A novel mechanism for hypofibrinolysis in diabetes: the role of complement C3

Fibrin Clot Properties in Cancer: Impact on Cancer-Associated Thrombosis

Cancer is associated with a high risk of venous thromboembolism (VTE) and its recurrence. There is evidence that the prothrombotic fibrin clot phenotype, involving the formation of denser and stiffer clots relatively resistant to lysis, occurs in cancer patients, which is in part related to enhanced inflammation, oxidative stress, and coagulation activation, along with the release of neutrophil extracellular traps, indicating that fibrin-related mechanisms might contribute to cancer-associated thrombosis (CAT). Multiple myeloma and its therapy have been most widely explored in terms of altered fibrin characteristics, but prothrombotic fibrin clot features have also been reported in patients with active solid cancer, including lung cancer and gastrointestinal cancer. Patient-related factors such as advanced age, smoking, and comorbidities might also affect fibrin clot characteristics and the risk of CAT. Prothrombotic fibrin clot features have been shown to predict the detection of cancer in patients following VTE during follow-up. Cancer-specific therapies and anticoagulation can favorably modify the phenotype of a fibrin clot, which may alter the course of CAT. It is unclear whether the fibrin clot phenotype might help identify patients with CAT who are more likely to experience recurrent events. This narrative review summarizes the current knowledge on the role of fibrin clot structure and function in cancer patients in the context of CAT.

Study on the Interaction Between C3 Gene Polymorphism and Environment in Patients with Type 2 Diabetes Combined with Coronary Artery Disease

Objective

This study was conducted to investigate the combined effect of genetic variation in the C3 gene and environmental factors on the risk of type 2 diabetes mellitus(T2DM) and coronary artery disease(CAD) in a population from Xinjiang, China.

Methods

We conducted a hospital-based case-control study with 896 participants (217 with T2DM+CAD and 679 healthy controls). A polymerase chain reaction-ligase detection reaction was used to identify and genotype TagSNPs in the C3 gene, and the influence of the interaction of two SNP loci (rs1047286 and rs11569562) with the environment on T2DM combined with CAD was evaluated through clinical data, statistical analysis of gene frequencies, and the formation of a gene-environment interaction model.

Results

We find that rs11569562 GG is an independent protective factor for T2DM and CAD (OR=0.353, p=0.012), and the variants at its locus may be closely associated with Activated Partial Thromboplastin Time (APTT), lipoprotein a (Lp(a)), Apolipoprotein A (APOA), Aspartate Aminotransferase (AST), Aspartate Aminotransferase (ALT) and AST/ALT levels (all P < 0.05); its GG genotype has significantly lower Gensini score and number of stenoses than the GA and AA genotypes. Multifactorial dimensionality reduction (MDR) finds a strong correlation between rs11569562 and AST (antagonistic effect) (4.44%); the role of rs11569562's influence remains strong in terms of the independent effects of each attribute (1.72%).

Conclusions

In this study, we find that variants in the C3 gene loci rs11569562 are associated with the incidence of type 2 diabetes mellitus combined with coronary heart disease in a Chinese population. It is expected to be an independent predictor of type 2 diabetes mellitus combined with coronary heart disease in the Chinese population. Rs11569562 may be associated with lipid levels and coagulation molecules.

Clinical Trial Registration

This trial registered on in 2014 at the China Clinical Trials Registry (ChiCTR-TRC-14005114).

Plasma levels of mannan-binding lectin-associated serine proteases are increased in type 1 diabetes patients with insulin resistance

Activation of the lectin pathway of the complement system, as demonstrated by elevated levels of mannan-binding lectin proteins (MBL), contributes to vascular pathology in type 1 diabetes (T1D). Vascular complications are greatest in T1D individuals with concomitant insulin resistance (IR), however, whether IR amplifies activiation of the lectin pathway in T1D is unknown. We pooled pretreatment data from two RCTs and performed a cross-sectional analysis on 46 T1D individuals. We employed estimated glucose disposal rate (eGDR), a validated IR surrogate with cut-points of: <5.1, 5.1-8.7, and > 8.7 mg/kg/min to determine IR status, with lower eGDR values conferring higher degrees of IR. Plasma levels of MBL-associated proteases (MASP-1, MASP-2, and MASP-3) and their regulatory protein MAp44 were compared among eGDR classifications. In a subset of 14 individuals, we assessed change in MASPs and MAp44 following improvement in IR. We found that MASP-1, MASP-2, MASP-3, and MAp44 levels increased in a stepwise fashion across eGDR thresholds with elevated MASPs and MAp44 levels conferring greater degrees of IR. In a subset of 14 patients, improvement in IR was associated with significant reductions in MASPs, but not MAp44, levels. In conclusion, IR in T1D amplifies levels of MASP-1/2/3 and their regulator MAp44, and improvement of IR normalizes MASP-1/2/3 levels. Given that elevated levels of these proteins contribute to vascular pathology, amplification of the lectin pathway of the complement system may offer mechanistic insight into the relationship between IR and vascular complications in T1D.

The Cellular and Protein Arms of Coagulation in Diabetes: Established and Potential Targets for the Reduction of Thrombotic Risk

Diabetes is a metabolic condition with a rising global prevalence and is characterised by abnormally high blood glucose levels. Cardiovascular disease (CVD) accounts for the majority of deaths in diabetes and, despite improvements in therapy, mortality and hospitalisations in this cohort remain disproportionally higher compared to individuals with normal glucose metabolism. One mechanism for increased CVD risk is enhanced thrombosis potential, due to altered function of the cellular and acellular arms of coagulation. Different mechanisms have been identified that mediate disordered blood clot formation and breakdown in diabetes, including dysglycaemia, insulin resistance, and metabolic co-morbidities. Collectively, these induce platelet/endothelial dysfunction and impair the fibrinolytic process, thus creating a prothrombotic milieu. Despite these abnormalities, current antithrombotic therapies are largely similar in diabetes compared to those without this condition, which explains the high proportion of patients experiencing treatment failure while also displaying an increased risk of bleeding events. In this narrative review, we aimed to summarise the physiological functioning of haemostasis followed by the pathological effects of diabetes mellitus on platelets and the fibrin network. Moreover, we carefully reviewed the literature to describe the current and future therapeutic targets to lower the thrombosis risk and improve vascular outcomes in diabetes.

Human complement component C3 N-glycome changes in type 1 diabetes complications

Aim

Changes in N-glycosylation have been described in numerous diseases and are being considered as biomarkers of ongoing pathological condition. Previous studies demonstrated the interrelation of N-glycosylation and type 1 diabetes (T1D), particularly linking serum N-glycan changes with complications accompanying the disease. Moreover, the role of complement component C3 in diabetic nephropathy and retinopathy has been implicated, and C3 N-glycome was found to be altered in young T1D patients. Therefore, we investigated associations between C3 N-glycan profiles and albuminuria and retinopathy accompanying T1D, as well as glycosylation connection with other known T1D complication risk factors.

Research design and methods

Complement component C3 N-glycosylation profiles have been analyzed from 189 serum samples of T1D patients (median age 46) recruited at a Croatian hospital centre. Using our recently developed high-throughput method, relative abundances of all six of the C3 glycopeptides have been determined. Assessment of C3 N-glycome interconnection with T1D complications, hypertension, smoking status, estimated glomerular filtration rate (eGFR), glycaemic control and duration of the disease was done using linear modelling.

Results

Significant changes of C3 N-glycome in severe albuminuria accompanying type 1 diabetes were observed, as well as in T1D subjects with hypertension. All except one of the C3 glycopeptides proved to be associated with measured HbA1c levels. One of the glycoforms was shown to be changed in non-proliferative T1D retinopathy. Smoking and eGFR showed no effect on C3 N-glycome. Furthermore, C3 N-glycosylation profile was shown to be independent of disease duration.

Conclusion

This study empowered the role of C3 N-glycosylation in T1D, showing value in distinguishing subjects with different diabetic complications. Being independent of the disease duration, these changes may be associated with the disease onset, making C3 N-glycome a potential novel marker of the disease progression and severity.

