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

Plasma levels of tissue plasminogen activator/plasminogen activator inhibitor-1 complex and von Willebrand factor are significant risk markers for recurrent myocardial infarction in the Stockholm Heart Epidemiology Program (SHEEP) study

An impaired fibrinolytic function due to elevated plasma levels of plasminogen activator inhibitor (PAI)-1 activity or tissue plasminogen activator (tPA) antigen is correlated with the development of myocardial infarction (MI) in patients with manifest coronary heart disease. Recently, methods for determining the specific tPA/inhibitor complexes constituting tPA antigen in plasma have become available. In the Stockholm Heart Epidemiology Program (SHEEP) study, 86 of 1212 MI patients, subjected to blood sampling in a metabolically stable period, suffered reinfarction before the end of 1996. These individuals have been compared with an approximately equal number of matched MI patients without recurrence and a group of matched healthy control subjects regarding the plasma concentrations of some hemostatic factors. The hemostatic compounds studied (fibrinogen, von Willebrand factor, tPA antigen, PAI-1, and the tPA/PAI-1 complex) were typically higher in the groups (men and women) with recurrence of MI compared with those without. The plasma concentrations were also typically higher in the pooled groups of patients compared with the groups of healthy control subjects. The largest between-group differences were found for the plasma tPA/PAI-1 complex. The crude odds ratio for reinfarction associated with higher concentration (>/=75th percentile among the control subjects) of tPA/PAI-1 was 1.8 (95% CI 1.1 to 3.1); the corresponding crude odds ratio for von Willebrand factor was 2.3 (1. 3 to 4.0). The tPA/PAI-1 complex correlated strongly with PAI-1 and tPA antigen in all groups and with serum triglycerides and body mass index in all groups except for women with reinfarction. An increased plasma level of tPA/PAI-1 complex is a novel risk marker for recurrent MI in men and women. Most likely, increased plasma levels of tPA/PAI-1 complex reflect impaired fibrinolysis, because the correlation with PAI-1 is strong. Further support is obtained indicating that the plasma concentration of von Willebrand factor is also an important risk marker for recurrent MI.

Moderate alcohol consumption and risk of coronary heart disease among women with type 2 diabetes mellitus

BACKGROUND

Moderate alcohol consumption is associated with reduced risk for coronary heart disease (CHD) in generally healthy populations. We assessed prospectively the association between moderate alcohol intake and CHD risk in women with type 2 diabetes mellitus, a group at high risk for cardiovascular disease.

METHODS AND RESULTS

We studied women in the Nurses' Health Study who reported a diagnosis of diabetes mellitus at >/=30 years of age. During 39 092 person-years of follow-up from 1980 to 1994, there were 295 CHD events documented among this population, including 194 cases of nonfatal myocardial infarction and 101 cases of fatal CHD. Odds ratios derived from logistic regression were used to estimate relative risks (RRs) for CHD as a function of usual alcohol intake, with adjustment for potential confounders. Compared with diabetic women reporting no alcohol intake, the age-adjusted RR for nonfatal or fatal CHD among diabetic women reporting usual intake of 0.1 to 4.9 g (<0.5 drinks) of alcohol daily was 0.74 (95% CI 0.56 to 0.98), and among those reporting usual intake >/=5 g/d, it was 0.48 (95% CI 0.32 to 0.72) (P for trend <0.0001). Inverse associations between alcohol intake and CHD risk remained significant in multivariate analysis adjusting for several other coronary risk factors (0.1 to 4. 9 g/d: RR 0.72 [95% CI 0.54 to 0.96]; >/=5 g/d: RR 0.45 [0.29 to 0.68]).

CONCLUSIONS

Although potential risks of alcohol consumption must be considered, these data suggest that moderate alcohol consumption is associated with reduced CHD risk in women with diabetes and should not be routinely discouraged.

Relationship between lipoprotein(a) phenotypes and plaminogen activator inhibitor type 1 in diabetic patients

It has been demonstrated in vitro that lipoprotein(a) [Lp(a)] increases the endothelial synthesis of plasminogen activator inhibitor 1 (PAI-1). However, this effect in vivo is controversial, and the possible relationship between PAI-1 and Lp(a) phenotypes has not been evaluated. The aim of the study was to determine the influence of Lp(a) and its phenotypes on PAI-1 serum concentrations in diabetic patients. For this purpose we include 75 Caucasian diabetic patients (34 consecutive type I and 41 consecutive type II) without late diabetic complications. Lp(a) and PAI-1 were assessed by ELISA. Lp(a) phenotypes were determined by SDS-PAGE followed by immunoblotting, and grouped according to size in small (F,B,S1,S2), big (S3,S4), and null. A linear correlation between Lp(a) and PAI-1 was not observed either as a whole or when type I and type II diabetic patients were analyzed separately. However, significant differences were detected in PAI-1 levels when Lp(a) phenotypes were considered (small: 42.1+/-31.8 ng/mL; big: 37.2+/-26.1 ng/mL; null: 14.4+/-14.4; p< 0.05). The significant differences were due to the low PAI-1 concentrations observed in patients with null phenotype. Our results suggest that fibrinolytic activity might be preserved in diabetic patients with null Lp(a) phenotype. Furthermore, it could be speculated that diabetic patients with null phenotype should be considered at low risk to develop cardiovascular disease.

Age-related changes in coagulation, fibrinolysis, and platelet aggregation in male WBN/Kob rats

We investigated the age-related changes in blood coagulation, fibrinolysis, and platelet aggregation in male WBN/Kob rats, animals that exhibit spontaneously diabetes mellitus at more than 6 months of age. The rats aged 6 months or more showed significant hyperglycemia, hypoinsulinemia, and hyperlipidemia. As changes in coagulation parameters, the data indicated significant increases in factors II, V, VII, VIII, IX, X, and XII activities; a significant decrease in antithrombin III activity in rats more than 6 months of age; significant increases in fibrinogen level and factor XI activity; and significant decreases in prothrombin time and activated partial thromboplastin time in those more than 9 months of age. As changes in fibrinolytic parameters, the animals showed significant decreases in plasminogen and tissue-type plasminogen activator, and significant increases in alpha2-plasmin inhibitor and plasminogen activator inhibitor at more than 6 months of age. In addition, there were significant correlations between the plasma levels of coagulation/fibrinolytic markers and the 4-hour fasting glucose or lipids. Furthermore, they displayed significant increases in ADP- or collagen-induced platelet aggregation and in cholesterol/phospholipid molar ratio in platelets at more than 9 months of age. The increase in cholesterol/phospholipid ratio may be responsible for hyperaggregation of platelets in diabetic animals. These findings suggest that WBN/Kob rats are suitable for research on blood coagulation abnormalities in diabetes. However, further studies are needed to clarify the details of the mechanisms involved.

Relationship between plasma plasminogen activator inhibitor 1 and insulin resistance

High plasminogen activator inhibitor 1 (PAI-1) levels are associated with an increased cardiovascular risk of atherothrombosis. Furthermore, increased plasma PAI-1 levels are associated with dyslipidemia, hyperinsulinemia and hypertension. This association between PAI-1 and metabolic components of the Metabolic Syndrome could explain the predisposition of insulin resistant patients to atherothrombosis. Recent studies have suggested that visceral adipose tissue might be the link between elevated plasma PAI-1 and insulin resistance in the Metabolic Syndrome. Indeed, visceral adipose tissue was proposed as a potentially important source of PAI-1 in humans. However, in light of recent studies, visceral adipose tissue appears to be involved in the increase of plasma PAI-1 via the metabolic disorders usually associated with central obesity, rather than directly. High plasma PAI-1 levels are undoubtedly related to insulin resistance, and the mechanisms which could explain such an increase in the Metabolic Syndrome appear to be multi-factorial and remain to be elucidated. These mechanisms may involve several metabolic disorders such as hyperinsulinemia, dyslipidemia, impaired glucose tolerance and hypertension, which would favor PAI-1 synthesis and release from different cell types.

