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

Arterial Stiffness Parameters Correlate with Estimated Cardiovascular Risk in Humans: A Clinical Study

Arterial stiffness is said to be a novel predictor of cardiovascular events. This study investigated the correlation between arterial stiffness parameters and the estimated cardiovascular disease risk (RISK) in a Polish cohort of patients divided by age, sex, and body-mass index (BMI). The cross-sectional study enrolled 295 patients who met the inclusion criteria. Subjects were divided into three age groups, four weight groups, and by gender. The stiffness of the vessels was assessed by the measurement of the stiffness index (SI) and reflection index (RI). An individual 10-year RISK was calculated for each patient using the Heart Risk Calculator algorithm by the American Heart Association. A correlation between the SI and estimated RISK was observed (r_S 0.42, p < 0.05). The strongest relationship was presented for women, the age group 40–54, and individuals with normal weight. The correlation between RI and calculated RISK was observed (r_S 0.19, p < 0.05), the highest correlation was noticed for people aged 40–54 and obese. In conclusion, both SI and RI are correlated with estimated cardiovascular risk, however SI seems to be more useful than RI to predict the individual risk of future cardiovascular events. Both of these can be measured using non-invasive techniques, which demonstrates their potential utility in clinical practice.

The impacts of the interaction of genetic variation, CYP11β2 and NEDD4L, with sodium intake on pediatric obesity with gender difference: a 3-year panel study

Backgrounds/Objectives:This panel study was to predict the incidences of pediatric obesity by the interaction of sodium (Na) intake and nine single-nucleotide polymorphisms (SNPs) of salt-sensitive genes (SSGs), ACE(angiotensin-converting enzyme), ADD1 G460W,AGT M235T,CYP11β2 (cytochrome P450 family 11-subfamily β-2, -aldosterone synthase),GNB3 C285T,GRK4(A142V)(G-protein-coupled receptor kinases type 4),GRK4 (A486V),NEDD4L (neural precursor cell expressed developmentally downregulated 4 like; rs2288774) and SLC12A3 (solute carrier family 12 (Na/Cl transporters)-member 3), selected from genome-wide association study.

SUBJECTS/METHODS

Non-obese (non-OB) Korean children of 9 years old were recruited from eight elementary schools in Seoul in 2007 and 2009, each. Follow-up subjects (total=798) in 2010 and 2012 were final participants. Participants were classified as OB group for those whose body mass index were over the 85th percentile using the 'Korean National Growth Charts', and others were classified as non-OB. With nine SNPs typing, the genetic interaction with the variation of Na intake for 3 years was evaluated as an obesity risk.

RESULTS

The obesity incidence rate for non-OB children at baseline after 3 years was 10.31%. Na intake in non-OB after 3 years was significantly decreased compared with the baseline, whereas Na intake reduction was undetectable in OB. We found gender differences on association between the changes of Na intake and the obesity incidence for 3 years by the SSG variation. Odds ratio for the obesity risk was 5.75 times higher in girls having hetero/mutant types of NEDD4L with higher Na intakes (Q2+Q3+Q4 in quartiles) compared with that in the wild type with the lowest Na intake (Q1). Girls with hetero/mutant of CYP11β2 tended to increase the obesity incidence as Na intake increased (Q1<Q2<Q3<Q4, P-value trend=0.047). The other seven SNPs of SSGs had no significance over Na intake.

CONCLUSIONS

From this panel study and the previous cross-sectional study, we found CYP11β2 as the common gene, powerful to explain the interaction between obesity incidence and Na intake, in particular, among girls. Girls with hetero/mutant allele of this gene should reduce their daily Na intake to prevent obesity.

Aldosterone Synthase Promoter Polymorphism and Cardiovascular Phenotypes in a Large, Multiethnic Population-Based Study

BACKGROUND

A single-nucleotide polymorphism in the aldosterone synthase gene (CYP11B2) promoter [-344C/T, rs1799998] has been reported to associate with cardiovascular phenotypes.

