The influence of type 2 diabetes on fibrin clot properties in patients with coronary artery disease

Prothrombotic status in COVID‑19 with diabetes mellitus (Review)

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has caused an important social and health impact worldwide and the coronavirus disease-19 (COVID-19) has elicited devastating economy problems. The pathogenesis of SARS-CoV-2 infection is a complex mechanism and is considered to be the result of a challenging interaction, in which host and virus immune responses are the key elements. In this process, several inflammatory pathways are involved, and their initiation can have multiple consequences with a considerable impact on evolution, such as hyperinflammation and cytokine storm, thereby promoting activation of the coagulation system and fibrinolytic activity suppression. It is commonly recognized that COVID-19 severity involves multiple factors, including diabetes which increases the risk of developing different complications. This could be as a result of the low-grade inflammation as well as the innate and adaptive immune response dysfunction that is observed in patients with diabetes mellitus. In patients with diabetes, multiple metabolic disturbances which have a major impact in disturbing the balance between coagulation and fibrinolysis were discovered, thus the risk for thrombotic events is increased. Diabetes has been recognized as an important severity prognosis factor in COVID-19 cases and considering there is a significant association between diabetes and prothrombotic status, it could be responsible for the increased risk of thrombotic events with a worse prognosis.

Elevated factor XIa as a modulator of plasma fibrin clot properties in coronary artery disease

INTRODUCTION

Patients with coronary artery disease (CAD) display a prothrombotic fibrin clot phenotype, involving low permeability and resistance to lysis. The determinants of this phenotype remain elusive. Circulating tissue factor (TF) and activated factor XI (FXIa) are linked to arterial thromboembolism. We investigated whether detectable active TF and FXIa influence fibrin clot properties in CAD.

METHODS

In 118 CAD patients (median age 65 years, 78% men), we assessed Ks, an indicator of clot permeability, and clot lysis time (CLT) in plasma-based assays, along with the presence of active TF and FXIa. We also analysed proteins involved in clotting and thrombolysis, including fibrinogen, plasminogen activator inhibitor-1 (PAI-1) and thrombin activatable thrombolysis inhibitor (TAFI). During a median 106 month (interquartile range 95-119) follow-up, myocardial infarction (MI), stroke, systemic thromboembolism (SE) and cardiovascular (CV) death were recorded.

RESULTS

Circulating TF and FXIa, detected in 20.3% and 39.8% of patients, respectively, were associated with low Ks and prolonged CLT. Solely FXIa remained an independent predictor of low Ks and high CLT on multivariable analysis. Additionally, fibrinogen and PAI-1 were associated with low Ks, while PAI-1 and TAFI-with prolonged CLT. During follow-up low Ks and prolonged CLT increased the risk of MI and the latter also a composite endpoint of MI, stroke/SE or CV death.

CONCLUSIONS

To our knowledge, this study is the first to show that circulating FXIa is associated with prothrombotic fibrin clot properties in CAD, suggesting additional mechanisms through which FXIa inhibitors could act as novel antithrombotic agents in CAD.

Elevated plasma factor XI predicts cardiovascular events in patients with type 2 diabetes: a long-term observational study

BACKGROUND

Type 2 diabetes mellitus (T2DM) patients are at high risk of cardiovascular (CV) events. Factor XI (FXI) is associated with arterial thromboembolism, including myocardial infarction (MI), stroke, and CV mortality. The role of FXI in T2DM is unknown. We investigated whether plasma FXI is associated with CV events in T2DM patients in long-term observation.

METHODS

In 133 T2DM patients (aged 66 ± 8 years, 40.6% women, median T2DM duration 5 [2-10] years) we assessed plasma FXI levels, along with fibrin clot properties, thrombin generation, and fibrinolysis proteins. A composite endpoint of MI, stroke, or CV death, as well as CV mortality alone were assessed during a median follow-up of 72 months.

RESULTS

Plasma FXI above the 120% upper normal limit was detected in 25 (18.8%) patients and showed positive association with LDL cholesterol and thrombin activatable fibrinolysis inhibitor, but not glycated hemoglobin, inflammatory markers or thrombin generation. The composite endpoint (n = 21, 15.8%) and CV death alone (n = 16, 12%) were more common in patients with elevated FXI (hazard ratio [HR] 10.94, 95% confidence interval [CI] 4.46-26.87, p < 0.001 and HR 7.11, 95% CI 2.61-19.31, p < 0.001, respectively). On multivariable analysis, FXI remained an independent predictor of the composite endpoint and CV death, regardless of concomitant coronary artery disease.

