Increased plasma plasminogen activator inhibitor 1 levels. A possible link between insulin resistance and atherothrombosis

According to recent prospective studies, hypofibrinolysis due to elevated plasma plasminogen activator inhibitor 1 levels appears to be an independent risk factor for myocardial reinfarction in men, and hyperinsulinaemia, a major indicator of insulin resistance is considered as a risk factor for coronary disease. It has recently been shown that insulin resistance is accompanied by an increased plasma plasminogen activator inhibitor 1 concentration: A significant correlation coefficient was demonstrated between plasminogen activator inhibitor 1 and fasting plasma insulin in the normal population, in obese subjects, in Type 2 (non-insulin-dependent) diabetic patients and in angina pectoris. Attempts to decrease insulin resistance such as fasting, diet, or administration of an oral anti-diabetic drug such as Metformin induced a parallel decrease in plasma insulin and plasminogen activator inhibitor 1 levels. This inhibitor is produced by endothelial cells and by hepatocytes in culture. Plasminogen activator inhibitor 1 synthesis by hepatocytes in culture was stimulated by an increasing insulin concentration, or low density lipoproteins, whereas the endothelial cell synthesis was stimulated by very low density lipoproteins especially when they were obtained from hypertriglyceridaemic patients. Therefore, a direct effect of insulin or lipoprotein changes on the cells which synthesize plasminogen activator inhibitor 1 could be responsible for its increased plasma concentration in insulin resistance states. The increase in plasma plasminogen activator inhibitor 1 levels linked to hyperinsulinaemia is a tempting partial explanation for the association between insulin resistance and coronary disease.

Fibrinolytic factors and the risk of myocardial infarction or sudden death in patients with angina pectoris. ECAT Study Group. European Concerted Action on Thrombosis and Disabilities

BACKGROUND

Disturbances of the fibrinolytic system that lead to decreased removal of fibrin deposits may be important risk factors for coronary thrombosis. There is as yet no consensus on the prognostic value of fibrinolytic parameters, which may be attributed in part to the choice of confounding variables controlled for.

METHODS AND RESULTS

The ECAT study is a prospective multicenter study of 3043 patients with angina pectoris followed for 2 years. Baseline measurements included 10 fibrinolytic variables. The results were analyzed in relation to the subsequent incidence of myocardial infarction or sudden coronary death. They are presented before and after adjustment for clusters of confounding variables that are markers of different mechanisms: insulin resistance (body mass index, triglyceride, and HDL cholesterol), inflammation (fibrinogen and C-reactive protein), and endothelial cell damage (von Willebrand factor). An increased incidence of events was associated with higher baseline concentrations of tissue plasminogen activator (TPA) antigen (P = .0002), plasminogen activator inhibitor-1 (PAI-1) activity (P = .02), and PAI-1 antigen (P = .001). The associations of PAI-1 activity and PAI-1 antigen with risk of events disappeared after adjustment for parameters reflecting insulin resistance but were not affected by other adjustments. TPA antigen was affected to a similar extent by adjustment for parameters reflecting insulin resistance. Inflammation, or endothelial cell damage, but the risk association disappeared only after combined adjustments.

CONCLUSIONS

The prognostic role of PAI-1 in predicting coronary events is related principally to insulin resistance, whereas that of TPA antigen could be explained only by its relationship with different mechanisms, including insulin resistance, inflammation and endothelial cell damage.

Production of plasminogen activator inhibitor 1 by human adipose tissue: possible link between visceral fat accumulation and vascular disease

Plasminogen activator inhibitor type 1 (PAI-1) contributes to the pathogenesis of atherothrombosis. Its plasma level is strongly correlated with parameters that define the insulin resistance syndrome, in particular with BMI and visceral accumulation of body fat, suggesting that PAI-1 may be an adipose tissue-derived circulating peptide. The present study was designed to investigate PAI-1 expression by human adipose tissue and its different cellular fractions. Special interest has been paid to the amount of PAI-1 antigen produced by omental versus subcutaneous fat. PAI-1 protein detected by immunolocalization was present at the stromal and adipocyte levels. PAI-1 mRNA was detected in stromal vascular cells freshly isolated and under culture conditions. It was also detected in whole adipose tissue and adipocyte fraction under culture conditions. The mRNA signal from the adipocyte fraction was detected as early as 2 h of incubation. The increase in PAI-1 mRNA was followed by an increase in PAI-1 antigen in the conditioned medium that was suppressed by treatment with cycloheximide. Transforming growth factor-beta1 significantly increased PAI-1 antigen production by the adipocyte fraction, whereas tumor necrosis factor-alpha did not have any effect. Interestingly, after 5 h of incubation, omental tissue explants produced significantly more PAI-1 antigen than did subcutaneous tissue from the same individual, whereas similar production of leptin by the two territories was observed. These results strongly suggest that human adipose tissue, in particular visceral tissue, can be an important contributor to the elevated plasma PAI-1 levels observed in central obesity.

