Endothelial function and dysfunction. Part I: Methodological issues for assessment in the different vascular beds: a statement by the Working Group on Endothelin and Endothelial Factors of the European Society of Hypertension

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.

Endothelial dysfunction in patients with antiphospholipid syndrome assessed with positron emission tomography

BACKGROUND

There is limited knowledge about endothelial dysfunction in patients with primary antiphospholipid syndrome (PAPS). The purpose of this study was to evaluate endothelial function in patients with PAPS assessed by positron emission tomography.

METHODS AND RESULTS

A 3-phase protocol--rest, cold pressor test (CPT), and adenosine positron emission tomography with nitrogen 13 ammonia--was used in 18 patients with PAPS and 18 healthy volunteers (HVs). Myocardial blood flow (MBF) was measured in each phase, with calculation of the endothelial-dependent vasodilation index, the increase in the MBF in response to CPT, and the myocardial flow reserve. An important trend was found in the myocardial flow reserve (2.76 +/- 1.04 in PAPS group vs 3.27 +/- 0.72 in HV group, P > .05), in the endothelial-dependent vasodilation index (1.19 +/- 0.31 in PAPS group vs 1.55 +/- 0.37 in HV group, P < .05), and in the percent change in the MBF in response to CPT (from rest) (19% +/- 31% in PAPS group vs 55% +/- 37% in HV group, P < .05).

CONCLUSION

The CPT results obtained in this study showed that the PAPS patients studied have endothelial dysfunction.

Association of endothelial function and vascular data with LDL-c and HDL-c in a homogeneous population of middle-aged, healthy military men: Evidence for a critical role of optimal lipid levels

BACKGROUND

Modifying lipids levels underpins atherosclerosis prevention. Flow-mediated dilation (FMD) could advise which patients to treat and to what extent. Little is known about the influence of near-normal lipid levels on the endothelium and the mechanisms related to different lipid fractions. We studied associations between FMD and lipids, focusing on normal lipid levels.

METHODS

An age-homogeneous sample of 171 healthy, untreated military men (mean age 35.5+/-1.1 years) was studied: serum lipid determination and brachial artery ultrasound with a forearm ischemia cuff and automated measurement were performed. NCEP-ATP III groups were used.

RESULTS

Significantly smaller vessel diameters were found among individuals with high HDL-c (4.10 mm vs. 4.24 mm), optimal LDL-c (4.00 mm vs. 4.22 mm), and normal triglycerides (<150 mg/dl) (4.15 mm vs. 4.31 mm). Basal diameter correlated significantly with HDL-c and triglycerides. There were significant differences in FMD between low HDL-c compared to the rest (4.13% vs. 5.07%) and between optimal and near-optimal LDL-c compared to the rest (5.28% vs. 4.56%). HDL-c and LDL-c correlated with FMD. The inverse relation of high LDL-c and FMD is partially due to a decreased stimulus. Besides, stimulus heterogeneity may mask HDL-c link with FMD.

CONCLUSION

Those subjects naturally (not pharmacologically) in the healthy tail-end of the lipid distributions have the best endothelial function and smaller vessels. Functional vascular remodeling might precede anatomical remodeling and, in early stages, vessel size should be considered a risk indicator rather than an atherosclerotic sign. Furthermore, controlling the stimulus seems necessary for detecting the relationship between HDL-c and FMD, and should be performed regularly.

Endothelial function in familial combined hyperlipidaemia

BACKGROUND

Familial combined hyperlipidaemia (FCH) is characterized by dyslipidaemia, visceral obesity and insulin resistance, and is associated with an increased intima-media thickness (IMT) and an increased risk for cardiovascular disease. In the present study, we investigated whether FCH is associated with early functional vascular wall changes, as represented by endothelial dysfunction, and we determined whether endothelial function in FCH is related to any of the cardiovascular risk factors associated with the FCH phenotype, or to the (increased) IMT.

DESIGN

In 98 patients with FCH [mean age 51 (48-54) years, 43% male] and 230 unaffected relatives [mean age 44 (42-46) years, 48% male], venous blood was drawn in the fasting state after discontinuation of lipid lowering drugs for at least 4 weeks (if used). IMT was measured by B-mode ultrasound and endothelial function was assessed by determination of flow mediated dilation (FMD) and by measurement of plasma concentrations of various soluble adhesion molecules, including soluble vascular cell adhesion molecule (sVCAM), soluble intercellular adhesion molecule (sICAM) and soluble E-selectin.

RESULTS

There were no significant differences between FCH patients and their non-affected relatives in FMD [2.9 (2.3-3.6%) vs. 2.8 (2.5-3.2%)] or in the plasma concentrations of the various adhesion molecules. None of the individual clinical and biochemical cardiovascular risk factors was an independent predictor of endothelial function in patients with FCH, nor was IMT. However, subgroup analysis revealed that IMT was an independent and powerful predictor of FMD in subjects with carotid artery plaques (St. beta = 4.11, P < 0.004), whereas IMT was no significant predictor in subjects without plaques.

CONCLUSIONS

FCH patients have no impaired endothelial function when compared to their unaffected relatives. IMT is an important predictor of FMD when advanced morphological wall changes are present. Our results question the value of FMD measurements for cardiovascular risk stratification in populations with an anticipated high cardiovascular risk.

Effects of low- and high-advanced glycation endproduct meals on macro- and microvascular endothelial function and oxidative stress in patients with type 2 diabetes mellitus

BACKGROUND

An advanced glycation endproducts (AGEs)-rich diet induces significant increases in inflammatory and endothelial dysfunction markers in type 2 diabetes mellitus (T2DM).

OBJECTIVE

The aim was to investigate the acute effects of dietary AGEs on vascular function in T2DM patients.

