Thrombin-activatable Fibrinolysis Inhibitor Antigen Levels Research Articles

The G505A Nonsynonymous Single-Nucleotide Polymorphism (SNP) in TAFI, the Gene Encoding Thrombin-Activatable Fibrinolysis Inhibitor (TAFI) Is Pleiotropically Associated with TAFI Antigen Levels and Coronary Heart Disease (CHD) in Mexican Americans of South Texas

Studies have reported that the G505A nonsynonymous (ns)-SNP encoding the Ala147Thr amino acid substitution in TAFI, is associated with a reduction in risk of venous thrombosis and myocardial infarction. Interestingly, homozygosity for the A-allele (AA) of G505A is associated with increased TAFI antigen (TAFI:Ag) levels in plasma. In our study of the genetic determinants of cardiovascular disease (CVD) in Mexican Americans of South Texas, we performed an exome-wide scan in relation to plasma TAFI antigen levels in 784 individuals. While accounting for age, sex, and their interactions as confounders in linear mixed model, we found a heritability of 59% for TAFI:Ag levels (p=1.4E-19), and that ns-SNP G505A was the only variant showing exome-wide significance (p=3.5E-14; Figure A). Figure B shows the quantile-quantile distribution of the p-values from all the exome-wide tests. Clearly, the p-value distribution reveals that there is no systematic bias that may act to skew the p-values, and that the lone exception¾in agreement between observed and expected quantiles¾is due to this TAFI SNP, which strongly suggests a truly significant effect. Consistent with previous reports, the regression coefficient for G505A as a predictor of TAFI:Ag levels showed them to be increasing from the homozygous for the major G-allele (GG), to the heterozygous individuals (GA), to the individuals homozygous for the minor A-allele (AA) (Figure B). We also investigated if G505A is associated with our CHD variable. Using a statistical genetic model for the liability to disease conditional on a threshold, which is equivalent to a probit mixed model, we found that the G505A ns-SNP in TAFI, encoding TAFI Ala147Thr, is significantly associated with a reduction in the risk of CHD (p=0.002). As observed in existing literature, potential limitations of this study include the ELISA assay used for the quantification of TAFI levels. Some ELISA assays measure proTAFI, TAFIa, and TAFIi. However, recent evidence suggests that there may be cross reactivity between TAFIa and TAFIi. This can result in measuring ongoing TAFI activation peptides and elevated levels of TAFIa which ultimately goes on to make resistant fibrin. This is likely the marker that results in the increased risk of venous thromboembolism. To mitigate this confounding factor, an ELISA assay specific to measuring TAFI antigen is needed. In conclusion, we found that TAFI G505A is pleiotropically associated with TAFI:Ag levels and risk of CHD. [Display omitted] DisclosuresDeFronzo: AstraZeneca: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novo Nordisk: Membership on an entity's Board of Directors or advisory committees; Boehringer-Ingelheim: Membership on an entity's Board of Directors or advisory committees, Research Funding; Intarcia: Membership on an entity's Board of Directors or advisory committees; Merck: Research Funding.

Thrombin-Activatable Fibrinolysis Inhibitor (TAFI) Antigen Levels and TAFI Gene Polymorphisms in Patients with Budd-Chiari Syndrome and Portal Vein Thrombosis.

