Platelet hyperaggregability and venous thrombosis risk: results from the RETROVE project.

The aim of the study was to determine whether platelet hyperaggregability correlates with short closure times (PFA-100) and if hyperaggregability is associated with the risk of venous thrombosis in a Spanish population. Case--control study (RETROVE project) involving 400 patients with venous thrombosis and 400 healthy controls. We determined platelet aggregation in platelet-rich plasma (PRP) by light transmission aggregometry. Various concentrations of two aggregation agonists [ADP and epinephrine (EPI)] were tested to determine the percentage of maximal aggregation and the percentage area under the curve (AUC). Venous thrombosis risk associated with platelet hyperaggregability was calculated by logistic regression. We estimated the crude and adjusted (by sex and age) odds ratios (OR) for venous thrombosis risk. An agonist concentration of 0.5 µmol/l differentiated between hypo-responders and hyper-responders at the following AUC cut-off values: EPI: the 50th percentile for aggregation with 0.5 µmol/l of EPI (EPI_AUC) was 22.53% (>22.53% = hyper-EPI); the crude risk for venous thrombosis was statistically significant (OR = 1.37; 95% CI 1.03-1.82); ADP: the 75th percentile for aggregation with 0.5 µmol/l of ADP (ADP_AUC) was 29.6% (>29.6% = hyper-ADP), with a significant crude risk for venous thrombosis (OR = 1.44; 95% CI 1.05-1.98). However, after adjustment for confounders (age), the ORs for EPI or ADP aggregation were no longer significant. EPI_AUC and PFA-100 values with the EPI agonist were significantly correlated (R = -0.342, P < 0.01). Only 12% of the PFA-100 values were explained by platelet aggregation. In this case--control study, platelet hyperaggregability was not associated with the risk of developing venous thrombosis.

VAMP8 and serotonin transporter levels are associated with venous thrombosis risk in a Spanish female population. Results from the RETROVE Project.

INTRODUCTION: Platelet hyper-reactivity has been associated with thrombosis and high levels of human vesicle-associated membrane protein 8 (VAMP8) and serotonin transporter (SERT). Two polymorphisms (rs1010 of VAMP8 gene and in SERT gene (SLC6A4)) are associated with arterial thrombosis. AIM: To determine if levels of serotonin, SERT and/or VAMP8 and these polymorphisms are associated with the risk of venous thrombosis. MATERIAL AND METHODS: A total of 324 individuals were included in the RETROVE Study (Riesgo de Enfermedad TROmboembólica VEnosa). VAMP8, SERT and serotonin were determined by ELISA; polymorphisms of SLC6A4 and VAMP8 by polymerase chain reaction (PCR) and real time PCR. The venous thrombotic risk was calculated by a logistic regression method to estimate the crude and adjusted OR (adjusted for sex, age, body mass index and venous thrombosis risk co-factors). RESULTS: Statistically significant high levels of VAMP8 and SERT were found in patients, but not in controls. In contrast, serotonin showed lower levels in patients than in controls. When individuals were studied by gender, only women exhibited a statistically significant difference: the OR for VAMP8 was 3.25 (1.61-6.56 95% CI). The adjusted OR did not change. The OR for SERT was 2.76 (1.36-5.60 95% CI), the adjusted OR was maintained also. For serotonin with OR of 2.62 (1.40-4.92 95% CI), the adjusted OR was not significant. In contrast males did not show significant differences. No statistically differences between patients and controls were found for both polymorphisms. CONCLUSIONS: VAMP8 and SERT levels are associated with venous thrombosis in a female Spanish population.

Short closure time values in PFA-100® are related to venous thrombotic risk. Results from the RETROVE Study.

