Interindividual and intraindividual variability in plasma fibrinogen, TPA antigen, PAI activity, and CRP in healthy, young volunteers and patients with angina pectoris

We compared intraindividual and interindividual variability in the plasma levels of fibrinogen, tissue-type plasminogen activator (TPA) antigen, plasminogen activator inhibitor (PAI) activity, and C-reactive protein (CRP) in 20 healthy, young individuals and 26 patients with stable angina pectoris (AP) who were at higher risk for cardiovascular disease. For each of the four parameters, the contribution of the intraindividual variation to the total variance (13% and 9% for fibrinogen, 3% and 5% for TPA antigen, 4% and 20% for In[PAI activity], and 14% and 9% for In[CRP] for the healthy volunteers and AP patients, respectively) was smaller than the contribution from the interindividual variation. These results indicate that single sampling is sufficient to assess an individual level for TPA antigen and PAI activity, whereas duplicate sampling for fibrinogen and triplicate sampling for CRP are recommended. In an epidemiological study the sample sizes, based on the variances found in the transverse part of the study, needed to detect a 15% difference between the two groups (with alpha = 0.01 and a statistical power = .90) are 31 and 40 for fibrinogen, 568 and 146 for TPA antigen, 603 and 119 for PAI activity, and 1490 and 2263 for CRP in healthy volunteers and patients with AP, respectively. Additionally, we studied the contribution of genetic polymorphisms of the B beta-fibrinogen (Bcl I and G-->A-455) and PAI activity (HindIII and CA-repeat) genes to intraindividual and interindividual variation. Fibrinogen genotypes were associated with plasma fibrinogen levels in the volunteers but not in the AP patients. No effects of fibrinogen or PAI polymorphisms on intraindividual variation were observed in either healthy individuals or AP patients. In this study intraindividual variation in plasma levels of the cardiovascular risk indicators fibrinogen, TPA antigen, PAI activity, and CRP was small when compared with the interindividual variation in healthy, young volunteers and patients with stable AP.

Reduced response to activated protein C is associated with increased risk for cerebrovascular disease

BACKGROUND

Resistance to activated protein C (APC), which results from various factors, including a mutation in the gene for coagulant factor V, has been associated with increased risk for venous thrombosis. However, its relation to arterial disease is still not well defined.

OBJECTIVE

To investigate the association of both response to APC and the factor V Leiden mutation with arterial disease.

DESIGN

Population-based case-control study.

SETTING

A district of Rotterdam, the Netherlands.

PARTICIPANTS

115 patients with a history of myocardial infarction; 112 patients with a history of stroke, transient ischemic attack, or both; and 222 age-matched controls without arterial disease chosen from among 7983 persons in the Rotterdam Study cohort. Patients using anticoagulant drugs were excluded.

MEASUREMENTS

Response to APC was determined in double-centrifuged platelet-poor plasma. Patients were genotyped for the Arg 506 to Gln mutation in the gene for coagulant factor V.

RESULTS

The prevalence of cerebrovascular disease increased gradually and corresponded to a decreasing response to APC (odds ratio per 1-unit decrease of response to APC, 1.43 [95% CI, 1.12 to 1.81], adjusted for age and sex). Adjustment for the factor V mutation did not change the findings. We found no association between response to APC and myocardial infarction or between factor V mutation and cerebrovascular disease or myocardial infarction.

CONCLUSIONS

Low response to APC is associated with an increased risk for cerebrovascular disease but not with an increased risk for myocardial infarction, independent of the factor V Leiden mutation. The association between the factor V Leiden mutation and cerebrovascular disease or myocardial infarction remains to be determined.

Modulation of plasma fibrinogen levels by ticlopidine in healthy volunteers and patients with stable angina pectoris

