Factor IX and thrombosis

A study of recurrent life-threatening thrombosis accompanied with the duplication of the factor IX gene

Hereditary predisposition play an important role in thrombosis, especially in younger patients. Here we studied a young patient who experienced three different episodes of severe thromboses, some of which were life-threatening (pulmonary artery thrombosis, portal and mesenteric vein thrombosis, and arterial thrombosis of the lower leg). Blood levels of clotting related indicators were assessed. We screened 35 genes linked to thrombosis. We discovered a 756 kb duplication that spanned the F9 gene in region q27.1 of the X chromosome. The repeat includes the full F9 gene, thus, the patient had two functional copies of FIX with the FIX activity 192%. An identical repetition was found in the patient's mother. Both the patient and his mother had high, but variable, plasma FIX activities that promote coagulation. The patient's frequent, severe thrombolic events maybe attributed to the duplication of a big portion of the F9 gene and lupus anticoagulant positive.

A novel factor IXa-specific enzyme-linked immunosorbent assay detects factor IXa in human plasma

Background

Factor (F)IXa activity has been detected in human plasma and may impact thrombotic risk. Current FIXa activity assays are complex and cumbersome.

Objectives

To develop a reproducible enzyme-linked immunosorbent assay (ELISA) using a novel monoclonal antibody that detects total FIXa in human plasma.

Methods

A monoclonal antibody was raised against the new N-terminus exposed upon activation of FIX to FIXa by cleavage after R226. This antibody is specific for FIXa protease and does not recognize FIX zymogen or FIXα. The antibody was used to develop a FIXa-specific ELISA capable of quantifying total FIXa (free FIXa and FIXa-antithrombin complex) in human plasma. Total FIXa quantified using the ELISA was compared to that of FIXa-antithrombin quantified using modifications of a previously described ELISA.

Results

The FIXa-specific ELISA was reproducible and quantified total FIXa in human plasma. Total FIXa levels correlated with FIXa-antithrombin levels.

Conclusion

A monoclonal antibody was developed that specifically detects human FIXa protease. A FIXa-specific ELISA using the new antibody is capable of reproducibly measuring total FIXa in human plasma (both free FIXa and FIXa-antithrombin). This assay should facilitate the evaluation of total FIXa levels in a variety of clinical circumstances.

Prothrombin Time and Coagulation Factor IX as Hemostatic Risk Markers for Legg- Calvé-Perthes Disease

BACKGROUND

Legg-Calvé-Perthes disease (LCPD) is a pediatric disorder that occurs due to the avascular necrosis of the femoral head and affects the range of motion of the hip in various degrees. Its etiology is still unknown, although it has been associated with coagulation abnormalities, however, the lack of reproducibility in the results in various studies has created a controversy as to whether hemostasis disorders are related to LCPD. On the other hand, there is little information on laboratory studies that could facilitate the diagnosis and treatment of LCPD.

METHODS

Blood and plasma samples were tested from 25 patients with LCPD and 50 healthy controls, matched by sex and age. Cellular markers were evaluated through complete blood count, as well as coagulation times, coagulation factors activity, antithrombotic proteins, and homocysteine concentration.

RESULTS

After assessing activity value frequencies in each group, the results showed more significant activity in some of the biological risk markers of thrombophilia, presenting a substantial difference in prothrombin time↘, FV↗, FVIII↗, FIX↗, and Hcy↗. These values imply that there may be hypercoagulable states in patients, which can cause thrombotic events.

CONCLUSIONS

Diminished prothrombin time and increase in FV activity, FVIII, FIX, and Hcy concentration support the hypothesis that microthrombi formation in small-caliber vessels could be causing avascularity and femoral necrosis, which are traits of LCPD. In addition, based on our results, we believe that the laboratory studies carried out are very useful in the diagnosis and treatment of LCPD.

SERPINE1 rs6092 Variant Is Related to Plasma Coagulation Proteins in Patients with Severe COVID-19 from a Tertiary Care Hospital

An impaired coagulation process has been described in patients with severe or critical coronavirus disease (COVID-19). Nevertheless, the implication of coagulation-related genes has not been explored. We aimed to evaluate the impact of F5 rs6025 and SERPINE1 rs6092 on invasive mechanical ventilation (IMV) requirement and the levels of coagulation proteins among patients with severe COVID-19. Four-hundred fifty-five patients with severe COVID-19 were genotyped using TaqMan assays. Coagulation-related proteins (P-Selectin, D-dimer, P-selectin glycoprotein ligand-1, tissue plasminogen activator [tPA], plasminogen activator inhibitor-1, and Factor IX) were assessed by cytometric bead arrays in one- and two-time determinations. Accordingly, SERPINE1 rs6092, P-Selectin (GG 385 pg/mL vs. AG+AA 632 pg/mL, p = 0.0037), and tPA (GG 1858 pg/mL vs. AG+AA 2546 pg/mL, p = 0.0284) levels were different. Patients carrying the CT F5-rs6025 genotype exhibited lower levels of factor IX (CC 17,136 pg/mL vs. CT 10,247 pg/mL, p = 0.0355). Coagulation proteins were also different among IMV patients than non-IMV. PSGL-1 levels were significantly increased in the late stage of COVID-19 (>10 days). The frequencies of F5 rs6025 and SERPINE1 rs6092 variants were not different among IMV and non-IMV. The SERPINE1 rs6092 variant is related to the impaired coagulation process in patients with COVID-19 severe.

