Hypo-fibrinolysis in patients with hypertension and elevated cholesterol

Connecting impaired fibrinolysis and dyslipidemia

A State of the Art lecture entitled "Connecting Fibrinolysis and Dyslipidemia" was presented at the International Society on Thrombosis and Haemostasis Congress 2023. Hemostasis balances the consequences of blood clotting and bleeding. This balance relies on the proper formation of blood clots, as well as the breakdown of blood clots. The primary mechanism that breaks down blood clots is fibrinolysis, where the fibrin net becomes lysed and the blood clot dissolves. Dyslipidemia is a condition where blood lipid and lipoprotein levels are abnormal. Here, we review studies that observed connections between impaired fibrinolysis and dyslipidemia. We also summarize the different correlations between thrombosis and dyslipidemia in different racial and ethnic groups. Finally, we summarize relevant and new findings on this topic presented during the 2023 International Society on Thrombosis and Haemostasis Congress. More studies are needed to investigate the mechanistic connections between impaired fibrinolysis and dyslipidemia and whether these mechanisms differ in racially and ethnically diverse populations.

Intracellular tPA-PAI-1 interaction determines VLDL assembly in hepatocytes

Apolipoprotein B (apoB)-lipoproteins initiate and promote atherosclerotic cardiovascular disease. Plasma tissue plasminogen activator (tPA) activity is negatively associated with atherogenic apoB-lipoprotein cholesterol levels in humans, but the mechanisms are unknown. We found that tPA, partially through the lysine-binding site on its Kringle 2 domain, binds to the N terminus of apoB, blocking the interaction between apoB and microsomal triglyceride transfer protein (MTP) in hepatocytes, thereby reducing very-low-density lipoprotein (VLDL) assembly and plasma apoB-lipoprotein cholesterol levels. Plasminogen activator inhibitor 1 (PAI-1) sequesters tPA away from apoB and increases VLDL assembly. Humans with PAI-1 deficiency have smaller VLDL particles and lower plasma levels of apoB-lipoprotein cholesterol. These results suggest a mechanism that fine-tunes VLDL assembly by intracellular interactions among tPA, PAI-1, and apoB in hepatocytes.

Plasma tissue-type plasminogen activator is associated with lipoprotein(a) and clinical outcomes in hospitalized patients with COVID-19

Background

Patients with COVID-19 have a higher risk of thrombosis and thromboembolism, but the underlying mechanism(s) remain to be fully elucidated. In patients with COVID-19, high lipoprotein(a) (Lp(a)) is positively associated with the risk of ischemic heart disease. Lp(a), composed of an apoB-containing particle and apolipoprotein(a) (apo(a)), inhibits the key fibrinolytic enzyme, tissue-type plasminogen activator (tPA). However, whether the higher Lp(a) associates with lower tPA activity, the longitudinal changes of these parameters in hospitalized patients with COVID-19, and their correlation with clinical outcomes are unknown.

Objectives

To assess if Lp(a) associates with lower tPA activity in COVID-19 patients, and how in COVID-19 populations Lp(a) and tPA change post infection.

Methods

Endogenous tPA enzymatic activity, tPA or Lp(a) concentration were measured in plasma from hospitalized patients with and without COVID-19. The association between plasma tPA and adverse clinical outcomes was assessed.

Results

In hospitalized patients with COVID-19, we found lower tPA enzymatic activity and higher plasma Lp(a) than that in non-COVID-19 controls. During hospitalization, Lp(a) increased and tPA activity decreased, which associates with mortality. Among those who survived, Lp(a) decreased and tPA enzymatic activity increased during recovery. In patients with COVID-19, tPA activity is inversely correlated with tPA concentrations, thus, in another larger COVID-19 cohort, we utilized plasma tPA concentration as a surrogate to inversely reflect tPA activity. The tPA concentration was positively associated with death, disease severity, plasma inflammatory, and prothrombotic markers, and with length of hospitalization among those who were discharged.

Conclusion

High Lp(a) concentration provides a possible explanation for low endogenous tPA enzymatic activity, and poor clinical outcomes in patients with COVID-19.

Assays to quantify fibrinolysis: strengths and limitations. Communication from the International Society on Thrombosis and Haemostasis Scientific and Standardization Committee on fibrinolysis

Fibrinolysis is a series of enzymatic reactions that degrade insoluble fibrin. Plasminogen activators convert the zymogen plasminogen to the active serine protease plasmin, which cleaves and solubilizes crosslinked fibrin clots into fibrin degradation products. The quantity and quality of fibrinolytic enzymes, their respective inhibitors, and clot structure determine overall fibrinolysis. The quantity of protein can be measured by antigen-based assays, and both quantity and quality can be assessed using functional assays. Furthermore, variations of commonly used assays have been reported, which are tailored to address the role(s) of specific fibrinolytic factors and cellular elements (eg, platelets, neutrophils, and red blood cells). Although the concentration and/or activity of a protein can be quantified, how these individual components contribute to the overall fibrinolysis outcome can be challenging to determine. This difficulty is due to temporal changes within and around the thrombi during the clot breakdown, particularly the fibrin matrix structure, and composition. Furthermore, terms such as "fibrinolytic activity/potential," "plasminogen activation," and "plasmin activity" are often used interchangeably despite having different definitions. The purpose of this review is to 1) summarize the assays measuring fibrinolysis activity and potential, 2) facilitate the interpretation of data generated by these assays, and 3) summarize the strengths and limitations of these assays.

The Acute and Chronic Effects of Resistance and Aerobic Exercise in Hemostatic Balance: A Brief Review

Hemostatic balance refers to the dynamic balance between blood clot formation (coagulation), blood clot dissolution (fibrinolysis), anticoagulation, and innate immunity. Although regular habitual exercise may lower the incidence of cardiovascular diseases (CVD) by improving an individual’s hemostatic profile at rest and during exertion, vigorous exercise may increase the risk of sudden cardiac death and venous thromboembolism (VTE). This literature review aims to investigate the hemostatic system’s acute and chronic adaptive responses to different types of exercise in healthy and patient populations. Compared to athletes, sedentary healthy individuals demonstrate similar post-exercise responses in platelet function and coagulatory and fibrinolytic potential. However, hemostatic adaptations of patients with chronic diseases in regular training is a promising field. Despite the increased risk of thrombotic events during an acute bout of vigorous exercise, regular exposure to high-intensity exercise might desensitize exercise-induced platelet aggregation, moderate coagulatory parameters, and up-regulate fibrinolytic potential via increasing tissue plasminogen activator (tPA) and decreasing plasminogen activator inhibitor (PAI-1) response. Future research might focus on combining different types of exercise, manipulating each training characteristic (frequency, intensity, time, and volume), or investigating the minimal exercise dosage required to maintain hemostatic balance, especially in patients with various health conditions.

Regular Resistance Training Enhances Fibrinolytic Potential but Does Not Affect Coagulation

PURPOSE

This study aimed to identify effects of an 8-wk, whole-body RT program on coagulation and fibrinolysis.

METHODS

Sixteen healthy women and men (23 ± 5 yr) completed an RT program three times per week for 8 wk. Exercises included 2-3 sets of 8-12 repetitions performed at approximately 60%-80% of a one repetition maximum. Strength, body composition, and body circumferences were assessed before and after training. Plasma samples were obtained before and after training, and analyzed for active tissue plasminogen activator (tPA activity), total tissue plasminogen activator (tPA antigen), active plasminogen activator inhibitor-1 (PAI-1 activity), total plasminogen activator inhibitor-1 (PAI-1 antigen), fibrinogen, and coagulation factors VII (FVII) and VIII (FVIII).