CONCLUSIONS

To our knowledge, this study is the first to show that in T2DM patients, elevated FXI could predict major CV events, including mortality, which suggest that anti-FXI agents might be a potential novel antithrombotic option in this disease.

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.

Association of Complement C3 With Incident Type 2 Diabetes and the Mediating Role of BMI: A 10-Year Follow-Up Study

CONTEXT

Impairment of immune and inflammatory homeostasis is reported to be one of the causal factors of diabetes. However, the association of complement C3 levels with incident diabetes in humans remains unclear.

OBJECTIVE

This study aimed to examine the association between C3 levels and incident type 2 diabetes mellitus (T2DM), and further explore the potential mediating role of body mass index (BMI) in C3-T2DM associations.

METHODS

We determined serum C3 levels of 2662 nondiabetic middle-aged and elderly (64.62 ± 7.25 years) individuals from the Dongfeng-Tongji cohort at baseline. Cox regression was employed to examine the incidence of T2DM in relationship to C3 levels during 10 years of follow-up. Mediation analysis was further applied to assess potential effect of BMI on the C3-T2DM associations.

RESULTS

Overall, 711 (26.7%) participants developed T2DM during 23 067 person-years of follow-up. Higher serum C3 was significantly associated with higher risk of incident T2DM after full adjustment (HR [95% CI] = 1.16 [1.05, 1.27]; per SD higher). Compared with the first quartile of C3 levels, the HR in the fourth quartile was 1.52 (95% CI = [1.14, 2.02]; Ptrend = 0.029). Robust significant linear dose-response relationship was observed between C3 levels and BMI (Poverall < 0.001, Pnonlinear = 0.96). Mediation analyses indicated that BMI might mediate 41.0% of the associations between C3 and T2DM.

CONCLUSION

The present prospective study revealed that C3 could be an early biomarker for incident T2DM, and that BMI might play a potential mediating role in the C3-T2DM associations, which provided clues for the pathogenesis of diabetes.

Homocysteine thiolactone contributes to the prognostic value of fibrin clot structure/function in coronary artery disease

Fibrin clot structure/function contributes to cardiovascular disease. We examined sulfur-containing metabolites as determinants of fibrin clot lysis time (CLT) and maximum absorbance (Absmax) in relation to outcomes in coronary artery disease (CAD) patients. Effects of B-vitamin/folate therapy on CLT and Absmax were studied. Plasma samples were collected from 1,952 CAD patients randomized in a 2 x 2 factorial design to (i) folic acid, vitamins B12, B6; (ii) folic acid, vitamin B12; (iii) vitamin B6; (iv) placebo for 3.8 years in the Western Norway B-Vitamin Intervention Trial. Clot lysis time (CLT) and maximum absorbance (Absmax) were determined using a validated turbidimetric assay. Acute myocardial infarction (AMI) and mortality were assessed during a 7-year follow-up. Data were analyzed using bivariate and multiple regression. Survival free of events was studied using Kaplan Mayer plots. Hazard ratios (HR) and 95% confidence intervals (CI) were estimated using Cox proportional hazards models. Baseline urinary homocysteine (uHcy)-thiolactone and plasma cysteine (Cys) were significantly associated with CLT while plasma total Hcy was significantly associated with Absmax, independently of fibrinogen, triglycerides, vitamin E, glomerular filtration rate, body mass index, age, sex plasma creatinine, CRP, HDL-C, ApoA1, and previous diseases. B-vitamins/folate did not affect CLT and Absmax. Kaplan-Meier analysis showed associations of increased baseline CLT and Absmax with worse outcomes. In Cox regression analysis, baseline CLT and Absmax (>cutoff) predicted AMI (CLT: HR 1.58, 95% CI 1.10-2.28; P = 0.013. Absmax: HR 3.22, CI 1.19-8.69; P = 0.021) and mortality (CLT: HR 2.54, 95% CI 1.40-4.63; P = 0.002. Absmax: 2.39, 95% CI 1.17-4.92; P = 0.017). After adjustments for other prognostic biomarkers these associations remained significant. Cys and uHcy-thiolactone, but not tHcy, were significant predictors of AMI in Cox regression models that included CLT. Conclusions uHcy-thiolactone and plasma Cys are novel determinants of CLT, an important predictor of adverse CAD outcomes. CLT and Absmax were not affected by B-vitamin/folate therapy, which could account for the lack of efficacy of such therapy in CAD. Trial registration: URL: http://clinicaltrials.gov. Identifier: NCT00354081.

