Differential regulation of fibrinogen γ chain splice isoforms by interleukin-6

Impact of Tigecycline on Coagulation in Severe Infections and Effect of Vitamin K1 Intervention: A Retrospective Single-Center Analysis

BACKGROUND Tigecycline is a tetracycline antibiotic used to treat gram-positive and gram-negative bacterial infections, and bleeding is a dose-dependent adverse effect. Vitamin K1 is a fat-soluble vitamin used to treat hemorrhagic conditions. This retrospective study from a single center included 920 patients treated with tigecycline for bacterial infections between January 2017 and December 2022 and aimed to evaluate the incidence of coagulopathy and the use of vitamin K1. MATERIAL AND METHODS A total of 220 patients were included and divided into a high-dose group (100 mg, every 12 h) and normal-dose group (50 mg, every 12 h) according to the treatment dose of tigecycline. Clinical characteristics and changes in coagulation indicators during tigecycline treatment were collected. Seventy-two patients were treated with vitamin K1, and the changes in coagulation indicators before and after treatment were compared. ANOVA and t test were used to analyze the effects of different doses of tigecycline on coagulation function and the intervention of vitamin K1. RESULTS Among 920 patients, the incidence of coagulopathy was 23.91%. In both groups, coagulopathy occurred on days 5 to 7 after administration, and the high-dose group had worse coagulation function than the normal-dose group, including activated partial thrombin time, prothrombin time, and fibrinogen (P<0.05). After treatment with vitamin K1, fibrinogen increased and activated partial thrombin time and prothrombin time were shortened in both groups (P<0.05 or P<0.01). CONCLUSIONS Tigecycline caused coagulopathy with dose and time dependence. Vitamin K1 can improve tigecycline-induced coagulopathy.

Extreme γ' fibrinogen levels in COVID-19 patients

COVID-19 disease progression can be accompanied by a "cytokine storm" that leads to secondary sequelae such as acute respiratory distress syndrome. Several inflammatory cytokines have been associated with COVID-19 disease progression, but have high daily intra-individual variability. In contrast, we have shown that the inflammatory biomarker γ' fibrinogen (GPF) has a 6-fold lower coefficient of variability compared to other inflammatory markers such as hs-CRP. The aims of the study were to measure GPF in serial blood samples from COVID-19 patients at a tertiary care medical center in order to investigate its association with clinical measures of disease progression. COVID-19 patients were retrospectively enrolled between 3/16/2020 and 8/1/2020. GPF was measured using a commercial ELISA. We found that COVID-19 patients can develop extraordinarily high levels of GPF. Our results showed that ten out of the eighteen patients with COVID-19 had the highest levels of GPF ever recorded. The previous highest GPF level of 80.3 mg/dL was found in a study of 10,601 participants in the ARIC study. GPF levels were significantly associated with the need for ECMO and mortality. These findings have potential implications regarding prophylactic anticoagulation of COVID-19 patients.

Fibrinogen and fibrin: synthesis, structure, and function in health and disease

Fibrinogen is an extraordinary molecule by any estimation. It is large, structurally intricate, and circulates at high concentrations. Its biological end product, insoluble fibrin(ogen) or fibrin, can assume a diverse array of conformations with the ability to interact with numerous plasma proteins and cells and withstand biochemical and biomechanical disruption to facilitate wound healing. Quantitative and qualitative defects in fibrinogen or fibrin are associated with bleeding, thrombosis, inflammation, and diseases affected by these processes. Numerous studies investigating mechanisms by which fibrin(ogen) and fibrin contribute to health and disease have been published. This review for the 20th-anniversary series in the Journal of Thrombosis and Haemostasis summarizes interesting aspects of fibrin(ogen) biology, biochemistry, biophysics, and physiology and highlights exciting findings published in the past 2 decades.

Post-transcriptional control of haemostatic genes: mechanisms and emerging therapeutic concepts in thrombo-inflammatory disorders

The haemostatic system is pivotal to maintaining vascular integrity. Multiple components involved in blood coagulation have central functions in inflammation and immunity. A derailed haemostasis is common in prevalent pathologies such as sepsis, cardiovascular disorders, and lately, COVID-19. Physiological mechanisms limit the deleterious consequences of a hyperactivated haemostatic system through adaptive changes in gene expression. While this is mainly regulated at the level of transcription, co- and posttranscriptional mechanisms are increasingly perceived as central hubs governing multiple facets of the haemostatic system. This layer of regulation modulates the biogenesis of haemostatic components, for example in situations of increased turnover and demand. However, they can also be 'hijacked' in disease processes, thereby perpetuating and even causally entertaining associated pathologies. This review summarizes examples and emerging concepts that illustrate the importance of posttranscriptional mechanisms in haemostatic control and crosstalk with the immune system. It also discusses how such regulatory principles can be used to usher in new therapeutic concepts to combat global medical threats such as sepsis or cardiovascular disorders.