Fibrin clot properties in cardiovascular disease: from basic mechanisms to clinical practice

Fibrinogen conversion into insoluble fibrin and the formation of a stable clot is the final step of the coagulation cascade. Fibrin clot porosity and its susceptibility to plasmin-mediated lysis are the key fibrin measures, describing the properties of clots prepared ex vivo from citrated plasma. Cardiovascular disease (CVD), referring to coronary heart disease, heart failure, stroke, and hypertension, has been shown to be associated with the formation of dense fibrin networks that are relatively resistant to lysis. Denser fibrin mesh characterized acute patients at the onset of myocardial infarction or ischaemic stroke, while hypofibrinolysis has been identified as a persistent fibrin feature in patients following thrombotic events or in those with stable coronary artery disease. Traditional cardiovascular risk factors, such as smoking, diabetes mellitus, hyperlipidaemia, obesity, and hypertension, have also been linked with unfavourably altered fibrin clot properties, while some lifestyle modifications and pharmacological treatment, in particular statins and anticoagulants, may improve fibrin structure and function. Prospective studies have suggested that prothrombotic fibrin clot phenotype can predict cardiovascular events in short- and long-term follow-ups. Mutations and splice variants of the fibrinogen molecule that have been proved to be associated with thrombophilia or increased cardiovascular risk, along with fibrinogen post-translational modifications, prothrombotic state, inflammation, platelet activation, and neutrophil extracellular traps formation, contribute also to prothrombotic fibrin clot phenotype. Moreover, about 500 clot-bound proteins have been identified within plasma fibrin clots, including fibronectin, α2-antiplasmin, factor XIII, complement component C3, and histidine-rich glycoprotein. This review summarizes the current knowledge on the mechanisms underlying unfavourable fibrin clot properties and their implications in CVD and its thrombo-embolic manifestations.

The complement alternative pathway and hemostasis

The complement and hemostatic systems are complex systems, and both involve enzymatic cascades, regulators, and cell components-platelets, endothelial cells, and immune cells. The two systems are ancestrally related and are defense mechanisms that limit infection by pathogens and halt bleeding at the site of vascular injury. Recent research has uncovered multiple functional interactions between complement and hemostasis. On one side, there are proteins considered as complement factors that activate hemostasis, and on the other side, there are coagulation proteins that modulate complement. In addition, complement and coagulation and their regulatory proteins strongly interact each other to modulate endothelial, platelet and leukocyte function and phenotype, creating a potentially devastating amplifying system that must be closely regulated to avoid unwanted damage and\or disseminated thrombosis. In view of its ability to amplify all complement activity through the C3b-dependent amplification loop, the alternative pathway of complement may play a crucial role in this context. In this review, we will focus on available and emerging evidence on the role of the alternative pathway of complement in regulating hemostasis and vice-versa, and on how dysregulation of either system can lead to severe thromboinflammatory events.

Emerging opportunities for C3 inhibition in the eye

The eye presents a unique opportunity for complement component 3 (C3) therapeutics. Drugs can be delivered directly to specific parts of the eye, and growing evidence has established a pivotal role for C3 in age-related macular degeneration (AMD). Emerging data show that C3 may be important to the pathophysiology of other eye diseases as well. This article will discuss the location of C3 expression in the eye as well as the preclinical and clinical data regarding C3's functions in AMD. We will provide a comprehensive review of developing C3 inhibitors for the eye, including the Phase 2 and 3 data for the C3 inhibitor pegcetacoplan as a treatment for the geographic atrophy of AMD. Developing evidence also points toward C3 as a therapeutic target for stages of AMD preceding geographic atrophy. We will also discuss data illuminating C3's relationship to other eye diseases, such as Stargardt disease, diabetic retinopathy, and glaucoma. In addition to being a converging point and centerpiece of the complement cascade, C3 has broad effects as a multifaceted controller of opsonophagocytosis, microglia/macrophage recruitment, and downstream terminal pathway activity. C3 is a crucial player in the pathophysiology of AMD but also seems to have importance in other diseases that are major causes of blindness. Directions for further investigation will be highlighted, as culminating evidence suggests that we may be approaching an era of C3 therapeutics for the eye.

A randomised controlled trial to assess the antithrombotic effects of aspirin in type 1 diabetes: role of dosing and glycaemic control

Background

The enhanced thrombotic milieu in diabetes contributes to increased risk of vascular events. Aspirin, a key antiplatelet agent, has inconsistent effects on outcomes in diabetes and the best dosing regimen remains unclear. This work investigated effects of aspirin dose and interaction with glycaemia on both the cellular and protein components of thrombosis.

Methods

A total of 48 participants with type 1 diabetes and 48 healthy controls were randomised to receive aspirin 75 or 300 mg once-daily (OD) in an open-label crossover study. Light transmittance aggregometry and fibrin clot studies were performed before and at the end of each treatment period.

Results

Aspirin demonstrated reduced inhibition of collagen-induced platelet aggregation (PA) in participants with diabetes compared with controls, although the higher dose showed better efficacy. Higher aspirin dose facilitated clot lysis in controls but not individuals with diabetes. Collagen-induced PA correlated with glycaemic control, those in the top HbA1c tertile having a lesser inhibitory effect of aspirin. Threshold analysis suggested HbA1c levels of > 65 mmol/mol and > 70 mmol/mol were associated with poor aspirin response to 75 and 300 mg daily doses, respectively. Higher HbA1c was also associated with longer fibrin clot lysis time.

Conclusions

Patients with diabetes respond differently to the antiplatelet and profibrinolytic effects of aspirin compared with controls. In particular, those with elevated HbA1c have reduced inhibition of PA with aspirin. Our findings indicate that reducing glucose levels improves the anti-thrombotic action of aspirin in diabetes, which may have future clinical implications.

Trial registration

EudraCT, 2008-007875-26, https://www.clinicaltrialsregister.eu/ctr-search/search?query=2008-007875-26.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12933-021-01427-y.

Fibrinogen and Antifibrinolytic Proteins: Interactions and Future Therapeutics

Thrombus formation remains a major cause of morbidity and mortality worldwide. Current antiplatelet and anticoagulant therapies have been effective at reducing vascular events, but at the expense of increased bleeding risk. Targeting proteins that interact with fibrinogen and which are involved in hypofibrinolysis represents a more specific approach for the development of effective and safe therapeutic agents. The antifibrinolytic proteins alpha-2 antiplasmin (α2AP), thrombin activatable fibrinolysis inhibitor (TAFI), complement C3 and plasminogen activator inhibitor-2 (PAI-2), can be incorporated into the fibrin clot by FXIIIa and affect fibrinolysis by different mechanisms. Therefore, these antifibrinolytic proteins are attractive targets for the development of novel therapeutics, both for the modulation of thrombosis risk, but also for potentially improving clot instability in bleeding disorders. This review summarises the main properties of fibrinogen-bound antifibrinolytic proteins, their effect on clot lysis and association with thrombotic or bleeding conditions. The role of these proteins in therapeutic strategies targeting the fibrinolytic system for thrombotic diseases or bleeding disorders is also discussed.

Fibrinogen interaction with complement C3: a potential therapeutic target to reduce thrombosis risk

Complement C3 binds fibrinogen and compromises fibrin clot lysis, thereby enhancing the risk of thrombosis. We investigated the role of the fibrinogen-C3 interaction as a novel therapeutic target to reduce thrombosis risk by analyzing: (i) consistency in the fibrinolytic properties of C3; (ii) binding sites between fibrinogen and C3; and (iii) modulation of fibrin clot lysis by manipulating fibrinogen-C3 interactions. Purified fibrinogen and C3 from the same individuals (n=24) were used to assess inter-individual variability in the anti-fibrinolytic effects of C3. Microarray screening and molecular modeling evaluated C3 and fibrinogen interaction sites. Novel synthetic conformational proteins, termed affimers, were used to modulate the C3-fibrinogen interaction and fibrinolysis. C3 purified from patients with type 1 diabetes showed enhanced prolongation of fibrinolysis compared with healthy control protein (195±105 and 522±166 s, respectively; P=0.04), with consistent effects but a wider range (5-51% and 5-18% lysis prolongation, respectively). Peptide microarray screening identified two potential C3-fibrinogen interaction sites within the fibrinogen β chain (residues 424-433 and 435-445). One fibrinogen-binding affimer that was isolated displayed sequence identity with C3 in an exposed area of the protein. This affimer abolished C3- induced prolongation of fibrinolysis (728±25.1 s to 632±23.7 s; P=0.005) and showed binding to fibrinogen in the same region that is involved in C3-fibrinogen interactions. Moreover, it shortened plasma clot lysis of patients with diabetes, cardiovascular disease or controls by 7-11%. C3 binds fibrinogen -chain and disruption of the fibrinogen-C3 interaction using affimer proteins enhances fibrinolysis, which represents a potential novel tool to reduce thrombosis in high-risk individuals.