Background Budd-Chiari syndrome (BCS) and Portal Vein Thrombosis (PVT) have been associated with several hypercoagulable states. Thrombin-activatable fibrinolysis inhibitor (TAFI) potently attenuates fibrinolysis. Elevated TAFI antigen levels form a risk factor for deep venous thrombosis and are to a high extend genetically determined. To establish the pathogenetic role of TAFI in BCS and PVT, we studied TAFI antigen levels and gene polymorphisms in patients with BCS, PVT and matched controls.Methods In a multicenter case-control study, 39 patients with BCS, 85 patients with PVT and 118 population-based controls were identified. Plasma levels of TAFI antigen were determined by a commercially available ELISA and polymorphisms of the TAFI gene (TAFI 505A/G and TAFI 1040C/T) were analysed by PCR. Because TAFI antigen levels are decreased in patients with impaired liver synthesis, plasma levels were corrected for antithrombin activity levels. ANOVA techniques were used to correlate TAFI polymorphisms with TAFI antigen levels.Results Mean plasma TAFI antigen levels were significantly lower in BCS and/or PVT patients as compared to controls, even after adjusting for impaired liver function by antithrombin activity levels (all p<0.002). There was a strong correlation between the TAFI 505 A/G and TAFI 1040 C/T polymorphisms and plasma TAFI antigen levels in all groups (all p<0.001). The G-allele of the 505A/G polymorphism was associated with a low antigen level of TAFI. Carriers of the GG genotype had an increased risk for BCS and/or PVT (OR=4.4; 95% CI 1.5–12.6). Carriers of the G allele showed a risk of 4.1 (95% CI 1.5–11.5). For the 1040C/T polymorphism, the T allele was associated with lower levels of TAFI antigen, and carriers of at least one copy of the T allele showed an OR of 1.6 (95% CI 0.9–2.7).Conclusion We found lower TAFI levels in patients with BCS and/or PVT than in healthy controls. In addition two TAFI genotypes, associated with lower TAFI antigen levels were found more frequently in patients with BCS and/or PVT than in healthy controls. Therefore low TAFI levels appear to be a risk factor for the development of BCS and PVT. These results suggest a different pathogenetic mechanism of TAFI in BCS and PVT than in deep venous thrombosis.

Association of Thrombin-Activatable Fibrinolysis Inhibitor with Acute Pulmonary Embolism.

Thrombin-activatable fibrinolysis inhibitor (TAFI) inhibits fibrinolysis and high levels may have an association with thrombosis. The aim of the current study was to investigate the association of TAFI antigen levels with pulmonary thromboembolism (PTE). A case-control study was conducted with 29 patients with PTE and 17 age- and gender-matched control individuals. Plasma levels of TAFI were measured at the time of diagnosis, then at 3 and 6 months after the event. Initial TAFI levels (%) were higher in patients with PTE than in the control group (190,0 [65,0-250,0] vs 133,0 [83,0-153,0]; p = 0.003). TAFI levels significantly decreased at the third and sixth months after initial diagnosis (p < 0.05). The percentage reductions in TAFI levels were 12 and 36.8% at 3 and 6 months, respectively. The Odss ratio (OR) of TAFI level for PTE was found to be 1.024 (95% CI: 1.007-1.040; p = 0.005). There was no significant correlation of initial TAFI levels with age, gender, smoking status, history of thrombosis, pulmonary artery pressure, and D-dimer levels (p > 0.05). In the sixth month of treatment, patients with residual thrombosis were seen to have similar baseline levels and reductions of TAFI as patients without residual thrombosis (p > 0.05). The result of this study suggests that high TAFI levels may have a role in the occurrence of PTE without impact on treatment outcome.

S62798, a TAFIa inhibitor, accelerates endogenous thrombolysis in a murine model of pulmonary thromboembolism