INTRODUCTION: Platelets play a role in the pathophysiology of venous thromboembolism (VTE). Some studies have not found an association between VTE and platelet aggregation. The PFA-100® analyser is an in vitro assay for assessing primary haemostasis. But, there are no studies to evaluate its association with VTE. We investigated the contribution of the global platelet function and aggregation in the development of VTE. MATERIAL AND METHODS: We analysed 800 individuals who were included in the RETROVE Study (Riesgo de Enfermedad TROmboembólica VEnosa). Global platelet function was evaluated as closure times (CT) with the agonists ADP and epinephrine using a PFA-100® analyser. Platelet aggregation was evaluated by Multiplate™ analyser. The VTE risk for all the parameters was calculated by unconditional logistic regression analyses considering the potential confounders: age, gender, body mass index (BMI), factor VIII (FVIII), the von Willebrand factor (vWF) and the ABO blood group system. RESULTS: The unadjusted odds ratio (OR) values ≤10th percentile for the PFAadp and PFAepi were 4.02 (95% CI, 2.76-5.95) and 3.33 (2.27-4.97). Also, after adjusting for vWF, we obtained lower OR for the PFAadp and for PFAepi: 2.24 (1.44-3.49) and 1.63 (1.04-2.59). But, the whole blood aggregation parameters did not shown an association with VTE risk. CONCLUSION: We demonstrated an association between short CT and VTE risk. Although, the whole blood aggregation parameters did not show an association with the VTE risk. This striking contrast suggests that there are other platelet function mechanisms (e.g. adhesion) that are responsible of VTE risk.

Genetic determinants of platelet large-cell ratio, immature platelet fraction, and other platelet-related phenotypes.

INTRODUCTION: Platelets play a significant role in arterial thrombosis and are involved also in venous thrombosis. The genetic determinants of several platelet-related phenotypes have been studied previously. However, to the best of our knowledge, the genetic determinants of other platelet phenotypes have not been reported such as platelet-large-cell ratio (P-LCR) index, immature platelet fraction (IPF) parameters and overall platelet function measured through the PFA-100 system. MATERIALS AND METHODS: As part of the GAIT-2 (Genetic Analysis of Idiopathic Thrombophilia 2) Project, 935 individuals from 35 large Spanish families, ascertained through a proband with thrombophilia, were studied. Using variance component methods, implemented in the SOLAR package, the heritability of the following sets of platelet-related phenotypes was determined: platelet count and indices, IPF, and platelet function. RESULTS AND CONCLUSIONS: High heritabilities of the platelet count and index phenotypes (from 0.41 to 0.64) were found, especially for those related to platelet volume. The heritabilities of the IPF phenotypes, as a measure of platelet turnover, were the highest (from 0.65 to 0.69). The heritabilities of the platelet function phenotypes were high also (0.45 and 0.62). The covariate age influenced all of the platelet phenotypes. Smoking influenced the platelet indices related to platelet volume and all the IPF phenotypes. Venous thrombosis showed a heritability of 0.67. We did not find a genetic correlation between any of the platelet-related phenotypes and venous thrombosis. The high heritabilities found for all of the platelet phenotypes provid promising data for the identification of new genes that underly these phenotypes.

Utilización de heparinas de bajo peso molecular para la profilaxis y el tratamiento de la enfermedad tromboembólica en pacientes embarazadas / Use of low molecular weight heparin for thromboprophylaxis and treatment of venous thromboembolism in pregnant women

Estudio observacional que valoró la seguridad de heparina de bajo peso molecular (HBPM) administrada para la profilaxis o el tratamiento de complicaciones tromboembólicas durante el embarazo. Diseño: Se revisaron retrospectivamente historias clínicas y se recogió el resultado del embarazo y los acontecimientos adversos. El riesgo tromboembólico (ETEV) se analizó mediante la clasificación del Royal College of Obstetrics and Gynaecologist. Resultados: Se incluyeron 127 pacientes (131 fetos) con edad media de 32,3 ± 4,3 años. La HBPM se indicó por ETEV aguda en 11 (8,6%) pacientes y por profilaxis en 116 (91,4%). En el grupo de profilaxis hubo 38 (30,0%), 49 (38,6%) y 29 (22,8%) pacientes con riesgo de ETEV alto, moderado y bajo respectivamente. Los nacidos vivos fueron 127 (97%) —19 (15,1%) pretérmino—. Una paciente con déficit de antitrombina desarrolló ETEV. Hubo 25 casos de sangrado (18 [72%] hematomas subcutáneos). Conclusión: La HBPM es bien tolerada y segura para la profilaxis y el tratamiento de las complicaciones tromboembólicas del embarazo (AU)

