Protective effect of high density lipoprotein on endothelium-dependent vasodilatation

Relationship between concentration difference of different density lipoproteins and shear stress in atherosclerosis

Previous research has observed concentration polarization in LDL and HDL in the arterial system. However, there is no report that links this concentration polarization to the development of vascular atherosclerosis (AS). Therefore, the purpose of this study is to establish the relationship between concentration difference of LDL and HDL and shear stress using a carotid bifurcation vascular model. PTFE was employed to create the carotid bifurcation model. Endothelial cells were coated on the inner wall of the graft. In a recirculation system, HDL and LDL concentration were measured under two different ICA flow velocities at 5 different locations within our model. We report the following: (1) LDL and HDL concentration difference was observed in both high flow and low flow environments; (2) the degree of LDL and HDL concentration polarization varied depending of high flow and low flow environment; (3) absolute values of concentration difference between LDL and HDL at the inner wall surface decreased with the increase in shear stress when shear stress was more than 1.5 Pa. This variation trend would be more pronounced if shear stress were less than 0.5 Pa. Our study suggests that under the action of shear stress, concentration differences of LDL or HDL create a disturbance in the balance of atherogenic factors and anti-As factors, resulting in the occurrence of AS.

Endothelial dysfunction but not increased carotid intima-media thickness in young European women with endometriosis

BACKGROUND

Atherosclerosis is a chronic and degenerative disease developing typically in the elderly; nonetheless, a condition of accelerated atherosclerosis can be observed precociously in the presence of some diseases. Endometriosis, a chronic benign gynecological disorder, shows some characteristics, such as oxidative stress, systemic inflammation and a pro-atherogenic lipid profile, which could increase the risk of developing accelerated atherosclerosis. The aim of our study was to evaluate markers of subclinical atherosclerosis in young European women with endometriosis.

METHODS

This cross-sectional study included 37 women with endometriosis and 31 control subjects. The presence of subclinical atherosclerosis was investigated by ultrasound evaluation of common carotid intima-media thickness (ccIMT) and flow-mediated dilation (FMD); in addition, serum levels of lipids, inflammatory and coagulation parameters, as well as markers of endothelial inflammation and activation, were determined.

RESULTS

Women with endometriosis showed significantly lower values of FMD compared with controls [mean difference: -4.62, 95% confidence interval (CI): -6.52, -2.73; P < 0.001], whereas no significant differences in ccIMT values were found between the two groups. As regards markers of endothelial inflammation and activation, women with endometriosis had significantly higher values of inter-cellular adhesion molecule 1 (P < 0.001), vascular cell adhesion molecule 1 (P < 0.001), E-selectin (P < 0.001), von Willebrand factor (P = 0.004) and ristocetin cofactor (P = 0.001) compared with controls.

CONCLUSIONS

Our study suggests that women with endometriosis have more subclinical atherosclerosis, resulting in a higher risk of developing cardiovascular disorders. Moreover, our findings demonstrate that endothelial dysfunction can occur in the absence of structural atherosclerotic changes; its evaluation might be helpful in young women with endometriosis.

The endothelial dysfunction in patients with type 2 diabetes mellitus is associated with IL-6 gene promoter polymorphism in Chinese population

The purpose of this study is to examine the effects of IL-6 gene promoter -174G/C and -572G/C polymorphism on endothelial function of Chinese T2DM and normal glucose regulation (NGR) subjects. 512 newly diagnosed T2DM patients and 483 NGR subjects were recruited and Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) was performed for the IL-6 gene promoter -174G/C and -572G/C polymorphism. Flow-mediated dilation (FMD) was measured as a non-invasive indicator for endothelial function. The results show that the C allele and CC genotype at -174 of IL-6 gene promoter region was extremely rare in both T2DM and NGR groups; genotypes' and alleles' frequency at -572 of IL-6 gene promoter region is of no difference between T2DM and NGR groups; within T2DM group, higher plasma IL-6 concentration and lower FMD was found in patients with -572 GC (2.36 ± 0.69, 4.23 ± 3.82%) or GG (2.32 ± 0.74, 4.24 ± 3.67%) genotype, compared with patients with CC (2.15 ± 0.62, 5.28 ± 3.94%) genotype. The conclusion of the study is that in comparison with patients of CC genotype, the T2DM patients of -572 GC or GG genotype may have more aggravated endothelial dysfunction (ED) and be at higher risk for coronary artery disease (CAD).

Vascular endothelial function assessed by a noninvasive ultrasound method and serum asymmetric dimethylarginine concentrations in mild-to-moderate plaque-type psoriatic patients

OBJECTIVES

Our aim was to evaluate vascular endothelial function assessed by serum asymmetric dimethylarginine (ADMA) concentrations and noninvasive ultrasonographic parameters such as flow-mediated dilatation (FMD) and nitroglycerin-induced dilatation (NID) in mild-to-moderate plaque-type psoriatic patients, as rated by the Psoriasis Area and Severity Index.

DESIGN AND METHODS

Plaque-type psoriatic patients (n = 29) diagnosed with clinical and/or histopathological findings and control subjects (n = 25) without skin and systemic metabolic diseases were included in the study.

RESULTS

There was no statistically significant difference between patients and control subjects in respect to FMD (p = 0.441), NID (p = 0.557), or serum ADMA concentrations (p = 0.225). Also, among the acute-phase reactants, serum C-reactive protein and plasma fibrinogen levels were moderately higher in patients when compared to control subjects (p = 0.008 and p = 0.011, respectively).

CONCLUSIONS

Mild-to-moderate plaque-type psoriatic patients with low-to-medium grade systemic inflammation did not have evidence of vascular endothelial function.

Endothelial function in individuals with coronary artery disease with and without type 2 diabetes mellitus

The goal of this study was to determine if individuals with coronary artery disease (CAD) and type 2 diabetes mellitus (T2DM) had greater endothelial dysfunction (ED) than individuals with only CAD. Flow-mediated dilation (FMD), calculated as percentage increase in brachial artery diameter in response to postischemic blood flow, was measured after an overnight fast in 2 cohorts. The first cohort included 76 participants in the Northern Manhattan Study with CAD; 25 also had T2DM. The second cohort was composed of 27 individuals with both T2DM and CAD who were participants in a study of postprandial lipemia. Combined, we analyzed 103 patients with CAD: 52 with T2DM (T2DM+) and 51 without T2DM (T2DM-). The 52 CAD T2DM+ subjects had a mean FMD of 3.9% +/- 3.2%, whereas the 51 CAD T2DM- subjects had a greater mean FMD of 5.5% +/- 4.0% (P < .03). An investigation of various confounders known to affect FMD identified age and body mass index as the only significant covariates in a multiple regression model. Adjusting for age and body mass index, we found that FMD remained lower in T2DM+ subjects compared with T2DM- subjects (difference, -1.99%; P < .03). In patients with CAD, the concomitant presence of T2DM is independently associated with greater ED, as measured by FMD. This finding may be relevant to the greater early and late morbidity and mortality observed in patients with both CAD and T2DM.