γ' fibrinogen levels as a biomarker of COVID-19 respiratory disease severity

Coronavirus disease 2019 (COVID-19) is characterized by a pro-inflammatory state associated with organ failure, thrombosis, and death. We investigated a novel inflammatory biomarker, γ' fibrinogen (GPF), in 103 hospitalized patients with COVID-19 and 19 healthy controls. We found significant associations between GPF levels and the severity of COVID-19 as judged by blood oxygen saturation (SpO2). The mean level of GPF in the patients with COVID-19 was significantly higher than in controls (69.8 (95 % CI 64.8-74.8) mg/dL compared with 36.9 (95 % CI 31.4-42.4) mg/dL, p < 0.0001), whereas C-reactive protein (CRP), lactate dehydrogenase (LDH), and total fibrinogen levels were not significantly different between groups. Mean GPF levels were significantly highest in patients with severe COVID-19 (SpO2 ≤ 93 %, GPF 75.2 (95 % CI 68.7-81.8) mg/dL), compared to mild/moderate COVID-19 (SpO2 > 93 %, GPF 62.5 (95 % CI 55.0-70.0) mg/dL, p = 0.01, AUC of 0.68, 95 % CI 0.57-0.78; Youden's index cutpoint 62.9 mg/dL, sensitivity 0.64, specificity 0.63). In contrast, CRP, interleukin-6, ferritin, LDH, D-dimers, and total fibrinogen had weaker associations with COVID-19 disease severity (all ROC curves with lower AUCs). Thus, GPF may be a useful inflammatory marker of COVID-19 respiratory disease severity.

Current View on the Molecular Mechanisms Underlying Fibrin(ogen)-Dependent Inflammation

Numerous studies have revealed the involvement of fibrinogen in the inflammatory response. To explain the molecular mechanisms underlying fibrinogen-dependent inflammation, two bridging mechanisms have been proposed in which fibrin(ogen) bridges leukocytes to endothelial cells. The first mechanism suggests that bridging occurs via the interaction of fibrinogen with the leukocyte receptor Mac-1 and the endothelial receptor ICAM-1 (intercellular adhesion molecule-1), which promotes leukocyte transmigration and enhances inflammation. The second mechanism includes bridging of leukocytes to the endothelium by fibrin degradation product E1 fragment through its interaction with leukocyte receptor CD11c and endothelial VE-cadherin to promote leukocyte transmigration. The role of E1 in promoting inflammation is inhibited by the fibrin-derived β15-42 fragment, and this has been suggested to result from its ability to compete for the E1-VE-cadherin interaction and to trigger signaling pathways through the src kinase Fyn. Our recent study revealed that the β15-42 fragment is ineffective in inhibiting the E1- or fibrin-VE-cadherin interaction, leaving the proposed signaling mechanism as the only viable explanation for the inhibitory function of β15-42. We have discovered that fibrin interacts with the very-low-density lipoprotein (VLDL) receptor, and this interaction triggers a signaling pathway that promotes leukocyte transmigration through inhibition of the src kinase Fyn. This pathway is inhibited by another pathway induced by the interaction of β15-42 with a putative endothelial receptor. In this review, we briefly describe the previously proposed molecular mechanisms underlying fibrin-dependent inflammation and their advantages/disadvantages and summarize our recent studies of the novel VLDL receptor-dependent pathway of leukocyte transmigration which plays an important role in fibrin-dependent inflammation.

The systemic-level repercussions of cancer-associated inflammation mediators produced in the tumor microenvironment

The tumor microenvironment is a dynamic, complex, and redundant network of interactions between tumor, immune, and stromal cells. In this intricate environment, cells communicate through membrane-membrane, ligand-receptor, exosome, soluble factors, and transporter interactions that govern cell fate. These interactions activate the diverse and superfluous signaling pathways involved in tumor promotion and progression and induce subtle changes in the functional activity of infiltrating immune cells. The immune response participates as a selective pressure in tumor development. In the early stages of tumor development, the immune response exerts anti-tumor activity, whereas during the advanced stages, the tumor establishes mechanisms to evade the immune response, eliciting a chronic inflammation process that shows a pro-tumor effect. The deregulated inflammatory state, in addition to acting locally, also triggers systemic inflammation that has repercussions in various organs and tissues that are distant from the tumor site, causing the emergence of various symptoms designated as paraneoplastic syndromes, which compromise the response to treatment, quality of life, and survival of cancer patients. Considering the tumor-host relationship as an integral and dynamic biological system, the chronic inflammation generated by the tumor is a communication mechanism among tissues and organs that is primarily orchestrated through different signals, such as cytokines, chemokines, growth factors, and exosomes, to provide the tumor with energetic components that allow it to continue proliferating. In this review, we aim to provide a succinct overview of the involvement of cancer-related inflammation at the local and systemic level throughout tumor development and the emergence of some paraneoplastic syndromes and their main clinical manifestations. In addition, the involvement of these signals throughout tumor development will be discussed based on the physiological/biological activities of innate and adaptive immune cells. These cellular interactions require a metabolic reprogramming program for the full activation of the various cells; thus, these requirements and the by-products released into the microenvironment will be considered. In addition, the systemic impact of cancer-related proinflammatory cytokines on the liver-as a critical organ that produces the leading inflammatory markers described to date-will be summarized. Finally, the contribution of cancer-related inflammation to the development of two paraneoplastic syndromes, myelopoiesis and cachexia, will be discussed.

