Obesity in adolescent men increases the risk of venous thromboembolism in adult life

BACKGROUND

As the population of obese and severely obese young adults grows, it is becoming increasingly important to recognize the long-term risks associated with adolescent obesity.

OBJECTIVES

This study aimed to determine the association between body mass index (BMI) in young men at enlistment for military service and later risk of venous thromboembolism (VTE).

METHODS

Nationwide register-based prospective cohort study of men enlisting 1969 to 2005, followed through the Swedish National Patient and Cause of Death registries. We identified 1 639 838 men (mean age, 18.3 years) free of prior venous thromboembolism, of whom 29 342 were obese (BMI 30 to <35 kg m^-2 ) and 7236 severely obese (BMI ≥ 35 kg m^-2 ). The participants were followed until a first registered diagnosis of VTE.

RESULTS

During a median follow-up of 28 years (interquartile interval, 20 to 36 years), 11 395 cases of deep vein thrombosis and 7270 cases of pulmonary embolism were recorded. Compared with men with a BMI of 18.5 to <20 kg m^-2 , men with higher BMI in young adulthood showed an incrementally increasing risk of VTE that was moderately but significantly increased already at normal BMI levels. Adolescent obese men with a BMI of 30 to 35 kg m^-2 had an adjusted hazard ratio of 2.93 (95% confidence interval, 2.65 to 3.24) for VTE. Severely obese men with a BMI of ≥35 kg m^-2 had a hazard ratio of 4.95 (95% confidence interval, 4.16 to 5.90).

CONCLUSIONS

Men who were obese or severely obese in young adulthood had a marked increase in risk of VTE.

Valproic acid selectively increases vascular endothelial tissue-type plasminogen activator production and reduces thrombus formation in the mouse

Essentials Stimulating endogenous fibrinolysis could be a novel antithrombotic strategy. The effect of valproic acid on endothelial tissue plasminogen activator in mice was investigated. Valproic acid increased tissue plasminogen activator expression in vascular endothelium. Valproic acid reduced fibrin deposition and thrombus formation after vascular injury.

SUMMARY

Background The endogenous fibrinolytic system has rarely been considered as a target to prevent thrombotic disease. Tissue-type plasminogen activator (t-PA) production is potently increased by histone deacetylase (HDAC) inhibitors in endothelial cells in vitro, but whether this translates into increased vascular t-PA production and an enhanced fibrinolytic capacity in vivo is unknown. Objectives To determine whether the HDAC inhibitor valproic acid (VPA) stimulates production of t-PA in the vasculature of mice, and whether VPA pretreatment affects fibrin deposition and clot formation after mechanical vessel injury. Methods Mice were injected with VPA twice daily for up to 5 days. t-PA mRNA, and antigen expression in the mouse aorta and the circulating levels of t-PA were determined. Fibrin and thrombus dynamics after mechanical vessel injury were monitored with intravital confocal microscopy. Potential effects of VPA on platelets and coagulation were investigated. Results and Conclusions We found that VPA treatment increased vascular t-PA production in vivo and, importantly, that VPA administration was associated with reduced fibrin accumulation and smaller thrombi in response to vascular injury, but still was not associated with an increased risk of bleeding. Furthermore, we observed that higher concentrations of VPA were required to stimulate t-PA production in the brain than in the vasculature. Thus, this study shows that VPA can be dosed to selectively manipulate the fibrinolytic system in the vascular compartment and reduce thrombus formation in vivo.

Effect of shear stress, statins and TNF-α on hemostatic genes in human endothelial cells

Atherosclerotic plaque formation and progression are dependent on local shear stress patterns and inflammatory cytokines. Statins effectively reduce the progression of atherosclerosis and the incidence of cardiovascular events. However, the benefit of statins cannot be explained by cholesterol reduction alone. This study, investigated the non-lipid lowering effects of simvastatin and rosuvastatin on endothelial anti- and prothrombotic genes under different biomechanical and inflammatory stress conditions. Endothelial cells responded in a similar way to simvastatin and rosuvastatin. However, they were more sensitive to simvastatin. The statins had anti-inflammatory properties counteracting the TNF-α effect on the hemostatic genes studied. There was no observed synergistic effect between shear stress and simvastatin. Simvastatin had a counteracting effect on t-PA and PAI-1 compared to TNF-α and shear stress. Simvastatin blocked the TNF-α suppressive effect on thrombomodulin and eNOS, irrespective of shear stress. The strong inductive effect of TNF-α on VCAM-1 was counteracted by simvastatin and shear stress in an additive dose-response dependent way.

Consistency of blood pressure and impact on cardiovascular structure over 20 years in young men

OBJECTIVE

To identify, in a prospective study, how blood pressure levels at the age of twenty predict hypertension and cardiovascular remodelling 20 years later.

METHODS

Twenty-year-old men with blood pressure (BP) elevation [systolic blood pressure (SBP) 140-160 and/or diastolic blood pressure (DBP) 85-95 mmHg; blood pressure elevation (BPE) group] or normal BP [SBP 110-130 and DBP 60-80 mmHg; normal controls (NC) group] entered the study in 1987. In 2007, follow-up was conducted including ambulatory BP, echocardiography, anthropometric and intima media thickness (IMT) measurements.

RESULTS

Assessed with 24-h ambulatory BP, the prevalence of hypertension was 35/47 (74.5%) and 1/17 (5.9%) in the BPE and NC group at follow-up respectively. Twenty-four hour mean arterial pressure (MAP) increased from 86.6 (0.8) to 97.2 (1.2) (P < 0.0001), and from 83.1 (1.5) to 88.1 (1.2) mmHg (P < 0.01) from baseline to follow-up in the BPE and NC group respectively. At follow-up, left ventricular mass index (LVMI) was 122 (4) and 106 (4) g m(-1) in the BPE and NC group (unpaired t-test; P < 0.01) respectively, whilst IMT was 0.61 (0.01) and 0.57 (0.01) mm in the BPE and NC group (P < 0.05) respectively. In a logistic regression model, prevalence of hypertension was best explained by office MAP and 24-h DBP at baseline (R(2) 0.333; P < 0.05). A combined model of office MAP, body mass index and insulin levels at baseline explained 56% of LVMI at follow-up.

CONCLUSIONS

BP elevation in young age predicts hypertension and adverse cardiovascular remodelling at the age of 40 years. Baseline office MAP is the best predictor of hypertension, 24-h MAP and LVMI.

Methodological Studies of Multiple Reference Genes as Endogenous Controls in Vascular Gene Expression Studies

Detection and quantification of differentially expressed genes requires valid and reliable references to control for error variability introduced by preparatory procedures or efficiency of reverse transcription and polymerase chain reaction (PCR) amplification conditions. So-called housekeeping genes are frequently used as endogenous standards, based on the assumption that they are constitutively expressed and independent of experimental conditions. However, if the influence of experimental stimuli is to be analyzed, it cannot a priori be assumed that their expression is unaffected by stimulation. In the present study, the authors studied the expression of different housekeeping genes in the vascular endothelium of intact conduit vessels perfused in a unique biomechanical perfusion model. Ten control gene candidates were investigated by microarray expression analysis. Further, five of these genes were systematically analyzed by real-time reverse transcriptase (RT)-PCR gene quantification and their suitability as reference genes were evaluated. On the basis of these findings, the authors suggest criteria for evaluation of endogenous control genes in vascular perfusion studies.