ATP-binding cassette transporter G1 and high-density lipoprotein promote endothelial NO synthesis through a decrease in the interaction of caveolin-1 and endothelial NO synthase

OBJECTIVE

To investigate whether cholesterol efflux to high-density lipoprotein (HDL) via ATP-binding cassette transporter G1 (ABCG1) modulates the interaction of caveolin (Cav) 1 and endothelial NO synthase (eNOS).

METHODS AND RESULTS

ABCG1 promotes cholesterol and 7-oxysterol efflux from endothelial cells (ECs) to HDL. It was previously reported that ABCG1 protects against dietary cholesterol-induced endothelial dysfunction by promoting the efflux of 7-oxysterols to HDL. Increased cholesterol loading in ECs is known to cause an inhibitory interaction between Cav-1 and eNOS and impaired NO release. In human aortic ECs, free cholesterol loading promoted the interaction of Cav-1 with eNOS, reducing eNOS activity. These effects of cholesterol loading were reversed by HDL in an ABCG1-dependent manner. HDL also reversed the inhibition of eNOS by cholesterol loading in murine lung ECs, but this effect of HDL was abolished in Cav-1-deficient murine lung ECs. Increased interaction of Cav-1 with eNOS was also detected in aortic homogenates of high-cholesterol diet-fed Abcg1(-/-) mice, paralleling a decrease in eNOS activity and impaired endothelial function.

CONCLUSIONS

The promotion of cholesterol efflux via ABCG1 results in a reduced inhibitory interaction of eNOS with Cav-1.

Correlation study of pulmonary embolism and high-density lipoprotein cholesterol

BACKGROUND

It is currently thought that pulmonary embolism and deep vein thrombosis are different manifestations of the same pathological process of venous thromboembolism. Venous thromboembolism has a negative correlation with high-density lipoprotein cholesterol.

HYPOTHESIS

Pulmonary embolism has a negative correlation with the level of high-density lipoprotein cholesterol.

METHODS

A total of 90 patients with pulmonary embolism, diagnosed and treated at a single center, were retrospectively analyzed for the present study. Among them were 57 cases of pulmonary arterial trunk embolism in group A and 33 cases of pulmonary arterial non-trunk embolism in group B.

RESULTS

The results showed that the level of high-density lipoprotein cholesterol decreased markedly in patients with pulmonary arterial trunk embolism as compared to those with pulmonary arterial non-trunk embolism. A stepwise logistic regression analysis was performed upon the relationship between pulmonary arterial trunk embolism and multiple factors. The results showed that a pulmonary arterial trunk embolism had a negative correlation with the level of high-density lipoprotein cholesterol and a positive correlation with triglyceride and high sensitivity C-reactive protein.

CONCLUSIONS

Pulmonary arterial trunk embolism is negatively correlated with the level of high-density lipoprotein cholesterol.

Anti-atherogenic effects of high-density lipoprotein on nitric oxide synthesis in the endothelium

1. The endothelium is critical in the control of vascular haemodynamics and haemostasis. Endothelial dysfunction, typically characterized by decreased nitric oxide bioavailability and response to endothelium-dependent agonists, is well accepted as a defining characteristic of early atherosclerosis. 2. Numerous epidemiological studies have reported that increased levels of circulating HDL are vasculoprotective and reduce the incidence of adverse cardiovascular events. Traditionally, these effects have been attributed to the ability of HDL to remove cholesterol from cells via reverse cholesterol transport. However, there is increasing evidence that the beneficial effects on the endothelium by HDL encompass its anti-inflammatory, antithrombotic and anti-oxidative properties, which include the release of nitric oxide (NO). 3. This review highlights recent findings on the importance of HDL in reducing atherosclerotic risk. We focus on the beneficial effects of HDL-induced NO release and how this relates to endothelial dysfunction and on the effect of HDL on vascular repair via endothelial progenitor cells.

HDL-associated dehydroepiandrosterone fatty acyl esters: enhancement of vasodilatory effect of HDL

OBJECTIVE

Dehydroepiandrosterone (DHEA) and high-density lipoprotein (HDL) are both vascular relaxants. In the circulation, HDL transports DHEA fatty acyl esters (DHEA-FAEs), which are naturally occurring lipophilic derivatives of DHEA. We studied in isolated rat mesenteric arteries whether HDL-associated DHEA-FAE improves the vasodilatory effect of HDL.

METHODS AND RESULTS

To prepare DHEA-FAE-enriched HDL, we incubated DHEA with human plasma. After incubation, HDL was isolated, purified, and added in cumulative doses (0.1-125 microg/ml) to noradrenaline-precontracted rat arterial rings. DHEA-FAE-enriched HDL caused a dose-dependent relaxation (maximal 43+/-4%), which was significantly stronger than the effect of HDL from the control incubation without addition of DHEA (25+/-2%, p<0.001). When plasma incubation of DHEA was carried out in the presence of lecithin:cholesterol acyltransferase (LCAT) inhibitor, the relaxation response to HDL (25+/-3%) did not differ from the control HDL (p=0.98). Pretreatment of the arterial rings with nitric oxide synthase (NOS) antagonist impaired the relaxation response to DHEA-FAE-enriched HDL (43+/-4% vs. 30+/-3%, p=0.008). Similar experiments were performed with 17beta-estradiol (E(2)). Compared to control HDL, E(2)-FAE-enriched HDL induced slightly but non-significantly stronger relaxation.

CONCLUSIONS

DHEA-FAE-enriched HDL was a stronger vasodilator than native HDL, and vascular relaxation was in part mediated by NOS, suggesting that DHEA-FAE may improve HDL's antiatherogenic function.

