Carlos Labat

Determinants of pulse wave velocity in healthy people and in the presence of cardiovascular risk factors: 'Establishing normal and reference values'

Aims Carotid–femoral pulse wave velocity (PWV), a direct measure of aortic stiffness, has become increasingly important for total cardiovascular (CV) risk estimation. Its application as a routine tool for clinical patient evaluation has been hampered by the absence of reference values. The aim of the present study is to establish reference and normal values for PWV based on a large European population. Methods and results We gathered data from 16 867 subjects and patients from 13 different centres across eight European countries, in which PWV and basic clinical parameters were measured. Of these, 11 092 individuals were free from overt CV disease, non-diabetic and untreated by either anti-hypertensive or lipid-lowering drugs and constituted the reference value population, of which the subset with optimal/normal blood pressures (BPs) (n = 1455) is the normal value population. Prior to data pooling, PWV values were converted to a common standard using established conversion formulae. Subjects were categorized by age decade and further subdivided according to BP categories. Pulse wave velocity increased with age and BP category; the increase with age being more pronounced for higher BP categories and the increase with BP being more important for older subjects. The distribution of PWV with age and BP category is described and reference values for PWV are established. Normal values are proposed based on the PWV values observed in the non-hypertensive subpopulation who had no additional CV risk factors. Conclusion The present study is the first to establish reference and normal values for PWV, combining a sizeable European population after standardizing results for different methods of PWV measurement.

Short Telomeres Are Associated With Increased Carotid Atherosclerosis in Hypertensive Subjects

Abstract—Recent studies have shown that individuals with shorter telomeres present a higher prevalence of arterial lesions and higher risk of cardiovascular disease mortality. As a group, patients with high blood pressure are at an increased risk for cardiovascular diseases. However, some hypertensive patients are more prone than others to atherosclerotic lesions. The main objective of this study was to examine the relationship between telomere length, as expressed in white blood cells, and carotid artery atherosclerotic plaques in hypertensive males. Data from 163 treated hypertensive men who were volunteers for a free medical examination were analyzed. Extracranial carotid plaques were assessed with B-mode ultrasound. Telomere length was measured from DNA samples extracted from white blood cells. The results of this study show that telomere length was shorter in hypertensive men with carotid artery plaques versus hypertensive men without plaques (8.17±0.07 kb versus 8.46±0.07 kb; P <0.01). Multivariate analysis showed that in addition to age, telomere length was a significant predictor of the presence of carotid artery plaques. The findings from this study suggest that in the presence of chronic hypertension, which is a major risk factor for atherosclerotic lesions, shorter telomere length in white blood cells is associated with an increased predilection to carotid artery atherosclerosis.

Telomeres shorten at equivalent rates in somatic tissues of adults

Telomere shortening in somatic tissues largely reflects stem cell replication. Previous human studies of telomere attrition were predominantly conducted on leukocytes. However, findings in leukocytes cannot be generalized to other tissues. Here we measure telomere length in leukocytes, skeletal muscle, skin and subcutaneous fat of 87 adults (aged 19–77 years). Telomeres are longest in muscle and shortest in leukocytes, yet are strongly correlated between tissues. Notably, the rates of telomere shortening are similar in the four tissues. We infer from these findings that differences in telomere length between proliferative (blood and skin) and minimally proliferative tissues (muscle and fat) are established during early life, and that in adulthood, stem cells of the four tissues replicate at a similar rate.