This observational study evaluated the safety of low molecular weight heparin (LMWH) for the prophylaxis and treatment of thromboembolic complications in pregnancy. Study Design: The medical records of pregnant women were identified and reviewed retrospectively. Information was extracted on LMWH use, pregnancy outcome, and adverse events. The Guidelines of the Royal College of Obstetrics and Gynaecologists were used to evaluate the thromboembolic risk. Results: Data were collected on 127 pregnancies (131 fetuses); the mean age was 32.3 ± 4.3. LMWH was prescribed for acute venous thromboembolism in 11 patients (8.6%) and for prophylaxis in 116 (91.4%). For the prophylaxis group, there were 38 (30.0%), 49 (38.6%) and 29 (22.8%) patients with high, moderate and low venous thromboembolism risk, respectively. There were 127 (97%) live births (19 preterm [15.1%]). In the prophylaxis group, one venous thromboembolism occurred in a patient with antithrombin deficiency. Safety outcomes included 25 cases of bleeding (18 [72%] were injection site hematomas). Conclusion: We found that LMWH was well tolerated and safe for the prophylaxis and treatment of thromboembolic complications during pregnancy (AU)

A genomewide study of body mass index and its genetic correlation with thromboembolic risk. Results from the GAIT project.

Thrombosis and obesity are complex epidemiologically associated diseases. The mechanism of this association is not yet understood. It was the objective of this study to identify genetic components of body mass index (BMI) and their possible role in the risk of thromboembolic disease. With the self-reported BMI of 397 individuals from 21 extended families enrolled in the GAIT (Genetic Analysis of Idiopathic Thrombophilia) Project, we estimated the heritability of BMI and the genetic correlation with the risk of thrombosis. Subjects were genotyped for an autosomal genome-wide scan with 363 highly-informative DNA markers. Univariate and bivariate multipoint linkage analyses were performed. The heritability for BMI was 0.31 (p=2.9×10⁻5). Thromboembolic disease (including venous and arterial) and BMI had a significant genetic correlation (ρG=0.54, p=0.005). Two linkage signals for BMI were obtained, one at 13q34 (LOD=3.36, p=0.0004) and other at 2q34, highly suggestive of linkage (LOD=1.95). Bivariate linkage analysis with BMI and thrombosis risk also showed a significant signal at 13q34 (LOD=3), indicating that this locus influences at the same time normal variation in the BMI phenotype as well as susceptibility to thrombosis. In conclusion, BMI and thrombosis are genetically correlated. The locus 13q34, which showed pleiotropy with both phenotypes, contains two candidate genes, which may explain our linkage pleiotropic signal and deserve further investigation as possible risk factors for obesity and thrombosis.

Pharmacodynamics assessment of Bemiparin after multiple prophylactic and single therapeutic doses in adult and elderly healthy volunteers and in subjects with varying degrees of renal impairment.

INTRODUCTION: Aging and renal impairment may prolong the half-life and lead to accumulation of low molecular weight heparins. Correct dosing is critical to prevent bleeding or thrombosis. MATERIALS AND METHODS: Open, parallel study. Healthy adult [n=13] and elderly (>65yrs) [n=12] volunteers; and subjects with mild (ClCr≥50 to ≤80mL/min, n=8), moderate (ClCr≥30 to <50mL/min, n=7), and severe (ClCr<30mL/min, n=8) renal impairment received four prophylactic doses (3,500IU/24h) and a single therapeutic dose (115IU/kg) of bemiparin with an interim washout period. Anti-FXa activity and the potential need for dose adjustment were evaluated. RESULTS: There were statistically significant differences in the severe renal impairment group vs. adult volunteers in all anti-FXa related parameters, but no significant differences in any of the anti-FXa related parameters between the adult and the elderly. Anti-FXa simulations after 10 prophylactic doses predicted mean Amax=0.59IU/mL in subjects with severe renal impairment and 0.33-0.39IU/mL in the rest. Simulations in the severe renal impairment group with dose adjustment (2,500IU/24h) predicted all individual Amax<0.60IU/mL (mean Amax=0.42IU/ml). Simulations after 10 therapeutic doses predicted mean Amax=1.22IU/mL in severe renal impairment group and 0.89-0.98IU/mL in the rest. Simulations in the severe renal impairment group with 75% dose adjustment predicted individual Amax≤1.60IU/mL (mean Amax=0.91IU/mL). CONCLUSIONS: No dose adjustments are required in elderly with preserved renal function. A dose adjustment of bemiparin is only advisable in patients with severe renal impairment when using prophylactic or therapeutic doses.

