Endothelium-derived nitric oxide regulates arterial elasticity in human arteries in vivo

Arterial pulse wave velocity, inflammatory markers, pathological GH and IGF states, cardiovascular and cerebrovascular disease

Blood pressure (BP) measurements provide information regarding risk factors associated with cardiovascular disease, but only in a specific artery. Arterial stiffness (AS) can be determined by measurement of arterial pulse wave velocity (APWV). Separate from any role as a surrogate marker, AS is an important determinant of pulse pressure, left ventricular function and coronary artery perfusion pressure. Proximal elastic arteries and peripheral muscular arteries respond differently to aging and to medication. Endogenous human growth hormone (hGH), secreted by the anterior pituitary, peaks during early adulthood, declining at 14% per decade. Levels of insulin-like growth factor-I (IGF-I) are at their peak during late adolescence and decline throughout adulthood, mirror imaging GH. Arterial endothelial dysfunction, an accepted cause of increased APWV in GH deficiency (GHD) is reversed by recombinant human (rh) GH therapy, favorably influencing the risk for atherogenesis. APWV is a noninvasive method for measuring atherosclerotic and hypertensive vascular changes increases with age and atherosclerosis leading to increased systolic blood pressure and increased left ventricular hypertrophy. Aerobic exercise training increases arterial compliance and reduces systolic blood pressure. Whole body arterial compliance is lowered in strength-trained individuals. Homocysteine and C-reactive protein are two inflammatory markers directly linked with arterial endothelial dysfunction. Reviews of GH in the somatopause have not been favorable and side effects of treatment have marred its use except in classical GHD. Is it possible that we should be assessing the combined effects of therapy with rhGH and rhIGF-I? Only multiple intervention studies will provide the answer.

Location of arterial stiffening differs in those with impaired fasting glucose versus diabetes: implications for left ventricular hypertrophy from the Multi-Ethnic Study of Atherosclerosis

OBJECTIVE

To determine whether middle-aged and older individuals with impaired fasting glucose (IFG), but no clinical evidence of cardiovascular disease, exhibit abnormal changes in proximal thoracic aortic stiffness or left ventricular (LV) mass when compared with healthy counterparts.

RESEARCH DESIGN AND METHODS

From the Multi-Ethnic Study of Atherosclerosis, 2,240 subjects with normal fasting glucose (NFG), 845 with IFG, and 414 with diabetes, all aged 45 to 85 years and without preexisting coronary artery disease, underwent MRI determinations of total arterial and proximal thoracic aortic stiffness and LV mass. The presence or absence of other factors known to influence arterial stiffness was assessed.

RESULTS

After adjustment for clinical factors known to modify arterial stiffness, proximal thoracic aortic stiffness was not increased in those with IFG compared with those with NFG (1.90 +/- 0.05 versus 1.91 +/- 0.04 10(-3) mmHg(-1), respectively, P = 0.83). After accounting for clinical factors known to influence LV mass, LV mass was increased in those with diabetes relative to those with NFG (150.6 +/- 1.4 versus 145.8 +/- 0.81 g, P < 0.0009) but not in those with IFG in comparison with NFG (145.2 +/- 1.03 versus 145.8 +/- 0.81 g, P = 0.56).

CONCLUSIONS

Middle-aged and older individuals with the pre-diabetes state of IFG do not exhibit abnormal proximal thoracic distensibility or LV hypertrophy relative to individuals with NFG. For this reason, an opportunity may exist in those with IFG to prevent LV hypertrophy and abnormal aortic stiffness that is observed in middle-aged and older individuals with diabetes.

Central sympathetic overactivity: maladies and mechanisms

There is growing evidence to suggest that many disease states are accompanied by chronic elevations in sympathetic nerve activity. The present review will specifically focus on central sympathetic overactivity and highlight three main areas of interest: 1) the pathological consequences of excessive sympathetic nerve activity; 2) the potential role of centrally derived nitric oxide in the genesis of neural dysregulation in disease; and 3) the promise of several novel therapeutic strategies targeting central sympathetic overactivity. The findings from both animal and human studies will be discussed and integrated in an attempt to provide a concise update on current work and ideas in these important areas.

Pulse transit times to the capillary bed evaluated by laser Doppler flowmetry

The pulse transit time (PTT) of a wave over a specified distance along a blood vessel provides a simple non-invasive index that can be used for the evaluation of arterial distensibility. Current methods of measuring the PTT determine the propagation times of pulses only in the larger arteries. We have evaluated the pulse arrival time (PAT) to the capillary bed, through the microcirculation, and have investigated its relationship to the arterial PAT to a fingertip. To do so, we detected cardiac-induced pulse waves in skin microcirculation using laser Doppler flowmetry (LDF). Using the ECG as a reference, PATs to the microcirculation were measured on the four extremities of 108 healthy subjects. Simultaneously, PATs to the radial artery of the left index finger were obtained from blood pressure recordings using a piezoelectric sensor. Both PATs correlate in similar ways with heart rate and age. That to the microcirculation is shown to be sensitive to local changes in skin perfusion induced by cooling. We introduce a measure for the PTT through the microcirculation. We conclude that a combination of LDF and pressure measurements enables simultaneous characterization of the states of the macro and microvasculature. Information about the microcirculation, including an assessment of endothelial function, may be obtained from the responses to perturbations in skin perfusion, such as temperature stress or vasoactive substances.

Arterial stiffness is associated with raised levels of the inflammatory marker erythrocyte sedimentation rate among ischaemic stroke patients

We studied the relationship of arterial stiffness, measured by carotid-femoral pulse wave velocity and inflammation, measured by serum erythrocyte sedimentation rate among 334 ischaemic stroke patients. There was a significant correlation between carotid-femoral pulse wave velocity and erythrocyte sedimentation rate (P = 0.001), a relationship independent of age, hypertension, diabetes and smoking. Arterial stiffness and inflammation are associated among ischaemic stroke patients and are independent of established vascular risk factors.

Endothelial dysfunction is related to aldosterone excess and raised blood pressure

Primary aldosteronism (PA) is a secondary hypertension characterized by autonomous aldosterone hypersecretion from adrenocortical adenoma and/or hyperplasia. Recently it has been suggested that aldosterone excess is directly involved in the development of cardiovascular injury in PA independent of its hypertensive effect. The present study was designed to examine the relationship between aldosterone excess and endothelial dysfunction in PA patients. 25 PA patients were studied for vascular endothelial function by ultrasound measurement of flow-mediated vasodilation (FMD), and 10 PA patients were re-evaluated 3 months after surgical or medical treatment; 10 age-, gender-, and blood pressurematched hypertensive patients served as control subjects. Percent (%) FMD in PA patients (4.6+/-2.0%) was significantly (p < 0.0001) lower than that in the control subjects (7.9+/-2.0%). %FMD showed significant (p < 0.05) negative correlations with systolic blood pressure (SBP) (r=-0.48), brachial-ankle pulse wave velocity (r=-0.52), plasma aldosterone concentration (PAC) (r=-0.42), and aldosterone-renin ratio (ARR) (r=-0.42), while SBP showed a positive correlation with PAC (r=0.47). Percent FMD, SBP, PAC, and ARR significantly (p < 0.05) improved after surgical and medical treatment, although the changes of %FMD did not correlate with those of SBP, PAC or ARR. In conclusion, the present study has demonstrated that PA patients have endothelial dysfunction, which is related to aldosterone excess and raised blood pressure, and reversible after treatment, suggesting that aldosterone excess contributes to the development of endothelial dysfunction due to its hypertensive effect and/or its direct effect on the cardiovascular system.

