Angiotensin-converting enzyme gene polymorphism and common carotid stiffness. The Rotterdam study

A Review of Vascular Traits and Assessment Techniques, and Their Heritability

Various tools are available to assess atherosclerosis, arterial stiffening, and endothelial function. They offer utility in the assessment of hypertensive phenotypes, in cardiovascular risk prediction, and as surrogate endpoints in clinical trials. We explore the relative influence of participant genetics, with reference to large-scale genomic studies, population-based cohorts, and candidate gene studies. We find heritability estimates highest for carotid intima-media thickness (CIMT 35–65%), followed by pulse wave velocity as a measure of arterial stiffness (26–43%), and flow mediated dilatation as a surrogate for endothelial function (14–39%); data were lacking for peripheral artery tonometry. We furthermore examine genes and polymorphisms relevant to each technique. We conclude that CIMT and pulse wave velocity dominate the existing evidence base, with fewer published genomic linkages for measures of endothelial function. We finally make recommendations regarding planning and reporting of data relating to vascular assessment techniques, particularly when genomic data are also available, to facilitate integration of these tools into cardiovascular disease research.

Age differences in arterial and venous extra-cerebral blood flow in healthy adults: contributions of vascular risk factors and genetic variants

Sufficient cerebral blood flow (CBF) and venous drainage are critical for normal brain function, and their alterations can affect brain aging. However, to date, most studies focused on arterial CBF (inflow) with little attention paid to the age differences in venous outflow. We measured extra-cerebral arterial and venous blood flow rates with phase-contrast MRI and assessed the influence of vascular risk factors and genetic polymorphisms (ACE insertion/deletion, COMT val158met, and APOEε4) in 73 adults (age 18-74 years). Advanced age, elevated vascular risk, ACE Deletion, and COMT met alleles were linked to lower in- and outflow, with no effects of APOE ε4 noted. Lower age-related CBF rate was unrelated to brain volume and was observed only in val homozygotes of COMTval158met. Thus, in a disease-free population, age differences in CBF may be notable only in persons with high vascular risk and carriers of genetic variants associated with vasoconstriction and lower dopamine availability. It remains to be established if treatments targeting alleviation of the mutable factors can improve the course of cerebrovascular aging in spite of the immutable genetic influence.

Gene Polymorphisms of Angiotensin II Type 1 Receptor and Angiotensin-Converting Enzyme in Two Ethnic Groups Living in Zhejiang Province, China

Polymorphisms of ACE insertion/deletion (I/D) and angiotensin II type 1 receptor (AT1R) 1166A-C have been associated with many diseases, and distributions of their genotypes vary in different races and populations. The aim of this study was to investigate distributions of angiotensin-converting enzyme (ACE) and AT1R genotypes in Han and She populations in ZheJiang province. We determined ACE and AT1R genotypes in 189 Han and 163 She individuals. DNA was extracted from peripheral blood samples. Analyses of ACE and AT 1R genotypes were performed by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP). The frequencies of ACE genotypes and alleles among the Han sample (41.3%II, 41.3%ID, 17.5%DD; 61.9%I allele, 38.1%D allele) were similar to those among She individuals (39.9%II, 39.3%ID, 20.9%DD; 59.5%I allele, 40.5%D allele), with p=0.660; p=0.421. However, significant differences in the distributions of ACE polymorphism between men and women among She population were observed, with p=0.042, p=0.014. AT1R genotype and allele frequencies in the Han population were (88.4%AA, 11.1%AC, 0.5%CC) and (93.9%A allele, 6.1%C) allele respectively. In the She population they were (78.0%AA, 21.3%AC, 0.6%CC) and (89.0%A allele, 11.0%C allele). The significant differences were found between Han and She populations with p=0.031, p=0.018, and within subgroups of women, with p=0.010, p=0.021. There were no significant differences within subgroups of men (p=0.476, p=0.261). The genotype distributions or allele frequencies of ACE and AT1R were significantly different between the samples of the She and Han populations.

Genetic determinants of arterial stiffness

Stiffness of large arteries (called arteriosclerosis) is an independent predictor of cardiovascular morbidity and mortality. Although previous studies have shown that arterial stiffness is moderately heritable, genetic factors contributing to arterial stiffness are largely unknown. In this paper, we reviewed the available literature on genetic variants that are potentially related to arterial stiffness. Most variants have shown mixed depictions of their association with arterial stiffness across multiple studies. Various methods to measure arterial stiffness at different arterial sites can contribute to these inconsistent results. In addition, studies in patient populations with hypertension or atherosclerosis may overestimate the impact of genetic variants on arterial stiffness. Future studies are recommended to standardize current measures of arterial stiffness in different age groups. Studies conducted in normal healthy subjects may also provide better opportunities to find novel genetic variants of arterial stiffness.