Correlation between blood fibrinolytic activity, plasminogen activator inhibitor level, plasma insulin level, and relative body weight in normal and obese subjects

This study was undertaken to obtain further information on the mechanism by which blood fibrinolytic activity, a balance between plasminogen activators and inhibitors, is lowered in obese subjects. Fasting blood samples were collected from 35 subjects, aged 15 to 45 years, with normal glucose tolerance and a Body Mass Index (BMI) varying widely between 16 and 45 (normal, 19 to 25). Euglobulin Fibrinolytic Activity (EFA) did not correlate with the level of tissue type plasminogen activator (t-PA) related antigen but exhibited a negative correlation with the level of PA inhibitor (r = -.609, P less than 0.01). EFA was negatively and PA inhibitor positively correlated with both BMI (r = -.381, P less than 0.02 and .664, P less than 0.01, respectively) and plasma insulin level (r = .410, P less than 0.02 and .521, P less than 0.01, respectively). Stepwise analysis showed that these correlations were independent. As expected, plasma insulin was correlated with BMI (r = .512, P less than 0.01) and triglyceride level (r = .38, P less than 0.02), total cholesterol with age (r = .379, P less than 0.02). Ten obese subjects were submitted to a 24-hour fast. While body weight did not change appreciably, plasma insulin decreased from 22.3 +/- 2.2 to 16.3 +/- 1.1 microU/ml, EFA increased from 3.6 +/- .8 to 4.9 +/- .67 mm, and PA inhibitor decreased from 4.52 +/- .76 to 3.44 +/- .63 IU/mL. All these differences were significant. T-PA-related antigen did not change.(ABSTRACT TRUNCATED AT 250 WORDS)

C3H/HeJ mice carrying a toll-like receptor 4 mutation are protected against the development of insulin resistance in white adipose tissue in response to a high-fat diet

AIMS/HYPOTHESIS

Inflammation is associated with obesity and has been implicated in the development of diabetes and atherosclerosis. During gram-negative bacterial infection, lipopolysaccharide causes an inflammatory reaction via toll-like receptor 4 (TLR4), which has an essential function in the induction of innate and adaptative immunity. Our aim was to determine what role TLR4 plays in the development of metabolic phenotypes during high-fat feeding.

MATERIALS AND METHODS

We evaluated metabolic consequences of a high-fat diet in TLR4 mutant mice (C3H/HeJ) and their respective controls.

RESULTS

TLR4 inactivation reduced food intake without significant modification of body weight, but with higher epididymal adipose tissue mass and adipocyte hypertrophy. It also attenuated the inflammatory response and increased glucose transport and the expression levels of adiponectin and lipogenic markers in white adipose tissue. In addition, TLR4 inactivation blunted insulin resistance induced by lipopolysaccharide in differentiated adipocytes. Increased feeding efficiency in TLR4 mutant mice was associated with lower mass and lower expression of uncoupling protein 1 gene in brown adipose tissue. Finally, TLR4 inactivation slowed the development of hepatic steatosis, reducing the liver triacylglycerol content and also expression levels of lipogenic and fibrosis markers.

CONCLUSIONS/INTERPRETATION

TLR4 influences white adipose tissue inflammation and insulin sensitivity, as well as liver fat storage, and is important in the regulation of metabolic phenotype during a fat-enriched diet.

Plasminogen activator inhibitor 1, transforming growth factor-beta1, and BMI are closely associated in human adipose tissue during morbid obesity

In adipose tissue from both obese mice and humans, plasminogen activator inhibitor 1 (PAI-1) expression has been reported to be upregulated to levels of increased plasma PAI-1. This elevated expression has been shown to be partly controlled by tumor necrosis factor (TNF)-alpha in mice. In humans, increased PAI-1 expression is associated with insulin resistance characterized by visceral fat accumulation. Therefore, the aim of this study was to investigate the expression pattern of PAI-1 and TNF-alpha (antigen and mRNA) in visceral human adipose fat in comparison with subcutaneous (SC) fat. Because transforming growth factor (TGF)-beta1 is a potent inducer of PAI-1 synthesis and has been shown to influence adipocyte metabolism, this work was extended to TGF-beta1 quantification. A total of 32 obese individuals (BMI 42 +/- 6.8 kg/m2) were investigated. Freshly collected visceral adipose tissue did not exhibit a higher content of PAI-1 or TGF-beta1 than did SC tissue. Although most of the TNF-alpha values were at the detection limit of the methods, TNF-alpha antigen was 3-fold higher and TNF-alpha mRNA was 1.2-fold higher in visceral fat. The levels of tissue TGF-beta1 antigen correlated well with those of PAI-1 antigen, regardless of the fat depot studied (SC tissue: n = 21, r = 0.72, P = 0.0006; visceral tissue: n = 20, r = 0.49, P < 0.03), and they were both significantly associated with BMI. Conversely, no relationship was observed between the levels of TNF-alpha and PAI-1 or TNF-alpha and BMI. Tissue PAI-1 levels were also significantly correlated with those of circulating PAI-1. These results describe, in severe obesity, a proportional increase in tissue PAI-1 and TGF-beta1 in visceral and SC tissues. This increased PAI-1 expression could be the result of tissue cytokine disturbances, such as elevated TGF-beta1 expression.