Assessment of arterial stiffness, a translational medicine biomarker system for evaluation of vascular risk

AIMS

Stiffening of the large arteries is a common feature of aging and is exacerbated by a number of disorders such as hypertension, diabetes, and renal disease. Arterial stiffening is recognized as an important and independent risk factor for cardiovascular events. This article will provide a comprehensive review of the recent advance on assessment of arterial stiffness as a translational medicine biomarker for cardiovascular risk.

DISCUSSIONS

The key topics related to the mechanisms of arterial stiffness, the methodologies commonly used to measure arterial stiffness, and the potential therapeutic strategies are discussed. A number of factors are associated with arterial stiffness and may even contribute to it, including endothelial dysfunction, altered vascular smooth muscle cell (SMC) function, vascular inflammation, and genetic determinants, which overlap in a large degree with atherosclerosis. Arterial stiffness is represented by biomarkers that can be measured noninvasively in large populations. The most commonly used methodologies include pulse wave velocity (PWV), relating change in vessel diameter (or area) to distending pressure, arterial pulse waveform analysis, and ambulatory arterial stiffness index (AASI). The advantages and limitations of these key methodologies for monitoring arterial stiffness are reviewed in this article. In addition, the potential utility of arterial stiffness as a translational medicine surrogate biomarker for evaluation of new potentially vascular protective drugs is evaluated.

CONCLUSIONS

Assessment of arterial stiffness is a sensitive and useful biomarker of cardiovascular risk because of its underlying pathophysiological mechanisms. PWV is an emerging biomarker useful for reflecting risk stratification of patients and for assessing pharmacodynamic effects and efficacy in clinical studies.

Arterial stiffness acutely decreases after whole-body vibration in humans

BACKGROUND

Increased arterial stiffness is a well-established cardiovascular risk factor. Mechanical stimuli to artery, such as compression, elicit vasodilation and acutely decrease arterial stiffness. As whole-body vibration (WBV)-induced oscillation is propagated at least to lumbar spine, WBV mechanically stimulates abdominal and leg arteries and may decrease arterial stiffness. WBV is feasible in vulnerable and immobilized humans. Therefore, it is worthwhile to explore the possibility of WBV as a valuable adjunct to exercise training.

AIM

The aim of this study was to investigate the acute effects of WBV on arterial stiffness.

METHODS

Ten healthy men performed WBV and control (CON) trials on separate days. The WBV session consisted of 10 sets of vibration (frequency, 26 Hz) for 60 s with an inter-set rest period of 60 s. Subjects maintained a static squat position with knees bent on a platform. In the CON trial, WBV stimulation was not imposed. Blood pressure, heart rate and brachial-ankle pulse wave velocity (baPWV), an index of arterial stiffness, were measured before and 20, 40 and 60 min after both trials.

RESULTS AND CONCLUSION

Heart rate and blood pressure did not change from baseline after both trials. Although baPWV did not change in the CON trial (baseline vs. after 20, 40 and 60 min; 1144 +/- 35 vs. 1164 +/- 41, 1142 +/- 39, and 1148 +/- 34 cm s(-1)), baPWV decreased 20 and 40 min after the WBV trial and recovered to baseline 60 min after the trial (1137 +/- 28 vs. 1107 +/- 30, 1108 +/- 28, and 1128 +/- 25 cm s(-1)). These results suggest that WBV acutely decreases arterial stiffness.

Short-term hypoxia reduces arterial stiffness in healthy men

This study examined the effects of hypoxia (80% arterial oxyhaemoglobin saturation for 20 min) and the accompanying changes in heart rate and blood pressure on two components of arterial stiffness in healthy men. Augmentation index (AIx) and time to reflection (Tr) representing measures of muscular artery and aortic stiffness, respectively, were continuously measured. At first, subjects were exposed to either hypoxia (n = 12) or room air (n = 5). During early hypoxia AIx increased by 6% before decreasing to baseline. After hypoxia AIx decreased by a further 6%. In contrast there was no change in Tr. Six subjects were then exposed to hypoxia following infusion with the nitric oxide (NO) synthase inhibitor NG-mono-methyl-L: -arginine (L-NMMA) or saline. During hypoxia AIx decreased by 12% following saline but increased by 14% after L-NMMA and Tr did not change. These findings suggest that hypoxia may induce NO-mediated vasodilatation of small muscular arteries but not the aorta.

Neurogenic-nitric oxide interactions affecting brachial artery mechanics in humans: roles of vessel distensibility vs. diameter

The purpose of this investigation was to assess the interactive influence of sympathetic activation and supplemental nitric oxide (NO) on brachial artery distensibility vs. its diameter. It was hypothesized that 1) sympathetic activation and NO competitively impact muscular conduit artery (brachial artery) mechanics, and 2) neurogenic constrictor input affects conduit vessel stiffness independently of outright changes in conduit vessel diastolic diameter. Lower body negative pressure (LBNP) and a cold pressor stress (CPT) were used to study the changes in conduit vessel mechanics when the increased sympathetic outflow occurred with and without changes in heart rate (LBNP -40 vs. -15 mmHg) and blood pressure (CPT vs. LBNP). These maneuvers were performed in the absence and presence of nitroglycerin. Neither LBNP nor CPT altered brachial artery diastolic diameter; however, distensibility was reduced by 25 to 54% in each reflex (all P < 0.05). This impact of sympathetic activation on brachial artery distensibility was not altered by nitroglycerin supplementation (21-54%; P < 0.05), although baseline diameter was increased by the exogenous NO (P < 0.05). The results indicate that sympathetic excitation can reduce the distensibility of the brachial artery independently of concurrent changes in diastolic diameter, heart rate, and blood pressure. However, exogenous NO did not minimize or reverse brachial stiffening during sympathetic activation. Therefore, sympathetic outflow appears to impact the stiffness of this conduit vessel rather than its diastolic diameter or, by inference, its local resistance to flow.

Endothelial function and arterial stiffness in normotensive normoglycemic first-degree relatives of diabetic patients are independent of the metabolic syndrome

BACKGROUND AND AIM

The aim of the present study was to investigate endothelial function and arterial stiffness in normotensive normoglycemic first-degree relatives (offspring) of diabetic subjects and to explore the relationship with the metabolic syndrome and its components.

METHODS AND RESULTS

Forty-five healthy normotensive normoglycemic subjects (aged 18-42 years), 29 first-degree relatives of diabetic subjects (FDR) and 16 with no parental history of type 2 diabetes mellitus were studied. Endothelial function was measured as flow-mediated dilation of the brachial artery (FMD) and arterial stiffness as carotid-femoral pulse wave velocity (PWV). Insulin resistance was calculated by homeostasis model assessment (HOMA). Plasma levels of inflammation markers (hsCRP, TNF-alpha, IL-1beta, CD40L, VCAM, and ICAM) were evaluated. Normotensive normoglycemic FDR presented a 33% lower flow-mediated dilation than the control group (9.8+/-5.2 vs. 16.2+/-7.6%, p<0.01). FMD was reduced in FDR, with or without insulin resistance, whereas arterial stiffness was significantly increased only in FDR with insulin resistance. To investigate the role of FDR status independently of altered components of the metabolic syndrome, subjects with no altered components of the metabolic syndrome were compared according to their FDR status: FDR subjects with no altered components of the metabolic syndrome presented a blunted endothelial function (lower FMD: 11.2+/-1.6 vs. 16.8+/-2.0%, p<0.05) and stiffer large arteries (higher PWV: 9.6+/-0.3 vs. 8.8+/-0.3m/s, p<0.05) than controls.