Concentration polarization of high-density lipoprotein and its relation with shear stress in an in vitro model

The purpose of this study was to determine the concentration polarization of high-density lipoprotein (HDL) at the surface of the carotid artery under conditions of steady flow and to establish its relationship with shear stress using an in vitro vascular simulation model of carotid bifurcation. Shear stress, HDL concentration at the surface, and the ratio of HDL concentration at the surface to concentration in bulk flow were measured at different locations within the model under high-speed (1.451 m/s) and low-speed (0.559 m/s) flow. HDL showed concentration polarization at the surface of the carotid artery model, particularly in the internal carotid artery sinus. With decreasing flow velocity, the shear stress at the surface also decreased, and HDL concentration polarization increased. The concentration polarization of HDL was negatively and strongly correlated with shear stress at both low- (r = −0.872, P < .001) and high-speed flow (r = −0.592, P = .0018).

Noninvasive assessment of subclinical atherosclerosis in children and adolescents: recommendations for standard assessment for clinical research: a scientific statement from the American Heart Association

Deterioration in endothelial function and arterial stiffness are early events in the development of cardiovascular diseases. In adults, noninvasive measures of atherosclerosis have become established as valid and reliable tools for refining cardiovascular risk to target individuals who need early intervention. With limited pediatric data, the use of these techniques in children and adolescents largely has been reserved for research purposes. Therefore, this scientific statement was written to (1) review the current literature on the noninvasive assessment of atherosclerosis in children and adolescents, (2) make recommendations for the standardization of these tools for research, and (3) stimulate further research with a goal of developing valid and reliable techniques with normative data for noninvasive clinical evaluation of atherosclerosis in pediatric patients. Precise and reliable noninvasive tests for atherosclerosis in youth will improve our ability to estimate future risk for heart attack and stroke. Currently, large longitudinal studies of cardiovascular risk factors in youth, such as the Bogalusa and Muscatine studies, lack sufficient adult subjects experiencing hard outcomes, such as heart attack and stroke, to produce meaningful risk scores like those developed from Framingham data.

Novel therapies for increasing serum levels of HDL

The protectiveness of elevated HDL-C against CHD and its long-term sequelae is a subject of intense investigation throughout the world. HDL has the capacity to modulate a large number of atherogenic mechanisms, such as inflammation, oxidation, thrombosis, and cell proliferation. Among lipoproteins, HDL is also unique, in that it promotes the mobilization and clearance of excess lipid via the series of reactions collectively termed "reverse cholesterol transport." Numerous therapeutic agents are being developed in an attempt to modulate serum levels of HDL-C as well as its functionality. This article discusses the development of newer treatments targeted at raising HDL-C and HDL particle numbers to reduce residual risk in patients at risk for CHD.

Smoking cessation early in pregnancy and birth weight, length, head circumference, and endothelial nitric oxide synthase activity in umbilical and chorionic vessels: an observational study of healthy singleton pregnancies

BACKGROUND

Reduced production of the vasodilator nitric oxide (NO) in fetal vessels in pregnant smokers may lower the blood flow to the fetus and result in lower birth weight, length, and head circumference. The present study measured endothelial NO synthase (eNOS) activity in fetal umbilical and chorionic vessels from nonsmokers, smokers, and ex-smokers and related the findings to the fetal outcome.

METHODS AND RESULTS

Of 266 healthy, singleton pregnancies, 182 women were nonsmokers, 43 were smokers, and 41 stopped smoking early in pregnancy. eNOS activity and concentration were quantified in endothelial cells of the fetal vessels. Cotinine, lipid profiles, estradiol, l-arginine, and dimethylarginines that may affect NO production were determined in maternal and fetal blood. Serum cotinine verified self-reported smoking. Newborns of smokers had a lower weight (P< or =0.001) and a smaller head circumference (P< or =0.041) and were shorter (P< or =0.001) than newborns of nonsmokers and ex-smokers. eNOS activity in umbilical veins of smokers was 36% lower (P<0.001), eNOS concentration was 47% lower (P<0.001), and the fetal plasma level of high-density lipoprotein was 18% lower (P<0.001) than those of nonsmokers, whereas the same levels were found in umbilical veins from ex-smokers and nonsmokers. The same patterns in eNOS activity and concentration were found in umbilical arteries and chorionic vessels. Fetal plasma levels of estradiol, l-arginine, dimethylarginines, total cholesterol, and triglycerides were similar for nonsmokers, smokers, and ex-smokers.

CONCLUSIONS

The findings suggest that maternal smoking reduces eNOS activity in the fetal vascular bed, contributing to retarded fetal growth caused by the reduction of vasodilatory capacity, and suggest that smoking cessation early in pregnancy prevents these effects in newborns.

ABCG1 and HDL protect against endothelial dysfunction in mice fed a high-cholesterol diet

Plasma HDL levels are inversely related to the incidence of atherosclerotic disease. Some of the atheroprotective effects of HDL are likely mediated via preservation of EC function. Whether the beneficial effects of HDL on ECs depend on its involvement in cholesterol efflux via the ATP-binding cassette transporters ABCA1 and ABCG1, which promote efflux of cholesterol and oxysterols from macrophages, has not been investigated. To address this, we assessed endothelial function in Abca1(-/-), Abcg1(-/-), and Abca1(-/-)Abcg1(-/-) mice fed either a high-cholesterol diet (HCD) or a Western diet (WTD). Non-atherosclerotic arteries from WTD-fed Abcg1(-/-) and Abca1(-/-)Abcg1(-/-) mice exhibited a marked decrease in endothelium-dependent vasorelaxation, while Abca1(-/-) mice had a milder defect. In addition, eNOS activity was reduced in aortic homogenates generated from Abcg1(-/-) mice fed either a HCD or a WTD, and this correlated with decreased levels of the active dimeric form of eNOS. More detailed analysis indicated that ABCG1 was expressed primarily in ECs, and that these cells accumulated the oxysterol 7-ketocholesterol (7-KC) when Abcg1(-/-) mice were fed a WTD. Consistent with these data, ABCG1 had a major role in promoting efflux of cholesterol and 7-KC in cultured human aortic ECs (HAECs). Furthermore, HDL treatment of HAECs prevented 7-KC-induced ROS production and active eNOS dimer disruption in an ABCG1-dependent manner. Our data suggest that ABCG1 and HDL maintain EC function in HCD-fed mice by promoting efflux of cholesterol and 7-oxysterols and preserving active eNOS dimer levels.