Deficient t-PA Release and Elevated PA Inhibitor Levels in Patients with Spontaneous or Recurrent Deep Venous Thrombosis

The fibrinolytic system was investigated in 120 patients with spontaneous or recurrent deep vein thrombosis (DVT) without any known organic disease able to explain by itself the occurrence of a thrombosis and without any known defect of antithrombin III, Heparin Cofactor II, Protein C, or Protein S. The assays included: Euglobulin fibrinolytic activity (EFA), tissue-type plasminogen activator related antigen (t-PA-Ag) and plasminogen activator inhibitor activity (PA inhibitor), which were measured before and after 10 min of venous occlusion (V. O.). On the basis of the results, the patients could be classified in 3 groups:good responders with an at least two-fold increase of EFA after venous occlusion (n = 76), poor responders with a lesser increase of EFA due to deficient release of t-PA (n = 12), and poor responders with a normal t-PA release but an increased level of PA-Inhibitor (n = 32).

The poor responders due to deficient t-PA release (10% of total) had a higher incidence of recurrence of deep vein thrombosis, than the other groups (p <0.01). An overall correlation was found between the level of PA-Inhibitor activity and the triglyceride level (r = 0.40, p <0.01), suggesting that these elevations may be due to a common cause, at least in some of the patients.

It is concluded that a poor fibrinolytic response to venous occlusion occurs in 35 percent of DVT patients. Poor responders however fall into two categories, one fourth with deficient t-PA release who have a high risk for recurrent venous thrombosis, and three fourth with increased PA-Inhibitor levels which may be associated with underlying diseases also causing hypertriglyceridemia. Further elucidation of the correlation between recurrent venous thrombosis and deficient fibrinolysis is expected to result in more specific and adequate treatment and prevention of DVT.

Insulin Stimulates the Synthesis of Plasminogen Activator Inhibitor 1 by the Human Hepatocellular Cell Line Hep G2

Secretion of plasminogen activator inhibitor 1 (PAI-1) by cultures of human umbilical vein endothelial cells and human hepatocellular cell line Hep G2 was evaluated after insulin stimulation. The secretion of PAI-1 antigen and activity was measured in the conditioned medium and the cellular extracts after incubation of confluent cultures with 1% serum medium for 24 hours.

Insulin induced a dose dependent increase of the PAI-1 secretion by Hep G2 cell line. At 10-8 M a two fold increase of PAI-1 antigen and activity were observed whereas a2 antiplasmin and fibrinogen were not significantly modified. No effect of insulin was observed on PAI-1 antigen and PAI activity production by human endothelial cells whereas endotoxin resulted in a two fold increase in PAI-1 secretion. In recent clinical studies we have demonstrated that the level of plasma insulin correlated with that of PAI-1. Thus we hypothesize that hepatocytes represent a physiological source of plasma PAI-1 which is modulated by plasma insulin level.

Clearance of tissue plasminogen activator (TPA) and TPA/plasminogen activator inhibitor type 1 (PAI-1) complex: relationship to elevated TPA antigen in patients with high PAI-1 activity levels

BACKGROUND

To evaluate the effect of plasminogen activator inhibitor type 1 (PAI-1) levels on the clearance of total tissue plasminogen activator (TPA) antigen, we studied the clearance of active TPA and TPA/PAI-1 complex in subjects with low (181+/-109 pmol/L; n=7) and high (1166+/-322 pmol/L; n=4) baseline active PAI-1.

METHODS AND RESULTS

A 5-microg/kg bolus of TPA was infused over a 15-second period followed by measurement of TPA activity, TPA antigen, TPA/PAI-1, TPA/C1 inhibitor, PAI-1 activity, and PAI-1 antigen over a 4-hour period. alpha-Phase clearance of total TPA antigen was faster in subjects with low PAI-1 (t(1/2) of 3.5+/-0.7 minutes) versus high PAI-1 (t(1/2) of 5.3+/-0.9 minutes) (P=.006). Clearance of all factors was best fit by a two-compartment pharmacokinetic model based on a computer-simulated human circulatory system. The average hepatic clearance fraction in the two-compartment model was greater for active TPA (89+/-10%, t(1/2) of 2.4+/-0.3 minutes) than for TPA/PAI-1 complex (48+/-17%, t(1/2) of 5.0+/-1.8 minutes) (P=.0006).

CONCLUSIONS

Plasma clearance of active TPA was faster than clearance of TPA/PAI-1 complex. High levels of active PAI-1 converted more TPA into TPA/PAI-1 complex, effectively slowing the clearance of total TPA antigen and explaining in part why high levels of PAI-1 activity are associated with increases in total TPA antigen.

Endothelial Cell Markers and the Risk of Coronary Heart Disease

Background— Tissue factor pathway inhibitor (TFPI), von Willebrand factor (vWF), and thrombomodulin (TM) are 3 major hemostatic regulatory molecules synthesized by endothelium. Data from epidemiological studies aiming to evaluate the relation between plasma levels of these molecules and the development of coronary heart disease (CHD) are sparse or contradictory.