CONCLUSION

Normoglycemic first-degree relatives of diabetic subjects have blunted endothelial function and increased stiffness of the large arteries. These alterations are already present at a very young age, before any alteration in glycemic control or blood pressure values can be detected, and are independent of the presence of the metabolic syndrome and its altered components.

Finger photoplethysmogram pulse amplitude changes induced by flow-mediated dilation

This study was conducted to investigate the utility and efficacy of finger photoplethysmogram pulse amplitude (PPG-AC) in comparison with the standard Doppler ultrasound in assessing an endothelial function via flow-mediated dilation (FMD). High-resolution B-mode scanning of the right brachial artery (BA) of 31 healthy subjects aged 39.7 +/- 11.3 (range 22-64) years and 52 risk subjects aged 47.7 +/- 10.8 (range 30-65) years were performed before and after 4 min of upper arm occlusion. Concurrent with the ultrasound measurement (where color Doppler imaging was used to enhance arterial boundary detection), PPG signals were recorded from both index fingers for cross evaluation and comparison. Our results show that the finger PPG-AC exhibits a similar response to that of the well-known BA dilation: following the release of pressure (cuff around the BA), the PPG-AC increases abruptly before slowly decreasing toward the baseline. The peak PPG-AC is reached significantly faster than the peak FMD measured by ultrasound among healthy and risk groups (P < 0.001). The proposed technique using a finger photoplethysmogram can be applied in a rapid and non-invasive assessment of peripheral vascular functions as an alternative low-cost and less operator-dependent tool compared to ultrasound.

Systemic arterial compliance, systemic vascular resistance, and effective arterial elastance during exercise in endurance-trained men

Systemic arterial compliance (C) and vascular resistance (R) regulate effective arterial elastance (Ea), an index of artery load. Increases in Ea during exercise are due primarily to reductions of C and maintain optimal ventricular-arterial coupling. Because C at rest and left ventricular functional reserve are greater in endurance-trained (ET) compared with sedentary control (SC) humans, we hypothesized that reductions of C and increases in Ea are greater in ET than SC individuals. The aim of this study was to investigate C, R, and Ea during exercise in ET and SC humans. C, R, Ea, and cardiac cycle length (T) were measured at rest and during exercise of 40, 60, and 80% maximal oxygen uptake using Doppler ultrasonography in 12 SC and 13 ET men. C decreased in an exercise intensity-dependent manner in both groups, but its reductions were greater in the ET than SC subjects. Consequently, although C at rest was greater in the ET than SC group, the intergroup difference in C disappeared during exercise. Exercise-related changes in R/T were relatively slight and R/T was lower in the ET than the SC group, both at rest and during exercise. Although Ea at rest was lower in the ET than SC group, there were no intergroup differences in Ea at 40, 60, or 80% maximal oxygen uptake. We conclude that the reductions of C from rest to exercise are more marked in ET than SC humans. This may be related to the exercise-associated disappearance of the difference in Ea between ET and SC humans.

Forearm vascular reactivity and arterial stiffness in asymptomatic adults from the community

Vascular reactivity may affect the stiffness characteristics of the arterial wall. We investigated the association between forearm microcirculatory and conduit artery function and measures of arterial stiffness in 527 asymptomatic non-Hispanic white adults without known cardiovascular disease. High-resolution ultrasonography of the brachial artery (ba) was performed to assess forearm microcirculatory function (ba blood flow velocity, local shear stress, and forearm vascular resistance at rest and during reactive hyperemia) and conduit artery function (ba flow-mediated dilatation [baFMD] and ba nitroglycerin-mediated dilatation [baNMD]). Arterial stiffness was assessed by cuff-derived brachial pulse pressure and aortic pulse wave velocity (aPWV) measured by applanation tonometry. In regression analyses that adjusted for heart rate, mean arterial pressure, height, cardiovascular risk factors, and hypertension medication and statin use, higher baseline ba systolic velocity and systolic shear stress were associated with greater pulse pressure (P=0.0002 and P=0.006, respectively) and higher aPWV (each P<0.0001). During hyperemia, lower ba mean velocity and lower mean shear stress were associated with higher pulse pressure (P=0.045 and P=0.036, respectively), whereas both systolic and mean velocity (P<0.0001 and P=0.002, respectively) and systolic and mean shear stress (P<0.0001 and P=0.003, respectively) were inversely associated with aPWV. baFMD was not associated with pulse pressure but was inversely associated with aPWV (P=0.011). baNMD was inversely associated with pulse pressure (P=0.0002) and aPWV (P=0.008). Our findings demonstrate that impaired forearm microvascular function (in the form of elevated resting blood flow velocity and impaired flow reserve) and impaired brachial artery reactivity are associated with increased arterial stiffness.

Exercise reduces arterial pressure augmentation through vasodilation of muscular arteries in humans

Exercise markedly influences pulse wave morphology, but the mechanism is unknown. We investigated whether effects of exercise on the arterial pulse result from alterations in stroke volume or pulse wave velocity (PWV)/large artery stiffness or reduction of pressure wave reflection. Healthy subjects ( n = 25) performed bicycle ergometry. with workload increasing from 25 to 150 W for 12 min. Digital arterial pressure waveforms were recorded using a servo-controlled finger cuff. Radial arterial pressure waveforms and carotid-femoral PWV were determined by applanation tonometry. Stroke volume was measured by echocardiography, and brachial and femoral artery blood flows and diameters were measured by ultrasound. Digital waveforms were recorded continuously. Other measurements were made before and after exercise. Exercise markedly reduced late systolic and diastolic augmentation of the peripheral pressure pulse. At 15 min into recovery, stroke volume and PWV were similar to baseline values, but changes in pulse wave morphology persisted. Late systolic augmentation index (radial pulse) was reduced from 54 ± 3.9% at baseline to 42 ± 3.7% ( P < 0.01), and diastolic augmentation index (radial pulse) was reduced from 37 ± 1.8% to 25 ± 2.9% ( P < 0.001). These changes were accompanied by an increase in femoral blood flow (from 409 ± 44 to 773 ± 48 ml/min, P < 0.05) and an increase in femoral artery diameter (from 8.2 ± 0.4 to 8.6 ± 0.4 mm, P < 0.05). In conclusion, exercise dilates muscular arteries and reduces arterial pressure augmentation, an effect that will enhance ventricular-vascular coupling and reduce load on the left ventricle.

Arterial stiffness in diabetes and the metabolic syndrome: a pathway to cardiovascular disease

Increased arterial stiffness associated with diabetes and the metabolic syndrome may in part explain the increased cardiovascular disease risk observed in these conditions. Arterial stiffness can be estimated by quantifying pulse pressure but is better described by distensibility and compliance coefficients, pulse wave velocity and wave reflection. The most common non-invasive methodologies used to quantify these estimates of arterial stiffness (e.g. ultrasonography and applanation tonometry) are also described. We then review and summarise the current data on the associations between diabetes, the metabolic syndrome and insulin resistance on the one hand and greater arterial stiffness on the other, and identify and discuss some unresolved issues such as differential stiffening of central vs peripheral arterial segments, the impact of sex, and the pathobiology of increased arterial stiffness in diabetes and the metabolic syndrome. Finally, some considerations with regard to treatment options are presented. At present the most powerful therapy available for reducing arterial stiffness is to vigorously treat hypertension using pharmacological agents. New pharmacological strategies to reduce arterial stiffness are likely to be especially relevant to individuals with diabetes.