Ventricular-vascular coupling in hypertension: methodological considerations and clinical implications

The present review is addressed to analyse the complex interplay between left ventricle and arterial tree in hypertension. The different methodological approaches to the analysis of ventricular vascular coupling in the time and frequency domain are discussed. Moreover, the role of hypertension-related changes of arterial structure and function (stiffness and wave reflection) on arterial load and how ventricular-vascular coupling modulates the process of left ventricular adaptation to hypertension are analysed.The different interplay between vascular bed and left ventricle emerges as the pathophysiological basis for the development of the multiple patterns of ventricular structural adaptation in hypertension and provides a pathway for the interpretation of systolic and diastolic functional abnormalities observed in hypertensive patients. Targeting the therapeutic approach to improve ventricular-vascular coupling may have relevant impact on reversing left ventricular hypertrophy and improving systolic and diastolic dysfunction.

The association of maternal ACE A11860G with small for gestational age babies is modulated by the environment and by fetal sex: a multicentre prospective case-control study

We aimed to determine whether the ACE A11860G genotype is associated with small for gestational age babies (SGA) and to determine whether the association is affected by environmental factors and fetal sex. Overall, 3234 healthy nulliparous women with singleton pregnancies, their partners and babies were prospectively recruited in Adelaide, Australia and Auckland, New Zealand. Data analyses were confined to 2121 Caucasian parent–infant trios, among which 216 were pregnancies with SGA infants and 1185 were uncomplicated pregnancies. Women with the ACE A11860G GG genotype in the combined and Adelaide cohorts had increased risk for SGA [odds ratios (OR) 1.5, 95% confidence interval (CI) 1.1–2.1 and OR 2.0, 95% CI 1.3–3.3, respectively) and delivered lighter babies (P = 0.02; P = 0.007, respectively) compared with those with AA/AG genotypes. The maternal ACE A11860G GG genotype was associated with higher maternal plasma ACE concentration at 15 weeks' gestation than AA/AG genotypes (P < 0.001). When the Adelaide cohort was stratified by maternal socio-economic index (SEI) and pre-pregnancy green leafy vegetable intake, the ACE A11860G GG genotype was only associated with an increased risk for SGA (OR 4.9, 95% CI 1.8–13.4 and OR 3.3, 95% CI 1.6–7.0, respectively) and a reduction in customized birthweight centile (P = 0.006 and P = 0.03) if superimposed on maternal SEI <34 or pre-pregnancy green leafy vegetable intake <1 serve/day. Furthermore, the associations of maternal ACE A11860G with customized birthweight centile observed among Adelaide women with SEI <34 or pre-pregnancy green leafy vegetable intake <1 serve/day were female specific. The current study identified a novel association of maternal ACE A11860G with SGA. More interestingly, this association was modified by environmental factors and fetal sex, suggesting ACE A11860G–environment–fetal sex interactions.

Trial Registry Name: Screening nulliparous women to identify the combinations of clinical risk factors and/or biomarkers required to predict pre-eclampsia, SGA babies and spontaneous preterm birth.

URL: http://www.anzctr.org.au.

Registration number: ACTRN12607000551493.

A review of genetics, arterial stiffness, and blood pressure in African Americans

The prevalence of hypertension in African Americans in the USA is among the highest in the world and increasing. The identification of genes and pathways regulating blood pressure in African Americans has been challenging. An early predictor of hypertension is arterial stiffness. The prevalence of arterial stiffness is significantly higher in African Americans compared to Caucasians. Approximately 20 % of the variance in arterial stiffness is estimated to be heritable. Identifying genes and biological pathways regulating arterial stiffness may provide insight into the genetics underlying the increased risk of hypertension in African Americans. This paper reviews the genetic findings to date in the area of arterial stiffness and blood pressure in African Americans with an emphasis on the current limitations and new efforts to move the field forward.

Association between polymorphisms of the renin angiotensin system and carotid stenosis

OBJECTIVE

Carotid stenosis is a common manifestation of systemic atherosclerosis. Apart from traditional risk factors, genetic determinants, such as polymorphisms of the renin angiotensin system (RAS), may be relevant in modulating the atherosclerotic process leading to carotid stenosis. In this study, we investigated the role of angiotensin-converting enzyme (ACE) I/D and -240A>T, angiotensinogen (AGT) M235T, and angiotensin type 1 receptor (AGTR1) 1166A > C polymorphisms in modulating the susceptibility to the disease.