The Diagnostic Values of Ischemia-Modified Albumin in Patients with Acute Abdominal Pain and Its Role in Differentiating Acute Abdomen

Aim

The aim of this study was to evaluate the diagnostic value of serum ischemia-modified albumin (IMA) levels in patients presenting to the emergency department with acute abdominal pain and its use in differentiating acute surgical abdomen.

Methods

This single-center prospective cross-sectional study included 334 adult patients who presented to the emergency department. These consisted of 194 patients (Group 1) with nontraumatic abdominal pain commencing in the preceding week, who were definitely diagnosed and either hospitalized in a specific department or planned for discharge, and a control group of 140 patients (Group 2).

Results

The mean IMA value of the patients diagnosed with acute appendicitis was statistically significantly higher than that of the control group. The mean IMA value of the patients diagnosed with acute appendicitis, ovarian pathologies, and gastritis-peptic ulcer was statistically significantly higher than that of the nonspecific abdominal pain group.

Conclusion

Serum IMA levels can be used as a diagnostic marker in patients with acute appendicitis. Furthermore, serum IMA levels in patients presenting to the emergency department with abdominal pain may be indicative of patients requiring surgery or of complicated cases, particularly in terms of acute appendicitis and ovarian pathologies.

Screening and analysis of small molecular peptides in urine of gestational diabetes mellitus

Gestational diabetes mellitus (GDM) is a common clinical disease with complicated clinical process and harmful effects on pregnant women and fetus. The purpose of this study is to use the convenient urine samples in combination with glucose levels to detect or predict GDM. In this study, urine samples of non-pregnant women, normal pregnant women and GDM patients were collected. The peptides in urine were enriched by weak cationic exchange magnetic beads (MB-WCX) and analyzed by matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS). 46 polypeptide peaks with statistical difference (P < 0.01) were screened out by using Bioexplorer analysis software. The level of molecules with mass-to-charge ratio of 1079.2, 1290.6 and 1500.7 was higher in the GDM group than the other two groups. Through the analysis of differential molecules by liquid chromatography tandem mass spectrometry (LC-MS), the above molecules were identified as coagulation factor IX, TBC1 family member 5 isoform a [Homo sapiens] (TBC1D5a) and immunoglobulin kappa constant. The discovery of polypeptides provides the research basis for further primary screening and assistant diagnosis of GDM through urine samples.

Combined Coagulopathy Can Induce Both Hemorrhagic and Thrombotic Complications in Multiple Myeloma

Coagulation abnormalities are a rare but critical complication associated with plasma cell diseases. We herein present a case of multiple myeloma (MM) with complicated coagulopathy. Initially, the patient showed severe bleeding tendency due to concomitant acquired hemophilia A and acquired von Willebrand syndrome. Interestingly, the patient also exhibited hyperactivation of factor IX. During treatment for MM, the bleeding complications were ameliorated; however, the patient had central retinal vein occlusion. All of the coagulation abnormalities were completely resolved after the complete remission of MM. This case suggests that MM patients may have concomitant risks for both bleeding and thromboembolic complications.

Padua FIXa resistance to Protein S and a potential therapy for hyperactive FIXa

INTRODUCTION

Abnormalities in the levels and functions of proteins that maintain hemostasis can cause thrombosis. Factor IX (FIX) R338L, i.e., Factor IX Padua, is a hyperactive clotting factor that promotes thrombosis. The R338L mutation increases the clotting rate by 8-fold despite increasing the Factor IXa enzymatic activity by only 2-fold. Protein S (PS) is a natural anticoagulant that directly inhibits FIXa. Because individuals affected by the R338L mutation have normal concentrations of PS, we speculated that the Padua hypercoagulation phenotype is due to decreased inhibition of FIXa R338L by PS.

METHODS

We measured the ability of PS to inhibit FIX R338L, and we assessed the ability of PS to mitigate the prothrombotic effect FIX R338L.

RESULTS

Plasma clotting assays demonstrated that 3-fold more PS was required to inhibit FIXa R338L compared with inhibition of wild type FIXa. Thrombin generation assays with Padua patient plasma recapitulated this biochemical consequence of the R338L mutation. Importantly, the less efficient inhibition of FIXa R338L was reversed by increasing PS concentration. Binding and co-immunoprecipitation studies revealed that the decrease in the inhibition of FIXa R338L by PS was caused by a 3- to 4-fold reduction in FIXa R338L affinity for PS.

CONCLUSION

In summary, the resistance of FIXa R338L to inhibition by PS likely contributes to the unexpectedly high clotting rate in Padua individuals. Moreover, PS-mediated reversal of the pathological properties of FIXa R338L suggests that PS administration may be a novel and effective means to mitigate thrombophilia caused by any source of elevated FIXa activity.

Diagnosing human blood clotting deficiency

There are different clotting factors present in blood, carries the clotting cascade and excessive bleeding may cause a deficiency in the clotting Diagnosis of this deficiency in clotting drastically reduces the potential fatality. For enabling a sensor to detect the clotting factors, suitable probes such as antibody and aptamer have been used to capture these targets on the sensing surface. Two major clotting factors were widely studied for the diagnosis of clotting deficiency, which includes factor IX and thrombin. In addition, factor IX is considered as the substitute for heparin and the prothrombotic associated with the increased thrombin generation are taking into account their prevalence. The biosensors, surface plasmon resonance, evanescent-field-coupled waveguide-mode sensor, metal-enhanced PicoGreen fluorescence and electrochemical aptasensor were well-documented and improvements have been made for high-performance sensing. We overviewed detecting factor IX and thrombin using these biosensors, for the potential application in medical diagnosis.