Antiphospholipid antibodies induce vascular functional changes in mice: a mechanism of vascular lesions in antiphospholipid syndrome?

Abstract

A premature atherosclerosis has been presumed in patients with antiphospholipid syndrome. The potential role of antiphospholipid antibodies in the development of atheroma is rather controversial. In this study, we tested the hypothesis that antiphospholipid antibodies could induce atherosclerosis via vascular functional changes. CD1 mice received one single injection of antiphospholipid monoclonal antibodies derived from male (BXSB × NZW) F1 mice with a lupus-like disease associated with an antiphospholipid syndrome and coronary artery disease. One week later, first-order mesenteric arteries (diameter 220–260 μm) were isolated and mounted on a small-vessel myograph for the measurement of the relaxation responses to acetylcholine or the NO donor nitroprusside after precontraction by phenylephrine. Five out of eight antiphospholipid monoclonal antibodies reduced the response to acetylcholine compared with control mice, and this effect was especially marked with one of them. No change in the response to nitroprusside was observed. The impairment was maintained after 3 weeks of treatment and appeared related to a moderate decrease in NO-mediated responses and a marked decrease in prostanoid-mediated relaxations. These vascular functional changes could be prevented by chronic treatment with statins or aspirin. These data could constitute additional elements supporting a direct pathogenic role of antiphospholipid antibodies. We suggest that a sub-population of these autoantibodies could be responsible for the endothelial dysfunction observed in antiphospholipid syndrome.

MAPK/ERK signalling mediates VEGF-induced bone marrow stem cell differentiation into endothelial cell

Multi-potent adult progenitor cells (MAPCs) differentiate into endothelial cells (ECs) in the presence of vascular endothelial growth factor (VEGF). The mechanism(s) of VEGF-induced differentiation of MAPCs to ECs are not yet known. We, therefore, examined the role of mitogen-activated protein kinase/extracellular signal-regulated kinase (p42/44-MAPK/ERK1/2) signalling in endothelial differentiation from bone marrow stem cells. We observed that VEGF stimulation of MAPCs for 14 days results in a significant expression of endothelial-specific gene and/or proteins including von Willebrand factor (vWF), vascular endothelial-cadherin (VE-cadherin), VEGF receptor-2 (VEGFR2), and CD31. Up-regulation of EC-specific markers was accompanied by a cobblestone morphology, expression of endothelial nitric oxide synthase (eNOS), and Dil-Ac-LDL uptake, typical for EC morphology and function. VEGF induced a sustained activation of p42 MAPK/ERK, but not that of p44 MAPK/ERK during the course of MAPCs differentiation in a time-dependent manner up to 14 days. VEGF-induced activation of p42 MAPK/ERK also led to the nuclear translocation of MAPK/ERK1/2. Incubation of MAPCs with MAPK/ERK1/2 phosphorylation inhibitor PD98059 blocked the sustained VEGF-induced MAPK/ERK1/2 phosphorylation as well as its nuclear translocation in the differentiating MAPCs. Inhibition of MAPK/ERK1/2 phosphorylation by PD98059 also blocked the expression of EC-specific genes in these cells and their differentiation to ECs. These data suggest that VEGF induces MAPC differentiation into EC via a. MAPK/ERK1/2 signalling pathway-mediated mechanism in vitro.

The new oral immunomodulating drug DiNAC induces brachial artery vasodilatation at rest and during hyperemia in hypercholesterolemic subjects, likely by a nitric oxide-dependent mechanism

OBJECTIVES

To investigate if the immunomodulator drug DINAC (1) affects arterial dimensions in asymptomatic patients with hypercholesterolemia, (2) has effects on leucocyte markers of inflammation and (3) has in vitro effects on nitric oxide synthase (NOS) in human umbilical vein endothelial cells (HUVEC).

METHODS AND RESULTS

One hundred and fifty-three patients with asymptomatic hypercholesterolemia were randomized to either 100 or 500 mg of DINAC or placebo in a double-blind, parallel-group fashion for 24 weeks. Treatment at the highest dose induced a significant increase in resting brachial artery diameter measured by ultrasound and also induced a significant increase in vessel diameter during hyperemia. However, flow-mediated vasodilation (FMD) and the vasodilatory response to nitroglycerin, lipid levels or leukocyte count were unaltered. Expression of several cell surface markers of inflammation, like CD11b and CD25, were reduced by treatment. In vitro, DINAC counteracted TNF-alpha induced reductions in NO levels and in NOS protein and mRNA levels.

CONCLUSION

The immunomodulator drug DINAC increased brachial artery diameter at rest and during hyperemia in asymptomatic subjects with hypercholesterolemia without affecting blood lipid levels. Based on parallel in vitro studies this effect is likely due to an enhancement of NOS activity.

Vessel wall stiffness in type 1 diabetes and the central hemodynamic effects of acute hypoglycemia

OBJECTIVE

To examine the effects of intravenous insulin and acute hypoglycemia on arterial wall stiffness and central hemodynamic responses in adults with and without type 1 diabetes.

RESEARCH DESIGN AND METHODS

In 30 young male volunteers [10 nondiabetic (Group 1); 10 with type 1 diabetes, <5 yr duration (Group 2); 10 with type 1 diabetes, >15 yr duration (Group 3)], intravenous insulin was administered to provoke an acute autonomic reaction (R) to hypoglycemia. Heart rate, peripheral blood pressure, and pulse wave analysis (radial artery) were monitored. Augmentation index (AIx), a measure of arterial wall stiffness and wave reflection, and central arterial pressure were recorded.

RESULTS

At baseline, no significant differences were observed between Groups 1 and 2 in either AIx or in central arterial pressure, but in Group 3, both measures were significantly higher. All three groups exhibited similar responses to intravenous infusion of insulin and to hypoglycemia: AIx fell progressively from baseline to R, peripheral systolic blood pressure increased, and central systolic pressure decreased.

CONCLUSION

Compared with age- and sex-matched nondiabetic controls, people who had type 1 diabetes for a long duration had increased stiffness of vessel walls. The opposing responses in peripheral and central systolic pressures during hypoglycemia may be related to the reduction in AIx, which causes diminished amplification of the systolic pressure wave. Changes in AIx are probably mediated by a direct action of insulin on arterial endothelium, or changes in heart rate. These functional changes may contribute to the increased cardiovascular morbidity that is associated with type 1 diabetes of long duration.

Exercise and postprandial lipaemia: effects on peripheral vascular function, oxidative stress and gastrointestinal transit

Postprandial lipaemia may lead to an increase in oxidative stress, inducing endothelial dysfunction. Exercise can slow gastric emptying rates, moderating postprandial lipaemia. The purpose of this study was to determine if moderate exercise, prior to fat ingestion, influences gastrointestinal transit, lipaemia, oxidative stress and arterial wall function. Eight apparently healthy males (age 23.6 ± 2.8 yrs; height 181.4 ± 8.1 cm; weight 83.4 ± 16.2 kg; all data mean ± SD) participated in the randomised, crossover design, where (i) subjects ingested a high-fat meal alone (control), and (ii) ingested a high-fat meal, preceded by 1 h of moderate exercise. Pulse Wave Velocity (PWV) was examined at baseline, post-exercise, and in the postprandial period. Gastric emptying was measured using the ¹³C-octanoic acid breath test. Measures of venous blood were obtained prior to and following exercise and at 2, 4 and 6 hours post-ingestion. PWV increased (6.5 ± 1.9 m/sec) at 2 (8.9 ± 1.7 m/sec) and 4 hrs (9.0 ± 1.6 m/sec) post-ingestion in the control group (time × group interaction, P < 0.05). PWV was increased at 2 hrs post-ingestion in the control compared to the exercise trial; 8.9 ± 1.7 vs. 6.2 ± 1.5 m/sec (time × group interaction, P < 0.05). Lipid hydroperoxides increased over time (pooled exercise and control data, P < 0.05). Serum triacylglycerols were elevated postprandially (pooled exercise and control data, P < 0.05). There were no changes in gastric emptying, cholesterol, or C-reactive protein levels. These data suggest that acute exercise prior to the consumption of a high-fat meal has the potential to reduce vascular impairments.