METHODS

Eight hundred twenty-one consecutive patients with severe carotid stenosis (≥70%) and 847 control subjects were investigated.

RESULTS

A significant difference in genotype distribution (P < .0001) and allele frequency (P < .0001) between patients and controls for the ACE I/D polymorphism, but not for the other single-nucleotide polymorphisms investigated, was observed. The ACE D allele frequency was significantly higher in patients without traditional risk factors in comparison with that observed in those with at least one risk factor (0.71 vs 0.61; P = .04). The ACE D allele significantly influenced carotid stenosis under dominant, recessive, and additive model of inheritance at both univariate (P < .0001) and multivariate analysis (P < .0001). When the combined effect of RAS unfavorable alleles was considered, patients carrying less than three alleles had a lower risk of carotid stenosis (odds ratio [OR], 0.79 [0.63-0.99]; P = .05), while carriers of more than four unfavorable alleles had an increased risk (OR, 1.44 [1.12-1.84]; P = .004), in comparison with subjects carrying three or four unfavorable alleles. ACE D allele frequency was similar in patients with and without additional atherosclerotic localizations (0.61 vs 0.62, respectively).

CONCLUSIONS

Our findings evidence a role for ACE I/D polymorphism in influencing the susceptibility to carotid stenosis, even in the absence of traditional risk factors. Interestingly, our findings provided further information concerning the role of this polymorphism in modulating the atherosclerotic process apart from its different localizations.

Effects of age, genes, and pulse pressure on executive functions in healthy adults

Executive functions (EF) evidence significant age-related declines, but the mechanisms underpinning those changes are unclear. In this study, we focus on two potential sources of variation: a physiological indicator of vascular health, and genetic variants related to vascular functions. In a sample of healthy adults (n=158, ages 18-81), we examine the effects of age, pulse pressure, and two polymorphisms (comt val158met and ace insertion/deletion) on working memory and cognitive flexibility. Results indicate that in addition to often-replicated age differences, the alleles of two polymorphisms that promote vasoconstriction (comt val and ace D) and reduced availability of dopamine in neocortical synapses (comt val), negatively impact virtually all aspects of EF tasks that involve working memory. In some cases, suppression of cognitive performance is limited to men or necessitates a combination of both risk-associated alleles. After accounting for genetic and age-related variation, pulse pressure had no additional effect on EF. These findings suggest that in healthy adults, the effects of genetic risk factors significantly modulate the course of cognitive aging.

Impaired abdominal aortic wall integrity in elderly men carrying the angiotensin-converting enzyme D allele

OBJECTIVE

A polymorphism in the angiotensin-converting-enzyme gene (ACE I/D) has been associated with abdominal aortic aneurysm and a link between aortic aneurysm and aortic stiffness has been suggested. This study aimed to explore the links between ACE I/D polymorphism, circulating ACE and abdominal aortic wall integrity as reflected by abdominal aortic wall stiffness.

MATERIAL

A total of 212 men and 194 women, aged 70-88 years, were studied.

METHODS

Mechanical properties of the abdominal aorta were determined using the Wall Track System, ACE genotype using the polymerase chain reaction (PCR) and circulating ACE level by enzyme-linked immunosorbent assay (ELISA).

RESULTS

In men, pulsatile diameter change differed between genotypes (II 0.70, ID 0.55 and DD 0.60 mm, P = 0.048), whereas a tendency was seen for distensibility coefficient (DC) (II 10.38, ID 7.68 and ID 8.79, P = 0.058). Using a dominant model (II vs. ID/DD), men carrying the ACE D allele had lower pulsatile diameter change (P = 0.014) and DC (P = 0.017) than II carriers. Multiple regression analyses showed additional associations between the D allele and increased stiffness β, and reduced compliance coefficient.

CONCLUSION

Men carrying the ACE D allele have stiffer abdominal aortas compared with II carriers. Deranged abdominal aortic stiffness indicates impaired vessel wall integrity, which, along with other local predisposing factors, may be important in aneurysmal disease.

Preliminary studies on human aldosterone synthase (CYP11B2) gene polymorphism, matrix metalloprotease-9, apoptosis, and carotid atherosclerosis plaque size by proton magnetic resonance imaging

Hypothesis. Aldosterone has direct or indirect effects on atherosclerosis, and polymorphisms occur in the gene encoding aldosterone synthase (CYP11B2), the enzyme catalysing aldosterone biosynthesis. Genetic variations in aldosterone synthesis may influence progression of carotid atherosclerosis.