Sex-Specific Associations of Diabetes With Brain Structure and Function in a Geriatric Population

Introduction

Globally, women with dementia have a higher disease burden than men with dementia. In addition, women with diabetes especially are at higher risk for cognitive impairment and dementia compared to men with diabetes. Differences in the influence of diabetes on the cerebral vasculature and brain structure may contribute to these sex-specific differences. We examined sex-specific patterns in the relationship between diabetes and brain structure, as well as diabetes and cognitive function.

Methods

In total, 893 patients [age 79 ± 6.6 years, 446 (50%) women] from the Amsterdam Ageing Cohort with available data on brain structures (assessed by an MRI or CT scan) and cognitive function were included. All patients underwent a thorough standardized clinical and neuropsychological assessment (including tests on memory, executive functioning, processing speed, language). Brain structure abnormalities were quantified using visual scales.

Results

Cross-sectional multivariable regression analyses showed that diabetes was associated with increased incidence of cerebral lacunes and brain atrophy in women (OR 2.18 (1.00–4.72) but not in men. Furthermore, diabetes was associated with decreased executive function, processing speed and language in women [B −0.07 (0.00–0.13), −0.06 (0.02–0.10) and −0.07 (0.01–0.12) resp.] but not in men.

Conclusions

Diabetes is related to increased risk of having lacunes, brain atrophy and impaired cognitive function in women but not in men. Further research is required to understand the time trajectory leading up to these changes and to understand the mechanisms behind them in order to improve preventive health care for both sexes.

Hypercoagulability Impairs Plaque Stability in Diabetes-Induced Atherosclerosis

Diabetes mellitus, which is largely driven by nutritional and behavioral factors, is characterized by accelerated atherosclerosis with impaired plaque stability. Atherosclerosis and associated complications are the major cause of mortality in diabetic patients. Efficient therapeutic concepts for diabetes-associated atherosclerosis are lacking. Atherosclerosis among diabetic patients is associated with reduced endothelial thrombomodulin (TM) expression and impaired activated protein C (aPC) generation. Here, we demonstrate that atherosclerotic plaque stability is reduced in hyperglycemic mice expressing dysfunctional TM (TM^Pro/Pro mice), which have a pro-coagulant phenotype due to impaired thrombin inhibition and markedly reduced aPC generation. The vessel lumen and plaque size of atherosclerotic lesions in the truncus brachiocephalic were decreased in diabetic TM^Pro/Pro ApoE^-/- mice compared to diabetic ApoE^-/- mice. While lipid accumulation in lesions of diabetic TM^Pro/Pro ApoE^-/- mice was lower than that in diabetic ApoE^-/- mice, morphometric analyses revealed more prominent signs of instable plaques, such as a larger necrotic core area and decreased fibrous cap thickness in diabetic TM^Pro/Pro ApoE^-/- mice. Congruently, more macrophages and fewer smooth muscle cells were observed within lesions of diabetic TM^Pro/Pro ApoE^-/- mice. Thus, impaired TM function reduces plaque stability, a characteristic of hyperglycemia-associated plaques, thus suggesting the crucial role of impaired TM function in mediating diabetes-associated atherosclerosis.