Abstract Pulmonary embolism (PE) is the third leading cause of cardiovascular death in western countries. The enhancement of fibrinolysis constitutes a promising approach to treat thrombotic diseases. In patients, venous thrombosis and thromboembolism risks are associated with increased plasma levels of TAFI (Thrombin Activatable Fibrinolysis Inhibitor) antigen as well as the active form TAFIa. S62798 is a competitive, selective and potent human TAFIa inhibitor (IC50±SD=11.2±0.4nM). It is however less potent on mouse TAFIa (IC50±SD=270±39nM). Here, we tested the ability of S62798 to enhance endogenous fibrinolysis in a mouse model of pulmonary thromboembolism. Human Tissue Factor (TF) was injected in C57Bl6 male mice. Ten minutes later, mice (n=4 to 14 per group) were treated (IV) with S62798 (from 0.01 to 100mg/kg) or vehicle (0.9% NaCl). Ten or twenty minutes (min) later, mice were anesthetized and lungs were collected, homogenized and pulmonary fibrin was quantified by ELISA. Results are expressed as ratio of geometric mean of pulmonary fibrin (μg/mL): tested treatment/ vehicle [95% confidence interval (CI)]. Ten minutes after S62798 treatment, pulmonary fibrin deposition was dose-dependently decreased with a Minimal Effective Dose of 0.04mg/kg [90% prediction interval 0.037 - 0.051] and an ED50 of 0.03mg/kg [95% CI: 0.01; 0.06]. Mice were then treated with 0.1mg/kg S62798 or vehicle (10 min after TF induction) and fibrin deposition in lungs was quantified 10 and 20 minutes post S62798 treatment. The level of pulmonary fibrin deposition was significantly decreased (p&amp;lt;0.0001) compared to vehicle group (ratio 0.31 [0.21; 0.45] at 10 min; 0.35 [0.24; 0.51] at 20 min). Finally, the effect of S62798 (1mg/kg) in combination with heparin was evaluated (n=10/group). When administered 10 min before TF injection, heparin (2000IU/kg) significantly (p&amp;lt;0.0001) decreased pulmonary fibrin level (20 min post TF: ratio 0.03 [0.01; 0.05]). When treatment was done in a curative setting (10 min post TF), heparin alone had no effect (p=0.85) on fibrin deposition (ratio 0.96 [0.65; 1.43]) whereas a similar significant (p&amp;lt;0.0001) decreased pulmonary fibrin deposition was observed in response to S62798 alone or associated with heparin (ratio 0.27 [0.18; 0.40] (S62798 alone) and 0.29 [0.20; 0.43] (S62798+heparin)). In this model, curative S62798 treatment, alone or associated to heparin, accelerated clot degradation by potentiating endogenous fibrinolysis and thus decreased pulmonary fibrin deposition. Due to its capacity to enhance endogenous fibrinolysis, S62798, which has completed phase I studies, is expected to be a therapeutic option for intermediate high risk PE patients on top of anticoagulants. With early recanalization, S62798 should rapidly reduce pulmonary artery pressure and resistance, with concomitant improvement in right ventricular function, preserving cardiac function, and reducing acute PE-related morbidity and mortality in these patients. Funding Acknowledgement Type of funding source: None

Plasma thrombin-activatable fibrinolysis inhibitor (TAFI) antigen levels in acromegaly patients in remission

Background/aimAcromegaly is associated with increased morbidity and mortality, mostly due to cardiovascular complications. Plasma thrombin-activatable fibrinolysis inhibitor (TAFI) antigen levels are associated with coagulation/fibrinolysis and inflammation. Plasma TAFI may play a role in arterial thrombosis in cardiovascular diseases. In this study, it was aimed to evaluate the thrombin-activatable fibrinolysis inhibitor (TAFI) antigen and homocysteine levels in patients with acromegaly and healthy control subjects.Materials and methodsPlasma TAFI antigen and homocysteine levels in 29 consecutive patients with acromegaly and 26 age-matched healthy control subjects were measured. All patients included in the study were in remission. The TAFIa/ai antigen in the plasma samples was measured using a commercially available ELISA kit.ResultsRoutine biochemical parameters, fasting blood glucose, prolactin, thyroid stimulating hormone, total-cholesterol, low density lipoprotein cholesterol, triglyceride, and homocysteine levels were similar in the 2 groups (P > 0.05), whereas the plasma TAFI antigen levels were significantly elevated in the acromegalic patients (154.7 ± 94.0%) when compared with the control subjects (107.2 ± 61.6%) (P = 0.033). No significant correlation was identified by Pearson’s correlation test between the plasma TAFI antigen and homocysteine levels (r = 0.320, P = 0.250).ConclusionA significant alteration in the plasma TAFI antigen levels was detected in acromegaly. Increased plasma TAFI antigen levels might aggravate prothrombotic and thrombotic events in patients with acromegaly.

Determinants of hypofibrinolysis in patients with digestive tract cancer.