Bemiparin versus unfractionated heparin as bridging therapy in the perioperative management of patients on vitamin K antagonists: the BERTA study.

BACKGROUND AND OBJECTIVE: The management of patients on vitamin K antagonist therapy who require an invasive procedure is problematic. A randomised, controlled, double-blind clinical trial was designed to compare the efficacy and safety of bemiparin, a low molecular weight heparin (LMWH), with unfractionated heparin (UFH) as bridging therapy: the BERTA (BEmiparin Randomised Trial on bridging Anticoagulants) study. METHODS: Two hundred and six patients on long-term oral anticoagulation therapy (OAT) requiring an invasive procedure were randomized to receive bridging therapy with bemiparin + matching placebo or UFH. OAT was resumed on day 1. The study medication was continued for 5-6 days after the procedure. The primary efficacy endpoint was the combined incidence of arterial and venous thromboembolic events. The primary safety endpoint was the incidence of major bleeding within 10 days after the invasive procedure. RESULTS: There were no thromboembolic events in the bemiparin group, but two events (2.2 %) occurred in the UFH group. No major bleeding occurred in either group, but minor bleeding occurred in four patients (4.3 %) and six patients (6.1 %) in the bemiparin and UHF groups, respectively. No deaths and no cases of severe thrombocytopenia occurred during the whole study period. CONCLUSION: Despite its small size, the BERTA study is the first randomised, double-blind clinical trial comparing UFH with a fixed high-risk thromboprophylactic dose of an LMWH as bridging therapy. There were no thromboembolic events and fewer bleeding episodes in the bemiparin group than in the UFH group, hence we suggest that bemiparin is at least as safe as UFH as bridging therapy.

Sex-specific regulation of mitochondrial DNA levels: genome-wide linkage analysis to identify quantitative trait loci.

Altered mitochondrial DNA (mtDNA) levels have been associated with common diseases in humans. We investigated the genetic mechanism that controls mtDNA levels using genome-wide linkage analyses in families from the Genetic Analysis of Idiopathic Thrombophilia Project (GAIT). We measure mtDNA levels by quantitative real-time PCR in 386 subjects from 21 extended Spanish families. A variance component linkage method using 485 microsatellites was conducted to evaluate linkage and to detect quantitative trait loci (QTLs) involved in the control of mtDNA levels. The heritalibility of mtDNA levels was 0.33 (p=1.82e-05). We identified a QTL on Chromosome 2 (LOD=2.21) using all of the subjects, independently on their sex. When females and males were analysed separately, three QTLs were identified. Females showed the same QTL on Chromosome 2 (LOD=3.09), indicating that the QTL identified in the analysis using all of the subjects was a strong female QTL, and another one on Chromosome 3 (LOD=2.67), whereas in males a QTL was identified on Chromosome 1 (LOD=2.81). These QTLs were fine-mapped to find associations with mtDNA levels. The most significant SNP association was for the rs10888838 on Chromosome 1 in males. This SNP mapped to the gene MRPL37, involved in mitochondrial protein translation. The rs2140855 on Chromosome 2 showed association in the analysis using all of the subjects. It was near the gene CMPK2, which encodes a mitochondrial enzyme of the salvage pathway of deoxyribonucleotide synthesis. Our results provide evidence of a sex-specific genetic mechanism for the control of mtDNA levels and provide a framework to identify new genes that influence mtDNA levels.

Genetic determinants of 5-lipoxygenase pathway in a Spanish population and their relationship with cardiovascular risk.