Methods and Results— We examined the association between these endothelial-cell markers and the incidence of fatal or nonfatal myocardial infarction (hard CHD) and stable or unstable angina (angina pectoris) in a prospective cohort (the PRIME Study) of nearly 10 000 healthy men recruited in France and Northern Ireland. We measured baseline plasma concentration of the free form of TFPI (f-TFPI), vWF, and the soluble form of TM (sTM) among 296 participants who subsequently developed CHD over the 5-year follow-up (158 with hard CHD and 142 with angina pectoris) and in 563 control subjects by use of a nested case-control design. Individuals with plasma vWF levels in the highest quartile showed a 3.04-fold increase in the risk of hard CHD compared with those in the lowest quartile (95% CI, 1.59 to 5.80). Individuals with f-TFPI levels below the 10th percentile had a 2.13-fold increased risk of hard CHD compared with those with levels above it (95% CI, 1.08 to 4.18). The risk for both molecules persisted after control for inflammatory parameters. Individuals with vWF levels in the highest quartile and f-TFPI levels below the 10th percentile presented a 6.9-fold increased risk of hard CHD compared with those with vWF levels in the lowest quartile and f-TFPI levels above the 10th percentile (95% CI, 1.3 to 37.8).

Conclusions— vWF and f-TFPI plasma levels were independent risk factors for hard CHD events.

Plasma plasminogen activator inhibitor-1 in angina pectoris. Influence of plasma insulin and acute-phase response

Plasminogen activator inhibitor-1 (PAI-1) is an important physiological inhibitor of fibrinolysis. It circulates in blood both in free active form and in inactive form complexed with tissue type plasminogen activator (t-PA). Control mechanisms for its synthesis and release from hepatocytes and endothelial cells are important in the pathogenesis of thrombosis. Possible risk factors for myocardial infarction include high insulin and PAI-1 levels, which correlate with one another in healthy subjects, and fibrinogen, which together with PAI-1, is an acute-phase reactant. We therefore studied the interrelationships between PAI-1, plasma insulin, and acute-phase proteins in 67 patients with angina pectoris. Plasma insulin correlated strongly (r = 0.59, p less than 0.001) with PAI activity, free PAI-1 antigen (r = 0.60, p less than 0.001), and total PAI-1 antigen (r = 0.58, p less than 0.001). The acute-phase proteins, fibrinogen and C-reactive protein, correlated significantly with t-PA antigen, total PAI-1 antigen, and PAI-1/t-PA complexes but not with PAI activity or free PAI-1. The results suggest that insulin stimulates synthesis and release of free PAI-1 (probably via hepatocytes as previously shown with cell culture) and that endothelial cell synthesis and release of t-PA, together with PAI-1, reflects a nonspecific acute-phase response to chronic vascular disease. Hyperinsulinemia found in patients with angina pectoris could play a role in the development of myocardial infarction via the induction of high plasma PAI-1 activity.

Granulocyte-endothelium initial adhesion. Analysis of transient binding events mediated by E-selectin in a laminar shear flow

The adhesion of moving cells to receptor-bearing surfaces is a key step to many important biological processes. Attachment was subjected to extensive modeling. However, the numerical values of kinetic bonding parameters relevant to realistic models of cell adhesion remain poorly known. In this report, we describe the motion of human granulocytes to interleukin-1-activated endothelial cells in presence of a low hydrodynamic drag (a few piconewtons) estimated to be much weaker than a standard ligand-receptor bond. It was thus expected to visualize the formation and rupture of individual bonds. We observed multiple short-time cell arrests with a median duration of 2.43 s. Stop frequency, not duration, was significantly inhibited by anti-E-selectin antibodies. Binding efficiency exhibited an almost linear relationship with the inverse of cell velocity. The distribution of arrest duration was determined: results were consistent with the view that these arrests reflected the formation/dissociation of single ligand-receptor bonds with a spontaneous dissociation rate of 0.5 s-1. The rate of bond formation was on the order of 0.04 s-1 when cells were freely rolling (mean velocity: 19 microns/s) and it exhibited an approximately 10-fold increase after the formation of a first adhesion.

Increased Plasminogen Activator Inhibitor Activity in Non Insulin Dependent Diabetic Patients – Relationship with Plasma Insulin

Type 2 diabetic patients are known to frequently have a high insulin level and were recently described as having high plasminogen activator inhibitor (PAI) activity, compared to normal controls. As we have shown in several clinical conditions (normal subjects, obese patients, angina pectoris patients) that plasma PAI activity was linked with plasma insulin, we have studied in 38 type 2 diabetic patients the relationship between PAI activity, insulin and other parameters. Patients showed higher level of PAI activity, as well as plasma glucose, insulin, triglyceride, cholesterol and Apolipoprotein B levels than normal controls; highest values were observed with diabetic patients also affected by coronary artery disease. A significant correlation was found between PAI activity and insulin (r = 0.60, p <0.001), body mass index (r = 0.32, p <0.05) and Apolipoprotein B (r = 0.33, p <0.05). The two latter correlations disappeared after adjustment for insulin.

These results are in agreement with our previous report showing an in vitro effect of insulin on the synthesis of PAI by a hepatocellular cell line. Hyperinsulinemia presented by type 2 diabetic patients may increase the hepatic synthesis of PAI, inducing an hypofibrinolysis, which could play a role in the development of the vascular complications.

Attempts to reduce hyperinsulinemia could have a favorable effect by lowering PAI activity.