RESULTS

Significant increases in lean mass, arm and thigh circumferences, maximal chest press (PRE: 57.8 ± 37.5 kg, POST: 73.3 ± 43.2 kg), and leg press (PRE: 189.5 ± 96.0 kg, POST: 256.7 ± 97.9 kg) were observed (P < 0.05 for all). PAI-1 activity (PRE: 20.3 ± 32.5 IU·mL-1, POST 9.5 ± 20.9 IU·mL-1) and PAI-1 antigen decreased (PRE: 10.2 ± 9.0 ng·dL-1, POST: 7.2 ± 5.7 ng·dL-1; both, P < 0.05). No change in tPA activity or tPA antigen occurred. Fibrinogen, FVII, and FVIII did not change after training.

CONCLUSIONS

Inhibition of fibrinolysis was decreased after training, and coagulation was unaffected. These results suggest that regular RT may beneficially influence the risk of a thrombotic event. More research is warranted to understand the mechanisms through which RT affects hemostasis.

Effects of Angiotensin-Converting Enzyme Inhibition and Alpha 1-Adrenergic Receptor Blockade on Inflammation and Hemostasis in Human Hypertension

Drugs blocking the renin-angiotensin-aldosterone system may offer benefit on endothelial function, inflammation, and hemostasis in addition to the effects of reducing blood pressure. We examined the contribution of the angiotensin-converting enzyme inhibitor ramipril and the alpha 1-adrenergic receptor blocker doxazosin on blood pressure and on markers of inflammation and hemostasis in 59 individuals with mild-to-moderate hypertension randomized to receive double-blind ramipril 10 mg od or doxazosin 8 mg od for 12 weeks. Inflammatory markers (interleukin-6, soluble interleukin-6 receptor, interleukin-8, tumor necrosis factor-α, monocyte chemoattractant protein-1, and C-reactive protein) and hemostasis (plasminogen activator inhibitor-1 activity, tissue plasminogen activator antigen, thrombin-antithrombin complex, and thrombin generation by calibrated automated thrombogram) were assessed. The treatment reduced blood pressure in both groups. Thrombin-antithrombin complex decreased by treatment, and this was dependent on a reduction in thrombin-antithrombin complex in the ramipril group alone. There were no changes in plasminogen activator inhibitor-1 activity, whereas tissue plasminogen activator antigen increased by ramipril and decreased by doxazosin. Only minor changes were observed in systemic inflammation by treatment. Treatment with ramipril seems to reduce thrombin generation beyond effects on reducing blood pressure. Drugs blocking the renin-angiotensin-aldosterone system may reduce atherothrombotic complications beyond their effects to reduce blood pressure.

Effects of blood flow restriction exercise on hemostasis: a systematic review of randomized and non-randomized trials

Background

Blood flow restriction (BFR) exercise has shown to induce a positive influence on bone metabolism and attenuate muscle strength loss and atrophy in subjects suffering from musculoskeletal weakness. Despite the known benefits of BFR exercise, it remains unclear whether or not the pressurization of blood vessels damages the endothelial cells or increases risk for formation of thrombi. Thus, the effects of BFR exercise on coagulation, fibrinolysis, or hemostasis, remains speculative.

Objective

The aim of the present study was to perform a systematic review of the short and long- term effects of BFR exercise on blood hemostasis in healthy individuals and patients with known disease (ie, hypertension, diabetes, obesity, and ischemic heart disease).

Data Sources

A systematic review of English and non-English articles was conducted across PubMed, Science Direct, and Google Scholar databases, including reference lists of relevant papers. Study quality assessment was evaluated using the modified version of Downs and Black checklist. Search results were limited to exercise training studies investigating the effects of BFR exercise on blood hemostasis in healthy individuals and patients with disease. Level of evidence was determined according to the criteria described by Oxford Center for Evidence-Based Medicine.

Study selection

Only randomized controlled trials (RCTs) and non-randomized controlled trials (NRCTs) that examined the effects of exercise with BFR exercise vs exercises without BFR on blood hemostasis in healthy individuals and patients were included.

Data extraction

Nine studies were eligible (RCT =4; NRCT =5).

Results

The average score on the Downs and Black checklist was 11.22. All studies were classified as having poor methodological quality wherein the level of evidence provided in all reviewed studies was level IIb only (ie, poor quality RCTs).

Conclusion

Considering the limitations in the available evidence, firm recommendations cannot be provided.

An ATF6-tPA pathway in hepatocytes contributes to systemic fibrinolysis and is repressed by DACH1

Tissue-type plasminogen activator (tPA) is a major mediator of fibrinolysis and, thereby, prevents excessive coagulation without compromising hemostasis. Studies on tPA regulation have focused on its acute local release by vascular cells in response to injury or other stimuli. However, very little is known about sources, regulation, and fibrinolytic function of noninjury-induced systemic plasma tPA. We explore the role and regulation of hepatocyte-derived tPA as a source of basal plasma tPA activity and as a contributor to fibrinolysis after vascular injury. We show that hepatocyte tPA is downregulated by a pathway in which the corepressor DACH1 represses ATF6, which is an inducer of the tPA gene Plat Hepatocyte-DACH1-knockout mice show increases in liver Plat, circulating tPA, fibrinolytic activity, bleeding time, and time to thrombosis, which are reversed by silencing hepatocyte Plat Conversely, hepatocyte-ATF6-knockout mice show decreases in these parameters. The inverse correlation between DACH1 and ATF6/PLAT is conserved in human liver. These findings reveal a regulated pathway in hepatocytes that contributes to basal circulating levels of tPA and to fibrinolysis after vascular injury.

Effects of Modified Qing'e Pill () on expression of adiponectin, bone morphogenetic protein 2 and coagulation-related factors in patients with nontraumatic osteonecrosis of femoral head

OBJECTIVES

To observe the regulation of Chinese herbal medicine, Modifified Qing'e Pill (, MQEP), on the expression of adiponectin, bone morphogenetic protein 2 (BMP2), osteoprotegerin (OPG) and other potentially relevant risk factors in patients with nontraumatic osteonecrosis of the femoral head (ONFH).

METHODS

A total of 96 patients with nontraumatic ONFH were unequal randomly divided into treatment group (60 cases) and control group (36 cases). The treatment group were treated with MQEP while the control group were treated with simulated pills. Both groups were given caltrate D. Six months were taken as a treatment course. Patients were followed up every 2 months. The levels of plasma adiponectin, BMP2, OPG, von Willebrand factor (vWF), von Willebrand factor cleaving protease (vWF-cp), plasminogen activator inhibitor 1 (PAI-1), tissue plasminogen activator (tPA), C-reactive protein (CRP), blood rheology, bone mineral density (BMD) of the femoral head and Harris Hip Score were measured before and after treatment.

RESULTS

After 6 months of treatment, compared with the control group, patients in the treatment group had signifificantly higher adiponectin and BMP2 levels (P<0.01 and P=0.013, respectively), lower vWF, PAI-1 and CRP levels (P=0.019, P<0.01 and P<0.01, respectively), and lower blood rheology parameters. BMD of the femoral neck, triangle area and Harris Hip Score in the treatment group were signifificantly higher than those in the control group. Moreover, plasma adiponectin showed a positive association with BMP2 (r=0.231, P=0.003) and a negative association with PAI-1 (r=-0.159, P<0.05).

CONCLUSION

MQEP may play a protective role against nontraumatic ONFH by increasing the expression of adiponectin, regulating bone metabolism and improving the hypercoagulation state, which may provide an experimental base for its clinical effects.