Influence of TNF-alpha and biomechanical stress on endothelial anti- and prothrombotic genes

Biomechanical stress modulates vascular tone, vascular remodelling and the spatial localisation of atherosclerotic plaques. Inflammatory cytokines, such as TNF-alpha, regulate expression of genes that impair the function of endothelial cells. This study investigates the combinatory effect of different biomechanical stresses and TNF-alpha on the expression of endothelial anti- and prothrombotic genes. Human umbilical vein endothelial cells were exposed to TNF-alpha and different levels of static/pulsatile tensile stress or shear stress. The response in endothelial cells to TNF-alpha was not modulated by tensile stress. However, shear stress was a more potent stimulus. Shear stress counteracted the cytokine-induced expression of VCAM-1, and the cytokine-suppressed expression of thrombomodulin and eNOS. Shear stress and TNF-alpha additively induced PAI-1, whereas shear stress blocked the cytokine effect on t-PA and u-PA. A flow profile characterized by high laminar shear stress seems to render the endothelial cell more resistant to inflammatory stress.

Impaired myocardial t-PA release in patients with coronary artery disease

AIMS

Myocardial ischemia remains a significant perioperative complication in coronary artery disease (CAD) patients. We hypothesized that noxious stimuli during major surgery are associated with an acute release of tissue-type plasminogen activator (t-PA) into the coronary circulation, and that this response is reduced by CAD.

METHODS AND RESULTS

Two patient groups, with (n=14) and without (n=8) CAD, were studied during the initial phase of heart surgery. After retrograde great cardiac vein catheterizations during closed-chest conditions, coronary arterial-venous concentration gradients of t-PA and plasminogen activator inhibitor type-1 (PAI-1) were measured together with coronary blood flow measurements, allowing derivation of coronary net release rates. Pre-surgery atrial pacing, performed to evaluate the influence of increases in heart rate (+ 40 beats/min) and coronary blood flow (+ 80 ml/min), did not significantly alter coronary net release of t-PA or PAI-1 in either patient group. Sternotomy induced a prominent increase in coronary net release of both total and active t-PA in the non-CAD group. This response was considerably reduced in the CAD group.

CONCLUSIONS

This study provides the first analysis of coronary t-PA release during major surgery and demonstrates a deficient local endothelial t-PA release in patients with CAD. This suggests a reduced local fibrinolytic capacity in CAD patients, which may explain the increased risk for coronary thrombosis in this patient group.

TNF-alpha mediated suppression of tissue type plasminogen activator expression in vascular endothelial cells is NF-kappaB- and p38 MAPK-dependent

BACKGROUND

Several proatherothrombotic conditions are associated with enhanced levels of circulating proinflammatory cytokines, which are believed to impair endothelial fibrinolytic capacity.

OBJECTIVE

This study aims at investigating how tumor necrosis factor (TNF)-alpha regulates endothelial gene expression of the key fibrinolytic enzyme tissue-type plasminogen activator (t-PA).

METHODS

Cultured human umbilical vein endothelial cells were pretreated with selective inhibitors of the three major inflammatory signaling pathways activated by TNF-alpha; the nuclear factor kappa-B (NF-kappaB), the p38 mitogen-activated protein kinase (p38 MAPK), and the c-jun N-terminal kinase (JNK) pathways. Following TNF-alpha stimulation, effects on t-PA gene expression were evaluated with real-time reverse transcriptase polymerase chain reaction and interactions of nuclear proteins with potential gene regulatory elements were studied with electrophoretic mobility shift assays.

RESULTS

Approximately 50% suppression of t-PA gene expression was observed after prolonged stimulation with TNF-alpha (> or =24 h). The repression was shown to be preferentially dependent on NF-kappaB activation, but also on p38 MAPK signaling. Further, we provide evidence for a TNF-alpha induced binding of NF-kappaB to the recently described kappaB site in the t-PA gene and of cyclic adenosine monophosphate response element binding protein (CREB) to the t-PA CRE-like site.

CONCLUSIONS

We conclude that TNF-alpha impairs fibrinolytic capacity in vascular endothelial cells by a NF-kappaB and p38 MAPK-dependent suppression of t-PA. This mechanism sheds a light on how inflammation contributes to the pathogenesis of cardiovascular diseases.

Regulation of local availability of active tissue-type plasminogen activator in vivo in man

Free, biologically active tissue-type plasminogen activator (tPA) is the main initiator of intravascular fibrinolysis, but little is known about the regulation of active tPA on the organ level. The aim was to investigate if the local availability of active tPA on the organ level depends on the local release rate of tPA or the arterial input of tPA and plasminogen activator inhibitor type 1 (PAI-1). Also, we wanted to evaluate if plasma levels predict capacity for endothelial release of fibrinolytic proteins. Invasive perfused-forearm studies were performed in 96 healthy subjects. Local release rates of fibrinolytic proteins were assessed at baseline and during endothelial stimulation. Stimulation by methacholine and desmopressin induced a 6- and 12-fold increase in total tPA release rates, respectively. With increasing local release rates of tPA a gradually closer correlation emerged between the total tPA secretion and the forearm output of active tPA (from r = 0.102, ns to r = 0.85, P < 0.0001). Forearm availability of active tPA was not related to arterial input of either tPA or PAI-1. Release rates and plasma levels of tPA were not correlated. Baseline release rates of active tPA increased to noon. The major determinant for the local availability of active tPA is the capacity of the endothelium to release tPA rather than the arterial input of PAI-1 or tPA. Despite a molar excess of PAI-1, the majority of tPA released during stimulation does not undergo local inactivation. The capacity to release tPA locally cannot be predicted from its plasma concentration.

Regression of electrocardiographic left ventricular hypertrophy predicts regression of echocardiographic left ventricular mass: the LIFE study

The electrocardiogram (ECG) is widely used for detection of left ventricular hypertrophy (LVH). However, whether changes in ECG LVH during antihypertensive therapy predict changes in LV mass remains unclear. Baseline and year-1 ECGs and echocardiograms were assessed in 584 hypertensive patients with ECG LVH by Sokolow-Lyon or Cornell voltage-duration product criteria at entry into the Losartan Intervention For Endpoint reduction in hypertension (LIFE) echocardiographic substudy. A >/=25% decrease in Cornell product defined regression of ECG LVH; a <25% decrease defined no significant regression; and an increase defined progression of ECG LVH. Regression of echocardiographic LVH was defined by a >/=20% reduction in LV mass. After 1 year of therapy, 155 patients (27%) had regression of ECG LVH, 286 (49%) had no significant change, and 143 (25%) had progression of ECG LVH. Compared with patients with progression of ECG LVH, patients with no significant decrease and patients with regression of ECG LVH had stepwise greater absolute decreases in LV mass (-16+/-33 vs -29+/-37 vs -32+/-41 g, P<0.001), greater percent reductions in LV mass (-5.7+/-14.6 vs -11.3+/-13.6 vs -12.3+/-15.6%, P<0.001), and were more likely to decrease LV mass by >/=20% (11.2 vs 24.8 vs 36.1%, P<0.001), even after adjusting for possible effects of baseline and change in systolic and diastolic pressures. Compared with progression of ECG LVH, regression of the Cornell product ECG LVH is associated with greater reduction in LV mass and a greater likelihood of regression of anatomic LVH.