Arterial stiffness or endothelial dysfunction as a surrogate marker of vascular risk

The understanding of the pathophysiology of atherosclerosis has advanced greatly in the past decade. Cardiovascular risk factors increase the likelihood of an adverse event by having a detrimental effect on the blood vessel wall. Abnormal interactions among cholesterol, inflammatory mediators, platelets and the vascular wall lead to atherogenesis and cardiac events. In an effort to better understand this process, develop surrogate end points for clinical trials and, ultimately, better risk stratify individuals, a variety of measures of arterial function have been studied. These include measures of endothelial health and arterial compliance. The current paper reviews the various techniques available for the study of vascular health. While not yet routinely used for clinical care, these measurements provide important insights into the pathophysiology and treatment of atherosclerosis.

External mechanical compression reduces regional arterial stiffness

Acute aerobic and resistance exercise has been shown to reduce local muscular artery stiffness in the exercised limb while having no effect on the non-exercised limb. The stimulus for these modulations may be related to local muscular compression of underlying vasculature. The purpose of this study was to examine arterial stiffness before and after a series of locally applied external mechanical compressions designed to be similar to the resistance exercise concentric/eccentric duty cycle. One rapidly inflatable cuff was placed around the upper thigh and another around the calf of the left leg in 18 healthy, young (24 +/- 1 years) participants (female n = 10). Cuffs were inflated to a supra-systolic pressure of 200 mmHg for 4 s followed by a 2-s rapid deflation period. One "set" consisted of 12 inflation/deflation cycles. Six sets of 12 compression cycles were performed. Pulse wave velocity (PWV) was used to measure central stiffness (carotid to femoral) and peripheral stiffness (femoral to dorsalis pedis of both legs) before and 10 min after mechanical compressions. No change was found in central PWV (6.2 +/- 0.3 m/s to 6.3 +/- 0.3 m/s, P > 0.05). Peripheral PWV in the non-compressed leg did not change (8.5 +/- 0.4 m/s to 8.3 +/- 0.4 m/s, P > 0.05) while peripheral PWV in the compressed leg significantly decreased from pre to 10 min post (8.6 +/- 0.3 m/s to 7.6 +/- 0.3 m/s, P < 0.05). External compression reduced local artery stiffness of the compressed limb while having no effect on arterial stiffness of the non-compressed limb or central artery stiffness.

Endothelial function, arterial stiffness and lipid lowering drugs

The endothelium is a dynamic organ that plays a pivotal role in cardiovascular homeostasis. Alteration in endothelial function precedes the development of atherosclerosis and contributes to its initiation, perpetuation and clinical manifestations. It has been suggested that the assessment of endothelial function could represent a barometer of vascular health that could be used to gauge cardiovascular risk. This review summarises the various methods used to assess endothelium-dependent vasodilatation and their potential prognostic implications. In addition, the techniques used to evaluate arterial stiffness are discussed. The latter is to some extent controlled by the endothelium and has been the subject of considerable research in recent years. This paper also discusses the effects of lipid lowering treatment on both endothelial function and arterial stiffness.

On the influence of variation in haemodynamic conditions on the generation and growth of cerebral aneurysms and atherogenesis: a computational model

A risk-factor criterion, based on near-wall haemodynamic conditions, for the assessment of vascular pathology risk is developed and tested. This criterion has its foundation on experimentally observed vascular wall responses to oscillatory and swirling wall shear stress patterns and is applied to the results of computational simulations. We test this model on two anatomically accurate vascular segments, where pathologies are either commonplace or have already been developed, i.e. a healthy carotid bifurcation and a cerebral fusiform aneurysm. In the case of the former, the risk-assessment criterion predicts the emergence of atherosclerosis of the same locations that the disease is usually encountered. In the case of the latter, the risk factor shows increased probability for the appearance of secondary, "baby", aneurysms at certain locations.

Microparticles derived from endothelial progenitor cells in patients at different cardiovascular risk

OBJECTIVES

Exposure to cardiovascular risk factors causes the release of pro-atherogenic microparticles from vascular cells and reduces the number of the atheroprotective endothelial progenitor cells (EPCs). We investigated whether microparticles shedding from EPCs are detectable in cultures of EPCs and in the circulation of subjects with various degrees of cardiovascular risk. We also investigated the relationship of EPCs-derived microparticles to cardiovascular risk factors and aortic stiffness, a marker of cardiovascular risk and impaired vascular repair by EPCs.

METHODS AND RESULTS

We estimated the 10-year Framingham risk score in 105 individuals with various degrees of cardiovascular risk and measured the number of circulating EPCs, EPCs-derived microparticles (CD34+/KDR+) and aortic stiffness. Release of CD34+/KDR+ microparticles was tested in cultures of EPCs exposed to hydrogen-peroxide. CD34+/KDR+ microparticles were found in EPCs cultures incubated with hydrogen-peroxide. Framingham risk was associated with EPCs (r=-0.47, p<0.001) and CD34+/KDR+ microparticles (r=0.56, p<0.001). Low EPCs (r=-0.59, p<0.001) and high CD34+/KDR+ microparticle (r=0.57, p<0.001) levels were predictors of aortic stiffness, independent of the Framingham risk.

CONCLUSIONS

EPCs undergo fragmentation into microparticles when exposed to a pro-apoptotic milieu. Increased microparticle shedding from EPCs may reduce circulating EPCs levels and may thus contribute to increase aortic stiffness beside traditional risk factors.

Characterization of the Upper Limb Arterial Properties during Reactive Hyperemia

The radial artery (RA) pressure waveform is commonly used to reconstruct the central aortic pressure waveform. Because the RA pressure waveform has been used as input to this process, its features that are dependent on the local arterial properties can influence the final reconstructed aortic waveform. In this study, we determined the effects of altered upper limb pulse wave velocity (PWV) and local wave reflection parameters on RA pressure waveform augmentation (RA-AIx). Twenty healthy volunteers (10 men) between the ages of 18 and 35 years of age were recruited. Simultaneous pressure waveforms were acquired using arterial tonometers from the right carotid and the radial arteries, prior to and following tourniquet induced hyperemia. The phase velocities from the pressure wave transfer function were used to estimate the pulse wave velocity (PWV(infinity)), the local reflection coefficient (Gamma) and an estimate of the terminal impedance of the upper limbs, PWV(0+). The RA-AIx was represented as a linear, three-parameter model that included the input (the AIx of the carotid artery pressure waveform, CA-AIx), the Gamma and PWV(infinity) of the arm. Tourniquet induced hyperemia did not alter Gamma but reduced PWV(infinity), and PWV(0+) and increased RA-AIx. Multiple linear regression analysis indicated that RA-AIx was increased by high levels of CA-AIx and PWV(infinity) and decreased by elevated Gamma. The relative weighing of CA-AIx, Gamma and PWV(infinity) on RA-AIx were 3:2:1, respectively. The AIx of RA is determined to an equal extent by the input and local factors. Interpretation of the AIx of the RA and the reconstructed central aortic waveform should be made in the context of this relationship.

