Factor VII coagulant activity, factor VII -670A/C and -402G/A polymorphisms, and risk of venous thromboembolism

Contribution of factor VII polymorphisms to coagulopathy in patients with isolated traumatic brain injury

BACKGROUND

Coagulopathy is a severe complication of traumatic brain injury (TBI) and can cause secondary injuries and death. Decrease of FVII activity contributes to the coagulopathy and progressive hemorrhagic injury (PHI) in patients with isolated TBI. Some polymorphic loci of coagulation factor VII (FVII) are shown to be essential for FVII activity. However, the relationship between FVII gene polymorphisms and coagulopathy in patients with isolated TBI is still unknown. Therefore, the present study aimed to investigate the relationship between FVII gene polymorphisms and plasma FVIIa levels, and assess whether FVII polymorphisms were associated with TBI-related coagulopathy, PHI, and 6 months GOS in patients with isolated TBI.

METHODS

One-hundred-forty-nine patients with isolated TBI (from East of China) admitted to Huashan Hospital's Neurological Trauma Center from March 2012 to March 2016 were enrolled in this study. The Polymorphism-Polymerase Chain Reaction (PCR) method was used to analyze the five FVII polymorphism loci (-323P0/P10, R353Q, -401G/T, -402G/A, and -670A/C) of these patients. Patients' blood was collected to test the activated partial thromboplastin time, international normalized ratio, platelet, and FVIIa concentrations. Other clinical characteristics were also recorded.

RESULTS

The minor alleles of three genotypes of -323 P0/P10, R353Q, and -401G/T each independently associated with 23.3%, 28.6%, and 27.6% lower FVIIa levels, respectively. These polymorphisms explained 21% of the total variance of FVIIa levels (adjusted R²:0.206). The genotype of -323P0/P10 was an independent risk factor for coagulopathy (OR = 2.77, p = 0.043) and PHI (OR = 3.47, p = 0.03) after adjustment for confounding factors in the logistic regression model. Polymorphisms of FVII were not independently associated with 6 months Glasgow Outcome Scale (GOS) of isolated TBI patients.

CONCLUSION

-323P0/P10, R353Q, and -401 G/T genotypes were associated with FVIIa levels. -323P0/P10 genotype was independently associated with traumatic coagulopathy and PHI in isolated TBI patients.

Biochemical, molecular and clinical aspects of coagulation factor VII and its role in hemostasis and thrombosis

Activated factor VII (FVIIa), the first protease of clotting, expresses its physiological procoagulant potential only after complexing with tissue factor (TF) exposed to blood. Deep knowledge of the FVIIa-TF complex and F7 gene helps to understand the Janus-faced clinical findings associated to low or elevated FVII activity (FVIIc). Congenital FVII deficiency, the most frequent among the recessively inherited bleeding disorders, is caused by heterogeneous mutations in the F7 gene. Complete FVII deficiency causes perinatal lethality. A wide range of bleeding symptoms, from life-threatening intracranial hemorrhage to mild mucosal bleeding, is observed in patients with apparently modest differences in FVIIc levels. Though clinically relevant FVIIc threshold levels are still uncertain, effective management, including prophylaxis, has been devised, substantially improving the quality of life of patients. The exposure of TF in diseased arteries fostered investigation on the role of FVII in cardiovascular disease. FVIIc levels were found to be predictors of cardiovascular death and to be markedly associated to F7 gene variation. These genotype-phenotype relationships are among the most extensively investigated in humans. Genome-wide analyses extended association to numerous loci that, together with F7, explain >50% of FVII level plasma variance. However, the ability of F7 variation to predict thrombosis was not consistently evidenced in the numerous population studies. Main aims of this review are to highlight i) the biological and clinical information that distinguishes FVII deficiency from the other clotting disorders and ii) the impact exerted by genetically predicted FVII level variation on bleeding as well as on the thrombotic states.