New and emerging risk factors for CVD

Morphological and immunocytochemical studies have elucidated the complex processes involved in atherogenesis. The notion of plaque instability has emerged from this work and underscored the importance of inflammation in determining clinical complications associated with atherosclerosis, such as acute coronary syndrome. Cells of the immune system have been detected within atherosclerotic lesions and auto-antibodies directed against modified LDL and heat-shock proteins have been identified in the blood of individuals with atherosclerosis. The use of risk 'engines', e.g. the Framingham coronary risk score, has facilitated the identification of individuals at high risk, but the constituent classical risk factors used in these algorithms do not adequately differentiate individuals at moderate risk. As age is a major component of the equations used in these algorithms they are not particularly useful in young adults, and their applicability to non-Caucasian populations has been questioned. Biomarkers of early disease and plaque instability have therefore both been sought. Although some of these markers have been shown individually to be associated with a significant hazard ratio, no substantial improvement in discrimination has been demonstrated when they are incorporated into a risk 'engine'. The latter has generally been assessed by receiver operator characteristic curve analysis, although this approach has been criticised. Other modalities, including imaging and functional assessments of vascular function, are now being developed for clinical use.

Beyond high-density lipoprotein cholesterol levels evaluating high-density lipoprotein function as influenced by novel therapeutic approaches

A number of therapeutic strategies targeting high-density lipoprotein (HDL) cholesterol and reverse cholesterol transport are being developed to halt the progression of atherosclerosis or even induce regression. However, circulating HDL cholesterol levels alone represent an inadequate measure of therapeutic efficacy. Evaluation of the potential effects of HDL-targeted interventions on atherosclerosis requires reliable assays of HDL function and surrogate markers of efficacy. Promotion of macrophage cholesterol efflux and reverse cholesterol transport is thought to be one of the most important mechanisms by which HDL protects against atherosclerosis, and methods to assess this pathway in vivo are being developed. Indexes of monocyte chemotaxis, endothelial inflammation, oxidation, nitric oxide production, and thrombosis reveal other dimensions of HDL functionality. Robust, reproducible assays that can be performed widely are needed to move this field forward and permit effective assessment of the therapeutic potential of HDL-targeted therapies.

Low high-density lipoprotein cholesterol: an important consideration in coronary heart disease risk assessment

PURPOSE OF REVIEW

One aim is to summarize evidence from observational studies and clinical trials evaluating the inverse relationship between high-density lipoprotein and coronary heart disease. Other aims are to explore the mechanisms underlying the reported cardioprotective effects of high-density lipoprotein and to evaluate therapeutic modalities to increase high-density lipoprotein levels and functionality.

RECENT FINDINGS

In addition to reverse cholesterol transport, recent data suggest that high-density lipoprotein possesses antioxidant, anti-inflammatory and fibrinolytic properties and the inverse relationship between high-density lipoprotein cholesterol and coronary heart disease is most evident with associated elevations in low-density lipoprotein cholesterol and triglyceride. Recent data suggest, however, that even after low-density lipoprotein cholesterol is sufficiently reduced, residual coronary heart disease risk persists with low high-density lipoprotein cholesterol. The excess death rate reported with the high-density lipoprotein cholesterol raising drug torcetrapib appears to have been the result of an off-target effect of the drug, rather than an effect attributable to cholesteryl ester transfer protein inhibition.

SUMMARY

Low high-density lipoprotein cholesterol remains an important consideration in coronary heart disease risk assessment, however several issues remain unresolved. They include the extent to which low high-density lipoprotein cholesterol in the absence of other risk factors augments risk, the relationship between high-density lipoprotein functionality and levels of high-density lipoprotein cholesterol and whether and to what extent improving these parameters independently offsets coronary heart disease risk.

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.

Detailed exploration of the endothelium: parameterization of flow-mediated dilation through principal component analysis

Endothelial dysfunction is associated with cardiovascular diseases and their risk factors (CVRF), and flow-mediated dilation (FMD) is increasingly used to explore it. In this test, artery diameter changes after post-ischaemic hyperaemia are classically quantified using maximum peak vasodilation (FMDc). To obtain more detailed descriptors of FMD we applied principal component analysis (PCA) to diameter-time curves (absolute), vasodilation-time curves (relative) and blood-velocity-time curves. Furthermore, combined PCA of vessel size and blood-velocity curves allowed exploring links between flow and dilation. Vessel diameter data for PCA (post-ischaemic: 140 s) were acquired from brachial ultrasound image sequences of 173 healthy male subjects using a computerized technique previously reported by our team based on image registration (Frangi et al 2003 IEEE Trans. Med. Imaging 22 1458). PCA provides a set of axes (called eigenmodes) that captures the underlying variation present in a database of waveforms so that the first few eigenmodes retain most of the variation. These eigenmodes can be used to synthesize each waveform analysed by means of only a few parameters, as well as potentially any signal of the same type derived from tests of new patients. The eigenmodes obtained seemed related to visual features of the waveform of the FMD process. Subsequently, we used eigenmodes to parameterize our data. Most of the main parameters (13 out of 15) correlated with FMDc. Furthermore, not all parameters correlated with the same CVRF tested, that is, serum lipids (i.e., high LDL-c associated with slow vessel return to a baseline, while low HDL-c associated with a lower vasodilation in response to similar velocity stimulus), thus suggesting that this parameterization allows a more detailed and factored description of the process than FMDc.

Endothelial and antithrombotic actions of HDL

It is well recognized that high-density lipoprotein (HDL)-cholesterol is antiatherogenic and serves a role in mediating cholesterol efflux from cells. However, HDL has multiple additional endothelial and antithrombotic actions that may also afford cardiovascular protection. HDL promotes the production of the atheroprotective signaling molecule nitric oxide (NO) by upregulating endothelial NO synthase (eNOS) expression, by maintaining the lipid environment in caveolae where eNOS is colocalized with partner signaling molecules, and by stimulating eNOS as a result of kinase cascade activation by the high-affinity HDL receptor scavenger receptor class B type I (SR-BI). HDL also protects endothelial cells from apoptosis and promotes their growth and their migration via SR-BI-initiated signaling. As importantly, there is evidence of a variety of mechanisms by which HDL is antithrombotic and thereby protective against arterial and venous thrombosis, including through the activation of prostacyclin synthesis. The antithrombotic properties may also be related to the abilities of HDL to attenuate the expression of tissue factor and selectins, to downregulate thrombin generation via the protein C pathway, and to directly and indirectly blunt platelet activation. Thus, in addition to its cholesterol-transporting properties, HDL favorably regulates endothelial cell phenotype and reduces the risk of thrombosis. With further investigation and resulting greater depth of understanding, these mechanisms may be harnessed to provide new prophylactic and therapeutic strategies to combat atherosclerosis and thrombotic disorders.

