Obesity is associated with impaired endothelial function in the postprandial state

Adequate microvascular perfusion is essential for the regulation of tissue metabolism. Therefore, defects in microvascular function may play a role in obesity-associated insulin resistance. Steady-state hyperinsulinemia during a euglycemic hyperinsulinemic clamp stimulates endothelium-dependent vasodilation and capillary recruitment, which contribute to increased glucose uptake. These phenomena have been shown to be blunted in obesity. If insulin's effects on microcirculatory function indeed play a physiological role in regulating insulin-mediated glucose uptake, such effects should be demonstrable not only during steady-state hyperinsulinemia, but also after meal ingestion. We investigated whether similar responses occur after ingestion of a glucose load or a mixed meal. We examined the effects of a glucose drink, a mixed meal drink, or a control drink (water) on skin capillary density (i.e. baseline capillary density, hyperemic capillary recruitment, and density during venous congestion, using capillaroscopy) and skin endothelium-(in)dependent vasodilation (using laser-Doppler flowmetry with iontophoresis of acetylcholine and sodium nitroprusside) in 20 lean and 19 obese individuals. In lean individuals, neither the glucose nor the mixed meal drink induced a significant effect on capillary density or endothelium-(in)dependent vasodilation. Possibly this is related to the modest plasma insulin levels as compared to the insulin clamp. In obese individuals, the mixed meal drink, compared to the control drink, decreased baseline skin perfusion (P < 0.05) and acetylcholine-mediated vasodilation (P < 0.05), while no effect of the drinks on capillary density was found. Compared to lean individuals, obese individuals had impaired acetylcholine-mediated vasodilation after meal ingestion (P = 0.02). The latter findings are consistent with impaired postprandial microvascular function in obesity.     

Obesity is associated with impaired endothelial function in the postprandial state

Adequate microvascular perfusion is essential for the regulation of tissue metabolism. Therefore, defects in microvascular function may play a role in obesity-associated insulin resistance. Steady-state hyperinsulinemia during a euglycemic hyperinsulinemic clamp stimulates endothelium-dependent vasodilation and capillary recruitment, which contribute to increased glucose uptake. These phenomena have been shown to be blunted in obesity. If insulin's effects on microcirculatory function indeed play a physiological role in regulating insulin-mediated glucose uptake, such effects should be demonstrable not only during steady-state hyperinsulinemia, but also after meal ingestion. We investigated whether similar responses occur after ingestion of a glucose load or a mixed meal. We examined the effects of a glucose drink, a mixed meal drink, or a control drink (water) on skin capillary density (i.e. baseline capillary density, hyperemic capillary recruitment, and density during venous congestion, using capillaroscopy) and skin endothelium-(in)dependent vasodilation (using laser-Doppler flowmetry with iontophoresis of acetylcholine and sodium nitroprusside) in 20 lean and 19 obese individuals. In lean individuals, neither the glucose nor the mixed meal drink induced a significant effect on capillary density or endothelium-(in)dependent vasodilation. Possibly this is related to the modest plasma insulin levels as compared to the insulin clamp. In obese individuals, the mixed meal drink, compared to the control drink, decreased baseline skin perfusion (P < 0.05) and acetylcholine-mediated vasodilation (P < 0.05), while no effect of the drinks on capillary density was found. Compared to lean individuals, obese individuals had impaired acetylcholine-mediated vasodilation after meal ingestion (P = 0.02). The latter findings are consistent with impaired postprandial microvascular function in obesity.     