DESIGN

Twenty inpatients with T2DM [x (+/-SEM) age: 55.4 +/- 2.2 y; glycated hemoglobin: 8.8 +/- 0.5%] were investigated. In a randomized crossover design, the effects of a low-AGE (LAGE) and high-AGE (HAGE) meal on macrovascular [by flow-mediated dilatation (FMD)] and microvascular (by Laser-Doppler flowmetry) function, serum markers of endothelial dysfunction (E-selectin, intracellular adhesion molecule 1, and vascular cell adhesion molecule 1), oxidative stress, and serum AGE were assessed. The meals had identical ingredients but different AGE amounts (15.100 compared with 2.750 kU AGE for the HAGE and LAGE meals, respectively), which were obtained by varying the cooking temperature and time. The measurements were performed at baseline and 2, 4, and 6 h after each meal.

RESULTS

After the HAGE meal, FMD decreased by 36.2%, from 5.77 +/- 0.65% (baseline) to 3.93 +/- 0.48 (2 h), 3.70 +/- 0.42 (4 h), and 4.42 +/- 0.54% (6 h) (P<0.01 for all compared with baseline). After the LAGE meal, FMD decreased by 20.9%, from 6.04 +/- 0.68% (baseline) to 4.75 +/- 0.48% (2 h), 4.69 +/- 0.51% (4 h), and 5.62 +/- 0.63% (6 h), respectively (P<0.01 for all compared with baseline; P<0.001 for all compared with the HAGE meal). This impairment of macrovascular function after the HAGE meal was paralleled by an impairment of microvascular function (-67.2%) and increased concentrations of serum AGE and markers of endothelial dysfunction and oxidative stress.

CONCLUSIONS

In patients with T2DM, a HAGE meal induces a more pronounced acute impairment of vascular function than does an otherwise identical LAGE meal. Therefore, chemical modifications of food by means of cooking play a major role in influencing the extent of postprandial vascular dysfunction.

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.

Nitric oxide in the pathogenesis of cardiac disease

Endothelial dysfunction is characterized by a vasoconstrictive and prothrombotic state in the vasculature; it plays a role in all stages of cardiac disease and is a significant independent predictor of cardiovascular outcomes. Nitric oxide (NO) performs multiple biologic activities in the endothelium, including vasodilation and antithrombotic actions. Reduced NO bioactivity is a major component of endothelial dysfunction. Impaired NO bioactivity is an important factor in the pathogenesis of atherosclerosis and in the metabolic syndrome. The functions of NO bioactivity in the heart go well beyond those in the endothelium, as all 3 NO synthase (NOS) isoforms-endothelial NOS, neuronal NOS, and inducible NOS-are expressed in cardiac myocytes and mediate systolic, diastolic, and chronotropic cardiac functions. Impairment of NO bioactivity is a pathogenic factor in various forms of cardiac disease. Although these findings support the potential use of NO-targeted therapies for treatment of cardiac disease, the complexities of the biologic actions of NO in the vasculature and heart are such that development of therapies is still largely in the preliminary stages.

What is the role of non-invasive measurements of atherosclerosis in individual cardiovascular risk prediction?

Primary prevention of CVD (cardiovascular disease) is mainly based on the assessment of individual cardiovascular risk factors. However, often, only the most important (conventional) cardiovascular risk factors are determined, and every level of risk factor exposure is associated with a substantial variation in the amount of atherosclerosis. Measuring the effect of risk factor exposure over time directly in the vessel might (partially) overcome these shortcomings. Several non-invasive imaging techniques have the potential to accomplish this, each of these techniques focusing on a different stage of the atherosclerotic process. In this review, we aim to define the current role of various of these non-invasive measurements of atherosclerosis in individual cardiovascular risk prediction, taking into account the most recent insights about validity and reproducibility of these techniques and the results of recent prospective outcome trials. We conclude that, although the clinical application of FMD (flow-mediated dilation) and PWA (pulse wave analysis) in individual cardiovascular risk prediction seems far away, there may be a role for PWV (pulse wave velocity) and IMT (intima-media thickness) measurements in the near future.

Effect of losartan, compared with atenolol, on endothelial function and oxidative stress in patients with type 2 diabetes and hypertension

OBJECTIVE

It has been shown that angiotensin-converting enzyme inhibition or angiotensin receptor blockade may improve endothelial dysfunction, an early manifestation of atherosclerosis, in patients with diabetes. Whether this protective effect is mediated through blood pressure-lowering effects or other specific mechanisms such as a reduction in oxidative stress is not clear. We investigated the influence of losartan, compared with atenolol, on endothelial function and oxidative stress in patients with type 2 diabetes and hypertension.

METHODS

Thirteen patients were included in this randomized, double-blind, crossover study; they received losartan 50 mg twice daily for 4 weeks followed by atenolol 50 mg twice daily or vice versa. Concomitant medication with renin-angiotensin blocking agents or beta-blockers was withdrawn, whereas other medication remained unchanged. At baseline and after each treatment period, flow-mediated dilation of the brachial artery and oxidative stress were measured in serum samples.

RESULTS

Flow-mediated dilation was increased significantly after 4 weeks' treatment with losartan (3.4 +/- 0.44%) compared with atenolol (2.58 +/- 0.42%; P = 0.01). 8-Isoprostanes, a marker of oxidative stress, were significantly reduced in the losartan group compared with baseline (0.039 +/- 0.007 versus 0.067 +/- 0.006 ng/ml; P = 0.01), but did not differ from baseline with atenolol. Glucose, hemoglobin A1c, highly sensitive C-reactive protein, lipids and systolic blood pressure remained unaltered, whereas diastolic blood pressure tended to be lower in the atenolol group.

CONCLUSIONS

This study demonstrates that losartan significantly improved endothelial function in type 2 diabetes patients with hypertension compared with atenolol. This must be independent of the blood pressure-lowering effect of losartan and is probably caused by an antioxidative effect of the angiotensin receptor blocker.