Decreased Insulin Sensitivity and Impaired Fibrinolytic Activity in Type 2 Diabetes Patients and Nondiabetics with Ischemic Stroke

We analyzed (a) insulin sensitivity (IS), (b) plasma insulin (PI), and (c) plasminogen activator inhibitor-1 (PAI-1) in type 2 diabetes (T2D) patients with (group A) and without (group B) atherothrombotic ischemic stroke (ATIS), nondiabetics with ATIS (group C), and healthy controls (group D). IS was determined by minimal model (Si). Si was lower in A versus B (1.18 ± 0.67 versus 2.82 ± 0.61 min-1/mU/L × 104; P < 0.001) and in C versus D (3.18 ± 0.93 versus 6.13 ± 1.69 min-1/mU/L × 104; P < 0.001). PI and PAI-1 were higher in A versus B (PI: 19.61 ± 4.08 versus 14.91 ± 1.66 mU/L; P < 0.001, PAI-1: 7.75 ± 1.04 versus 4.57 ± 0.72 mU/L; P < 0.001) and in C versus D (PI: 15.14 ± 2.20 versus 7.58 ± 2.05 mU/L; P < 0.001, PAI-1: 4.78 ± 0.98 versus 3.49 ± 1.04 mU/L; P < 0.001). Si correlated with PAI-1 in T2D patients and nondiabetics, albeit stronger in T2D. Binary logistic regression identified insulin, PAI-1, and Si as independent predictors for ATIS in T2D patients and nondiabetics. The results imply that insulin resistance and fasting hyperinsulinemia might exert their atherogenic impact through the impaired fibrinolysis.

Profibrinolytic effect of Enzamin, an extract of metabolic products from Bacillus subtilis AK and Lactobacillus

Fibrinolytic system impairment contributes to the development of thrombotic disease such as cardiovascular disease and stroke. Therefore, an agent that increases fibrinolytic activity may be useful for the prevention of these diseases. In this study, to explore novel profibrinolytic agents, we examined the profibrinolytic effect of Enzamin, an extract of metabolic products from Bacillus subtilis AK and Lactobacillus in vitro and in vivo. Enzamin directly enhanced plasmin activity generated by tissue-type plasminogen activator (t-PA) by twofold but not by urokinase-type plasminogen activator (u-PA) in vitro, which was measured employing both the chromogenic substrate H-D: -Val-Leu-Lys-pNA (S-2251) and fibrin plate. Enzamin also increased plasmin activity generated by t-PA in the cell lysate and culture medium of endothelial cells, measured by fibrin zymography. Furthermore, the oral administration of a 1% concentration of Enzamin increased plasmin activity generated by t-PA by 1.7-fold but not by u-PA in the euglobulin fraction of mouse plasma. In conclusion, Enzamin has a unique ability to enhance the fibrinolytic activity through an increase in endogenous plasmin activity generated by t-PA released from endothelial cells, and may be a beneficial supplement for the prevention of thrombotic episodes.

Haemostatic markers are associated with measures of vascular disease in adults with hypertension

Haemostatic markers have been implicated in the development and progression of vascular disease. We investigated the associations of several haemostatic markers (fibrinogen, D-dimer, FV, FVII, FVIII, von Willebrand factor (vWF) and antithrombin III) with two quantitative measures of vascular disease in adults with hypertension. Participants included 1051 African Americans (65+/-9 years, 72% women) and 894 non-Hispanic whites (61+/-9 years, 55% women) belonging to hypertensive sibships. Phenotypes of vascular disease included the ankle-brachial index (ABI), a measure of peripheral arterial disease, and urinary albumin/creatinine ratio (UACR), a surrogate of glomerular endothelial function. Generalized estimating equations were used to assess whether plasma levels of haemostatic markers were associated with measures of arteriosclerosis, after adjustment for conventional risk factors and medication (statin, aspirin and oestrogen) use. Higher fibrinogen and D-dimer were significantly associated with lower ABI in African Americans (P<0.001 and 0.004 respectively) and in non-Hispanic whites (P<0.001 and 0.010 respectively). Higher fibrinogen (P<0.001), D-dimer (P=0.003), FVIII (P<0.001) and vWF (P<0.001) were significantly associated with higher UACR in African Americans, whereas, in non-Hispanic whites, higher fibrinogen (P=0.020) and FVII (P=0.006) were significantly associated with higher UACR. Our findings indicate that in adults with essential hypertension, several markers in the haemostatic pathway are independently associated with ABI and UACR, two measures of vascular disease..

Impact of cilazapril on fibrinolytic system in hypertensive patients

Impaired fibrinolysis is associated with thromboembolic complications in hypertensive patients. Cardiovascular morbidity/mortality rates have been reported high even after lowering the elevated blood pressure with antihypertensive drugs. We investigated the effects of clinically used dosages of cilazapril on the fibrinolytic system in hypertensive patients. The present study was performed among 30 hypertensive patients (22 women, eight men), who received 2.5-5.0 mg cilazapril daily for 1 month. Before and after the cilazapril treatment, patients' venous blood was drawn for fibrinolytic tests. The fibrinolytic activity was examined utilizing the euglobulin clot lysis time and fibrin plate methods. Using the fibrin plate method, as compared with the pretreatment group, we observed a 57% increased activity in the hypertensive patients receiving cilazapril (P < 0.001). When assessed by the euglobulin clot lysis time method, the activity due to cilazapril treatment was found to be relatively low, although highly significant (approximately 20%, P < 0.001). Changes in fibrinolytic activity were observed in 23 (77%) hypertensive patients after cilazapril treatment; however, their blood pressure remained normal. The remaining seven patients' (23%) blood pressures and fibrinolytic activity did not change significantly after cilazapril treatment. In conclusion, we suggest that the observed differential fibrinolytic activity between the pre and post cilazapril treatment values is due to the plasminogen activators released from the vascular endothelium, which may have been stimulated by cilazapril. It appears that cilazapril is not only an angiotensin-converting enzyme inhibitor but also a stimulator for fibrinolytic activity, which may be an added component in reducing thromboembolic complications in hypertensive patients.

The role of the alpha-1 adrenoceptor in modulating human mesangial cell matrix production

BACKGROUND

The sympathetic nervous system is frequently activated in hypertension and may modify various aspects of renal function. Whether modulation of the sympathetic nervous system directly influences the development of renal fibrosis is yet to be established. The current study investigates the role of the alpha-1 adrenoceptor on human mesangial cell scarring.

METHODS

Human mesangial cells were injured with macrophage-conditioned medium (MPCM) and treated with doxazosin for 1 or 3 days.

RESULTS

alpha-1 Adrenoceptor antagonist doxazosin of 2 micromol/l reduced fibronectin protein in MPCM-injured female mesangial cells by 31 +/- 1.03% (P < 0.001) and by 9.5 +/- 0.3% (P = 0.01) in male mesangial cells. The differential response between sexes was significant (P = 0.004). alpha-1B Adrenoceptors were detected in human mesangial cells by reverse transcription-polymerase chain reaction with expression in female cells being 87% higher than in males (P = 0.04). Injury with MPCM reduced alpha-1B adrenoceptor mRNA expression in both cell types. Doxazosin had no effect on the protein levels of transforming growth factor-beta (TGF-beta) or interleukin-1beta (IL-1beta), however, a small reduction in tumour necrosis factor-alpha (TNF-alpha) levels was observed. Doxazosin had no effect on the modulators of matrix turnover matrix metalloproteinases MMP3, MMP9 and tissue inhibitor of matrix metalloproteinases (TIMP-1), although a significant reduction in tissue plasminogen activator (tPA); (36.5 +/- 2.6%, P < 0.001) was observed. Doxazosin caused an up-regulation of kallikrein expression, both at mRNA and protein levels. Co-treatment with the bradykinin B2 receptor antagonist HOE140 was able to attenuate the effects of doxazosin treatment on fibronectin levels.

CONCLUSION

These data suggest that inhibition of alpha-1B adrenoceptors in mesangial cells exerts an anti-fibrotic effect in a sex-specific manner via modulation of the kallikrein-kinin/plasminogen activator system.

Is the effect of antihypertensive drugs on platelet aggregability and fibrinolysis clinically relevant?