Combined use of endothelial function assessed by brachial ultrasound and high-sensitive C-reactive protein in predicting cardiovascular events

BACKGROUND: Endothelial function plays a key role in determining the clinical manifestations of atherosclerotic lesions. Elevated high-sensitive C-reactive protein (hsCRP) relates to long-term prognosis of cardiovascular disease. HYPOTHESIS: We test the hypothesis that combined use of endothelial function and hsCRP could increase predictive value of future cardiovascular events. METHODS AND RESULTS: 205 patients were followed up for a median period of 24 months. Endothelial function was assessed using brachial ultrasound to measure endothelium-dependent flow-mediated vasodilation (FMD). Cox regression analyses were conducted for the 205 subjects, with cardiovascular events being defined as myocardial infarction, hospitalization due to congestive heart failure, percutaneous coronary intervention, coronary artery bypass grafting, and ischemic stroke. Twenty nine (14%) developed cardiovascular events. Both FMD and hsCRP were significantly predictive of cardiovascular events (relative risk for patients with FMD<3% as compared to those with FMD>6%, 4.65, 95% confidence interval (CI): 1.30-16.66, p=0.018; relative risk for the highest as compared with the lowest tertile of hsCRP level, 3.59, 95% CI: 1.32-9.74, p=0.012, respectively). Further risk analysis was performed among four groups classified by FMD (FMD >or= 6% or<6%) and half percentile of hsCRP (hsCRP >or= 1 or<1 mg/dL). Relative risks for the FMD<6%/hsCRP >or= 1 mg/dL group compared to FMD >or= 6%/hsCRP<1 mg/dL group increased markedly to 12.598 (95% CI: 1.69 to 94.14, p=0.014) for cardiovascular events. CONCLUSIONS: Patients with suspected coronary artery disease may benefit from risk stratification based on both endothelium-dependent FMD and hsCRP, since combined these two factors contribute significantly toward the incidence of cardiovascular events.     

Methodology and clinical significance of heparin cofactor II. Probable heparin cofactor II deficiency in a patient with cerebrovascular thrombosis

HC II was functionally determined by thrombin inhibition in the presence of heparin in AT III-free plasma prepared by immunoadsorption on anti-AT III-Sepharose 4B column. HC II antigen concentration was assayed using specific antibodies to HC II. Simultaneously, AT III was measured. Plasma levels of HC II and AT III were determined in 110 patients with thrombotic tendency and two patients with obstetric complications and DIC. Highly significant correlations between activity and antigen prove the suitability of the methods. Reduced levels of HC II to about 50% with normal AT III values were repeatedly found in one patient with thrombotic tendency. The course of AT III and HC II during the process of DIC suggests that HC II may function as a thrombin inhibitor reserve when AT III becomes subnormally low.     

Impaired brachial artery endothelial function is not predicted by elevated triglycerides

OBJECTIVES

The purpose of this study was to determine if patients with modest hyperlipidemia, and no other risk factors for coronary artery disease (CAD), have impaired endothelium-dependent (ED) vasoactivity.

BACKGROUND

Hypercholesterolemia impairs ED vasodilation, but the impact of elevated triglycerides on endothelial function is not as well established.

METHODS

High-resolution ultrasound was used to determine flow-mediated dilation (FMD) in the brachial artery (BA) after a 5-min arterial occlusion (endothelium-dependent stimulus) and nitroglycerin-induced dilation (endothelium-independent stimulus). We studied 40 healthy controls (Group 1), 38 patients with elevated low-density lipoprotein (LDL) cholesterol (Group 2) and 35 patients with elevated triglycerides (Group 3). Patients were excluded if they had known CAD or other risk factors for CAD, or if they were receiving lipid-lowering or vasoactive medications.

RESULTS

Control patients (Group 1) had normal LDL cholesterol (2.6 ± 0.8 mmol/liter) and triglyceride levels (1.0 ± 0.5 mmol/liter) compared with Group 2 (5.2 ± 1.2 mmol/liter, 1.8 ± 0.6 mmol/liter) and Group 3 (3.5 ± 0.9 mmol/liter, 4.2 ± 2.5 mmol/liter) subjects (p < 0.001). Baseline BA diameters were the same across the three groups. There was no significant attenuation of flow-mediated vasodilation (FMD) in either of the hyperlipidemic groups (Group 1: 10.9 ± 5.0% vs. Group 2: 8.6 ± 6.1% vs. Group 3: 9.4 ± 3.9%; p = 0.14). However, nitroglycerin-induced vasodilation was mildly reduced (Group 1: 21.0 ± 5.0% vs. 16.9 ± 7.6% vs. 17.3 ± 7.7%; p = 0.01). By multivariate analysis, after controlling for baseline diameters, only the ratio of LDL/high-density lipoprotein predicted a minor impairment in FMD.