Increased Carotid Wall Elastic Modulus and Fibronectin in Aldosterone-Salt–Treated Rats Effects of Eplerenone

Background—Previous studies have demonstrated the development of cardiac fibrosis in aldosterone (Aldo)–salt hypertensive rats. Our aim was to determine the effects of Aldo and the Aldo receptor antagonist eplerenone (Epl) on in vivo mechanical properties of the carotid artery using echo-tracking system. Methods and Results—Aldo was administered (1 &mgr;g/h) in uninephrectomized Sprague-Dawley rats (SD) receiving a high-salt diet from 8 to 12 weeks of age. Uninephrectomized control SD rats received a normal salt diet without Aldo. Three groups of Aldo-salt rats were treated with 1, 10, or 30 mg/kg−1 · d−1 of Epl by gavage. Elasticity was measured by elastic modulus (Einc)-wall stress curves using medial cross-sectional area (MCSA). The structure of the arterial wall was analyzed by histomorphometry (elastin and collagen), immunohistochemistry (EIIIA fibronectin, Fn), and Northern blot (collagens I and III). Aldo produced increased systolic arterial pressure, pulse pressure, Einc, MCSA, and EIIIA Fn with no change in wall stress or elastin and collagen densities compared with controls without Aldo. No differences in collagen mRNA levels were detected between groups. Epl blunted the increase in pulse pressure in Aldo rats and normalized Einc-wall stress curves, MCSA, and EIIIA Fn. These effects were dose dependent and not accompanied by a reduction in wall stress. Conclusions—Aldo is able to increase arterial stiffness associated with Fn accumulation, independently of wall stress. The preventive effects of Epl suggest a direct role for mineralocorticoid receptors in mechanical and structural alterations of large vessels in rat hyperaldosteronism.

Validation of a new non-invasive portable tonometer for determining arterial pressure wave and pulse wave velocity: the Pulsepen device

Objective To validate a new, small portable tonometer (PulsePen) that is able to assess carotid artery pressure and to measure pulse wave velocity (PWV) non-invasively. Its software provides absolute arterial pressure values, an assessment of arterial pulse wave contours, an estimation of reflection waves and measurements of PWV. Design and methods Two validation studies were carried out. The aim of the first study was to compare arterial pressure values and pulse wave contours recorded in the carotid artery using the PulsePen versus intra-arterial simultaneous measurements in 10 patients undergoing cardiac catheterization. The pulse wave contour was assessed using Fourier analysis. The comparison between the two methods showed no difference in arterial pressure wave spectral moduli from harmonics 1 to 6. The second study compared PWV measurements taken with the PulsePen (one tonometer) and measurements performed with two Millar tonometers in 68 subjects (32 men, 36 women). PulsePen measurements were realized as two consecutive measurements in the carotid and femoral arteries, both synchronized by electrocardiogram. The pulse wave transit time was calculated as the difference between the time delay of the femoral pulse wave and the carotid pulse wave in relation to the R wave of the electrocardiogram. These measurements were compared with PWV obtained by simultaneous carotid and femoral measurements with the two Millar tonometers. No difference between the two methods was found, with a variation coefficient of 7.7%. The variation coefficients of the inter-observer and intra-observer reproducibility for the PulsePen were 7.9 and 7.2%, respectively. Conclusions These results show that the PulsePen enables an easy and reliable evaluation of central arterial pressure and stiffness in clinical ambulatory practice, especially in high-risk patients in whom arterial stiffness has been shown to be a significant indicator of morbidity and mortality.