Hypertension is associated with decreased fibrinolytic potential, mainly expressed as elevated plasma plasminogen activator inhibitor type 1 (PAI-1) levels, and increased platelet aggregability, which may account in part for the increased risk of atherosclerosis and its clinical complications in hypertensive patients. The effects of antihypertensive drugs on this prothrombotic state have been investigated and controversial findings have been reported, possibly because of differences in study designs, patients selected, and methodology used. Scarce and conflicting data exist about the effects of diuretics and beta-adrenoceptor antagonists on the fibrinolytic system, whereas ACE inhibitors have generally been reported to improve the fibrinolytic balance by decreasing plasma PAI-1 levels, calcium channel antagonists have been shown to increase tissue plasminogen activator (tPA) activity, and angiotensin II type 1 (AT(1)) receptor antagonists seem to exert neutral effects. beta-Adrenoceptor antagonists, calcium channel antagonists, and AT(1)-receptor antagonists have been reported to exert anti-aggregatory effects on platelets, while contrasting data exist about the influence of ACE inhibitors. Clinical implications of the changes induced by antihypertensive drugs on the fibrinolytic balance and platelet function are still debated. In particular, the question of whether these changes may translate into different degrees of cardiovascular protection in hypertensive patients remains unanswered. While awaiting more information from clinical trials, the choice of antihypertensive drugs, particularly in high-risk patients, should take into account effects beyond their BP-lowering efficacy. Selected agents should have a favorable, or at least neutral, impact on fibrinolytic function and platelet activity.

Exercise-induced changes in coagulation and fibrinolysis in healthy populations and patients with cardiovascular disease

This review highlights the clinical significance of coagulation and fibrinolytic responses, and adaptations in healthy individuals and patients with cardiovascular disease (CVD). Much of the review focuses on indicators of the potential for coagulation and fibrinolysis. The terms 'coagulation potential' and 'fibrinolytic potential' are used frequently, as much of the literature in the area of exercise haemostasis evaluates factors that reflect an increased potential for coagulation, while coagulation per se, may or may not be occurring. Similarly, fibrinolysis is definitively the lysis of inappropriate or excessive blood clot, which may or may not be occurring when the enzymes that stimulate fibrinolysis are activated. Nevertheless, markers of coagulation and fibrinolytic potential are associated with CVD, ischaemic events, and cardiovascular mortality. Additionally, fibrinolytic potential is associated with other established CVD risk factors. Ischaemic events triggered by physical exertion are more likely to occur due to an occlusive thrombus, suggesting the exercise-induced responses related to haemostasis are of clinical significance. The magnitude of increase in coagulation potential, platelet aggregation and fibrinolysis appears to be primarily determined by exercise intensity. Patients with CVD may also have a larger increase in coagulation potential during acute exercise than healthy individuals. Additionally, the magnitude of the fibrinolytic response is largely related to the resting fibrinolytic profile of the individual. In particular, high resting plasminogen activator inhibitor-1 may diminish the magnitude of tissue plasminogen activator response during acute exercise. Therefore, acute responses to exercise may increase the risk of ischaemic event. However, chronic aerobic exercise training may decrease coagulation potential and increase fibrinolytic potential in both healthy individuals and CVD patients. Due to the aforementioned importance of resting fibrinolysis on the fibrinolytic response to exercise, chronic aerobic exercise training may cause favourable adaptations that could contribute to decreased risk for ischaemic event, both at rest and during physical exertion.

Exercise and Training Effects on Blood Haemostasis in Health and Disease

In recent years, the dysfunction of the haemostatic system in relation to the clinical complications from arterioscleroses and cardiovascular diseases has become more recognised. Blood coagulation and fibrinolysis comprise two important physiological systems, which are regulated by a balance between activators and inhibitors. Activation of blood coagulation is associated with accelerated clot formation, whereas activation of blood fibrinolysis enhances the breakdown of the blood clot. Available evidence suggests that strenuous exercise induces activation of blood coagulation with simultaneous enhancement of blood fibrinolysis. Although the responses of blood coagulation and fibrinolysis appear to be related to the exercise intensity and its duration, recent reports suggest that moderate exercise intensity is followed by activation of blood fibrinolysis without concomitant hyper-coagulability, while very intense exercise is associated with concurrent activation of blood coagulation and fibrinolysis. Similar to blood coagulation and fibrinolysis, systemic platelet-related thrombogenic factors have been shown to be involved in the initiation and progression of atherogenesis and plaque growth. Although exercise effects on platelet aggregation and function in healthy individuals have been examined, the results reported have been conflicting. However, for patients with coronary heart disease, the balance of evidence available would strongly suggest that platelet aggregation and functions are increased with exercise. Few studies are available concerning the influence of training on blood coagulation and fibrinolysis and the exact effects of exercise training on the equilibrium between blood coagulation and fibrinolysis is not as yet known. Although the effects of physical training on platelets have been briefly investigated, available meagre evidence suggests that exercise training is associated with favourable effects on platelet aggregation and activation in both men and women.

Fibrinolytic function and atrial fibrillation

Atrial fibrillation (AF) is the commonest sustained cardiac arrhythmia, which is associated with a substantial risk of stroke and thromboembolism. A prothrombotic or hypercoagulable state has been observed in these patients, although previous studies have mainly focused on various clotting factors, endothelial damage or dysfunction markers and platelet activation. However, fibrinolytic function has been less frequently studied, despite the fibrinolytic system playing an important role in preventing intravascular thrombosis. Indeed, increasing evidence suggests that an imbalance between the fibrinolytic function is of great importance in cardiovascular disease. This review will begin by providing a brief approach to fibrinolytic function and examine previous studies about fibrinolytic activity and atrial fibrillation.

Parental history of hypertension is associated with coagulation–fibrinolytic balance disorders

It has been previously shown that essential hypertension (EH) is associated with coagulation-fibrinolytic balance disorders. Our study was conducted in order to investigate disturbances in coagulation-fibrinolysis in offsprings of hypertensive parents. Two groups were studied: 44 healthy normotensive individuals (17 male, 27 female, age range 12-22 years) with a documented family history of hypertension and 33 individuals (14 male, 19 female, age range 11-21 years) without a family history of essential hypertension. The following parameters were determined in both groups: plasminogen activator inhibitor-1 antigen, tissue plasminogen activator antigen, fibrinogen, fibrin degradation products, thrombomodulin, protein S antigen, protein C activity, von Willebrand factor Ag, factor VII and factor XII activity. Additionally, systolic and diastolic blood pressure, insulin levels, blood lipids and heart rate were determined. The two groups were not found to have differences with respect to age, gender, body mass index, blood lipids and insulin levels. Hypertensive offsprings had significantly higher plasma levels of plasminogen activator inhibitor-1 antigen, fibrinogen, fibrin degradation products, protein S antigen and factor XII activity, while no differences were observed to the other haemostatic variables studied. Hence, offsprings of hypertensives had significantly higher diastolic blood pressure and heart rate. In conclusion, alterations regarding blood pressure, heart rate and fibrinolytic function exist in offsprings of hypertensive parents compared to individuals without family history of hypertension.

Endogenous fibrinolysis in patients with lower extremity ischemia

To explore the relationship between disorders of endogenous fibrinolysis and thrombosis in patients with lower extremity ischemia, we measured the activity of tissue plasminogen activator (tPAac) and plasminogen activator inhibitor (PAlac) and the antigens of tissue plasminogen activator (tPAa) and inhibitor (PAla) in plasma from 420 patients treated for lower extremity ischemia. Values and ratios observed were compared with those in healthy volunteers. Additionally, values and ratios in the patients were examined with respect to the severity of ischemia and site of atherosclerotic occlusion or stenosis (pelvic compared with femoropopliteal or crural). Patients with lower extremity ischemia had higher plasma concentrations of PAla (p<0.01) and PAlac (p<0.0001) than healthy volunteers. In patients with rest pain or gangrene, the ratio of tPAac to PAlac was higher than in patients with claudication (p<0.05). The elevation of tPAac in patients with the more severe form of lower extremity ischemia is probably the feedback protective reaction on prothrombotic mechanisms of the organism suffered from severe atherosclerosis. Results did not vary according to the site of occlusion or stenosis. Our study found defects in endogenous fibrinolysis in patients with lower extremity ischemia. A defect in fibrinolysis may contribute to the development of thrombosis in native arteries and bypasses.