Infantile obesity: a situation of atherothrombotic risk?

Obesity is a major risk factor for cardiovascular disease frequently associated with hypertension, dyslipidemia, and diabetes. In recent years, alterations in the hemostatic system have been added to these dysfunctions. We analyzed some of these alterations in coagulation and fibrinolysis in obese children (6 to 9 years old) of both sexes. We studied 61 obese children (mean body mass index [BMI], 22.35 kg/m2; 95% confidence interval [CI], 21.82 to 22.87) and 70 non-obese children (mean BMI, 16.58 kg/m2; 95% CI, 16.24 to 16.93) as a control group. The obese subjects presented significantly elevated values for insulin (P < .001), tissue-plasminogen activator ([t-PA] P < .001), plasminogen activator inhibitor-1 ([PAI-1] P < .001), and fibrinogen (P < .001) with respect to the control group. We found no significant differences in the concentration of glucose and fragment 1 + 2 of prothrombin (F1 + 2). In the obese subjects, insulin, PAI-1, and F1 + 2 were positively correlated with the BMI. On the other hand, t-PA was correlated with insulin and PAI-1 but not with the BMI. Therefore, in the obese children, there was an increment of the risk factors for cardiovascular disease.

Improvement by the insulin-sensitizing agent, troglitazone, of abnormal fibrinolysis in type 2 diabetes mellitus

This study evaluated abnormal fibrinolysis in diabetic patients in terms of the pathophysiological significance and reversibility by oral hypoglycemic agents. Forty-seven patients with type 2 diabetes mellitus were randomly treated for 4 weeks with glibenclamide (n = 23) or troglitazone (n = 24). Before and after treatment, glycemic control, steady-state plasma glucose and insulin (SSPG and SSPI, respectively), and markers of fibrinolysis (tissue plasminogen activator [tPA] and plasminogen activator inhibitor-1 [PAI-1]) were analyzed in each patient. Pretreatment plasma PAI-1 in diabetic patients, but not tPA, was well correlated with the severity of retinopathy assessed by the fluorescence technique. Four weeks of treatment with troglitazone significantly decreased hemoglobin A1c (HbA1c), SSPG, and PAI-1 without an alteration of tPA. The troglitazone-induced decrease in plasma PAI-1 (50.3 v28.8 micromol/L; P < .05) was correlated with HbA1c (8.80% v7.21%, r = .539, P < .01) and SSPG (16.2 v 8.97 mmol/L, r = .562, P < .01) but not with SSPI. In contrast, treatment with glibenclamide for 4 weeks also reduced the HbA1c titer to almost the same extent as troglitazone (1.38% v 1.59%), but did not change the plasma PAI-1 or SSPG titer. These results suggest that an abnormal fibrinolytic state, especially overproduction of PAI-1, may be a pathogenic factor in the development of diabetic complications such as retinopathy, which may be improved by correction of the insulin resistance with troglitazone.

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.

Differential regulation by troglitazone of plasminogen activator inhibitor type 1 in human hepatic and vascular cells

Troglitazone, a novel oral insulin sensitizer, normalizes increased plasma activity of plasminogen activator inhibitor type 1 (PAI-1) in hyperinsulinemic patients such as women with polycystic ovary syndrome and patients with type 2 diabetes mellitus. However, underlying mechanisms have not yet been fully elucidated. Human hepatic and vascular cells, the main sources of circulating PAI-1, were studied in cell culture. In human hepatic cells, PAI-1 accumulated in conditioned medium by 23% within 24 h after exposure to 3 microg/mL troglitazone (P = 0.001). The accumulation depended on the concentration of troglitazone, but not that of insulin (known to stimulate PAI-1 synthesis). By contrast, in human aortic smooth muscle cells, 3 microg/mL troglitazone decreased basal PAI-1 expression by 23% (P = 0.037) and decreased transforming growth factor-beta-induced expression by 34% (P = 0.026). Concomitant insulin had no effect. Tissue-type plasminogen activator was decreased by 38% (P = 0.002). In human endothelial cells, PAI-1 was diminished by 32% (P < 0.001), whereas tissue-type plasminogen activator was unaffected. The results suggest that the reduction in plasma activity of PAI-1 induced by troglitazone in patients may reflect both directly mediated diminution of its elaboration from vessel walls and indirectly mediated reduction of its hepatic synthesis secondary to attenuation of hyperinsulinemia (known to increase the hepatic synthesis of PAI-1).

Dietary treatment of thrombogenic disorders related to the metabolic syndrome

The increased risk of coronary heart disease associated with the metabolic syndrome may be partially explained by prothrombotic deviations of the haemostatic system. Individuals with insulin resistance, dyslipidaemia and obesity are characterized by elevated plasma fibrinogen and factor VII coagulant activity levels and raised concentrations of plasminogen-activator inhibitor, the main inhibitor of endogenous fibrinolysis. These haemostatic abnormalities may be corrected with dietary treatment of the underlying clinical disorder. Dietary trials of diseased and healthy volunteers suggest that the optimal antithrombotic diet is a low-fat diet with a high content of foods rich in complex carbohydrates and dietary fibre. The dietary fatty acid composition has a profound effect on blood lipids, but seems of minor importance for the haemostatic system.

Thrombophilia in Patients with Hypertriglyceridemia

Objectives: To investigate a possible relationship between hypertriglyceridemia and the coagulation system, a Cardiovascular Risk Factor Two-township Study was conducted in Taiwan. Design: A case-control study. This longitudinal, prospective study focused on the evolution of cardiovascular disease risk factors with emphasis on haemostatic factors. Subjects: Hypertriglyceridemic subjects (triglyceride <2.26 mmoll+1, n = 327) and age-matched normal controls from a population screening program. Main outcome measures: Haemostatic parameters measured in this study included prothrombin time (PT), activated partial thromboplastin time (aPTT), fibrinogen, factors VIIc and VIIIc, and antithrombin-III and plasminogen levels. Results: In our male hypertriglyceridemic subjects, aPTT was not significantly reduced, while significant elevations of factor VIIIc, factor VIIc, and plasminogen and antithrombin-III levels were noted. In the female hypertriglyceridemic subjects, the elevation of factor VIIc, factor VIIIc, and plasminogen and antithrombin-III levels was highly-significant, whereas aPTT was not significantly reduced. Unexpectedly, the levels of the established coronary risk factor, fibrinogen, did not show a statistically different change. Similar to previous data, our hypertriglyceridemic subjects also presented with hyperinsulinemia, glucose intolerance, upper body obesity, and elevated blood pressure. Conclusions: Despite the fact that in population studies, triglycerides do not consistently appear to be an independent risk factor for coronary heart disease, our data suggest that a pronounced increase in triglycerides warrants aggressive therapy, because this increase may be associated with a hypercoagulable state. This phenomenon contributes another perspective to the study of higher cardiovascular mortality in hypertriglyceridemic subjects.

Epidemiological and clinical studies on insulin resistance and diabetes

In Uppsala, extensive epidemiological and clinical studies on insulin resistance and diabetes have been ongoing for the past 30 years. A prospective cohort study of men born 1920-24, living in Uppsala County, was initiated during 1969-74 (the Uppsala Longitudinal Study of Adult Men, ULSAM). Risk factors for cardiovascular disease were examined in 2,322 men, and re-examinations have been performed every 10 years. At the first follow-up, when the men were 60 years old, insulin resistance was found to be a risk factor for development of hypertension and diabetes. In addition, treatment with antihypertensive medication was an independent risk factor for development of diabetes. These findings resulted in a series of clinical studies on metabolic effects of antihypertensive agents. At the second follow-up, when the men were 70 years old, the development of hypertension and diabetes was once again in focus, but at this time, cross-sectional and prospective studies of other cardiovascular determinants, such as circadian blood pressure pattern, left ventricular geometry and function, muscle morphology, ion status, fibrinolysis and cognitive function, were also performed. The cohort has furthermore been linked to the Swedish census and hospital discharge and cause of death registries, it has been used for studies on relationships between birth weight and cardiovascular disease, and genetic analyses have been performed, taking advantage of the long observation time obtained in this cohort. The cohort is currently being re-examined for the third time, and will hopefully continue to provide valuable information on the epidemiology of diabetes and cardiovascular disease in the future.