Association of left bundle branch block with left ventricular structure and function in hypertensive patients with left ventricular hypertrophy: the LIFE study

Electrocardiographic (ECG) left bundle branch block (LBBB) is associated with left ventricular hypertrophy (LVH), but its relation to left ventricular (LV) geometry and function in hypertensive patients with ECG LVH is unknown. Echocardiograms were performed in 933 patients (548 women, mean age 66+/-7 years) with essential hypertension and LVH by baseline ECG in the Losartan Intervention For Endpoint reduction in hypertension (LIFE) study. LBBB, defined by Minnesota code 7.1, was present in 47 patients and absent in 886 patients. Patients with and without LBBB were similar in age, gender, body mass index, blood pressure, prevalence of diabetes, and history of myocardial infarction. Despite similarly elevated mean LV mass (126+/-25 vs 124+/-26 g/m(2)) and relative wall thickness (0.41+/-0.07 vs 0.41+/-0.07, P=NS), patients with LBBB had lower LV fractional shortening (30+/-6 vs 34+/-6%), ejection fraction (56+/-10 vs 61+/-8%), midwall shortening (14+/-2 vs 16+/-2%), stress-corrected midwall shortening (90+/-13 vs 97+/-13%) (all P<0.001), and lower LV stroke index (38+/-7 vs 42+/-9 ml/m(2)) (P<0.05). Patients with LBBB also had reduced LV inferior wall and lower mitral E/A ratio (0.75+/-0.18 vs 0.87+/-0.38) (all P<0.05). The above univariate results were confirmed by multivariate analyses adjusted for gender, age, blood pressures, height, weight, body mass index, heart rate, and LV mass index. Among hypertensive patients at high risk because of ECG LVH, the presence of LBBB identifies individuals with worse global and regional LV systolic function and impaired LV relaxation without more severe LVH by echocardiography.

Quantification of ADP and ATP receptor expression in human platelets

The mechanism of ADP-mediated platelet activation has been difficult to unravel due to the large number of receptors for extracellular nucleotides (P2 receptors). mRNA levels in circulating platelets are very low, but have been shown to be translationally active. By optimizing mRNA extraction and using real time (RT)-PCR we were able to establish a protocol for highly sensitive platelet mRNA quantification in human regular blood samples. In platelets from healthy volunteers, only P2X1, P2Y1 and P2Y12 were found in significant levels, with the following order of expression: P2Y12 >> P2X1 > P2Y1. Other P2 receptors (P2Y2, P2Y4, P2Y6, P2Y11, P2Y13, P2X4, P2X7) had very low expression. As a control measurement to exclude contamination, P2 receptors in buffy coat were quantified but had a completely different profile. Incubation in vitro revealed a more rapid degradation rate for P2X1 receptor mRNA than for P2Y1 and P2Y12, indicating that the level of P2X1 may be relatively higher in newly released platelets and in megacaryocytes. In conclusion, we have developed the first protocol for quantifying mRNA expression in human platelets limiting the P2 receptor drug development targets to P2Y12, P2Y1 and P2X1. Furthermore, the method could be used to study platelet expression for any gene in human materials.

Relation of QT interval and QT dispersion to echocardiographic left ventricular hypertrophy and geometric pattern in hypertensive patients. The LIFE study. The Losartan Intervention For Endpoint Reduction

OBJECTIVE

In hypertensive patients, left ventricular hypertrophy (LVH) predicts increased mortality, in part due to an increased incidence of sudden death. Repolarization-related arrhythmogenesis may be an important mechanism of sudden death in hypertensive patients with LVH. Increased QT interval and QT dispersion are electrocardiographic (ECG) measures of ventricular repolarization, and also risk markers for ventricular tachyarrhythmias. We assessed the relation of QT intervals and QT dispersion to echocardiographically determined left ventricular (LV) mass and geometry in a large population of hypertensive patients with ECG evidence of LVH.

METHODS

QT intervals and QT dispersion were determined from baseline 12-lead ECGs in 577 (57% male; mean age 65 +/- 7 years) participants in the LIFE study. LV mass index (LVMI) and geometric pattern were determined by echocardiography and QT interval duration and QT dispersion were assessed in relation to gender-specific LVMI quartiles.

RESULTS

In both genders, increasing LVMI was associated with longer rate-adjusted QT intervals. QT dispersion measures showed a weaker association with LVMI quartiles. Both concentric and eccentric LVH were associated with increased QT interval duration and QT dispersion. These relations remained significant after controlling for relevant clinical variables.

CONCLUSIONS

In hypertensive patients with ECG evidence of LVH, increased LVMI and LVH are associated with a prolonged QT interval and increased QT dispersion. These findings suggest that an increased vulnerability to repolarization-related ventricular arrhythmias might in part explain the increased risk of sudden death in hypertensive patients with increased LV mass.

Relation of echocardiographic left ventricular mass and hypertrophy to persistent electrocardiographic left ventricular hypertrophy in hypertensive patients: the LIFE Study

BACKGROUND

The Losartan Intervention For Endpoint Reduction in Hypertension (LIFE) trial used left ventricular hypertrophy (LVH) on a screening ECG to identify patients at high risk for morbid events. Because of regression to the mean, not all patients who met screening criteria had persistent ECG LVH on the ECG performed at study baseline.

METHODS

The relationship of echocardiographic LV mass and LVH to persistence or loss of ECG LVH between screening and baseline evaluation was examined in 906 hypertensive patients in the LIFE study, who had echocardiograms and additional ECG performed at study baseline. Patients were categorized according to the presence or absence of ECG LVH by Cornell voltage-duration product criteria or Sokolow-Lyon voltage criteria; echocardiographic LVH was defined by LV mass index (LVMI) > 104 g/m2 in women and > 116 g/m2 in men.

RESULTS

A total of 678 patients (75%) had persistent ECG LVH at baseline evaluation. Compared with the 228 patients without ECG LVH on the second ECG by either criterion, the 106 patients with LVH by both Cornell product and Sokolow-Lyon criteria had significantly higher LVMI (140+/-31 v 114+/-21 g/m2, P < .001) and a higher prevalence of echocardiographic LVH (86% v 55%, P < .001). Patients with ECG LVH on the baseline ECG by either Cornell product criteria (n = 410) or Sokolow-Lyon voltage criteria (n = 162) had intermediate values of LVMI (125+/-25 and 121+/-21 g/m2) and prevalences of echocardiographic LVH (78% and 62%). After controlling for possible effects of age, sex, ethnicity, systolic blood pressure, and body mass index, persistence of ECG LVH on the baseline ECG was associated with an increased risk of echocardiographic LVH: compared with patients with neither ECG criteria for LVH, patients with only Sokolow-Lyon voltage criteria had a 1.2-fold increased risk of echocardiographic LVH, those with only Cornell product criteria had a 2.7-fold increased risk, and patients with both ECG criteria had a 4.1-fold increased risk of echocardiographic LVH (P < .001).