OBJECTIVE: Leukotrienes (LT) play a role in inflammation, cardiovascular diseases, and cancer. Although some studies suggest that there are genes that determine variability of some LT-related phenotypes, the genetic influence on these phenotypes has not been evaluated. METHODS: The relative contributions of genetic and environmental influences to the 5-lipoxygenase pathway-related phenotypes (5-Lipoxygenase, five lipoxygenase activating protein (FLAP), LTA(4)-hydrolase and LTC(4)-synthase expression, and LTB(4)-plasma concentration and LTB(4) production by stimulated whole blood) were assessed in a sample of 934 individuals in 35 extended families. Our design is based on extended families recruited through a probands with idiopathic thrombophilia. This strategy allows us the analysis of the effects of measured covariates (such as sex, age and smoking), genes, and environmental variables shared by members of a household. RESULTS: All of these phenotypes showed significant genetic contributions, with heritabilities ranging from 0.33 to 0.51 for enzyme expression and from 0.25 to 0.50 for LTB(4) production of the residual phenotypic variance. Significant phenotypic and genetic correlation among the LT-related traits was found. More importantly, FLAP and LTA(4)-hydrolase expression exhibit significant genetic correlations with arterial thrombosis, indicating that some of the genes that influence quantitative variation in these phenotypes also influence the risk of thrombosis. CONCLUSION: This is the first study that quantifies the genetic component of 5-Lipoxygenase pathway phenotypes. The high heritability of these traits and the significant genetic correlations between arterial thrombosis and some of these phenotypes suggest that the exploitation of correlated quantitative phenotypes will aid the search for susceptibility genes.

Influence of age, gender and lifestyle in lymphocyte subsets: report from the Spanish Gait-2 Study.

INTRODUCTION: Flow cytometry analysis of lymphocyte subsets in peripheral blood is a common technique in diagnostic laboratories. Abnormal values have been identified in prevalent infections, autoimmune disorders and neoplastic diseases. Reference ranges for lymphocyte subsets of a healthy population from Spain are scarce. METHODS: The study was performed on 319 healthy subjects, aged 4-88 years, from 709 individuals enrolled in the GAIT-2 Project (Genetic Analysis of Idiopathic Thrombophilia). Health status, age, sex, fertility, BMI and lifestyle (physical activity, cigarette smoking and ethanol intake) were assessed using standardized criteria. The percentage of lymphocyte subsets was determined using flow cytometry (Lymphogram™). Percentages of CD3+, CD4+, CD8+, CD19+, CD3-CD56+, CD3+CD4-CD8- double-negative (DN) T cells, CD3+CD4+CD8+ double-positive T cells and the CD4+/CD8+ ratio were recorded for each case. RESULTS: Children had a significantly higher percentage of CD19+ and DN cells than adults. Women had a significantly higher percentage of CD3+ and CD4+ and a lower percentage of natural killer cells than men. Increases in BMI were inversely associated with the percentage of DN cells. Physical activity increased the percentage of lymphocytes and DN cells. Alcohol consumers had a lower percentage of CD19+ and DN cells, and a higher percentage of CD4+. CONCLUSION: This study provides reference ranges for lymphocyte subsets of healthy children and adults in a Mediterranean population (Spain) and determines the influence of lifestyle factors on these values.

Regulatory regions of SERPINC1 gene: identification of the first mutation associated with antithrombin deficiency.

Antithrombin is the main endogenous anticoagulant. Impaired function or deficiency of this molecule significantly increases the risk of thrombosis. We studied the genetic variability of SERPINC1 , the gene encoding antithrombin, to identify mutations affecting regulatory regions with functional effect on its levels. We sequenced 15,375 bp of this gene, including the potential promoter region, in three groups of subjects: five healthy subjects with antithrombin levels in the lowest (75%) and highest (115%) ranges of our population, 14 patients with venous thrombosis and a moderate antithrombin deficiency as the single thrombophilic defect, and two families with type I antithrombin deficiency who had neither mutations affecting exons or flanking regions, nor gross gene deletions. Our study confirmed the low genetic variability of SERPINC1 , particularly in the coding region, and its minor influence in the heterogeneity of antithrombin levels. Interestingly, in one family, we identified a g.2143 C>G transversion, located 170 bp upstream from the translation initiation codon. This mutation affected one of the four regions located in the minimal promoter that have potential regulatory activity according to previous DNase footprinting protection assays. Genotype-phenotype analysis in the affected family and reporter analysis in different hepatic cell lines demonstrated that this mutation significantly impaired, although it did not abolish, the downstream transcription. Therefore, this is the first mutation affecting a regulatory region of the SERPINC1 gene associated with antithrombin deficiency. Our results strongly sustain the inclusion of the promoter region of SERPINC1 in the molecular analysis of patients with antithrombin deficiency.