Plasma plasminogen activator inhibitor 1, insulin resistance and android obesity

Plasma plasminogen activator inhibitor 1 (PAI-1) levels are elevated in insulin-resistant subjects and are associated with increased cardiovascular risk of atherothrombosis. Strong association between PAI-1 and the metabolic components of the insulin resistance syndrome is found in clinical studies, suggesting that insulin resistance may regulate circulating PAI-1. However, the mechanisms underlying increased PAI-1 levels in such conditions are still poorly understood. Several studies have been carried out specifically in patients with central or android obesity, a major characteristic of the insulin resistance syndrome, and have suggested that visceral adipose tissue may be the major component of the relationship between android obesity and PAI-1. Accordingly, adipose tissue PAI-1 production was found to be elevated in obese human subjects, particularly in visceral adipose tissue. The genetic background for having high PAI-1 levels in several populations have been looked for and its role appeared to be weaker than that of the metabolic condition. High plasma PAI-1 levels are then clearly related to android obesity and insulin resistance, but the mechanisms whereby PAI-1 increases in plasma in these diseases remain to be determined.

Oxidized LDL and lysophosphatidylcholine stimulate plasminogen activator inhibitor-1 expression in vascular smooth muscle cells

Plasminogen activator inhibitor-1 (PAI-1) functions as an important regulator of fibrinolysis by inhibiting both tissue-type and urokinase-type plasminogen activator. PAI-1 is produced by smooth muscle cells (SMCs) in atherosclerotic arteries, but the mechanisms responsible for induction of PAI-1 in SMCs are less well understood. In cultured human aortic SMCs, PAI-1 mRNA expression and protein secretion were increased after incubation with oxidized low-density lipoprotein (LDL) and the lipid peroxidation product lysophosphatidylcholine, whereas the effects of native LDL on PAI-1 production and release were more variable and did not reach statistical significance. The effect of LDL on arterial expression of PAI-1 in vivo was also studied in an animal model. Intravenous injection of human LDL in Sprague-Dawley rats resulted in accumulation of apolipoprotein B in the aorta within 12 hours as assessed by immunohistochemical testing. Epitopes specific for oxidized LDL began to develop in the aorta 12 hours after injection of LDL and peaked at 24 hours; this peak was accompanied by intense expression of PAI-1 immunoreactivity in the media. Also, increased aortic expression of PAI-1 mRNA after LDL injection was detected by using in situ hybridization. The transcription factor activator protein-1, which is known to bind to the promoter of the PAI-1 gene, was activated in the aortic wall 24 hours after LDL injection as assessed by electrophoretic mobility shift assay. Pretreatment of LDL with the antioxidant probucol decreased expression of oxidized LDL and PAI-1 immunoreactivity and activator protein-1 induction in the aorta but did not affect expression of apolipoprotein B immunoreactivity. These findings demonstrate that LDL oxidation enhances secretion of PAI-1 from cultured SMCs and that a similar mechanism may be involved in vascular expression of PAI-1.

Screening for cardiovascular disease. Concepts, conflicts, and consensus

CVD in the United States is prevalent, costly, and disabling. Wherever in the arterial tree atherosclerosis occurs, the process appears to begin in youth, to develop under the influence of the same risk factors, and to be amenable to the same interventions. The relationship between CVD and its associated risk factors is continuous, is graded, and extends below thresholds previously defined as normal. This observation, in turn, is based on an appreciation that in our society, the gap between normal and optimal can be considerable. CVD is a multifactorial process, often related to modifiable lifestyle choices; we focus on any single risk factor to the exclusion of others puts patients in danger. Because risk factors rarely occur in isolation, risk assessment must be as multifactorial as the underlying disease process. By understanding differences between risk factors in terms of the impact of their modification on the underlying disease, targeted interventions become possible that are tailored to the likelihood of an individual patient acquiring CVD. To change the overall prevalence of an epidemic disease such as CVD, however, such a high-risk approach must be applied in concert with a population strategy that seeks to effect smaller degrees of change in the large segment of society that may be at only moderate risk but--because of their great numbers--bears most of the morbidity and mortality of CVD. Finally, despite the remarkable progress that has been made in our understanding of the pathophysiology of CVD and the effectiveness of risk factor modification, significant gaps remain between knowledge and behavior. Fewer than 50% of diabetics are even aware that they have the disease. Only a third of those whose lipid levels qualify them for treatment receive intervention of any kind, including dietary advice. Only 27% of hypertensives have their blood pressure adequately controlled. The potential impact of more vigorous screening practices in the primary care setting on the health of individuals and communities cannot be overstated.

Comparison of plasminogen activator inhibitor-1 concentration in insulin-resistant versus insulin-sensitive healthy women

The primary goal of this investigation was to see whether plasminogen activator inhibitor-1 (PAI-1) concentrations varied as a function of differences in insulin-mediated glucose disposal in 2 groups of healthy women matched for every other variable that might play a role in regulation of PAI-1. For this purpose, we recruited 32 healthy women, divided on the basis of their steady-state plasma glucose (SSPG) concentrations during the insulin suppression test into an insulin-resistant (SSPG=216+/-12 mg/dL, n=16) and an insulin-sensitive (94+/-6 mg/dL, n=16) group. PAI-1 antigen concentrations were significantly higher (26+/-4 versus 14+/-3 ng/mL, P<0.02) in the insulin-resistant group. In addition, fasting plasma insulin (18+/-3 versus 11+/-2 microU/mL, P<0.02) and triglyceride (160+/-19 versus 93+/-10 mg/dL, P<0.001) concentrations were higher in the insulin-resistant individuals, whereas HDL concentrations were lower (44+/-3 versus 58+/-3 mg/dL, P<0.005). However, the 2 groups were essentially identical in terms of age, menopausal status, hormone replacement therapy, body mass index (BMI), ratio of waist-to-hip girth, and blood pressure. When the experimental population was considered as 1 group, there were statistically significant correlations between PAI-1 antigen and the following variables: adjusting for differences in age and BMI, SSPG (r=0.56, P<0.001); triglyceride (r=0.39, P<0.05); and HDL cholesterol (r=-0. 65, P<0.001) concentrations. Finally, multiple regression analysis revealed the major determinants of PAI-1 to be insulin resistance, or insulin concentration, and HDL cholesterol. These results: 1) demonstrate that PAI-1 concentrations are higher in healthy, insulin-resistant women as compared with insulin-sensitive individuals, independent of differences in BMI or ratio of waist-to-hip girth; and 2) provide another mechanism by which insulin-resistant individuals are at increased thrombotic cardiovascular risk.

Local insulin infusion stimulates expression of plasminogen activator inhibitor-1 and tissue-type plasminogen activator in normal subjects

PURPOSE

Plasma levels of plasminogen activator inhibitor-1 are increased in obesity, hypertension, and diabetes. Their correlation with insulin levels supports the hypothesis that hypofibrinolysis may affect the development of atherosclerotic complications in patients with insulin resistance. To investigate the effect of insulin on fibrinolysis, we evaluated levels of plasminogen activator inhibitor-1 (PAI-1) and tissue plasminogen activator (tPA) antigens during insulin infusion in the forearm vascular beds of 8 healthy subjects.