CONCLUSIONS

Persistent ECG LVH between screening and LIFE study baseline identified patients with greater LV mass and a higher prevalence of echocardiographic LVH, suggesting that these patients may be at higher risk for subsequent morbid and mortal events.

Relationship of the electrocardiographic strain pattern to left ventricular structure and function in hypertensive patients: the LIFE study. Losartan Intervention For End point

OBJECTIVES

This study was designed to assess the relation of electrocardiographic (ECG) strain to increased left ventricular (LV) mass, independent of its relation to coronary heart disease (CHD).

BACKGROUND

The classic ECG strain pattern, ST depression and T-wave inversion, is a marker for left ventricular hypertrophy (LVH) and adverse prognosis. However, the independence of the relation of strain to increased LV mass from its relation to CHD has not been extensively examined.

METHODS

Electrocardiograms and echocardiograms were examined at study baseline in 886 hypertensive patients with ECG LVH by Cornell voltage-duration product and/or Sokolow-Lyon voltage enrolled in the Losartan Intervention For End point (LIFE) echocardiographic substudy. Strain was defined as a downsloping convex ST segment with inverted asymmetrical T-wave opposite to the QRS axis in leads V5 and/or V6.

RESULTS

Strain occurred in 15% of patients, more commonly in patients with than without evident CHD (29%, 51/175 vs. 11%, 81/711, p < 0.001). When differences in gender, race, diabetes, systolic pressure, serum creatinine and high density lipoprotein cholesterol were controlled, strain on baseline ECG was associated with greater indexed LV mass in patients with (152 +/- 33 vs. 131 +/- 32 g/m2, p < 0.001) or without CHD (131 +/- 24 vs. 119 +/- 22 g/m2, p < 0.001). In logistic regression analyses, strain was associated with an increased risk of anatomic LVH in patients with CHD (relative risk 5.14, 95% confidence interval [CI] 1.16 to 22.85, p = 0.0315), without evident CHD (relative risk 2.91, 95% CI 1.50 to 5.65, p = 0.0016), and in the overall population when CHD was taken into account (relative risk 2.98, 95% CI 1.65 to 5.38, p = 0.0003).

CONCLUSIONS

When clinical evidence of CHD is accounted for, ECG strain is likely to indicate the presence of anatomic LVH. Greater LV mass and higher prevalence of LVH in patients with strain offer insights into the known association of the strain pattern with adverse outcomes.

Extracellular nucleotides ATP and UTP induce a marked acute release of tissue-type plasminogen activator in vivo in man

Extracellular nucleotides such as ATP and UTP are released by activation of platelets and ischemic tissue injury. The aim of the present study was to investigate whether ATP and UTP can induce acute tPA release from the vascular endothelium in vivo. Nine healthy subjects were studied in a perfused-forearm model during stepwise intraarterial infusions of ATP and UTP (10-200 nmol/min), and UTP during inhibition of prostanoid and NO synthesis by indomethacin and L-NMMA. ATP and UTP induced a similar and marked stimulation of forearm tPA release which increased 11- and 18-fold above baseline (p < or =0.01 for both) in conjunction with pronounced vasodilation. Neither the acute tPA release nor the vasodilation could be abrogated by NO and prostanoid synthesis inhibition. The similar effect of ATP and UTP suggests that P2Y rather than adenosine receptors mediate the response. Release of extracellular nucleotides in ischemic tissue may induce a pronounced activation of the endogenous fibrinolytic system.

Baseline characteristics in relation to electrocardiographic left ventricular hypertrophy in hypertensive patients: the Losartan intervention for endpoint reduction (LIFE) in hypertension study. The Life Study Investigators

The Losartan Intervention For Endpoint (LIFE) reduction in hypertension study is a double-blind, prospective, parallel group study designed to compare the effects of losartan with those of atenolol on the reduction of cardiovascular morbidity and mortality. A total of 9194 patients with hypertension and ECG left ventricular hypertrophy (LVH) by Cornell voltage-duration product and/or Sokolow-Lyon voltage criteria were enrolled in the study, with baseline clinical and ECG data available in 8785 patients (54% women; mean age, 67+/-7 years). ECG LVH by Cornell voltage-duration product criteria was present in 5791 patients (65.9%) and by Sokolow-Lyon voltage in 2025 patients (23.1%). Compared with patients without ECG LVH by Cornell voltage-duration product criteria, patients with ECG LVH by this method were older; more obese; more likely to be female, white, and to have never smoked; more likely to be diabetic and have angina; and had slightly higher systolic, diastolic, and pulse blood pressures. In contrast, patients with ECG LVH by Sokolow-Lyon criteria were slightly younger; less obese; more likely to be male, black, and current smokers; less likely to have diabetes; more likely to have angina and a history of cerebrovascular disease; and had higher systolic and pulse blood pressure but slightly lower diastolic blood pressure than patients without ECG LVH by this method. By use of multivariate logistic regression analyses, presence of ECG LVH by Cornell voltage-duration product criteria was predominantly associated with higher body mass index, increased age, and female gender, whereas presence of ECG LVH by Sokolow-Lyon voltage criteria was predominantly related to lower body mass index, male gender, and black race. Thus, hypertensive patients who meet Cornell product and Sokolow-Lyon voltage criteria are associated with different, but potentially equally adverse, risk factor profiles.

Temporal regulation of endothelial ET-1 and eNOS expression in intact human conduit vessels exposed to different intraluminal pressure levels at physiological shear stress

OBJECTIVE

By using a computerized vascular perfusion model, we investigated temporal effects of sub-acute pressure elevation on vasomotor behavior and expression of endothelin-1 (ET-1) and endothelial nitric oxide synthase (eNOS) in intact human conduit vessels.

METHODS

Paired umbilical veins were perfused during 1.5, 3 and 6 h under high/low intraluminal pressure (40/20 mmHg) and at identical shear stress level of 10 dyn/cm(2). ET-1 and eNOS gene and protein expression was quantified with real-time reverse-transcribed polymerase chain reaction and quantitative immunohistochemistry, respectively.

RESULTS

Pressure induced differential temporal regulation patterns of ET-1 and eNOS gene expression. During the high pressure condition, eNOS mRNA was upregulated after 3 h and leveled off after 6 h of perfusion, while ET-1 mRNA was elevated after 6 h perfusion. Immunohistochemistry verified synchronal changes at the protein level. Significant vasodilation was observed after 3 h in the high-pressure system.

CONCLUSION

Thus, subacute pressure elevation exerts differential effects on the endothelial eNOS/ET-1 expression, which dynamically regulate the vasomotor tone.