Fibrinolysis in Acute and Chronic Cardiovascular Disease

The formation of an obstructive thrombus within an artery remains a major cause of mortality and morbidity worldwide. Despite effective inhibition of platelet function by modern antiplatelet therapies, these agents fail to fully eliminate atherothrombotic risk. This may well be related to extensive vascular disease, beyond the protective abilities of the treatment agents used. However, recent evidence suggests that residual vascular risk in those treated with modern antiplatelet therapies is related, at least in part, to impaired fibrin clot lysis. In this review, we attempt to shed more light on the role of hypofibrinolysis in predisposition to arterial vascular events. We provide a brief overview of the coagulation system followed by addressing the role of impaired fibrin clot lysis in acute and chronic vascular conditions, including coronary artery, cerebrovascular, and peripheral vascular disease. We also discuss the role of combined anticoagulant and antiplatelet therapies to reduce the risk of arterial thrombotic events, addressing both efficacy and safety of such an approach. We conclude that impaired fibrin clot lysis appears to contribute to residual thrombosis risk in individuals with arterial disease on antiplatelet therapy, and targeting proteins in the fibrinolytic system represents a viable strategy to improve outcome in this population. Future work is required to refine the antithrombotic approach by modulating pathological abnormalities in the fibrinolytic system and tailoring therapy according to the need of each individual.

PAI-1 in Diabetes: Pathophysiology and Role as a Therapeutic Target

Hypofibrinolysis is a key abnormality in diabetes and contributes to the adverse vascular outcome in this population. Plasminogen activator inhibitor (PAI)-1 is an important regulator of the fibrinolytic process and levels of this antifibrinolytic protein are elevated in diabetes and insulin resistant states. This review describes both the physiological and pathological role of PAI-1 in health and disease, focusing on the mechanism of action as well as protein abnormalities in vascular disease with special focus on diabetes. Attempts at inhibiting protein function, using different techniques, are also discussed including direct and indirect interference with production as well as inhibition of protein function. Developing PAI-1 inhibitors represents an alternative approach to managing hypofibrinolysis by targeting the pathological abnormality rather than current practice that relies on profound inhibition of the cellular and/or acellular arms of coagulation, and which can be associated with increased bleeding events. The review offers up-to-date knowledge on the mechanisms of action of PAI-1 together with the role of altering protein function to improve hypofirbinolysis. Developing PAI-1 inhibitors may form for the basis of future new class of antithrombotic agents that reduce vascular complications in diabetes.

Coagulation and Fibrinolysis in Obstructive Sleep Apnoea

Obstructive sleep apnoea (OSA) is a common disease which is characterised by repetitive collapse of the upper airways during sleep resulting in chronic intermittent hypoxaemia and frequent microarousals, consequently leading to sympathetic overflow, enhanced oxidative stress, systemic inflammation, and metabolic disturbances. OSA is associated with increased risk for cardiovascular morbidity and mortality, and accelerated coagulation, platelet activation, and impaired fibrinolysis serve the link between OSA and cardiovascular disease. In this article we briefly describe physiological coagulation and fibrinolysis focusing on processes which could be altered in OSA. Then, we discuss how OSA-associated disturbances, such as hypoxaemia, sympathetic system activation, and systemic inflammation, affect these processes. Finally, we critically review the literature on OSA-related changes in markers of coagulation and fibrinolysis, discuss potential reasons for discrepancies, and comment on the clinical implications and future research needs.

Albumin-mediated alteration of plasma zinc speciation by fatty acids modulates blood clotting in type-2 diabetes

Zn²⁺ is an essential regulator of coagulation and is released from activated platelets. In plasma, the free Zn²⁺ concentration is fine-tuned through buffering by human serum albumin (HSA). Importantly, the ability of HSA to bind/buffer Zn²⁺ is compromised by co-transported non-esterified fatty acids (NEFAs). Given the role of Zn²⁺ in blood clot formation, we hypothesise that Zn²⁺ displacement from HSA by NEFAs in certain conditions (such as type 2 diabetes mellitus, T2DM) impacts on the cellular and protein arms of coagulation. To test this hypothesis, we assessed the extent to which increasing concentrations of a range of medium- and long-chain NEFAs reduced Zn²⁺-binding ability of HSA. Amongst the NEFAs tested, palmitate (16 : 0) and stearate (18 : 0) were the most effective at suppressing zinc-binding, whilst the mono-unsaturated palmitoleate (16 : 1c9) was markedly less effective. Assessment of platelet aggregation and fibrin clotting parameters in purified systems and in pooled plasma suggested that the HSA-mediated impact of the model NEFA myristate on zinc speciation intensified the effects of Zn²⁺ alone. The effects of elevated Zn²⁺ alone on fibrin clot density and fibre thickness in a purified protein system were mirrored in samples from T2DM patients, who have derranged NEFA metabolism. Crucially, T2DM individuals had increased total plasma NEFAs compared to controls, with the concentrations of key saturated (myristate, palmitate, stearate) and mono-unsaturated (oleate, cis-vaccenate) NEFAs positively correlating with clot density. Collectively, these data strongly support the concept that elevated NEFA levels contribute to altered coagulation in T2DM through dysregulation of plasma zinc speciation.

Zn²⁺ is an essential regulator of coagulation. In plasma, Zn²⁺ availability is fine-tuned by human serum albumin (HSA). Here we show that elevated fatty acid levels contribute to altered coagulation in type-2 diabetes through Zn²⁺ mishandling by HSA.

Valproic acid influences the expression of genes implicated with hyperglycaemia-induced complement and coagulation pathways

Because the liver plays a major role in metabolic homeostasis and secretion of clotting factors and inflammatory innate immune proteins, there is interest in understanding the mechanisms of hepatic cell activation under hyperglycaemia and whether this can be attenuated pharmacologically. We have previously shown that hyperglycaemia stimulates major changes in chromatin organization and metabolism in hepatocytes, and that the histone deacetylase inhibitor valproic acid (VPA) is able to reverse some of these metabolic changes. In this study, we have used RNA-sequencing (RNA-seq) to investigate how VPA influences gene expression in hepatocytes. Interesting, we observed that VPA attenuates hyperglycaemia-induced activation of complement and coagulation cascade genes. We also observe that many of the gene activation events coincide with changes to histone acetylation at the promoter of these genes indicating that epigenetic regulation is involved in VPA action.

Maturity onset diabetes of the young and fibrin-related thrombosis risk

BACKGROUND

Fibrin network characteristics determine predisposition to cardiovascular disease (CVD). Individuals with type 1 (T1DM) and type 2 diabetes mellitus (T2DM) have higher risk of CVD and display deranged fibrin network structure. Those with maturity onset diabetes of the young (MODY) may also be at increased risk but their fibrin clot properties have not been studied.

METHODS

Plasma clots properties from 13 individuals with HNF1A-MODY, 12 matched-individuals with T2DM and 12 with T1DM were studied using a validated turbidimetric assay and confocal microscopy. Plasma levels of fibrinogen, plasminogen activator inhibitor-1, complement C3 and C-reactive protein were also measured.

RESULTS

MODY clot maximum absorbance was 0.37 ± 0.03 AU, similar to T1DM (0.32 ± 0.03 AU; p = 0.26), but lower than T2DM (0.49 ± 0.03 AU; p = 0.02), with confocal microscopy confirming structural differences. Clot lysis time in MODY was similar to T1DM (456 ± 50 and 402 ± 20 s, respectively; p = 0.09) but shorter than T2DM (588 ± 58 s; p = 0.006). Comparing inflammatory/thrombotic proteins in HNF1A-MODY and T2DM, C3 levels were lower in MODY than T2DM (0.58 ± 0.09 and 0.80 ± 0.1 mg/ml, respectively; p < 0.01).

CONCLUSIONS

HNF1A-MODY fibrin network alterations are at least as pronounced as in T1DM but less thrombotic than T2DM clots. Differences in fibrin clot characteristics comparing HNF1A-MODY and T2DM may, in part, relate to lower C3 levels.

Determinants of plasma fibrin clot lysis measured using three different assays in healthy subjects

INTRODUCTION

Several methods for measuring fibrinolytic capacity in plasma have been developed yielding frequently inconsistent results. We investigated which factors determine fibrinolytic capacity in three plasma-based assays.

MATERIAL AND METHODS

In 80 apparently healthy controls (aged 43 ± 10 years, 50 women [62.5%]) we evaluated fibrinolysis using three assays: (1) by Pieters et al. (CLT2018), (2) by Lisman et al. (CLT), and (3) by Carter et al. (Lys50). Coagulation factors and fibrinolytic proteins, including histidine-rich glycoprotein (HRG) and γ'-fibrinogen, were determined. Regression models were performed to identify determinants of lysis times.