Basal production of nitric oxide (NO) and non-NO vasodilators in the forearm microcirculation in Type 2 diabetes: associations with blood pressure and HDL cholesterol

We examined basal forearm microcirculatory blood flow (FBF) using venous occlusive strain-gauge plethysmography in 47 middle-aged men and women [55+/-1 years] with Type 2 diabetes and 15 age-matched healthy individuals [52+/-3 years], all receiving aspirin. Blood flow was also measured following infusion of N(G)-monomethyl-L-arginine into the brachial artery to inhibit basal NO release (FBF+L-NMMA). Acetylcholine (ACh) and sodium nitroprusside (SNP) were administered to assess endothelium-dependent and endothelium-independent functions. Compared with controls, diabetic subjects had significantly lower vasodilatory responses to ACh and SNP (p<0.05 for each). Basal FBF and FBF+L-NMMA were increased in diabetic subjects compared with controls (2.4+/-0.2 ml/100ml/min versus 1.7+/-0.2 ml/100ml/min, p=0.02 and 1.9+/-0.1 ml/100ml/min versus 1.2+0.1 ml/100ml/min, p=0.01, respectively) whereas the change in FBF following L-NMMA was greater in the controls (-27% versus -19%, p=0.05). Amongst the diabetic subjects, pulse pressure and HDL cholesterol were independent predictors of FBF (b=0.04+/-0.01, adjusted r2=0.21 and p=0.001, and b=3.3+/-1.2, adjusted r2=0.12 and p=0.007, respectively) and FBF+L-NMMA (b=0.03+/-0.01, adjusted r2=0.20, p=0.002 and b=2.1+/-0.9, adjusted r2=0.09 and p=0.02, respectively). Diastolic blood pressure predicted the change in FBF with L-NMMA (b=-1.02+/-0.32, adjusted r2=0.20 and p=0.003). Our findings suggest that well controlled T2DM patients have impaired agonist-mediated vasodilatation of the forearm resistance arteries that is associated with impaired basal release of nitric oxide but an increase in the release of non-NO vasodilators. The latter may be a compensatory response to increased arterial stiffness and may be facilitated by an effect of HDL.

High frequency of endothelial vasomotor dysfunction after acute coronary syndromes in non-culprit and angiographically normal coronary arteries: a reversible phenomenon

This study aimed to assess endothelium-dependent vasomotor function in non-culprit coronary vessels in patients with recent acute coronary syndrome (ACS). Endothelial dysfunction can also concern peripheral vessels during ACS, but the frequency of this phenomenon at coronary circulation level is unknown. Endothelial function was assessed by infusion of graded doses of acetylcholine (ACh) in a non-culprit coronary artery of normal appearance in 43 patients having recently suffered from non-ST ACS, and reassessed 6 months later. Endothelium-dependent vasoreactivity was impaired at baseline in 81% (35/43) of the patients, and only 19% (8/43) of patients showed a normal response to ACh. Among the 35 subjects with initial dysfunction, 77% showed a significant improvement 6 months later. All patients without initial endothelial dysfunction remained normal. C-reactive protein (CRP) level was elevated at month 0, and had declined at follow-up, tending towards normal levels. At that time, apolipoprotein A-I (apoA-I) levels were correlated with vasomotor improvement in univariate (p < 0.02) and multivariate analysis (p < 0.04). In conclusion, endothelium dysfunction is very frequently observed after recent ACS in non-culprit and angiographically normal coronary arteries, and an improvement occurs within 6 months in most cases. After resolution of the initial inflammation, apoA-I seems to play an important role in endothelial function.

High-density lipoprotein as a therapeutic target: clinical evidence and treatment strategies

The clinical importance of low serum levels of high-density lipoprotein (HDL) cholesterol is often under-recognized and underappreciated as a risk factor for premature atherosclerosis as well as for cardiovascular morbidity and mortality. Low serum levels of HDL are frequently encountered, especially in patients who are obese or have the metabolic syndrome. In prospective epidemiologic studies, every 1-mg/dL increase in HDL is associated with a 2% to 3% decrease in coronary artery disease risk, independent of low-density lipoprotein (LDL) cholesterol and triglyceride (TG) levels. The primary mechanism for this protective effect is believed to be reverse cholesterol transport, but several other anti-inflammatory, antithrombotic, and antiproliferative functions for HDL have also been identified. In recognition of these antiatherogenic effects, recent guidelines have increased the threshold for defining low levels of HDL for both men and women. The first step in achieving these revised targets is therapeutic lifestyle changes. When these measures are inadequate, pharmacotherapy specific to the patient's lipid profile should be instituted. Niacin therapy, currently the most effective means for raising HDL levels, should be initiated in patients with isolated low HDL (HDL <40 mg/dL, LDL and non-HDL at or below National Cholesterol Education Program (NCEP) targets based on global cardiovascular risk evaluation). Patients who have both low HDL and elevated LDL should receive a statin or statin-niacin combination therapy, and patients with concomitant low HDL and elevated TGs should receive a fibrate initially, with a statin, niacin, or ezetimibe added thereafter as needed to help attain NCEP lipoprotein targets.

The role of total and high-molecular-weight complex of adiponectin in vascular function in offspring whose parents both had type 2 diabetes

AIMS/HYPOTHESIS

Adiponectin is an adipokine with insulin-sensitising and anti-atherogenic properties. We studied the role played by total adiponectin and by the bioactive high-molecular-weight (HMW) oligomeric complexes of adiponectin in vascular function in offspring whose parents both had type 2 diabetes, a population at high risk of diabetes and atherosclerosis.

METHODS

Total and %HMW adiponectin, the cytokines C-reactive protein, interleukin-6 and plasminogen activator inhibitor-1 (PAI-1), as well as lipid profiles were assayed in 19 offspring, each with two type 2 diabetic parents. Subjects underwent OGTTs and IVGTTs. Endothelium-dependent vasodilation (EDV) was assessed by brachial artery ultrasonography.

RESULTS

There was a significant relationship between %HMW and total adiponectin levels (r=0.72, p=0.001). Despite an expected strong positive correlation between HDL-cholesterol and adiponectin levels (r=0.52, p=0.04), as well as HDL-cholesterol and EDV (r=0.56, p<0.02), there was no significant relationship between either total adiponectin or % HMW adiponectin and EDV. Adiponectin was inversely associated with PAI-1 (r=0.50, p=0.05), but did not correlate with the inflammatory markers C-reactive protein or interleukin-6.