Forearm blood flow responses to neuropeptide Y, noradrenaline and adenosine 5'-triphosphate in hypertensive and normotensive subjects

Neuropeptide Y (NPY), noradrenaline (NA) and adenosine 5'-triphosphate (ATP) are important co-transmitters in the sympathetic nervous system, which has a central role in cardiovascular control. In order to evaluate if hypertension is associated with alterations in vascular responses to sympathetic co-transmitters we studied the effects of intra-arterial infusion of NPY, NA and ATP on forearm blood flow. Blood flow was measured by venous occlusion plethysmography in six hypertensive (mean arterial blood pressure (MAP) 113 +/- 4 mmHg) and six matched normotensive subjects (MAP 97 +/- 3 mmHg). NPY and NA significantly reduced forearm blood flow, while a powerful increase was seen with ATP. Forearm vascular resistance, calculated as MAP divided by forearm blood flow, was significantly increased by NPY and NA and strongly reduced by ATP. There was no difference between hypertensive and normotensive subjects in response to either transmitter. In conclusion, vascular reactivity to intra-arterial administration of NPY, NA and ATP seems to be intact in hypertensive patients without metabolic aberrations.

Identification of eight novel single-nucleotide polymorphisms at human tissue-type plasminogen activator (t-PA) locus: association with vascular t-PA release in vivo

Recently, we reported that an Alu insertion polymorphism of the tissue-type plasminogen activator (t-PA) gene is associated with vascular t-PA release rates in man. In the current study we searched the t-PA gene for putative functional genetic variants in linkage disequilibrium (LD) with this polymorphism. Healthy individuals with different Alu genotypes and contrasting t-PA release rates were studied. Regulatory and coding regions of the t-PA gene were sequenced. Eight single-nucleotide polymorphisms (SNPs) were identified. Three of these were in significant LD with the Alu polymorphism and consequently associated with t-PA release rates; one in the far upstream enhancer, one in exon 6, and one in intron 10. The enhancer SNP resides within a GC box. Electrophoretic mobility shift assay (EMSA) revealed a reduced binding affinity of Sp1 to the T allele, which is the allele associated with a low t-PA release rate. Variations in exon 6 and intron 10 were silent and without apparent effect on splicing, respectively.

Fluid shear stress increases the intra-cellular storage pool of tissue-type plasminogen activator in intact human conduit vessels

We investigated the effect of shear stress on the expression of tissue-type plasminogen activator (t-PA) in intact human conduit vessels. Human umbilical veins were exposed to high or low shear stress (25 vs < 4 dyn/cm2) at identical intraluminal pressure (20 mmHg) for 1.5, 3, and 6 h in a new computerized biomechanical perfusion system. High shear perfusion induced a marked, time-dependent increase in t-PA immunostaining in both the endothelium and the media. t-PA relative to GAPDH gene expression increased by 54 +/- 14% in high- compared to low-sheared vessels (p = 0.002). By contrast, t-PA release into the perfusion medium was similar in vessels perfused under high or low shear stress conditions. The results show that shear stress independently of pressure is a potent fluid mechanical stimulus for up-regulation of the intracellular storage pool of t-PA in the vascular wall of fresh human conduit vessels. The shear effect is associated with an increased t-PA gene expression.

Differential immediate-early gene responses to shear stress and intraluminal pressure in intact human conduit vessels

We have previously shown distinct effects of shear stress and pressure on transcription of several potent vascular mediators. In the present study, we tested the hypothesis that c-jun and c-fos are regulated differentially by shear and pressure. Intact human umbilical veins were perfused with various combinations of shear and pressure during 1.5, 3 and 6 h. Protein and gene expressions were assessed by immunofluorescence and real-time reverse transcription PCR, respectively. Shear stress and pressure exert differential temporal effects on c-jun and c-fos gene and protein expression, and these immediate-early gene responses appear to be cell-type specific for endothelial and smooth muscle cells.

Distinct regulation of vascular endothelial growth factor in intact human conduit vessels exposed to laminar fluid shear stress and pressure

VEGF is a potent angiogenic factor. We tested the hypothesis that biomechanical forces may regulate VEGF expression. By using a computerized perfusion system, human umbilical veins were exposed to high/low shear stress or intraluminal pressure (25/4 dyn/cm(2) or 40/20 mmHg) for 1.5, 3, or 6 h. Quantification of VEGF gene expression was performed with real-time RT-PCR. VEGF protein was characterized by quantitative immunohistochemistry. All perfusion experiments were performed under identical pH, PO(2), and temperature. Shear stress induced significant biphasic regulation pattern of VEGF (P = 0.0044) with significant downregulation by 45 and 40% after 1.5 and 6 h perfusion, respectively (P = 0.006 and P = 0.0002). The temporal changes of the gene expression were accompanied by synchronal changes at the protein level. High pressure induced transient 25% downregulation of VEGF gene expression after 1.5 h perfusion (P = 0.031). These data provide the first evidence on modulating effects of biomechanical forces on the vascular angiogenic property.

Preserved tissue-type plasminogen activator release and endothelium-dependent vasodilation in postmenopausal women with NIDDM

We have recently shown that the net release of tissue-type plasminogen activator (t-PA) antigen can be rapidly enhanced by the muscarinic receptor stimulation in healthy males. Since diabetes mellitus has been associated with endothelial dysfunction, the aim of the present study was to compare the endothelium-derived local net release of t-PA with vasodilation in response to muscarinic receptor stimulation by metacholine (Mch) and fluid shear stress in a group of postmenopausal women with non-insulin-dependent diabetes mellitus (NIDDM), and to elucidate the influence of estrogen on this process. Six postmenopausal women with NIDDM were in randomized order exposed to step-wise intra-arterial infusions of Mch (0.1-0. 8-4.0 microg/min) and nitroprusside (SNP; 0.5-2.5-10.0 microg/min). Forearm blood flow (FBF) was assessed by plethysmography. The infusions with Mch and SNP were repeated during simultaneous intra-arterial infusion of 17-beta estradiol (E; 20 ng/min). During placebo infusion, FBF increased significantly in response to Mch and SNP (p<0.001), but no differences between Mch and SNP were found. In parallel to the blood flow increase in response to Mch stimulation, the t-PA net release was increased over 30 times (p<0.001). Estrogen did not produce any change in blood flow or net release of t-PA at baseline or in response to either drug (Mch or SNP). The present study demonstrates a preserved endothelium-dependent vasodilation and stimulated tissue-type plasminogen activator release in NIDDM postmenopausal women in response to Mch stimulation. Acute intra-arterial infusion of 17-beta estradiol did not affect the vasodilation or the t-PA net release.