MATERIALS AND METHODS

Insulin was infused in the brachial artery of each subject to raise local venous concentrations to approximately 100 microU/mL. Blood samples were obtained from the brachial artery and vein at baseline, after 30, 60, 90, and 120 minutes of infusion, and 30 minutes after the end of the infusion.

RESULTS

Following intra-arterial infusion of insulin, forearm blood flow (mean +/- SD) increased progressively from 2.7 +/- 0.6 to 4.0 +/- 0.6 mL/dL/min (P <0.01) and did not return to baseline after the end of the infusion. Plasminogen activator inhibitor-1 balance increased (345 +/- 160 versus 8 +/- 152 fmol/dL/min, P <0.02) at 60 minutes, reaching baseline levels after the end of the infusion. After 90 minutes, tPA balance increased (40 +/- 26 versus 7 +/- 29 fmol/dL/min, P <0.01) with a profile similar to forearm blood flow.

CONCLUSIONS

Local hyperinsulinemia induces regional vasodilation and expression of PAI-1 and tPA antigens. An alteration of this physiological process could be involved in the development of hypofibrinolysis and atherosclerosis in states of insulin resistance.

Renal allograft thrombosis: can thrombophilia explain the inexplicable?

Renal allograft thrombosis remains a preventable cause of early allograft thrombosis. It should not be considered simply an unpredictable and poorly understood consequence of surgery. Extrapolated data from the general population and early data from renal patients supports the concept that the interplay of non-inherited hypercoagulability of renal disease with inherited thrombophilia, and the altered environmental milieu of transplantation predisposes to thrombosis (summarized in Figure 2). We should not accept the inevitability of a constant attrition of grafts to thrombosis and need to continue to identify risk factors and confirm appropriate screening and interventions for its prevention, almost certainly requiring collaborative multicentre trials. In the future, just as we now expand the specificity of HLA gene typing with molecular biology, genotyping for recognized thrombophilia genes in patients at risk will expand our ability to recognize and prevent thrombosis with targeted interventions drawn from the increasing array of anticoagulants now available. The contribution of thrombophilia to non-immune mechanisms of chronic allograft loss is also a potentially important but neglected area of research.

Genetic determinants of arterial thrombosis

This chapter describes examples of genetic variation involved in the function or regulation of a number of haemostatic proteins involved in the thrombotic process. In each case, the data suggest associations between genotype and disease and, particularly in the case of fibrinogen, PAI-1, Factor VII and Factor XIII, there is interaction between genotype and environment in determination of the relevant plasma level, providing a possible explanation for the differential response of individuals to their environment.

Rapid, Homogeneous Genotyping of the 4G/5G Polymorphism in the Promoter Region of the PAI1 Gene by Fluorescence Resonance Energy Transfer and Probe Melting Curves

Background: Many studies have convincingly shown that survivors of myocardial infarction have impaired fibrinolytic activity because of increased concentrations of plasma plasminogen activator inhibitor-1 (PAI-1). A single guanosine insertion/deletion polymorphism in the promoter region of the PAI1 gene, commonly called 4G/5G, has been shown to be associated with plasma PAI-1 activity. Our aim was to develop and validate a homogeneous assay for rapid genotyping of the 4G/5G polymorphism.

Methods: In this report we present a single-tube method for genotyping of the 4G/5G polymorphism that combines both rapid-cycle PCR with real-time monitoring of the amplification process and generation of allele-specific fluorescent probe melting profiles on the LightCyclerTM. Two fluorescently labeled hybridization probes recognizing adjacent sequences in the amplicon were present in the reaction mixture. The shorter detection probe spanned the polymorphic site, perfectly matching the 5G allele. After annealing, the fluorophores were in resonance energy transfer, providing real-time monitoring of the amplification process. At the completion of the PCR, fluorescence was monitored as the temperature increased through the Tm of the probe/product duplex, and a characteristic melting profile for each genotype was obtained.

Results: With this method, 32 samples were genotyped within 30 min without the need of any post-PCR sample manipulation. The genotypes of 100 DNA samples determined with the LightCycler were identical to those obtained with conventional PCR and restriction fragment length analysis.

Conclusion: The genotyping of the 4G/5G polymorphism with the LightCycler is a rapid, reliable method that is suitable for typing both small and large numbers of samples.

Clinical implications of elevated PAI-1 revisited: multiple arterial thrombosis in a patient with essential thrombocythemia and elevated plasminogen activator inhibitor-1 (PAI-1) levels: a case report and review of the literature

Plasminogen activator inhibitor (PAI-1), a member of the serine protein family, is the most active in vivo inhibitor of fibrinolysis induced by plasminogen, tissue plasminogen activator (tPA), and urokinase type plasminogen activator (uPA). While the association between elevated PAI-1 and thrombogenesis has been well studied for several disease processes, including coronary disease, postoperative deep vein thrombosis (DVT), myocardial infarction, malignancy, and diabetes, few studies have concentrated on the correlation between elevated PAI-1 levels and thrombogenesis in patients with myeloproliferative disorders. Essential thrombocythemia (ET), a chronic myeloproliferative disorder, characterized by the overproduction of poorly functioning platelets, is associated with both thrombotic and hemorrhagic life-threatening complications. Although the events resulting in thrombogenesis in such patients may be multifactorial in nature, an association between elevated PAI-1 levels and thrombus formation has been proposed. Herein we present a patient diagnosed with ET complicated by multiple episodes of arterial thrombosis. Elevations in PAI-1 levels were documented repeatedly. The role of elevated PAI-1 when associated with other disease processes is also discussed.

Fibrinolytic function and coronary risk

Plasminogen activation potential in the blood is controlled by an equilibrium between plasminogen activators, mainly tissue-type plasminogen activator (t-PA), and inhibitors, mainly plasminogen activator inhibitor (PAI)-1. In cardiovascular practice, imbalance of this fibrinolytic potential is encountered primarily in the insulin-resistance syndrome. This syndrome leads to increased plasma PAI-1 and t-PA antigen levels (reflecting inactive t-PA/PAI-1 complexes) with a consequent decrease in fibrinolytic activity. Increased plasma PAI-1 and t-PA antigen both are predictive of myocardial infarction. The prognostic value of PAI-1 disappears after adjustments for insulin resistance markers, whereas the prognostic value of t-PA antigen disappears after simultaneous adjustments for insulin resistance and inflammation markers, suggesting an additive role of inflammation in inducing plasma fibrinolytic markers. Recently the production of PAI-1 by adipose tissue, in particular by tissue from the omentum, has been shown. PAI-1 produced in this way could be an important contributor to the elevated plasma PAI-1 levels observed in insulin-resistant patients. These results support the notion that PAI-1 may be a link between obesity, insulin resistance, and cardiovascular disease. Genetic control of PAI-1 expression has also been shown, involving a -675 4G/5G polymorphism, the 4G/4G genotype being associated with higher plasma PAI-1 levels; its proper influence on the development of myocardial infarction is still debated.

Improved fibrinolysis by intense lifestyle intervention. A randomized trial in subjects with impaired glucose tolerance

OBJECTIVE

To assess the effects of lifestyle intervention on cardiovascular risk factors in general and especially on fibrinolysis.

DESIGN

Randomized clinical study.

SUBJECTS

A total of 186 subjects with impaired glucose tolerance and obesity.

INTERVENTIONS

The intervention programme included a low-fat, high-fibre diet and regular physical exercise. Half of the participants (n = 93) took part in a one-month learning and training session using different behavioural modification techniques and conducted in a full-board wellness centre (intense intervention group). The other half (n = 93) was randomized a one-hour counselling session with a specially trained nurse (usual care group). Follow-up was carried out after 12 months.