Elevated plasma fibrinogen levels are associated with an increased risk for cardiac events. Ticlopidine is a drug that inhibits the ADP-induced aggregation of blood platelets and it also has been described that ticlopidine can decrease the plasma fibrinogen level in patients with vascular diseases. The mechanism of this decrease has not yet been elucidated and therefore mechanisms that are known to affect fibrinogen levels were studied, viz, the acute phase reaction, total fibrin plus fibrinogen degradation (TDP) levels and the polymorphisms of the fibrinogen beta-gene. The fibrinogen lowering effect of ticlopidine was studied in 26 healthy volunteers, selected on genotype of the Bcl] polymorphism of the fibrinogen beta-gene, and in 26 patients with stable angina pectoris in a double blind, randomized cross-over study. Functional plasma fibrinogen levels were measured with the Clauss assay. Fibrinogen antigen, C-reactive protein (CRP) and TDP levels were measured using an enzyme immuno assay (EIA). In the healthy volunteers the functional fibrinogen levels had decreased by 0.20 g/l (9%, p = 0.005 using the paired Student l-test) after 4 weeks of 250 mg bid ticlopidine administration, whereas fibrinogen antigen, CRP and TDP levels were not significantly changed. In the stable angina pectoris patients the pre-treatment fibrinogen, CRP and TDP levels were significantly higher than in the volunteer group. After four weeks 250 mg bid ticlopidine administration the functional fibrinogen levels had decreased by 0.38 g/l (11%, p < 0.005), whereas the fibrinogen antigen, CRP and TDP levels were not significantly changed. The levels of functional and antigen fibrinogen, CRP and TDP did not change significantly during the placebo period in the volunteers or the patients. Neither in the volunteers nor in the patients was the effect of ticlopidine on the fibrinogen levels associated with the fibrinogen beta-gene polymorphisms. Therefore, the fibrinogen lowering effect of ticlopidine is likely to be a modulation of the functionality of the molecule and unlikely to be modulated by the acute phase reaction, TDP-levels or the fibrinogen beta-gene polymorphisms.

Temporal relation between ischemic episodes and activation of the coagulation system in unstable angina

BACKGROUND

Although a major role of coronary thrombosis in the pathogenesis of unstable angina has been demonstrated, the results of a series of studies have suggested that activation of the hemostatic system may not be confined to ischemic episodes. The purpose of this study was to investigate the temporal relation between ischemic episodes and activation of the coagulation system in unstable angina.

METHODS AND RESULTS

Thrombin-antithrombin III (TAT) and prothrombin fragment 1 + 2 (F1 + 2) levels were measured in 13 patients during spontaneous ischemic episodes (time 0, 5, and 15 minutes and 1 hour) to evaluate the time course of the activation of the coagulation system associated with the development of ischemia (protocol A). TAT and F1 + 2 levels were also measured in 28 patients with unstable angina on admission to hospital (every 6 hours for 24 hours and daily for 3 days) to assess their temporal relation with ischemic episodes (protocol B). In protocol A, TAT and F1 + 2 levels were elevated in 10 of 13 patients (77%) in at least 1 sample. The median value of TAT showed a peak at 5 minutes and returned to baseline within 15 minutes (P < .05), consistent with its plasma half-life of 5 minutes, whereas the median value of F1 + 2 showed no significant changes, possibly because of its longer half-life, which tends to dampen sudden bursts of thrombin production. In protocol B, activation of the clotting system was found in 10 of 33 samples (30%) temporally related to ischemia and also in 23 of 150 (15%, P = .07) of those not temporally related to ischemia.

CONCLUSIONS

Our study demonstrates that patients with active unstable angina develop frequent bursts of thrombin production not necessarily associated with ischemic episodes and that, conversely, some ischemic episodes are not associated with evidence of thrombin activation.

Association of plasma fibrinogen levels with coronary artery disease, smoking and inflammatory markers

The plasma level of fibrinogen is associated with the risk of ischaemic heart disease (IHD) and the severity of atherosclerosis. It has been suggested that an increased plasma level of fibrinogen is a coronary risk indicator because it reflects the inflammatory condition of the vascular wall. An inflamed vascular wall may increase the production of the cytokines interleukin 6 (IL6), interleukin 1-beta (IL1-beta), and tumour necrosis factor alpha(TNF-alpha), which have a major role in the regulation of synthesis in the liver of acute phase proteins, including fibrinogen. Smoking has also been reported to increase the levels of fibrinogen and C-reactive protein (CRP). This may indicate that smoking induces an inflammatory reaction, probably of the pulmonary bronchi and alveolae. Therefore, we anticipated that with both types of inflammation the levels of acute phase proteins and cytokines would be related. We have investigated the contribution of inflammation to the plasma levels of fibrinogen in 34 patients with severe coronary artery disease (CAD) and 30 healthy controls comparable for age and smoking habits. We did not find a parallel in the effects of smoking and ischaemic heart disease on the plasma levels of fibrinogen, CRP, IL6, IL1-beta and TNF-alpha. Cardiovascular disease had its most important effect on the plasma fibrinogen level, while smoking appeared to increase the CRP levels, while both CAD and smoking seemed to affect the IL6 levels. Our results indicate that both smoking and CAD induce an inflammatory condition but that the increase of plasma levels of different inflammatory markers is complex. Although the acute phase reaction is the main regulatory mechanism of fibrinogen, the increase of fibrinogen in our group of CAD patients could not be fully explained by increased inflammation.