IntroductionRecently, we demonstrated that digestive tract cancer (DTC) is associated with reduced fibrin clot permeability and impaired fibrinolysis.AimWe investigated determinants of fibrinolysis in DTC patients.Material and methodsIn 44 consecutive patients with DTC and 47 controls matched for age, sex, and cardiovascular risk, we evaluated fibrinolysis proteins, platelet activation markers, thrombin formation, together with plasma clot lysis time assays in the absence (CLT) and presence of carboxypeptidase potato inhibitor (CLT CPI) that blocks thrombin activatable fibrinolysis inhibitor (TAFI).ResultsIn the DTC group CLT (by 22.3%) and CLT CPI (by 27.4%) were longer compared with controls. The DTC patients had higher plasma fibrinolysis inhibitors, plasminogen activator inhibitor 1 (PAI-1) (by 18.2%), TAFI activity (by 17.3%), and antigen (by 11.2%). The patients had markedly increased platelet markers – soluble CD40 ligand (by 338%) and P-selectin (by 97%), together with von Willebrand factor (vWF) antigen (by 61%). Thrombin-antithrombin complexes (TAT) (by 48.7%) and soluble thrombomodulin (sTM) (by 17.2%) were also increased in the DTC group (all p < 0.05). Patients with high-grade tumours (n = 26) compared with remainders (n = 18) had longer CLT, higher tissue-type plasminogen activator antigen, both TAFI antigen and activity levels, vWF, and sTM. Multiple regression analysis after adjustment for potential confounders showed that independent predictors of CLT in DTC patients were TAT, TAFI activity, and vWF. The only independent predictor of CLT CPI was TAT.ConclusionsHypofibrinolysis in DTC patients is largely driven by enhanced thrombin generation, TAFI, and endothelial injury.

Plasma Thrombin-activatable Fibrinolysis Inhibitor Levels Correlate with the Disease Activity of Ulcerative Colitis.

Objective Patients with ulcerative colitis (UC) are at an increased risk for thromboembolic events, particularly in patients with extensive and active disease. To date, a few studies have been published on the role of thrombin-activatable fibrinolysis inhibitor (TAFI) in UC. However, there are no reports in the literature investigating the effect of UC treatment on plasma TAFI levels. Methods The plasma TAFI antigen levels were quantitatively determined using ELISA kits for 20 UC patients at activation and remission, along with 17 healthy controls. The association between the TAFI levels and inflammatory markers was assessed to determine UC activation. To predict and determine the activation of UC, the Truelove-Witts index and the endoscopic activation index (EAI) were used for each subject. Results The plasma TAFI levels were higher in UC patients at activation of the disease compared with the remission state and in healthy controls. Spearman's correlation analyses revealed that the WBC (r: 0.586, p<0.001), hsCRP (r: 0.593, p<0.001) and EAI (r: 0.721, p<0.001) were significantly correlated with the TAFI levels. The overall accuracy of TAFI in determining UC activation was 82.5% with a sensitivity, specificity, NPV and PPV of 80%, 85%, 81% and 84.2%, respectively (cut-off value: 156.2% and AUC: 0.879). Conclusion The present study demonstrates that the TAFI levels are elevated in the active state of UC. The assessment of TAFI levels in patients with UC in conjunction with other markers of inflammation may provide additional information for estimating UC activation and severity.

Thrombin-activatable fibrinolysis inhibitor Thr325Ile polymorphism and plasma level in breast cancer: A pilot study

This study aimed to investigate thrombin-activatable fibrinolysis inhibitor (TAFI) Thr325Ile polymorphism and TAFI antigen (Ag) levels in breast cancer (BC) in the Egyptian population to clarify their role in relation to BC. A group of 300 females was recruited in this study; of these 150 unrelated patients with different stages of BC and 150 age-matched healthy controls. Plasma TAFI Ag was measured by ELISA and TAFI Thr325Ile (rs1926447) polymorphism was genotyped using TaqMan single nucleotide polymorphism (SNP) genotyping assay. The results showed the genotypes of the minor allele; Thr/Ile (CT) and Ile/Ile (TT) were significantly more frequent in patients compared to control group (50.0% and 22.0% vs. 42.0% and 13.3%, respectively) and were also associated with BC susceptibility [OR=1.9 and 2.6; 95% CI: (1.1–3.3) and (1.3–5.5), respectively P=0.01]. Ile325 allele carriers were more frequent in cases than in controls (47.0% vs. 34.0%) [OR=1.7, (95% CI=1.2–2.4), P=0.001]. However, TAFI Thr325Ile polymorphism was not associated with BC stage or other clincopathological characteristics. TAFI Ag levels were correlated with advanced stages of BC, poor prognosis and risk of recurrence (P=0.02, P=0.04 and P <0.001, respectively) and Thr325Ile SNP was significantly correlated with TAFI antigen levels with the C/C genotype corresponding to the highest and the T/T genotype to the lowest TAFI antigen levels (P<0.001) in the study groups. In conclusion, this study showed for the first time that TAFI Thr325Ile polymorphism could have a contribution to BC susceptibility in our population. Furthermore, high TAFI plasma levels may serve as a predictor of poor prognosis in patients with BC.