Development of aptamer oligonucleotides as anticoagulants and antithrombotics for cardiovascular diseases: current status

Aptamers are short DNA/RNA oligonucleotides selected by a process known as Systematic Evolution of Ligands by Exponential Enrichment (SELEX) based on affinity for target molecules. Since aptamers have several advantages over monoclonal antibodies, such as high specificity and affinity, flexible modification and stability, and lack of toxicity and immunogenicity, they are promising novel diagnostic and therapeutic agents. In this review, we will describe the development of aptamers against thrombin, von Willebrand factor (vWF), factor IX, and factor XII as potential anticoagulants or antithrombotics for cardiovascular diseases, especially those that have entered clinical trials.

Elevated factor IX activity is associated with an increased odds ratio for both arterial and venous thrombotic events

OBJECTIVES

Elevations of factor IX (FIX) are thought to contribute to thrombotic risk, but this has not been well characterized. We retrospectively sought to determine whether elevated FIX levels are a risk factor for thrombosis in 81 adult subjects younger than 65 years (mean, 47 years) who were referred for evaluation of a hypercoagulable state.

METHODS

Patients were classified by arterial transient ischemic attack/stroke (TIA/stroke, n = 62) or venous thromboembolism (VTE, n = 19) events. FIX activity testing was performed on all 81 subjects and a reference group of 40 healthy individuals.

RESULTS

Thirteen (21%) of 62 subjects with TIA/stroke and 5 (26%) of 19 subjects with VTE had elevated FIX activity. Odds ratios for TIA/stroke and VTE in subjects with elevated FIX activity were 3.7 (95% confidence interval [CI], 0.76-17.65) and 6.8 (95% CI, 1.18-39.07), respectively.

CONCLUSIONS

Our findings suggest an association between elevated FIX levels and both arterial and venous thrombotic events.

Changes in haemostatic and platelet activation markers in non-dipper hypertensive patients

BACKGROUND

Non-dipper hypertensive patients are at increased risk for cardiovascular disease. Coagulation and fibrinolysis activation factors are considered as risk factors for cardiovascular disease. The aim of this study was to examine the relationship between the haemostatic and platelet activation markers and the non-dipping pattern in treated hypertensive patients.

PATIENTS AND METHODS

Seventy-one treated hypertensive patients (53 with essential and 18 with secondary hypertension, due to chronic kidney disease-stage 4), aged 33 to 81 years (30 men), were classified as dippers and non-dippers, according to the presence or absence, respectively, of a decline of nocturnal average systolic blood pressure (BP) by more than 10% of the diurnal BP (non-dipping pattern) on 24-hour ambulatory BP monitoring. Plasma levels of factors VIII and IX, fibrinogen, prothrombin fragment 1 + 2, thrombin-antithrombin complex, protein C, plasmin-alpha-2 antiplasmin complex, D-dimer and platelet factor 4 were measured in all patients.

RESULTS

Thirty-seven patients were classified as dippers and 34 as non-dippers. The percentages of patients with essential and with secondary hypertension were similar in the dippers and in the non-dippers groups (both P = 0.754). Multivariate analysis of variance showed statistically significant differences in all measured variables between dippers and non-dippers (P = 0.043). Plasma levels of factors VIII and IX, fibrinogen, prothrombin fragment 1 + 2, protein C, plasmin-alpha-2-antiplasmin complex, and D-dimers were significantly higher in non-dippers when compared to dippers (P < 0.05 for all). In contrast, there were no significant differences in plasma levels of thrombin-antithrombin complex (P = 0.955) and platelet factor 4 (P = 0.431) between the two groups.

CONCLUSION

This study provides evidence that non-dipper treated hypertensive patients exhibit alterations in haemostasis, which may affect their cardiovascular risk.

Correlation of factor IXa subsite modulations with effects on substrate discrimination

BACKGROUND

A key feature of factor IXa is its allosteric transformation from an enzymatically latent form into a potent procoagulant. Although several small molecules have been found to be capable of partially affecting FIXa function (i.e. ethylene glycol, Ca(2+), and low molecular weight heparin [LMWH]), the resulting modest changes in peptidolytic activity have made the study of their mechanisms of action challenging. As these effects provide hints about potential regulatory forces that may be operational in the full expression of FIXa coagulant activity, their description remains of great interest. Studies of crystal structures have yielded insights into the structural changes induced by these effectors, but there remains a paucity of information to correlate any given structural change with specific consequences for FIXa function.

OBJECTIVES

To correlate structural changes induced by these modulators with defined consequences for FIXa substrate discrimination and function.

METHODS

A peptidomics-based mass spectrometry (MS) approach was used to examine the patterns of hydrolysis of four combinatorial chemistry-derived pentapeptide libraries by FIXa under various conditions in a soluble, active enzyme system.

RESULTS

Ethylene glycol specifically altered the S3 subsite of FIXa to render it more tolerant to side chains at the P3 substrate position, whereas Ca(2+) enhanced tolerance at the S2 subsite. In contrast, LMWH altered both the S2 and S1' subsites.

CONCLUSIONS

These results demonstrate the role of plasticity in regulating FIXa function with respect to discrimination of extended substrate sequences, as well as providing crucial insights into active site modulations that may be capitalized on by various physiologic cofactors of FIXa and in future drug design.