RESULTS

Positive correlations were observed between CLT2018 and both CLT (r = 0.73) and Lys50 (r = 0.61), as well as between CLT and Lys50 (r = 0.46, all p < 0.001). The main determinants of both CLT2018 and CLT were plasminogen activator inhibitor-1 (PAI-1), followed by thrombin-activatable fibrinolysis inhibitor (TAFI) and α₂-antiplasmin. Histidine-rich glycoprotein was a predictor of the longest-normal CLT2018 alone (OR 1.04, 95% CI 1.02-1.06). α₂-Antiplasmin and fibrinogen levels, followed by PAI-1 and TAFI determined Lys50. After adjustment for age, sex, and body mass index, C-reactive protein (CRP) was an independent predictor of the top quartiles of the three lysis times.

CONCLUSIONS

We showed that apart from PAI-1, TAFI, and α₂-antiplasmin, several other factors, in particular CRP, can affect the results of global fibrinolysis tests used in research. Our findings may help understand why the choice of a specific fibrinolysis assay can affect the presence and/or magnitude of intergroup differences in fibrinolytic capacity in a given disease state.

Diabetes and atherothrombosis: The circadian rhythm and role of melatonin in vascular protection

Obesity-related euglycaemic insulin resistance clusters with cardiometabolic risk factors, contributing to the development of both type 2 diabetes and cardiovascular disease. An increased thrombotic tendency in diabetes stems from platelet hyperactivity, enhanced activity of prothrombotic coagulation factors and impaired fibrinolysis. Furthermore, a low-grade inflammatory response and increased oxidative stress accelerate the atherosclerotic process and, together with an enhanced thrombotic environment, result in premature and more severe cardiovascular disease. The disruption of circadian cycles in man secondary to chronic obesity and loss of circadian cues is implicated in the increased risk of developing diabetes and cardiovascular disease. Levels of melatonin, the endogenous synchronizer of circadian rhythm, are reduced in individuals with vascular disease and those with deranged glucose metabolism. The anti-inflammatory, antihypertensive, antioxidative and antithrombotic activities of melatonin make it a potential therapeutic agent to reduce the risk of vascular occlusive disease in diabetes. The mechanisms behind melatonin-associated reduction in procoagulant response are not fully known. Current evidence suggests that melatonin inhibits platelet aggregation and might affect the coagulation cascade, altering fibrin clot structure and/or resistance to fibrinolysis. Large-scale clinical trials are warranted to investigate the effects of modulating the circadian clock on insulin resistance, glycaemia and cardiovascular outcome.

Reduced Plasma Magnesium Levels in Type-1 Diabetes Associate with Prothrombotic Changes in Fibrin Clotting and Fibrinolysis

Individuals with type-1 diabetes mellitus (T1DM) have a higher risk of thrombosis and low plasma magnesium concentrations. As magnesium is a known regulator of fibrin network formation, we investigated potential associations between fibrin clot properties and plasma magnesium concentrations in 45 individuals with T1DM and 47 age- and sex-matched controls without diabetes. Fibrin clot characteristics were assessed using a validated turbidimetric assay and associations with plasma magnesium concentration were examined. Plasma concentrations of fibrinogen, plasminogen activator inhibitor-1 (PAI-1), and lipids were measured and fibrin fiber diameters assessed using scanning electron microscopy. Fibrin clot maximum absorbance was unchanged in subjects with T1DM compared with controls, while lysis time was prolonged (p = 0.0273). No differences in fibrin fiber diameters or in lipid profile were observed between T1DM and controls. PAI-1 concentration was lower in the T1DM group compared with the controls (p = 0.0232) and positively correlated with lysis time (p = 0.0023). Plasma magnesium concentration was lower in the T1DM group compared with controls (p < 0.0001). Magnesium concentration negatively correlated with clot maximum absorbance (p = 0.0215) and lysis time (p = 0.0464). A turbidimetric fibrin clot lysis assay performed in a purified system that included PAI-1 and 0 to 3.2 mM Mg2+ showed a shortening of lysis time with increasing Mg2+ concentrations (p = 0.0004). Our findings reveal that plasma magnesium concentration is associated with changes in fibrin clot and lysis parameters.

Impaired Fibrinolysis Predicts Adverse Outcome in Acute Coronary Syndrome Patients with Diabetes: A PLATO Sub-Study

Hypofibrinolysis is a key abnormality in diabetes but the role of impaired clot lysis in predicting vascular events and mortality in this population is yet to be determined. We aimed to investigate the relationship between fibrin clot properties and clinical outcomes in patients with diabetes and recent acute coronary syndrome (ACS). Plasma samples were collected at hospital discharge from 974 ACS patients with diabetes randomised to clopidogrel or ticagrelor in the PLATO trial. A validated turbidimetric assay was employed to study fibrin clot lysis and maximum turbidity. One-year rates of cardiovascular (CV) death, spontaneous myocardial infarction (MI) and PLATO-defined major bleeding events were assessed after sample collection. Hazard ratios (HRs) were determined using Cox proportional analysis. After adjusting for CV risk factors, each 50% increase in lysis time was associated with increased risk of CV death/MI (HR 1.21; 95% confidence interval [CI] 1.02–1.44; p  = 0.026) and CV death alone (HR 1.38; 1.08–1.76; p  = 0.01). Similarly, each 50% increase in maximum turbidity was associated with increased risk of CV death/MI (HR 1.25; 1.02–1.53; p  = 0.031) and CV death alone (HR 1.49; 1.08–2.04; p  = 0.014). The relationship between lysis time and the combined outcome of CV death and MI remained significant after adjusting for multiple prognostic vascular biomarkers ( p  = 0.034). Neither lysis time nor maximum turbidity was associated with major bleeding events. Impaired fibrin clot lysis predicts 1-year CV death and MI in diabetes patients following ACS.

Clinical Trial Registration  URL: http://www.clinicaltrials.gov . Unique identifier NCT00391872.

Complement activation in obesity, insulin resistance, and type 2 diabetes mellitus

Amplified inflammatory reaction has been observed to be involved in cardiometabolic diseases such as obesity, insulin resistance, diabetes, dyslipidemia, and atherosclerosis. The complement system was originally viewed as a supportive first line of defense against microbial invaders, and research over the past decade has come to appreciate that the functions of the complement system extend beyond the defense and elimination of microbes, involving in such diverse processes as clearance of the immune complexes, complementing T and B cell immune functions, tissue regeneration, and metabolism. The focus of this review is to summarize the role of the activation of complement system and the initiation and progression of metabolic disorders including obesity, insulin resistance and diabetes mellitus. In addition, we briefly describe the interaction of the activation of the complement system with diabetic complications such as diabetic retinopathy, nephropathy and neuropathy, highlighting that targeting complement system therapeutics could be one of possible routes to slow down those aforementioned diabetic complications.

Type 1 diabetes is associated with an increased risk of venous thromboembolism: A retrospective population-based cohort study

Background

It has been unclear whether diabetes mellitus (DM) is positively associated with a risk of venous thromboembolism (VTE). In addition, whether the risk of VTE is altered in patients with type 1 diabetes (T1DM) has rarely been explored.

Aim

We investigated whether patients with T1DM are at a relatively high risk of VTE development.

Methods

We retrieved data from the National Health Insurance Research Database of Taiwan to conduct this retrospective cohort study. The T1DM group consisted of 4967 patients diagnosed as having T1DM before 2003. The non-T1DM group comprised 19 868 age- and sex-matched enrollees without T1DM. Cox proportional hazard regression analysis was used to investigate the hazard ratio of VTE in patients with T1DM relative to those without T1DM.

Results

During a mean follow-up period of 8.61 years, the risk of VTE in the T1DM group was 5.33-fold higher than in the non-T1DM group after adjusting for dyslipidemia, hypertension, stroke, lower leg fracture or surgery, and obesity. Further stratified analysis revealed that the risk of VTE was significantly high in both sexes and in all age groups below the age of 60.

Conclusion

T1DM appears to be an independent risk factor for VTE development.

