication, and 36.36% GG, 42.73% GA, and 20.91% AA patients did not (p=0.0070). The LVH patients had a higher A allele frequency (58.09%) than patients without LVH (42.27%) (p=0.0037). Logistic regression analysis revealed that the association between the A allele and LVH was independent of age, blood pressure, and body mass index. The relative risk of LVH in patients bearing the A allele (GA+AA group) compared with that of GG hypertensive patients was 3.31 (95% confidence interval [CI]: 1.43 to 7.68). These findings suggest an association between LVH and the 2350A allele in hypertensive patients.

Molecular genetics of human hypertension

EH (essential hypertension) is a major public health problem in many countries due to its high prevalence and its association with coronary heart disease, stroke, renal disease, peripheral vascular disease and other disorders. Epidemiological studies have demonstrated that EH is heritable. Owing to the fact that blood pressure is controlled by cardiac output and total peripheral resistance, many molecular pathways are believed to be involved in the disease. In this review, recent genetic studies investigating the molecular basis of EH, including different molecular pathways, will be highlighted.

Endothelial NOS G894 T and MMP-3 5A/6A gene polymorphisms and hypertension in Serbian population

The incidence of hypertension is increasing and it is more common in man than in women. Up to date, MMP-3 5A/6A polymorphism has been associated with artery stiffening and elevated blood pressure, whereas results considering association of endothelial NOS (eNOS) G894 T polymorphism with hypertension are controversial. The aim of our study was to analyze the possible association of eNOS G894 T and MMP-3 5A/6A gene polymorphisms with hypertension in Serbian population. Study sample consisted of 172 hypertensive and 200 normotensive subjects divided by gender. Both female and male group was truncated according to age. All subjects were genotyped for MMP-3 5A/6A and eNOS G894 T polymorphism. There was a significantly higher (P < 0.05) prevalence of 5A/5A genotype in hypertensive females compared to normotensive ones (19.30 % vs. 10.84%) even more pronounced in group > or =50 years, according to its recessive effect. In young males (<40 years), we found 3.7-fold increased risk for hypertension associated with allele 6A (P < 0.01), and 8.1-fold with genotype 6A/6A (P = 0.01) according to recessive model. We found no association of eNOS G894 T polymorphism with hypertension. These results indicate that there were gender- and age-specific differences in association of MMP-3 5A/6A polymorphism with hypertension in Serbian population.

RAAS polymorphisms alter the acute blood pressure response to aerobic exercise among men with hypertension

Limited evidence suggests renin-angiotensin-aldosterone system (RAAS) polymorphisms alter the blood pressure (BP) response to aerobic exercise training. We examined if RAAS polymorphisms influenced postexercise hypotension in men with high normal to Stage 1 hypertension. Forty-seven men (44.2+/-1.4 years, 145.1+/-1.6/85.5+/-1.1 mmHg) randomly completed three experiments: seated rest (control) and two cycle exercise bouts at 40% (LITE) and 60% (MOD) of maximal oxygen consumption. Ambulating BP was measured for 14 h after each experiment. RAAS polymorphisms associated with hypertension (i.e. angiotensin converting I enzyme, ACE I/D; angiotensin II type 1 receptor, AT1R A/C; and intron 2 of aldosterone synthase, Int2 W/C) were analyzed using polymerase chain reaction and restriction enzyme digestion. Repeated measure ANOVA tested if BP differed between experimental conditions by RAAS genotypes. Compared to men with 0-2 variant alleles, men with > or =3 combined RAAS variant alleles had lower average systolic BP (SBP) (P=0.030) and lower average diastolic BP (DBP) (P=0.009) for 14 h only after LITE. In contrast, average BP was not different for MOD and control between RAAS variant allele groups over this time period (P> or =0.05). LITE reduced BP in men with > or =3 variant RAAS alleles for 14 h, whereas MOD had no influence on BP in these men. In order to optimally prescribe exercise for its BP lowering benefits in those with hypertension, additional knowledge of how genetic variation affects the BP response to exercise is needed.

Genetic determinants of blood pressure regulation

Hypertension is a multifactorial disorder that probably results from the inheritance of a number of susceptibility genes and involves multiple environmental determinants. Existing evidence suggests that the genetic contribution to blood pressure variation is about 30-50%. Although a number of candidate genes have been studied in different ethnic populations, results from genetic analysis are still inconsistent and specific causes of hypertension remain unclear. Furthermore, the abundance of data in the literature makes it difficult to piece together the puzzle of hypertension and to define candidate genes involved in the dynamic of blood pressure regulation. In this review, we attempt to highlight the genetic basis of hypertension pathogenesis, focusing on the most important existing genetic variations of candidate genes and their potential role in the development of this disease. Our objective is to review current knowledge and discuss limitations to clinical applications of genotypic information in the diagnosis, evaluation and treatment of hypertension. Finally, some principles of pharmacogenomics are presented here along with future perspectives of hypertension.