PI3-Kinase Inhibitor LY294002 Repressed the Expression of Thrombin-Activatable Fibrinolysis Inhibitor in Human Hepatoma HepG2 Cells.

Thrombin-activatable fibrinolysis inhibitor (TAFI) is a carboxypeptidase B-like proenzyme biosynthesized in the liver and released into the blood circulation. Activated TAFI (TAFIa) has been implicated as an important player in maintaining the balance between blood coagulation and fibrinolysis. In the present study, regulation of TAFI (CPB2) gene expression was investigated using cultured human hepatoma HepG2 cells. HepG2 cells were treated with the phosphoinositide 3-kinase (PI3K) inhibitor LY294002, and the levels of TAFI antigen and CPB2 mRNA were measured. HepG2 cells treated with LY29400 decreased their release of TAFI antigen into the conditioned medium (CM). In parallel, there were decreased levels of CPB2 mRNA and TAFI antigen in the cells. However, CPB2 gene promoter activity was not influenced by treatment of the cells with LY294002. The half-life of the CPB2 transcript was shortened by treatment with LY294002 compared with control. The present results suggest that the PI3K inhibitor LY294002 suppresses expression of TAFI, a prothrombotic factor, by decreasing the stability of CPB2 transcripts.

Impaired fibrinolysis in angiographically documented coronary artery disease.

Impaired fibrinolysis may predispose to coronary artery disease (CAD). Hypofibrinolysis due to high levels of plasminogen activator inhibitor-1 (PAI-1) has been reported in CAD. A novel regulator of fibrinolytic activity, thrombin activatable fibrinolysis inhibitor (TAFI), has attracted attention in recent years. It acts by blocking the formation of a ternary complex of plasminogen, fibrin, and tissue plasminogen activator (t-PA). Previously ambiguous results regarding TAFI levels have been reported in CAD. We measured plasma levels of PAI-1 and TAFI antigen in 123 patients with age ranging from 40 to 65 years who had been submitted to coronary angiography and assessed the association of these markers with the extent of stenosis in three groups: angiographically normal artery (NAn), mild to moderate atheromatosis (MA), and severe atheromatosis (SA). Plasma levels of PAI-1 were increased in patients with severe atheromatosis compared to mild/moderate atheromatosis or to normal patients (66.60, 40.50, and 34.90 ng/mL, resp.; P < 0.001). For TAFI no difference was found between different groups. When patients were grouped in only two groups based on clinical cut-off point for intervention (stenosis less than or above 70%) we found increased plasma levels for PAI-1 (37.55 and 66.60 ng/mL, resp.; P < 0.001) and decreased plasma levels for TAFI (5.20 and 4.53 μg/mL, resp.; P = 0.04) in patients with stenosis above 70%. No difference was found in PAI-1 or TAFI levels comparing the number of affected vessels. Conclusion. As evidenced by a raised level of PAI-1 antigen, one can suggest an impaired fibrinolysis in stable CAD, although no correlation with the number of affected vessels was found. Curiously, a decreased plasma level of total TAFI levels was observed in patients with stenosis above 70%. Further studies measuring functional TAFI are required in order to elucidate its association with the extent of degree of atheromatosis.

Is thrombin-activatable fibrinolysis inhibitor antigen (TAFIag) level significant in recurrent miscarriage?

Objective: The aim of this study was to evaluate the plasma thrombin-tat fibrinolysis inhibitor antigen (TAFIag) levels in women with recurrent miscarriage (RM) and age-matched healthy parous women as controls. Materials and Methods: A total of 80 patients were enrolled in this study. As a study group (group 1), the authors evaluated 49 RM patients who had two or more consecutive abortions with unknown etiology before 12 weeks of gestation. The remaining 31 patients (group 2) were age-matched healthy parous women with no history of miscarriage and experienced at least one live baby. Results: Comparisons of blood TAFIag levels revealed no statistically significant difference between women with recurrent miscarriages and control group. Conclusions: The findings of the present study indicated that TAFIag level was not associated with recurrent miscarriages.