Diabetes affects endothelial cell function and alters fibrin clot formation in a microvascular flow model: A pilot study

Diabetes is a proinflammatory and prothrombotic condition that increases the risk of vascular complications. The aim of this study was to develop a diabetic microvascular flow model that allows to study the complex interactions between endothelial cells, blood cells and plasma proteins and their effects on clot formation. Primary human cardiac microvascular endothelial cells from donors without diabetes or donors with diabetes (type 1 or type 2) were grown in a microfluidic chip, perfused with non-diabetic or diabetic whole blood, and clot formation was assessed by measuring fibrin deposition in real time by confocal microscopy. Clot formation in non-diabetic whole blood was significantly increased in the presence of endothelial cells from donors with type 2 diabetes compared with cells from donors without diabetes. There was no significant difference in clot formation between non-diabetic and diabetic whole blood. We present for the first time a diabetic microvascular flow model as a new tool to study clot formation as a result of the complex interactions between endothelial cells, blood cells and plasma proteins in a diabetes setting. We show that endothelial cells affect clot formation in whole blood, attributing an important role to the endothelium in the development of atherothrombotic complications.

Coagulatory Defects in Type-1 and Type-2 Diabetes

Diabetes (both type-1 and type-2) affects millions of individuals worldwide. A major cause of death for individuals with diabetes is cardiovascular diseases, in part since both types of diabetes lead to physiological changes that affect haemostasis. Those changes include altered concentrations of coagulatory proteins, hyper-activation of platelets, changes in metal ion homeostasis, alterations in lipid metabolism (leading to lipotoxicity in the heart and atherosclerosis), the presence of pro-coagulatory microparticles and endothelial dysfunction. In this review, we explore the different mechanisms by which diabetes leads to an increased risk of developing coagulatory disorders and how this differs between type-1 and type-2 diabetes.

Double diabetes: A distinct high-risk group?

The term double diabetes (DD) has been used to refer to individuals with type 1 diabetes (T1D) who are overweight, have a family history of type 2 diabetes and/or clinical features of insulin resistance. Several pieces of evidence indicate that individuals who display features of DD are at higher risk of developing future diabetes complications, independently of average glucose control, measured as glycated haemoglobin (HbA1c) concentration. Given the increased prevalence of individuals with features of DD, pragmatic criteria are urgently required to identify and stratify this group, which will help with subsequent implementation of more effective personalized interventions. In this review, we discuss the potential criteria for the clinical identification of individuals with DD, highlighting the strengths and weaknesses of each definition. We also cover potential mechanisms of DD and how these contribute to increased risk of diabetes complications. Special emphasis is placed on the role of estimated glucose disposal rate (eGDR) in the diagnosis of DD, which can be easily incorporated into clinical practice and is predictive of adverse clinical outcome. In addition to the identification of individuals with DD, eGDR has potential utility in monitoring response to different interventions. T1D is a more heterogeneous condition than initially envisaged, and those with features of DD represent a subgroup at higher risk of complications. Pragmatic criteria for the diagnosis of individuals with DD will help with risk stratification, allowing a more personalized and targeted management strategy to improve outcome and quality of life in this population.

Role of complement in diabetes

Accumulating evidence suggests a role for the complement system in the pathogenesis of diabetes and the vascular complications that characterise this condition. Complement proteins contribute to the development of type 1 diabetes (T1D) by enhancing the underlying organ-specific autoimmune processes. Complement upregulation and activation is also an important feature of insulin resistance and the development of type 2 diabetes (T2D). Moreover, animal and human studies indicate that complement proteins are involved in the pathogenic mechanisms leading to diabetic microvascular and macrovascular complications. The adverse vascular effects of complement appear to be related to enhancement of the inflammatory process and the predisposition to a thrombotic environment, eventually leading to vascular occlusion. Complement proteins have been considered as therapeutic targets to prevent or treat vascular disease but studies have been mainly conducted in animal models, while human work has been both limited and inconclusive so far. Further studies are needed to understand the potential role of complement proteins as therapeutic targets for reversal of the pathological processes leading to T1D and T2D and for the prevention/treatment of diabetic vascular complications.

MASP-1 of the complement system alters fibrinolytic behaviour of blood clots

BACKGROUND

The lectin pathway serine protease mannan-binding lectin-associated serine protease 1 (MASP-1) has been demonstrated to be a major link between complement and coagulation, yet little is known about its interactions with the fibrinolytic system. The aim of this work was to assess the effects of MASP-1 on fibrin clot lysis in different experimental settings.

METHODS

Rotational thrombelastometry was used to evaluate the effect of MASP-1 on the lysis of clots formed in whole blood under static conditions. Whole blood clots were also formed in the presence and absence of MASP-1 under flow conditions in the Chandler loop and their lysis was analysed separately by fluorescence release of incorporated labelled fibrin. Real-time observation by laser scanning confocal microscopy was used to investigate the lysis of plasma clots where MASP-1 was present either during clot formation or lysis. Cleavage of tPA or plasminogen by MASP-1 was analysed by gel electrophoresis. We performed a turbidimetric clot lysis assay in the presence and absence of the MASP-1 inhibitor SGMI-1 (Schistocerca gregaria protease inhibitor (SGPI)-based MASP inhibitor-1) to evaluate the effect of endogenous MASP-1 in normal plasma and plasma samples from sepsis patients.

RESULTS

In the thrombelastometric experiments, where MASP-1 was present during the entire clotting and lysis process, MASP-1 had a significant profibrinolytic effect and accelerated clot lysis. When clots were formed in the presence of MASP-1 under flow in the Chandler loop, the effects on fibrinolysis were heterogenous with impaired fibrinolysis in some individuals (n = 5) and no (n = 3) or even the opposite effect (n = 2) in others. In plasma clot lysis observed by confocal microscopy, lysis was prolonged when MASP-1 was added to the lysis solution, yet there was no difference in lysis time when MASP-1 was present during clot formation. When MASP-1 was incubated with tPA or plasminogen, respectively, cleavage of single-chain tPA into two-chain tPA and a slight reduction of plasminogen were observed. SGMI-1 significantly prolonged clot lysis in the turbidimetric clot lysis assay suggesting that MASP-1 accelerated lysis in plasma samples.

CONCLUSION

MASP-1 is able to alter the susceptibility of blood clots to the fibrinolytic system. MASP-1 has complex, mostly promoting effects on fibrinolysis with high inter-individual variation. Interactions of MASP-1 with the fibrinolytic system may be relevant in the development and therapy of cardiovascular and thrombotic diseases.

Decreased Ficolin-3-mediated Complement Lectin Pathway Activation and Alternative Pathway Amplification During Bacterial Infections in Patients With Type 2 Diabetes Mellitus

Bacterial infections are frequent and severe in patients with diabetes mellitus. Whether diabetes per se induces functional alterations in the complement system hampering activation during infection is unknown. We investigated key elements of the complement system during bacterial infections in patients with type 2 diabetes mellitus (T2DM) and compared them to non-diabetic (ND) individuals. Using a prospective design, we included 197 T2DM, and 196 ND subjects, all with clinical diagnosis of acute community-acquired bacterial infections. Functional activities of the ficolin-3-mediated lectin (F3-LP), mannose binding lectin-mediated lectin- (MBL-LP), classical (CP), and alternative pathways (AP), as well as concentrations of complement activation products C4d and sC5b-9 were determined. Functional in vitro activities of F3-LP and AP were significantly higher in T2DM than in ND subjects, (median 64% vs. 45%, p = 0.0354 and 75 vs. 28%, p = 0.0013, respectively), indicating a decreased in vivo activation and lack of consumption of F3-LP and AP in T2DM patients, whereas no difference in functional capacities of CP and MBL-LP were observed between T2DM and ND subjects. Diminished F3-LP and AP activation was most pronounced in diabetic patients with urinary tract infections with positive microbiological culture results for Escherichia coli bacteria. In the T2DM group 3-months mortality significantly associated with diminished F3-LP and AP, but not with CP activation. Concentrations of C4d and sC5b-9 were significantly lower in the T2DM than in ND patients. In conclusion, we found impaired F3-LP activation and lack of AP amplification during bacterial infections in patients with type 2 diabetes, compared to non-diabetic subjects, suggesting a diminished complement mediated protection to bacterial infections in T2DM.

Prolonged Prothrombotic Effects of Antecedent Hypoglycemia in Individuals With Type 2 Diabetes

OBJECTIVE

Hypoglycemia has been linked to persistent increases in cardiovascular (CV) mortality in type 2 diabetes after the event. Our aim was to examine acute and downstream effects of hypoglycemia on markers of thrombosis risk and inflammation in type 2 diabetes.

RESEARCH DESIGN AND METHODS

Twelve individuals with type 2 diabetes with no history of CV disease and 11 age- and BMI-matched volunteers without diabetes underwent paired hyperinsulinemic-euglycemic (glucose 6 mmol/L for two 60-min periods) and hypoglycemic (glucose 2.5 mmol/L for two 60-min periods) clamps on separate occasions on day 0. Fibrin clot properties, platelet reactivity, and inflammatory markers were measured at baseline, end of and after recovery from the initial clamp, day 1, and day 7 using validated assays and electron microscopy.