Nitric oxide mechanisms in the pathogenesis of global risk

Identification and management of cardiovascular risk factors, such as hypertension, diabetes mellitus, and dyslipidemia, is essential not only for prevention of cardiovascular disease, but also for slowing the progression of existing cardiovascular disease. A major underlying mechanism that links various cardiovascular risk factors and manifestations of cardiovascular disease is endothelial dysfunction, characterized by impaired nitric oxide bioactivity. Oxidative stress is an important cause of impaired nitric oxide bioactivity, and a major pathogenic mechanism of atherosclerosis. Several pharmacologic therapies, including angiotensin-converting enzyme inhibitors, calcium channel blockers, statins, and the vasodilating beta blocker nebivolol, have been shown to enhance nitric oxide bioactivity and improve endothelial function. This effect may help explain the cardioprotective benefits of these agents and may stimulate further use of nitric oxide modulation for the treatment of cardiovascular risk factors and manifestations of cardiovascular disease.

Inflammation and endothelial activation are linked to renal function in long-term kidney transplantation

The aim of this study was to investigate the relationships between inflammation and adhesion molecules in long-term kidney transplantation. We measured serum concentrations of tumor necrosis factor-alpha (TNFalpha) and intercellular and vascular cell adhesion molecules (ICAM-1 and VCAM-1) in 35 renal transplant recipients (mean age of transplantation 5 +/- 3 years) and in 35 chronic renal insufficiency (CRI) patients; twenty-six healthy subjects were enrolled as controls. Transplanted showed higher values than controls of TNFalpha (P < 0.0001), ICAM-1 (P < 0.0001), and VCAM-1 (P < 0.0001). CRI group as well exhibited higher concentrations than controls of TNFalpha (P < 0.0001), ICAM-1 (P < 0.0001), and VCAM-1 (P < 0.0001). Transplanted and CRI patients had similar blood pressure and renal function levels, and TNFalpha, ICAM-1, and VCAM-1 were not significantly different in the two groups. In transplanted group ICAM-1, VCAM-1, and TNFalpha correlated negatively and independently with glomerular filtration rate (GFR) -P < 0.00001 for all. TNFalpha as well correlated with ICAM-1 and VCAM-1 (P < 0.001, respectively). In CRI group, TNFalpha correlated with serum creatinine, ICAM-1, and VCAM-1 (P = 0.01 for all). In conclusion, in long-term renal transplantation, the level of kidney function and both inflammation and endothelial activation are closely related. In fact, the multiple regression analysis demonstrated that the level of kidney insufficiency and the levels of the studied molecules were independently associated.

C-reactive protein and intercellular adhesion molecule-1 are stronger predictors of oxidant stress than blood pressure in established hypertension

BACKGROUND

Oxidant stress is implicated in the pathogenesis of atherosclerosis in cardiovascular diseases. Our aim was to test oxidative stress, as 8-iso-prostaglandin F2alpha (8-iso-PGF2alpha), and its relationship with inflammation markers C-reactive protein (CRP) and tumour necrosis factor-alpha (TNFalpha), and endothelial activation assayed as soluble intercellular adhesion molecule (ICAM)-1 and vascular cell adhesion molecule (VCAM)-1 in essential hypertension.

METHODS

In 216 essential hypertensive patients and 55 healthy control individuals, plasma levels of high-sensitivity CRP and TNFalpha, 8-iso-PGF2alpha, ICAM-1 and VCAM-1 were measured in basal conditions. Moreover, basal and 24-h ambulatory blood pressure monitoring measurements were obtained.

RESULTS

Essential hypertensive patients showed higher levels of 8-iso-PGF2alpha (P < 0.0001), high-sensitivity CRP, TNFalpha, ICAM-1 and VCAM-1 (P < 0.001, respectively) than control individuals. In control individuals, 8-iso-PGF2alpha correlated only with high-sensitivity CRP (P < 0.001). In essential hypertensive patients, 8-iso-PGF2alpha correlated with high-sensitivity CRP (P < 0.000001), TNFalpha (P < 0.0001), ICAM-1 (P < 0.000001), VCAM-1 (P < 0.0001) and blood pressure. The multiple regression analysis considering 8-iso-PGF2alpha as the dependent variable showed that in essential hypertensive patients the independent predictors of 8-iso-PGF2alpha were ICAM-1, high-sensitivity CRP (P < 0.00001, respectively), and TNFalpha (P = 0.028).

CONCLUSION

Our findings demonstrate that oxidant stress is increased in essential hypertension, and relates to inflammation and endothelial activation. Factors other than blood pressure are stronger predictors of oxidant stress.

Endothelial dysfunction in psoriatic arthritis patients without clinically evident cardiovascular disease or classic atherosclerosis risk factors

OBJECTIVE

To determine whether endothelial dysfunction was present in a cohort of patients with psoriatic arthritis (PsA) without overt cardiovascular disease or classic cardiovascular risk factors attended to in a community hospital.

METHODS

Fifty patients with PsA who fulfilled the Moll and Wright criteria were recruited from Hospital Xeral-Calde (Lugo, Spain). Patients seen during the period of recruitment who had classic cardiovascular risk factors or had experienced cardiovascular or cerebrovascular events were excluded. Fifty healthy matched controls were also studied. In all patients and controls, endothelial function was determined by measuring flow-mediated endothelial dependent vasodilatation (FMD%) and endothelial independent vasodilatation (GTN%) by brachial ultrasonography.

RESULTS

FMD% was significantly impaired in patients compared with controls (mean, median [range] 6.3%, 6.1% [0.3-13.4%] versus 8.2%, 8.2% [0.0-21.2%]; P = 0.008). However, no significant difference existed between patients and controls in GTN% or baseline diameter. A significant correlation between C-reactive protein level and erythrocyte sedimentation rate at the time of disease diagnosis and FMD% was found (P < 0.04). No significant FMD% and GTN% differences were observed when patients with PsA with polyarticular pattern were compared with the remaining patients with PsA.