Haplotypes of the endothelial protein C receptor gene and Behçet's disease.

INTRODUCTION: Behçet's disease is a vasculitis of unknown cause in which thrombosis occurs in about 25% of patients. Two haplotypes of the endothelial protein C receptor gene, H1 and H3, are associated with the risk of thrombosis. Thus, the objective of this study was to evaluate the influence of these haplotypes on the thrombosis risk in Behçet's disease. MATERIAL AND METHODS: We evaluated the H1 and H3 haplotypes in 87 patients with Behçet's disease, 19 with and 68 without a history of thrombosis, and in 260 healthy individuals. We also measured protein C, activated protein C, and soluble endothelial protein C receptor levels in all individuals. RESULTS: The presence of the H1 haplotype seemed to protect Behçet's patients against thrombosis (odds ratio 0.21; 95% CI 0.1-0.8; p=0.023), whereas the frequency of the H3 haplotype was lower in patients than in control individuals (0.19; 0.1-0.5; p=0.006). Furthermore, the H1 haplotype was associated with increased levels of activated protein C, whereas the H3 haplotype was associated with the highest soluble endothelial protein C levels. Moreover, activated protein C levels were lower in patients with than in patients without posterior uveitis (p<0.001). CONCLUSIONS: These findings indicate that the H1 haplotype protects Behçet's patients from thrombosis, likely via increased levels of activated protein C, whereas individuals carrying the H3 haplotype seem to be protected from the clinical manifestations associated with Behçet's disease, probably via increased soluble endothelial protein C levels.

Safety assessment and pharmacodynamics of a novel ultra low molecular weight heparin (RO-14) in healthy volunteers--a first-time-in-human single ascending dose study.

INTRODUCTION: RO-14 is a novel ultra low molecular heparin. The purpose of this study was to evaluate the safety and pharmacodynamic profile of RO-14 in healthy males. MATERIALS AND METHODS: We conducted a two-stage, single-center, open-label, randomized study. Two cohorts of 6 volunteers were randomly assigned to 12 single, ascending subcutaneous doses (1750-19950IU of anti-FXa activity) in an alternating crossover fashion. Safety was assessed by spontaneous/elicited adverse events, medical examination and laboratory tests. Anti-FXa activity and anti-FIIa activity were assessed throughout the 24hours after dosing. Dose proportionality and linearity of the anti-FXa activity were evaluated. RESULTS: All doses were well tolerated and there were no bleeding events. At the lowest dose, anti-FXa activity A(max) was 0.16 (±0.02) IU/mL and AUC(0-24) was 1.11 (±0.24) IU*h/mL, At the highest dose anti-FXa activity A(max) was 1.67 (±0.15) IU/mL; AUC(0-24) was 21.48 (±4.46) IU*h/mL and t½ was 8.05h. Mean T(max) (all doses) was 2.86 (±0.39) h. RO-14 showed proportional and linear pharmacodynamics [normalized A(max) among doses (p=0.594) and normalized AUC(0-24) (p=0.092), correlations between A(max-)dose (R(2)=0.89, p<0.001) and AUC(0-24)-dose (R(2)=0.86, p<0.001)]. Anti-FIIa activity was below the detection limit (0.1IU/ml) at all dose levels. No clinically significant changes were observed in the platelet count, APTT, PT, TT, fibrinogen and antithrombin. CONCLUSIONS: In this phase I study, RO-14 exhibited a good safety profile, anti-FXa activity for either prophylaxis or treatment of venous thromboembolism, linear pharmacodynamics, a longer elimination half-life than currently marketed low molecular weight heparin and no anti-FIIa activity.

A genome-wide association study of the Protein C anticoagulant pathway.