The role of the cytochrome P450 3A5 enzyme for blood pressure regulation in the general Caucasian population

Cytochrome P450 3A (CYP3A) enzymes are important for drug metabolism in gut and liver. The CYP3A5 isoenzyme is also expressed in the kidney and has been implicated in renal sodium reabsorption and blood pressure regulation. Its expression and activity is strongly linked to a polymorphism (i.e. 6986G > A). Thus, appreciable expression is found in carriers of the CYP3A5*1 (6986A) but not in homozygous carriers of the CYP3A5*3 (6986G) allele. We tested whether the presence of CYP3A5*1 affects blood pressure in Caucasian individuals who were enrolled in the Prevention of REnal and Vascular ENd stage Disease (PREVEND) study. In addition, we evaluated whether the genetic effect of CYP3A5*1 on blood pressure is modulated by sodium intake. CYP3A5*1 was found in 13.3% (901 individuals) of the cohort (6777 individuals). Diastolic blood pressure was not affected by CYP3A5*1. Overall, systolic and pulse pressure were significantly lower in carriers of CYP3A5*1, both after univariate analysis adjusted for age (P = 0.012 and P = 0.008) and in logistic regression analysis (P = 0.015 and P = 0.012). The effect on systolic blood pressure was significantly modulated by sodium intake (P = 0.038). In separate analysis according to gender, CYP3A5*1 accounted for a significant age adjusted decrease in systolic blood pressure (-1.6 mmHg, P = 0.04) and pulse pressure (-1.2 mmHg, P = 0.04) in females but not in men. The present study demonstrates that the CYP3A5*1 allele affects systolic blood pressure and pulse pressure in the general population. Its role in hypertensive disease and potential gender differences should be investigated in further studies.

Association of angiotensin-converting enzyme 2 (ACE2) gene polymorphisms with parameters of left ventricular hypertrophy in men. Results of the MONICA Augsburg echocardiographic substudy

Angiotensin-converting enzyme (ACE) activity is considered to be of major importance for the conversion of angiotensin (Ang) I to Ang II. Recently, a second ACE, named ACE2, has been identified. Experimental data provide evidence that ACE2 might be involved in modulating cardiac structure and function. In the present explorative study, we assessed whether polymorphisms in the ACE2 gene are related to echocardiographically determined parameters of left ventricular mass, structure or function in the general population. Five intronic single nucleotide polymorphisms (SNPs) were genotyped using the 5'-exonuclease activity (TaqMan) assay in the echocardiographic substudy of the third MONICA Augsburg survey. As ACE2 is located on the X chromosome, women and men were analysed separately. Four SNPs showed high pairwise linkage disequilibrium (rs4646156, rs879922, rs4240157 and rs233575). The minor alleles of these four SNPs were associated with higher left ventricular mass index (LVMI) and higher septal wall thickness (SWT) in men. Likewise, male carriers of a common haplotype (frequency 29.9%) consisting of the minor alleles of these four SNPs displayed higher values for LVMI and SWT than non-carriers (LVMI: TGGC 98.8+/-1.52 vs non-TGGC 94.8+/-0.99 g/m(2), p=0.027; SWT: TGGC 11.5+/-0.14 vs non-TGGC 11.1+/-0.09 mm, p=0.019). Furthermore, this haplotype was associated with an increased odds ratio (OR) for left ventricular hypertrophy (OR 3.10, p=0.006). In women, similar but less pronounced and consistent trends were observed. No association was observed between any of these SNPs and parameters of left ventricular systolic or diastolic function nor with blood pressure levels. This study provides evidence that genetic variants in the ACE2 gene may be associated with left ventricular mass, SWT and left ventricular hypertrophy in hemizygous men.

Animal models of hypertension: an overview

Hypertension is a multifactorial disease involving complex interactions between genetic and environmental factors. Development of experimental models of hypertension allowed dissection and isolation of various factors associated with regulation of blood pressure, inheritance of hypertensive traits, and cellular responses to injury. The phenotype-driven approach is taking advantage of selective breeding of animals (primarily rats) that exhibit a desired phenotype, like the useful SHR. Genotype-driven models include transgenic techniques, in which mice are the most successful for selective deletion or overexpression of target genes. Notably, a combination of comparative genomics strategies and phenotypic correlates enhances the utility of hypertension models and their clinical relevance. Indeed, experimental models enabled development of targeted interventions aimed at decreasing not only blood pressure but also target organ injury. Continued utilization of experimental models simulating human hypertension, particularly those that combine other clinically relevant comorbidities like obesity or hypercholesterolemia, may afford development of effective strategies to address this common disease. Nevertheless, a cautious approach is mandatory when experimental findings in these models are extrapolated to human hypertension.