METHODS

The Dallas Heart Study is a large, multiethnic cohort with a high prevalence of hypertension. We genotyped 3452 Dallas Heart Study participants for -344C/T. Generalized linear models were used to assess whether variation at -344C/T associated with plasma aldosterone concentration (PAC), systolic and diastolic blood pressure (SBP and DBP), plasma glucose (in persons with no diabetes), HOMA IR (Homeostasis Model Assessment as an Index of Insulin Resistance), and left ventricular (LV) mass indexed to height. Systolic blood pressure and DBP were significantly higher in blacks compared with whites (P < 0.001 for SBP and for DBP) and Hispanics (P < 0.001 for SBP and for DBP). Log-transformed body mass index was also significantly higher in blacks compared with whites (P < 0.001), but not Hispanics (P = 0.10). Log-transformed PAC was higher in whites compared with blacks (P < 0.001), but did not differ significantly in whites compared with Hispanics (P = 0.73). In univariate and multivariable analysis, -344C/T was not significantly associated with PAC within any ethnicity. In univariate and multivariable analysis, -344C/T was not associated with SBP or DBP within any ethnicity. After adjustment for multiple testing, univariate and multivariable analyses revealed no association between -344C/T and plasma glucose in patients with no diabetes, HOMA IR, or LV mass indexed to height.

CONCLUSIONS

We were unable to reproduce previously reported associations between -344C/T and PAC, blood pressure, plasma glucose, or LV mass. Methodological differences might explain the differences between our findings and those previously reported.

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.

Physical activity, vasomotor endothelial function, and arterial stiffness

Aim. To study the prevalence of selected parameters of subclinical atherosclerosis and their association with muscle function and muscle volume in patients with different levels of cardiovascular risk (CVR). Material and methods. The study included 20 patients (11 men and 9 women; mean age 54,5±8,5 years) with chronic coronary heart disease (CCHD; mean duration 6,4±2,3 years) in the main group (MG), as well as 20 CCHD-free people in the control group (CG). Arterial stiffness was assessed by pulse wave velocity (PWV) and calculated carotid-femoral index (CFI). Endothelial function was assessed by endothelium-dependent vasodilatation (EDVD) in the reactive hyperemia (RH) test. Common carotid artery (CCA) ultrasound was performed in order to assess intima-media thickness (IMT) of carotid arteries. All participants underwent veloergometry (VEM); exercise capacity (EC) was measured by calculated metabolic equivalents (MET). Muscle tissue volume was assessed using a bioelectrical impedance analyser. The percentage of active muscle mass (%AMM) and fat-free muscle mass (%FFM), out of the total body mass, was calculated. Results. Increased CFI values >12 m/s, as a marker of adverse prognosis, were observed in 20% CCHD patients and in 10% of controls (z=0,17; p=0,87). Vasomotor endothelial dysfunction (EDVD <10%) was registered in 65% and 50%, respectively (z=0,74; p=0,46), while increased IMT values >0,9 mm were observed in 55% and 15%, respectively (z=2,3; p=0,02). Most patients with pathologically increased arterial stiffness and vasomotor endothelial dysfunction had low EC. In CCHD patients with low EC, CFI significantly correlated with %AMM and %FFM (r=-0,32; p<0,05; and r=-0,36; p<0,05, respectively). EDVD significantly correlated with both %AMM and %FFM (r=0,47; p<0,05; and r=0,5; p<0,05, respectively). There was a significant correlation between CFI and EDVD (r=-0,3; p<0,05). In CG participants with low EC, EDVD correlated with %AMM and %FFM (r=0723; p<0,05 and r=0,7; p<0,05, respectively). In both groups, %AMM and %FFM correlated with MET (r=0,49; p<0,05 and r=0,55; p<0,05, respectively; r=0,34; p<0,05 and r=0,31; p<0,05, respectively). Conclusion. EDVD and PWV reflect the lower PA levels and functional disadaptation of CCHD patients, which can result in a faster progression of atherosclerosis.

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.

Arterial stiffness, central hemodynamics, and cardiovascular risk in hypertension

This review summarizes several scientific contributions at the recent Satellite Symposium of the European Society of Hypertension, held in Milan, Italy. Arterial stiffening and its hemodynamic consequences can be easily and reliably measured using a range of noninvasive techniques. However, like blood pressure (BP) measurements, arterial stiffness should be measured carefully under standardized patient conditions. Carotid-femoral pulse wave velocity has been proposed as the gold standard for arterial stiffness measurement and is a well recognized predictor of adverse cardiovascular outcome. Systolic BP and pulse pressure in the ascending aorta may be lower than pressures measured in the upper limb, especially in young individuals. A number of studies suggest closer correlation of end-organ damage with central BP than with peripheral BP, and central BP may provide additional prognostic information regarding cardiovascular risk. Moreover, BP-lowering drugs can have differential effects on central aortic pressures and hemodynamics compared with brachial BP. This may explain the greater beneficial effect provided by newer antihypertensive drugs beyond peripheral BP reduction. Although many methodological problems still hinder the wide clinical application of parameters of arterial stiffness, these will likely contribute to cardiovascular assessment and management in future clinical practice. Each of the abovementioned parameters reflects a different characteristic of the atherosclerotic process, involving functional and/or morphological changes in the vessel wall. Therefore, acquiring simultaneous measurements of different parameters of vascular function and structure could theoretically enhance the power to improve risk stratification. Continuous technological effort is necessary to refine our methods of investigation in order to detect early arterial abnormalities. Arterial stiffness and its consequences represent the great challenge of the twenty-first century for affluent countries, and "de-stiffening" will be the goal of the next decades.