Thrombin activatable fibrinolysis inhibitor

The slow coronary flow (SCF) phenomenon is characterized by slow progression of angiographic contrast medium in the coronary arteries in the absence of stenosis in the epicardial vessels. The pathophysiological mechanisms of SCF phenomenon remain uncertain. Several hypotheses, however, have been suggested for SCF phenomenon, including an early form of atherosclerosis, small vessel dysfunction, dilatation of coronary vessels, imbalance between vasoconstrictor and vasodilatory factors, platelet function disorder, and inflammation. Atherosclerosis and inflammation are the most accepted mechanisms for the pathogenesis of SCF. Thrombin activatable fibrinolysis inhibitor (TAFI) was described as a new inhibitor of fibrinolysis recently and plays an important role in coagulation and fibrinolysis. In previous studies, the role of TAFI was associated with inflammation and evolution of atherosclerosis in coronary artery disease. There are no data available about TAFI levels in patients with SCF phenomenon investigated by angiography. Our goal was to evaluate TAFI antigen (Ag) levels in patients with SCF and to determine the association of the TAFI Ag level with traditional cardiovascular risk factors in our study. The study group constituted 41 patients with angiographically confirmed SCF and 46 patients with normal coronary flow as the control group. The TAFI Ag levels of each patient were determined. Between the control and study group, a statistical difference in the levels of TAFI Ag (p < 0.05) was observed. The TAFI Ag level was significantly higher in the SCF group than the control group (132.21 ± 21.14 versus 122.15 ± 21.59). We have demonstrated that TAFI might be a risk factor for the development of SCF independently of conventional cardiovascular risk factors. In addition, TAFI Ag levels were positively correlated with C-reactive protein (CRP) known as an acute phase reactant. Our findings support the reports of previous studies that increased TAFI levels may be associated with inflammation. Further large studies are required to evaluate the importance of TAFI antigen levels in relation to the development of SCF.

Levels of thrombin activatable fibrinolysis inhibitor in gestational diabetes mellitus

Thrombin-activatable fibrinolysis inhibitor (TAFI) is a procarboxypeptidase, which is synthesised in liver and activated by thrombin and the thrombin–thrombomodulin complex. TAFI suppresses fibrinolysis by removing carboxy–terminal lysine residues from partially degraded fibrin. In this study we aimed to assess the circulating levels of TAFI antigen, ‘a fibrinolytic parameter’ in women with gestational diabetes (GDM). Thirty-four pregnant women with GDM and 50 pregnant women with normal glucose tolerance were included in the study. Plasma TAFI antigen levels were significantly higher in pregnant women with GDM when compared with controls. Increased TAFI levels may contribute to the decreased fibrinolytic potency, causing a thrombophilic state. GDM is regarded as a specific form of diabetes, and it could in addition be a predictor of type 2 diabetes mellitus in the future and the risk of complications due to hypercoagulability increases in this disease. Increased TAFI levels may also have a role in increased risk of hypercoagulability.

Plasma thrombin-activatable fibrinolysis inhibitor as an indicator of inflammation and disease severity in acute pancreatitis

In addition to suppressing fibrinolysis, thrombin activatable fibrinolysis inhibitor (TAFI) was suggested to be involved in inflammation. To date, no study has been published that reports the role of TAFI in acute pancreatitis (AP). Therefore, the objective of the present study was to investigate the role of plasma TAFI as an indicator of inflammation in AP, and its association with disease severity. Plasma TAFI antigen levels quantitatively determined by using ELISA kits in 21 AP patients at onset and remission and 17 healthy controls. Associations of TAFI with inflammatory markers to determine AP and disease severity were assessed. To predict the severity of AP, modified Glasgow prognostic score (mGPS) and computerized tomography severity index (CTSI) were used for each subject. Plasma TAFI levels was higher in AP patients at onset of the disease compared with healthy controls. The disease severity according to mGPS was significantly correlated with TAFI levels. Overall, accuracy of TAFI in determining AP was 83.3% with a sensitivity, specificity, NPV and PPV of 80.9%, 85.7%, 81.8%, and 85% respectively (AUC: 0.915). The present study for the first time demonstrated that TAFI is elevated in AP. The appraisal of TAFI levels in patients with AP in conjunction with other markers of inflammation may provide additional information in estimating AP severity.