Aptamers as therapeutics in cardiovascular diseases

With many advantages over other therapeutic agents such as monoclonal antibodies, aptamers have recently emerged as a novel and powerful class of ligands with excellent potential for diagnostic and therapeutic applications. Typically generated through Systematic Evolution of Ligands by EXponential enrichment (SELEX), aptamers have been selected against a wide range of targets such as proteins, phospholipids, sugars, nucleic acids, as well as whole cells. DNA/RNA aptamers are single-stranded DNA/RNA oligonucleotides (with a molecular weight of 5-40 kDa) that can fold into well-defined 3D structures and bind to their target molecules with high affinity and specificity. A number of strategies have been adopted to synthesize aptamers with enhanced in vitro/in vivo stability, aiming at potential therapeutic/diagnostic applications in the clinic. In cardiovascular diseases, aptamers can be developed into therapeutic agents as anti-thrombotics, anti-coagulants, among others. This review focuses on aptamers that were selected against various molecular targets involved in cardiovascular diseases: von Willebrand factor (vWF), thrombin, factor IX, phospholamban, P-selectin, platelet-derived growth factor, integrin α(v)β(3), CXCL10, vasopressin, among others. With continued effort in the development of aptamer-based therapeutics, aptamers will find their niches in cardiovascular diseases and significantly impact clinical patient management.

Pegnivacogin results in near complete FIX inhibition in acute coronary syndrome patients: RADAR pharmacokinetic and pharmacodynamic substudy

AIMS

Establishing factor IX inhibition in patients with acute coronary syndrome/non-ST-elevation myocardial infarction (ACS/NSTEMI), a setting characterized by increased factor IX activity, is critical to investigate the REG1 system in this target population. The REG1 system (Regado Biosciences, Basking Ridge, NJ) consists of pegnivacogin (RB006), an RNA aptamer that directly inhibits factor IXa, and anivamersen (RB007), its complementary control agent.

METHODS AND RESULTS

RADAR is a Phase 2b study investigating the use of pegnivacogin in patients (n = 800) with ACS undergoing planned early cardiac catheterization. To validate dose selection and stability of anticoagulation throughout the time of cardiac catheterization at an early stage of the clinical trial, 33 patients, 22 of whom had not received recent prior heparin, underwent thorough pharmacokinetic and pharmacodynamic assessment. Fold prolongation of activated partial thromboplastin time (aPTT) was used to impute factor IX inhibition. Pegnivacogin 1 mg/kg rapidly achieved a high pegnivacogin plasma concentration (26.1 ± 4.6 µg/mL), prolonged the aPTT (mean aPTT 93.0 ± 9.5 s), and approached near complete factor IX inhibition (mean fold increase from baseline 2.9 ± 0.3). These levels remained stable from the time of drug administration through completion of the catheterization.

CONCLUSION

Pegnivacogin administered at a weight-adjusted dose of 1 mg/kg consistently achieves a high level of factor IX activity inhibition among patients with ACS and provides stable anticoagulation during cardiac catheterization. These findings support the dose of pegnivacogin selected for the RADAR study.

Factor IXa as a target for pharmacologic inhibition in acute coronary syndrome

Anticoagulant therapy, combined with platelet-directed inhibitors, represents a standard-of-care in the management of patients with acute coronary syndrome, particularly those who require percutaneous coronary interventions. While a vast clinical experience, coupled with large clinical trials have collectively provided guidance, an optimal anticoagulant drug and applied strategy, defined as one that reduces thrombotic and hemorrhagic events consistently, with minimal off-target effects and active control of systemic anticoagulation according to patient and clinical-setting specific need, remains at large. An advancing knowledge of coagulation, hemostasis, and thrombosis suggests that factor IXa, a protease that governs thrombin generation in common thrombotic disorders may represent a prime target for pharmacologic inhibition.

First clinical application of an actively reversible direct factor IXa inhibitor as an anticoagulation strategy in patients undergoing percutaneous coronary intervention

BACKGROUND

The ideal anticoagulant should prevent ischemic complications without increasing the risk of bleeding. Controlled anticoagulation is possible with the REG1 system, an RNA aptamer pair comprising the direct factor IXa inhibitor RB006 and its active control agent RB007.

METHODS AND RESULTS

This phase 2a study included a roll-in group (n=2) treated with REG1 plus glycoprotein IIb/IIIa inhibitors followed by 2 groups randomized 5:1 to REG1 or unfractionated heparin. In group 1 (n=12), RB006 was partially reversed with RB007 after percutaneous coronary intervention and fully reversed 4 hours later. In group 2 (n=12), RB006 was fully reversed with RB007 immediately after percutaneous coronary intervention. Femoral sheaths were removed after complete reversal. Patients were pretreated with aspirin and clopidogrel. End points included major bleeding within 48 hours; composite of death, myocardial infarction, or urgent target vessel revascularization within 14 days; and pharmacodynamic measures. All cases were successful, with final Thrombolysis in Myocardial Infarction grade 3 flow and no angiographic thrombotic complications. There were 2 ischemic end points in the REG1 group and 1 in the unfractionated heparin group, with 1 major bleed in the unfractionated heparin group. Median activated clotting time values rose from 151 to 236 seconds after RB006. Administration of the partial RB007 dose reversed anticoagulation to an intermediate activated clotting time value of 186 seconds. Complete reversal with RB007 returned the median activated clotting time value to 144 seconds. Both reversal strategies enabled scheduled femoral sheath removal.

CONCLUSIONS

This study demonstrates the clinical translation of a novel platform of anticoagulation targeting factor IXa and its active reversal to percutaneous coronary intervention and provides the basis for further investigation.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00715455.