RESULTS

Euglycemic hyperinsulinemia reduced platelet reactivity, decreased fibrin clot density, and improved fibrinolytic efficiency in both groups. Platelet reactivity and aggregation increased during acute hypoglycemia in both groups, resolving at recovery. In type 2 diabetes, clot lysis times and clot maximum absorbance increased up to day 7 (P = 0.002 and 0.001 vs. euglycemia, respectively), but clots from control subjects without diabetes showed limited changes. Fibrin network density increased Δ 1.15 ± 0.28 fibers/μm² at day 7 after the hypoglycemic clamp (P < 0.01 for glycemic arm), whereas fibrinogen and complement C3 increased after hypoglycemia up to day 7 in type 2 diabetes only.

CONCLUSIONS

Antecedent hypoglycemia has acute and persistent prothrombotic effects, lasting at least 7 days, that were enhanced in individuals with type 2 diabetes. These findings identify mechanisms by which hypoglycemia might increase short- and medium-term risk of CV mortality.

Complement-coagulation connections

: Complement and coagulation are evolutionarily related proteolytic cascades in the blood that are critical for effecting an appropriate innate response to injury that limits bleeding and infection, while promoting healing. Although often viewed as distinct, it has long been recognized that cross-talk likely exists between these pathways. Only recently have molecular links been established. These are providing insights that are revealing opportunities for the development of novel therapeutic strategies to better treat a wide range of thrombotic, inflammatory, immune, infectious, and malignant diseases. In this brief review, the complex relationship between complement and coagulation is highlighted, underlining some of the newly uncovered interactions, in the hopes of stimulating innovative research that will yield improvements in patient outcomes.

Complement C3 and Risk of Diabetic Microvascular Disease: A Cohort Study of 95202 Individuals from the General Population

BACKGROUND

Whether the complement system is involved in the development of diabetic microvascular disease is unknown. We tested the hypothesis that high concentrations of complement C3 are associated with increased risk of diabetic retinopathy, nephropathy, and neuropathy in individuals from the general population.

METHODS

We studied 95202 individuals from the general population with baseline measurements of complement C3, genotyped for rs1065489, rs429608, and rs448260 determining concentrations of complement C3, and enrolled in the Copenhagen General Population Study from 2003 through 2013, following them until April 10, 2013. Rs1065489, rs429608, and rs448260 were identified with genome-wide association scans in 3752 individuals from the Copenhagen City Heart Study.

RESULTS

The cumulative incidence was increased from the lowest tertile to the highest tertile of complement C3 for diabetic retinopathy (log-rank trend, P = 1 × 10^-20), nephropathy (P = 7 × 10^-15), and neuropathy (P = 5 × 10^-10). Multifactorially adjusted hazard ratios for a 1 SD higher concentration of complement C3 were 1.87 (95% CI, 1.61-2.18) for diabetic retinopathy, 1.90 (1.62-2.23) for diabetic nephropathy, and 1.56 (1.29-1.89) for diabetic neuropathy. The multifactorially adjusted hazard ratio for individuals with the highest vs lowest tertile of complement C3 was 3.29 (1.78-6.07) for retinopathy, 2.71 (1.42-5.16) for nephropathy, and 2.40 (1.26-4.54) for neuropathy.

CONCLUSIONS

High baseline concentrations of complement C3 were associated with increased risk of diabetic retinopathy, nephropathy, and neuropathy in individuals from the general population. These epidemiological findings were substantiated by a Mendelian randomization approach, potentially indicating causality.

A model to study complement involvement in experimental retinal degeneration

BACKGROUND

The complement system (CS) plays a role in the pathogenesis of a number of ocular diseases, including diabetic retinopathy (DR), glaucoma, uveitis, and age-related macular degeneration (AMD). Given that many of the complex eye-related degenerative diseases have limited treatment opportunities, we aimed to mimic the in vivo retinal degenerative process by developing a relevant co-culture system.

METHOD AND MATERIALS

The adult porcine retina was co-cultured with the spontaneously arising human retinal pigment epithelial cells-19 (ARPE-19).

RESULTS

Inflammatory activity was found after culture and included migrating microglial cells, gliosis, cell death, and CS activation (demonstrated by a minor increase in the secreted anaphylotoxin C3a in co-culture). CS components, including C1q, C3, C4, soluble C5b-9, and the C5a receptor, were expressed in the retina and/or ARPE cells after culture. C1q, C3, and CS regulators such as C4 binding protein (C4BP), factor H (CFH), and factor I (CFI) were secreted after culture.

DISCUSSION

Thus, our research indicates that this co-culturing system may be useful for investigations of the CS and its involvement in experimental neurodegenerative diseases.

Simultaneous presence of hypercoagulation and increased clot lysis time due to IL-1β, IL-6 and IL-8

Circulating cytokines, and particularly the interleukin (IL)-family are known to play an important role in inflammation. These molecules circulate in the blood and therefore have a direct effect on the plasma molecules and the formed elements like the erythrocytes and platelets. Aberrant coagulation (hypercoagulation or blood clots that form too easily) and clot lyses (hypofibrinolysis, where clots do not dissolve properly, with an abnormally low rate of clot lysis time), are usually the hallmarks of many inflammatory conditions. However, the mechanism by which cross-linking augments clot stiffness remains undetermined. IL-1β; IL-6 and IL-8 has been found to be involved in most chronic and acute inflammatory diseases. In the present study, we investigate clot structure of healthy blood, with the addition of these 3 interleukins, to determine the individual effects at concentrations that mimic low-grade, chronic inflammation. Previous studies showed that clot rheological behavior is regulated by at least the following three factors, fibrinogen concentration, fibrin network architecture and FXIIIa-induced ligation. We investigated clot formation and lysis using thromboelastography (TEG), before and after exposure, and created clots by adding thrombin to whole blood. This allowed us to look at extensive fibrin fiber formation and their interactions with particularly the erythrocytes, using scanning electron microscopy (SEM). Our results showed that IL-1β; IL-6 and IL-8 causes hypercoagulation and results in a disheveled fibrin clot, with trapped RBCs. IL-8 showed eryptosis (a type of apoptosis in erythrocytes). Our lysis results showed that both clot lysis time and maximum rate of lysis are decreased, with the addition of the interleukins. This is a novel finding and the observations reported in this paper, therefore points to the importance of looking at the effects of individual circulating inflammagens, to better understand the role that each play in the expression of disease. These methods can be used for an individualized patient-orientated approach in healthcare to track blood viscosity in conditions with acute and chronic inflammation.

Viscoelasticity as a measurement of clot structure in poorly controlled type 2 diabetes patients: towards a precision and personalized medicine approach

Objectives

Type 2 diabetes patients (T2D) have a considerably higher cardiovascularrisk, which is closely associated with systemic inflammation, and an accompanying pathologic coagulation system. Due to the complexity of the diabetic profile, we suggest that we need to look at each patient individually and particularly at his or her clotting profile; as the healthiness of the coagulation system gives us an indication of the success of clinical intervention.

Results

T2D coagulability varied markedly, although there were no clear difference in medication use and the standards of HbA1c levels.

Research design and methods

Our sample consisted of 90 poorly controlled T2D and 71 healthy individuals. We investigated the medication use and standards of HbA1c levels of T2D and we used thromboelastography (TEG) and scanning electron microscopy (SEM) to study their clot formation.

Conclusion

The latest NIH guidelines suggest that clinical medicine should focus on precision medicine, and the current broad understanding is that precision medicine may in future, provide personalized targets for preventative and therapeutic interventions. Here we suggest a practical example where TEG can be used as an easily accessible point-of-care tool to establish a comprehensive clotting profile analysis for T2D patients; and additionally may provide valuable information that may be used in the envisaged precision medicine approach. Only by closely following each individual patient's progress and healthiness and thereby managing systemic inflammation, will we be able to reduce this pandemic.