CONCLUSIONS

In patients free from other cardiac risk factors, modest elevations of triglycerides or LDL cholesterol do not significantly attenuate BA endothelial-dependent vasodilation. Synergism with other cardiac risk factors may be required to significantly impair endothelial function in these patients.     

Sickle cell disorders and chronic intravascular haemolysis are associated with low plasma heparin cofactor II

Thrombotic events are known to be increased in patients with sickle cell syndromes and a variety of abnormalities of coagulation or endothelial function have been described, although the relevance of these findings either to the pathogenesis of vaso-occlusive phenomena or the risk of thrombosis are unclear. Heparin cofactor II (HCII) and antithrombin III are circulating inhibitors of thrombin and low plasma levels have been associated with an increased risk of thrombosis in otherwise healthy individuals. We describe for the first time abnormally low plasma levels of HCII in patients with sickle cell syndromes. 45 adult patients with sickle cell syndromes (31 SS, 10 SC, 4 SβThal) were compared with 61 age matched control patients for HCII in plasma. There was a highly significant reduction in HCII in SS patients irrespective of crisis or transfusion state 0.68 ± 0.15 U/ml (mean ± SD) compared with controls 1.00 ± 0.19 U/ml ( P < 0.001). HCII antigen was also significantly reduced (0.53 ± 0.19 U/ml) compared with controls (1.02 ± 0.23 U/ml, P < 0.0001). By contrast there was no reduction in antithrombin III in this group. HCII (0.63 ± 0.13 U/ml, P < 0.001) and HCII antigen (0.54 ± 0.08 U/ml, P < 0.001) are also significantly reduced in SC patients HCII levels increased towards control values during sickle cell crises, in patients taking the contraceptive pill, or with regular blood transfusion; however, plasma HCII concentrations were not increased acutely by exchange transfusion. HCII was also decreased in thalassaemia intermedia and pyruvate kinase deficiency, suggesting that intravascular haemolysis may be the cause of reduced HCII levels.     

Placental dermatan sulfate: isolation, anticoagulant activity, and association with heparin cofactor II

Pregnancy is associated with hemostatic challenges that may lead to thrombosis. Heparin cofactor II (HCII) is a glycosaminoglycan-dependent thrombin inhibitor present in both maternal and fetal plasma. HCII activity increases during pregnancy, and HCII levels are significantly decreased in women with severe pre-eclampsia. Dermatan sulfate (DS) specifically activates HCII and is abundant in the placenta, but the locations of DS and HCII in the placenta have not been determined. We present evidence that DS is the major anticoagulant glycosaminoglycan in the human placenta at term. DS isolated from human placenta contains disaccharides implicated in activation of HCII and has anticoagulant activity similar to that of mucosal DS. Immunohistochemical studies revealed that DS is associated with fetal blood vessels and stromal regions of placental villi but is notably absent from the syncytiotrophoblast cells in contact with the maternal circulation. HCII colocalizes with DS in the walls of fetal blood vessels and is also present in syncytiotrophoblast cells. Our data suggest that DS is in a position to activate HCII in the fetal blood vessels or in the stroma of placental villi after injury to the syncytiotrophoblast layer and thereby inhibit fibrin generation in the placenta.     

Impaired endothelial function in patients with rapidly stabilized unstable angina: assessment by noninvasive brachial artery ultrasonography.