MAIN OUTCOME MEASURES

Body weight, oxygen consumption, plasminogen activator inhibitor type 1 (PAI-1) activity, tissue plasminogen activator (tPA) antigen, fibrinogen and fasting plasma insulin measured at the start of the programme and at follow-up after 1 year.

RESULTS

The intense intervention group had a mean weight decline by 1 year of 5.4 kg compared to 0.5 kg in the usual care group. Oxygen consumption in the intense group increased 10% vs. a 1% decline in the usual care group. In the intense group, PAI-1 activity decreased 31% (-10.1 U mL(-1)), which was significantly more than in the usual care group (12%; -3.0 U mL(-1)). The corresponding reductions in tPA antigen were 14% (-1.65 microg L(-1)) and 6% (-0.69 microg L(-1)).

CONCLUSIONS

The present randomized study shows that an intense lifestyle programme has sustained beneficial effects on fibrinolysis.

Beneficial effects of conversion from cyclosporine to azathioprine on fibrinolysis in renal transplant recipients

Cyclosporin A (CsA) has been implicated as one of the factors contributing to the high cardiovascular morbidity and mortality after renal transplantation. This may be mediated by either a high prevalence of conventional risk factors for atherosclerosis, such as hypertension, hypercholesterolemia, and diabetes mellitus, or by impairment of the fibrinolytic activity evoked by CsA, possibly through interference with prostanoid metabolism. We therefore assessed the impact of conversion of CsA to azathioprine immunosuppressive treatment on parameters of fibrinolytic activity and plasma concentration of the prostanoids prostaglandin E2 and thromboxane B2 in 18 stable renal transplant recipients. During CsA, mean arterial pressure and serum creatinine were significantly higher than during azathioprine (116+/-15 mm Hg versus 106+/-13 mm Hg, P=0.0003; and 147+/-34 micromol/L versus 127+/-35 micromol/L, P=0.002; mean+/-SD). On conversion, the plasma tissue plasminogen activator activity increased from 1.2 (1.1 to 1.7; median, 95% CI) to 1.8 (1.6 to 2.0) IU/mL (P=0.011), without a significant change of the plasminogen activator antigen concentration. This was associated with a substantial decrease in plasminogen activator inhibitor-1 activity from 10.4 (8.5 to 16.7) to 6.4 (5.6 to 9.2) IU/mL (P=0.009). Furthermore, plasma levels of prostaglandin E2 and thromboxane B2 markedly decreased (from 9.7 [7.4 to 12.9] to 4.6 [4.3 to 8.1] pg/mL, P=0.0006; and from 106.1 [91.7 to 214.2] to 70.2 [50.3 to 85.6] pg/mL, P=0.002, respectively). During CsA, but not azathioprine, plasma tissue plasminogen activator antigen and plasminogen activator inhibitor-1 levels correlated significantly with prostaglandin E2 (r=0.53, P=0.02; and r=0.60, P=0.008, respectively), and thromboxane B2 (r=0.75, P=0.0001; and r=0.77, P=0.0001, respectively) levels. In conclusion, CsA induced substantial impairment of fibrinolytic activity, which recovered after conversion to azathioprine. The impaired fibrinolysis observed during CsA treatment may be caused by modulation of eicosanoid production or metabolism in vascular endothelial cells and possibly contributes to the high incidence of cardiovascular disease after kidney transplantation.

Effects of fibrate compounds on expression of plasminogen activator inhibitor-1 by cultured endothelial cells

The consistent positive correlation between triglyceride and plasminogen activator inhibitor-1 (PAI-1) levels in plasma and the fact that very low density lipoprotein (VLDL) induces secretion of PAI-1 from cultured human umbilical vein endothelial cells (HUVECs) and human hepatoblastoma cells have raised the question of whether fibrate treatment, the main effect of which is a profound lowering of plasma concentrations of VLDL, might improve fibrinolytic function by reducing the plasma levels of PAI-1. However, the findings of controlled clinical trials using various fibrate compounds have been discrepant. ECs express PAI-1 under normal conditions in humans. We therefore examined the effects of several fibrate compounds on PAI-1 expression and secretion by cultured HUVECs and the HUVEC-derived cell line EA.hy926. All fibrate compounds examined had significant effects on PAI-1 gene transcription in the EA.hy926 cells. Low concentrations of clofibric acid and bezafibrate increased PAI-1 transcription and secretion, whereas Wy-14643 increased PAI-1 synthesis in a dose-dependent way. In contrast, both fenofibric acid and gemfibrozil markedly decreased PAI-1 transcription and secretion from HUVECs and EA.hy926 cells. Thus, stimulation of the transcriptional activity of the PAI-1 gene by some fibrates is linked to increased secretion of PAI-1 protein by the cells, whereas the opposite effects occur with other fibrate compounds. Whether the different effects on PAI-1 transcription and secretion by ECs in vitro also reflect differences in treatment effects on the regulation of plasma PAI-1 activity in vivo will have to be determined in larger-scale, controlled clinical trials.

Impact of adipose tissue on plasma plasminogen activator inhibitor-1 in dieting obese women

The increased incidence of cardiovascular diseases in obese subjects could be partially attributed to impaired fibrinolysis due to elevated plasma levels of tissue plasminogen activator inhibitor 1 (PAI-1). The associations between changes in plasma PAI-1, metabolic variables, and adipose tissue during weight loss and regain were studied in 52 healthy, premenopausal, obese women participating in a weight reduction program with a hypocaloric diet. PAI-1, insulin, triglyceride, leptin, and adipsin levels were determined at entry, after the first week, after completion of the program, and after 5 months of follow-up. In the 33 obese women who completed the program, decreases in PAI-1 antigen (-54%), PAI activity (-74%), and leptin (-51%), but not of adipsin, were observed. Changes in PAI-1 were associated with changes in body mass index (BMI), body fat, leptin, and insulin. The decreased level of PAI-1 remained low after follow-up in the 14 women who maintained their reduced weight but increased in the 16 women who regained weight. This increase in PAI-1 was correlated with an increase in body fat and leptin. On multivariate analysis, BMI was the major determinant of PAI-1 level. In conclusion, during weight reduction with a hypocaloric diet, the decrease in PAI-1 is more closely related to changes in adipose tissue than to changes in metabolic variables, suggesting a significant role for adipose tissue in regulating plasma levels of PAI-1.

Hyperinsulinemia and Related Atherosclerotic Risk Factors in the Population at Cardiovascular Risk: A Community-based Study

Background: A population-based study was conducted in Taiwan to investigate the prevalence of insulin resistance and high serum insulin concentrations and their relationships with potential atherosclerotic risk factors.

Methods: We studied 2165 subjects, ages &gt;35, from a community cohort.

Results: The distributions of fasting insulin were skewed to the right, with higher concentrations in women than in men. As age increased, insulin increased in women, but decreased in men. As fasting insulin concentrations increased, postloading insulin, glucose, blood pressure, body mass index, waist-to-hip ratio, total cholesterol, triglycerides, LDL-cholesterol, apoprotein B, plasminogen activator inhibitor 1, tissue plasminogen activator, and fibrinogen increased, but lipoprotein(a), HDL-cholesterol, and apoprotein A1 decreased. Multiple logistic regression showed that obesity, high LDL-cholesterol, and low HDL-cholesterol were significant predictors of hyperinsulinemic status.

Conclusion: The study subjects with insulin resistance syndrome and related risk factors may be at risk for atherosclerosis, thrombosis, and other coronary heart diseases.

