Genetic polymorphisms influencing total and γ′ fibrinogen levels and fibrin clot properties in Africans

A comprehensive exploration of chronic kidney disease and dialysis in Canada's Indigenous population: from epidemiology to genetic influences

PURPOSE

This study aims to review the escalating prevalence of chronic kidney disease (CKD) and end-stage renal disease (ESRD) among Canada's Indigenous population, focusing on risk factors, hospitalization and mortality rates, and disparities in kidney transplantation. The study explores how these factors contribute to the health outcomes of this population and examines the influence of genetic variations on CKD progression.

METHODS

The review synthesizes data on prevalence rates, hospitalization and mortality statistics, and transplantation disparities among Indigenous individuals. It also delves into the complexities of healthcare access, including geographical, socioeconomic, and psychological barriers. Additionally, the manuscript investigates the impact of racial factors on blood characteristics relevant to dialysis treatment and the genetic predispositions influencing disease progression in Indigenous populations.

RESULTS

Indigenous individuals exhibit a higher prevalence of CKD and ESRD risk factors such as diabetes and obesity, particularly in regions like Saskatchewan. These patients face a 77% higher risk of death compared to their non-Indigenous counterparts and are less likely to receive kidney transplants. Genetic analyses reveal significant associations between CKD and specific genomic variations. Through analyses, we found that healthy Indigenous individuals may have higher levels of circulating inflammatory markers, which could become further elevated for those with CKD. In particular, they may have higher levels of C-reactive protein (CRP) fibrinogen, as well as genomic variations that affect IL-6 production and the function of von Willebrand Factor (vWF) which has critical potential influence on the compatibility with dialysis membranes contributing to complications in dialysis.

CONCLUSION

Indigenous people in Canada are disproportionately burdened by CKD and ESRD due to socioeconomic factors and potential genetic predispositions. While significant efforts have been made to assess the socioeconomic conditions of the Indigenous population, the genetic factors and their potential critical influence on compatibility with dialysis membranes, contributing to treatment complications, remain understudied. Further investigation into these genetic predispositions is essential.

Whole-Exome Sequencing in a Family with an Unexplained Tendency for Venous Thromboembolism: Multicomponent Prediction of Low-Frequency Variant Deleteriousness and of Individual Protein Interaction

Whole-exome sequencing (WES) in families with an unexplained tendency for venous thromboembolism (VTE) may favor detection of low-frequency variants in genes with known contribution to hemostasis or associated with VTE-related phenotypes. WES analysis in six family members, three of whom affected by documented VTE, filtered for MAF < 0.04 in 192 candidate genes, revealed 22 heterozygous (16 missense and six synonymous) variants in patients. Functional prediction by multi-component bioinformatics tools, implemented by a database/literature search, including ClinVar annotation and QTL analysis, prioritized 12 missense variants, three of which (CRP Leu61Pro, F2 Asn514Lys and NQO1 Arg139Trp) were present in all patients, and the frequent functional variants FGB Arg478Lys and IL1A Ala114Ser. Combinations of prioritized variants in each patient were used to infer functional protein interactions. Different interaction patterns, supported by high-quality evidence, included eight proteins intertwined in the "acute phase" (CRP, F2, SERPINA1 and IL1A) and/or in the "fibrinogen complex" (CRP, F2, PLAT, THBS1, VWF and FGB) significantly enriched terms. In a wide group of candidate genes, this approach highlighted six low-frequency variants (CRP Leu61Pro, F2 Asn514Lys, SERPINA1 Arg63Cys, THBS1 Asp901Glu, VWF Arg1399His and PLAT Arg164Trp), five of which were top ranked for predicted deleteriousness, which in different combinations may contribute to disease susceptibility in members of this family.