Elevated intraluminal pressure inhibits vascular tissue plasminogen activator secretion and downregulates its gene expression

We recently discovered that patients with essential hypertension have a markedly impaired capacity for stimulated release of tissue plasminogen activator (tPA) from vascular endothelium. This defect may reduce the chance of timely spontaneous thrombolysis in case of an atherothrombotic event. We now investigated whether increased intraluminal pressure as such may depress vascular tPA release or downregulate its gene expression. Segments of human umbilical veins were studied in a new computerized vascular perfusion model under steady laminar flow conditions for 3 or 6 hours. Paired segments were perfused at high or physiological intraluminal pressure (40 versus 20 mm Hg) under identical shear stress (10 dyne/cm(2)). Quantitative immunohistochemical evaluation of cellular tPA immunoreactivity was performed on paraffin-embedded 5-microm vascular sections. tPA mRNA in endothelial cells was quantified with reverse transcription real-time TaqMan polymerase chain reaction with GAPDH as endogenous control. Secretion of tPA into perfusion medium was evaluated with SDS-PAGE and Western blotting, followed by densitometric quantification. High-pressure perfusion downregulated tPA gene expression with a 38% decrease in tPA mRNA levels (P=0.01) compared with vessels perfused under normal intraluminal pressure. tPA release into the perfusion medium was markedly suppressed by high pressure (P<0.01 ANOVA). The intracellular storage pool of tPA was reduced after 6 but not 3 hours. Thus, elevated intraluminal pressure downregulates tPA gene and protein expression and inhibits its release from the endothelium independently of shear stress. The defective capacity for stimulated tPA release that we demonstrated in patients with essential hypertension might thus be an effect of the elevated intraluminal pressure per se.

Effects of shear stress on eicosanoid gene expression and metabolite production in vascular endothelium as studied in a novel biomechanical perfusion model

This study investigated the effects of shear stress on gene expression of prostacyclin synthesis-related enzymes cyclooxygenases (COX-1 and COX-2), prostacyclin synthase (PGS), and thromboxane synthase (TXS) and their metabolites prostaglandin (PGI(2)) and thromboxane A(2) (TXA(2)) in endothelium of intact conduit vessels. Paired human umbilical veins were perfused at high/low shear stress (25/<4 dyn/cm(2)) at identical intraluminal pressure (20 mmHg) for 1.5, 3, or 6 hours in a computerized vascular model. High shear perfusion induced a significant, monophasic upregulation of PGS and TXS gene expressions after 6 hours. COX-1 and COX-2 mRNA showed a biphasic response with peaks at 1.5 and 6 hours, with a nadir level at 3 hours. Shear-induced gene expression was associated with a significantly greater accumulation of 6-keto prostaglandin F(1alpha) and TXA(2) in the perfusion medium. Thus, shear stress independently of perfusion pressure alters the expression of prostacyclin synthesis-related enzymes and the biosynthesis of their vasoactive metabolites.

Effect of obesity on electrocardiographic left ventricular hypertrophy in hypertensive patients : the losartan intervention for endpoint (LIFE) reduction in hypertension study

Obesity may limit sensitivity of ECG voltage criteria for left ventricular hypertrophy (LVH) because of the attenuating effects of increased body mass on precordial voltages. However, obesity is associated with an increased prevalence of anatomic LVH, making more accurate ECG criteria in obese patients a clinical priority. ECG LVH by Cornell voltage-duration product and/or Sokolow-Lyon voltage criteria was used to select patients for the Losartan Intervention For Endpoint (LIFE) Reduction in Hypertension Study. Clinical and ECG data were available in 8417 patients (54% women; mean age, 67+/-7 years); 2519 were overweight and 1573 were obese by gender-specific body mass index criteria. Increased body mass index had significant but directionally opposite effects on ECG LVH by these 2 criteria. Compared with normal-weight patients, obese and overweight patients had lower Sokolow-Lyon voltage and a lower prevalence of ECG LVH by Sokolow-Lyon criteria (10.9% versus 16.2% versus 31.4%; P<0.001). In contrast, obese and overweight patients had higher mean values of the Cornell product and higher prevalences of ECG LVH by this criterion (75.1% versus 69.9% versus 60.7%; P<0. 001). After adjustment for age, gender, race, myocardial infarction, and diastolic and pulse pressure with the use of logistic regression analysis, increased body mass remained highly predictive of the presence of ECG LVH. Compared with normal-weight patients, obese patients had a >2-fold higher risk of ECG LVH by the Cornell product but a 4-fold lower risk of ECG LVH by Sokolow-Lyon voltage; overweight status was associated with intermediate risks, with a 151% greater likelihood of ECG LVH by the Cornell product but only 44% of the risk of LVH by Sokolow-Lyon voltage criteria compared with normal-weight individuals. Thus, Sokolow-Lyon voltage criteria underestimate the prevalence of anatomic LVH in the presence of obesity, whereas Cornell product criteria for ECG LVH appear to provide a more accurate measure of LVH in obese and overweight patients.

Systemic levels and preportal organ release of tissue-type plasminogen activator are enhanced by PEEP in the pig

BACKGROUND

Endothelium-derived tissue-type plasminogen activator, t-PA, is the key enzyme in the initiation of endogenous thrombolysis. Plasma levels of t-PA increase in response to sympatho-adrenergic activation. In the mesenteric vascular bed an increased norepinephrine spillover has been observed during positive end-expiratory pressure ventilation, PEEP. This experimental study examines the effects of PEEP-induced alterations on regional release rates and systemic levels of t-PA in vivo.

METHODS

The protocol included measurements of arterio-venous concentration gradients of t-PA and the respective plasma flow across the pulmonary, coronary, hepatic and preportal vascular beds, in pigs, during zero-PEEP and at 2, 4 and 10 min after the application of a PEEP of 10 cm H2O. Both total plasma t-PA antigen (ELISA with a porcine t-PA standard) and active t-PA (spectrophotometric functional assay) were determined.

RESULTS

During zero-PEEP, a high preportal basal net release and hepatic net uptake of total t-PA was observed. With PEEP, the magnitude of the preportal net release of t-PA was markedly enhanced (+24+/-5%), as was hepatic net uptake (+21+/-8%), simultaneously to a significant decrease in liver plasma flow (-30+/-2%). PEEP-induced alterations in active t-PA mirrored those observed in total t-PA. No significant net fluxes of total or active t-PA were observed across the coronary or the pulmonary vascular beds.

CONCLUSIONS

Clinically used levels of PEEP induce increases in net release of endothelially derived t-PA within preportal organs. The application of PEEP is associated with increased systemic levels of total and active t-PA, in spite of a simultaneous increase in hepatic net uptake, indicating that the preportal vascular bed can not account for the systemic t-PA response.

Gene polymorphism of t-PA is associated with forearm vascular release rate of t-PA

We have observed marked interindividual differences in release rates of tissue-type plasminogen activator (t-PA) among healthy subjects. The objective of the current study was to test the hypothesis that there is an association between a genetic variation at the t-PA locus and the in vivo release rate of t-PA. Fifty-one healthy males were studied at rest in the morning and 27 of these were also subjected to a mental stress test. Net release rates of total t-PA across the forearm vascular bed were calculated as the product of the venoarterial concentration gradient and forearm plasma flow. Zygosity for an Alu-repeat polymorphism in intron 8 of the t-PA gene was determined by a polymerase chain reaction. Basal t-PA release rates differed markedly by genotype (ANOVA, P<0.05); subjects homozygous for the insertion had a significantly higher release rate (mean 10.9 ng. min-1. L-1, n=19) than both heterozygotes (4.5 ng. min-1. L-1, n=26) and subjects homozygous for the deletion (0.9 ng. min-1. L-1, n=6). After 2 minutes of mental stress release rates had increased approximately 2-fold in all groups. Arterial and venous plasma levels of t-PA were unrelated to genotype. In conclusion, the current results provide the first evidence of an association between a common genetic variation at the t-PA locus and interindividual differences in net release rates of t-PA in vivo. The relationship is not reflected by circulating steady-state plasma levels and can thus not be disclosed by conventional venous plasma sampling.