Impact of thrombogenic mutations on clinical phenotypes of von Willebrand disease

von Willebrand disease (VWD) is a most common inherited bleeding disorder. von Willebrand factor (VWF) exists as an extracellular adaptor molecule and generally involves in the hemostasis mechanism through binding with GP (Glycoprotein) Ib-IX-V platelet receptor. Clinical phenotype of bleeding disorders modulated to a decrease in bleeding symptoms by thrombogenic mutations. We made an attempt to investigate the impact of thrombogenic mutations/polymorphisms on the clinical phenotype of 114 different types of patients with VWD, and 120 healthy controls were screened for methylenetetrahydrofolate reductase (MTHFR) 677C/T, factor V (FV) Leiden (1691G/A), beta(3) integrin (HPA-I) (Human platelets antigen-I) gene (1565T/C), and prothrombin 20210G/A mutations. Genotypic analysis was performed using polymerase chain reaction (PCR) and restriction fragment length polymorphism. Forty-five patients (39.5%) were found to be positive for at least one of the prothrombotic risk factors screened. Prothrombin 20210G/A was not found in any patient with VWD as well as healthy control. Eight patients with VWD were carrying the defective alleles of different thrombogenic markers, showing milder phenotypes than expected. A high prevalence was observed for MTHFR 677C/T (677C/C 73.6%, 677C/T 24.6%, 677T/T 1.8%) and PLA1/A2 (1565T/T 88.6%, 1565T/C 10.5%, 1565C/C 0.87%) polymorphism followed by FV Leiden (1691G/G 97.4%, 1691G/ A 2.6%, 1691A/A 0.00%) in patients with VWD with allelic frequencies 11.4% (677T), 5% (1565C), and 1.3% (1691A). Hence, we concluded that thrombophilic markers were seen to be influencing the clinical phenotypes of patients with VWD.

Factor IX and deep vein thrombosis

Elevated levels of several coagulation factors have been found to be associated with an increased risk of thrombosis. In this perspective article, Dr. Lowe examines the implications of the report by Bezemer and coworkers in this issue for our understanding of the mechanisms involved and how they should direct future research.

F9 Malmö, factor IX and deep vein thrombosis

BACKGROUND

We recently reported the association between the Malmö sequence variant in F9 (rs6048) and deep vein thrombosis.

DESIGN AND METHODS

We aimed to study whether the association between F9 Malmö and deep vein thrombosis is explained by linkage disequilibrium with nearby single-nucleotide polymorphisms, and whether the association is explained biologically by F9 Malmö affecting factor IX antigen levels or activation of factor IX. We investigated the association of F9 Malmö and 28 nearby single-nucleotide polymorphisms with deep vein thrombosis in men from two case-control studies, LETS (n=380) and MEGA (n=1,469). We assessed the association of F9 Malmö with factor IX antigen level in male control subjects from LETS (n=191) and two subsets of MEGA (n=823 and n=484) and the association with endogenous thrombin potential in LETS control men. We studied the association between F9 Malmö and factor IX activation peptide in 1,199 healthy middle-aged men from the NPHS-II cohort.

RESULTS

In the combined LETS and MEGA studies, the odds ratio (95% confidence interval) for the G allele of F9 Malmö, compared with the A allele, was 0.80 (0.69-0.93). One single-nucleotide polymorphism in F9, rs422187, was strongly linked to F9 Malmö (r(2)=0.94) and was similarly associated with deep vein thrombosis. No other single-nucleotide polymorphism or haplotype tested was more strongly associated. Factor IX antigen level, factor IX activation peptide levels and endogenous thrombin potential did not differ between F9 Malmö genotypes.

CONCLUSIONS

The F9 Malmö sequence variant was the most strongly associated with deep vein thrombosis among common single-nucleotide polymorphisms in the region. However, the biological mechanism by which F9 Malmö affects risk remains unknown.

Variability in bleeding phenotype in Amish carriers of haemophilia B with the 31008 C-->T mutation

The aim of this study was to characterize the variability of bleeding phenotype and its association with plasma factor IX coagulant activity (FIX:C) in haemophilia B carriers in a large Amish pedigree with a unifying genetic mutation, C-to-T transition at base 31008 of the factor IX gene (Xq27.1-27.2). A cross-sectional survey of haemophilia B carriers included a multiple choice questionnaire evaluating symptoms of mucocutaneous bleeding, joint bleeding and bleeding after haemostatic stress [menstruation, postpartum haemorrhage (PPH), dental extractions and invasive surgeries]. Severity of bleeding was graded as 0 to 4, 0 being no bleeding whereas 4 being severe bleeding. Association between total bleeding scores and the FIX:C was evaluated. Sixty-four haemophilia B carriers participated in this study. Median age: 18 years (range 1-70 years); median bleeding score: 1 (range 0-8). Besides PPH, isolated symptoms of bruising, epistaxis, menorrhagia and postsurgical bleeding including dental extraction were not associated with lower FIX:C. Bleeding score >/=3 was associated with involvement of at least two bleeding sites and a lower mean FIX:C of 42 +/- 10.3% (95% CI 36.4-47.7) while a score >3 had involvement of </=2 sites and higher mean FIX:C of 54.9 +/- 21.5% (95% CI 49-61), P = 0.005. Subcutaneous haematoma formation and bleeding after haemostatic stress requiring treatment were associated with bleeding scores >/=3. Phenotypic variability existed among the carriers of haemophilia B who belonged to a single pedigree carrying a single unifying mutation. The utility of bleeding scores to define bleeding phenotype precisely in haemophilia B carriers needs further evaluation.