Plasma thrombin-activatable fibrinolysis inhibitor antigen concentration and genotype in relation to myocardial infarction in the north and south of Europe

The thrombin-activatable fibrinolysis inhibitor (TAFI) is a recently described inhibitor of fibrinolysis that decreases plasminogen binding to the fibrin surface. The plasma TAFI concentration is almost entirely genetically determined. We investigated whether plasma TAFI levels and polymorphisms located in the TAFI gene could constitute risk markers of myocardial infarction (MI). Plasma TAFI antigen (Ag) levels were assayed by ELISA and 2 TAFI gene polymorphisms (Ala147Thr and C+1542G in the 3' untranslated region) were determined in a large European case-control study. This study compared 598 men recruited 3 to 6 months after MI with 653 age-matched controls from North Europe (Stockholm, Sweden, and London, England) and South Europe (Marseilles, France, and San Giovanni Rotondo, Italy). A TAFI Ag value above the 90th percentile was associated with a significantly lower risk of MI (odds ratio 0.55, P<0.02), indicating that elevated TAFI may be protective against MI. As previously shown, the 2 TAFI gene polymorphisms were in strong linkage disequilibrium and were associated with the TAFI Ag concentration, with carriers of the Thr147 and 1542C alleles having higher levels (P<0.0005). These effects were similar in controls and cases and in each center. There was a difference in allele frequency between cases and controls for the Ala147Thr polymorphism, with Thr147 allele carriers being more frequent in controls than in cases in 2 centers, Stockholm (P=0.03) and San Giovanni Rotondo (P=0.03); the odds ratio for the entire cohort was 0.78 (P<0.05). In conclusion, patients with a recent MI presented lower values of TAFI Ag and higher frequencies of the "TAFI-decreasing" alleles. The geographical differences observed do not contribute to explaining the North-South gradient in MI risk in Europe.

Identification of polymorphisms in the promoter and the 3' region of the TAFI gene: evidence that plasma TAFI antigen levels are strongly genetically controlled

Thrombin-activable fibrinolysis inhibitor (TAFI) is a recently described carboxypeptidase that is potentially involved in the regulation of fibrinolysis by decreasing plasminogen binding to the fibrin surface. This role makes the TAFI gene a good candidate in atherothrombotic diseases. The great interindividual variability of plasma TAFI antigen levels is poorly explained by lifestyle characteristics, thus suggesting its genetic determination. To test this hypothesis, the promoter and the 3'-untranslated region of the TAFI gene were screened for polymorphisms, and their contribution to the variability of plasma TAFI antigen levels was evaluated. Seven new polymorphisms are described, 5 in the promoter (C-2599G, -2345 2G/1G, A-1690G, G-1102T, and G-438A) and 2 in the 3'UTR (C+1542G and T+1583A). All these polymorphisms were in strong linkage disequilibrium with each other and with the previously described Ala147Thr polymorphism. They generated 4 main haplotypes, accounting for 80% of all observed haplotypes. In univariate analyses, all polymorphisms were associated with plasma TAFI Ag levels and, individually, contributed to a large fraction of plasma TAFI Ag levels, ranging from 20% to 52%. In a stepwise regression analysis including all polymorphisms, several combinations remained significantly and independently associated with plasma TAFI Ag levels: C+1542G associated with Ala147Thr, T+1583A, or -2345 2G/1G explaining 61.6%, 60.2%, and 58.1% of the variance, respectively. These findings clearly demonstrate that circulating levels of TAFI are strongly determined by polymorphic variations in the promoter and the 3'UTR of the TAFI gene. (Blood. 2001;97:2053-2058)

Metformin Decreases the High Plasminogen Activator Inhibition Capacity, Plasma Insulin and Triglyceride Levels in Non-Diabetic Obese Subjects

We have previously observed a positive correlation between Plasminogen Activator Inhibition capacity (PA Inhibition), Body Mass Index (BMI) and plasma insulin levels in a population of non diabetic subjects. The anti diabetic biguanide Metformin which decreases insulin resistance has been reported to increase the blood fibrinolytic activity. Therefore we have studied the effect of Metformin on PA Inhibition levels in obese subjects with normal glucose tolerance. Eighteen obese women (O) (BMI: 31.4 ± 1.13, m ± S.E.M.) were compared to age matched controls (C) (BMI: 20.2 ± 0.8) and randomized to a 15 days treatment by Metformin (M) (1.7 g/day) or placebo (P) in a double blind study while on a weight maintaining diet. O compared to C had higher levels (m ± S.E.M.) of PA Inhibition (9 ± 1.8 IU/ml, versus 2.88 ± 0.29 p <0.01), lower euglobulin fibrinolytic activity (EFA) (4.95 ±1.17 mm versus 9 ± 0.29 p <0.05), higher plasma insulin (24.1 ±2.1. uU/ml), versus 12 ± 1 p <0.01) and triglyceride (1.32 ± 0.16 mmol/1, versus 0.8 ± 0.08 p <0.05). After 15 days of treatment, in group M a significant decrease in PA Inhibition (5.51 ± 1.4, versus 9.48 ±2.1 p <0.05) in plasma insulin (18.5 ±0.1, versus 24.5 ± 3.5, p <0.05) and plasma triglyceride (1.08 ± 0.1, versus 1.47 ± 0.3 p <0.05) and an increase in EFA (6.50 ± 0.28, versus 5.25 ± 0.35 p <0.05) were observed. No significant variation was observed in group P.