Peroxisome proliferator-activated receptor-alpha agonists repress expression of thrombin-activatable fibrinolysis inhibitor by decreasing transcript stability

Thrombin-activatable fibrinolysis inhibitor (TAFI) (carboxypeptidase B2) is a plasma zymogen that is biosynthesised in the liver and released into the circulation. Activated TAFI is a prothrombotic factor which inhibits fibrin clot lysis. Cultured human hepatoma HepG2 cells were treated with peroxisome proliferator-activated receptor (PPAR)α, β or γ agonists, and the levels of TAFI antigen and mRNA (here, termed CPB2 mRNA) were measured. HepG2 cells treated with the PPARα agonist WY14643, but not agonists for PPARβ or PPARγ, decreased their release of TAFI antigen into the conditioned medium. In parallel, there were decreased levels of CPB2 mRNA and TAFI antigen in the cells. The WY14643-mediated decrease in CPB2 mRNA levels was accelerated by overexpression of PPARα and abolished by RNA interference of PPAR A mRNA. CPB2 gene promoter activity was not influenced by treatment of the cells with WY14643. The half-life of the CPB2 transcript was shortened by treatment with WY14643 as compared with that of the control, and the decreased half-life of mRNA returned to control levels by treatment with a PPARα antagonist MK886 or transfection of PPAR A-specific siRNA to WY14643-treated HepG2 cells. The present results suggest that PPARα agonists not only play a hypolipidaemic role, but also decrease the expression of TAFI, a prothrombotic factor, by decreasing stability of CPB2 transcripts.

Plasma Thrombin-Activatable Fibrinolysis Inhibitor Levels Are not Associated With Glucose Intolerance and Subclinical Atherosclerosis in Women With Previous Gestational Diabetes

We aimed to determine plasma thrombin-activatable fibrinolysis inhibitor (TAFI) antigen levels in women with previous gestational diabetes mellitus (GDM) and to evaluate the possible association of plasma TAFI with glucose intolerance and markers of subclinical atherosclerosis. This cross-sectional study was performed in 111 women with previous GDM and 60 controls. Glucose intolerance was evaluated. Homeostasis model assessment score was calculated. Circulating lipids, interleukin-6, matrix metalloproteinase-1, fibrinogen, plasminogen activator inhibitor-1, and TAFI antigen levels were assayed. Carotid intima media thickness (IMT) was measured. Women with previous GDM had increased levels of atherosclerosis markers and carotid IMT. On the other hand, plasma TAFI antigen levels were similar (P = .395). Thrombin-activatable fibrinolysis inhibitor was not associated with the indices of insulin resistance, glucose intolerance, markers of atherosclerosis, and carotid IMT. Our data demonstrated that plasma TAFI was not altered in women with previous GDM. TAFI was not associated with glucose intolerance and subclinical atherosclerosis.

Reduced plasma fibrinolytic potential in patients with recurrent implantation failure after IVF and embryo transfer

Recurrent implantation failure (RIF) following embryo transfer (ET) is a major continuing problem in IVF. Women with haemostatic defects may be at increased risk of miscarriage and preclinical pregnancy loss. The fibrinolytic system is considered, at present, the key to new thrombotic pathogenic mechanisms. Patients with unexplained recurrent miscarriage have an impairment of fibrinolysis, as demonstrated by prolonged clot lysis time (CLT) in association with increased plasma levels of thrombin-activatable fibrinolysis inhibitor (TAFI). In this study, we investigated fibrinolytic potential in patients with RIF. Three groups of patients were studied: 30 women with RIF (RIF group), 60 patients undergoing a first successful IVF-ET cycle (IVF group) and 60 healthy fertile women (FER group). Plasma CLT was measured using a global fibrinolysis assay. TAFI antigen plasma levels and polymorphisms in the TAFI gene (+505A/G and +1542C/G) were analysed using enzyme-linked immunosorbent assay and allele-specific PCR, respectively. CLT was significantly longer (P < 0.0001 and P < 0.0009, respectively) and TAFI antigen levels were significantly higher (both P < 0.0001) in the RIF versus the IVF and FER groups. A direct relationship between CLT and TAFI antigen levels (r = 0.40; P = 0.001) was detected in the whole study population. There were no differences in distribution of TAFI polymorphisms between groups. Patients with RIF have reduced plasma fibrinolytic potential, as shown by a prolonged CLT, and this may be explained, at least in part, by increased TAFI antigen levels.