Tigecycline-Associated Coagulopathy: A Single-Center Retrospective Analysis

INTRODUCTION

The purpose of this study was to assess clinical characteristics and risk factors for tigecycline-associated prothrombin time (PT) and activated partial thromboplastin time (aPTT) prolongation.

METHODS

We performed a retrospective analysis on coagulation parameters before and during tigecycline treatment in 55 patients in our hospital with severe infections, mainly pneumonia caused by Acinetobacter baumannii. Patients were divided into different groups according to prolongation of PT and aPTT, and clinical features involved were explored. Univariate and multivariable binary logistic regression analyses were used to identify risk factors for tigecycline-associated PT and aPTT increase.

RESULTS

We found that PT values increased from 12.73 ± 1.87 to 13.86 ± 2.06 during the treatment compared with premedication (p < 0.001), and the aPTT level prolonged significantly from 33.63 ± 11.24 to 38.15 ± 11.81 (p < 0.001). The multivariate analyses identified 2 variables that were associated with tigecycline-induced PT prolongation: albumin level (p = 0.018) and weight-adjusted tigecycline dosage (p = 0.005). In addition, treatment duration was the only risk factor for tigecycline-induced aPTT prolongation (p = 0.043).

CONCLUSION

Albumin level, weight-adjusted tigecycline dosage, treatment duration may serve as risk indicators for tigecycline-associated coagulation dysfunction. Physicians should be careful with coagulation disorder when prescribing tigecycline in clinical practice, especially in patients with risk factors.

Sensitivity analysis of a reduced model of thrombosis under flow: Roles of Factor IX, Factor XI, and γ'-Fibrin

A highly reduced extrinsic pathway coagulation model (8 ODEs) under flow considered a thin 15-micron platelet layer where transport limitations were largely negligible (except for fibrinogen) and where cofactors (FVIIa, FV, FVIII) were not rate-limiting. By including thrombin feedback activation of FXI and the antithrombin-I activities of fibrin, the model accurately simulated measured fibrin formation and thrombin fluxes. Using this reduced model, we conducted 10,000 Monte Carlo (MC) simulations for ±50% variation of 5 plasma zymogens and 2 fibrin binding sites for thrombin. A sensitivity analysis of zymogen concentrations indicated that FIX activity most influenced thrombin generation, a result expected from hemophilia A and B. Averaging all MC simulations confirmed both the mean and standard deviation of measured fibrin generation on 1 tissue factor (TF) molecule per μm2. Across all simulations, free thrombin in the layer ranged from 20 to 300 nM (mean: 50 nM). The top 2% of simulations that produced maximal fibrin were dominated by conditions with low antithrombin-I activity (decreased weak and strong sites) and high FIX concentration. In contrast, the bottom 2% of simulations that produced minimal fibrin were dominated by low FIX and FX. The percent reduction of fibrin by an ideal FXIa inhibitor (FXI = 0) ranged from 71% fibrin reduction in the top 2% of MC simulations to only 34% fibrin reduction in the bottom 2% of MC simulations. Thus, the antithrombotic potency of FXIa inhibitors may vary depending on normal ranges of zymogen concentrations. This reduced model allowed efficient multivariable sensitivity analysis.

Curcuma longa extract improves serum inflammatory markers and mental health in healthy participants who are overweight: a randomized, double-blind, placebo-controlled trial

Background

The dietary spice Curcuma longa, also known as turmeric, has various biological effects. Both a water extract and a supercritical carbon dioxide extract of C. longa showed anti-inflammatory activities in animal studies. However, the anti-inflammatory effect in humans of a mixture of these two C. longa extracts (CLE) is poorly understood. Therefore, we investigated the effect of CLE containing anti-inflammatory turmeronols on chronic inflammation and general health.

Methods

We performed a randomized, double-blind, placebo-controlled study in healthy subjects aged 50 to 69 years with overweight. Participants took two capsules containing CLE (CLE group, n = 45) or two placebo capsules (placebo group, n = 45) daily for 12 weeks, and serum inflammatory markers were measured. Participants also completed two questionnaires: the Medical Outcomes Study (MOS) 36-Item Short-Form Health Survey (SF-36) and the Profile of Mood States (POMS) scale. Treatment effects were analyzed by two way analysis of variance followed by a t test (significance level, p <  0.05).

Results

After the intervention, the CLE group had a significantly lower body weight (p <  0.05) and body mass index (p < 0.05) than the placebo group and significantly lower serum levels of C-reactive protein (p < 0.05) and complement component 3 (p < 0.05). In addition, the CLE group showed significant improvement of the MOS SF-36 mental health score (p < 0.05) and POMS anger-hostility score (p < 0.05).