Different antioxidants status, total antioxidant power and free radicals in essential hypertension

Hypertension is a multi-factorial process, prevalent in developed as well as in developing countries. Different antioxidants and free radicals play an important role in cardiovascular system. In present study, total antioxidant power in terms of FRAP (ferric reducing activity of plasma), free radicals and different antioxidants have been studied in essential hypertensives (n = 50) and normal subjects (n = 50). Levels of total cholesterol, low-density lipids-cholesterol, malonialdehyde, very low-density lipids (VLDL), uric acid, plasma homocysteine and low-density lipids (LDL), were significantly higher in hypertensives as compared to normotensive. HDL-cholesterol, SOD, GPx, reduced glutahione, total glutathione, oxidized glutathione, total thiols, protein thiols, non protein thiols, RNI, total antioxidant power, vitamin A, ascorbic acid and glutahione-S-transferase (GST) were decreased significantly in normotensive. We observed significantly low nitric oxide levels in hypertensive patients. No correlation was observed between severity of disease and plasma nitric oxide levels. There was a significant decrease in plasma FRAP value in essential hypertensives as compared to normotensive controls, which showed a negative correlation with diastolic blood pressure. In conclusion, our study revealed that there was a consistent significant difference between essential hypertensives versus controls with respect to most of the parameters. These complex changes are consistent in the view that essential hypertension is associated with an abnormal level of antioxidant status compared to normal response to oxidative stress or both.

Deletion polymorphism in the gene for angiotensin-converting enzyme is associated with essential hypertension in men born during the Pacific War

Age is a strong risk factor for hypertension in relation to vascular aging. Additional etiological factors include: lifestyle, genetic factors, and their interactions. The aim of this study is to examine whether an insertion/deletion (I/D) polymorphism in the angiotensin-converting enzyme (ACE) gene is associated with essential hypertension in Korean born during the Pacific War. A total of 13,914 healthy subjects (8261 men, 5653 women) aged 20-79 years were examined. Subjects with abnormal renal, thyroid dysfunction, or electrolyte levels were excluded. Logistic regression analysis showed increased risk (OR=1.15; 95% CI, 1.01-1.31) in men, but not in women (OR, 1.06; 95% CI, 0.89-1.26). However, after adjustment for age, obesity, cholesterol, alcohol consumption, and diabetes mellitus, increased risk in men was not significant (OR, 1.13; 95% CI, 0.98-1.42). Analyzed according to birth-year, DD genotype showed increased risk for hypertension in only a subgroup of men (adjusted OR, 1.56; 95% CI, 1.16-2.09; p = 0.001), born during the Pacific War (1941-1945 year). Findings suggest that the ACE DD genotype plays a role in the pathogenesis of essential hypertension, in conjunction with adverse environmental conditions in early life, with sex-related difference.

Angiotensin-converting enzyme (ACE) haplotypes and cyclosporine A (CsA) response: a model of the complex relationship between ACE quantitative trait locus and pathological phenotypes

It is highly controversial to define the role of angiotensin-converting enzyme (ACE) polymorphisms in essential hypertension. We studied a group of patients in whom hypertension was the major side effect of treatment by cyclosporine A (CsA). This study group comprised 227 Italian patients with nephrotic syndrome, 103 of which were treated with CsA and had different outcome. Forty-nine patients developed serious hypertension that was reversed after withdrawal of drug. ACE haplotypes were determined by a combination of molecular and statistical methods after verifying genotypes of six intragenic single nucleotide polymorphisms in 304 Italian blood donors and assembling them in clades (A, B, C) that include 95% of observed haplotypes. The association between ACE clade combinations and serum enzymatic levels confirmed the previous results about a role of an unidentified genetic variant at the 5' of the intragenic recombination site located near intron 7. ACE clades were then determined in patients, and regression methods were used to analyze variables associated with CsA responsivity and progression to renal failure. ACE genotype and responsiveness to CsA were strictly associated, because homozygosis for ACE B clade was able to influence CsA sensitivity. This highlights the role of 5' variants, which differentiate clades B and C. Other genetic markers were tested to search for possible additive effects. We found that PAI-1 4G allele was associated with progression to renal failure in the group of CsA-treated patients. Our results are in agreement with the hypothesis, raised after experimental results obtained in mouse models, that the effect of ACE polymorphisms on blood pressure is detectable once environmental factors, like CsA treatment in our case, overcome physiological homeostatic mechanisms.

Gene markers and antihypertensive therapy

Increasingly, detailed characterization of human molecular genetic variation will facilitate the use of genetic information in preventing, diagnosing, and treating common diseases. One promising application is the identification of genetic variants influencing responses to drugs used to lower blood pressure (BP) and prevent target-organ complications of hypertension. This update on gene markers to guide antihypertensive therapy highlights polymorphisms recently reported to predict interindividual differences in response to antihypertensive medications. However, single-site variation in most genes makes only a small contribution to differences in BP response, and, after all known genetic and environmental predictors have been considered, most variation in responses still remains unexplained. Advancing beyond our current "trial-and-error" approach to selecting drug therapy in individual patients will undoubtedly require whole-genome approaches to discover additional, novel genetic pathways influencing drug response. In addition, larger samples will be required to more fully characterize genetic variation within candidate genes and to consider the joint effects of gene-gene and gene-environment interactions. Eventually, knowledge of genetic variants that influence BP responses may allow more individualized tailoring of therapy to optimally reduce BP and target-organ damage.