CONCLUSION

The present study demonstrates that patients with PsA without cardiovascular risk factors or clinically evident cardiovascular disease also exhibit endothelial dysfunction. These observations provide a basis for the potential association between PsA and atherosclerotic disease.

Measurement of Flow-Mediated Vasodilation of the Brachial Artery A Comparison of Measurements in the Seated and Supine Positions

BACKGROUND

Measurement of flow-mediated vasodilation (FMD) is used to assess endothelial function in humans and according to the guidelines, subjects must remain supine during the study. However, measurement of FMD while seated would be more comfortable and convenient for patients, so the purpose of this study was to determine the effect of the patient's position on FMD results.

METHODS AND RESULTS

High-resolution ultrasonography, a linear array transducer (13 MHz) and an arm-holding device were used to measure arterial diameter in response to reactive hyperemia (FMD, cuff inflated to 50 mmHg above systolic blood pressure for 5 min) and in response to sublingual nitroglycerine (NTG, 75 microg) in 31 subjects, which included those with cardiovascular diseases. There was no significant difference between basal or peak hyperemic blood flow in the seated or supine position. Basal brachial artery diameter, FMD and vascular response to NTG were similar in both positions (basal diameter: 3.8+/-0.4 vs 3.9+/-0.4 mm, FMD: 7.3+/-4.3% vs 7.2+/-4.5%, NTG: 13.1+/-5.1% vs 12.8+/-5.6%).

CONCLUSIONS

The findings suggest that measurement of FMD in the seated position is as useful as measuring it in the supine position for assessing endothelial function. This flexibility of position is better for patients and physicians, and should lead to more widespread measurement of FMD.

Non-Invasive Assessment of Endothelial Function

OBJECTIVES

The purpose of this study was to compare 3 non-invasive techniques for assessment of endothelial function in adults and children and evaluate their utility in acute inflammation.

BACKGROUND

Endothelial dysfunction is a key early event in pre-clinical atherosclerosis. Flow-mediated dilation (FMD), although the established technique, is expensive and technically demanding. Measurements of vascular responses to inhaled salbutamol by pulse wave analysis (PWA) or pulse contour analysis (PCA) are potential alternatives.

METHODS

Sixteen adults (mean age 28 years, range 18 to 39) and 16 children (mean age 13 years, range 7 to 17) underwent concurrent vascular function testing on 2 occasions with ultrasound, PWA, and PCA. Eighteen men were also studied before and after typhoid vaccination.

RESULTS

Reproducibility of FMD was high in adults and children (coefficient of variation [CV] = 7.1 and 6.3, respectively). Salbutamol responses were more variable with PWA (adults CV = 11.5, children CV = 17.1) and PCA particularly in children (adults CV = 18.2, children CV = 36.3). Flow-mediated dilation (p < 0.001) and PWA with salbutamol (p = 0.03) responses fell after typhoid vaccination, and PCA (p = 0.7) was unchanged.

CONCLUSIONS

Vascular dysfunction during acute inflammation can be measured by FMD and by PWA with salbutamol. Flow-mediated dilation is less variable than PWA. Variability of PCA makes this technique currently unsuited to serial measures of endothelial function in children. Flow-mediated dilation remains the most reproducible method.

Clinical assessment of endothelial dysfunction: combine and rule

PURPOSE OF REVIEW

To briefly survey the literature for the past 2-3 years on the subject of diagnostic and prognostic markers of endothelial cell dysfunction.

RECENT FINDINGS

Established and emerging techniques to detect endothelial cell dysfunction are divided into two large families: (1) functional and structural markers of endothelial cell dysfunction, and (2) surrogate markers of endothelial cell dysfunction. The first category includes high-resolution Doppler studies of conduit arteries, laser Doppler flowmetry of cutaneous microvasculature, and measurements of arterial stiffness and intima: media thickness. The second category of tests provides brief descriptions of detection of oxidative stress, inflammation, coagulation abnormalities, circulating endothelial cells and microparticles. I also focus on integration of various techniques and some novel genomic, proteomic and metabolomic tests.

SUMMARY

This snapshot of existing and emerging technologies diagnosing endothelial cell dysfunction is intended to provide the foundation for the future (a) development of personalized noninvasive screening of endothelial function, and (b) delineation of preclinical diagnostic biomarkers heralding cardiovascular complications.

Uric acid restores endothelial function in patients with type 1 diabetes and regular smokers

Endothelial dysfunction is a characteristic finding in both patients with type 1 diabetes and in regular smokers and is an important precursor to atherosclerosis. The urate molecule has antioxidant properties, which could influence endothelial function. The impact of acutely raising uric acid concentrations on endothelial function was studied in eight men with type 1 diabetes, eight healthy regular smokers, and eight age-matched healthy control subjects in a randomized, four-way, double-blind, placebo-controlled study. Subjects received 1,000 mg uric acid i.v. in vehicle, 1,000 mg vitamin C as a control antioxidant, vehicle alone, or 0.9% saline on separate occasions over 1 h. Forearm blood flow responses to intrabrachial acetylcholine and sodium nitroprusside were assessed using venous occlusion plethysmography. Responses to acetylcholine, but not sodium nitroprusside, were impaired in patients with diabetes (P < 0.001) and in smokers (P < 0.005) compared with control subjects. Administration of uric acid and vitamin C selectively improved acetylcholine responses in patients with type 1 diabetes (P < 0.01) and in regular smokers (P < 0.05). Uric acid administration improved endothelial function in the forearm vascular bed of patients with type 1 diabetes and smokers, suggesting that high uric acid concentrations in vivo might serve a protective role in these and other conditions associated with increased cardiovascular risk.