Thrombosis and Vascular Inflammation in Diabetes: Mechanisms and Potential Therapeutic Targets

Cardiovascular disease remains the main cause of morbidity and mortality in patients with diabetes. The risk of vascular ischemia is increased in this population and outcome following an event is inferior compared to individuals with normal glucose metabolism. The reasons for the adverse vascular profile in diabetes are related to a combination of more extensive atherosclerotic disease coupled with an enhanced thrombotic environment. Long-term measures to halt the accelerated atherosclerotic process in diabetes have only partially addressed vascular pathology, while long-term antithrombotic management remains largely similar to individuals without diabetes. We address in this review the pathophysiological mechanisms responsible for atherosclerosis with special emphasis on diabetes-related pathways. We also cover the enhanced thrombotic milieu, characterized by increased platelet activation, raised activity of procoagulant proteins together with compromised function of the fibrinolytic system. Potential new therapeutic targets to reduce the risk of atherothrombosis in diabetes are explored, including alternative use of existing therapies. Special emphasis is placed on diabetes-specific therapeutic targets that have the potential to reduce vascular risk while keeping an acceptable clinical side effect profile. It is now generally acknowledged that diabetes is not a single clinical entity but a continuum of various stages of the condition with each having a different vascular risk. Therefore, we propose that future therapies aiming to reduce vascular risk in diabetes require a stratified approach with each group having a "stage-specific" vascular management strategy. This "individualized care" in diabetes may prove to be essential to improve vascular outcome in this high risk population.

Increased Levels of Serum Protein Complexes Are Associated with Type 2 Diabetes

Objective: To screen novel biomarkers in the levels of protein complexes for type 2 diabetes mellitus (T2DM). Methods: Serum immunoinflammation-related protein complexes (IIRPCs) and diabetes-related protein complexes (DRPCs) in 1537 serum samples including 504 healthy controls, 320 patients with prediabetes, and 713 patients with T2DM were analyzed using an optimized native polyacrylamide gel electrophoresis (native-PAGE). Results: Seven patterns of serum IIRPCs and four patterns of serum DRPCs were observed in the study population, respectively. Significant increase in the levels of serum IIRPCs in T2DM was detected relative to healthy controls. Change trends of serum DRPCs are as below: patients with T2DM>patients with prediabetes> healthy controls. Conclusion: Our findings suggest that increased levels of serum IIRPCs and DRPCs were associated with T2DM.

BβArg448Lys polymorphism is associated with altered fibrin clot structure and fibrinolysis in type 2 diabetes

Both type 2 diabetes (T2DM) and Bß448Lys variant of fibrinogen are associated with dense fibrin clots, impaired fibrinolysis and increased cardiovascular risk. It was our objective to investigate whether BßArg448Lys adds to vascular risk by modulating fibrin network structure and/or fibrinolysis in diabetes. The primary aim was to study effects of BßArg448Lys on fibrin network characteristics in T2DM. Secondary aims investigated interactions between gender and BßArg448Lys substitution in relation to fibrin clot properties and vascular disease. Genotyping for BßArg448Lys and dynamic clot studies were carried out on 822 T2DM patients enrolled in the Edinburgh Type 2 Diabetes Study. Turbidimetric assays of individual plasma samples analysed fibrin clot characteristics with additional experiments conducted on clots made from purified fibrinogen, further examined by confocal and electron microscopy. Plasma clot lysis time in Bß448Lys was longer than Bß448Arg variant (mean ± SD; 763 ± 322 and 719 ± 351 seconds [s], respectively; p<0.05). Clots made from plasma-purified fibrinogen of individuals with Arg/Arg, Arg/Lys and Lys/Lys genotypes showed differences in fibre thickness (46.75 ± 8.07, 38.40 ± 6.04 and 25 ± 4.99 nm, respectively; p<0.001) and clot lysis time (419 ± 64, 442 ± 87 and 517 ± 65 s, respectively; p=0.02), directly implicating the polymorphism in the observed changes. Women with Bß448Lys genotype had increased risk of cerebrovascular events and were younger compared with Bß448Arg variant (67.2 ± 4.0 and 68.2 ± 4.4 years, respectively; p=0.035). In conclusion, fibrinogen Bβ448Lys variant is associated with thrombotic fibrin clots in diabetes independently of traditional risk factors. Prospective studies are warranted to fully understand the role of BβArg448Lys in predisposition to vascular ischaemia in T2DM with the potential to develop individualised antithrombotic management strategies.

[Diabetes Mellitus, a prothrombotic disease]

In patients with acute atherothrombotic disease, diabetes or glucose intolerance is frequently found. Indeed, the number of people with diabetes in the world continues to increase and is expected to reach more than 500 million people by 2035. Diabetes is a pathology commonly associated with both microvascular and macrovascular complications. Although the mortality of coronary artery disease has decreased significantly over the past 20 years, mortality in patients with type 2 diabetes has changed little and atherothrombotic events remain the leading cause of death in diabetic patients. Although our understanding of vascular pathology has greatly evolved in recent years, the cellular and molecular mechanisms linking thrombogenicity and diabetes remain incompletely understood. Type 1 and type 2 diabetes are prothrombotic pathologies. This prothrombotic state is due to both hyperglycemia and chronic hyperinsulinism. Among the different agonists involved in the increased thrombogenicity of diabetic patients, abnormalities can be found in all phases of coagulation. Increased procoagulant factors and tissue factor associated with impaired fibrinolysis, platelet hyperreactivity, endothelial dysfunction, leukocyte activation, low-grade inflammation, and microparticle involvement, they all play a role in the establishment of this prothrombotic condition. This review sought to provide an update on the prothrombotic nature of diabetes and its consequences in therapeutics.

Lipopolysaccharide-binding protein (LBP) reverses the amyloid state of fibrin seen in plasma of type 2 diabetics with cardiovascular co-morbidities

Type 2 diabetes (T2D) has many cardiovascular complications, including a thrombotic propensity. Many such chronic, inflammatory diseases are accompanied (and may be exacerbated, and possibly even largely caused) by amyloid fibril formation. Recognising that there are few strong genetic associations underpinning T2D, but that amyloidogenesis of amylin is closely involved, we have been seeking to understand what might trigger the disease. Serum levels of bacterial lipopolysaccharide are raised in T2D, and we recently showed that fibrin(ogen) polymerisation during blood clotting can be affected strongly by LPS. The selectivity was indicated by the regularisation of clotting by lipopolysaccharide-binding protein (LBP). Since coagulopathies are a hallmark of T2D, we wondered whether they might too be caused by LPS (and reversed by LBP). We show here, using SEM and confocal microscopy, that platelet-poor-plasma from subjects with T2D had a much greater propensity for hypercoagulability and for amyloidogenesis, and that these could both be reversed by LBP. These data imply that coagulopathies are an important feature of T2D, and may be driven by ‘hidden’ LPS. Given the prevalence of amyloid formation in the sequelae of diabetes, this opens up novel strategies for both the prevention and treatment of T2D.

Diabetic retinopathy and dysregulated innate immunity

Diabetic retinopathy (DR) is the progressive degeneration of retinal blood vessels and neurons. Inflammation is known to play an important role in the pathogenesis of DR. During diabetes, metabolic disorder leads to the release of damage-associated molecular patterns (DAMPs) both in the retina and elsewhere in the body. The innate immune system provides the first line of defense against the DAMPs. In the early stages of DR when the blood retinal barrier (BRB) is intact, retinal microglia and the complement system are activated at low levels. This low-level of inflammation (para-inflammation) is believed to be essential to maintain homeostasis and restore functionality. However, prolonged stimulation by DAMPs in the diabetic eye leads to maladaptation of the innate immune system and dysregulated para-inflammation may contribute to DR development. In the advanced stages of DR where immune privilege is comprised, circulating immune cells and serum proteins may infiltrate the retina and participate in retinal chronic inflammation and retinal vascular and neuronal damage. This review discusses how the innate immune system is activated in diabetes and DR. The view also discusses why the protective immune response becomes detrimental in DR.

Uric Acid Is Associated With Inflammatory Biomarkers and Induces Inflammation Via Activating the NF-κB Signaling Pathway in HepG2 Cells

Objective—

Serum uric acid (UA) has been associated with increased risk of cardiovascular and metabolic diseases. However, the causal mechanisms linking elevated UA levels to cardio-metabolic diseases are still unsettled. One potential explanation for how UA might contribute to cardio-metabolic disease might be its ability to induce systemic inflammation.