High thrombin activatable fibrinolysis inhibitor levels are associated with an increased risk of premature peripheral arterial disease

BackgroundPrevious studies suggested that hypofibrinolysis is associated with increased risk of peripheral arterial disease. Thrombin activatable fibrinolysis inhibitor (TAFI) has been identified as an important inhibitor of fibrinolysis. The aim of our study was to assess the role of TAFI in young patients with peripheral arterial disease. MethodsIn a single-center case-control study we measured plasma TAFI antigen levels and functional TAFI in consecutive young patients (men 18-45years and women 18-55years) with a first manifestation of peripheral arterial disease and compared these with a population-based control group. ResultsA total of 47 peripheral arterial disease patients and 141 controls (mean age 43) were included. Intact TAFI antigen levels were significantly higher in patients with peripheral arterial disease (112.4±21.1%) than in controls (104.9±19.9%, p=0.03). The risk of peripheral arterial disease increased with 18% (OR 1.18; CI 1.01-1.34) per 10% increase of TAFI antigen. Functional TAFI levels were slightly higher in patients compared to controls, however this difference was not significant. For individuals with the highest functional TAFI levels, above the 90th percentile, the increased risk for peripheral arterial disease was most pronounced (OR 3.1; CI 1.02-9.41). ConclusionHigh TAFI levels are associated with increased risk of premature peripheral arterial disease.

Effect of Levothyroxine Suppression Therapy on Plasma Thrombin Activatable Fibrinolysis Inhibitor Antigen Levels in Benign Thyroid Nodules

Objective: The aim of this prospective study was to investigate the effect of LT4 suppression therapy on plasma thrombin activatable fibrinolysis inhibitor (TAFI) antigen and plasminogen activator inhibitor-1 (PAI-1) levels in benign thyroid nodules. We also compared hyperthyroid patients and healthy controls. Subjects and Methods: Twenty premenopausal women with benign thyroid nodules were given LT4 suppression therapy for 1 year. Plasma TAFI and PAI-1 antigen levels were measured at baseline and after LT4 suppression treatment. The endogenous hyperthyroid group was composed of 19 premenopausal females with newly diagnosed endogenous hyperthyroidism. Eighteen age-matched euthyroid healthy premenopausal women were enrolled as the control group. Results: TAFI antigen levels decreased after LT4 suppression treatment; however, the difference was not statistically significant (p = 0.057). LT4 treatment resulted in a nonsignificant increase in PAI-1 levels. Patients with endogenous hyperthyroidism had decreased levels of TAFI antigen and increased levels of PAI-1 antigen (p < 0.05). There was a negative correlation between the FT₄ and TAFI antigen levels. Serum TSH was positively correlated with the plasma levels of TAFI antigen. Conclusion: LT4 suppression therapy for benign thyroid nodules did not result in a significant decrease in TAFI antigen levels in premenopausal women, but endogenous hyperthyroidism was associated with significantly decreased levels of TAFI antigen.

Clot lysis time and thrombin activatable fibrinolysis inhibitor in severe preeclampsia with or without associated antiphospholipid antibodies

We investigated clot lysis time, thrombin activatable fibrinolysis inhibitor antigen (TAFI) levels and TAFI gene polymorphisms in pregnant patients with severe preeclampsia, with or without associated antiphospholipid syndrome (APS). The study groups included 82 pregnant patients without antiphospholipid antibodies with severe preeclampsia (PE group) and 10 pregnant APS patients who developed severe preeclampsia (APS-PE group). Controls included 76 primary pregnant APS patients (APS group) and 89 healthy pregnant patients (NOR group) with uneventful term pregnancy and delivery. Patients in the APS-PE, APS and NOR groups were sampled during each trimester of pregnancy and at 4-6 months and 12 months after delivery. Patients in the PE group were sampled during the third trimester and after delivery. Significantly prolonged clot lysis time after delivery was found in the PE, APS-PE and APS groups compared to the NOR group. The PE and APS-PE groups had longer clot lysis time than the APS group. Levels of TAFI were found to be higher after delivery in patients of the PE and APS-PE groups compared to the APS and NOR groups. Allele distribution of the TAFI gene polymorphisms was similar among the four study groups. We conclude that increased TAFI antigen levels and impaired fibrinolysis are pathogenetic factors in preeclampsia, regardless of whether or not preeclampsia is associated with the presence of antiphospholipid antibodies.