Materials and methods. Ten subjects were genotyped through the use of the polymerase chain reaction for two diallelic polymorphisms in CYP11B2: one in the transcriptional regulatory region (promotor) and the other in the second intron. In vivo plaque size was estimated by H-1 magnetic resonance imaging using gradient echo pulse sequence. Media-intima thickness and ex vivo plaque in endarterectomy samples were measured by histology. Matrix metalloprotease (MMP)-9 was stained in endarterectomy histology sections and apoptosis index was counted in these sections.

Results. The CYP11B2 promoter genotype patterns were associated significantly with the plaque size in carotid artery (r2=0.9987; p=0.001), MMP-9 levels (r 2=0.9878; p=0.0001) and apoptotic indices (r2=0.9495; p=0.005) by multiple regression analysis. The media-intima thickness was not significantly correlated with genotype patterns.

Conclusion. Genetic variations in aldosterone synthase (CYP11B2) gene are associated with the progression of atherosclerotic plaque size, MMP-9 and apoptosis in the carotid artery.

Genetic variation in the renin-angiotensin system and arterial stiffness. The Rotterdam Study

We studied the associations of three renin-angiotensin system polymorphisms, angiotensin-converting enzyme (ACE) I/D, angiotensinogen 235 M/T, and angiotensin II receptor type I 573 C/T, with arterial stiffness. The study was embedded in the Rotterdam Study, a population-based study older adults. The association of the polymorphisms with pulse wave velocity, the carotid distensibility, and pulse pressure was investigated in 3706 subjects. We found no association of the ACE I/D polymorphism with pulse wave velocity, but the D-allele was associated with a lower distensibility coefficient (p = 0.05) and higher pulse pressure (p = 0.01). For the angiotensinogen 235 M/T polymorphism, no significant associations with either pulse wave velocity (p = 0.71), the distensibility coefficient (p = 0.16) or pulse pressure (p = 0.34) were found. Also, we found no significant associations of pulse wave velocity (PWV) (p = 0.32), the distensibility coefficient (p = 0.08), and pulse pressure (p = 0.09) with the angiotensin II receptor type 1 573 C/T polymorphism. No epistatic effects were observed between the three renin-angiotensin system (RAS) genes with arterial stiffness. Our findings suggest that genetic variation in the renin-angiotensin system may play a role in determining carotid distensibility and pulse pressure.

Benefits of the RAS blockade: clinical evidence before the ONTARGET study

Activation of the AT1 angiotensin II (Ang II) receptors has various effects including vasoconstriction, hypertrophy, and possibly hyperplasia of vascular smooth muscle cells and cardiomyocytes and increase in extracellular collagen matrix synthesis. These actions lead to the development of cardiovascular hypertrophy and fibrosis, as well as arterial stiffness, which are some key factors in the development of the cardiovascular and renal complications. In clinical studies, it has been shown that renin-angiotensin blockade has direct and specific implications in the evolution of heart failure, coronary disease, stroke, and hypertensive and diabetic renal disease. The beneficial cardiovascular and renal effects of blocking the renin-angiotensin-aldosterone system reported in numerous clinical trials may be at least partially related to the actions of these drugs on cardiovascular and renal fibrosis, and arterial stiffness. These effects are now well-established and lead the international medical societies to propose the use of the renin-angiotensin system (RAS) blockers as initial treatment (both angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers) in several cardiovascular, metabolic, and renal disorders such as hypertension, heart failure, and proteinuria.

Insertion/deletion polymorphism of angiotensin converting enzyme gene in Korean hypertensive adolescents