Blood hemostasis in exercise and training

Formation of the blood clot is a slow but normal physiological process occurring as a result of the activation of blood coagulation pathways. Nature's guard against unwanted blood clots is the fibrinolytic enzyme system. In healthy people, there is a delicate dynamic balance between blood clot formation and blood clot dissolution. Available evidence suggests that exercise and physical training evoke multiple effects on blood hemostasis in normal healthy subjects and in patients. A single bout of exercise is usually associated with a transient increase in blood coagulation as evidenced by a shortening of activated partial thromboplastin time (APTT) and increased Factor VIII (FVIII). The rise in FVIII is intensity dependent and continues into recovery. The effects of acute exercise on plasma fibrinogen have yielded conflicting results. Thus, the issue of whether exercise-induced blood hypercoagulability in vitro mirrors an in vivo thrombin generation and fibrin formation remains disputable. Exercise-induced enhancement of fibrinolysis has been repeatedly demonstrated using a wide range of exercise protocols incorporating various exercise intensities and durations. Moderate exercise appears to enhance blood fibrinolytic activity without a concomitant activation of blood coagulation mechanisms, whereas, very heavy exercise induces simultaneous activation of blood fibrinolysis and coagulation. The increase in fibrinolysis is due to a rise in tissue-type plasminogen activator (tPA) and decrease in plasminogen activator inhibitor (PAI). The mechanism of exercise-induced hyperfibrinolysis is poorly understood, and the physiological utility of such activation remains unresolved. Strenuous exercise elicits a transient increase in platelet count, but there are conflicting results concerning the effect of exercise on platelet aggregation and activation. Few comprehensive studies exist concerning the influence of exercise training on blood hemostasis, making future investigation necessary to identify whether there are favorable effects of exercise training on blood coagulation, fibrinolysis, and platelet functions.

Association of blood pressure with fibrinolytic potential in the Framingham offspring population

BACKGROUND

Hypertension is an established risk factor for acute coronary events. Because fibrinolytic and hemostatic factors are also associated with cardiovascular disease, we examined the relations of systolic and diastolic blood pressures (SBP and DBP) to levels of plasminogen activator inhibitor antigen, tissue plasminogen activator antigen, fibrinogen, factor VII, von Willebrand factor, fibrinogen, and plasma viscosity in subjects of the Framingham Offspring Study.

METHODS AND RESULTS

We studied 1193 men and 1459 women after the exclusion of subjects with known cardiovascular disease and those receiving anticoagulant or antihypertensive therapy. Linear regression models were used to evaluate SBP and DBP as predictors of fibrinolytic and hemostatic factor levels in separate sex models, with adjustment for age, body mass index, smoking, diabetes, total cholesterol, HDL, triglycerides, alcohol intake, and estrogen use (in women). In both sexes, levels of plasminogen activator inhibitor and tissue plasminogen activator antigen were positively related to SBP and DBP (P<0.001). Plasma viscosity was positively related to SBP (P=0.008) and DBP (P=0.001) in women only. There was no association between SBP or DBP and fibrinogen, factor VII, or von Willebrand factor in either sex.

CONCLUSIONS

These data suggest that impaired fibrinolysis may play an important role in the pathogenesis of cardiovascular disease in hypertensive patients.

Differential effects of enalapril and nitrendipine on the fibrinolytic system in essential hypertension

BACKGROUND

Impaired fibrinolysis is associated with thromboembolic complications in hypertensive patients. It has been reported that cardiovascular morbidity and mortality rates are high even after lowering the elevated blood pressure with antihypertensive drugs. The aim of this study was to assess the effect of clinically used dosages of enalapril and nitrendipine on the fibrinolytic system.

METHODS

Tissue plasminogen activator antigen (tPA) and tissue plasminogen activator inhibitor-1 (PAI-1) activity were measured in 20 normotensive male subjects and 46 male patients with mild essential hypertension divided into 2 groups (22 patients treated with 5 to 10 mg enalapril once a day and 24 treated with 5 to 10 mg nitrendipine once a day) before and 3 months after drug administration. Plasma renin activity and norepinephrine concentration were also measured.

RESULTS

There were no significant differences in basal characteristics between the 2 hypertensive groups. In both hypertensive groups, blood pressure was significantly reduced to a similar level after drug treatment. In the 2 hypertensive groups, plasma renin activity significantly increased after drug treatment; however, there were no significant changes in norepinephrine concentration. Before drug treatment, the 2 hypertensive groups had significantly higher tPA and higher PAI-1 activity than the normotensive subjects. In the enalapril group, there was no significant change in tPA although PAI-1 activity significantly decreased after drug treatment. In the nitrendipine group, there was no significant change in tPA although PAI-1 activity significantly increased after drug treatment.

CONCLUSION

Thus enalapril improved impaired fibrinolysis but nitrendipine further aggravated fibrinolysis in essential hypertension. Considering the effect of antihypertensive drugs on the fibrinolytic system, more effective and beneficial treatment of hypertensives, especially at a high risk for thrombus formation might be selected.

3-Hydroxy-3-methylglutaryl coenzyme A reductase inhibitors increase fibrinolytic activity in rat aortic endothelial cells. Role of geranylgeranylation and Rho proteins

3-Hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase inhibitors (HRIs) have been recently shown to prevent atherosclerosis progression. Clinical benefit results from combined actions on various components of the atherosclerotic lesion. This study was designed to identify the effects of HRI on one of these components, the endothelial fibrinolytic system. Aortas isolated from rats treated for 2 days with lovastatin (4 mg/kg body wt per day) showed a 3-fold increase in tissue plasminogen activator (tPA) activity. In a rat aortic endothelial cell line (SVARECs) and in human nontransformed endothelial cells (HUVECs), HRI induced an increase in tPA activity and antigen in a time- and concentration-dependent manner. In SVARECs, the maximal response was observed when cells were incubated for 48 hours with 50 micromol/L HRI. An increase of tPA mRNA was also in evidence. In contrast, HRI inhibited plasminogen activator inhibitor-1 activity and mRNA. The effects of HRI were reversed by mevalonate and geranylgeranyl pyrophosphate, but not by LDL cholesterol and farnesyl pyrophosphate, and were not induced by alpha-hydroxyfarnesyl phosphonic acid, an inhibitor of protein farnesyl transferase. C3 exoenzyme, an inhibitor of the geranylgeranylated-activated Rho protein, reproduced the effect of lovastatin on tPA and plasminogen activator inhibitor-1 activity and blocked its reversal by geranylgeranyl pyrophosphate. The effect of HRI was associated with a disruption of cellular actin filaments without modification of microtubules. A disrupter of actin filaments, cytochalasin D, induced the same effect as lovastatin on tPA, whereas a disrupter of microtubules, nocodazole, did not. In conclusion, HRI can modify the fibrinolytic potential of endothelial cells, likely via inhibition of geranylgeranylated Rho protein and disruption of the actin filaments. The resulting increase of fibrinolytic activity of endothelial cells may contribute to the beneficial effects of HRI in the progression of atherosclerosis.

Hemostasis in normotensive and hypertensive men: results of the PROCAM study. The prospective cardiovascular Münster study

BACKGROUND

The greater than normal cardiovascular risk of hypertensive patients could be partly due to an impairment of hemostatic balance found in such individuals.

OBJECTIVE

To examine the relationship between hemostatic variables and blood pressures in 1950 apparently healthy male participants in the prospective cardiovascular Münster study aged 40-65 years.