Hypertriglyceridemia, insulin resistance, and the metabolic syndrome

The metabolic syndrome consists of a cluster of metabolic disorders, many of which promote the development of atherosclerosis and increase the risk of cardiovascular disease events. Insulin resistance may lie at the heart of the metabolic syndrome. Elevated serum triglycerides commonly associate with insulin resistance and represent a valuable clinical marker of the metabolic syndrome. Abdominal obesity is a clinical marker for insulin resistance. The metabolic syndrome manifests 4 categories of abnormality: atherogenic dyslipidemia (elevated triglycerides, increased small low-density lipoproteins, and decreased high-density lipoproteins), increased blood pressure, elevated plasma glucose, and a prothrombotic state. Various therapeutic approaches for the patient with the metabolic syndrome should be implemented to decrease the risk of cardiovascular disease events. These interventions include decreasing obesity, increasing physical activity, and managing dyslipidemia; the latter may require the use of pharmacotherapy with cholesterol-lowering and triglyceride-lowering drugs.

PAI-1 produced ex vivo by human adipose tissue is relevant to PAI-1 blood level

Human adipose tissue has been shown to produce plasminogen activator inhibitor type 1 (PAI-1). However, the importance of adipose tissue in the regulation of the PAI-1 plasma level is not known. The aim of this study was to investigate the relation between the production of PAI-1 by adipose tissue, plasma PAI-1 level, and variables related to the insulin resistance state. The link between the production of PAI-1 inducers such as tumor necrosis factor-alpha and transforming growth factor-beta and the production of PAI-1 by adipose tissue was also evaluated. Blood samples were obtained as soon as possible to the induction of anesthesia from 30 patients undergoing elective abdominoplasty. PAI-1 antigen levels measured in conditioned media after a 19-hour incubation period of adipose tissue explants were significantly correlated with plasma PAI-1 antigen levels (r=0.54, P=0.004) and with systemic lipid parameters such as triglycerides and high density lipoprotein cholesterol (r=0. 46, P=0.014; r=-0.50, P=0.01, respectively) but not with insulinemia and body mass index. PAI-1 production by adipose tissue was correlated with those of TNF-alpha (r=0.5, P=0.01) and TGF-beta (r=0. 53, P=0.007). These results emphasize the role of adipose tissue in determining plasma levels of PAI-1, with a local contribution of TNF-alpha and TGF-beta in PAI-1 production by adipose tissue.

Is leptin concentration associated with the insulin resistance syndrome in nondiabetic men?

OBJECTIVE

Insulin resistance has been strongly associated with cardiovascular risk. Recently, leptin, a hormone that regulates appetite, has been associated with both obesity and insulin resistance. However, the possible relation of leptin to the insulin resistance syndrome has been controversial.

RESEARCH METHODS AND PROCEDURES

To explore this issue, we examined the relation of leptin to blood pressure, lipid levels, low density lipoprotein (LDL) size, and glucose levels in 87 normoglycemic men.

RESULTS

Leptin levels were significantly correlated with body mass index (BMI) (r = 0.494), fasting insulin (r = 0.576), whole-body glucose disposal rate (GDR) (r = -0.566), fasting glucose (r = 0.510) total triglycerides (r = 0.294), apolipoprotein B (r = 0.223), systolic blood pressure (r = 0.223), and LDL size (r = -0.244). After adjustment for BMI and GDR, leptin levels remained significantly correlated with fasting insulin, fasting glucose, triglyceride, apolipoprotein B, and systolic blood pressure. Leptin levels were also correlated with the number of metabolic risk factors (dyslipidemia, systolic blood pressure, and fasting glucose).

DISCUSSION

We conclude that leptin concentrations may be associated with several cardiovascular risk factors related to insulin resistance syndrome. These associations are only partly explained by leptin's relationship with BMI and GDR.

Fibrinolytic activation markers predict myocardial infarction in the elderly. The Cardiovascular Health Study

Coagulation factor levels predict arterial thrombosis in epidemiological studies, but studies of older persons are needed. We studied 3 plasma antigenic markers of fibrinolysis, viz, plasminogen activator inhibitor-1 (PAI-1), fibrin fragment D-dimer, and plasmin-antiplasmin complex (PAP) for the prediction of arterial thrombosis in healthy elderly persons over age 65. The study was a nested case-control study in the Cardiovascular Health Study cohort of 5201 men and women >/=65 years of age who were enrolled from 1989 to 1990. Cases were 146 participants without baseline clinical vascular disease who developed myocardial infarction, angina, or coronary death during a follow-up of 2.4 years. Controls remained free of cardiovascular events and were matched 1:1 to cases with respect to sex, duration of follow-up, and baseline subclinical vascular disease status. With increasing quartile of D-dimer and PAP levels but not of PAI-1, there was an independent increased risk of myocardial infarction or coronary death, but not of angina. The relative risk for D-dimer above versus below the median value (>/=120 microg/L) was 2.5 (95% confidence interval, 1.1 to 5.9) and for PAP above the median (>/=5.25 nmol/L), 3.1 (1.3 to 7.7). Risks were independent of C-reactive protein and fibrinogen concentrations. There were no differences in risk by sex or presence of baseline subclinical disease. D-dimer and PAP, but not PAI-1, predicted future myocardial infarction in men and women over age 65. Relationships were independent of other risk factors, including inflammation markers. Results indicate a major role for these markers in identifying a high risk of arterial disease in this age group.

Relationship of plasmin generation to cardiovascular disease risk factors in elderly men and women

Plasmin-alpha2-antiplasmin complex (PAP) marks plasmin generation and fibrinolytic balance. We recently observed that elevated levels of PAP predict acute myocardial infarction in the elderly, yet little is known about the correlates of PAP. We measured PAP in 800 elderly subjects who were free of clinical cardiovascular disease in 2 cohort studies: the Cardiovascular Health Study and the Honolulu Heart Program. Median PAP levels did not differ between the Cardiovascular Health Study (6.05+/-1.46 nmol/L) and the Honolulu Heart Program (6.11+/-1.44 nmol/L), and correlates of PAP were similar in both cohorts. In CHS, PAP levels increased with age (r=0. 30), procoagulant factors (eg, factor VIIc, r=0.15), thrombin activity (prothrombin fragment F1+2, r=0.29), and inflammation-sensitive proteins (eg, fibrinogen, r=0.44; factor VIIIc, r=0.37). PAP was associated with increased atherosclerosis as measured by the ankle-arm index (AAI) (P for trend, </=0.001). PAP was negatively related to factors associated with the insulin resistance syndrome (IRS) (eg, fasting insulin, r=-0.26; body mass index, r=-0.26), possibly reflecting an association with plasminogen activator inhibitor-1 (r=-0.29). Although our study did not have sufficient power to detect a significant interaction, PAP and AAI appeared to be more weakly associated in subjects with more manifestations of the IRS: PAP appeared more strongly associated with AAI in the subgroup with 0 or 1 metabolic disorders (P</=0.001; slope estimate, -0.14) compared with the subgroup with 2 or more metabolic disorders (P=0.10; slope estimate, -0.08) and in those with non-insulin-dependent diabetes mellitus (P=0.46; slope estimate, -0.04). Although PAP reflects reactive fibrinolysis and is associated with subclinical atherosclerosis, this relationship may be weaker in populations with characteristics of the IRS, possibly reflecting the inhibitory effects of plasminogen activator inhibitor-1 on PAP. Decreased fibrinolysis in the presence of subclinical disease in subjects with hyperinsulinemia or glucose intolerance is consistent with the premise that depressed plasmin generation may enhance the progression of atherosclerosis in these people.