Do measures of vascular compliance correlate with endothelial function?

Accumulating evidence demonstrates that measures of vascular compliance correlate with endothelial function in animal models and patients with cardiovascular, metabolic, and kidney diseases. Nitric oxide modulates not only endothelial function, but also vascular compliance. Disruption of normal endothelial function may, at least partially, be responsible for reduced vascular compliance. Thus, nitric oxide may play a pivotal role as a mechanistic link between impaired vascular compliance and endothelial dysfunction.

Age, hypertension and arterial function

1. Ageing exerts a marked effect on the cardiovascular system and, in particular, the large arteries. Using a variety of techniques to assess arterial stiffness, many cross-sectional studies have demonstrated a significant relationship between age and aortic stiffness, although the age-related changes observed in peripheral arteries appear to be less marked. 2. The relationship between arterial stiffness and hypertension is more complex. The distending, or mean arterial, pressure is an important confounder of measurements of arterial stiffness and, therefore, must be taken into consideration when assessing arterial stiffness in hypertensive subjects or investigating the effect of antihypertensive agents. Current methods for correcting for differences in distending pressure involve pharmacological manipulation, statistical correction or mathematical manipulation of stiffness indices. 3. Many studies have provided evidence that both peripheral (muscular) and central (elastic) arteries are stiffer in subjects with mixed (systolic/diastolic) hypertension compared with normotensive subjects. However, it is unclear to what extent differences in mean arterial pressure explain the observed differences in hypertensive subjects. In contrast, isolated systolic hypertension is associated with increased aortic, but not peripheral artery, stiffness, although the underlying mechanisms are somewhat unclear. 4. Traditional antihypertensive agents appear to reduce arterial stiffness, but mostly via an indirect effect of lowering mean pressure. Therefore, therapies that target the large arteries to reduce stiffness directly are urgently required. Agents such as nitric oxide donors and phosphodiesterase inhibitors may be useful in reducing stiffness via functional mechanisms. In addition, inhibitors or breakers of advanced glycation end-product cross-links between proteins, such as collagen and elastin, hold substantial promise.

Endothelial function and hypertension

PURPOSE OF REVIEW

Endothelial dysfunction, in particular a reduced vascular availability of endothelium-derived nitric oxide, has been analysed in numerous experimental and clinical studies as a potential mechanism mediating the adverse vascular effects of hypertension. This paper outlines some notable studies in this dynamic field published recently.

RECENT FINDINGS

The understanding of mechanisms underlying endothelial dysfunction in hypertension has been substantially advanced recently. Increased oxidant stress is thought to represent a major mechanism leading to reduced vascular availability of endothelium-derived nitric oxide. Vascular nicotinamide adenine dinucleotide phosphate oxidases, uncoupled nitric oxide synthase and xanthine oxidase have been identified as major sources of reactive oxygen species in hypertension. Endothelial dysfunction has been implicated in the macrovascular complications of hypertension, such as stroke or myocardial infarction, coronary microvascular dysfunction and increased arterial stiffness, probably at least partly resulting from loss of the antiatherogenic and vasculoprotective effects of endothelium-derived nitric oxide.

SUMMARY

Recent research on endothelial dysfunction supports its clinical significance in hypertension, and has led to important insights into the pathophysiology of the disease. These observations suggest that targeting endothelial dysfunction, in particular reduced nitric oxide availability, would exert beneficial effects in hypertensive patients. This concept needs further evaluation in clinical studies.

Intima-media thickness and arterial stiffness of carotid artery in Korean patients with Behçet's disease

Behçet's disease (BD) is a systemic vasculitis involving diverse sizes of arteries and veins. We performed this study to evaluate the vascular changes by assessment of the arterial stiffness and intima-media thickness (IMT) of carotid artery in Korean patients with BD. Forty-one patients with BD and age-, and sex-matched 53 healthy subjects were recruited in this study. Carotid arterial stiffness and IMT were assessed by using high-resolution B-mode ultrasonography. Arterial stiffness parameters such as carotid arterial distensibility coefficient, stiffness index, and incremental elastic modulus (E(inc)) were significantly increased in BD patients compared with those in healthy subjects, but not in IMT. Positive relationship was noted between age and IMT, whereas age of onset was significantly associated with arterial stiffness in BD. This finding suggests impaired endothelial function before visible structural changes of arterial wall in BD. Age and age of onset may be an independent risk factor for carotid IMT and arterial stiffness, respectively. Further studies in more large populations are required to confirm our results.

Estimated Glomerular Filtration Rate and Urinary Albumin Excretion Are Independently Associated with Greater Arterial Stiffness: The Hoorn Study

Mild renal insufficiency is a risk factor for cardiovascular disease (CVD). Both a decline in GFR and (micro)albuminuria are associated with greater cardiovascular mortality. In ESRD, arterial stiffness, an important cause of CVD, is known to be greater, but few data exist in individuals with mild renal insufficiency or microalbuminuria. This study investigated the association of impaired renal function expressed as lower GFR or greater urinary albumin excretion with arterial stiffness. In a population-based study in 806 individuals (402 men), mean age 68 yr (range 50 to 87), peripheral arterial stiffness (by compliance and distensibility of the carotid, brachial, and femoral arteries and by the carotid elastic modulus [E(inc)]) and central arterial stiffness (by total systemic arterial compliance, carotid-femoral transit time, and aortic augmentation index) were measured ultrasonically. GFR was estimated (eGFR) by the Modification of Diet in Renal Disease (MDRD) formula. Urinary albumin excretion was expressed as urinary albumin/creatinine ratio (UACR). eGFR was 60.6 +/- 11.1 ml/min per 1.73 m(2). Median UACR was 0.57 mg/mmol (range 0.1 to 26.6). After adjustment for age, mean arterial pressure (MAP), gender, and glucose tolerance status (GTS), each 5-ml/min per 1.73 m(2) lower eGFR was associated with a lower distensibility coefficient of the carotid (regression coefficient beta -0.20 10(-3)/kPa; 95% confidence interval [CI] -0.34 to -0.07 10(-3)/kPa) and brachial artery (-0.15 10(-3)/kPa; 95% CI -0.28 to -0.03 10(-3)/kPa) and a greater carotid E(inc) (0.02 kPa; 95% CI 0.0004 to 0.04 kPa). No statistically significant association was found of eGFR with other arterial stiffness indices. After adjustment for age, MAP, gender, and GTS, a greater UACR (per quartile) was associated with a greater E(inc) (0.03 kPa; 95% CI 0.001 to 0.07 kPa) and a trend to a lower distensibility coefficient (-0.24 10(-3)/kPa; 95% CI -0.49 to 0.02 10(-3)/kPa) of the carotid artery. After adjustment for age, MAP, gender, and GTS, a greater UACR (per quartile) was in addition associated with a shorter carotid-femoral transit time (-1.67 ms; 95% CI -3.24 to -0.10 ms). These associations were not substantially changed by mutual adjustment for eGFR and UACR. In individuals with mild renal insufficiency, both a lower eGFR and a greater albumin excretion, even below levels that are considered to reflect microalbuminuria, are independently associated with greater arterial stiffness. Moreover, these associations were mutually independent. These findings may explain, in part, why eGFR and microalbuminuria are associated with greater risk for CVD and suggest that amelioration of arterial stiffness could be a target of intervention.