METHODS

Blood pressure and other variables were determined, including fibrinogen level, coagulation factor VII clotting activity, protein C level, antithrombin III level, plasminogen activator inhibitor-1 level, euglobulin fibrinolytic activity, and von Willebrand factor level.

RESULTS

Age-adjusted mean values of coagulation factor VII clotting activity, plasminogen activator inhibitor-1 level, antithrombin III level, and protein C level in hypertensives and borderline hypertensives were significantly higher than those in normotensive men (e.g. for hypertensive versus normotensive men, coagulation factor VII clotting factor activity 111.5 versus 106.1%, plasminogen activator inhibitor-1 level 5.05 versus 3.22 arbitrary units/ml, and protein C level 111.1 versus 107.0%, P < 0.05-0.01). For most of the hemostatic variables we found positive bivariate correlations to blood pressure (P < or = 0.05). Exceptions were von Willebrand factor level (no correlation to blood pressure), and euglobulin fibrinolytic activity (a negative correlation to systolic blood pressure and no correlation to diastolic blood pressure). Significance persisted in the multiple logistic regression analysis with the exception of the relationships between systolic and diastolic blood pressures and fibrinogen level as well as euglobin fibrinolytic activity after adjustment for age. After adjustment for age and body mass index significance for relationships between systolic blood pressure and coagulation factor VII clotting activity as well as protein C level was also lost.

CONCLUSIONS

We conclude that the greater than normal cardiovascular risk of hypertensive patients is partly due to an imbalance in hemostasis.

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.

Dependence of augmentation of arterial endothelial cell expression of plasminogen activator inhibitor type 1 by insulin on soluble factors released from vascular smooth muscle cells

BACKGROUND

Insulin-resistant states are characterized by accelerated atherosclerosis and are associated with increased plasma concentrations of insulin and plasminogen activator inhibitor type 1 (PAI-1). To determine whether arterial expression of PAI-1 in response to insulin contributes to the increased PAI-1 observed, human and porcine arteries in culture were exposed to insulin, and results were compared with responses of specific arterial cellular constituents maintained in culture and coculture.

METHODS AND RESULTS

Human and porcine arterial segments and cells obtained from arteries were maintained in culture. Insulin increased accumulation of PAI-1 in conditioned medium from arterial segments (ng PAI-1 [1 nmol/L insulin minus control]: human arteries 47+/-17, porcine arteries 3.1+/-1.2, P<.05 for each) and from endothelial cells (ECs) cocultured with smooth muscle cells (SMCs, ng PAI-1 [1 nmol/L insulin minus control]: human cells 43+/-8, porcine cells 0.5+/-0.1, P<.05 for each). Insulin had no effect on EC expression of PAI-1 when not cocultured with SMCs. Increased accumulation of PAI-1 was seen when ECs, in coculture chambers without SMCs, were cultured with medium previously conditioned by SMCs in the presence of insulin. The increased accumulation of PAI-1 in conditioned medium was secondary to both an increased transport of PAI-1 from the basal to the apical surface of ECs as well as an increased production of PAI-1 by ECs.

CONCLUSIONS

Insulin augments arterial expression of PAI-1 by stimulating release of a soluble factor(s) from SMCs. Accordingly, increased arterial elaboration of PAI-1 in response to insulin is likely to account, in part, for the elevated PAI-1 observed in the blood of subjects with insulin-resistant states.

Haemostasis balance disorders in patients with essential hypertension

This study was aimed at investigating haemostasis parameters in patients (pts) with arterial hypertension (AH) before any medical treatment and to correlate these findings with those in healthy normal Greek population 83 pts (48 m, 35 w) mean age 49.8 +/- 10.1 yrs, body mass index 23.4 +/- 1.5 with mild to moderate AH and 42 healthy volunteers matched for sex (24 m, 18 w), age 51.2 +/- 10.5 yrs and body mass index 22.8 +/- 1.46 were studied. Fibrinogen, vWF, plasminogen, ECLT, a2 antiplasmin, tPA-Ag, PAI-1 in all pts and in the control group were measured. Mean age and BMI did not significantly differ between the two groups. The hypertensive patients had significantly higher levels of fibrinogen (327.75 +/- 51.36 vs. 272.84 +/- 46.8 mg/dl), tPA-Ag (8.81 +/- 3.32 vs. 5.76 +/- 2.54 ng/ml) and PAI-1 (11.8 +/- 10.9 vs. 7.91 +/- 5.5 IU/ml), whereas a2 antiplasmin level was significantly lower (98.71 +/- 15.40 vs. 107.84 +/- 17.52%). No differences were found between hypertensives and normal subjects in vWF, plasminogen and ECLT. These preliminary data suggest that in pts with mild to moderate AH, before any medical treatment, there are significantly higher levels of fibrinogen, tPA-Ag and PAI-1 compared with normal volunteers, whereas there are significantly lower a antiplasmin levels. These findings indicate a disturbance in the haemostasis balance with hypercoagulability and fibrinolytic deficiency.

Fibrinolytic responses to acute physical activity in older hypertensive men

We tested the hypothesis that the fibrinolytic response to acute physical activity is impaired in sedentary older hypertensive men, which may contribute to the risk of exertion-triggered acute myocardial infarction in this population. Tissue-type plasminogen activator (t-PA) antigen and activity and plasminogen activator inhibitor-1 (PAI-1) antigen and activity were measured in 12 hypertensive (69 +/- 1 yr) and 11 normotensive (64 +/- 1 yr) men before and after an acute bout of submaximal exercise. Contrary to our hypothesis, there were no differences between the two groups in the fibrinolytic response to exercise. t-PA antigen and activity were significantly elevated in both the hypertensive (38 and 172%, respectively) and normotensive (45 and 130%, respectively) groups immediately after exercise but they returned to resting levels within 30 min. There was no change in PAI-1 antigen levels immediately after exercise in either group; however, PAI-1 antigen was significantly lower at 30 and 60 min postexercise in both the hypertensive (31 and 16%, respectively) and normotensive (35 and 20%, respectively) groups. PAI-1 activity was significantly lower immediately after exercise in both the hypertensive (25%) and normotensive (22%) groups and remained lower than preexercise levels at 30 min (23 and 26%, respectively) and 60 min (16 and 12%, respectively) postexercise in both groups. The results of this study demonstrate that the fibrinolytic response to an acute bout of moderate physical activity is not impaired in sedentary older hypertensive men.

Determinants of coronary vascular disease in patients with type II diabetes mellitus and their therapeutic implications

Cardiovascular morbidity and mortality are increased 4- to 6-fold in patients with type II diabetes. The high prevalence is multifactorial and reflects in part the adverse influence of covariate, cardiac risk factors such as hypertension and hyperlipidemia. Type II diabetes is characterized by insulin resistance, hyperinsulinemia, and altered carbohydrate and lipid metabolism resulting in hyperglycemia, increased concentrations in blood of very low-density and low-density lipoproteins, and decreased blood high-density lipoproteins. Abnormalities seen predispose to vasculopathy through lipid deposition into vessel walls associated with monocyte infiltration, vascular smooth muscle cell proliferation, arterial mural fibrosis, and thrombosis. Conventional therapy for cardiovascular disease such as angioplasty and bypass surgery are of only limited efficacy. Thus, retardation of progression of atherosclerosis is essential. In addition to focusing on co-existent cardiac risk factors such as hypertension, therapy for patients with type II diabetes should reduce or reverse insulin resistance, improve metabolic control, and, ideally, do so without exacerbating hyperinsulinemia. Diet and exercise are central, and novel orally active hyperglycemic agents such as the biguanides and the thiazolidinediones that sensitize diverse tissues to insulin offer particular promise.