Microalbuminuria and early endothelial activation in essential hypertension

We hypothesized that in essential hypertensive patients (EHs), plasma levels of pro-atherogenic adhesion molecules would be increased and related with urine albumin excretion (UAE). Thus, this study was aimed at evaluating biochemical markers of endothelial activation and their relationship with UAE in a group of patients with uncomplicated EH. In basal condition soluble forms of adhesion molecules intercellular adhesion molecule (ICAM)-1 and vascular cell adhesion molecule (VCAM)-1, as well as 24-h UAE were assayed. One hundred patients with essential hypertension and no diabetes or ultrasonographic evidence of atherosclerosis were included in the study. Seventy normotensive healthy subjects served as controls. EHs were first studied overall, than were divided into two subgroups: those with UAE > or =20 mcg/min MAUs and those with UAE <20 mcg/min (non-MAUs). ICAM-1 (P<0.001) and VCAM-1 (P<0.0001) plasma concentrations were higher in EHs than in controls. Microalbuminuric EHs had greater levels of adhesion molecules than non-MAUs (ICAM-1 P=0.04; VCAM-1 P=0.02, respectively). In EHs UAE was correlated with ICAM-1 (r=0.29, P=0.003), and VCAM-1 (r=0.30, P=0.002). These associations were confirmed in multiple regression models (P=0.02 for both ICAM-1 and VCAM-1) including, along with adhesion molecules, age, body mass index and blood pressures. Our findings show that in essential hypertension there is a very early activation of endothelial adhesion molecules favouring atherosclerosis.

The vascular endothelium in hypertension

The vascular endothelium plays a fundamental role in the basal and dynamic regulation of the circulation. Thus, it has a crucial role in the pathogenesis of hypertension. A spectrum of vasoactive substances is synthesised in the endothelium; of these, nitric oxide (NO), prostacyclin (PGI2) and endothelin (ET)-1 are the most important. There is a continuous basal release of NO determining the tone of peripheral blood vessels. Systemic inhibition of NO synthesis or scavenging of NO through oxidative stress causes an increase in arterial blood pressure. Also, the renin-angiotensin-aldosterone system has a major role in hypertension as it has a direct vasoconstrictor effect and important interactions with oxygen free radicals and NO. Prostacyclin, in contrast to NO, does not contribute to the maintenance of basal vascular tone of conduit arteries, but its effect on platelets is most important. ET acts as the natural counterpart to endothelium-derived NO and has an arterial blood pressure-raising effect in man. Anti-hypertensive therapy lowers blood pressure and may influence these different mediators, thus influencing endothelial function. In summary, due to its position between the blood pressure and smooth muscle cells responsible for peripheral resistance, the endothelium is thought to be both victim and offender in arterial hypertension. The delicate balance of endothelium-derived factors is disturbed in hypertension. Specific anti-hypertensive and anti-oxidant treatment is able to restore this balance.

Tissue kallikrein gene polymorphisms induce no change in endothelium-dependent or independent vasodilation in hypertensive and normotensive subjects

BACKGROUND

Tissue kallikrein (TK) generates Lys-bradykinin, which is then converted to bradykinin and releases nitric oxide (NO) from endothelial cells via B2 receptors. TK gene inactivation in mice causes severe endothelial dysfunction, which is also a hallmark of human primary hypertension (PH). Healthy carriers of a loss-of-function Arg to His substitution at position 53 (R53H) of the TK gene exhibit paradoxical arterial eutrophic remodeling. We therefore investigated the impact of this and other TK gene single nucleotide polymorphisms (SNPs) on endothelium-dependent vasodilatation (EDV) and endothelium-independent vasodilatation (EIV) in PH patients and normotensive (NT) subjects.

METHODS

The TK gene SNPs were genotyped blind to the phenotype by sequencing. We compared EDV and EIV vasodilatation across TK genotypes in 131 uncomplicated PH patients and 51 healthy NT subjects. EDV and EIV were assessed as the forearm blood flow response to a graded infusion of acetylcholine and sodium nitroprusside, respectively. We also evaluated the impact of the SNPs on NO-mediated EDV and on reactive oxygen species (ROS)-induced NO breakdown with the nitric oxide synthase (NOS) inhibitor N(G)-monomethyl-L-arginine or vitamin C, respectively.

RESULTS

Genotypes and allele frequencies were in Hardy-Weinberg equilibrium and similar in PH and NT. EDV was lower in PH patients than in NT subjects. No TK genotype affected either EDV or EIV per se, or via interaction with gender and age. NO inhibition and scavenging of ROS showed no TK genotype effect on EDV. Similar conclusions were obtained with haplotype analysis.

CONCLUSIONS

These results do not support the contention that TK gene SNPs have a major impact in determining NO-mediated responses to acetylcholine.

Benfotiamine prevents macro- and microvascular endothelial dysfunction and oxidative stress following a meal rich in advanced glycation end products in individuals with type 2 diabetes

OBJECTIVE

Diabetes is characterized by marked postprandial endothelial dysfunction induced by hyperglycemia, hypertriglyceridemia, advanced glycation end products (AGEs), and dicarbonyls (e.g., methylglyoxal [MG]). In vitro hyperglycemia-induced MG formation and endothelial dysfunction could be blocked by benfotiamine, but in vivo effects of benfotiamine on postprandial endothelial dysfunction and MG synthesis have not been investigated in humans until now.

RESEARCH DESIGN AND METHODS

Thirteen people with type 2 diabetes were given a heat-processed test meal with a high AGE content (HAGE; 15.100 AGE kU, 580 kcal, 54 g protein, 17 g lipids, and 48 g carbohydrates) before and after a 3-day therapy with benfotiamine (1,050 mg/day). Macrovascular flow-mediated dilatation (FMD) and microvascular reactive hyperemia, along with serum markers of endothelial disfunction (E-selectin, vascular cell adhesion molecule-1, and intracellular adhesion molecule-1), oxidative stress, AGE, and MG were measured during both test meal days after an overnight fast and then at 2, 4, and 6 h postprandially.

RESULTS

The HAGE induced a maximum reactive hyperemia decrease of -60.0% after 2 h and a maximum FMD impairment of -35.1% after 4 h, without affecting endothelium-independent vasodilatation. The effects of HAGE on both FMD and reactive hyperemia were completely prevented by benfotiamine. Serum markers of endothelial dysfunction and oxidative stress, as well as AGE, increased after HAGE. These effects were significantly reduced by benfotiamine.