The Protein C anticoagulant pathway regulates blood coagulation by preventing the inadequate formation of thrombi. It has two main plasma components: protein C and protein S. Individuals with protein C or protein S deficiency present a dramatically increased incidence of thromboembolic disorders. Here, we present the results of a genome-wide association study (GWAS) for protein C and protein S plasma levels in a set of extended pedigrees from the Genetic Analysis of Idiopathic Thrombophilia (GAIT) Project. A total number of 397 individuals from 21 families were typed for 307,984 SNPs using the Infinium® 317 k Beadchip (Illumina). Protein C and protein S (free, functional and total) plasma levels were determined with biochemical assays for all participants. Association with phenotypes was investigated through variance component analysis. After correcting for multiple testing, two SNPs for protein C plasma levels (rs867186 and rs8119351) and another two for free protein S plasma levels (rs1413885 and rs1570868) remained significant on a genome-wide level, located in and around the PROCR and the DNAJC6 genomic regions respectively. No SNPs were significantly associated with functional or total protein S plasma levels, although rs1413885 from DNAJC6 showed suggestive association with the functional protein S phenotype, possibly indicating that this locus plays an important role in protein S metabolism. Our results provide evidence that PROCR and DNAJC6 might play a role in protein C and free protein S plasma levels in the population studied, warranting further investigation on the role of these loci in the etiology of venous thromboembolism and other thrombotic diseases.

Hemostatic proteins and their association with hematoma growth in patients with acute intracerebral hemorrhage.

BACKGROUND AND PURPOSE: We tested the hypothesis that proteins of hemostasia could be associated with hematoma growth (HG) in patients with acute intracerebral hemorrhage. METHODS: We prospectively studied patients with spontaneous supratentorial intracerebral hemorrhage within the first 6 hours after the onset of symptoms. HG was defined as an increase > 33% in the volume of hematoma on CT obtained 24 to 72 hours after the onset of symptoms in comparison with the CT obtained at admission. We collected admission and follow-up blood samples. We measured fibrinogen, factor XIII, thrombin activatable fibrinolysis inhibitor, plasminogen activator inhibitor, plasminogen, α2-antiplasmin, tissue plasminogen activator, d-dimer, thrombomodulin, thrombin-antithrombin complex, and plasmin-antiplasmin complex. RESULTS: We included 90 patients with a mean age of 71 ± 10.8 years; 61% were men. HG was observed in 35 (39%) of the patients. Mean baseline and follow-up protein measurements showed no difference between the groups with and without HG. The analysis of variance showed that factor XIII activity decreased in the non-HG group in the 24 to 72 hours sample, whereas it increased in the HG group (P = 0.001). CONCLUSIONS: Factor XIII was the only measured protein related to HG. The levels at the follow-up sample decreased in the non-HG group and increased in the HG group. Further studies are needed to confirm this association.

C4BPB/C4BPA is a new susceptibility locus for venous thrombosis with unknown protein S-independent mechanism: results from genome-wide association and gene expression analyses followed by case-control studies.

Through its binding with protein S (PS), a key element of the coagulation/fibrinolysis cascade, the C4b-binding protein (C4BP) has been hypothesized to be involved in the susceptibility to venous thrombosis (VT). To identify genetic factors that may influence the plasma levels of the 3 C4BP existing isoforms, alpha(7)beta(1), alpha(6)beta(1), and alpha(7)beta(0), we conducted a genome-wide association study by analyzing 283 437 single nucleotide polymorphisms (SNPs) in the Genetic Analysis of Idiopathic Thrombophilia (GAIT) study composed of 352 persons. Three SNPs at the C4BPB/C4BPA locus were found genome-wide significantly associated with alpha(7)beta(0) levels. One of these SNPs was further found to explain approximately 11% of the variability of mRNA C4BPA expression in the Gutenberg Heart Study composed of 1490 persons, with no effect on C4BPB mRNA expression. The allele associated with increased alpha(7)beta(0) plasma levels and increased C4BPA expression was further found associated with increased risk of VT (odds ratio [OR] = 1.24 [1.03-1.53]) in 2 independent case-control studies (MARseille THrombosis Association study [MARTHA] and FActeurs de RIsque et de récidives de la maladie thromboembolique VEineuse [FARIVE]) gathering 1706 cases and 1379 controls. This SNP was not associated with free PS or total PS. In conclusion, we observed strong evidence that the C4BPB/C4BPA locus is a new susceptibility locus for VT through a PS-independent mechanism that remains to be elucidated.