CONCLUSIONS/INTERPRETATION

In offspring of diabetic parents, a population at high risk of diabetes and atherosclerotic disease, there is no relationship between total or %HMW adiponectin and endothelium-dependent vasodilation. However, low adiponectin was associated with impaired fibrinolysis as manifested by increased levels of plasminogen activator inhibitor-1.

Mechanisms, Significance and Treatment of Vascular Dysfunction in Type 2 Diabetes Mellitus

Endothelial dysfunction and increased arterial stiffness occur early in the pathogenesis of diabetic vasculopathy. They are both powerful independent predictors of cardiovascular risk. Advances in non-invasive methodologies have led to widespread clinical investigation of these abnormalities in diabetes mellitus, generating a wealth of new knowledge concerning the mechanisms of vascular dysfunction, risk factor associations and potential treatment targets. Endothelial dysfunction primarily reflects decreased availability of nitric oxide (NO), a critical endothelium-derived vasoactive factor with vasodilatory and anti-atherosclerotic properties. Techniques for assessing endothelial dysfunction include ultrasonographic measurement of flow-mediated vasodilatation of the brachial artery and plethysmography measurement of forearm blood flow responses to vasoactive agents. Arterial stiffness may be assessed using pulse wave analysis to generate measures of pulse wave velocity, arterial compliance and wave reflection. The pathogenesis of endothelial dysfunction in type 2 diabetes is multifactorial, with principal contributors being oxidative stress, dyslipidaemia and hyperglycaemia. Elevated blood glucose levels drive production of reactive oxidant species (ROS) via multiple pathways, resulting in uncoupling of mitochondrial oxidative phosphorylation and endothelial NO synthase (eNOS) activity, reducing NO availability and generating further ROS. Hyperglycaemia also contributes to accelerated arterial stiffening by increasing formation of advanced glycation end-products (AGEs), which alter vessel wall structure and function. Diabetic dyslipidaemia is characterised by accumulation of triglyceride-rich lipoproteins, small dense low-density lipoprotein (LDL) particles, reduced high-density lipoprotein (HDL)-cholesterol and increased postprandial free fatty acid flux. These lipid abnormalities contribute to increasing oxidative stress and may directly inhibit eNOS activity. Although lipid-regulating agents such as HMG-CoA reductase inhibitors (statins), fibric acid derivatives (fibrates) and fish oils are used to treat diabetic dyslipidaemia, their impact on vascular function is less clear. Studies in type 2 diabetes have yielded inconsistent results, but this may reflect sampling variation and the potential over-riding influence of oxidative stress, dysglycaemia and insulin resistance on endothelial dysfunction. Results of positive intervention trials suggest that improvement in vascular function is mediated by both lipid and non-lipid mechanisms, including anti-inflammatory, anti-oxidative and direct effects on the arterial wall. Other treatments, such as renin-angiotensin-aldosterone system antagonists, insulin sensitisers and lifestyle-based interventions, have shown beneficial effects on vascular function in type 2 diabetes. Novel approaches, targeting eNOS and AGEs, are under development, as are new lipid-regulating therapies that more effectively lower LDL-cholesterol and raise HDL-cholesterol. Combination therapy may potentially increase therapeutic efficacy and permit use of lower doses, thereby reducing the risk of adverse drug effects and interactions. Concomitant treatments that specifically target oxidative stress may also improve endothelial dysfunction in diabetes. Vascular function studies can be used to explore the therapeutic potential and mechanisms of action of new and established interventions, and provide useful surrogate measures for cardiovascular endpoints in clinical trials.

Assessment of flow-mediated vasodilatation (FMD) of the brachial artery: effects of technical aspects of the FMD measurement on the FMD response

AIMS

The ability to assess endothelial function non-invasively with B-mode ultrasound has lead to its widespread application in a variety of studies. However, the absolute values obtained using this approach vary considerably across studies. We studied whether technical aspects of the methodology can explain the wide variety in absolute values across studies.

METHODS AND RESULTS

A literature search was performed to identify published reports on flow-mediated vasodilatation (FMD) of the brachial artery published between 1992 and 2001. Information on type of equipment (wall track/B-mode), location of the measurement (antecubital fossa/upper arm), occlusion site (lower/upper arm), occlusion duration (min), and occlusion pressure was extracted. Patient characteristics were also extracted. For the healthy populations, mean FMD varied from 0.20 to 19.2%; for the coronary heart disease (CHD) patients FMD varied from -1.3 to 14%; for subjects with diabetes mellitus FMD varied from 0.75 to 12%. Compared with occlusion at the upper arm, lower arm occlusion was related to decreased FMD (mean difference in FMD -2.47%; 95% CI 0.55-4.39). An occlusion duration of > or =4.5 min was related to an increased FMD compared with an occlusion time of < or =4 min (mean difference 1.30%; 95% CI 0.35-2.46). These findings were adjusted for other technical aspects of the methodology and for differences in risk factors between populations.

CONCLUSION

Mean FMD differs widely between studies. There is a great overlap between populations (healthy, CHD, diabetics). Our findings suggest that the technical aspects of the measurements, the location, and the duration of the occlusion may explain some of these differences, whereas type of equipment, location of the measurement, and occlusion pressure do not.

Comparative effects of lipid-lowering therapies

The pharmacologic regulation of lipid metabolism in patients with dyslipidemia is unequivocally associated with significant reductions in risk for cardiovascular morbidity and mortality. A number of therapeutic drug classes have been developed in an effort to ever more precisely and intensively modulate lipid metabolism. Statins, fibrates, ezetimibe, and niacin exert their effects via different mechanisms and afford physicians the opportunity to beneficially impact multiple pathways in patients. When used alone or in combination, these drugs decrease risk for the development and progression of atherosclerotic disease. There are strong clinical trial data to support of the use of lipid-lowering therapies in the settings of both primary and secondary prevention. This article (1) discusses the mechanisms of action of antilipidemic medications, (2) reviews dosing regimens and the pharmacokinetic differences among drugs of the same class, (3) assesses risk for drug interactions, and (4) reviews the clinical trial evidence used to support the use of particular antilipidemic medications in specific physiologic settings. The incidence of dyslipidemia is rising worldwide. This trend portends an ever-growing need for the aggressive and judicious use of different antilipidemic medication(s) in patients at risk for all forms of atherosclerotic vascular disease.

HDL action on the vascular wall: is the answer NO?

Circulating levels of HDL cholesterol are inversely related to the risk of atherosclerosis, and therapeutic increases in HDL reduce the incidence of cardiovascular events. A new study shows that HDL-associated lysophospholipids stimulate the production of the potent antiatherogenic signaling molecule NO by the vascular endothelium.