CONCLUSIONS

Our study confirms micro- and macrovascular endothelial dysfunction accompanied by increased oxidative stress following a real-life, heat-processed, AGE-rich meal in individuals with type 2 diabetes and suggests benfotiamine as a potential treatment.

Measuring endothelial function

Dysfunction of the endothelium and of the arterial wall is well described in patients with atherosclerosis, diabetes, and other risk factors for vascular disease. In recent years, clinical research has focused on elucidating the role of this dysfunction in influencing vascular disease progression. Alteration in the structure of arteries and disruption of the homeostatic functions of the endothelium act as a substrate for end-organ damage and the occurrence of vascular events. Dysfunction of the vascular endothelial cells is probably the earliest event promoting atherosclerotic lesion formation. Therefore, methods capable of assessing endothelial function at a preclinical stage hold potential to refine cardiovascular risk stratification and serve as a guide to monitor the effects of therapeutic interventions. A number of methodologies are currently employed to assess endothelial function, but the optimal approach is not firmly established. In this article, we critically appraise the use of different methodologies employed to study endothelial function as a surrogate marker of future cardiovascular risk.

Methodological issues in the assessment of skin microvascular endothelial function in humans

The study of microvascular function can be performed in humans using laser Doppler flowmetry of the skin. This technology lends itself to a wide range of applications for studying the endothelial function of skin blood vessels. We review the advantages and limitations of postocclusive hyperemia, local thermal hyperemia, acetylcholine iontophoresis, flowmotion and association with microdialysis as tools with which to investigate skin microvascular endothelial function in humans. Postocclusive hyperemia, thermal hyperemia and acetylcholine iontophoresis provide integrated indexes of microvascular function rather than specific endothelial markers. However, they are valuable tools and can be used as surrogate endpoints in clinical trials in which the assessment of microvascular function in humans is required.

Endothelial dysfunction: how can one intervene at the beginning of the cardiovascular continuum?

Endothelial dysfunction, characterized by impaired nitric oxide activity, constitutes an early step in the pathogenesis of atherosclerotic disease. Prospective studies have shown that impaired endothelium-dependent vasorelaxation and the vasodilatory response of coronary arteries to acetylcholine predict cardiovascular events. Microalbuminuria and estimated glomerular filtration rate, which are both deeply influenced by renal nitric oxide activity, are predictors of cardiovascular outcome and total mortality but develop at a later stage of renal impairment. Endothelial dysfunction reflects early stage renal involvement in the atherosclerotic processes. The Telmisartan versus Ramipril in renal ENdothelium DYsfunction (TRENDY) trial examined endothelial function of the renal vasculature as a therapeutic target in patients with hypertension and type 2 diabetes, but without albuminuria. The rationale was that blockade of the renin-angiotensin system (RAS) is cardio- and renoprotective at later stages of the disease, but the impact of blockade of the RAS at earlier stages of disease is unknown. The results of TRENDY indicate that the endothelial function, as assessed by basal nitric oxide activity, can be improved after RAS blockade. These data complement the results of the Diabetics Exposed to Telmisartan And enalaprIL (DETAIL) trial, which demonstrated that telmisartan and enalapril similarly decelerate the progression of overt diabetic nephropathy. The results of TRENDY are in accordance with the observed changes in peripheral circulation. Endothelium-dependent vasorelaxation could be improved with angiotensin II receptor blockers, but not with diuretics or beta-blockers, in hypertensive patients. Intervention at the beginning of the renal and cardiovascular continuum offers the opportunity to prevent the fatal development towards renal and cardiac failure.

Non-invasive methods and stimuli for evaluating the skin's microcirculation

Vessels in the skin are arranged into superficial and deep horizontal plexuses and they are involved in thermoregulation, oxygen and nutritional support. The skin has a large number of functions and broad appeal spanning basic mechanistic and clinical research. Indeed, the skin can be used as a marker of normal and impaired vascular control and, owing to its accessibility and frequent involvement, is easy to investigate non-invasively. A large number of non-invasive methods are available for investigating the skin, ranging from those that permit the visualisation of microvessels, to those that monitor blood flow or one of its derivatives (e.g., skin temperature and transcutaneous oxygen). Such methods can be combined with non-invasive, dynamic stimuli (e.g., the use of cold or warm stimuli, activation of the peripheral nervous system or local neuronal systems, and the topical application of vasoactive drugs) and this potentially enables the differentiation of underlying disorders (e.g., primary from secondary Raynaud's phenomenon) and also to quantify changes over time or following intervention. The present article outlines the non-invasive methods and dynamic tests that can be used to investigate the microcirculation of the skin.

Meeting report: ISN forefronts in nephrology on endothelial biology and renal disease: from bench to prevention

This ISN-sponsored Forefront in Nephrology meeting, which has brought together 120 scientists from 21 countries, has been concerned with various aspects of endothelial function and dysfunction and their contribution to progression of chronic kidney disease and/or its cardiovascular complications. The following themes were discussed in great depth: (1) phenotypical changes in the vascular endothelium - permeability, senescence, and apoptosis; (2) regulation of endothelial nitric oxide (NO) synthase function - caveolar and shear stress mechanisms, epigenetic regulation, S-nitrosylation, and Rho-kinase regulation; (3) oxidative stress and hypoxia-induced changes; (4) organellar dysfunction - lysosomes, mitochondria, and endoplasmic reticulum; (5) NO-independent mechanisms of vasomotion - epoxides, heme oxygenase-1 and carbon monoxide, thromboxane, tumor necrosis factor-alpha, and uric acid; (6) endothelial crosstalk with podocytes, monocytes, smooth muscle cells, and platelets; (7) candidate clinical biomarkers of endothelial dysfunction - functional testing of macro- and micro-vascular functions, surrogate markers, circulating detached endothelial cells, and endothelial precursor cells; and culminated in Round Table discussion on the diagnosis of endothelial dysfunction and its treatment options. In conclusion, this meeting has focused on several key problems of endothelial cell pathobiology relevant to chronic kidney disease.