Human arterial responses to isometric exercise: the role of the muscle metaboreflex

The effects of exercise on the distensibility of large and medium-sized arteries are poorly understood, but can be attributed to a combination of local vasodilator effects of exercise opposed by sympathetic vasoconstrictor tone. We sought to examine this relationship at the conduit artery level, with particular reference to the role of the sympatho-excitatory muscle metaboreflex. The effect of maintained muscle metaboreflex activation on a previously passive or exercised limb femoral artery was investigated. A total of ten healthy volunteers performed 2 min of isometric ankle plantar-flexion at 40% MVC (maximal voluntary force), in conjunction with 2 min of either non-ischaemic isometric HG (handgrip; control condition) or IHG (ischaemic HG) at 40% MVC. IHG was followed by 2 min of PECO (post-exercise circulatory occlusion) to maintain muscle metaboreflex activation. FTPWV [femoral-tibial PWV (pulse wave velocity)] was measured in the exercised or contralateral limb at baseline and immediately following calf exercise. BP (blood pressure) and HR (heart rate) were measured continuously throughout. In the HG condition, BP and HR returned promptly to baseline post-exercise, whereas exercised leg FTPWV was decreased (less stiff) by 0.6 m/s (P<0.05) and the non-exercised leg PWV was not changed from baseline. PECO caused a sustained increase in BP, but not HR, in the IHG condition. Contralateral leg PWV increased (stiffened) during PECO by 0.9 m/s (P<0.05), whereas exercised limb FTPWV was not changed from baseline. In conclusion, muscle metaboreflex activation causes a systemic stiffening of the arterial tree, which can overcome local exercise-induced decreases in arterial PWV.

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.

Nitric oxide in hypertension

Hypertension is a major risk factor for cardiovascular disease, and reduction of elevated blood pressure significantly reduces the risk of cardiovascular events. Endothelial dysfunction, which is characterized by impairment of nitric oxide (NO) bioavailability, is an important risk factor for both hypertension and cardiovascular disease and may represent a major link between the conditions. Evidence suggests that NO plays a major role in regulating blood pressure and that impaired NO bioactivity is an important component of hypertension. Mice with disruption of the gene for endothelial NO synthase have elevated blood pressure levels compared with control animals, suggesting a genetic component to the link between impaired NO bioactivity and hypertension. Clinical studies have shown that patients with hypertension have a blunted arterial vasodilatory response to infusion of endothelium-dependent vasodilators and that inhibition of NO raises blood pressure. Impaired NO bioactivity is also implicated in arterial stiffness, a major mechanism of systolic hypertension. Clarification of the mechanisms of impaired NO bioactivity in hypertension could have important implications for the treatment of hypertension.

Aspects of nitric oxide in health and disease: a focus on hypertension and cardiovascular disease

Nitric oxide (nitrogen monoxide) (NO) plays an important role in a wide range of physiologic processes. A major mediator of endothelial function, NO regulates vasodilatory and antithrombotic actions in the vasculature and plays a role in reproductive functions, bronchodilation, bone formation, memory, insulin sensitivity, and gastrointestinal relaxation. NO is formed from NO synthase. Impaired NO bioactivity is strongly associated with endothelial dysfunction and cardiovascular disease, but is also implicated in a broad range of other disorders, including pulmonary hypertension, insulin resistance, erectile dysfunction, and preeclampsia. Numerous therapies designed to target NO are being investigated and developed, including NO donors and stimulants. The recent African-American Heart Failure Trial (A-HeFT) showed that the NO donor isosorbide dinitrate, combined with the vasodilator hydralazine, significantly reduced morbidity and mortality in black patients with moderate-to-severe heart failure. Antihypertensive drugs, including angiotensin-converting enzyme inhibitors, calcium channel blockers, and third-generation beta-blockers, are NO stimulants that have demonstrated significant improvement of endothelial function and NO bioactivity. Other cardiovascular therapies that may improve NO bioactivity include statins, l-arginine, and nonpharmacologic approaches such as exercise and dietary changes.

Coronary hemodynamics and atherosclerotic wall stiffness: a vicious cycle

Local hemodynamic environment, including low shear stress and increased tensile stress, determines the localization, growth and progression of coronary atherosclerosis. As atherosclerotic lesions evolve, the diseased coronary arteries undergo local quantitative and qualitative changes in their wall, and progressively become stiff. Arterial stiffening amplifies the atherogenic local hemodynamic environment, initiating a self-perpetuating vicious cycle, which drives the progression of atherosclerosis and the formation of atherosclerotic plaque. In vivo evidence indicates that endothelial dysfunction is associated with arterial stiffness, an association that creates a challenging perspective of utilizing stiffness as an early marker of endothelial dysfunction and future atherosclerosis. Coronary stiffening is also associated with vascular remodeling, which is a major determinant of the natural history of atherosclerotic plaques. Thus, arterial stiffness may constitute a useful marker for the identification of the remodeling pattern, in particular expansive remodeling, which is closely associated with high-risk plaques. The early identification of endothelial dysfunction, or a high-risk plaque may enable the early adoption of preventive measures to improve endothelial function, or justify pre-emptive local interventions in high-risk regions to prevent future acute coronary syndromes. Further experimental and perspective clinical studies are needed for the investigation of these perspectives, whereas the development of new modalities for non-invasive and reliable assessment of coronary stiffness is anticipated to serve these studies.

The effect of acute aerobic exercise on pulse wave velocity and oxidative stress following postprandial hypertriglyceridemia in healthy men

Oxidative stress is postulated to be responsible for the postprandial impairments in vascular function. The purpose of this study was to measure pulse wave velocity (PWV) and markers of postprandial oxidative stress before and after an acute bout of moderate exercise. Ten trained male subjects (age 21.5 +/- 2.5 years, VO2 max 58.5 +/- 7.1 ml kg(-1) min(-1)) participated in a randomised crossover design: (1) high-fat meal alone (2) high-fat meal followed 2 h later by a bout of 1 h moderate (60% max HR) exercise. PWV was examined at baseline, 1, 2, 3, and 4 h postprandially. Blood Lipid hydroperoxides (LOOHs), Superoxide dismutase (SOD) and other biochemical markers were measured. PWV increased at 1 h (6.49 +/- 2.1 m s(-1)), 2 h (6.94 +/- 2.4 m s(-1)), 3 h (7.25 +/- 2.1 m s(-1)) and 4 h (7.41 +/- 2.5 m s(-1)) respectively, in the control trial (P < 0.05). There was no change in PWV at 3 h (5.36 +/- 1.1 m s(-1)) or 4 h (5.95 +/- 2.3 m s(-1)) post ingestion in the exercise trial (P > 0.05). LOOH levels decreased at 3 h post ingestion in the exercise trial compared to levels at 3 h (P < 0.05) in the control trial. SOD levels were lower at 3 h post ingestion in the control trial compared to 3 h in the exercise trial (0.52 +/- 0.05 vs. 0.41 +/- 0.1 units mul(-1); P < 0.05). These findings suggest that a single session of aerobic exercise can ameliorate the postprandial impairments in arterial function by possibly reducing oxidative stress levels.