BACKGROUND: Endothelial dysfunction may contribute to symptoms of instability in patients with acute coronary syndromes. High-resolution external ultrasound assessment of the brachial artery responses allows noninvasive determination of endothelial function. HYPOTHESIS: This study was conducted to assess endothelial function in patients with unstable angina using a noninvasive technique. METHODS: We studied 189 patients who were subdivided into three groups. Group 1: 60 apparently healthy subjects with no cardiovascular risk factors or symptoms of coronary artery disease; Group 2: 105 subjects with cardiovascular risk factors--arterial hypertension, hypercholesterolemia, cigarette smoking, diabetes, and obesity, but no evidence of coronary artery disease; and Group 3: 24 patients with unstable angina (chest pain at rest within the 24 h preceding study entry). All patients underwent pre- and postischemic brachial artery test evaluation with measurements of internal arterial diameters and blood flow. RESULTS: Results are expressed as percentage change from basal values. Subjects in Groups 1 and 2 showed a diameter increase of 19.1 and 11.9%, respectively, whereas patients in Group 3 showed a diameter change of 1.2% (p < 0.002 and < 0.0001, respectively). Calculated blood flow did not differ significantly in Groups 1 or 2 (74.4 and 56.4%), but was notably lower in Group 3 (18.4%, p < 0.005 vs. Groups 1 and 2). In nine patients of Group 3, the brachial studies were repeated 4 weeks after symptom stabilization and showed values comparable with those in Group 2. CONCLUSIONS: Patients with unstable angina showed endothelial dysfunction compared with control individuals. It is of interest that in patients whose symptoms were stabilized by medical therapy, endothelial function was restored 4 weeks after hospital discharge.     

Reproducibility of brachial ultrasonography and flow-mediated dilatation (FMD) for assessing endothelial function

Abstract Background : High-resolution brachial artery ultrasonography is used to study vasodilator response induced by physiologic reactive hyperaemia. We examined the reproducibility of measuring flow-mediated dilatation (FMD) on two occasions.
Aims : To determine the degree of variability of this technique in our vascular laboratory for the design of clinical research studies.
Methods : Nineteen subjects were studied on two separate occasions using an Acuson 128 ultrasound device and a 7.0 MHz linear array transducer. Reactive hyperaemia was induced in the brachial artery by inflation and release of a blood pressure cuff. Nitrate-induced dilatation was assessed in 11 of the 19 subjects. Measurements were made by two observers blinded to subject details.
Results : The 11 subjects given sublingual GTN during the first ultrasound study had a mean nitrate-induced dilatation of 20.7% (sd 9.6). The mean vessel diameter of 3.78 mm (sd 0.7) at rest and 3.89 mm (sd 0.7) during reactive hyperaemia yielded a mean FMD of only 3.0% (sd 2.7). The mean difference in FMD within-observers was 0.13% (sd 2.07), between-observers 0.06% (sd 2.17) and between-studies was 0.57% (sd 6.83).
Conclusions : The reproducibility of FMD measured by brachial artery ultrasound was poor and likely to render the measurements inaccurate for clinical research in our hands. Between-study variation contributed the largest proportion of total study variability. We suggest that investigators using this technique conduct their own careful reproducibility studies in order to avoid the misinterpretation of 'negative' studies.     

Brachial endothelial function is impaired in patients with systemic lupus erythematosus