Relative contribution of insulin and its precursors to fibrinogen and PAI-1 in a large population with different states of glucose tolerance. The Insulin Resistance Atherosclerosis Study (IRAS)

Hyperinsulinemia is associated with the development of coronary heart disease. However, the underlying mechanisms are still poorly understood. Hypercoagulability and impaired fibrinolysis are possible candidates linking hyperinsulinism with atherosclerotic disease, and it has been suggested that proinsulin rather than insulin is the crucial pathophysiological agent. The aim of this study was to investigate the relationship of insulin and its precursors to markers of coagulation and fibrinolysis in a large triethnic population. A strong and independent relationship between plasminogen activator inhibitor-1 (PAI-1) antigen and insulin and its precursors (proinsulin, 32-33 split proinsulin) was found consistently across varying states of glucose tolerance (PAI-1 versus fasting insulin [proinsulin], r=0.38 [r=0.34] in normal glucose tolerance; r=0.42 [r=0.43] in impaired glucose tolerance; and r=0.38 [r=0.26] in type 2 diabetes; all P<0.001). The relationship remained highly significant even after accounting for insulin sensitivity as measured by a frequently sampled intravenous glucose tolerance test. In a stepwise multiple regression model after adjusting for age, sex, ethnicity, and clinic, both insulin and its precursors were significantly associated with PAI-1 levels. The relationship between fibrinogen and insulin and its precursors was significant in the overall population (r=0.20 for insulin and proinsulin; each P<0.001) but showed a more inconsistent pattern in subgroup analysis and after adjustments for demographic and metabolic variables. Stepwise multiple regression analysis showed that proinsulin (split products) but not fasting insulin significantly contributed to fibrinogen levels after adjustment for age, sex, clinic, and ethnicity. Decreased insulin sensitivity was independently associated with higher PAI-1 and fibrinogen levels. In summary, we were able to demonstrate an independent relationship of 2 crucial factors of hemostasis, fibrinogen and PAI-1, to insulin and its precursors. These findings may have important clinical implications in the risk assessment and prevention of macrovascular disease, not only in patients with overt diabetes but also in nondiabetic subjects who are hyperinsulinemic.

Low-density lipoprotein particle size is inversely related to plasminogen activator inhibitor-1 levels. The Insulin Resistance Atherosclerosis Study

High levels of plasminogen activator inhibitor-1 (PAI-1) and preponderance of small dense low-density lipoproteins (LDL) have both been associated with atherosclerotic disease and with the insulin resistance syndrome (IRS). In vitro studies have shown a stimulatory effect of various lipoproteins on PAI-1 release from different cells, including endothelial cells and adipocytes. The authors sought to investigate the relation of PAI-1 to LDL particle size in a large tri-ethnic population (n=1549) across different states of glucose tolerance. LDL size was determined by gradient gel electrophoresis, and PAI-1 was measured by a 2-site immunoassay, sensitive to free PAI-1. PAI-1 was inversely related to LDL size in the overall population (r=-0.21, P<0.0001), independent of gender and ethnicity. However, the authors found a significant interaction with glucose tolerance status (P=0.035). In univariate analysis, the association between PAI-1 and LDL size was most pronounced in subjects with normal glucose tolerance (NGT, r=-0.22, P<0.0001) and weaker in impaired glucose tolerance (IGT, r=-0.12, P=0.03) and type-2 diabetes (r=-0.10, P=0.02). After adjustment for demographic variables and metabolic variables known to influence PAI-1 levels (triglyceride and insulin sensitivity), a significant inverse relation of LDL size to PAI-1 levels was only present in NGT (P=0. 023). In subjects with IGT or overt diabetes, who usually have elevated PAI-1 levels, additional factors other than LDL size seem to contribute more importantly to PAI-1 levels. The demonstrated inverse relation of LDL size and PAI-1 levels provides one possible explanation for the atherogeneity of small dense LDL particles.

From preadipocyte to adipocyte: differentiation-directed signals of insulin from the cell surface to the nucleus

An alarming rise in obesity, and the accompanying threat of type 2 diabetes mellitus and cardiovascular disease, have attracted worldwide attention. The pathogenic mechanism(s) underlying obesity remains obscure. However, new cellular and molecular insights about the development of adipose tissue, with respect to adipocyte number (hyperplasia) and size (hypertrophy), are occurring at a rapid pace. Specialized fibroblasts (preadipocytes) committed to the adipocyte lineage are present throughout life. Primary cell culture systems and immortalized cell line models of preadipocytes have advanced the study of adipocyte differentiation (adipogenesis). Differentiation-inducing cues are able to trigger a complex network of intracellular signaling pathways in the preadipocyte, allowing signals from cell-surface receptors to reach nuclear transcription factors that regulate the genetic program of adipocyte differentiation. The extracellular matrix environment of the preadipocyte, known to modulate adipogenesis, may act by altering some of these signaling events.

Genotype-specific transcriptional regulation of PAI-1 gene by insulin, hypertriglyceridemic VLDL, and Lp(a) in transfected, cultured human endothelial cells

Plasminogen activator inhibitor-1 (PAI-1) has been shown to be an independent risk factor for coronary artery disease. Variations in plasma PAI-1 levels have been attributed to variations in the PAI-1 gene, and associations between PAI-1 levels and PAI-1 genotypes suggest that PAI-1 expression may be regulated in a genotype-specific manner by insulin, hypertriglyceridemic (HTG) very low density lipoprotein (VLDL), or lipoprotein(a) [Lp(a)]. Polymerase chain reaction-amplified 1106-bp fragments of the promoter of the 1/1 and 2/2 PAI-1 genotypes were sequenced and showed 5 regions of small nucleotide differences in the 1/1 versus 2/2 PAI-1 promoters that consistently occurred with high frequency. These fragments were ligated into the luciferase reporter gene, and 1/1 and 2/2 PAI-1 genotype human umbilical vein endothelial cell (HUVEC) cultures were transiently transfected with their respective p1PAI110/luc and p2PAI110/luc constructs and vice versa. Insulin induced an approximately 12- to 16-fold increase in luciferase activity in both the 1/1 and 2/2 PAI-1 genotype HUVEC cultures transfected with the p1PAI110/luc construct. HTG-VLDL and Lp(a) induced luciferase activity by approximately 14- to 16- and approximately 8- to 11-fold, respectively, in both the 1/1 and 2/2 PAI-1 genotype HUVEC cultures transfected with the p2PAI110/luc construct. The positive control interleukin-1 showed an approximately 7- to 12-fold response in the 1/1 and 2/2 PAI-1 genotype HUVEC cultures transfected with either of the constructs. These cross-over results demonstrate that regulation of either the 1/1 or 2/2 PAI-1 genotype by its respective inducer is due to the promoter itself and not to some factor(s) expressed differently in the 1/1 or 2/2 PAI-1 genotype HUVEC cultures.

Concentration of endogenous tPA antigen in coronary artery disease: relation to thrombotic events, aspirin treatment, hyperlipidemia, and multivessel disease

Tissue plasminogen activator (tPA) is the major plasminogen activator responsible for dissolving blood clots found in blood vessels. However, elevated concentrations of tPA antigen were found to be related to adverse events in patients with coronary artery disease (CAD). Considerable controversy about the significance of these results exists. The goal of this cross-sectional study was to identify independent determinants for tPA antigen concentrations in patients with CAD, to possibly clarify the above paradoxical relationship. The baseline tPA antigen concentrations of 366 patients with angiographic evidence of coronary sclerosis were determined. Univariate analysis showed that age (P=0.013), angiographic extent of disease (P<0.001), presence of angina at rest (P<0.001), diabetes mellitus (P=0.004), hypercholesterolemia (P=0. 045), hypertriglyceridemia (P=0.015), and chronic intake of nitrates (P<0.001) were significantly and positively related to tPA antigen concentration, while the chronic intake of aspirin was inversely related to tPA antigen (P<0.001). In addition, plasminogen activator inhibitor type 1 (PAI-1) activity was found to be significantly and positively associated with tPA antigen concentration (P<0.001). A multivariate analysis identified chronic low-dose aspirin therapy (P<0.001), PAI-1 activity (P<0.001), hypertriglyceridemia (P=0.005), the type of angina (P=0.026), multivessel disease (P=0.041), and hypercholesterolemia (P=0.043) as significant and independent determinants of tPA antigen. While hypertriglyceridemia and hypercholesterolemia both are related to the underlying disease, the type of angina and the number of involved vessels are linked to the severity and extent of disease, and all of them are indicators of a prothrombotic state found during the progression of CAD. In contrary, low-dose aspirin rather would decrease the likelihood of thrombotic events. The relation of tPA antigen to PAI-1 activity furthermore underlines the relation between tPA antigen concentration and a prothrombotic state. Therefore, the positive or-in case of aspirin therapy-negative correlation of these parameters with tPA antigen concentration would indicate that thrombus formation and simultaneous endothelial cell activation might be major determinants for tPA antigen concentration in CAD.