Pulse Pressure Amplification: A Mechanical Biomarker of Cardiovascular Risk

OBJECTIVES The aim of this study was to determine whether the carotid/brachial (C/B) ratio is an independent predictor of cardiovascular (CV) risk. BACKGROUND Brachial and carotid pulse pressure (PP) are independent predictors of CV risk, mainly in elderly patients. Because PP is physiologically lower at the brachial than at the carotid arterial site, PP amplification is represented by the C/B ratio and could independently predict CV risk. METHODS In a Paris population (n = 834), brachial and carotid PP were measured from sphygmomanometry and pulse wave analysis. With stepwise multiple regression, carotid PP was calculated from a nomogram including age, sex, body height, brachial PP, and plasma glucose. This model was applied to 125,151 subjects, followed for 12 years, during which 3,997 deaths occurred (735 of CV origin). With Cox regression analysis, multi-adjusted hazard ratios (HRs) were calculated for 1 SD increase of brachial PP, calculated carotid PP, and C/B ratio. RESULTS Brachial PP was significantly associated with both CV and all-cause mortality (HR: 1.16, 95% confidence interval [CI]: 1.13 to 1.19, and HR: 1.13, 95% CI: 1.10 to 1.17, respectively). Calculated carotid PP predicted a similar risk (HR: 1.21, 95% CI: 1.15 to 1.28, and HR: 1.18, 95% CI: 1.12 to 1.25, respectively). Finally, the C/B ratio was a strong risk predictor (HR: 1.22, 95% CI: 1.12 to 1.32, and HR: 1.41, 95% CI: 1.14 to 1.73, respectively). Addition of drug treatment and other confounding variables did not statistically modify the results. CONCLUSIONS Brachial PP, calculated carotid PP, and C/B PP amplification all predict CV mortality. In contrast to brachial and carotid PP, the C/B ratio is less dependent on blood pressure calibration and thus can be directly applicable to large population studies.

Prevention of aortic and cardiac fibrosis by spironolactone in old normotensive rats.

OBJECTIVES Because the synthesis of aldosterone is mainly modulated by angiotensin II through type I receptor stimulation and because converting enzyme inhibition (CEI) does not modify aortic extracellular matrix in old normotensive rats, the aim of the present study was to determine whether inhibition of aldosterone formation was able to prevent aortic fibrosis in old Sprague-Dawley normotensive rats. BACKGROUND We have previously shown that long-term aldosterone antagonism prevents the age-related increase in aortic collagen accumulation in young spontaneously hypertensive rats, independent of blood pressure changes. In contrast, we reported that the positive effects of CEI in the prevention of aortic collagen accumulation were related to the inhibition of angiotensin II actions on angiotensin II type I receptors. METHODS For this purpose, we studied the histomorphometric and stiffness (echo-tracking technique) changes of an eight-week treatment with the aldosterone antagonist spironolactone by comparison with placebo. RESULTS At the end of treatment, spironolactone in conscious animals did not change intra-arterial blood pressure, aortic and carotid wall thickness, and cardiac weight. Cardiac collagen density and, to a lesser extent, carotid collagen and elastin densities and contents were significantly decreased in association with an increase of carotid distensibility. CONCLUSIONS These results show that in old normotensive rats, spironolactone can markedly prevent cardiac and, to a lesser extent, arterial fibrosis and improve arterial stiffness, despite a lack of hypotensive effect.

Angiotensin II type 1 receptor-153A/G and 1166A/C gene polymorphisms and increase in aortic stiffness with age in hypertensive subjects.

Objectives Arterial stiffness is associated with excess morbidity and mortality, independently of other cardiovascular risk factors. Age is the main determinant responsible for arterial wall changes leading to arterial stiffening. Environmental and genetic factors may however influence the magnitude of the effects of age on large artery stiffness. Design and methods The present study assessed whether or not the relationship between age and aortic stiffness was influenced by genetic variants of angiotensinogen (AGT 174T/M, 235M/T), angiotensin converting enzyme (ACE I/D), angiotensin II type 1 receptor (AT1 1166A/C, −153A/G) and aldosterone synthase (CYP11B2 −344T/C). This study was realized in 441 untreated hypertensive subjects of European origin (aged 18–74 years). Aortic stiffness was assessed by carotid–femoral pulse wave velocity (PWV). Results Carriers of the angiotensin II type 1 receptor −153G allele showed a steeper age/PWV relationship than the AT1 −153AA subjects. The effect of the AT1 −153A/G polymorphism on aortic stiffness became apparent after the age of 55 years. In subjects with the AT1 1166C allele, the relationship age/PWV is shifted upward, indicating higher values of aortic stiffness at any age compared to the AT1 1166AA patients. Carriers of both the AT11166C and −153G alleles presented the additive effects of these 2 genotypes on aortic stiffness. Angiotensinogen, ACE and CYP11B2 genotypes did not influence the effects of age on PWV. Conclusions AT1 receptor genotypes could influence arterial ageing in hypertensive subjects. These results also show that the association between genotypes and arterial stiffness may manifest itself later in life.