Thrombogenic and fibrinolytic factors and cardiovascular risk in non-insulin-dependent diabetes mellitus

Disturbances of the haemostatic system may favour the development of vascular damage and the final occlusion events in the progress of coronary heart disease (CHD). It has been shown recently in epidemiological studies, that increased concentration of several factors, mainly fibrinogen, factor VII, von Willebrand factor (vWF), and the fibrinolytic variables plasminogen activator inhibitor 1 (PAI-1) and tissue plasminogen activator (t-PA), can be considered as risk factors for CHD. As morbidity and mortality through coronary atherosclerosis are higher in type 2 diabetic patients than in nondiabetic subjects and as insulin resistance represents a situation which favours the development of atherothrombosis, evaluation of the haemostatic factors which are recognized as risk factors may be interesting to consider in these situations. In fact, it has been shown that the fibrinolytic parameters PAI-1 and t-PA antigen are strongly related to the metabolic disorder of insulin resistance, whereas the link with fibrinogen, factor VII, and vWF remains weak. Many cross-sectional studies conducted in different populations have shown that PAI-1 and t-PA antigen (which represents t-PA/PAI-1 complexes) are strongly correlated with insulin, triglyceride, high-density lipoprotein (HDL) cholesterol, body mass index, walst-to-hip ratio and blood pressure, and that the improvement of insulin resistance improves in parallel the metabolic abnormalities and the concentration of the fibrinolytic parameters. Attempts at explaining the elevated PAI-1 and t-PA antigen levels in the insulin resistance syndrome have involved many clinical and in vitro studies, in which the role of insulin, insulin propeptides, very-low-density lipoprotein (VLDL) triglyceride, insulin resistance per se, glucose, and adipose tissue have successively been analysed and the main results of these studies are presented in this review. Due to recent experimental data from animal models of thrombosis, a pathogenic role of decreased fibrinolytic activity or increased PAI-1 levels can be proposed and could play a role in the development of vascular disease in subjects with Type 2 diabetes or insulin resistance.

Fat distribution and plasminogen activator inhibitor activity in nondiabetic obese women

Epidemiologic data strongly suggest that upper distribution of body fat and high plasminogen activator inhibitor (PAI) activity are risk factors for cardiovascular disease. Therefore, a link between these two parameters was evaluated by studying 51 menstrually active nondiabetic obese women. In this group positive correlations were observed between body mass index (BMI), waist to hip circumference ratio (W/H ratio, which estimates body fat distribution), plasma insulin, and PAI activity. In addition, plasma triglycerides were related to the W/H ratio and insulin and PAI activity. Partial correlations revealed that BMI was independently and solely related to W/H ratio, which was also independently related to plasma insulin, which in turn related to PAI activity. These results suggest that upper body fat distribution acts as a risk factor of cardiovascular disease through its association with high PAI activity.

Fibrinolytic and inflammatory processes in pleural effusions

This study was designed to evaluate major fibrinolytic parameters in relation to parameters of inflammation associated with different kinds of pleural effusion. Sixty patients with pleural effusion were studied. The underlying aetiology was empyema in 10 cases, tuberculosis in 9, cancer in 31, cardiac failure in 7, and undetermined in 3. Plasminogen, plasminogen activator inhibitor 1 (PAI-1) and 2 (PAI-2), tissue type plasminogen activator (t-PA), urokinase (u-PA) and D-dimers (D-D) were quantified in plasma samples and pleural effusion specimens. These data were then correlated with inflammatory or infectious parameters, i.e. fibrinogen, von Willebrand factor (vWF), erythrocyte sedimentation rate (ESR), protein concentration, and white blood cell count. D-D levels were higher in pleural fluid than in plasma. D-D levels were not correlated with either plasminogen activator or plasminogen activator inhibitor levels, suggesting the presence of other fibrinolytic pathways. PAI levels (PAI activity, PAI-1 antigenicity, PAI-2 antigenicity) and vWF levels were significantly higher in patients with tuberculosis and empyema than in patients with cancer or cardiac failure. Regression analysis between inflammatory and fibrinolytic parameters showed that pleural PAI levels were significantly correlated with pleural neutrophil count, vWF levels, and plasma fibrinogen levels. D-D levels were correlated with blood ESR. No significant difference in pleural t-PA, u-PA and D-D levels was observed between aetiologies. The highest pleural t-PA and u-PA values were noted in patients with cancer, especially lymphoma. Plasma t-PA levels were higher inpatients with pleural effusion secondary to congestive heart failure, but this difference did not reach statistical significance.(ABSTRACT TRUNCATED AT 250 WORDS)

Subcutaneous abdominal, but not femoral fat expression of plasminogen activator inhibitor-1 (PAI-1) is related to plasma PAI-1 levels and insulin resistance and decreases after weight loss

AIMS/HYPOTHESIS

Abdominal fat produces plasminogen activator inhibitor-1 (PAI-1) and could contribute to increased plasma PAI-1 values in human obesity associated with insulin resistance. Femoral fat, which is not associated with insulin resistance, is thought to be metabolically different from the abdominal fat. This study aimed to assess PAI-1 expression in these two fat territories in obese and lean subjects and to determine if concomitant changes of plasma and adipose tissue PAI-1 values occur after weight reduction.