Segregation analysis of plasminogen activator inhibitor-1 and fibrinogen levels in the NHLBI family heart study

Elevated plasminogen activator inhibitor-1 (PAI-1) and fibrinogen concentrations are risk factors for coronary heart disease. We investigated environmental, familial, and genetic influences on PAI-1 antigen and fibrinogen concentrations in 2029 adults from 512 randomly ascertained families in 4 US communities. We used maximum-likelihood segregation analysis to fit several genetic and nongenetic modes of inheritance to the data to determine whether mendelian inheritance of a major gene could best explain the familial distributions of these 2 hemostatic factors. Age- and gender-adjusted familial correlations for PAI-1 antigen level averaged 0.16 in first-degree relatives (95% CI=0.11 to 0.21); the spouse correlation was positive but not statistically significant (r=0.10, 95% CI=-0.02 to 0.23). Complex segregation analysis indicated a major gene associated with higher PAI-1 concentrations in 65% of individuals from these families. Demographic, anthropometric, lifestyle, and metabolic characteristics together explained 37% to 47% of the variation in PAI-1 antigen levels, and the inferred major gene explained an additional 17% of the variance. Positive and statistically significant age- and gender-adjusted familial correlations in first-degree relatives indicated a possible heritable component influencing plasma fibrinogen concentration (r=0. 17, 95% CI=0.13 to 0.22); however, segregation analysis did not provide statistical evidence of a major gene controlling fibrinogen level. These family data suggest that there are modest familial and genetic effects on the concentration of PAI-1.

Relationship between obesity and the increased risk of major complications in non-insulin-dependent diabetes mellitus

Obesity and non-insulin-dependent diabetes mellitus (NIDDM) are closely linked. They frequently occur together in patients, and body mass index (BMI) is the strongest risk factor for the development of NIDDM. Both obesity and NIDDM are also major causes of morbidity and mortality from atherogenic macrovascular disease, and they are independent risk factors for coronary heart disease. The risk of developing NIDDM and cardiovascular disease is affected by the regional distribution of body fat. Visceral obesity is associated with a higher degree of risk than peripheral obesity. The metabolic and circulatory changes associated with visceral obesity lead to the development of insulin resistance and increased lipoprotein synthesis. For example, the change in the population profile of lipoproteins in the blood, and alterations in the levels of oxidative stress lead to an increased cardiovascular and macrovascular risk. The changes in lipid metabolism also affect haemorrheological function. They have been linked to decreased fibrinolysis (a serious cardiovascular risk factor) through elevated levels of plasminogen activator inhibitor factor, high blood viscosity, and increased erythrocyte aggregability. Increased BMI also appears to be associated with endothelial dysfunction, which is a major factor in atheroma plaque formation and development of thrombosis. Visceral obesity therefore adds a significant burden to the already increased cardiovascular risk inherent in NIDDM. However, even moderate weight loss may successfully reverse the majority of changes seen with visceral obesity.

Cardiovascular risk continuum: implications of insulin resistance and diabetes

Although low-density lipoprotein (LDL) cholesterol is a critically important factor in the development of atherosclerosis, nearly half the patients with coronary artery disease have LDL cholesterol levels within the National Cholesterol Education Program (NCEP) guidelines. Therefore, attention has focused on other modifiable risk factors that could strongly impact the development of coronary artery disease. Type 2 diabetics have a 3-fold increased risk of coronary artery disease; prediabetics, without chronic hyperglycemia, have a 2-fold increased risk compared with normal subjects. Insulin resistance has also been implicated as the cause of atherosclerosis. Insulin resistance is associated with hyperinsulinemia and a constellation of other factors, some of which are themselves independent risk factors for coronary artery disease. These include reduced levels of high-density lipoprotein (HDL) cholesterol, hypertriglyceridemia, increased small dense LDL particles, hypertension, visceral obesity, and increased levels of plasminogen activator inhibitor-1 (PAI-1). Hyperinsulinemia and insulin resistance at the vascular level also may contribute to vascular injury and the atherosclerotic process. Current studies suggest that controlling hyperglycemia, LDL cholesterol, and blood pressure are important to protect the diabetic from atherosclerosis. A key question, particularly in type 2 diabetes, is to define the best regimen for glucose control that will protect the vasculature. Sulfonylureas, metformin, and troglitazone have direct vascular actions. Metformin lowers LDL cholesterol and triglycerides, while troglitazone reverses many of the components associated with the insulin resistance syndrome. Clinical trials focusing on coronary artery disease outcomes are now warranted to prevent coronary artery disease, the major vascular complication and cause of mortality in diabetes.

The relationships between insulin and plasminogen activator inhibitor 1 levels: assessment in groups of subjects with dyslipidaemia and hypertension

Elevated plasminogen activator inhibitor-1 (PAI-1) levels have been described in some populations to associate with hyperinsulinaemia in the metabolic syndrome which predisposes to coronary heart disease (CHD). This association, if consistently present, could provide more evidence for a synergistic role for insulin resistance and altered fibrinolysis in the pathogenesis of CHD. To test the hypothesis further therefore, we explored the relationships between the fasting levels of insulin and PAI-1 and lipids in groups of non-diabetic Arab subjects classified as: A: normolipidaemic (n = 148); B: hyperlipidaemic: (n = 99), subdivided into - C: normotensive (n = 71) and D: hypertensive (n = 28); and E: patients with CHD (n = 12). In Group A, fasting insulin (FI) was 7.2+/-(SD) 3.4 mU/l, PAI-1 30.6+/-9.7 ng/ml, both levels significantly lower (P < 0.05) than in Group B as a whole (FI 9.7+/-5.2, PAI-1 36.9+/-10.6), or as normotensive Group C (FI 9.4+/-5.4, PAI-1 36.7+/-10.3) or hypertensive Group D (FI 10.9+/-4.8, PAI-1 37.2+/-11.5). These values were highest in the hyperlipidaemic hypertensive Group D. There were no significant differences relative to the hyperlipidaemic phenotype of predominant hypercholesterolaemia, hypertriglyceridaemia or mixed hyperlipidaemia. PAI-1 (34.7+/-13.8) and FI (7.0+/-2.4) levels in Group E with CHD were similar to those of Group A but lower than values seen in Groups B, C and D. Consistent positive correlations (r = 0.32-0.41, P <0.01) were demonstrable in all the groups between PAI-1 and triglycerides levels. There were also significant correlations between insulin and PAI-1 (r = 0.20, P<0.1) in all the subjects (grouped as a whole, n = 259) and in normolipidaemic Group A (r = 0.29, P < 0.01) but not in any of the hyperlipidaemic groups or in patients with CHD. This study therefore suggests that levels of insulin and PAI-1 are increased in hyperlipidaemic subjects, particularly when also hypertensive. The further observation of significant correlations between insulin and PAI-1 levels only in normolipidaemic subjects and not those who were hyperlipidaemic or with CHD is at variance with observations in Caucasians in whom strong positive correlations between insulin and PAI-1 had suggested that elevated PAI-1 levels should constitute one more component of the metabolic syndrome which strongly predisposes to CHD. Whether this is a racial variation or an artifact of the insulin/PAI-1 assay methodology is unclear and deserves further study.