Endothelial dysfunction: a multifaceted disorder (The Wiggers Award Lecture)

Endothelial cells synthesize and release various factors that regulate angiogenesis, inflammatory responses, hemostasis, as well as vascular tone and permeability. Endothelial dysfunction has been associated with a number of pathophysiological processes. Oxidative stress appears to be a common denominator underlying endothelial dysfunction in cardiovascular diseases. However, depending on the pathology, the vascular bed studied, the stimulant, and additional factors such as age, sex, salt intake, cholesterolemia, glycemia, and hyperhomocysteinemia, the mechanisms underlying the endothelial dysfunction can be markedly different. A reduced bioavailability of nitric oxide (NO), an alteration in the production of prostanoids, including prostacyclin, thromboxane A2, and/or isoprostanes, an impairment of endothelium-dependent hyperpolarization, as well as an increased release of endothelin-1, can individually or in association contribute to endothelial dysfunction. Therapeutic interventions do not necessarily restore a proper endothelial function and, when they do, may improve only part of these variables.

The emerging role of flavonoid-rich cocoa and chocolate in cardiovascular health and disease

Cocoa and chocolate have recently been found to be rich plant-derived sources of antioxidant flavonoids with beneficial cardiovascular properties. These favorable physiological effects include: antioxidant activity, vasodilation and blood pressure reduction, inhibition of platelet activity, and decreased inflammation. Increasing evidence from experimental and clinical studies using cocoa-derived products and chocolate suggest an important role for these high-flavanol-containing foods in heart and vascular protection.

Relation of plasma insulin levels to forearm flow-mediated dilatation in healthy volunteers

Although several observations suggest that insulin resistance/compensatory hyperinsulinemia (IR/CH) has a direct effect on endothelial function, independently of the metabolic abnormalities associated with the defect in insulin action, this relation has not been evaluated in apparently healthy individuals. To address this issue, we measured endothelial-dependent vasodilation in response to forearm ischemia (flow-mediated dilation [FMD]) in 47 nonsmoking, healthy volunteers without known risk factors for atherosclerosis. Measurements were also made of multiple anthropometric, metabolic, and hemodynamic variables related to IR/CH. Decreases in FMD were significantly correlated (analysis of variance for linear trend) with (1) male gender (p = 0.003), (2) waist circumference (p = 0.038), (3) higher fasting plasma insulin (p = 0.015) and triglyceride concentrations (p = 0.023), and (4) lower concentrations of high-density lipoprotein cholesterol (p = 0.001). Multivariate linear regression analysis indicated that only plasma insulin (beta -0.424) was independently associated (p <0.001) with changes in FMD, and individual differences in insulin concentrations, along with gender and brachial artery diameter at baseline, accounted for approximately 39% of the variability in FMD. In conclusion, IR/CH is an independent predictor of decreases in endothelial-dependent vasodilation in apparently healthy individuals, in the absence of traditional risk factors for atherosclerosis.

Circulating endothelial progenitor cells and endothelial function after chronic Tadalafil treatment in subjects with erectile dysfunction

We evaluated the effect of a chronic treatment with Tadalafil on progenitor cells (PCs) number and endothelial function in patients with erectile dysfunction (ED) with or without cardiovascular risk factors. Twenty-six subjects with ED and 23 aged matched controls were studied. All subjects underwent blood tests, International Index of Erectile Function (IIEF-5), Nocturnal Penile Tumescence Rigidity Monitoring test (NPTRM), brachial artery flow-mediated dilation (FMD) and PCs count. International index of erectile function, FMD and PC count were re-evaluated in all subjects at the end of Tadalafil and placebo treatment. With respect to controls patients had lower basal FMD (P < 0.05) and basal PCs (P < 0.05). Treatment with Tadalafil determined a significant increase in PCs (P < 0.001) and FMD (P < 0.001) with respect to basal level. Positive correlation was found between basal FMD and PCs (P < 0.05) and between basal FMD and PCs increase after Tadalafil treatment (P < 0.05). Tadalafil promotes a mobilization of PCs and improves endothelial function in ED patients.

Which endothelium-derived factors are really important in humans?

The endothelium plays a primary role in the local control of vascular function and structure, mainly by the production and release of NO, a potent vasodilator that also inhibits all the mechanisms involved in the pathogenesis of atherosclerosis, thus protecting the vessel wall against the development of atherosclerosis and thrombosis. Cardiovascular risk factors are associated with endothelial dysfunction, which involves enhanced production of oxygen free radicals that reduce NO availability and the release of contracting factors, including prostanoids and endothelin-1. In humans, endothelium-dependent relaxation can be assessed by tests that explore vascular reactivity. Besides the degree of vasodilation, which represents a crude estimate of endothelial function, the utilization of a complex experimental design, requiring the administration of specific agonists and antagonists, allows detailed exploration of the mediators and mechanisms involved in endothelium-dependent vasodilation. At present, the degree of endothelium-dependent vasodilation (evoked by receptor-operated agonists or the application of mechanical forces) is considered an independent predictor of cardiovascular events. In contrast, scant information is available concerning the clinical relevance of different mediators involved in endothelial function. Further studies are needed in the future to assess the specific impact of different endothelial responses on the clinical outcome in patients with cardiovascular risk factors and disease.