OBJECTIVE: To verify if endothelial function is impaired in pre-menopausal women with systemic lupus erythematosus (SLE) and whether endothelial dysfunction is related to disease duration, cumulative prednisone dose, antimalarial use, anticardiolipin antibody (aCL), hypertension, Raynaud's phenomenon, disease activity score, and vasculitis. METHODS: Using high-resolution ultrasound, we measured the diameter of brachial artery at rest, during reactive hyperemia, and after glyceryl trinitrate (GTN). We compared 69 pre-menopausal female patients with SLE (mean age 29 +/- 8 years) with 35 age and sex-matched controls (mean age 29 +/- 6 years), The mean disease duration was 72 months. RESULTS: There was no significant difference in baseline brachial artery diameter. The flow-mediated dilation (endothelial dependent dilation) was significantly impaired in SLE patients when compared to controls (5.0 +/- 5.0% vs 12.0 +/- 6.0%, p < 0.001), even in the subgroup of patients without coronary artery disease risk factor (4.5 +/- 4.0% vs 12.0 +/- 6.0%, p < 0.001). The GTN induced dilation (endothelial independent dilation) was significantly lower in the aCL positive SLE patients when compared to the controls (11.9 +/- 4.0% vs 16.3 +/- 6.0%, p < 0.05). The endothelium-dependent dilation was not related to disease duration, cumulative prednisone dose, antimalarial use, anticardiolipin antibody, hypertension history, Raynaud's phenomenon, SLE disease activity score or vasculitis. CONCLUSION: This is the first study using brachial artery ultrasound imaging to evaluate endothelium function in SLE. Patients with SLE presented lower flow mediated dilation (endothelium dependent dilation) than sex and age-matched controls, even in patients without traditional cardiovascular risk factors and this may represent an early atherosclerotic process.     

Decreased vascular contractility induced by hemin is associated with a reduced rho-kinase activity

Objectives

In this study, the role of rho-kinase activity in the modulation of vascular contractility induced by hemin, a heme oxygenase inducer, was investigated.

Methods

Aortic rings from Wistar rats were incubated in physiological saline solution (PSS) containing hemin at 10-4 M for six hours then contracted with phenylephrine, and a dose-response curve was established. The effect of Y-27632, a rho-kinase inhibitor, on the relaxation of the pre-contracted aortic rings was then studied.

Results

Incubation of the aortic rings in hemin induced an increased expression of heme oxygenase 1 (HO-1). A reduction in the contractile force of aortic rings incubated in hemin was observed in response to phenylephrine. Y-27632 at a concentration of 10-6 M induced a 36% relaxation of the control aortic rings but only a 20% relaxation in aortic rings treated with hemin.

Conclusion

These data suggest that the decreased vascular contractility induced by hemin could, in part, result from an inhibition of rho-kinase activity.     

Endothelial dysfunction in patients with rheumatoid arthritis is associated with a reduced number and impaired function of endothelial progenitor cells

BACKGROUND: Rheumatoid arthritis (RA) is associated with increased morbidity and mortality attributable to accelerated atherosclerosis and cardiovascular events. OBJECTIVE: To determine the role played by endothelial progenitor cells (EPC) in the defence system against arteriosclerosis. METHODS: The number and function of EPC in 13 young patients with RA with low disease activity (DAS28 3.5 (0.3)) and 13 healthy control subjects was studied. Endothelial function was investigated by agonist-induced, endothelium dependent vasodilatation measured by the forearm blood flow technique. Migratory activity and adhesion of EPC to tumour necrosis factor alpha (TNFalpha) activated mature endothelial cells and components of the extracellular matrix were tested in vitro. Putative precursor populations (CD34(+), CD34(+)/CD133(+), and CD34(+)/KDR(+) haematopoietic stem cells) were measured by flow cytometric analysis. RESULTS: Acetylcholine-induced, endothelium dependent vasodilatation was reduced by about 50% in patients with RA, indicating endothelial dysfunction, whereas endothelium-independent vasodilatation in response to glyceryl trinitrate was at control level. Significantly reduced numbers of EPC were found in the patients compared with controls. Migratory activity of EPC was decreased in patients with RA. Adhesion to mature endothelial cells after activation with TNFalpha was enhanced only in controls. The adhesion to matrix proteins and the number of putative precursor cell lineages was comparable in both groups. CONCLUSION: Endothelial dysfunction in patients with RA with low grade inflammation is associated with a reduced number and partial dysfunction of EPC. Further studies are needed to explore whether interventions that potentially ameliorate the number and function of EPC also improve endothelial function in these patients.