A new computerized biomechanical perfusion model for ex vivo study of fluid mechanical forces in intact conduit vessels

We have developed a new computerized biomechanical ex vivo perfusion system for intact conduit vessels in which a wide range of combinations of intraluminal pressure, fluid flow and shear stress could be set and maintained at target levels in mammalian conduit vessels under controlled metabolic conditions. Mean wall shear stress is calculated using the formula: Accuracy of the wall shear stress calculation was validated by ultrasonographic imaging of the vessel radius. In a series of simulation experiments, the hemodynamic homeostasis functions of the system were challenged by generating a wide range of vascular resistance in artificial vessels and by pharmacologically induced changes in vascular tone in intact human vessels. Despite rapid changes in vessel resistance, shear stress and pressure, or flow and pressure were maintained well at target levels. Shear- and pressure-stimulated production of the vasodilator prostaglandin E2 (PGE2) was used to validate the biological relevance of the model. PGE2 release was significantly more stimulated by high (25 dyn/cm2) compared to low (<4 dyn/cm2) shear (ANOVA, p = 0.012). High compared to low intraluminal pressure depressed the production of PGE2 (ANOVA, p = 0.019). In summary, the computerized perfusion model appears to offer new possibilities of investigating the complex interplay between fluid mechanics and the vascular wall.

Comparison of effects of quinapril and metoprolol on glycaemic control, serum lipids, blood pressure, albuminuria and quality of life in non-insulin-dependent diabetes mellitus patients with hypertension. Swedish Quinapril Group

OBJECTIVE

To compare the long-term effects of the angiotensin-converting enzyme (ACE)-inhibitor quinapril and the cardioselective beta-adrenergic blocking agent metoprolol on glycaemic control, with glycosylated haemoglobin (HbA1c) as the principal variable, in non-insulin-dependent diabetes mellitus (NIDDM) patients with hypertension.

DESIGN

A randomized, double-blind, double-dummy, multicentre study during 6 months preceded by a 4 week wash-out and a 3 week run-in placebo period. Quinapril (20 mg) and metoprolol (100 mg, conventional tablets) were given once daily. No change was made in the treatment of diabetes (diet and hypoglycaemic agents).

SUBJECTS

Seventy-two patients fulfilling the criteria were randomized and entered the double-blind period. Twelve patients did not complete the study. Sixty patients, 26 on quinapril and 34 on metoprolol, were available for the final analysis.

MAIN OUTCOME MEASURES

The effect was assessed by changes in HbA1c, the fasting serum glucose and the post-load serum glucose, C-peptide and insulin levels during the oral glucose tolerance test.

RESULTS

In the quinapril group, the fasting serum glucose, oral glucose tolerance and the C-peptide and insulin responses, determined as the incremental area under the curves (AUC), showed no change, but the mean HbA1c level increased from 6.2 +/- 1.1% to 6.5 +/- 1.3% (P < 0.05). In the metoprolol group, the rise in the mean level of HbA1c, from 6.3 +/- 1.0% to 6.8 +/- 1.3% (P < 0.01), tended to be more marked than after quinapril, although there was no significant difference between the increments. The mean fasting serum glucose showed an increase from 9.1 +/- 1.9 mM to 10.1 +/- 2.8 mM (P < 0.01) which correlated significantly with the duration of diabetes (P < 0.01) and the increase in fasting serum triglycerides (P < 0.001). Moreover, in the metoprolol group we found significant decreases in the oral glucose tolerance as well as C-peptide and insulin responses to the glucose load.

CONCLUSIONS

Treatment with quinapril for 6 months appears to have advantages over metoprolol in NIDDM patients with hypertension. Although treatment with quinapril or metoprolol over 6 months was concomitant with a rise in the HbA1c, increased fasting blood glucose, decreased oral glucose tolerance and decreased C-peptide and insulin responses to a glucose challenge were observed only in patients treated with metoprolol.

Assessment of left ventricular hypertrophy in patients with essential hypertension

By virtue of its potency as a cardiovascular risk indicator, the presence of left ventricular hypertrophy (LVH) in a patient with hypertension deserves serious attention and make its diagnosis a clinical priority. In view of its prognostic impact, an argument could be made for routine assessment of this intermediate endpoint in each patient with essential hypertension. Two diagnostic approaches are available for screening evaluation of hypertensive patients; either a limited echocardiographic examination or an ECG-based LVH assessment. Recently developed new or combined criteria have significantly improved the diagnostic performance of ECG criteria, and evolving data show that accurate estimation of LVH can be performed by ECG screening in a majority of patients. At present, ECG evaluation based either on sex-specific orthogonal-lead time-voltage criteria or on the combined standard 12-lead criteria of Sokolow-Lyon (sum of S in V1 and R in V5 or V6) or Cornell Product (product of sum of R in aVL and S in V3 + 6 mm in females and QRS duration) demonstrates the best overall diagnostic accuracy. With orthogonal criteria, the sensitivity is 81% in women and 71% in men at a matched 98% specificity. The corresponding overall sensitivity of the combined Cornell Product or Sokolow-Lyon criteria is reported to be 68% at a specificity of 96.6%. What speaks in favour of the echocardiographic approach is its superior sensitivity and the possibility of gaining additional potential risk information associated with the geometric pattern of the LVH. However, its general availability makes electrocardiography a cost-effective diagnostic alternative with which to follow the progression or regression of LVH in hypertensive patients.

Evidence of a local mechanism for desmopressin-induced tissue-type plasminogen activator release in human forearm

Systemic administration of desmopressin (DDAVP) induces increased plasma levels of tissue-type plasminogen activator (t-PA), coagulation factor VIII, and von Willebrand factor (vWF). However, the mechanisms behind these responses are not known. We tested the hypothesis that DDAVP acts as a local stimulator of acute endothelial release of t-PA and vWF independently of central pathways. Healthy, young, nonsmoking male volunteers were studied. In a first study (n = 7), DDAVP and placebo were administered as randomized single-blind stepwise intrabrachial artery infusions (0.7, 7.0, and 70 ng/min). In a another subset of subjects (n = 4), a constant-rate DDAVP infusion of 70 ng/min was administered for 20 minutes in the brachial artery of the nondominant arm with the dominant arm as control. To rule out that the observed t-PA release was flow-dependent, 4 additional subjects received stepwise intra-arterial infusions of both DDAVP (7.0, 21, and 70 ng/min) and sodium nitroprusside (SNP; 0.5, 2.5, and 10 micrograms/min). Brachial venoarterial plasma concentration gradients and forearm plasma flow were used to determine net release/uptake rates of t-PA and vWF. At baseline, the average net release rate of t-PA was 6.7 ng/min across the whole forearm vascular bed, whereas there was no detectable basal release of vWF. Stepwise infusion of DDAVP induced a massive regulated release of t-PA with a peak after 15 minutes on the highest dose-step (ANOVA; P < .0001). The average maximum net release rate was 178 ng/min, and the total amount of t-PA released was, on the average, 3,000 ng. The majority was released in its active form. Constant-rate DDAVP infusion again markedly increased t-PA release in the infusion arm but had no effect whatsoever in the control arm. In contrast, DDAVP did not stimulate a local release of vWF in either study. Central hemodynamics were unchanged during infusions despite a local vasodilatory response with DDAVP. Endothelium-independent flow stimulation by SNP did not elicit any local t-PA release. We conclude that DDAVP induces a massive acute flow-independent release of t-PA, without the simultaneous release of vWF, in the human forearm vascular bed. The lack of a t-PA response in the control arm, as well as the unaltered central hemodynamics with DDAVP, confirms that the observed regulated t-PA release is local and independent of central mechanisms.