Glycemic control and atrial fibrillation: an intricate relationship, yet under investigation

Atrial fibrillation (AF) and diabetes mellitus (DM) constitute two major closely inter-related chronic cardiovascular disorders whose concurrent prevalence rates are steadily increasing. Although, the pathogenic mechanisms behind the AF and DM comorbidity are still vague, it is now clear that DM precipitates AF occurrence. DM also affects the clinical course of established AF; it is associated with significant increase in the incidence of stroke, AF recurrence, and cardiovascular mortality. The impact of DM on AF management and prognosis has been adequately investigated. However, evidence on the relative impact of glycemic control using glycated hemoglobin levels is scarce. This review assesses up-to-date literature on the association between DM and AF. It also highlights the usefulness of glycated hemoglobin measurement for the prediction of AF and AF-related adverse events. Additionally, this review evaluates current anti-hyperglycemic treatment in the context of AF, and discusses AF-related decision-making in comorbid DM. Finally, it quotes significant remaining questions and sets some future strategies with the potential to effectively deal with this prevalent comorbidity.

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.

Hypofibrinolysis in type 2 diabetes and its clinical implications: from mechanisms to pharmacological modulation

A prothrombotic state is a typical feature of type 2 diabetes mellitus (T2DM). Apart from increased platelet reactivity, endothelial dysfunction, hyperfibrinogenemia, and hypofibrinolysis are observed in T2DM. A variety of poorly elucidated mechanisms behind impaired fibrinolysis in this disease have been reported, indicating complex associations between platelet activation, fibrin formation and clot structure, and fibrinolysis inhibitors, in particular, elevated plasminogen antigen inhibitor-1 levels which are closely associated with obesity. Abnormal fibrin clot structure is of paramount importance for relative resistance to plasmin-mediated lysis in T2DM. Enhanced thrombin generation, a proinflammatory state, increased release of neutrophil extracellular traps, elevated complement C3, along with posttranslational modifications of fibrinogen and plasminogen have been regarded to contribute to altered clot structure and impaired fibrinolysis in T2DM. Antidiabetic agents such as metformin and insulin, as well as antithrombotic agents, including anticoagulants, have been reported to improve fibrin properties and accelerate fibrinolysis in T2DM. Notably, recent evidence shows that hypofibrinolysis, assessed in plasma-based assays, has a predictive value in terms of cardiovascular events and cardiovascular mortality in T2DM patients. This review presents the current data on the mechanisms underlying arterial and venous thrombotic complications in T2DM patients, with an emphasis on hypofibrinolysis and its impact on clinical outcomes. We also discuss potential modulators of fibrinolysis in the search for optimal therapy in diabetic patients.

Fibrinogen and a Triad of Thrombosis, Inflammation, and the Renin-Angiotensin System in Premature Coronary Artery Disease in Women: A New Insight into Sex-Related Differences in the Pathogenesis of the Disease

Coronary artery disease (CAD) is the leading cause of morbidity and mortality in women worldwide. Its social impact in the case of premature CAD is particularly devastating. Many differences in the presentation of the disease in women as compared to men, including atypical symptoms, microvascular involvement, and differences in pathology of plaque formation or progression, make CAD diagnosis in women a challenge. The contribution of different risk factors, such as smoking, diabetes, hyperlipidemia, or obesity, may vary between women and men. Certain pathological pathways may have different sex-related magnitudes on CAD formation and progression. In spite of the already known differences, we lack sufficiently powered studies, both clinical and experimental, that assess the multipathogenic differences in CAD formation and progression related to sex in different age periods. A growing quantity of data that are presented in this article suggest that thrombosis with fibrinogen is of more concern in the case of premature CAD in women than are other coagulation factors, such as factors VII and VIII, tissue-type plasminogen activator, and plasminogen inhibitor-1. The rise in fibrinogen levels in inflammation is mainly affected by interleukin-6 (IL-6). The renin-angiotensin (RA) system affects the inflammatory process by increasing the IL-6 level. Unlike in men, in young women, the hypertensive arm of the RA system is naturally downregulated by estrogens. At the same time, estrogens promote the fibrinolytic path of the RA system. In young women, the promoted fibrinolytic process upregulates IL-6 release from leukocytes via fibrin degradation products. Moreover, fibrinogen, whose higher levels are observed in women, increases IL-6 synthesis and exacerbates inflammation, contributing to CAD. Therefore, the synergistic interplay between thrombosis, inflammation, and the RA system appears to have a more significant influence on the underlying CAD atherosclerotic plaque formation in young women than in men. This issue is further discussed in this review. Fibrinogen is the biomolecule that is central to these three pathways. In this review, fibrinogen is shown as the biomolecule that possesses a different impact on CAD formation, progression, and destabilization in women to that observed in men, being more pathogenic in women at the early stages of the disease than in men. Fibrinogen is a three-chain glycoprotein involved in thrombosis. Although the role of thrombosis is of great magnitude in acute coronary events, fibrinogen also induces atherosclerosis formation by accumulating in the arterial wall and enabling low-density lipoprotein cholesterol aggregation. Its level rises during inflammation and is associated with most cardiovascular risk factors, particularly smoking and diabetes. It was noted that fibrinogen levels were higher in women than in men as well as in the case of premature CAD in women. The causes of this phenomenon are not well understood. The higher fibrinogen levels were found to be associated with a greater extent of coronary atherosclerosis in women with CAD but not in men. Moreover, the lysability of a fibrin clot, which is dependent on fibrinogen properties, was reduced in women with subclinical CAD compared to men at the same stage of the disease, as well as in comparison to women without coronary artery atherosclerosis. These findings suggest that the magnitude of the pathological pathways contributing to premature CAD differs in women and men, and they are discussed in this review. While many gaps in both experimental and clinical studies on sex-related differences in premature CAD exist, further studies on pathological pathways are needed.