Approach and Results—

Herein, we report a positive relationship between serum UA and acute-phase reactants, such as high-sensitivity C-reactive protein, fibrinogen, ferritin, complement C3, and erythrocyte sedimentation rate, in a cohort of 2731 nondiabetic adults. The relationship remains significant after adjustment for several confounders, including age, sex, adiposity, anti-hypertensive treatments or diuretics use. To confirm the existence of a causal relationship, we examined the effect of UA on the expression of inflammatory biomarkers in human hepatoma HepG2 cells and characterized the signaling pathway by which UA acts. We show that UA stimulates the expression of C-reactive protein, fibrinogen, ferritin, and complement C3 in a dose-dependent fashion. The proinflammatory effects of UA were abrogated by benzbromarone, a specific inhibitor of UA transporters. Exposure of cells to UA resulted in activation of the IκB kinase/IκBα/NF-κB signaling pathway that was attenuated by benzbromarone. The effect of UA was completely blocked by the antioxidant N -acetylcysteine.

Conclusions—

These in vivo and in vitro data suggest that hyperuricemia might induce the expression of hepatic inflammatory molecules by activating the proinflammatory NF-κB signaling cascade. Because inflammation has an important pathogenetic role in metabolic and cardiovascular disease, our study may help understanding the mechanism by which hyperuricemia may contribute to organ damage.

Hypofibrinolysis in diabetes: a therapeutic target for the reduction of cardiovascular risk

An enhanced thrombotic environment and premature atherosclerosis are key factors for the increased cardiovascular risk in diabetes. The occlusive vascular thrombus, formed secondary to interactions between platelets and coagulation proteins, is composed of a skeleton of fibrin fibres with cellular elements embedded in this network. Diabetes is characterised by quantitative and qualitative changes in coagulation proteins, which collectively increase resistance to fibrinolysis, consequently augmenting thrombosis risk. Current long-term therapies to prevent arterial occlusion in diabetes are focussed on anti-platelet agents, a strategy that fails to address the contribution of coagulation proteins to the enhanced thrombotic milieu. Moreover, antiplatelet treatment is associated with bleeding complications, particularly with newer agents and more aggressive combination therapies, questioning the safety of this approach. Therefore, to safely control thrombosis risk in diabetes, an alternative approach is required with the fibrin network representing a credible therapeutic target. In the current review, we address diabetes-specific mechanistic pathways responsible for hypofibrinolysis including the role of clot structure, defects in the fibrinolytic system and increased incorporation of anti-fibrinolytic proteins into the clot. Future anti-thrombotic therapeutic options are discussed with special emphasis on the potential advantages of modulating incorporation of the anti-fibrinolytic proteins into fibrin networks. This latter approach carries theoretical advantages, including specificity for diabetes, ability to target a particular protein with a possible favourable risk of bleeding. The development of alternative treatment strategies to better control residual thrombosis risk in diabetes will help to reduce vascular events, which remain the main cause of mortality in this condition.

Clot Structure: A Potent Mortality Risk Factor in Patients on Hemodialysis

Patients with CKD on hemodialysis exhibit increased cardiovascular risk. Fibrin clot structure and clot lysis are crucially involved in development of cardiovascular events, but little is known about the influence of clot density on outcome in patients on hemodialysis. We determined fibrin clot structure parameters and effect on mortality in a prospective cohort of 171 patients on chronic hemodialysis (mean±SD age =59±11 years old; 54% men) using a validated turbidimetric assay. Kaplan-Meier analysis revealed that patients on hemodialysis with a denser clot structure had increased all-cause and cardiovascular mortality risks (log rank P=0.004 and P=0.003, respectively). Multivariate Cox regression models (adjusted for age, diabetes, sex, and duration of dialysis or fibrinogen, C-reactive protein, and complement C3) confirmed that denser clots are independently related to mortality risk. We also purified fibrinogen from healthy controls and patients on hemodialysis using the calcium-dependent IF-1 mAb against fibrinogen for additional investigation using mass spectrometric analysis and electron microscopy. Whereas purified fibrinogen from healthy controls displayed no post-translational modifications, fibrinogen from patients on hemodialysis was glycosylated and guanidinylated. Clots made of purified fibrinogen from patients on hemodialysis exhibited significantly thinner fibers compared with clots from fibrinogen of control individuals (mean±SD =63±2 and 77±2 nm, respectively; P<0.001). In vitro guanidinylation of fibrinogen from healthy subjects increased the formation of thinner fibers, suggesting that difference in fiber thickness might be at least partially due to post-translational modifications. Thus, in patients on hemodialysis, a denser clot structure may be a potent independent risk factor for mortality.

Complement gene variants in relation to autoantibodies to beta cell specific antigens and type 1 diabetes in the TEDDY Study

A total of 15 SNPs within complement genes and present on the ImmunoChip were analyzed in The Environmental Determinants of Diabetes in the Young (TEDDY) study. A total of 5474 subjects were followed from three months of age until islet autoimmunity (IA: n = 413) and the subsequent onset of type 1 diabetes (n = 115) for a median of 73 months (IQR 54-91). Three SNPs within ITGAM were nominally associated (p < 0.05) with IA: rs1143678 [Hazard ratio; HR 0.80; 95% CI 0.66-0.98; p = 0.032], rs1143683 [HR 0.80; 95% CI 0.65-0.98; p = 0.030] and rs4597342 [HR 1.16; 95% CI 1.01-1.32; p = 0.041]. When type 1 diabetes was the outcome, in DR3/4 subjects, there was nominal significance for two SNPs: rs17615 in CD21 [HR 1.52; 95% CI 1.05-2.20; p = 0.025] and rs4844573 in C4BPA [HR 0.63; 95% CI 0.43-0.92; p = 0.017]. Among DR4/4 subjects, rs2230199 in C3 was significantly associated [HR 3.20; 95% CI 1.75-5.85; p = 0.0002, uncorrected] a significance that withstood Bonferroni correction since it was less than 0.000833 (0.05/60) in the HLA-specific analyses. SNPs within the complement genes may contribute to IA, the first step to type 1 diabetes, with at least one SNP in C3 significantly associated with clinically diagnosed type 1 diabetes.

The role of complement activation in thrombosis and hemolytic anemias

OBJECTIVE

The objective of this study was to describe complement activation in hemostatic and pathologic states of coagulation and in the acquired and congenital hemolytic anemias.

METHODS AND RESULTS

We review published and emerging data on the involvement of the classic, alternative and lectin-based complement pathways in coagulation and the hemolytic anemias. The alternative pathway in particular is always "on," at low levels, and is particularly sensitive to hyper-activation in a variety of physiologic and pathologic states including infection, autoimmune disorders, thrombosis and pregnancy, requiring tight control predicated on a variety of soluble and membrane bound regulatory proteins. In acquired hemolytic anemias such as paroxysmal nocturnal hemoglobinuria (PNH) and cold agglutinin disease (CAD), the complement system directly induces red blood cell injury, resulting in intravascular and extravascular hemolysis. In congenital hemolytic anemias such as sickle cell disease and β-thalassemia, the complement system may also contribute to thrombosis and vascular disease. Complement activation may also lead to a storage lesion in red blood cells prior to transfusion.

CONCLUSION

Complement pathways are activated in hemolytic anemias and are closely linked with thrombosis. In acquired disorders such as PNH and possibly CAD, inhibition of the alternative complement pathway improves clinical outcomes and reduces thrombosis risk. Whether complement inhibition has a similar role in congenital hemolytic anemias apart from the atypical hemolytic-uremic (aHUS)-type thrombotic microangiopathies remains to be determined.

Is diabetes a hypercoagulable state? A critical appraisal

Diabetes mellitus (DM), a chronic disease with an increasing incidence and prevalence worldwide, is an established risk factor for arterial cardiovascular, cerebrovascular and peripheral vascular diseases including acute myocardial infarction, stroke and peripheral artery disease. On the other hand, its role as independent risk factor for venous thromboembolism (VTE) and for cardioembolic stroke or systemic embolism (SE) in patients with atrial fibrillation (AF) is more conflicting. Venous and arterial thromboses have traditionally been regarded as separate diseases, but recent studies have documented an association between these vascular complications. Cardiovascular risk factors may contribute to unprovoked VTE, and VTE may be an early symptomatic event in patients at high cardiovascular risk, including diabetic patients. Compelling evidences suggest that DM is associated with a higher risk of development and progression of AF. Furthermore, in AF patients with a coexisting DM the risk of cardioembolic stroke/SE appeared increased. Thus, DM has been included as one of the items of the CHADS2 score and of the subsequent CHA2DS2-VASc score that have been developed to assess the arterial tromboembolic risk of AF patients. Such a high incidence of thromboembolic events observed in these clinical subsets may be attributable to the DM-related prothrombotic state due to a number of changes in primary and secondary hemostasis. Although of potential clinical interest, unfortunately, to date, no study has properly evaluated the effects of drugs used to control blood glucose levels on the risk of venous thromboembolism and arterial cardioembolic events in patients with DM.