Arterial elasticity identified by pulse wave analysis and its relation to endothelial function in patients with coronary artery disease

Patients with coronary artery disease (CAD) have impaired endothelial function. Arterial elasticity is modulated by endothelial function. The association between arterial elasticity and endothelial function has not been reported in patients with CAD. The present study was designed to investigate whether endothelial dysfunction contributes to impaired arterial elasticity. Thirty patients with CAD and 30 control subjects were recruited. Large and small artery elasticity indices were non-invasively assessed using pulse wave analysis. Brachial artery endothelium-dependent and -independent function were assessed by vascular response to flow-mediated vasodilation (FMD) and sublingual nitroglyceride (NTG), respectively. C1 large artery elasticity index was not different in the CAD group compared with the control group. However, C2 small artery elasticity index was significantly reduced in the CAD group compared with the control group. Flow-mediated vasodilation (FMD) was also impaired in the CAD group compared with the control group. Flow-mediated vasodilation (FMD) in the brachial artery correlated with C2 small arterial elasticity index. But NTG-mediated brachial artery vasodilation was similar between the two groups. The present findings suggest that the patients with CAD have reduced C2 small arterial elasticity index and impaired FMD. Endothelial dysfunction is involved in diminished arterial elasticity, suggesting that C2 small arterial elasticity index is a novel surrogate measure for the clinical evaluation of endothelial function.

Angiotensin Receptor Blockade Improves Vascular Compliance in Healthy Normotensive Elderly Individuals: Results From a Randomized Double‐Blind Placebo‐Controlled Trial

The renin-angiotensin system (RAS) may play a role in vascular aging. The authors hypothesized that blockade of the angiotensin II type 1 receptor with an angiotensin receptor blocker in healthy elderly subjects improves vascular compliance and endothelial function. Thirty-five healthy elderly subjects were randomized to valsartan or placebo in a double-blind crossover study after baseline testing for pulse wave velocity, aortic augmentation index, and brachial artery flow-mediated dilation. Angiotensin II type 1 receptor blockade with valsartan improved vascular compliance but not flow-mediated dilation. Changes in pulse wave velocity with valsartan were correlated with change in central systolic blood pressure and pulse pressure and remained associated on multivariate analysis. Change in pulse wave velocity after adjusting for degree of blood pressure change, age, and sex remained correlated with assignment to the angiotensin receptor blocker but not placebo. These data suggest that angiotensin II type 1 receptor blockade improves aging-related vascular compliance without alterations in flow-mediated dilation. Mechanisms regulating compliance and endothelial function are complex and may not necessarily converge in aging.

Chronic nitric oxide synthase inhibition blunts endothelium-dependent function of conduit coronary arteries, not arterioles

Current literature suggests that chronic nitric oxide synthase (NOS) inhibition has differential effects on endothelium-dependent dilation (EDD) of conduit arteries vs. arterioles. Therefore, we hypothesized that chronic inhibition of NOS would impair EDD of porcine left anterior descending (LAD) coronary arteries but not coronary arterioles. Thirty-nine female Yucatan miniature swine were included in the study. Animals drank either tap water or water with N(G)-nitro-L-arginine methyl ester (L-NAME; 100 mg/l), resulting in control and chronic NOS inhibition (CNI) groups, respectively. Treatment was continued for 1-3 mo (8.3 +/- 0.6 mg x kg(-1) x day(-1)). In vitro EDD of coronary LADs and arterioles was assessed via responses to ADP (LADs only) and bradykinin (BK), and endothelium-independent function was assessed via responses to sodium nitroprusside (SNP). Chronic NOS inhibition diminished coronary artery EDD to ADP and BK. Incubating LAD rings with L-NAME decreased relaxation responses of LADs from control pigs but not from CNI pigs such that between-group differences were abolished. Neither indomethacin (Indo) nor sulfaphenazole incubation significantly affected relaxation responses of LAD rings to ADP or BK. Coronary arteries from CNI pigs showed enhanced relaxation responses to SNP. In contrast to coronary arteries, coronary arterioles from CNI pigs demonstrated preserved EDD to BK and no increase in dilation responses to SNP. L-NAME, Indo, and L-NAME + Indo incubation did not result in significant between-group differences in arteriole dilation responses to BK. These results suggest that although chronic NOS inhibition diminishes EDD of LAD rings, most likely via a NOS-dependent mechanism, it does not affect EDD of coronary arterioles.

Haemodynamics and wall remodelling of a growing cerebral aneurysm: A computational model

We have developed a computational simulation model for investigating an often postulated hypothesis connected with aneurysm growth. This hypothesis involves a combination of two parallel and interconnected mechanisms: according to the first mechanism, an endothelium-originating and wall shear stress-driven apoptotic behavior of smooth muscle cells, leading to loss of vascular tone is believed to be important to the aneurysm behavior. Vascular tone refers to the degree of constriction experienced by a blood vessel relative to its maximally dilated state. All resistance and capacitance vessels under basal conditions exhibit some degree of smooth muscle contraction that determines the diameter, and hence tone, of the vessel. The second mechanism is connected to the arterial wall remodeling. Remodeling of the arterial wall under constant tension is a biomechanical process of rupture, degradation and reconstruction of the medial elastin and collagen fibers. In order to investigate these two mechanisms within a computationally tractable framework, we devise mechanical analogues that involve three-dimensional haemodynamics, yielding estimates of the wall shear stress and pressure fields and a quasi-steady approach for the apoptosis and remodeling of the wall. These analogues are guided by experimental information for the connection of stimuli to responses at a cellular level, properly averaged over volumes or surfaces. The model predicts aneurysm growth and can attribute specific roles to the two mechanisms involved: the smooth muscle cell-related loss of tone is important to the initiation of aneurysm growth, but cannot account alone for the formation of fully grown sacks; the fiber-related remodeling is pivotal for the latter.

Measurement of the Brachial-Ankle Pulse Wave Velocity and Flow-Mediated Dilatation in Young, Healthy Smokers

The brachial-ankle pulse wave velocity (PWV) is a quick test which adequately estimates arterial stiffness. Because flow-mediated dilatation (FMD) of the brachial artery assesses an essential endothelial function, we tested the hypothesis that the brachial-ankle PWV could reflect the early stages of endothelial dysfunction caused by smoking in young, healthy subjects. Fifty-seven healthy subjects (13 females and 44 males; mean 29.9+/-5.6 years) were enrolled. Twenty-six of the subjects (30.4+/-5.7 years) were active smokers, with a mean cumulative nicotine consumption of 10.0+/-8.6 pack/years, and thus were assigned to the smoking group. Thirty-one subjects without a history of smoking (29.5+/-5.5 years) were assigned to the non-smoking group. The brachial-ankle PWV and arterial blood pressure were simultaneously measured using a recently established, non-invasive automatic device (model BP-203RPE; Nihon Colin, Tokyo, Japan). Endothelium-dependent FMD was induced by reactive hyperemia, while endothelium-independent vasodilation of the brachial artery was induced by administration of sublingual nitroglycerin spray. The FMD was lower in the smoking group than in the non-smoking group (p<0.05). There was no significant difference between the two groups with respect to the brachial-ankle PWV. In the non-smoking group, multiple stepwise regression analysis revealed that FMD was predicted by the systolic blood pressure (F=16.351). In the smoking group, statistical analysis revealed that FMD was independently predicted by either the brachial-ankle PWV (F=8.108) or the subject's age (F=4.381). Our results suggest that a reduction in FMD is closely associated with the early stages of endothelial dysfunction caused by cigarette smoking in young, healthy subjects, which is at least partly reflected by the PWV value.