Low high-density lipoprotein cholesterol: physiological background, clinical importance and drug treatment

Low high-density lipoprotein (HDL) cholesterol is an important risk factor for coronary heart disease (CHD). In vitro, HDL exerts several potentially anti-atherogenic activities. HDLs mediate the reverse cholesterol transport (RCT) from peripheral cells to the liver, inhibit oxidation of low-density lipoprotein (LDL), adhesion of monocytes to the endothelium, apoptosis of vascular endothelial and smooth muscle cells and platelet activation, and stimulate the endothelial secretion of vasoactive substances as well as smooth muscle cell proliferation. Hence, raising HDL-cholesterol levels has become an interesting target for anti-atherosclerotic drug therapy. Levels of HDL cholesterol and the composition of HDL subclasses in plasma are regulated by apolipoproteins, lipolytic enzymes, lipid transfer proteins, receptors and cellular transporters. The interplay of these factors leads to RCT and determines the composition and, thereby, the anti-atherogenic properties of HDL. Several inborn errors of metabolism, as well as genetic animal models, are characterised by both elevated HDL cholesterol and increased rather than decreased cardiovascular risk. These findings suggest that the mechanism of HDL modification rather than simply increasing HDL cholesterol determine the efficacy of anti-atherosclerotic drug therapy. In several controlled and prospective intervention studies, patients with low HDL cholesterol and additional risk factors benefited from treatment with fibric acid derivatives (fibrates) or HMG-CoA reductase inhibitors (statins). However, only in some trials was prevention of coronary events in patients with low HDL cholesterol and hypertriglyceridaemia related to an increase in HDL cholesterol. We discuss the clinical and metabolic effects of fibrates, statins, nicotinic acid and sex steroids, and present novel therapeutic strategies that show promise in modifying HDL metabolism. In conclusion, HDL-cholesterol levels increase only moderately after treatment with currently available drugs and do not necessarily correlate with the functionality of HDL. Therefore, the anti-atherosclerotic therapy of high-risk cardiovascular patients should currently be focused on the correction of other risk factors present besides low HDL cholesterol. However, modification of HDL metabolism and improvement of RCT remain an attractive target for the development of new regimens of anti-atherogenic drug therapy.

Effect of endogenous estrogen on endothelial function in women with coronary heart disease and its mechanism

BACKGROUND

Estrogen promotes and modulates vascular endothelial function, which may be protective against development of atherosclerosis. Asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthase, has been reported to be associated with the impairment of vascular endothelial function. Recent studies suggested estrogen replacement therapy lowers plasma concentrations of ADMA in healthy postmenopausal women. However, the relation between endogenous estrogen and ADMA and their effect on endothelial function in patients with coronary heart disease (CHD) remains unclear.

METHODS

Flow-mediated dilatation (FMD) and nitroglycerin-induced dilatation (NID) of the brachial arteries were detected by using high-resolution ultrasound in 33 women with CHD and 17 healthy controls. Plasma estradiol, ADMA, and lipid concentrations were also measured in all subjects.

RESULTS

In comparison with control group, FMD and NID were significantly decreased in the CHD group (1.73 +/- 1.26% vs. 5.37 +/- 3.20%, p < 0.001 and 12.38 +/- 6.70% vs. 20.79 +/- 7.57%, p < 0.01, respectively). Plasma estradiol concentrations in the CHD group were lower than in controls (27.80 +/- 12.28 vs. 43.83 +/- 14.30 pg/ml, p < 0.01), whereas ADMA concentrations in the CHD group were higher than in controls (3.39 +/- 1.07 vs. 1.31 +/- 0.69 micromol/l, p < 0.001). Pearson correlation analysis determined that plasma estradiol concentrations were associated with FMD, NID, age, systolic pressure, diastolic pressure and ADMA (r = 0.610, p < 0.01; r = 0.392, p < 0.01; r = -0.589, p < 0.01; r= -0.364, p < 0.01; r = -0.350, p < 0.05; r = -0.553, p < 0.01; respectively). Multiple linear stepwise regression analysis revealed that plasma estradiol concentrations was independently positively correlated with FMD (p < 0.005) and negatively correlated with ADMA (p < 0.05).

CONCLUSIONS

Both FMD and NID are impaired in women with CHD. The decrease of endogenous estrogen concentrations and the increase of ADMA concentrations may involve the endothelial dysfunction in women with CHD.

Insulin impairs endothelium-dependent vasodilation independent of insulin sensitivity or lipid profile

Insulin resistance is a risk factor for atherosclerosis and is associated with hyperinsulinemia, abnormal lipid profile, and hypertension. Whether hyperinsulinemia affects vascular function independent of insulin resistance or other metabolic risk factors is unknown. This investigation aimed to assess the effects of hyperinsulinemia on endothelial function in subjects with a spectrum of insulin sensitivity and lipid profile. Endothelium-dependent (flow-mediated dilation, FMD) and -independent (nitroglycerin) responses of the brachial artery were studied by high-resolution ultrasound before and during hyperinsulinemia (euglycemic clamp) in 25 normoglycemic, normotensive subjects. Participants were divided into an insulin-sensitive and an insulin-resistant subgroup based on their sensitivity index values, with a cutoff of 8, and into a normal-cholesterol and a high-cholesterol subgroup based on their total cholesterol levels, with a cutoff of 5.2 mmol/l (200 mg/dl). In the whole population, FMD was lower during hyperinsulinemia compared with baseline (2.3 +/- 0.6% vs. 6 +/- 0.6%; P < 0.001). Resting FMD was lower in the insulin-resistant subgroup compared with the insulin-sensitive subgroup (4.2 +/- 0.9% vs. 7.4 +/- 0.8%; P = 0.014) and in the high-cholesterol subjects compared with the normal-cholesterol subjects (4.4 +/- 0.7% vs. 8 +/- 0.7%; P = 0.002). Hyperinsulinemia decreased FMD in both the insulin-sensitive (from 7.4 +/- 0.8% to 3.6 +/- 0.4%; P < 0.001) and insulin-resistant (from 4.2% to 1.22%; P = 0.012) subgroups and in both the normal-cholesterol (from 8 +/- 0.7% to 3.9 +/- 0.4%; P < 0.001) and high-cholesterol (from 4.4 +/- 0.7% to 1.1 +/- 0.8%; P = 0.01) participants. Acute hyperinsulinemia impairs conduit vessel endothelial function independent of insulin sensitivity and lipid profile. Insulin may trigger endothelial dysfunction and promote atherosclerosis.