Elevated fibrinogen and the relation to acute phase response in diabetic nephropathy

Insulin-dependent diabetic patients with nephropathy have a high risk of cardiovascular disease. Chronic inflammation is a part of the pathogenesis of atherosclerosis, and presently we have studied the relation between the inflammatory state, measured as levels of interleukin-6 and C-reactive protein and fibrinogen in diabetic nephropathy. Thirty-three insulin-dependent diabetic patients with diabetic nephropathy (urinary albumin excretion rate (AER) > 300 mg/24-h) and 22 patients with incipient diabetic nephropathy (AER 30-300 mg/24-h) were compared with 14 non-diabetic controls and 17 diabetic patients with normal AER (<30 mg/24-h). Fibrinogen was significantly higher in diabetic nephropathy than in non-diabetic controls and diabetic patients with normal AER (median 8.1, range (5.4-15.6) mu mol/l vs. 6.6 (5.0-12.1) mu mol/l, p < 0.05, and 6.2 (5.0-9.0) mu mol/l, p < 0.005, respectively), while C-reactive protein did not deviate between groups. Interleukin-6 was significantly elevated in all insulin-dependent diabetic patients (diabetic nephropathy (3.2 (1.0-14.5) pg/ml, p < 0.005), incipient nephropathy (3.7 (1.0-22.9) pg/ml, p < 0.005) and diabetic patients with normal AER (2.7 (1.0-9.0) pg/ml, p < 0.05) compared with nondiabetic controls (1.2 (1.0-6.2) pg/ml)). When fibrinogen was adjusted for interleukin-6, C-reactive protein or both, the level of fibrinogen was still higher in patients with diabetic nephropathy than in patients without nephropathy (p < 0.05), which suggests that inflammation is not the only mechanism that increases fibrinogen levels in patients with diabetic nephropathy.

Episodic activation of the coagulation system in unstable angina does not elicit an acute phase reaction

The results of our study suggest that the acute phase response may be partly related to a yet unknown primary inflammatory component in unstable angina. Further studies are needed to elucidate the actual role of inflammation in unstable angina and its relation to activation of the coagulation system.

Fibrin binding of plasminogen coated liposomes in vitro

In this study, the fibrin binding properties of liposomes containing a number of plasminogen (Plg) molecules on the outside were compared to those of free (non-liposomal) Plg in an in vitro model system. Fibrin monolayer coated 96-wells plates were used, containing fibrin monomer at a density of around 3.4 to 3.9 x 10(-4) nmol/cm2. These densities are similar to liposomal Plg-densities, thus allowing multivalent interactions to occur. In the panel of experimental conditions that was chosen, binding of free Plg and liposomes with Plg showed three main differences in characteristics. Firstly, in the fibrin binding of Plg-liposomes not all Plg may be involved, but on the average 40% of the total amount of liposomal Plg. This was shown by lysing the liposomes after binding to the fibrin and estimation of truly bound Plg. With Plg-densities on the liposomes below the fibrin binding sites density, the maximal number of bound Plg molecules remains below the amount of available fibrin binding sites. Secondly, a higher binding rate by at least one order of magnitude was observed for liposomes with Plg compared to free Plg. Thirdly, liposomes with Plg exhibit a fibrin binding affinity which increases with Plg-density, because of the multivalent character of interaction. Liposomal Plg can successfully compete for fibrin binding sites with a 100 fold higher concentration of free Plg. These in vitro findings indicate that in view of avid and rapid fibrin binding, liposomes with attached plasminogen may be suitable for in vivo targeting to fibrin based thrombi.

An amino acid polymorphism in histidine-rich glycoprotein (HRG) explains 59% of the variance in plasma HRG levels

A pedigree-based maximum likelihood method developed by Lange et al. (12) was used to study the contribution of a newly defined di-allelic polymorphism in histidine-rich glycoprotein (HRG) to the plasma levels of HRG. In four families (n = 99) and 20 volunteers we found a heritability of 70%, an age effect of 3% and an effect of individual environmental factors of 27%. These results are remarkably similar to the results found in a previous parent-twin study in which a heritability of 69% and an effect of random environment of 31% was found. The overall genetic influence in the present study can be subdivided into an effect of 59% by the HRG phenotype and 11% by residual genetic factors. The influence of the HRG phenotype of 59% can entirely be explained by adding up the effect of the two alleles that make up the phenotype. These results indicate a codominant inheritance pattern of HRG levels in which the genetic influences can almost completely be ascribed to the additive effect of the di-allelic HRG locus whereas only a small part is due to other loci.