Blood coagulation system in patients with chronic kidney disease: a prospective observational study

OBJECTIVES

Thromboembolic events are the major factor affecting the prognosis of patients with chronic kidney disease (CKD). Haemostatic alterations are possible causes of these complications, but their roles remain poorly characterised. In the prospective observational study, we investigated the entire coagulation process in patients with CKD to elucidate the mechanisms of their high thromboembolic risk.

METHODS

A total of 95 patients with CKD and 20 healthy controls who met the inclusion criteria were consecutively recruited from September 2015 to March 2016. The platelet count, platelet aggregation, von Willebrand factor antigen (vWF:Ag), vWF ristocetin cofactor activity (vWF:RCo), fibrinogen, factor V (FV), FVII, FVIII, antithrombin III, protein C, protein S, D-dimer, standard coagulation tests and thromboelastography were measured in patients with CKD and controls. Associations between the estimated glomerular filtration rate (eGFR) and haemostatic biomarkers were tested using multivariable linear regression.

RESULTS

The adjusted and unadjusted levels of vWF:Ag, vWF:RCo, fibrinogen, FVII, FVIII and D-dimer were significantly higher in patients with CKD than that in the healthy controls, and were elevated with CKD progression. However, after adjustment for baseline differences, platelet aggregation and thromboelastography parameters showed no significant differences between patients with CKD and healthy controls. In the correlation analysis, vWF:Ag, vWF:RCo and FVIII were inversely associated with eGFR (r=-0.359, p<0.001; r=-0.391, p<0.001; r=-0.327, p<0.001, respectively). During the 1-year of follow-up, one cardiovascular event occurred in patients with CKD 5 stage, whereas no thromboembolic event occurred in the CKD 3 and 4 and control groups.

CONCLUSIONS

Patients with CKD are characterised by endothelial dysfunction and increased coagulation, especially FVIII activity. The abnormal haemostatic profiles may contribute to the elevated risk of thrombotic events but further longer-term study with large samples is still required to more precisely determine the relationship between the elevation of procoagulant factors and clinical outcomes.

Rare and low-frequency variants and their association with plasma levels of fibrinogen, FVII, FVIII, and vWF

Fibrinogen, coagulation factor VII (FVII), and factor VIII (FVIII) and its carrier von Willebrand factor (vWF) play key roles in hemostasis. Previously identified common variants explain only a small fraction of the trait heritabilities, and additional variations may be explained by associations with rarer variants with larger effects. The aim of this study was to identify low-frequency (minor allele frequency [MAF] ≥0.01 and <0.05) and rare (MAF <0.01) variants that influence plasma concentrations of these 4 hemostatic factors by meta-analyzing exome chip data from up to 76,000 participants of 4 ancestries. We identified 12 novel associations of low-frequency (n = 2) and rare (n = 10) variants across the fibrinogen, FVII, FVIII, and vWF traits that were independent of previously identified associations. Novel loci were found within previously reported genes and had effect sizes much larger than and independent of previously identified common variants. In addition, associations at KCNT1, HID1, and KATNB1 identified new candidate genes related to hemostasis for follow-up replication and functional genomic analysis. Newly identified low-frequency and rare-variant associations accounted for modest amounts of trait variance and therefore are unlikely to increase predicted trait heritability but provide new information for understanding individual variation in hemostasis pathways.

Role of hemostatic factors on the risk of venous thrombosis in people with impaired kidney function

BACKGROUND

Factors explaining the association between impaired kidney function and venous thrombosis have not been identified so far. The aim of our study was to determine whether the association between impaired kidney function and venous thrombosis can be explained by the concurrent presence of genetic or acquired venous thrombosis risk factors.