Arterial and venous thrombosis in rare congenital bleeding disorders: a critical review

A thorough review of the literature and of personal files has allowed the gathering of 81 patients with rare congenital bleeding disorders and thrombotic phenomena. Sixteen of these patients had congenital afibrinogenemia, eight involved factor V deficiency, 20 factor VII defects, 33 factor XI deficiencies and only one, a factor XIII defect. Altogether 42 patients showed arterial thrombosis (myocardial infarction [MI] in 28 cases; ischemic stroke in 4; arterial occlusion in 8; 2 patients with disseminated intravascular coagulation (DIC)). Ages varied between 13 and 74. Twenty-two patients were males and 16 females. In four cases, sex was not reported. There were three fatalities: two after a MI and one because of heart failure. With regard to venous thrombosis: 9 patients had pulmonary embolism, 15 patients had deep vein thrombosis, 9 patients had both pulmonary embolism and deep vein thrombosis; 1 patient had superficial vein thrombosis, whereas, 5 cases had an unusual site venous thrombosis (two portal systems, two cerebral sinuses, one inferior vena cava) for a total of 39 cases. Age varied between 3 and 86. In this case, 20 patients were males and 17 were females. In two cases, sex was not reported. There were three fatalities: two because of pulmonary embolism and one because of inferior vena cava thrombosis. The fact that thrombosis has never been described in patients with factor II or factor X seems to underscore the central antithrombotic role that these two factors have in the coagulation system.

Non-catheter associated venous thrombosis in hemophilia A and B. A critical review of all reported cases

All reported cases of non-catheter induced venous thrombosis in patients with hemophilia A or B have been carefully evaluated. A total of 27 cases were reported,12 patients with hemophilia A and 15 patients with hemophilia B. The age of patients varied between 9 and 67 years. There were 10 cases of deep vein thrombosis, 8 patients with pulmonary embolism accompanied or not by deep vein thrombosis, 5 cases of superficial vein thrombosis. In addition, there were 3 cases of thrombosis in unusual sites (1 retinal central vein thrombosis and 2 portal vein thrombosis). Finally, in one case, venous thrombosis was multiple. There was a fatality in a hemophilia B patient with pulmonary embolism. The most frequent risk or triggering factor in hemophilia A was the administration of Feiba or rFVIIa concentrates in patients with inhibitors. Surgery together with Prothrombin Complex concentrates was the most frequent cause in hemophilia B patients. Congenital associated prothrombotic risk factors were present in two patients. No or very few therapeutic procedures were initiated in these patients but for a suspension or reduction of concentrates infusion. In a few instances low molecular weight heparin was given for a few days. The frequent association of venous thrombosis with infusion of concentrates indicates the need for a careful evaluation of patients about to receive such therapy.

Shape-shifting serpins--advantages of a mobile mechanism

Serpins use an extraordinary mechanism of protease inhibition that depends on a rapid and marked conformational change and causes destruction of the covalently linked protease. Serpins thus provide stoichiometric, irreversible inhibition, and their dependence on conformational change is exploited for signalling and clearance. The regulatory advantages provided by structural mobility are best illustrated by the heparin activation mechanisms of the plasma serpins antithrombin and heparin cofactor II. This mechanistic complexity, however, renders serpins highly susceptible to disease-causing mutations. Recent crystal structures reveal the intricate conformational rearrangements involved in protease inhibition, activity modulation and the unique molecular pathology of the remarkable shape-shifting serpins.

Genetic determinants of normal variation in coagulation factor (F) IX levels: genome-wide scan and examination of the FIX structural gene

BACKGROUND

High-normal and elevated plasma FIX activity (FIX:C) levels are associated with increased risk for venous- and possibly arterial-thrombosis.

OBJECTIVE

Because the broad normal range for FIX:C involves a substantial unknown genetic component, we sought to identify quantitative-trait loci (QTLs) for this medically important hemostasis trait.

METHODS

We performed a genome-wide screen and a resequencing-based variation scan of the known functional regions of every distinct FIX gene (F9) in the genetic analysis of idiopathic thrombophilia project (GAIT), a collection of 398 Spanish-Caucasians from 21 pedigrees.

RESULTS

We found no evidence for linkage (LOD scores <1.5) despite genotyping more than 540 uniformly-spaced microsatellites. We identified 27 candidate F9 polymorphisms, including three in cis-elements responsible for the increase in FIX:C that occurs with aging, but found no significant genotype-specific differences in mean FIX:C levels (P-values > or = 0.11) despite evaluating every polymorphism in GAIT by marginal multicovariate measured-genotype association analysis.

CONCLUSIONS

The heritable component of interindividual FIX:C variability likely involves a collection of QTLs with modest effects that may reside in genes other than F9. Nevertheless, because the alleles of these 27 polymorphisms exhibited a low overall degree of linkage disequilibrium, we are currently defining their haplotypes to interrogate several highly-conserved non-exonic sequences and other F9 segments not examined here.

The metabolic syndrome and insulin resistance: relationship to haemostatic and inflammatory markers in older non-diabetic men

AIMS

We have examined the cross-sectional relationship between insulin resistance, the metabolic syndrome and haemostatic and inflammatory markers.