METHODS

In 24 obese and 16 lean subjects, PAI-1 expression in abdominal and femoral subcutaneous fat, plasma PAI-1, insulin, triglyceride concentrations and insulin resistance were determined at the start of the study and in obese subjects after a 3-month weight reduction programme as well.

RESULTS

PAI-1 mRNA content in the abdominal subcutaneous fat was higher in obese than in lean subjects and positively correlated with plasma PAI-1 values (p < 0.01) and markers of insulin resistance (p < 0.05). In 18 obese subjects, re-examined after successful dieting, PAI-1 mRNA content decreased in the abdominal subcutaneous fat along with plasma PAI-1. However, the absolute changes of these two variables were not associated. In contrast, PAI-1 mRNA content in the femoral subcutaneous fat did not differ between lean and obese subjects, was not associated with plasma PAI-1 values or with markers of insulin resistance, and did not change after weight loss.

CONCLUSION/INTERPRETATION

Only the abdominal, but not the femoral subcutaneous fat PAI-1 expression is a potential contributor to increases in plasma PAI-1 in obesity. Both plasma and abdominal subcutaneous fat PAI-1 values decreased significantly after weight reduction, although their absolute changes were not associated.

The inflammatory receptor CD40 is expressed on human adipocytes: contribution to crosstalk between lymphocytes and adipocytes

AIMS/HYPOTHESIS

Obesity is associated with adipose tissue inflammation. The CD40 molecule, TNF receptor superfamily member 5 (CD40)/CD40 ligand (CD40L) pathway plays a role in the onset and maintenance of the inflammatory reaction, but has not been studied in human adipose tissue. Our aim was to examine CD40 expression by human adipocytes and its participation in adipose tissue inflammation.

METHODS

CD40 expression was investigated in human whole adipose tissue and during adipocyte differentiation by real-time PCR, Western blot and immunohistochemistry. The CD40/CD40L pathway was studied using recombinant CD40L (rCD40L) in adipocyte culture and neutralising antibodies in lymphocyte/adipocyte co-culture.

RESULTS

CD40 mRNA levels in subcutaneous adipose tissue were higher in the adipocyte than in the stromal-vascular fraction. CD40 expression was upregulated during adipocyte differentiation. Addition of rCD40L to adipocytes induced mitogen activated protein kinase (MAPK) activation, stimulated inflammatory adipocytokine production, and decreased insulin-induced glucose transport in parallel with a downregulation of IRS1 and GLUT4 (also known as SCL2A4). rCD40L decreased the expression of lipogenic genes and increased lipolysis. CD40 mRNA levels were significantly higher in subcutaneous adipose tissue than in visceral adipose tissue of obese patients and were positively correlated with BMI, and with IL6 and leptin mRNA levels. Lymphocyte/adipocyte co-culture led to an upregulation of proinflammatory adipocytokines and a downregulation of leptin and adiponectin. Physical separation of the two cell types attenuated these effects, suggesting the involvement of a cell-cell contact. Blocking the CD40/CD40L interaction with neutralising antibodies reduced IL-6 secretion from adipocytes.

CONCLUSIONS/INTERPRETATION

Adipocyte CD40 may contribute to obesity-related inflammation and insulin resistance. T lymphocytes regulate adipocytokine production through both the release of soluble factor(s) and heterotypic contact with adipocytes involving CD40.

Influence of PAI-1 on adipose tissue growth and metabolic parameters in a murine model of diet-induced obesity

An increased plasma plasminogen activator inhibitor-1 (PAI-1) level is a risk factor for myocardial infarction, particularly when associated with visceral obesity. Although the link between PAI-1 and obesity is well documented, little is known about the physiological relevance of PAI-1 production by adipose tissue. Therefore, we have compared adipose tissue development and insulin resistance plasma parameters in PAI-1-deficient mice (PAI-1(-/-)) and wild-type littermates (PAI-1(+/+)) in a model of nutritionally induced obesity. After 17 weeks of consuming a high-fat diet (HFD), PAI-1(+/+) mice showed marked obesity, with a 52% increase in body weight compared with mice that were kept on a standard fat diet (P<0.0001). This weight gain was accompanied by adipocyte hypertrophy and an increase in the number of stroma cells in the gonadal fat pad, expressed as stroma cells/adipocytes (0.67+/-0.05 versus 0.43+/-0. 02; P<0.001). In plasma, the HFD induced a marked increase in PAI-1 antigen (5.1+/-0.56 versus 2+/-0.22 ng/mL; P<0.001), fasting insulinemia (1.1+/-0.21 versus 0.21+/-0.04 ng/mL; P<0.001), and glycemia (7.4+/-0.5 versus 5+/-0.3 mmol/L; P<0.001), whereas plasma triglyceride levels were not affected. When we compared PAI-1(-/-) and PAI-1(+/+) mice on the HFD, PAI-1(-/-) mice gained weight faster than did PAI-1(+/+) mice, with a significant difference in body weight between 3 and 8 weeks of the diet (32+/-1.7 versus 26+/-1.6 g at 6 weeks; P<0.05). After 17 weeks of the HFD, its effect on weight gain and the number and size of adipocytes was similar in PAI-1(+/+) and PAI-1(-/-) mice. By contrast, the increase in the number of stroma cells presented by PAI-1(+/+) mice was not observed in PAI-1(-/-) mice. In obese PAI-1(-/-) mice, tissue-type PA activity and antigen levels in the gonadal fat pad were significantly higher than in obese PAI-1(+/+) mice (230+/-50 versus 47+/-20 arbitrary units/g, P<0.01; 40+/-13 versus 17+/-13 ng/g, P<0.05, respectively), whereas urokinase-type PA activity and antigen levels were similar in both groups. In plasma, nonobese PAI-1(-/-) mice displayed 62% higher insulin levels (P<0.05) than did PAI-1(+/+) mice. Obese PAI-1(-/-) mice displayed 68% higher triglyceride levels (P<0.01) and 21% lower glucose levels (P<0.05) than did PAI-1(+/+) mice. These data support an effect of PAI-1 on weight gain and adipose tissue cellularity in the induction of obesity in mice. Moreover, PAI-1 influences glucidolipidic metabolism. The elevated expression of PAI-1 observed in human obesity could be involved in mechanisms that control adipose tissue development.