Conclusion

CLE may ameliorate chronic low-grade inflammation and thus help to improve mental health and mood disturbance.

Trial registration

UMIN-CTR, UMIN000037370. Registered 14 July 2019, https://upload.umin.ac.jp/cgi-open-bin/ctr/ctr_view.cgi?recptno=R000042607

Supplementary Information

The online version contains supplementary material available at 10.1186/s12937-021-00748-8.

Thrombin-Fibrin(ogen) Interactions, Host Defense and Risk of Thrombosis

Fibrinogen is a well-known risk factor for arterial and venous thrombosis. Its function is not restricted to clot formation, however, as it partakes in a complex interplay between thrombin, soluble plasma fibrinogen, and deposited fibrin matrices. Fibrinogen, like thrombin, participates predominantly in hemostasis to maintain vascular integrity, but executes some important pleiotropic effects: firstly, as observed in thrombin generation experiments, fibrin removes thrombin from free solution by adsorption. The adsorbed thrombin is protected from antithrombins, notably α2-macroglobulin, and remains physiologically active as it can activate factors V, VIII, and platelets. Secondly, immobilized fibrinogen or fibrin matrices activate monocytes/macrophages and neutrophils via Mac-1 interactions. Immobilized fibrin(ogen) thereby elicits a pro-inflammatory response with a reciprocal stimulating effect of the immune system on coagulation. In contrast, soluble fibrinogen prohibits recruitment of these immune cells. Thus, while fibrin matrices elicit a procoagulant response, both directly by protecting thrombin and indirectly through the immune system, high soluble fibrinogen levels might protect patients due to its immune diminutive function. The in vivo influence of the 'protective' plasma fibrinogen versus the 'pro-thrombotic' fibrin matrices on thrombosis should be explored in future research.

γ' fibrinogen levels are associated with blood clot strength in traumatic brain injury patients

BACKGROUND

γ' fibrinogen is an alternatively-spliced fibrinogen variant that displays different coagulation parameters in vitro than the major form of fibrinogen. Purified γ' fibrinogen has slower clotting kinetics than unfractionated fibrinogen, but forms clots that are stronger and resistant to fibrinolysis. However, these properties have only been investigated in human populations in a limited number of studies. We therefore performed a retrospective analysis to test the hypothesis that γ' fibrinogen levels influence coagulation in vivo.

METHODS

In the present study, we utilized blood samples that were collected from traumatic brain injury patients to probe the relationship between γ' fibrinogen levels and traditional coagulation parameters.

RESULTS

The results show that the levels of γ' fibrinogen were inversely associated with clotting kinetics, indicated by a shortened INR. In addition, the levels of γ' fibrinogen were associated with stronger clots by thrombelastography. However, these changes were not associated with significant changes in hemorrhage progression.

CONCLUSIONS

These findings verify that γ' fibrinogen properties observed in purified systems result in similar properties in a clinical setting, and may affect coagulation.

Ligustrazine reverts anthracycline chemotherapy resistance of human breast cancer by inhibiting JAK2/STAT3 signaling and decreasing fibrinogen gamma chain (FGG) expression

Chemotherapy resistance is a major challenge for breast cancer treatment. It is necessary to elucidate the mechanisms of anthracycline resistance to develop new chemosensitizers for breast cancer. In this study, we explored the effects of ligustrazine (TMP) on reverting anthracycline resistance of breast cancer cells, as well as its related mechanisms. Clinical significance of fibrinogen gamma chain (FGG) expression was also analyzed in breast cancer tissues. We provided evidence that breast tumor cell derived FGG participated in anthracycline chemoresistance of breast cancer. Further, TMP reverted epirubicin resistance by inhibiting JAK2/STAT3 signaling and decreasing FGG expression. Meanwhile, the elimination of cancer stem cell was observed in TMP treated chemoresistant breast cancer cells. Clinical analysis demonstrated that patients with FGG expressing breast cancer showed a dramatically low response to anthracycline-based chemotherapy and poor survival. Our data collectively indicated that FGG was an independent detrimental factor for anthracycline based chemotherapy for breast cancer patients. TMP was a novel chemosensitizer for FGG-induced anthracycline chemoresistance in breast cancer treatment.

The FDP/FIB Ratio and Blood FDP Level May Be Related to Seizures After Fever in Young Children