METHODS AND RESULTS

The glomerular filtration rate was estimated (eGFR) in 2473 venous thrombosis patients and 2936 controls from a population-based case-control study. Kidney function was grouped into 6 categories based on percentiles of the eGFR in the controls (>50th [reference], 10th-50th, 5th-10th, 2.5th-5th, 1st-2.5th, and <1st percentile). Several hemostatic factors showed a procoagulant shift with decreasing kidney function in controls, most notably factor VIII and von Willebrand factor. Compared with eGFR >50th percentile, factor VIII levels (adjusted mean difference, 60 IU/dL for the <1st eGFR percentile category) and von Willebrand factor levels (adjusted mean difference, 60 IU/dL for the <1st eGFR percentile category) increased with each percentile category. The odds ratios for venous thrombosis similarly increased across the categories from 1.1 (95% confidence interval, 0.9-1.3) for the 10th to 50th percentile to 3.7 (95% confidence interval, 2.4-5.7) for the <1st percentile category. Adjustment for factor VIII or von Willebrand factor attenuated these odds ratios, indicating an effect of eGFR on thrombosis through these factors. Adjustments for other risk factors for venous thrombosis did not affect the odds ratios.

CONCLUSION

Impaired kidney function affects venous thrombosis risk via concurrently raised factor VIII and von Willebrand factor levels.

Genetic associations with expression for genes implicated in GWAS studies for atherosclerotic cardiovascular disease and blood phenotypes

Genome-wide association studies (GWAS) have uncovered many genetic associations for cardiovascular disease (CVD). However, data are limited regarding causal genetic variants within implicated loci. We sought to identify regulatory variants (cis- and trans-eQTLs) affecting expression levels of 93 genes selected by their proximity to SNPs with significant associations in prior GWAS for CVD traits. Expression levels were measured by qRT-PCR in leukocytes from 1846 Framingham Heart Study participants. An additive genetic model was applied to 2.5 million imputed SNPs for each gene. Approximately 45% of genes (N = 38) harbored at least one cis-eSNP after a regional multiple-test adjustment. Applying a more rigorous significance threshold (P < 5 × 10(-8)), we found the expression level of 10 genes was significantly associated with more than one cis-eSNP. The top cis-eSNPs for 7 of these 10 genes exhibited moderate-to-strong association with ≥ 1 CVD clinical phenotypes. Several eSNPs or proxy SNPs (r(2) = 1) were replicated by other eQTL studies. After adjusting for the lead GWAS SNPs for the 10 genes, expression variances explained by top cis-eSNPs were attenuated markedly for LPL, FADS2 and C6orf184, suggesting a shared genetic basis for the GWAS and expression trait. A significant association between cis-eSNPs, gene expression and lipid levels was discovered for LPL and C6orf184. In conclusion, strong cis-acting variants are localized within nearly half of the GWAS loci studied, with particularly strong evidence for a regulatory role of the top GWAS SNP for expression of LPL, FADS2 and C6orf184.

Genetic variation associated with plasma von Willebrand factor levels and the risk of incident venous thrombosis

In a recent genome-wide association study, variants in 8 genes were associated with VWF level, a risk factor for venous thrombosis (VT). In an independent, population-based, case-control study of incident VT, we tested hypotheses that variants in these genes would be associated with risk. Cases were 656 women who experienced an incident VT, and controls comprised 710 women without a history of VT. DNA was obtained from whole blood. Logistic regression was used to test associations between incident VT and single nucleotide polymorphisms (SNPs) in 7 genes not previously shown to be associated with VT. Associations with P < .05 were candidates for replication in an independent case-control study of VT in both sexes. Two of the 7 SNPs tested yielded P < .05: rs1039084 (P = .005) in STXBP5, a novel candidate gene for VT, and rs1063856 (P = .04) in VWF, a gene whose protein level is associated with VT risk. Association results for the remaining 5 variants in SCARA5, STAB2, STX2, TC2N, and CLEC4M were not significant. Both STXBP5 and VWF findings were replicated successfully. Variation in genes associated with VWF levels in the genome-wide association study was found to be independently associated with incident VT.

Novel associations of multiple genetic loci with plasma levels of factor VII, factor VIII, and von Willebrand factor: The CHARGE (Cohorts for Heart and Aging Research in Genome Epidemiology) Consortium

BACKGROUND

Plasma levels of coagulation factors VII (FVII), VIII (FVIII), and von Willebrand factor (vWF) influence risk of hemorrhage and thrombosis. We conducted genome-wide association studies to identify new loci associated with plasma levels.