Endothelial nitric oxide synthase gene polymorphism, homocysteine, cholesterol and vascular endothelial function

Nitric oxide-dependent vasodilation is impaired early in the pathogenesis of vascular disease. Both the 4ab polymorphism of endothelial nitric oxide synthase (eNOS) and elevated plasma homocysteine are putatively associated with coronary artery disease (CAD). Few studies have investigated the influence of either on endothelial function in normal subjects. We aimed to examine any effect of three eNOS gene polymorphisms and plasma levels of homocysteine, folate and lipids on vascular endothelial function in normal healthy subjects. Community subjects (n=60) were selected for their eNOS genotype. Largely NOz.-dependent, flow-mediated dilation (FMD) of the brachial artery and the response to glyceryl trinitrate (GTN) were measured. Neither FMD nor response to GTN in 4a allele carriers was significantly different from that of 4b homozygotes, (7.1+/-0.5 S.E.M. vs. 7.1+/-0.6%) and (18.9+/-1.2 vs. 18.9+/-0.9%), respectively. Responses were also independent of the other polymorphisms. FMD was significantly correlated with HDL-cholesterol (P=0.02). After accounting for serum folate, there was a significant inverse correlation between FMD and plasma homocysteine (P=0.03). In these normal community subjects, plasma homocysteine and HDL-cholesterol were predictors of FMD despite subjects being recruited without regard to these variables and despite normal plasma levels.

Aggressive lipid lowering does not improve endothelial function in type 2 diabetes: the Diabetes Atorvastatin Lipid Intervention (DALI) Study: a randomized, double-blind, placebo-controlled trial

OBJECTIVE

Endothelial dysfunction is considered an important early marker of atherosclerosis and cardiovascular risk and is currently used as a surrogate end point for cardiovascular risk in clinical trials. Type 2 diabetic patients show a characteristic dyslipidemia. Aggressive lipid lowering might be an effective method to improve endothelial function in these patients.

RESEARCH DESIGN AND METHODS

A randomized, double-blind, placebo-controlled trial was completed to study the effect of 30 weeks' administration of atorvastatin 10 mg and 80 mg on endothelial function, as assessed by B-mode ultrasound of the brachial artery, in 133 patients with type 2 diabetes without a history of cardiovascular disease.

RESULTS

Patients with diabetes and diabetic dyslipidemia had considerable endothelium-dependent and endothelium-independent dysfunction; mean flow-mediated vasodilation (SD) was 3.16% (3.56), and mean response on sublingual nitroglycerin was 6.58% (6.04). Despite substantial lowering of all atherogenic lipid parameters, no improvement of endothelium-dependent vasodilatation was found (P > 0.8).

CONCLUSIONS

We observed considerable baseline endothelium-dependent and endothelium-independent dysfunction in patients with diabetes and diabetic dyslipidemia without a history of cardiovascular disease. Aggressive lipid lowering by administration of atorvastatin, resulting in substantial improvement of the lipid profile, did not reverse endothelial dysfunction.

HDL and arteriosclerosis: beyond reverse cholesterol transport

The inverse correlation between serum levels of high density lipoprotein (HDL) cholesterol and the risk of coronary heart disease, the protection of susceptible animals from atherosclerosis by transgenic manipulation of HDL metabolism, and several potentially anti-atherogenic in vitro-properties have made HDL metabolism an interesting target for pharmacological intervention in atheroslcerosis. We have previously reviewed the concept of reverse cholesterol transport, which describes both the metabolism and the classic anti-atherogenic function of HDL (Arterioscler. Thromb. Vasc. Biol. 20 2001 13). We here summarize the current understanding of additional biological, potentially anti-atherogenic properties of HDL. HDL inhibits the chemotaxis of monocytes, the adhesion of leukocytes to the endothelium, endothelial dysfunction and apoptosis, LDL oxidation, complement activation, platelet activation and factor X activation but also stimulates the proliferation of endothelial cells and smooth muscle cells, the synthesis of prostacyclin and natriuretic peptide C in endothelial cells, and the activation of proteins C and S. These anti-inflammatory, anti-oxidative, anti-aggregatory, anti-coagulant, and pro-fibrinolytic activities are exerted by different components of HDL, namley apolipoproteins, enzymes, and even specific phospholipids. This complexity further emphasizes that changes in the functionality of HDL rather than changes of plasma HDL-cholesterol levels determine the anti-atherogenicity of therapeutic alterations of HDL metabolism.

Cardiovascular risk factors as determinants of endothelium-dependent and endothelium-independent vascular reactivity in the general population

OBJECTIVES

We examined to what extent the variation in risk factors for coronary heart disease (CHD) and the Framingham risk score (FRS) explain the variation in vascular reactivity in adults aged 30 to 53 years.

BACKGROUND

The role of risk factors in determining vascular reactivity in the general population has not been quantified.

METHODS

Risk factors for CHD were measured, and the FRS was calculated in 69 healthy volunteers. Lipoprotein particle size was measured using proton-nuclear magnetic resonance spectroscopy. Forearm plethysmography was used to assess blood flow responses to acetylcholine (ACh), bradykinin (BK), glyceryl trinitrate (GTN), noradrenaline and N(G)-monomethyl-L-arginine (L-NMMA).

RESULTS

Lower ACh and BK responses were associated with a higher body mass index (BMI), a higher total cholesterol to high-density lipoprotein (HDL) cholesterol ratio, lower HDL cholesterol and a cigarette smoking habit (all p < 0.05). Higher low-density lipoprotein (LDL) cholesterol was also associated with a lower BK response (p = 0.001). A decreased GTN response was associated with a higher BMI and total cholesterol to HDL cholesterol ratio (both p < 0.05). A decreased L-NMMA response was associated with a smoking habit (p < 0.001). Lipoprotein particle sizes did not independently predict any vascular response. A high FRS was associated with a reduced response to ACh (p = 0.07), BK (p = 0.003) and L-NMMA (p = 0.003), and the relationship was stronger in women than in men. Altogether, risk factors explained 13%, 9%, 8% and 15% of the response to ACh, BK, GTN and L-NMMA, respectively.

CONCLUSIONS

Lipids, BMI and smoking are important determinants of vascular reactivity. The FRS is predictive of agonist-stimulated, endothelium-dependent vasodilation and basal NO release. However, much of the variation in the vascular responses to these drugs, at this age, remains unexplained.