Objective: To evaluate the relationship of the blood fibrinogen (FIB) degradation product (FDP) level and FDP/FIB ratio with seizure in young children with fever. Methods: A total of 35 children with simple febrile seizures and 80 children with fever but no seizure were selected. First, the differences in white blood cell (WBC), platelets (PLT), prothrombin time (PT), activated partial thromboplastin time (APTT), thrombin time (TT), FIB, FDP, FDP/FIB ratio, and C-reactive protein (CRP) between 35 children with simple febrile seizures and 40 randomly selected children with fever but no seizure were retrospectively analyzed. Then, an ROC curve was used to determine the diagnostic utility of the FDP level, FDP/FIB ratio, and FDP+FDP/FIB ratio, and the best diagnostic cutoff points were selected. Finally, the diagnostic specificities of the three diagnostic indicators were verified by comparison with the results of all 80 children with fever but no seizure. Results: The FDP level and FDP/FIB ratio were significantly different between the two groups (P < 0.0001) and there was a positive correlation between the FDP and FIB levels. Both the FDP level and FDP/FIB ratio had good diagnostic value. An FDP ≥ 2.0 mg/L and FDP/FIB ratio ≥ 0.5 had good diagnostic specificities. Combined application of an FDP ≥ 2.0 mg/L and FDP/FIB ratio ≥ 0.5 improved the diagnostic power. Conclusions: The blood FDP level and FDP/FIB ratio may be related to seizures after fever, and an FDP ≥ 2.0 mg/L + FDP/FIB ratio ≥ 0.5 has good diagnostic specificity.

Uncovering the protective mechanism of Huoxue Anxin Recipe against coronary heart disease by network analysis and experimental validation

Coronary heart disease (CHD) is a leading cause of death and disability worldwide. Huoxue Anxin Recipe (HAR) is a novel Chinese Herbal Medicine formula of that has been used to treat CHD for several decades. Our previous study found that HAR had anti-oxidative effects, and could promote myocardial angiogenesis and improve cardiac function following myocardial infarction (MI) in rats. However, the active compounds, potential targets, and biological processes related to HAR have not been systematically investigated. Here, network pharmacology and experimental validation were used to study the protective mechanisms of HAR against CHD. We identified 124 active components, 124 verified targets, and 111 predictive targets. A total of 1192 genes related to CHD were identified by cDNA microarray and database analysis. A total of 47 putative targets of HAR against CHD were identified, including 32 verified targets and 15 predictive targets. ClueGo enrichment analysis identified 49 biological processes involved in the anti-CHD effects of HAR. Among them, the negative regulation of blood coagulation and regulation of collagen biosynthetic process were experimentally validated. After constructing a protein-protein interaction network and clustering with MECODE and ClusterONE, 162 key proteins (from ClueGo and clustering) were used to construct an internal interaction network. Complement C3 (C3), Fibrinogen alpha (FGA), Fibrinogen gamma (FGG), interleukin-6 (IL6), and Apolipoprotein A1 (APOA1) were the top 5 hub proteins identified by cytoHubber analysis. HAR limited the concentrations of C3, FGA, FGG, and IL6 and increased APOA1 levels. The results indicated that HAR could down-regulate blood coagulation, regulate collagen biosynthesis, inhibit peroxidation and inflammation injury, and promote cholesterol efflux. HAR could be a potential source of novel and effective drugs for CHD.

Fibrin γ/γ' influences the secretion of fibrinolytic components and clot structure

Background

In healthy subjects fibrinogen γ/γ‘ circulates at 8–15% of the total plasma fibrinogen concentration. Elevated levels of this variant have been associated with arterial thrombosis, and its diminution with venous thrombosis. The aims of the present work were to analyze the structure of the fibrin network formed on the top of human dermal microvascular endothelial cells (HMEC-1) at different fibrinogen γ/γ‘ concentrations, as well as its influence on the secretion of fibrinolytic components.

The kinetics of fibrin polymerization on top of HMEC-1 cells with 3, 10, and 30% fibrinogen γ/γ‘ was followed at 350 nm. The secretion of urokinase-type plasminogen activator (uPA) and plasminogen activator inhibitor type 1 (PAI 1) by HMEC-1 were measured in the supernatant and cell lysates, after incubation with 1 nM thrombin, fibrin with 3, and 30% fibrinogen γ/γ‘, using commercial kits. The influence of fibrinogen γ/γ‘ on fibrin structure on the surface of the HMEC-1 was followed with laser scanning confocal microscopy (LSCM).

Results

The kinetics of fibrin formation on HMEC-1 with 3 and 10% fibrinogen γ/γ‘ were similar. However, with 30% fibrinogen γ/γ‘ both the slope and final turbity were approximately 50% less. The LSCM images showed the dramatic effects of increasing fibrinogen γ/γ‘ from 3 to 30%. The uPA and PAI 1 concentrations in culture supernatants HMEC-1 cells treated with thrombin or 30% γ/γ‘ fibrin were two-fold increased as compared to basal culture supernatants and 3% γ/γ‘ fibrin-treated HMEC-1. In all stimulatory conditions the intracellular concentration of uPA was higher than in supernatants. In contrast, the intracellular PAI 1 concentration was decreased as compared to that measured in the supernatant, including the basal condition.

Conclusion

A concentration of 30% fibrin γ/γ‘ alter drastically fibrin structure on the cell surface and affects the secretion of uPA and PAI 1 through its capacity to bind thrombin.