METHODS AND RESULTS

The setting of the study included 5 community-based studies for discovery comprising 23 608 European-ancestry participants: Atherosclerosis Risk In Communities Study, Cardiovascular Health Study, British 1958 Birth Cohort, Framingham Heart Study, and Rotterdam Study. All subjects had genome-wide single-nucleotide polymorphism (SNP) scans and at least 1 phenotype measured: FVII activity/antigen, FVIII activity, and vWF antigen. Each study used its genotype data to impute to HapMap SNPs and independently conducted association analyses of hemostasis measures using an additive genetic model. Study findings were combined by meta-analysis. Replication was conducted in 7604 participants not in the discovery cohort. For FVII, 305 SNPs exceeded the genome-wide significance threshold of 5.0x10(-8) and comprised 5 loci on 5 chromosomes: 2p23 (smallest P value 6.2x10(-24)), 4q25 (3.6x10(-12)), 11q12 (2.0x10(-10)), 13q34 (9.0x10(-259)), and 20q11.2 (5.7x10(-37)). Loci were within or near genes, including 4 new candidate genes and F7 (13q34). For vWF, 400 SNPs exceeded the threshold and marked 8 loci on 6 chromosomes: 6q24 (1.2x10(-22)), 8p21 (1.3x10(-16)), 9q34 (<5.0x10(-324)), 12p13 (1.7x10(-32)), 12q23 (7.3x10(-10)), 12q24.3 (3.8x10(-11)), 14q32 (2.3x10(-10)), and 19p13.2 (1.3x10(-9)). All loci were within genes, including 6 new candidate genes, as well as ABO (9q34) and VWF (12p13). For FVIII, 5 loci were identified and overlapped vWF findings. Nine of the 10 new findings were replicated.

CONCLUSIONS

New genetic associations were discovered outside previously known biological pathways and may point to novel prevention and treatment targets of hemostasis disorders.

An evaluation of candidate genes of inflammation and thrombosis in relation to the risk of venous thromboembolism: The Women's Genome Health Study

BACKGROUND

Although pathways associated with hemostasis and thrombosis are well documented to have an impact on venous thromboembolism (VTE), whether the inflammatory cascade also influences VTE risk is uncertain.

METHODS AND RESULTS

We evaluated 51 polymorphisms from 32 inflammation-related genes (and an additional 19 polymorphisms from 15 thrombosis-related genes) as potential determinants of VTE in a prospective cohort of 22 413 white women followed over a 10-year period. Hazard ratios (HRs) for incident VTE according to the different genotypes were assessed by Cox proportional-hazards models. The false discovery rate (FDR) was used for correction for multiple testing with a 0.20 cut point. During follow-up, 158 idiopathic and 180 secondary VTE events occurred. As anticipated, factor V Leiden (HR, 3.22; 95% CI, 1.92 to 5.40; P<0.0001; FDR=0.004) and the prothrombin mutation (HR, 2.57; 95% CI, 1.64 to 4.02; P<0.0001; FDR=0.004) were both strongly associated with incident idiopathic VTE, as was the rs6046 polymorphism in the factor VII gene (HR, 0.54; 95% CI, 0.35 to 0.86; P=0.008; FDR, 0.12). With regard to polymorphism in the inflammatory genes, variation at rs1143634 in the IL-1beta gene was associated with a reduced risk of idiopathic VTE (HR, 0.59; 95% CI, 0.44 to 0.80; P=0.0007; FDR=0.02), whereas variation at rs1800872 in the IL-10 gene was associated with increased risk (HR, 1.42; 95% CI, 1.12 to 1.80; P=0.004; FDR=0.07). By contrast, no significant associations were found for secondary VTE events.

CONCLUSIONS

In addition to previously reported polymorphisms associated with hemostasis and thrombosis, these prospective cohort data suggest that genetic variation in IL-1 beta and IL-10 genes may also influence the risk of idiopathic VTE.