METHODS AND RESULTS

We carried out the study in 2722 non-diabetic men aged 60-79 years with no history of coronary heart disease or stroke and who were not on warfarin treatment, drawn from general practices in 24 British towns. Insulin resistance (HOMA) was significantly associated with increased inflammatory markers (C-reactive protein (CRP), white cell count), coagulation factors VII-IX, von Willebrand factor (VWF) and tissue plasminogen activator (t-PA) antigens (markers of endothelial dysfunction) and blood viscosity after adjustment for age, smoking, physical activity, alcohol intake and waist circumference. Relationships with fibrinogen and fibrin D-dimer were weak. The relationship between HOMA and CRP was abolished after adjustment for t-PA. The prevalence of the metabolic syndrome was similar using World Health Organization (WHO) and National Cholesterol Education Program definitions (26.7% and 27.0%) but associations between the metabolic syndrome and increased haemostatic markers, particularly for raised factor VIII and VWF were stronger using WHO criteria.

CONCLUSION

Insulin resistance and the metabolic syndrome showed significant associations with markers of haemostasis and inflammation, which may be relevant to their associations with cardiovascular disease.

Prevalence and risk factors for heart disease among males with hemophilia

There have been conflicting reports in the literature about the protective effect of hemophilia on the occurrence of ischemic heart disease (IHD). Circulatory disease has been reported as the second most common cause of death in persons with hemophilia in the United States. In addition to diabetes and hypertension, high levels of FVIII, as may occur during factor concentrate infusions, may increase IHD risk in this population. To estimate the prevalence of heart disease and examine factors associated with IHD and other heart diseases among persons with hemophilia, we analyzed data collected from the medical records of 3,422 males with hemophilia living in six U.S. states from 1993 to 1998. Heart disease cases were ascertained from among 2,075 persons who were hospitalized at least once during the 6-year period. Of these, 48 were diagnosed with IHD and 106, with other types of heart disease. The age-specific prevalence of IHD ranged from 0.05% in those under 30 years to 15.2% in those 60 years or older. Hospital discharge rates in males with hemophilia with IHD and other types of heart disease were lower compared to rates in age-matched U.S. males. In our cohort, as in the general population, IHD was independently associated with age, hypertension, diabetes, and hyperlipidemia. Other heart diseases were associated with HIV infection, hypertension, hemophilia B, and diabetes. In summary, persons with hemophilia have unique risk factors such as infusion of factor concentrates and infection with HIV that may predispose them to heart disease as their life expectancy increases.

Hormone replacement therapy and cardiovascular disease: increased risks of venous thromboembolism and stroke, and no protection from coronary heart disease

Hormone replacement therapy (HRT) was increasingly promoted over the last 40 years to improve quality of life, and to reduce the risks of osteoporotic fractures and coronary heart disease (CHD). In recent years, observational studies, randomized trials and systematic reviews of such trials have shown that HRT does not reduce, but actually increases cardiovascular risk. HRT increases the relative risks of venous thromboembolism (twofold), and of fatal or disabling stroke (by 50%); whilst increasing the early risk of myocardial infarction and having no protective effect against CHD on longer term use. Possible mechanisms for these increased cardiovascular risks include down-regulation of several inhibitory pathways of blood coagulation, resulting in increased coagulation activation, which promotes venous and arterial thrombosis. The implications for prescription are discussed, as are lessons for future evaluation of health care interventions.

Insulin resistance, haemostatic and inflammatory markers and coronary heart disease risk factors in Type 2 diabetic men with and without coronary heart disease

AIMS/HYPOTHESIS

We have examined markers of haemostasis and inflammation in men with diabetes, coronary heart disease (CHD) or both, and assessed their associations with insulin resistance in men with Type 2 diabetes.

METHODS

The study was carried out in 4066 British men aged 60 to 79 years who were not on warfarin or insulin, of whom there were 426 men with prevalent Type 2 diabetes and 842 with prevalent CHD.

RESULTS

Men with Type 2 diabetes were more likely to have multiple risk factors and higher levels of haemostatic and inflammatory markers than men without, irrespective of CHD status. Compared with men with CHD only, men with diabetes only showed increased levels of tissue plasminogen activator antigen, increased plasma and blood viscosity, and increased levels of coagulation factors VII, VIII and IX. They also had dyslipidaemia. In men with diabetes, increased insulin resistance (homeostasis model assessment, HOMA) was associated with increased levels of haemostatic markers and dyslipidaemia. The prevalence of CHD increased significantly with increasing tertiles of HOMA (adjusted odds ratio 1.32 [95% CI: 0.72-2.42] in the second, and 1.70 [95% CI: 0.92-3.44] in the third tertile; p=0.04 for trend).

CONCLUSIONS/INTERPRETATION

Increased insulin resistance among men with Type 2 diabetes is associated with increased prevalence of CHD and of activated haemostasis and dyslipidaemia. Reducing insulin resistance in men with diabetes may reduce their tendency to develop thrombosis and hence CHD risk.

Identification of prothrombin as a major thrombogenic agent in prothrombin complex concentrates

Prothrombin complex concentrates (PCC) were compared in an in vitro test system for thrombogenicity (thrombin generation assay) employing plasma from coumarin-treated patients. Among these concentrates one had a proven history of thrombogenicity, whereas the remainder did not cause such fatal casualties in the past. Investigations into the thrombogenic component were performed by spiking experiments in which we biased a typical PCC without reported thromboembolic complications into one with a performance in the thrombin generation assay like that with a proven history of thrombogenicity. Hereby, it was possible to identify prothrombin as the most plausible thrombogenic component. Additional experiments performed with anticoagulant components (antithrombin together with heparin) resulted in a perfect reversal of the observed in vitro thrombogenicity. Our in vitro observations corroborate on an experimental basis the widespread medicinal usage of antithrombin administration as a regimen for the avoidance of thromboembolic complications during treatment with PCC and related products, and vice versa. Our observation casts doubts upon the widely accepted idea of activated factor IX as the thromboembolic agent in PCC. Also, our finding may be taken as an example for the feasibility of this test system as an in vitro model for thrombogenicity.