Association of Genetic Polymorphisms of Fibrinogen, Factor XIII A-Subunit and α2-Antiplasmin with Fibrinogen Levels in Pregnant Women

Fibrinogen synthesis is stimulated by proinflammatory triggers and depends on α-, β- and γ-fibrinogen (FGA, FGB, FGG) genotypes. Constellations of fibrinogen, factor XIII A-subunit (F13A) and α₂-antiplasmin (A2AP) genotypes predisposing for dense fibrin gels with high antifibrinolytic capacity (e.g., FGB rs1800790 A-allele carriage in F13A 34Val/Val or A2AP 6Arg/Arg wildtypes) are related with reduced inflammation. As both relationships are likely to influence each other, we tested whether the association of fibrinogen genotypes with fibrinogen levels is influenced by F13A and A2AP genotypes in a population under proinflammatory stress. In total, 639 women were followed during pregnancy (2218 observations). The relationship between fibrinogen genotypes and levels was statistically assessed in univariate and multivariate analyses without and with stratification for F13A Val34Leu and A2AP Arg6Trp. Strong associations with fibrinogen levels could be found for FGB rs1800790G > A, FGA rs2070016T > C and FGG rs1049636T > C. For FGB rs1800790G > A and FGA rs2070016T > C, this relationship significantly depended on F13A Val34Leu and A2AP Arg6Trp genotypes. Specifically, in F13A 34Val/Val wildtypes, carriage of FGB rs1800790A was related to significantly lower fibrinogen levels compared with FGB rs1800790GG wildtypes (p < 0.01). For A2AP 6Arg/Arg wildtypes, a comparable relationship could be found (p < 0.04). As these genotype constellations related to lower fibrinogen levels have previously been shown to be associated with reduced inflammatory activity, these findings suggest that the influence of fibrinogen, F13A and A2AP genotypes on inflammation could affect the control of fibrinogen levels and vice versa.

The Correlation Between FGB Promoter Polymorphism and Clotting Function in Patients With Idiopathic Lower Extremity Deep Venous Thrombosis

To explore the possible single nucleotide polymorphisms (SNPs) sites in the promoter region of fibrinogen B β (FGB), and construct logistic regression model and haplotype model, so as to reveal the influence of FGB promoter SNPs on susceptibility, hemodynamics and coagulation function of lower extremity deep venous thrombosis (LEDVT) in the genetic background. LEDVT patients (120) and healthy people (120) were taken as case and control objects, respectively. SNPs and their genotypes of FGB promoter were detected by promoter sequencing and PCR-RFLP. The parameters of coagulation system were evaluated. There were 6 SNPs in FGB promoter, which were β-148C/T, β-249C/T, β-455G/A, β-854G/A, β-993C/T and β-1420G/A. The genotype and allele frequency of β-1420 G/A, β-455G/A, β-249c/T and β-148C/T were significantly different between the LEDVT group and the control group, but not β-993C/T and β-854G/A. In addition, we found that the higher the content of Fibrinogen (FG), the higher the risk of LEDVT. The risk of LEDVT increased by 4.579 times for every unit increase of fibrinogen. We also found that FG, PT and APTT in LEDVT group were higher than those in control group, while TT was lower than those in control group; Furthermore, there was no significant difference in all coagulation indexes among 6 SNP genotypes in LEDVT group, while a significant difference was found between the 2 genotypes of β-993C/T in the control group. β-993C/T may indirectly affect the susceptibility of LEDVT by improving the basic level of plasma FG.

Mechanisms of fibrinolysis resistance and potential targets for thrombolysis in acute ischaemic stroke: lessons from retrieved stroke emboli

There has been growing interest and insight into the histological composition of retrieved stroke emboli. One of the main focuses of the stroke clot analysis literature has been the implications of clot composition on mechanical thrombectomy procedures. However, the holy grail of clot analysis may not be in the field of clot–device interaction, but rather, in understanding mechanisms of fibrinolysis resistance. The mechanisms underlying the low response to fibrinolytic therapy, even with the newer, more powerful agents, remain poorly understood. While factors such as embolus size, location and collateral status influence alteplase delivery and recanalisation rates; compositional analyses focused on histological and ultrastructural characteristics offer unique insights into mechanisms of alteplase resistance. In this review, we strive to provide comprehensive review of current knowledge on clot composition and ultrastructural analyses that help explain resistance to fibrinolysis.