The essential role of the renin-angiotensin system (RAS) in controlling blood pressure has been well established. Genes encoding components of the RAS have been proposed as candidate genes that determine genetic predisposition to hypertension and the risk of developing cardiovascular complications. The purpose of this study was to analyze angiotensin-converting enzyme (ACE) insertion/deletion (I/D) polymorphisms in Korean hypertensive adolescents, and to determine the association between ACE genotype and cardiovascular risk. Forty hypertensive adolescents (16-17 years old, systolic blood pressure (BP) > or =140 mm Hg and/or diastolic BP > or =90 mm Hg) and a control group of twenty normotensive adolescents were included in the study. Obesity index (OI) and body mass index (BMI) were calculated. Skin fold thickness and arm circumference were also measured. Fat mass and fat distribution were analyzed by bioelectrical impedance. Blood pressure was measured at resting state by oscillometric methods. Serum aldosterone, renin, insulin, ACE, homocysteine, vitamin B12, and folate levels were evaluated after a fasting period of 12 h. The carotid intima-media thickness (IMT) and carotid artery diameter were measured by carotid ultrasound. Pulse wave velocity (PWV) and ankle-brachial index (ABI) were also measured. Polymerase chain reaction (PCR) was conducted to amplify DNA from blood samples of each individuals to analyze ACE I/D polymorphism. Genotype frequencies of I/I were 37.5%, I/D 45.0% and D/D 17.5%. Serum ACE levels were 33.5 +/- 8.7 U/l in I/I genotype, 48.6 +/- 19.8 U/l in I/D genotype and 61.4 +/- 22.7 U/l in D/D genotype, which showed that ACE levels were significantly higher in those with D/D or I/D genotype than in I/I genotype. Carotid IMT was significantly greater in D/D group than in I/I group. In conclusion, the D allele is associated with the increased level of ACE in Korean hypertensive adolescents.

Prevalence of the angiotensin I converting enzyme gene insertion/deletion polymorphism in a healthy Turkish population

Angiotensin converting enzyme (ACE) plays an essential role in the renin-angiotensin system. It converts angiotensin I to angiotensin II and inactivates bradykinin and tachykinins. Numerous studies have been published investigating associations of the ACE gene I/D polymorphism with various pathophysiological conditions. We examined the prevalence of the ACE I/D polymorphism in a sample of healthy volunteers from western Turkey, including 1063 healthy Turkish controls. Analysis of the ACE I/D gene polymorphisms by polymerase chain reaction found frequencies of 16.1% for the II genotype, 47.7% for the ID genotype, and 36.2% for the DD genotype. The allele frequency was 39.9% for the I alleles and 60.1% for the D allele. This study demonstrates that the allele and genotype frequency values for the Turkish population are similar to previously published frequencies for Caucasian populations.

Multimarker approach to evaluate correlates of vascular stiffness: the Framingham Heart Study

BACKGROUND

Arterial stiffness increases with age and contributes to the pathogenesis of systolic hypertension and cardiovascular disease in the elderly. Knowledge about the pathophysiological processes that determine arterial stiffness may help guide therapeutic approaches.

METHODS AND RESULTS

We related 7 circulating biomarkers representing distinct biological pathways (C-reactive protein, aldosterone-to-renin ratio, N-terminal proatrial natriuretic peptide and B-type natriuretic peptide, plasminogen activator inhibitor-1, fibrinogen, and homocysteine) to 5 vascular function measures (central pulse pressure, carotid-femoral pulse-wave velocity, mean arterial pressure, forward pressure wave amplitude [all measures of conduit artery stiffness], and augmented pressure, an indicator of wave reflection) in 2000 Framingham Offspring Study participants (mean age, 61 years; 55% women). Tonometry measures were obtained on average 3 years after the biomarkers were measured. In multivariable linear regression models adjusting for covariates, the biomarker panel was significantly associated with all 5 vascular measures (P<0.003 for all). On backward elimination, the aldosterone-to-renin ratio was positively associated with each stiffness measure (P< or =0.002 for all). In addition, C-reactive protein was positively related to augmented pressure (P=0.0003), whereas plasminogen activator inhibitor-1 was positively associated with mean arterial pressure (P=0.003), central pulse pressure (P=0.001), and forward pressure wave (P=0.01).

CONCLUSIONS

Our cross-sectional data on a community-based sample suggest a distinctive pattern of positive associations of biomarkers of renin-angiotensin-aldosterone system activation with pan-arterial vascular stiffness, plasminogen activator inhibitor-1 with central vascular stiffness indices, and C-reactive protein with wave reflection. These observations support the notion of differential influences of biological pathways on vascular stiffness measures.

Novel measures of cardiovascular health and its association with prevalence and progression of age-related macular degeneration: the CHARM Study

Background

To determine if novel measures of cardiovascular health are associated with prevalence or progression of age-related macular degeneration (AMD).

Methods

Measures of the cardiovascular system: included intima media thickness (IMT), pulse wave velocity (PWV), systemic arterial compliance (SAC), carotid augmentation index (AI). For the prevalence study, hospital-based AMD cases and population-based age- and gender-matched controls with no signs of AMD in either eye were enrolled. For the progression component, participants with early AMD were recruited from two previous studies; cases were defined as progression in one or both eyes and controls were defined as no progression in either eye.