Identification and genetic analysis of a common molecular variant of histidine-rich glycoprotein with a difference of 2kD in apparent molecular weight

Two forms of histidine-rich glycoprotein (HRG) were detected on SDS-PAGE by silver staining and immunoblotting after isolation of the protein from pooled plasma using immuno-affinity chromatography followed by chromatography with heparin-Sepharose. Both forms were single-chain molecules and the apparent molecular weights of form 1 and form 2 were 77 kD and 75 kD respectively. Mendelian inheritance of both HRG forms was observed in four families with 24 informative meioses, strongly suggesting that the two forms are encoded by different alleles. The frequency of form 1 and form 2 in a group of 36 individuals was 0.35 and 0.65 respectively. The difference between the two molecular variants was studied by direct sequence analysis of amplified exons of the HRG gene from 6 individuals who were homozygous either for form 1 or form 2. Five amino acid polymorphisms in three different exons were observed: Ile/Thr in exon4; Pro/Ser in exon 5; His/Arg, Arg/Cys and Asn/Ile in exon 7. Analysis of these polymorphisms in 20 volunteers showed that only the Pro/Ser polymorphism at position 186 in exon 5 was coupled to the form of the HRG protein. Ser was found in form 1 and Pro in form 2. The presence of Ser at position 186 introduces a consensus sequence for a N-glycosylation site (Asn-X-Ser/Thr). By removing N-linked sugars with N-glycanase, it could be demonstrated that the difference between the two forms of HRG is caused by an extra carbohydrate group at Asn 184 in form 1.

Beneficial effect of a moderately energy-restricted diet on fibrinolytic factors in non-obese men

Impaired fibrinolytic activity has been reported in the elderly and is thought to play a role in the etiology of cardiovascular disease, one of the leading causes of death in most Western countries. Since restriction of energy intake has been demonstrated to act beneficially on the aging process in a variety of species, we studied the effect of a 10-week moderately energy-restricted (ER) regimen (80% of habitual) on plasminogen activator inhibitor (PAI) activity, PAI-1 antigen, tissue plasminogen activator (tPA) activity, and tPA antigen in non-obese, middle-aged men. Moreover, the relationship between these fibrinolytic markers and glucose tolerance was investigated. Weight loss in the ER group (n = 16) was considerable (-7.4 +/- 1.7 kg, P < .001). Subjects in the control group (n = 8) also lost some weight (-2.1 +/- 1.5 kg, P < .01). Fasting glucose levels decreased in the ER group (-0.31 +/- 0.48 mmol/L, P < .05), which was correlated with the extent of weight loss (P < .01). Baseline insulin levels at 2 hours after an oral glucose load correlated with baseline PAI activity (P < .001) and PAI-1 antigen levels (P < .001). PAI activity decreased in the ER group (-2.94 +/- 2.90 IU/mL, P < .001), particularly in subjects with a high baseline PAI activity (> 9 IU/mL). Furthermore, energy restriction led to decreased PAI-1 antigen concentration (P < .05), a nonsignificant increase in tPA activity, and a decrease in tPA antigen concentration (P < .001). All these changes were more clear in subjects with a high baseline PAI activity. These results suggest that 10 weeks of moderate energy- restriction has a profibrinolytic effect in non-obese, middle-aged men, at least in subjects with higher baseline PAI activity (> 9 IU/mL). Moreover, in line with the suggestion that high PAI activity goes together with insulin resistance, a relationship between insulin concentration after a glucose load and PAI activity was found.

Early spontaneous intermittent myocardial reperfusion during acute myocardial infarction is associated with augmented thrombogenic activity and less myocardial damage

OBJECTIVES

This study investigated the influence of early spontaneous intermittent reperfusion on the extent of myocardial damage and its relation to endogenous hemostatic activity.

BACKGROUND

In the early phase of acute myocardial infarction coronary occlusion is often intermittent, even before thrombolytic therapy is administered. The relation between this phenomenon, myocardial damage and hemostatic activity is unknown.

METHODS

Holter ST segment recording and pretreatment plasma tissue-type plasminogen activator (t-PA) antigen, plasminogen activator inhibitor-1 (PAI-1) antigen, prothrombin fragment F1 + 2 and soluble fibrin levels were measured in 57 patients with acute evolving myocardial infarction. Spontaneous intermittent myocardial reperfusion, defined as two or more episodes of transient resolution of ST segment elevation to within 0.05 mV of baseline, lasting > or = 1 min, before the start of recombinant t-PA (rt-PA) treatment was present in 28 patients (group 1) and absent in 29 (group 2). Left ventriculography and coronary angiography were performed 90 min after intravenous rt-PA administration. Plasma creatine kinase-MB fraction (CK-MB) levels were measured every 6 h for 24 h, and C-reactive protein levels were measured daily for 3 days.