Glucocorticoids and insulin promote plasminogen activator inhibitor 1 production by human adipose tissue

Plasminogen activator inhibitor 1 (PAI-1) is likely to play a role in vascular disease, primarily in subjects with android obesity. It has been demonstrated that PAI-1 is overexpressed in adipose tissue from obese subjects and that visceral adipose tissue produced more PAI-1 than subcutaneous fat. In the present study, the effect of insulin and glucocorticoids, which are key mediators of adipose tissue metabolism, was examined in relation to PAI-1 synthesis by human adipose tissue explants (HAT), collagenase isolated human adipocytes (IHA), cultured human stromal cells (cSC), and differentiated adipocytes from the murine clonal cell line 3T3-F442A. A significant increase in PAI-1 antigen release (1.5-fold) from HAT was detectable after 16 h of treatment with insulin concentrations of at least 10(-8) mol/l. This was associated with a PAI-1 mRNA increase. Concomitant addition of insulin (10(-8) mol/l) to forskolin (5 x 10(-5) mol/l) reversed the decrease in PAI-1 antigen caused by forskolin alone. No effect on PAI-1 antigen was observed when insulin was incubated with IHA or cSC. 3T3 F442A cells were sensitive to insulin with a four- and twofold increase in PAI-1 antigen and mRNA levels, respectively, after 16 h of stimulation with 10(-8) mol/l. Dexamethasone (DXM) significantly enhanced PAI-1 antigen and mRNA expression by HAT (1.5- and 2.5-fold increase, respectively) at concentrations of at least 10(-8) mol/l. A higher stimulation was observed with IHA (sevenfold increase) and with the differentiated 3T3 F442 cell line. Cortisol was found to be less potent than DXM. No effect was observed when glucocorticoids were incubated with cSC. Coincubation of HAT with insulin (10(-7) mol/l) and DXM (10(-7) mol/l) led to an additive effect on PAI-1 synthesis. These results support the hypothesis that PAI-1 expression in human adipose tissue is controlled by insulin and glucocorticoids and may help to explain the increase in plasma PAI-1 levels observed in patients with android obesity.

Metabolic determinants are much more important than genetic polymorphisms in determining the PAI-1 activity and antigen plasma concentrations: a family study with part of the Stanislas Cohort

Increased plasma plasminogen activator inhibitor-1 (PAI-1) concentration has been identified as a risk factor for coronary heart disease. We investigated the relative contribution of both metabolic factors involved in the insulin resistance (IR) syndrome and polymorphisms of the PAI-1 gene to plasma levels of PAI-1 in 228 healthy nuclear white families from the Stanislas Cohort. Variables related to IR included body mass index, waist-to-hip ratio, fasting insulin, triglyceride, and HDL cholesterol. Five PAI-1 gene polymorphisms were studied, including a newly described G+12078A substitution in the 3' region. A sex difference was observed, with fathers exhibiting higher IR state and PAI-1 levels and stronger correlations between PAI-1 and IR variables than mothers. Such a difference was not observed in offspring. Family correlations were of similar magnitude for fibrinolytic parameters and IR variables. The PAI-1 genotypes A-844G, -675 4G/5G, and G+12078A polymorphisms, which were in strong linkage disequilibrium, were associated with plasma PAI-1 levels. In multivariate analysis, IR explained a major part of PAI-1 variability (49% in fathers, 29% in mothers), whereas polymorphisms had only a minor contribution, explaining 3% of variability in women and having no significant effect in men. We conclude that plasma levels of PAI-1 are, in a healthy population, primarily determined by the IR syndrome, this relationship being stronger in males. The contribution of the PAI-1 gene seems larger in females. These results deserve special attention for understanding the relationships observed between fibrinolytic parameters and the risk of developing a cardiovascular ischemic event.