Results

160 cases and 160 controls were included in the prevalence component. The upper two quartiles of SAC, implying good cardiovascular health, were significantly associated with increased risk of AMD (OR = 2.54, 95% CL = 1.29, 4.99). High PWV was associated with increased prevalent AMD. Progression was observed in 82 (32.3%) of the 254 subjects recruited for the progression component. Higher AI (worse cardiovascular function) was protective for AMD progression (OR = 0.30, 95%CL = 0.13, 0.69). Higher aortic PWV was associated with increased risk of AMD progression; the highest risk was seen with the second lowest velocity (OR = 6.22, 95% CL = 2.35, 16.46).

Conclusion

The results were unexpected in that better cardiovascular health was associated with increased risk of prevalent AMD and progression. Inconsistent findings between the prevalence and progression components could be due to truly different disease etiologies or to spurious findings, as can occur with inherent biases in case control studies of prevalence. Further investigation of these non-invasive methods of characterizing the cardiovascular system should be undertaken as they may help to further elucidate the role of the cardiovascular system in the etiology of prevalent AMD and progression.

Screening the Single Nucleotide Polymorphisms in Patients with Internal Carotid Artery Stenosis by Oligonucleotide-Based Custom DNA Array

Early screening of individuals considered to be at risk for severe internal carotid artery (ICA) stenosis is an important strategy for preventing ischemic cerebral stroke. The purpose of this study is to screening candidate single nucleotide polymorphisms (SNPs) associated with severe ICA stenosis using a newly developed oligonucleotide-based custom DNA array. The subjects consisted of 47 controls and 46 patients with severe ICA stenosis (≥70%) who underwent carotid endarterectomy (CEA). Subjects gave informed consent and we obtained samples of blood and genomic DNA. We studied 8 candidate genes: renin-angiotensin system [angiotensinogen (AGT), angiotensin II receptor type 1 (AGTR1), nitric oxide synthase 3 (NOS3)]; growth factor [hepatocyte growth factor (HGF)]; transgelin (SM22); cytokine [chemokine receptor 2 (CCR2)]; coagulation-fibrinolysis system [5,10-methylenetetrahydrofolate reductase (MTHFR)]; and plasminogen activator inhibitor 1 (PAI-1). Genotyping of candidate SNPs was done with a line probe assay (LiPA) based on an oligonucleotide-based DNA array. Results: The allele frequency of PAI-1 -1965 delG (odds ratio (OR), 0.3; 95% confidence interval (CI), 0.2–0.6) and MTHFR (OR 1.3, 95% CI, 1.0–1.5) were significantly different between controls and cases with ICA stenosis by Fisher's exact test. Multiple logistic analysis revealed that diabetes mellitus (DM), SNPs in PAI-1 -1965 delG and MTHFR were an independent risk for ICA stenosis. In conclusion, genetic factors of coagulation-fibrinolysis as well as diabetes mellitus (DM) were relevant in ICA stenosis.

Genetic markers of vascular aging

Age is a powerful determinant of cardiovascular risk, being associated with a number of deleterious changes in the cardiovascular system. Increased arterial stiffness is an almost ubiquitous accompaniment of aging. However, there is significant variability in age-related arterial changes between individuals likely due, in part, to genetic factors. Measures of arterial stiffness such as pulse pressure and aortic pulse wave velocity have been shown to be heritable, indicating that genetic factors play a role in the interindividual variation of these phenotypes. Linkage analyses in related individuals have identified several genomic regions that may influence measures of arterial stiffness, and numerous association studies have investigated whether polymorphisms in candidate genes are related to this phenotype. Genome-wide association studies using 500,000 single nucleotide polymorphisms or more are now feasible and will accelerate the discovery of specific genetic polymorphisms that influence vascular aging/stiffness. Such findings will facilitate the development of novel therapies to retard vascular aging.

Long-term trandolapril treatment is associated with reduced aortic stiffness: the prevention of events with angiotensin-converting enzyme inhibition hemodynamic substudy