RESULTS

Group 1 had lower peak plasma CK-MB (141.9 +/- 28.3 vs. 203.8 +/- 23.3 IU/liter [mean +/- SEM], p < 0.014) and C-reactive protein levels (16 +/- 4 vs. 28 +/- 4 mg/liter on day 1; 26.6 +/- 5.5 vs. 61.8 +/- 14.4 mg/liter on day 2; 19.6 +/- 4.2 vs. 40.6 +/- 6.5 mg/liter on day 3, p < 0.012) and a higher left ventricular ejection fraction (62.9 +/- 4% vs. 51.1 +/- 5%, p < 0.04) than group 2. Group 1 had lower plasma t-PA antigen levels (15.6 vs. 27 micrograms/liter, p < 0.006) but higher prothrombin fragment F1 + 2 (1.8 vs. 1.1 nmol/liter, p < 0.003) and soluble fibrin levels (66.8 vs. 31 nmol/liter, p < 0.01). Coronary patency at 90 min was similar.

CONCLUSIONS

Early spontaneous intermittent reperfusion during acute myocardial infarction is associated with augmented thrombogenic activity and less subsequent myocardial damage. This finding is consistent with a protective effect of intermittency on the myocardium and a procoagulant effect of spontaneous lysis on blood. It may also reflect a different rate of evolution of coronary thrombosis and myocardial infarction in patients with and those without spontaneous intermittent myocardial reperfusion.

Gender-related association between beta-fibrinogen genotype and plasma fibrinogen levels and linkage disequilibrium at the fibrinogen locus in Greenland Inuit

Elevated plasma fibrinogen levels represent an increased risk for cardiovascular disease, but the mechanism explaining this association is still not clear. Genetic differences may play a role, because it has been shown that individuals who carry the rare alleles of polymorphisms in the genes for the B beta-chain (Bcl I and G/A-455) and the A alpha-chain (Taq I) of fibrinogen have higher plasma fibrinogen levels and that patients with peripheral arterial disease have a higher frequency of the rare allele of the Bcl I polymorphism than do healthy control subjects. We studied the Greenland Inuit, a population with a low incidence of ischemic heart disease; polymorphisms of the fibrinogen gene; and their association with plasma fibrinogen level. The group studied had a small age range (30 to 34 years), 97% were smokers, 62 were men, and 71 were women. We observed that in the Inuit, frequencies of the rare alleles of the beta gene and of the common alleles of the alpha gene polymorphisms were lower than those published for other populations (all Caucasian). Accordingly, in the Inuit, these distribution patterns give a higher frequency of alleles that are associated with lower plasma fibrinogen levels. We further observed comparable linkage disequilibrium between alpha and beta gene polymorphisms in Caucasian populations. In Inuit men the rare allele of the Bcl I and G/A-455 fibrinogen polymorphisms was associated with plasma fibrinogen level comparable with the association described in Caucasian populations.(ABSTRACT TRUNCATED AT 250 WORDS)

Protection of single-chain urokinase-type plasminogen activator (scu-PA) in aprotinin treated cardiac surgical patients undergoing cardiopulmonary bypass

Intraoperative high-dose aprotinin administration has been shown to reduce the intra-and postoperative blood loss in cardiac surgery. The haemostatic effect has been attributed to platelet preserving properties and to inhibition of contact activation reducing thrombotic and fibrinolytic activity during and after cardiopulmonary bypass (CPB). Here we report on the effects of aprotinin on urokinase-type plasminogen activator, especially on the protection of the zymogen single-chain urokinase-type plasminogen activator (scu-PA). scu-PA occurs cell associated as well as free in the circulation (concentration 50 pM, half-life 5 min), and is potentially activated by kallikrein and plasmin, both potent targets for aprotinin. The generated active two-chain u-PA (tcu-PA) is a powerful activator of fibrinolysis. Sixteen male patients undergoing myocardial revascularization were randomly assigned to aprotinin treatment (A) or control group (C). Plasma concentration of total u-PA antigen and of the specific forms scu-PA(zymogen) and tcu-PA(active enzyme) were measured at different stages intraoperatively and two hours postoperatively. After an initial drop due to haemodilution at the onset of CPB, the concentrations of circulating u-PA forms restored intraoperatively in A, but remained subnormal in C until the end of the observation period. The concentration of total u-PA antigen of shed mediastinal blood was both in A and C two-fold higher than in the circulation, but the antigen was preserved as the zymogen scu-PA in A and largely converted to an inactive, non activatable form in C. Intra- and postoperative blood losses were less than half the amount in A as compared to C.(ABSTRACT TRUNCATED AT 250 WORDS)