Genetics and pathophysiology of arterial stiffness

Arterial stiffness is a cardiovascular risk factor that is independent of arterial pressure. Clinically, carotid-femoral pulse wave velocity (PWV) is the gold-standard parameter of arterial stiffness. Recent genetic studies have revealed specific genes that contribute to arterial stiffening. Here we review the recent findings on genome-wide linkage analyses and candidate gene polymorphism association studies. We also focus on the latest advances in the identification of gene variants affecting PWV using high density array single nucleotide polymorphism technology in a recent genome-wide association (GWA) study. Linkage and polymorphism studies revealed a first group of genes affecting the renin-angiotensin-aldosterone system, elastic fibre structural components, metalloproteinases, and the NO pathway. A second group of genes, identified by polymorphism association studies and possibly involved in the pathophysiology of arterial stiffness, includes beta-adrenergic receptors, endothelin receptors, and inflammatory molecules. The last group of genes, identified by GWA studies and unrelated to currently suspected mechanisms of arterial stiffness, may target transcriptional pathways controlling gene expression, differentiation of vascular smooth muscle cells, apoptosis of endothelial cells, or the immune response within the vascular wall.

Association of arterial stiffness with the angiotensin-converting enzyme gene polymorphism in healthy individuals

BACKGROUND

Arterial stiffness is an important determinant of cardiovascular morbidity and mortality. The I/D polymorphism of angiotensin-converting enzyme (ACE) gene is associated with cardiovascular disease. However, the relationship between ACE polymorphism, arterial stiffness, and wave reflections in healthy, low-risk population has not been defined yet.

METHODS

The study included 282 apparently healthy, low-risk individuals (mean age 39.7 +/- 8.9 years, 178 males). Carotid-femoral pulse wave velocity (PWV) was measured as an index of aortic stiffness, while wave reflections were assessed by augmentation index (AIx) of the central pressure waveform. I/D polymorphism of the ACE gene was determined in all subjects for the prevalence of the DD, ID, and II genotype (39, 44, and 17%, respectively). C-reactive protein (CRP) levels were determined as a marker of chronic, subclinical inflammation.

RESULTS

After adjustment for potential confounding factors, presence of D allele was associated with lower values of PWV compared to II genotype (P < 0.05), implying lower aortic stiffness for D allele carriers. There was no association between ACE genotype and wave reflections or peripheral and central systolic pressures.

CONCLUSIONS

In apparently healthy individuals, D allele is associated with lower aortic stiffness, whereas there is no association of the ACE polymorphism with wave reflections. This finding provides new insights into the possible links between ACE gene, regulation of large artery stiffness, and has implications for cardiovascular risk.

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.

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Sodium excretion as a modulator of genetic associations with cardiovascular phenotypes in the European Project on Genes in Hypertension

Hypertension is a chronic age-related disorder, affecting nearly 20% of all adult Europeans. This disease entails debilitating cardiovascular complications and is the leading cause for drug prescriptions in Europeans older than 50 years. Intensive research over the past two decades has so far failed to identify common genetic polymorphisms with a major impact on blood pressure or associated cardiovascular phenotypes, suggesting that multiple genes each with a minor impact, along with gene-gene and gene-environment interactions, play a role. The European Project on Genes in Hypertension (EPOGH) is a large-scale, family-based study in which participants from seven different populations were phenotyped and genotyped according to standardized procedures. This review article summarizes the initial 5-year findings and puts these observations into perspective against other published studies. The EPOGH demonstrated that phenotype-genotype relations strongly depend on host factors such as gender and lifestyle, in particular salt intake as reflected by the 24-h urinary excretion of sodium. The EPOGH therefore highlights the concept that phenotype-genotype relations can only be studied within a defined ecogenetic context.