The Prevention of Events with Angiotensin Converting Enzyme inhibition (PEACE) trial evaluated angiotensin-converting enzyme inhibition with trandolapril versus placebo added to conventional therapy in patients with stable coronary disease and preserved left ventricular function. The PEACE hemodynamic substudy evaluated effects of trandolapril on pulsatile hemodynamics. Hemodynamic studies were performed in 300 participants from 5 PEACE centers a median of 52 months (range, 25 to 80 months) after random assignment to trandolapril at a target dose of 4 mg per day or placebo. Central pulsatile hemodynamics and carotid-femoral pulse wave velocity were assessed by using echocardiography, tonometry of the carotid and femoral arteries, and body surface transit distances. Patients randomly assigned to trandolapril tended to be older (mean+/-SD: 64.2+/-7.9 versus 62.9+/-7.7 years; P=0.14), with a higher body mass index (28.5+/-4.0 versus 27.8+/-3.9 kg/m(2); P=0.09) and lower ejection fraction (57.1+/-8.1% versus 58.7+/-8.4%; P<0.01). At the time of the hemodynamic substudy, the trandolapril group had lower mean arterial pressure (93.1+/-10.2 versus 96.3+/-11.3 mm Hg; P<0.01) and lower carotid-femoral pulse wave velocity (geometric mean [95% CI]: 10.4 m/s [10.0 to 10.9 m/s] versus 11.2 m/s [10.7 to 11.8 m/s]; P=0.02). The difference in carotid-femoral pulse wave velocity persisted (P<0.01) in an analysis that adjusted for baseline characteristics and follow-up mean pressure. In contrast, there was no difference in aortic compliance, characteristic impedance, augmentation index, or total arterial compliance. Angiotensin-converting enzyme inhibition with trandolapril produced a modest reduction in carotid-femoral pulse wave velocity, a measure of aortic wall stiffness, beyond what would be expected from blood pressure lowering or differences in baseline characteristics alone.

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.

The genetic basis for altered blood vessel function in disease: large artery stiffening

The progressive stiffening of the large arteries in humans that occurs during aging constitutes a potential risk factor for increased cardiovascular morbidity and mortality, and is accompanied by an elevation in systolic blood pressure and pulse pressure. While the underlying basis for these changes remains to be fully elucidated, factors that are able to influence the structure and composition of the extracellular matrix and the way it interacts with arterial smooth muscle cells could profoundly affect the properties of the large arteries. Thus, while age and sex represent important factors contributing to large artery stiffening, the variation in growth-stimulating factors and those that modulate extracellular production and homeostasis are also being increasingly recognized to play a key role in the process. Therefore, elucidating the contribution that genetic variation makes to large artery stiffening could ultimately provide the basis for clinical strategies designed to regulate the process for therapeutic benefit.

Angiotensin converting enzyme gene polymorphism and cardiovascular morbidity and mortality: the Rotterdam Study

BACKGROUND

Findings on the association between the insertion/deletion (I/D) polymorphism of the angiotensin I-converting enzyme (ACE) gene and cardiovascular morbidity and mortality have been inconsistent. Considering the possible interaction between this polymorphism and smoking, we evaluated the association between ACE I/D polymorphism and myocardial infarction (MI), mortality due to coronary heart disease (CHD), and cardiovascular disease (CVD).

METHODS

The study was performed within the Rotterdam Study, a population based cohort study. The ACE I/D polymorphism was determined for 6714 participants and smoking status recorded at baseline. Fatal and non-fatal MIs and mortality events were regularly recorded. Cox proportional hazard analysis was performed separately for current smokers and non-smokers. We used age as the follow up time, presenting age specific survivals.

RESULTS

During follow up, 248 MIs and 301 and 482 deaths, respectively, due to CHD and CVD occurred. There were no significant differences between the genotypes as regards MI incidence. Among smokers, there was an increased risk of CHD and CVD mortality in carriers of the DD genotype compared to the II genotype, which diminished at later ages (p<0.01 for gene-age interaction). Subgroup analysis in a younger and older group (based on the median age of 68.2 years) showed a significantly increased risk of CVD mortality in the younger group (hazard ratio = 5.19; 95% confidence interval: 1.15 to 23.42).

CONCLUSIONS

This study showed that the ACE I/D polymorphism is not a strong risk factor for MI but its interaction with smoking might play a role in cardiovascular mortality especially at younger ages.

Functional genomics in hypertension

PURPOSE OF REVIEW

Essential hypertension is a complex polygenetic disease with a major impact on health worldwide. Despite earlier detection of promising candidate genes, only recent advances in genotyping technology and new approaches to examining gene and protein function have provided the tools to unravel the genetic basis of hypertension.

RECENT FINDINGS

In humans, genome-wide scans resulted in the identification of several chromosomal loci that are linked to hypertension. These regions still contain a large number of potential candidate genes, but high-throughput genotyping methods will facilitate the detection and analysis of single-nucleotide polymorphisms within these genes. The focus will be on animal models of hypertension, specifically rats. Congenic strains facilitate the identification of genetic determinants of hypertension, and new technologies such as RNA interference (which silences the expression of target genes) and transgenic rescue models will help us to analyse the relationship between genes and function. Analysis of conserved synteny (preserved order of genes) between species allows translation of findings from rodent models to essential hypertension in humans. Recent discoveries and approaches beyond genomics will also be discussed, including the regulatory role of microRNA and the concept of proteomics.