Integration of "Omics" Strategies for Biomarkers Discovery and for the Elucidation of Molecular Mechanisms Underlying Brugada Syndrome

PURPOSE

The Brugada syndrome (BrS) is a severe inherited cardiac disorder. Given the high genetic and phenotypic heterogeneity of this disease, three different "omics" approaches are integrated in a synergic way to elucidate the molecular mechanisms underlying the pathophysiology of BrS as well as for identifying reliable diagnostic/prognostic markers.

EXPERIMENTAL DESIGN

The profiling of plasma Proteome and MiRNome is perfomed in a cohort of Brugada patients that were preliminary subjected to genomic analysis to assess a peculiar gene mutation profile.

RESULTS

The integrated analysis of "omics" data unveiled a cooperative activity of mutated genes, deregulated miRNAs and proteins in orchestrating transcriptional and post-translational events that are critical determining factors for the development of the Brugada pattern.

CONCLUSIONS AND CLINICAL RELEVANCE

This study provides the basis to shed light on the specific molecular fingerprints underlying BrS development and to gain further insights on the pathogenesis of this life-threatening cardiac disease.

Fetuin B links vitamin D deficiency and pediatric obesity: Direct negative regulation by vitamin D

Vitamin D (VD) deficiency (VDD) correlates to obesity, with VD a recognized mediator of metabolic diseases. From a previous proteomic study identifying adiponectin as a link between VDD and pediatric obesity, herein we analysed another protein (SSP2301) increased with VDD. A focused 2D-electrophoretic analysis identified 4 corresponding plasma proteins, with one predicted to be fetuin B (FETUB). FETUB was studied due to its emerging role in metabolic diseases and cytogenetic location (3q27.3) with adiponectin. Results were confirmed in obese children, where plasma FETUB was higher with VDD. A direct effect by 1α,25-(OH)2D3 on hepatocellular FETUB synthesis was observed, with a time and dose dependent reduction. Further, we demonstrated the VD-receptor (VDR) is key, with FETUB "released" with VDR silencing. Finally, VD supplementation (6weeks) to juvenile mice fed a standard diet, reduced plasma FETUB. Only at 22weeks did liver FETUB correspond to plasma FETUB, highlighting the contribution of other VD-responsive tissues. Overall, FETUB is a key protein linking VDD to pediatric obesity. With an emerging role in metabolic diseases, we demonstrate that VD/VDR directly regulate FETUB.

Fibrinogen and clot-related phenotypes determined by fibrinogen polymorphisms: Independent and IL-6-interactive associations

Interleukin-6 (IL-6) induces the expression of fibrinogen, and polymorphic variation within the fibrinogen genes is believed to alter the magnitude of this expression. The identification of the functional relevance of individual fibrinogen single nucleotide polymorphisms (SNPs) has been hindered by the high linkage disequilibrium (LD) reported in the European fibrinogen gene locus. This study investigated two novel and 12 known fibrinogen SNPs of potential functional relevance, in 2010 Tswana individuals known to have low LD. We aimed to identify functional polymorphisms that contribute to clot-related phenotypes and total and γ’ fibrinogen concentrations independently and through their interaction with IL-6, by taking advantage of the high fibrinogen and IL-6 concentrations and the low LD reported in black South Africans. Fibrinogen was significantly associated with IL-6, thereby mediating associations of IL-6 with clot formation and structure, although attenuating the association of IL-6 with clot lysis time. None of the common European fibrinogen haplotypes was present in this study population. Putative functional fibrinogen SNPs FGB–rs7439150, rs1800789 (–1420_G/A) and rs1800787 (–148_C/T) were significantly associated with fibrinogen concentration and altered clot properties, with several associations significantly influenced by IL-6 concentrations. The impact of harbouring several minor fibrinogen SNP alleles on the association of IL-6 and fibrinogen concentration was cumulative, with possession of each additional minor allele showing a stronger relationship of IL-6 with fibrinogen. This was also reflected in differences in clot properties, suggesting potential clinical relevance. Therefore, when investigating the effect of fibrinogen genetics on fibrinogen concentrations and CVD outcome, the possible interactions with modulating factors and the fact that SNP effects seem to be additive should be taken into account.

Lack of association of plasma gamma prime (γ') fibrinogen with incident cardiovascular disease

INTRODUCTION

The association of gamma prime (γ') fibrinogen; a fibrinogen γ chain variant generated via alternative mRNA processing, with cardiovascular disease (CVD) remains equivocal. We prospectively examine the association of plasma γ' fibrinogen with the incidence of multiple cardiovascular disease (CVD) endpoints, independent of established CVD risk factors and total fibrinogen.

MATERIALS AND METHODS

We measured plasma γ' fibrinogen on plasma samples collected in 1992-1993 from adults ≥65years (n=3219) enrolled in the Cardiovascular Health Study, who were followed through 2013 for incident CVD events.