Evolving the concept of regulation of vascular tone in humans

Elucidation of mechanisms regulating microcirculatory vascular tone is a key issue in the knowledge of human pathophysiology. Anandamide is an endogenous lipidic cannabinoid (CB) characterized by potent vasodilator activity acting mainly through the activation of CB receptors, located on the vessel walls, and the vanilloid receptor 1, located on sensory peptidergic nerve endings within the external layers of vessel walls. In humans, cutaneous anandamide administration causes forearm skin vasodilation by activating vanilloid receptor 1 presumably on primary sensory nerves, while intrabrachial infusion of the same compound is devoid of effect on forearm muscle microcirculation. Taken together, these results indicate that, apart from a possible distrectual difference, the effect of anandamide is specific for the abluminal, but not for the endoluminal, part of the vessel wall. Thus, it is conceivable that, at least in the peripheral microcirculation, this compound could act as an autocrine/paracrine agent and not as a circulating hormone. In line with this possibility, it has been demonstrated that anandamide can be produced by macrophages and therefore its biological effect might increase in clinical conditions characterized by augmented activity of this cell line, including cardiogenic, hemorrhagic and endotoxic shock and even in atherosclerosis, inflammation and ischemia. Moreover, increased serum values of anandamide have been found in patients with endotoxic shock. However, decisive information concerning the role of anandamide in humans will be obtained when specific antagonists or inhibitors will be available. In that case, the anandamide system might represent a potential target for the treatment of important cardiovascular conditions, including severe shock.

Common Genetic Variation at the Endothelial Nitric Oxide Synthase Locus and Relations to Brachial Artery Vasodilator Function in the Community

Background— Sequence variants at the endothelial nitric oxide synthase ( NOS3 ) locus have been associated with endothelial function measures, but replication has been limited.

Methods and Results— In reference pedigrees, we characterized linkage disequilibrium structure at the NOS3 locus using 33 common single nucleotide polymorphisms (SNPs). Eighteen SNPs that capture underlying common variation were genotyped in unrelated Framingham Heart Study participants (49.5% women; mean age, 62 years) with measured brachial artery flow-mediated dilation (n=1446) or hyperemic flow velocity (n=1043). Within 3 defined blocks of strong linkage disequilibrium that spanned NOS3 , 11 SNPs captured >80% of common haplotypic variation. Among men, there were nominally significant associations between 8 NOS3 SNPs (minimum P =0.002) and between haplotypes (minimum P =0.002) and either flow-mediated dilation or hyperemic flow velocity. In women, we did not observe significant associations between NOS3 SNPs or haplotypes and endothelial function measures. To correct for multiple testing, we constructed 1000 bootstrapped null data sets and found that empirical probability values exceeded 0.05 for both phenotypes.

Conclusions— A parsimonious set of SNPs captures common genetic variation at the NOS3 locus. A conservative interpretation of our results is that, accounting for multiple testing, we did not observe statistically significant relations between NOS3 sequence variants and endothelial function measures in either sex. The nominal associations of select NOS3 variants with endothelial function in men (unadjusted for multiple testing) should be viewed as hypothesis-generating observations and may merit testing in other cohorts and experimental designs.

Systemic endothelial dysfunction in adults with cyanotic congenital heart disease

BACKGROUND

Secondary erythrocytosis results in increased shear stress in cyanotic congenital heart disease (CCHD), which may modify the balance between vasodilators and vasoconstrictors and affect systemic endothelial function. Because no data are available on systemic vasomotion, systemic endothelial function and nitric oxide (NO) availability were investigated in CCHD patients.

METHODS AND RESULTS

Responses to arterial endothelium-dependent (acetylcholine [Ach]) and -independent (sodium nitroprusside [SNP]) vasodilation, NO synthase blockade (NG-monomethyl-L-arginine [L-NMMA]), endothelin-1 (ET-1), and ET-1 receptor blockade by BQ-123 in 11 CCHD patients (O2 saturation <90%; mean+/-SD, 79+/-1%; mean+/-SD age, 39+/-2 years) were compared with those in 10 age-matched healthy referents by using forearm venous occlusion plethysmography. Resting forearm blood flow (FBF) was lower in CCHD patients than in referents (2.4+/-0.2 versus 3.5+/-0.4 mL.min(-1).100 mL(-1) of forearm volume [FAV], P<0.05). Although the response to SNP was similar in both groups (CCHD, 2.0+/-0.3 to 8.3+/-1.0; referents, 3.6+/-0.7 to 11.9+/-1.2 mL.min(-1).100 mL(-1) of FAV; P>0.1), the response to Ach was markedly reduced in CCHD (maximal increase in FBF, 2.8+/-0.8 versus 37.5+/-4.4 mL.min(-1).100 mL(-1) of FAV; P<0.0001). l-NMMA was less effective in CCHD (decrease in FBF, 25+/-6% versus 40+/-4%; P<0.05). ET-1 caused less vasoconstriction in the CCHD group (-25+/-9% versus -51+/-7%, P<0.05), but the response to BQ-123 was similar in both groups (32+/-9% versus 27+/-9%).

CONCLUSIONS

Systemic endothelial dysfunction is evident in CCHD patients as shown by strikingly reduced endothelial vasodilation to Ach. The response to exogenous ET-1 is reduced, possibly because of elevated endogenous ET-1 levels, but the effects of endogenous ET-1 on arterial tone are not enhanced, as indicated by the similar response to ET-1 blockade.

Endothelial function and dysfunction. Part II: Association with cardiovascular risk factors and diseases. A statement by the Working Group on Endothelins and Endothelial Factors of the European Society of Hypertension*

Dysfunction of the vascular endothelium is a hallmark of most conditions that are associated with atherosclerosis and is therefore held to be an early feature in atherogenesis. However, the mechanisms by which endothelial dysfunction occurs in smoking, dyslipidaemia, hyperhomocysteinaemia, diabetes mellitus, arterial hypertension, cerebrovascular diseases, coronary artery disease and heart failure are complex and heterogeneous. Recent data indicate that endothelial dysfunction is often associated with erectile dysfunction, which can precede and predict cardiovascular disease in men. This paper will provide a concise overview of the mechanisms causing endothelial dysfunction in the different cardiovascular risk factors and disease conditions, and of the impact of the intervention measures and treatments.