Comparison of cardiovascular risk profile between male employees of two automotives companies in France and Sweden. The Coeur Project Group

To determine whether or not the lower rate of coronary disease in France, in comparison with Sweden, might be explained by different cardiovascular risk profiles, a cross-sectional analysis (first step of a longitudinal study) of comparable samples of automotive workers was carried out in corporate occupational health clinics of Renault and Volvo. Traditional cardiovascular risk factors were evaluated and the Framingham coronary risk was estimated for 1000 randomly selected 45-50 years old Caucasian males from each company. Compared with the Frenchmen, the Swedish men consisted of more white collar workers and were slightly older. After adjustment for age and blue/white collar status, the Swedish men showed lower body mass indexes, waist to hip rations and heart rates, lower frequency of treatment of hypercholesterolemia and diabetes than the Frenchmen. The Swedish males also exhibited higher averages of blood cholesterol, low density lipoprotein (LDL) cholesterol and glucose, but lower frequencies of hypercholestrolemia and diabetes, and a higher frequency of family histories of cardiovascular disease. Blood pressure, hypertension prevalence, triglycerides level, and high density lipoprotein (HDL) did not differ between the groups. The average number of traditional risk factors was 1.1/person for the Frenchmen and 0.8/person for the Swedes. However, the coronary risk as estimated using the Framingham index was not different between the groups. This, together with the more frequent family history of cardiovascular disease in Swedish men, suggests a lower susceptibility to risk factors as a possible explanation for the lower cardiovascular disease prevalence reported in France, and/or the possibility that factors not measured were involved.

High capacity for tissue-type plasminogen activator release from vascular endothelium in vivo

BACKGROUND

Tissue-type plasminogen activator (t-PA) is the key mediator of intravascular fibrinolysis. We showed recently that local administrations both of methacholine (MCH) and of desmopressin (1-desamino-8-D-arginine vasopressin, DDAVP) induced a massive local release of t-PA in the human forearm vasculature.

OBJECTIVE

To determine whether the human vascular endothelium could respond to repeated stimulation with the same agonist, and, if so, to further evaluate the releasable endothelial pool of t-PA.

METHOD

Seven young, healthy men participated. MCH and DDAVP were administered as local infusions into the brachial artery. In protocol 1 (n = 3) 2 microg/min MCH was infused for 2 (30 min with a free interval of 20 min). In protocol 2 (n = 4) 70 ng/min DDAVP was infused for 2 (20 min with an interval of 75 min). Dosages and time intervals were based on the different release profiles of the two drugs observed in previous studies. Brachial arterial and venous blood samples were obtained at baseline and throughout infusions. Net release of t-PA was calculated as the product of the arteriovenous concentration gradient and forearm plasma flow.

RESULTS

Forearm blood flow was increased 3-4-fold by MCH and 2-3-fold by DDAVP infusions. During the first and second infusions of MCH, the average amounts of t-PA released were 1600 and 1000 ng/l forearm tissue, respectively. In contrast, DDAVP induced similar t-PA responses during both infusions; the average total releases of t-PA were 2300 and 2400 ng/l tissue, respectively.

CONCLUSION

The results show that the vascular endothelium is responsive to repeated stimulation both with MCH and with DDAVP. The diminished t-PA response to the second MCH infusion can not be explained in terms of depletion of intracellular pools, in view of the large amount of t-PA released by a single infusion of DDAVP. The dynamic pool of t-PA available for release is very large, but further studies are required in order to quantify the releasable endothelial stores.

Endothelium-dependent vasodilation and tissue-type plasminogen activator release in borderline hypertension

We recently showed that muscarinic receptor stimulation causes a marked increase in the net release of tissue-type plasminogen activator (TPA) antigen and activity across the human forearm in vivo, in conjunction with endothelium-dependent vasodilation. Because hypertension has been associated with endothelial dysfunction, the aim of the study was to compare forearm TPA release and vasodilation in response to muscarinic stimulation in normotensive (NC) and borderline hypertensive (BH) subjects. The study was performed in 10 apparently healthy young men with BH and 10 male NC subjects. Methacholine (MCh: 0.1, 0.8, and 4.0 micrograms/min) and sodium mitroprusside (SNP: 0.5, 2.5, and 10 micrograms/min) were administered in randomized order as double-blind, stepwise, intrabrachial artery infusions. Forearm blood flow was assessed by plethysmography. Net release/uptake was calculated as the product of the arteriovenous concentration gradient and forearm plasma flow. Vasodilator responses to MCh were similar in both groups (P = NS), whereas the decrease in forearm vascular resistance in response to SNP was somewhat less in BH subjects (P = .005). At rest, both groups showed a significant arteriovenous gradient and net release of TPA antigen across the forearm (P < .05 throughout). However, in contrast to the significant net increment in TPA activity across the forearm in the NC group (P < .018), BH subjects had no basal forearm increment in TPA activity (NC vs BH, P = .006). Arterial and venous plasma levels of plasminogen activator inhibitor 1 (PAI-1) antigen and activity were higher in BH subjects (P < or = .05 throughout), who in contrast to NC subjects, also had a significant forearm net release of PAI-1 antigen (P = .006). Across the whole group, there was a significant inverse relation between arterial PAI-1 antigen levels and increment in TPA activity across the forearm (r = -.57, P = .008) but no relation to TPA antigen release. In response to MCh infusion, both the net release of TPA antigen and increment in TPA activity increased markedly and to similar extents in both groups (P < .01 throughout). SNP infusion had no effect on either TPA antigen release or increment in TPA activity in the NC group but elicited a significant net release of TPA antigen and increase in TPA activity in the BH group (P < .05). Both circulating levels and local release of PAI-1 antigen were significantly correlated to fasting plasma insulin. Endothelium-dependent vasodilation and endothelial TPA release in response to muscarinic receptor stimulation were preserved in BH subjects. At rest, BH subjects had higher circulating PAI-1 antigen levels and a corresponding decrease in circulating levels and local increment of TPA activity. In contrast to NC subjects, BH subjects responded with a TPA release also in response to increased flow, which may indicate an enhanced endothelial cell responsiveness to fluid shear stress.