RESULTS AND CONCLUSIONS

In multivariable Cox models adjusted for traditional CVD risk factors and total fibrinogen, the hazard ratio per 1 standard deviation (10.7mg/dl) increment of γ' fibrinogen was 1.02 (95%CI: 0.95-1.10) for coronary heart disease; 0.88 (0.77-1.00) for ischemic stroke; 1.07 (0.87-1.32) for peripheral artery disease; 1.00 (0.92-1.08) for heart failure and 1.01 (0.92-1.10) for CVD mortality. Likewise, we failed to show a statistically significant association of γ'/total fibrinogen ratio with any CVD endpoint. These results suggest that among the elderly, γ' fibrinogen does not add much to CVD prediction beyond traditional risk factors and total fibrinogen level.

Association of Plasma γ' Fibrinogen With Incident Cardiovascular Disease: The Atherosclerosis Risk in Communities (ARIC) Study

OBJECTIVES

To prospectively examine the association of plasma γ' fibrinogen with the incidence of multiple cardiovascular disease (CVD) end points, independent of established CVD risk factors, total fibrinogen, and other inflammatory markers.

APPROACH AND RESULTS

The Atherosclerosis Risk in Communities (ARIC) study measured γ' fibrinogen by enzyme-linked immunosorbent assay in stored plasma samples from 1993 to 1995 and related levels in 10 601 adults to incident CVD end points (coronary heart disease [n=1603], ischemic stroke [n=548], peripheral artery disease [n=599], heart failure [n=1411], and CVD mortality [n=705]) through 2012 (median follow-up, 18 years). In Cox models accounting for established CVD risk factors and total fibrinogen levels, γ' fibrinogen was associated positively with peripheral artery disease (hazard ratio [HR] per 1-SD [8.80 mg/dL] increment, 1.14 [1.04-1.24]), heart failure (HR, 1.06 [1.01-1.13]), and CVD deaths (HR, 1.12 [1.04-1.21]) but not with incident coronary heart disease (HR, 1.01 [0.96-1.07]) or ischemic stroke (HR, 0.98 [0.89-1.07]). Additional adjustment for C-reactive protein, however, eliminated the associations with peripheral artery disease and heart failure.

CONCLUSIONS

These findings do not lend support to the hypothesis that γ' fibrinogen influences CVD events through its prothrombotic properties. Rather, γ' fibrinogen concentrations seem to reflect general inflammation that accompanies and may contribute to atherosclerotic CVD, instead of γ' fibrinogen being a causal risk factor.

Fibrinogen, red blood cells, and factor XIII in venous thrombosis

Cardiovascular disease is the leading cause of death and disability worldwide. Among cardiovascular causes of death, venous thrombosis (VT) is ranked third most common in the world. Venous thrombi have high red blood cell and fibrin content; however, the pathophysiologic mechanisms that contribute to venous thrombus composition and stability are still poorly understood. This article reviews biological, biochemical, and biophysical contributions of fibrinogen, factor XIII, and red blood cells to VT, and new evidence suggesting interactions between these components mediate venous thrombus composition and size.

Fibrin, γ'-fibrinogen, and transclot pressure gradient control hemostatic clot growth during human blood flow over a collagen/tissue factor wound

OBJECTIVE

Biological and physical factors interact to modulate blood response in a wounded vessel, resulting in a hemostatic clot or an occlusive thrombus. Flow and pressure differential (ΔP) across the wound from the lumen to the extravascular compartment may impact hemostasis and the observed core/shell architecture. We examined physical and biological factors responsible for regulating thrombin-mediated clot growth.

APPROACH AND RESULTS

Using factor XIIa-inhibited human whole blood perfused in a microfluidic device over collagen/tissue factor at controlled wall shear rate and ΔP, we found thrombin to be highly localized in the P-selectin(+) core of hemostatic clots. Increasing ΔP from 9 to 29 mm Hg (wall shear rate=400 s(-1)) reduced P-selectin(+) core size and total clot size because of enhanced extravasation of thrombin. Blockade of fibrin polymerization with 5 mmol/L Gly-Pro-Arg-Pro dysregulated hemostasis by enhancing both P-selectin(+) core size and clot size at 400 s(-1) (20 mm Hg). For whole-blood flow (no Gly-Pro-Arg-Pro), the thickness of the P-selectin-negative shell was reduced under arterial conditions (2000 s(-1), 20 mm Hg). Consistent with the antithrombin-1 activity of fibrin implicated with Gly-Pro-Arg-Pro, anti-γ'-fibrinogen antibody enhanced core-localized thrombin, core size, and overall clot size, especially at venous (100 s(-1)) but not arterial wall shear rates (2000 s(-1)). Pathological shear (15 000 s(-1)) and Gly-Pro-Arg-Pro synergized to exacerbate clot growth.

CONCLUSIONS

Hemostatic clotting was dependent on core-localized thrombin that (1) triggered platelet P-selectin display and (2) was highly regulated by fibrin and the transclot ΔP. Also, γ'-fibrinogen had a role in venous but not arterial conditions.

Prognostic utility of biochemical markers of cardiovascular risk: impact of biological variability

BACKGROUND

Although a variety of biochemical markers are used to help predict the risk of cardiovascular disease, the prognostic utility of any marker used as a risk assessment tool is dependent on the long- and short-term biological variability that the marker shows in different individuals.