Increased levels of tissue plasminogen activator antigen in essential hypertension. A population-based study in Sweden

OBJECTIVE

To investigate components of the haemostatic and fibrinolytic system in borderline hypertensives and hypertensives, drug-treated or not, from a defined population.

DESIGN AND METHODS

A randomly selected sample of the population of northern Sweden, 1558 subjects aged 25-64 years, was studied. Eight per cent of them were being treated with antihypertensive drugs (trHT). Remaining subjects were classified according to their mean diastolic blood pressure (DBP). Normotension, DBP < 85 mmHg, was found in 63%, borderline hypertension (bHT), DBP 85-94 mmHg, in 21% and untreated hypertension (uHT), DBP > or = 95 mmHg, in 8% of the subjects.

RESULTS

Mean age increased from the normotensive group through the bHT and uHT groups to the trHT group, members of which were the oldest. Age-adjusted values for the body mass index, waist: hip ratio, serum triglyceride and Phadeseph plasma insulin levels increased with each level of hypertension. Plasma fibrinogen levels and plasminogen activator inhibitor type 1 activity (in men) increased stepwise from normotensives through bHT and uHT to the highest values found in the trHT group. The tissue plasminogen activator (tPA) activity in men declined strongly across the groups, trHT having the lowest fibrinolytic activity (P < 0.001). tPA antigen levels increased strongly from normotensives through bHT to uHT, but then were lower in the trHT group. Even after adjustment for possible confounders, men in the uHT group had 21% higher (P = 0.027) tPA antigen levels than did the normotensives. In bHT men, the tPA antigen and plasminogen activator inhibitor type 1 activities were 14 and 24% respectively, higher (P < 0.01) than those in the normotensives.

CONCLUSION

Hypertension is associated with multiple metabolic and fibrinolytic disturbances that are accentuated in drug-treated hypertensives and already discernible in subjects with borderline hypertension. Decreased fibrinolysis is associated with, and possibly secondary to, metabolic disturbances linked to the insulin-resistance syndrome. The independent increase in tPA antigen in hypertensive men might indicate an endothelial dysfunction.

Elevation of plasminogen activator inhibitor 1 in borderline hypertension is linked to concomitant metabolic disturbances

In the present study we investigated plasma levels of plasminogen activator inhibitor 1 (PAI-1), fibrinogen and von Willebrand factor (vWF) in borderline hypertensive (BHT) men [diastolic blood pressure (DBP) 85-94 mmHg, n = 75] and age-matched normotensive (NT) control subjects (DBP < or = 80 mmHg, n = 75), in relation to smoking, body mass index (BMI) and fasting lipoprotein and insulin levels. PAI-1 levels were elevated in the BHT group [16.3 vs. 13.7 arbitrary units (AU), P = 0.032], whereas levels of fibrinogen and vWF were similar in the two groups. The PAI-1 elevation was even more pronounced in dyslipidaemic BHT subjects than in normolipidaemic NT subjects (20.0 vs. 10.3 arbitrary units (AU), P = 0.001). PAI-1 levels showed strong correlations with insulin, lipoproteins and BMI (P < 0.01-0.001), but not with DBP. The results show that disturbances in the fibrinolytic system appear even in borderline hypertension. The elevation of PAI-1 levels seems to be more strongly linked to concomitant metabolic disturbances than to blood pressure levels.

The fibrinolytic system is not impaired in older men with hypertension

The fibrinolytic system is thought to be impaired in older hypertensive adults, thus contributing to the elevated risk of atherothrombosis, stroke, and acute myocardial infarction in this population. However, studies that have examined the fibrinolytic system in hypertensive individuals have failed to control for the confounding effects of other metabolic risk factors, making it difficult for one to determine the independent effect of hypertension on the fibrinolytic system. The purpose of the present study was to test the hypothesis that the fibrinolytic system is not impaired in older sedentary hypertensive men when the confounding effects of cardiovascular disease, diabetes, and dyslipidemia are controlled. Plasma concentrations of tissue-type plasminogen activator antigen and activity as well as plasminogen activator inhibitor-1 antigen and activity were measured under resting conditions in 12 hypertensive (69.4 +/- 1.4 years) and 11 normotensive 65.2 +/- 1.3 years) older men. The hypertensive and normotensive subjects had similar anthropometric and metabolic characteristics. There were no significant differences between the hypertensive and normotensive men in tissue-type plasminogen antigen (7.3 +/- 0.5 versus 6.1 +/- 0.6 ng/mL) and activity (1.8 +/- 0.3 versus 1.7 +/- 0.2 IU/mL) or plasminogen activator inhibitor-1 antigen (14.1 +/- 2.3 versus 10.8 +/- 2.2 ng/mL) and activity (17.4 +/- 1.2 versus 17.5 +/- 1.8 arbitrary units [AU]/mL) levels. In addition, the molar concentration ratio of active tissue type plasminogen activator to active plasminogen activator inhibitor-1 did not differ between the hypertensive (1:9.7 +/- 2.3) mmol/L) and normotensive (1:10.5 +/- 2.2 mmol/L) subjects, indicative of no impairment in fibrinolytic potential in either group. These results support the hypothesis that hypertension does not directly result in impaired fibrinolytic function in older adults. Furthermore, our findings suggest that abnormalities in fibrinolytic function in older hypertensive men are likely due to the primary effects of other metabolic disorders that usually accompany hypertension, such as hyperinsulinemia and dyslipidemia.

Enhanced levels of tissue-type plasminogen activator in borderline hypertension

Despite effective antihypertensive therapy, essential hypertension is still associated with considerable residual risk of cardiovascular complications. The aim of the present study was to investigate the state of the endogenous fibrinolytic system in young subjects with borderline hypertension. Thirty-nine young (age, 24 to 34 years) male subjects with borderline hypertension (systolic BP [SBP] 140 to 160 mm Hg and/or diastolic BP [DBP] 85 to 95 mm Hg) and 17 normotensive control subjects (age, 22 to 31 years; SBP 110 to 130 and DBP 60 to 80 mm Hg) were recruited from a population screening. Plasma levels of tissue-type plasminogen activator (t-PA) antigen and activity and plasminogen activator inhibitor 1 (PAI-1) antigen were determined at rest and in response to a venous occlusion test. Borderline-hypertensive subjects had metabolic and anthropometric characteristics similar to normotensive individuals. In comparison with normotensive subjects, borderline-hypertensive subjects had higher plasma concentration of t-PA antigen both at rest and after venous occlusion but similar levels of t-PA activity or PAI-1 antigen. The increase in t-PA antigen and activity in response to venous occlusion was significantly greater in borderline-hypertensive subjects than in normotensive control subjects (P < .0001 and P = .003, respectively). In stepwise regression analyses, 24-hour mean arterial pressure emerged as the single most powerful predictor of t-PA antigen levels, but body mass index was the most important determinant of t-PA activity and PAI-1 antigen. However, PAI-1 was explained by both body mass index (partial r = .48, P < .001) and 24-hour mean arterial pressure (partial r = .29, P < .05). Thus, early hypertension may be associated with significant alterations in endogenous fibrinolysis.

Some coronary risk factors related to the insulin resistance syndrome and treatment with gemfibrozil. Experience from the Helsinki Heart Study

BACKGROUND

Coronary risk factors related to the insulin resistance syndrome tend to cluster in the same individual. Our previous studies have shown that the dyslipidemia characteristic of this syndrome--low HDL cholesterol and high triglyceride (TG) levels--responds well to treatment with gemfibrozil. Most factors related to insulin-resistance syndrome decrease fibrinolytic capacity, whereas a recent study showed that gemfibrozil improves it and thus may attenuate thrombotic events. To discover whether subjects with clustering of factors related to this resistance might in particular benefit from gemfibrozil, we reanalyzed the Helsinki Heart Study data.