Dysfibrinogenemia-Potential Impact of Genotype on Thrombosis or Bleeding

The congenital dysfibrinogenemias, most often associated with bleeding disorders, encompass mutations in the amino-terminal end of fibrinogen α-chain consisting of Gly17-Pro18-Arg19-Val20, known as knob A, which is a critical site for fibrin polymerization. Here we review the studies reporting dysfibrinogenemia due to mutations affecting fibrinogen knob A and identified 29 papers. The number of reports on dysfibrinogenemias related to residues Gly17, Pro18, Arg19, and Val20 is 5, 4, 18, and 2, respectively. Dysfibrinogenemias related to residues Gly17, Pro18, and Val20 are exclusively associated with bleeding tendency. However, the clinical picture associated with dysfibrinogenemia related to residue Arg19 varies, with most patients suffering from bleeding tendencies, but also transitory ischemic attacks and retinal thrombosis may occur. The reason for this variation is unclear. To elaborate the genotype-phenotype associations further, we studied a Danish family with knob A-related dysfibrinogenemia caused by the Aα Arg19Gly (p.Arg19Gly) mutation using whole-exome sequencing and fibrin structure analysis. Our family is the first reported carrying the p.Arg19Gly mutation combined with one or more single nucleotide polymorphisms (SNP)s in FGA, FGB, and/or FGG and increased fibrin fiber thickness and fibrin mass-to-length ratio suffering from pulmonary emboli, suggesting that compound genotypes may contribute to the thrombogenic phenotype of these patients. Our review, accordingly, focuses on significance of SNPs, compound genotypes, and fibrin structure measures affecting the genotype-phenotype associations in fibrinogen knob A mutations.

Lifestyle Influences Changes in Fibrin Clot Properties Over a 10-Year Period on a Population Level

Case-control and observational studies have provided a plausible mechanistic link between clot structure and thrombosis. We aimed to identify lifestyle, demographic, biochemical, and genetic factors that influence changes in total fibrinogen concentration and clot properties over a 10-year period in 2,010 black South Africans. Clot properties were assessed with turbidimetry and included lag time, slope, maximum absorbance, and clot lysis time. Linear mixed models with restricted maximum likelihood were used to determine whether (1) outcome variables changed over the 10-year period; (2) demographic and lifestyle variables, biochemical variables, and fibrinogen single-nucleotide polymorphisms influenced the change in outcome variables over the 10-year period; and (3) there was an interaction between the exposures and time in predicting the outcomes. A procoagulant risk score was furthermore created, and multinomial logistic regression was used to determine the exposures that were associated with the different risk score categories. In this population setting, female gender, obesity, poor glycemic control, increased low-density lipoprotein cholesterol, and decreased high-density lipoprotein cholesterol contributed to the enhanced progression to prothrombotic clot properties with increasing age. Alcohol consumption on the other hand, offered a protective effect. The above evidence suggest that the appropriate lifestyle changes can improve fibrin clot properties on a population level, decreasing cardiovascular disease risk and thus alleviate the strain on the medical health care system.