SUMMARY

The genetic basis of hypertension is complex, and the examination of the functional consequences of genetic variants in particular is still challenging. A number of tools are now available with which to examine gene-function relationships, and these will provide an improved understanding of cardiovascular genomics. This will eventually lead to targeted prevention and treatment strategies in patients with hypertension and other cardiovascular diseases.

Polymorphism of the angiotensin-converting enzyme (ACE) and angiotesinogen (AGT) genes and their associations with blood pressure and carotid artery intima media thickness among healthy Finnish young adults--the Cardiovascular Risk in Young Finns Study

The roles of angiotensin converting enzyme (ACE) insertion-deletion (I/D) and angiotensinogen (AGT) m235t polymorphisms in cardiovascular diseases have been investigated extensively during the past decade but results have been inconsistent. A sex-specific association between the ACE I/D polymorphism and systolic blood pressure (BP) was seen among Finnish children and adolescents previously. We investigated if these polymorphisms associate with the BP and carotid artery intima media thickness (IMT) in the same cohort during their adulthood. IMT data were available for 224 ACE I/D genotyped individuals and 202 AGT m235t genotyped individuals. Systolic and diastolic blood pressure values did not differ between ACE and AGT genotypes. Age and BMI adjusted mean IMT was 0.02 (95% CI: -0.05 to 0.02, p=0.33) and 0.03 mm (95% CI: -0.07 to 0.001, p=0.06) lower among the ID and DD genotype groups, respectively, compared to the II genotype group. MT and TT genotype groups had 0.02 mm (95% CI: -0.01 to 0.05, p=0.17) higher and 0.01 mm (95% CI: -0.04 to 0.02, p=0.59) lower mean IMT, respectively, compared to the MM genotype group. We conclude that ACE I/D and AGT m235t polymorphisms are not associated with carotid IMT in healthy young Finnish adults.

ACE I/D polymorphism is a risk factor of Alzheimer's disease but not of vascular dementia

Different studies have investigated the effect of the angiotensin converting enzyme (ACE) insertion/deletion (I/D) polymorphism on the risk of Alzheimer dementia (AD). However, results on the association of the ACE-I allele with AD have been inconclusive. A recent meta-analysis reported an association of the I-allele with the risk of AD. A few small studies also investigated the effect of ACE polymorphism on the risk of vascular dementia (VD). We have investigated the effect of ACE I/D polymorphism in 351 AD and 155 VD patients and 348 healthy controls. We found the I/I genotype to be associated with an increased risk of AD, but not with the risk of VD. Cell-specific effects of ACE polymorphism are suggested, additional studies on neuronal cells might help to understand the role of this polymorphism in AD.

Arterial stiffness and the renin-angiotensin-aldosterone system

Arterial stiffness has recently been recognised as an independent risk factor for cardiovascular morbidity and mortality in hypertension. Many of the complications seen with angiotensin II (Ang II) excess or hyperaldosteronism--an increased event rate, left ventricular hypertrophy, endothelial dysfunction and target organ damage--are also associated with arterial stiffness. It is possible that reduced arterial compliance may be one mechanism whereby increased activity of the renin-angiotensin-aldosterone system (RAAS) produces adverse vascular effects. Common pathophysiological processes, altered collagen turnover and increased fibrosis may underlie both arterial stiffness and RAAS-associated vascular damage. While it is recognised that patients with hyperaldosteronism have increased arterial stiffness, the role of the RAAS in modulating arterial compliance in essential hypertension and in normotensive subjects is less clear cut. There is, however, more consistent data which show that drugs that interfere with Ang II or aldosterone, namely angiotensin-converting enzyme (ACE) inhibitors, angiotensin receptor blockers (ARBs) and aldosterone antagonists, all reduce arterial stiffness. In many cases, this is to a greater extent than predicted from the extent of reduction in blood pressure (BP), suggesting a role for RAAS in vascular stiffness in hypertensive subjects. There is also evidence that combined ACE inhibitors (ACE-Is) and ARBs may have an additive effect in reducing stiffness. The reduction in cardiovascular mortality in end-stage renal disease patients treated with ACE-Is was preferentially seen in those who had reduced arterial stiffness. These data suggest that, in addition to regulation of vascular biology and BP, the RAAS is an important determinant of arterial stiffness in health and, more particularly, in disease.