METHODS AND RESULTS

We used Cox regression models to explore the effects of gemfibrozil among overweight subjects with additional coronary risk factors in this hypercholesterolemic male population of 2046 subjects randomized to gemfibrozil and 2035 to placebo. The effect of gemfibrozil was largely confined to overweight subjects: among those with body mass index (BMI) > 26 kg/m2, the net difference in cardiac end points between gemfibrozil and placebo groups was 21 (25 of 1119 versus 46 of 1081), and in those with BMI < or = 26 kg/m2, it was 7 (31 of 927 versus 38 of 954). The risk reduction with gemfibrozil was 78% (P = .002) among those with BMI > 26 kg/m2 and dyslipidemia (TG > or = 2.3 mmol/L and HDL cholesterol < 1.08 mmol/L). Among those with BMI > 26 kg/m2 and three or four of the following factors present--smoking, sedentary lifestyle, blood pressure > or = 140/90 mm Hg, or blood glucose > 4.4 mmol/L--the risk reduction was 68% (P = .03).

CONCLUSIONS

Gemfibrozil reduced the coronary risk mainly in overweight subjects with additional risk factors known to contribute to the insulin-resistance syndrome or predispose to it.

Hyperlipidemia: a novel etiologic factor in deep vein thrombosis

The possible association of hyperlipidemia and deep vein thrombosis (DVT) was investigated in 59 consecutive patients. The incidence of hyperlipidemia, judged by the value of serum total cholesterol and triglyceride, was unexpectedly high (overall 59%, high total cholesterol alone 25%, high triglyceride alone 9%, combined 25%), as compared with 29% of the control (p < 0.001). The idiopathic DVT patients (without known etiologic factors) had a higher incidence of hypercholesterolemia (63%) than the normal subjects (20%, p = 0.0002). The idiopathic DVT patients showed higher total cholesterol level of 255 +/- 72 mg/dl than that of 194 +/- 36 in the control subjects (p < 0.0001). And 67% of the idiopathic DVT patients were hyperlipidemic. Thereby, hyperlipidemia may be an important etiologic factor in DVT, which has not been recognized previously. The low incidence of DVT in Asians may, thus, be attributable to their lower cholesterol level.

The association of fibrinolysis and hyperlipidaemia with quantitative sensory tests in an epidemiological study of Swedish type 1 diabetic patients

Serum levels of cholesterol, HDL-cholesterol, triglycerides, lipoprotein Lp(a), and the fibrinolysis factors tPA (tissue plasminogen activator) and PAI-1 activity (plasminogen activator inhibitor) were compared with sensory thresholds for vibration, electrical current perception, and pain in a population-based study comprising 239 patients with diabetes mellitus Type 1, aged 15-50 years. Univariate regression analyses (n = 180) showed significant correlations between elevated sensory thresholds and age, duration of diabetes, serum cholesterol and triglycerides, and HbA1c. In multivariate regression analysis, age, duration of diabetes, height, and serum triglycerides showed significant independent associations with five or six of the six measured sensory threshold variables. In addition there was a significant association between increased thresholds for vibration and Lp(a) levels. Thus, increased sensory thresholds for vibration, current perception, and pain in patients with Type 1 diabetes are associated with increased serum triglyceride levels, and Lp(a) levels are associated with increased threshold for vibration. Fibrinolytic activity is unrelated to these measures of nerve function in Type 1 diabetic patients.

Platelet function and fibrinolytic activity during rest and exercise in borderline hypertensive patients

In this study we examined whether the reduced fibrinolysis and increased platelet activity that are known to occur in hypertension are already present in borderline hypertension. Twelve patients with 'borderline' hypertension (diastolic blood pressure 90-95 mmHg) were found to have substantially reduced fibrinolytic activity, both at rest and during exercise, compared with 12 normotensive controls. Euglobulin clot lysis time (ECLT) was significantly higher in hypertensive subjects (218 min vs. 145 min; P < 0.05), and this difference persisted during exercise. Resting tissue plasminogen activator activity (t-PA) did not differ in the two groups, but the brisk increase in t-PA in controls during exercise (0.64 rising to 1.44 IU mL-1; P < 0.01) did not occur to the same extent in the borderline hypertensive subjects. Levels of the fast-acting t-PA inhibitor, normally referred to as PAI-1, were considerably higher in hypertensives (9.22 vs. 4.41 IU mL-1; P < 0.02), and this difference persisted in the upright posture, indicating a decrease in fibrinolytic activity. Platelet aggregability induced by ADP in vitro was not significantly higher in the hypertensive subjects, but indices of platelet activity in vivo (B-TG and PF-4 levels) revealed enhanced platelet function in the hypertensives. These results indicate that the indicators of altered haemostatic function known to occur in hypertension, namely diminished fibrinolytic activity and increased platelet function, are already detectable during the very earliest stage of the disease.

Expression of PAI-1, t-PA and u-PA in cultured human umbilical vein endothelial cells derived from racial groups

To determine whether inherent fibrinolytic differences may exist in racial groups (black americans, BA vs. white americans, WA), 55 different individual racially-derived human umbilical vein endothelial cell (HUVEC) cultures (35 BA and 20 WA) were analyzed in terms of their fibrinolytic protein (t-PA, u-PA and PAI-1) antigen and mRNA levels. Values (mean +/- SD) for measured fibrinolytic component levels include: cell-associated t-PA antigen (ELISA), 1.14 +/- 0.82 ng/ml/8.6 x 10(5) cells/24 hr in BA and 0.70 +/- 0.85 ng/ml in WA (p = 0.0624); secreted t-PA antigen, 18.65 +/- 17.06 ng/ml in BA and 10.37 +/- 6.38 ng/ml in WA (p = 0.0422); t-PA/cyclophilin mRNA ratios (Northern blot analysis), 1.90 +/- 1.34 in BA and 1.32 +/- 0.70 in WA (p = 0.0776); cell-associated PAI-1 antigen, 71.10 +/- 30.16 ng/ml/8.6 x 10(5) cells/24 hr in BA and 108.85 +/- 56.89 ng/ml in WA (p = 0.0022); secreted PAI-1 antigen, 1,582.13 +/- 612.67 ng/ml in BA and 1,992.17 +/- 711.50 ng/ml in WA (p = 0.0285); 2.4 kb PAI-1/cyclophilin mRNA ratios, 0.59 +/- 0.39 in BA and 0.79 +/- 0.31 in WA (p = 0.1085); 3.4 kb PAI-1/cyclophilin mRNA ratios, 0.70 +/- 0.47 in BA and 0.77 +/- 0.54 in WA (p = 0.6322). These combined data suggest that cultured HUVECs from BA express significantly higher levels of t-PA, lower levels of PAI-1 and approximately 1.72-fold lower molar ratio of PAI-1/t-PA antigen (183.99 +/- 168.81 vs. 315.92 +/- 164.99) (p < 0.05) than cultured HUVECs from WA, presumably reflecting an apparent inherent increased fibrinolytic potential in cultured HUVEC derived from BA.

Correlations between platelet aggregation, fibrinolysis, peripheral and central serotonergic measures in subhuman primates

We have studied the relationships between whole blood and plasma serotonin (5-hydroxytryptamine, 5-HT), its major metabolite 5-hydroxyindoleacetic acid (5-HIAA) and serum lipids, platelet aggregation in the whole blood and in the platelet-rich plasma (PRP), and some fibrinolytic parameters in monkeys. Plasma 5-HT was found to be positively related to 5-HT- and ADP-induced platelet aggregation, tissue plasminogen activator (tPA) activity, serum cholesterol and LDL-cholesterol, whereas 5-HT in cerebrospinal fluid correlated inversely with serum cholesterol. Plasminogen activator inhibitor (PAI) activity was positively related to LDL. Euglobulin clot lysis time was related to both tPA and PAI activities. The significance of these findings and the possible role of 5-HT in atherogenesis and hemostasis are discussed.