Hepatic fibrinogen storage disease and hypofibrinogenemia caused by fibrinogen Aguadilla mutation: a case report

Hepatic fibrinogen storage disease is a rare autosomal dominant genetic disorder characterized by hypofibrinogenemia, as well as the retention of variant fibrinogen within the hepatocellular endoplasmic reticulum. Here, we describe an asymptomatic 4-year-old boy with abnormal liver function test results and unexpected hypofibrinogenemia. Liver biopsy showed circular eosinophil inclusion bodies in the hepato-cytoplasm. Immunostaining results of eosinophil inclusion bodies were positive for fibrinogen. Following pretreatment with diastase, the inclusion bodies failed to stain with the periodic acid–Schiff technique; moreover, immunostaining results were positive for fibrinogen, but negative for alpha-1-antitrypsin. Genetic analysis identified a heterozygous missense mutation c.1201C > T (p. Arg401Trp) within the fibrinogen γ-chain (FGG) gene and an additional single nucleotide polymorphism c.-58 A > G within the 5′-untranslated region of the fibrinogen Aα-chain (FGA) gene. Thus, the patient was diagnosed with hepatic fibrinogen storage disease. Our results indicate that, for patients who exhibit chronic liver disease with unexpected hypofibrinogenemia, hepatic fibrinogen storage disease should be considered in the differential diagnosis. Moreover, our findings emphasize the importance of molecular diagnosis in patients with cryptogenic liver disease.

Plasma phospholipid fatty acids are associated with altered fibrin clot properties in a population-based setting

Evidence regarding the relationship of plasma clot properties with fatty acids is contradictory, owing to different experimental protocols employed. The relationship of fibrinogen and plasma fibrin clot properties with plasma phospholipid fatty acids were cross-sectionally investigated in a population-based setting in 900 individuals. Composite saturated fatty acids (driven by stearic acid) and composite n-3 and n-6 polyunsaturated fatty acids (driven by docosahexaenoic and arachidonic acid respectively) were associated with prothrombotic clot properties. Composite monounsaturated fatty acids (driven by oleic acid) were associated with a profibrinolytic clot phenotype. Fibrinogen and BMI partly mediated these relationships. Individual plasma fatty acids from the same composite group had opposing associations with clot properties indicating that associations with composite fatty acid groups is dependent on the relative composition of the comprising fatty acids. The relationship of the plasma phospholipid fatty acid profile with disease should not be interpreted without considering the role of regulatory mechanisms.

microRNAs in the haemostatic system: More than witnesses of thromboembolic diseases?

MicroRNAs (miRNAs) are small endogenous RNAs that post-transcriptionally regulate gene expression. In the last few years, these molecules have been implicated in the regulation of haemostasis, and an increasing number of studies have investigated their relationship with the development of thrombosis. In this review, we discuss the latest developments regarding the role of miRNAs in the regulation of platelet function and secondary haemostasis. We also discuss the genetic and environmental factors that regulate miRNAs. Finally, we address the potential use of miRNAs as prognostic and diagnostic tools in thrombosis.

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.

Cardiovascular Health in African Americans: A Scientific Statement From the American Heart Association

BACKGROUND AND PURPOSE

Population-wide reductions in cardiovascular disease incidence and mortality have not been shared equally by African Americans. The burden of cardiovascular disease in the African American community remains high and is a primary cause of disparities in life expectancy between African Americans and whites. The objectives of the present scientific statement are to describe cardiovascular health in African Americans and to highlight unique considerations for disease prevention and management.

METHOD

The primary sources of information were identified with PubMed/Medline and online sources from the Centers for Disease Control and Prevention.

RESULTS

The higher prevalence of traditional cardiovascular risk factors (eg, hypertension, diabetes mellitus, obesity, and atherosclerotic cardiovascular risk) underlies the relatively earlier age of onset of cardiovascular diseases among African Americans. Hypertension in particular is highly prevalent among African Americans and contributes directly to the notable disparities in stroke, heart failure, and peripheral artery disease among African Americans. Despite the availability of effective pharmacotherapies and indications for some tailored pharmacotherapies for African Americans (eg, heart failure medications), disease management is less effective among African Americans, yielding higher mortality. Explanations for these persistent disparities in cardiovascular disease are multifactorial and span from the individual level to the social environment.

CONCLUSIONS

The strategies needed to promote equity in the cardiovascular health of African Americans require input from a broad set of stakeholders, including clinicians and researchers from across multiple disciplines.