Reference Values in White Europeans for the Arterial Pulse Wave Recorded by Means of the SphygmoCor Device

Measurement of blood pressure together with applanation tonometry at the radial artery allows the reproducible assessment of various indexes of arterial stiffness, including the peripheral (PPp) and central pulse pressures (PPc) and the peripheral (Alp) and central augmentation indexes (Alc). We defined preliminary diagnostic thresholds, using the distributional characteristics of these hemodynamic measurements in a reference population. We randomly recruited 870 subjects from 3 European populations. PPp was the average difference between systolic and diastolic blood pressure measured five times at one home visit. For measurement of PPc, Alp and Alc, we used the SphygmoCor device. We selected subjects without hypertension, diabetes, dyslipidemia in need of medical treatment or previous or concomitant cardiovascular disease. The study population included 228 men and 306 women (mean age 34.9 years). All hemodynamic measurements were curvilinearly related to age, and Alp and Alc were lower in men than in women. In men at age 40, the upper 95% prediction bands of the relations of the hemodynamic measurements with age approximated 60 mmHg for PPp, 40 mmHg for PPc, 90% for Alp, and 30% for Alc. For PPc, Alp and Alc, these thresholds must be adjusted for age, leading to lower and higher thresholds at younger and older age, respectively. In addition, in women of any age, the Alp and Alc thresholds must be increased by 10% and 7%, respectively. Pending validation in prospective outcome studies, distributional characteristics of arterial stiffness indexes in a reference population can be used to generate operational thresholds for use in clinical practice.

Aldosterone synthase gene polymorphism, stroke volume and age-related changes in aortic pulse wave velocity in subjects with hypertension

PURPOSE

In rats, chronic aldosterone administration with high diet intake increases aortic stiffness independent of mechanical stress. In hypertensive humans, enhanced plasma aldosterone and arterial stiffness are positively associated. Whether the aldosterone synthase gene polymorphism (ASGP) CYP11B2 influences the age-related changes in blood pressure (BP) and arterial stiffness in hypertensive subjects has never been investigated.

METHODS

In 425 untreated hypertensive men and women, ASGP was evaluated together with aortic pulse wave velocity (PWV). In 191 of these subjects, cardiac haemodynamics were measured using echo-Doppler techniques.

RESULTS

In the overall population, independently of sex, the TC and CC genotypes of ASPG had significantly higher heart rate (HR) (P < 0.05) and lower stroke index (P < 0.01) than the TT genotype, but did not affect BP. In men, the adjusted slopes of the curves relating age to PWV and HR were significantly steeper (P = 0.04; P = 0.002) for the TC and CC than for the TT genotype. Such gene-related differences were not observed for the age-systolic BP relationship.

CONCLUSION

In hypertensive subjects, the TC and CC genotypes of ASGP involve, by comparison with the TT genotype, significantly higher HR and reduced stroke index. In men with the C allele, the reduced stroke index (cardiac effect) compensates for the steep increase of PWV with age (arterial effect), thus modulating the cardiovascular phenotype and explaining the lack of increased incidence of systolic hypertension. The results are consistent with a local role of endogenous aldosterone on both heart and vessels.

An updated clinical primer on large artery mechanics: implications of pulse waveform analysis and arterial tonometry

PURPOSE OF REVIEW

The use of pulse wave analysis with arterial tonometry has accelerated over the last year. Despite approval from the US Food and Drug Administration in 2001 on the use of generalized transfer function to generate the central (aortic) pressure wave from the radial waveform, this technique is still questioned. This review summarizes major findings on (a) value of arterial tonometry in determining indices of cardiovascular function, (b) use of these indices in outcome and drug studies, (c) relevance to major trials on blood pressure reduction.

RECENT FINDINGS

Pulse pressure has emerged as a better predictor of cardiac ischemic events than systolic, diastolic, and mean brachial pressure. Central systolic and pulse pressure and augmentation index have shown an even better relation with cardiovascular events and with outcomes. The claim by specific angiotensin-converting enzyme inhibitor and angiotensin receptor blocker drugs of their benefits "beyond blood pressure lowering" has been challenged on the basis of greater reduction in central and aortic pressure compared with brachial pressure measured by cuff sphygmomanometer, as shown by the pREterax in regression of Arterial Stiffness in a contrOlled double-bliNd study. Augmentation index is higher in hypertension, is inversely related to body height, and can be reduced by exercise. Augmentation index shows a linear relation with age up to 60 years. Regrettably, recent major trials such as the Comparison of Amlodipine versus Enalapril to Limit Occurrences of Thrombosis, Prevention of Events with Angiotensin Converting Enzyme Inhibition, and Valsartan Antihypertensive Long-term Use Evaluation studies have not included pulse wave analysis to distinguish the relative benefit of different drugs.

SUMMARY

Pulse wave analysis will assist in a better understanding of hypertension as well as in establishing the extent of cardiovascular disease and for monitoring therapy.