Prostanoid receptors involved in the relaxation of human pulmonary vessels

To characterize the prostanoid receptors on human pulmonary smooth muscle involved in vasodilatations, isolated arteries and veins were contracted with norepinephrine (10 μM) and vessels were subsequently challenged with different prostanoid‐receptor agonists in the absence or presence of selective antagonists. Prostaglandin D2 (PGD2) and the selective DP‐receptor agonist, BW245C, induced relaxations in the contracted human pulmonary venous preparations. The pD2 values were: 6.88±0.11 (n=17) and 7.31±0.12 (n=5), respectively. The relaxant responses induced by PGD2 were reduced by the selective DP‐receptor antagonist, BWA868C, and the estimated pA2 value was 7.84±0.16 (n=4). PGD2 and BW245C did not relax contracted human pulmonary arteries. The selective IP‐receptor agonists, iloprost and cicaprost, both induced relaxations in the contracted human vascular preparations. The pD2 values for iloprost were: 7.84±0.08 (n=6) and 8.25±0.06 (n=4) and for cicaprost: 8.06±0.12 (n=5) and 8.11±0.09 (n=5) in arteries and veins respectively. Prostaglandin E2 (PGE2) and the EP2/EP3‐receptor agonist, misoprostol, partially relaxed the contracted venous preparations and the pD2 values were: 8.10±0.15 (n=15) and 6.24±0.33 (n=3), respectively. These relaxations suggest the presence of an EP receptor in the human pulmonary veins. The contracted human pulmonary arteries did not relax when challenged with PGE2. In human pulmonary venous preparations, the PGE2‐induced relaxations were neither modified by treatment with TP/EP4‐receptor antagonist, AH23848B (10 and 30 μM, n=6), nor by the DP/EP1/EP2‐receptor antagonist, AH6809 (3 μM, n=6). These data suggest that the relaxation induced by prostanoids involved DP‐, IP‐receptors and to a lesser extent an EP‐receptor on human pulmonary venous smooth muscle. In contrast, only the IP‐receptor is involved in the prostanoid induced relaxations on human pulmonary arterial smooth muscle.

The endothelial mineralocorticoid receptor regulates vasoconstrictor tone and blood pressure

Pathophysiological aldosterone (aldo)/ mineralocorticoid receptor (MR) signaling has significant effects on the cardiovascular system, resulting in hypertension and cardiovascular remodeling; however, the specific contribution of the vascular MR to blood pressure regulation remains to be established. To address this question, we generated a mouse model with conditional overexpression of the MR in endothelial cells (MR‐EC). In basal conditions, MR‐EC mice developed moderate hypertension that could be reversed by canrenoate, a pharmacological MR antagonist. MR‐EC mice presented increased contractile response of resistance arteries to vasoconstrictors (phenylephrine, thromboxane A2 analog, angiotensin II, and endothelin 1) in the absence of vascular morphological alterations. The acute blood pressure response to angiotensin II or endothelin 1 infusion was increased in MR‐EC mice compared with that in littermate controls. These observations demonstrate that enhanced MR activation in the endothelium generates an increase in blood pressure, independent of stimulation of renal tubular Na+ transport by aldo/MR or direct activation of smooth muscle MR and establish one mechanism by which endothelial MR activation per se may contribute to impaired vascular reactivity.—Nguyen Dinh Cat, A., Griol‐Charhbili, V., Loufrani, L., Labat, C, Benjamin, L., Farman, N., Lacolley, P., Henrion, D., and Jaisser, F. The endothelial mineralocorticoid receptor regulates vasoconstrictor tone and blood pressure. FASEB J. 24, 2454–2463 (2010). www.fasebj.org