Identification of hepatic molecular mechanisms of action of alpha-tocopherol using global gene expression profile analysis in rats

The recent discovery that vitamin E (VE) regulates gene activity at the transcriptional level indicates that VE may exert part of its biological effects by mechanisms which may be independent of its well-recognised antioxidant function. The objective of this study was the identification of hepatic vitamin E-sensitive genes and examination of the effects of VE on their corresponding biological endpoints. Two groups of male rats were randomly assigned to either a VE-sufficient diet or to a control diet deficient in VE for 290 days. High-density oligonucleotide microarrays comprising over 7000 genes were used to assess the transcriptional response of the liver. Differential gene expression was monitored over a period of 9 months, at four different time-points, and rats were individually profiled. This experimental strategy identified several VE-sensitive genes, which were chronically altered by dietary VE. VE supplementation down-regulated scavenger receptor CD36, coagulation factor IX and 5-alpha-steroid reductase type 1 mRNA levels while hepatic gamma glutamyl-cysteinyl synthetase was significantly up-regulated. Measurement of the corresponding biological endpoints such as activated partial thromboplastin time, plasma dihydrotestosterone and hepatic glutathione substantiated the gene chip data which indicated that dietary VE plays an important role in a range of metabolic processes within the liver.

Polymorphisms in coagulation factor genes and their impact on arterial and venous thrombosis

Arterial and venous thromboses, with their clinical manifestations such as stroke, myocardial infarction (MI), or pulmonary embolism, are the major causes of death in developed countries. Several studies in twins and siblings have shown that genetic factors contribute significantly to the development of these diseases. Since the advent of molecular genetics in medicine, it has been a focus of interest to elucidate the role of mutations in various candidate genes and their impact on hemostatic disorders such as arterial and venous thromboses. In this article, we review the current knowledge of the contribution of polymorphisms in coagulation factors to the development of thrombotic diseases. We show that in arterial thrombosis, results are controversial. Only for factor XIII 34Leu a protective effect on the development of myocardial infarction has been demonstrated in several studies. No other single polymorphism in a coagulation factor could be confirmed as a relevant risk factor, although there is evidence for a role of factor V Arg506Gln, factor VII Arg353Gln, and vWF Thr789Ala polymorphisms in patient subgroups. Further studies will be necessary to confirm the value of testing for genetic polymorphisms in arterial thrombosis. A large body of data is available on the role of factor V Arg506Gln and the prothrombin G20210A mutation in venous thrombosis. Some papers already recommend diagnosis and treatment strategies. We will discuss these recent publications on venous thrombosis in our review.

Pathogenesis of venous thromboembolism

Three factors are related with the pathogenesis of venous thrombosis: (1) blood stasis, (2) hypercoagulability, and (3) vessel damage. Local and systemic factors are implicated in blood stasis. Remarkable advances have been recently achieved regarding the understanding of the concept of hypercoagulability, with special emphasis to thrombophilic molecular abnormalities. Increased thromboembolic risk has been described in patients with antithrombin III, protein C, or protein S deficiencies as well as factor V Leiden, prothrombin mutation G20210A, or hyperhomocystinemia. Vessel wall has a remarkable role in protecting against and in promoting thrombosis. The role of inflammation on venous thrombosis is under investigation.

The natural history of venous thromboembolism: impact on ventilation/perfusion scan reporting

Deep vein thrombosis (DVT) and pulmonary embolism (PE) are separate but related aspects of the same dynamic disease process known as venous thromboembolism (VTE). Recent community studies have shown that VTE is a major health issue for the developed world, with at least 201,000 new cases each year in the United States, comprising 107,000 with DVT and 94,000 with PE. A quarter of PE cases die within 7 days, some so rapidly that treatment or intervention is impossible. Despite the availability of heparin prophylaxis, the annual incidence of VTE has remained constant at 1 event per 1,000 person-years since 1979 but reaches 1 event per 100 person-years for the over-85-year-olds. The most important risk factors for VTE are hemostatic and environmental. The recent discoveries of factor V Leiden, prothrombin 20210A, and high concentrations of factor VIII have highlighted the increasing importance of a genetic predisposition to thrombophilia. Acquired hemostatic factors include pregnancy and the puerperium, oral contraception, hormone-replacement therapy, malignant tumors, and antiphospholipid syndromes. Important environmental risk factors include hospitalization with previous surgery or trauma, confinement in a care facility, neurologic disease or paraplegia after stroke, current or recent central venous catheter or transvenous pacemaker, and long airplane flights. Internists may be confused about the risk of PE after ventilation/perfusion (VQ) imaging. This may well arise from their use of the relative risk of PE after a low-probability category scan rather than the absolute risk obtained by incorporating the PE prevalence for their particular patient in the risk analysis. Ideally, personal communication with an experienced referring physician provides this clinical information for nuclear medicine. Diagnostic tools or checklists can be used as an alternative. A general knowledge of the natural history of VTE will encourage the nuclear medicine physician to provide an appropriate clinical signal to complement VQ categorical analysis. Combination of these 2 dynamic elements of the art and science of VQ scan reporting-the clinical pretest probability of PE and lung scan category-will permit an accurate prediction of the absolute risk of PE posttest.