METHODS

We measured total, low-density lipoprotein (LDL), and high-density lipoprotein (HDL) cholesterol; triglycerides; high-sensitivity C-reactive protein (hsCRP); total fibrinogen; and γ' fibrinogen in blood samples collected from 15 apparently healthy individuals over the course of 1 year. Repeated measures variation estimates were used to calculate short- and long-term intraclass correlation coefficients (ICC), within- and between-subject coefficients of variation (CVI and CVG, respectively), validity coefficients, and indices of individuality for each marker.

RESULTS

HDL cholesterol demonstrated the lowest variability profile, with an ICC of 0.84 and CVI of 11.1 (95% CI: 8.3, 17.0). hsCRP showed the highest levels of short- and long-term within-subject variability [CVI (95% CI): 54.8 (32.8, 196.3) and 77.1 (53.3, 141.3), respectively]. Stated differently, it would require five separate measurements of hsCRP, performed on samples collected over multiple days, to provide the risk assessment information provided by a single measurement of HDL cholesterol. γ' Fibrinogen demonstrated an ICC of 0.79 and CVI of 14.3 (95% CI: 10.6, 21.9).

CONCLUSIONS

hsCRP showed very high biological variability, such that a single measurement of hsCRP lacks sufficient clinical utility to justify routine measurement. The variability profile of γ' fibrinogen was not markedly different than HDL cholesterol, necessitating only a limited number of measurements to establish an individual's risk of cardiovascular disease.

The fibrinogen γA/γ' isoform does not promote acute arterial thrombosis in mice

BACKGROUND

Elevated plasma fibrinogen is associated with arterial thrombosis in humans and promotes thrombosis in mice by increasing fibrin formation and thrombus fibrin content. Fibrinogen is composed of six polypeptide chains: (Aα, Bβ, and γ)2. Alternative splicing of the γ chain leads to a dominant form (γA/γA) and a minor species (γA/γ'). Epidemiological studies have detected elevated γA/γ' fibrinogen in patients with arterial thrombosis, suggesting that this isoform promotes thrombosis. However, in vitro data show that γA/γ' is anticoagulant due to its ability to sequester thrombin and suggest its expression is upregulated in response to inflammatory processes.

OBJECTIVE

To determine whether γA/γ' fibrinogen is prothrombotic in vivo.

METHODS

We separated γA/γA and γA/γ' fibrinogen from human plasma-purified fibrinogen and determined the effects on in vitro plasma clot formation and on in vivo thrombus formation and circulating thrombin-antithrombin complexes in mice.

RESULTS AND CONCLUSIONS

Both γA/γA and γA/γ' fibrinogen were cleaved by murine and human thrombin and were incorporated into murine and human clots. When γA/γA or γA/γ' was spiked into plasma, γA/γA increased the fibrin formation rate to a greater extent than γA/γ'. In mice, compared to controls, γA/γA infusion shortened the time to carotid artery occlusion, whereas γA/γ' infusion did not. Additionally, γA/γ' infusion led to lower levels of plasma thrombin-antithrombin complexes following arterial injury, whereas γA/γA infusion did not. These data suggest that γA/γ' binds thrombin in vivo and decreases prothrombotic activity. Together, these findings indicate that elevated levels of γA/γA fibrinogen promote arterial thrombosis in vivo, whereas γA/γ' does not.

Obesity-related increased γ' fibrinogen concentration in children and its reduction by a physical activity-based lifestyle intervention: a randomized controlled study

OBJECTIVE

To determine if elevated plasma γ'-fibrinogen, typically involved in the formation of fibrinolysis-resistant clots, confers an increased risk for cardiovascular disease (CVD) and thrombosis in children as it does in adults. Although obesity-related hyperfibrinogenemia is frequently reported in children, the role of γ' fibrinogen and its response to physical activity-based lifestyle are less clear in this population.

STUDY DESIGN

In a randomized controlled 3-month physical activity-based lifestyle intervention, γ' fibrinogen concentration was measured in 21 children (aged 14-18 years; Tanner stage > IV), including 15 in the obese group and 6 in the normal weight group, with body mass index percentiles for age and sex of >95 and <85, respectively.

RESULTS

The relationships between γ' fibrinogen and other risk factors for CVD, such as markers of insulin resistance and subclinical inflammation, along with body composition (as measured by dual-energy X-ray absortiometry), were assessed before and after the intervention. γ' fibrinogen concentration was higher in the obese group compared with the normal weight group (P < .05) and was correlated with other risk factors for CVD (adjusted R(2) = 0.9; P < .05), and insulin emerged as the major predictor of γ' fibrinogen. The intervention reduced γ'-fibrinogen concentration (P < .05).

CONCLUSION

Our data reveal: (1) elevated γ' fibrinogen concentrations in obese insulin-resistant children compared with normal lean controls; (2) a relationship between γ' fibrinogen and other CVD risk factors; and (3) physical activity-induced reduction in γ' fibrinogen in obese children.