Fibrin Clot Properties in Atherosclerotic Vascular Disease: From Pathophysiology to Clinical Outcomes

Fibrin is a major component of thrombi formed on the surface of atherosclerotic plaques. Fibrin accumulation as a consequence of local blood coagulation activation takes place inside atherosclerotic lesions and contributes to their growth. The imbalance between thrombin-mediated fibrin formation and fibrin degradation might enhance atherosclerosis in relation to inflammatory states reflected by increased fibrinogen concentrations, the key determinant of fibrin characteristics. There are large interindividual differences in fibrin clot structure and function measured in plasma-based assays and in purified fibrinogen-based systems. Several observational studies have demonstrated that subjects who tend to generate denser fibrin networks displaying impaired clot lysis are at an increased risk of developing advanced atherosclerosis and arterial thromboembolic events. Moreover, the majority of cardiovascular risk factors are also associated with unfavorably altered fibrin clot properties, with their improvement following effective therapy, in particular with aspirin, statins, and anticoagulant agents. The prothrombotic fibrin clot phenotype has been reported to have a predictive value in terms of myocardial infarction, ischemic stroke, and acute limb ischemia. This review article summarizes available data on the association of fibrin clot characteristics with atherosclerotic vascular disease and its potential practical implications.

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.

Effects of Hyperglycemia and Diabetes Mellitus on Coagulation and Hemostasis

In patients with diabetes, metabolic disorders disturb the physiological balance of coagulation and fibrinolysis, leading to a prothrombotic state characterized by platelet hypersensitivity, coagulation disorders and hypofibrinolysis. Hyperglycemia and insulin resistance cause changes in platelet number and activation, as well as qualitative and/or quantitative modifications of coagulatory and fibrinolytic factors, resulting in the formation of fibrinolysis-resistant clots in patients with diabetes. Other coexisting factors like hypoglycemia, obesity and dyslipidemia also contribute to coagulation disorders in patients with diabetes. Management of the prothrombotic state includes antiplatelet and anticoagulation therapies for diabetes patients with either a history of cardiovascular disease or prone to a higher risk of thrombus generation, but current guidelines lack recommendations on the optimal antithrombotic treatment for these patients. Metabolic optimizations like glucose control, lipid-lowering, and weight loss also improve coagulation disorders of diabetes patients. Intriguing, glucose-lowering drugs, especially cardiovascular beneficial agents, such as glucagon-like peptide-1 receptor agonists and sodium glucose co-transporter inhibitors, have been shown to exert direct anticoagulation effects in patients with diabetes. This review focuses on the most recent progress in the development and management of diabetes related prothrombotic state.

Modulating the rate of fibrin formation and clot structure attenuates microvascular thrombosis in systemic inflammation

Systemic inflammation can lead to coagulopathy and disseminated intravascular coagulation (DIC). In prior studies, the recombinant A2 domain of human von Willebrand factor (VWF; A2 protein) attenuated DIC and decreased mortality in lipopolysaccharide (LPS)-treated mice. Here, we performed studies to dissect the mechanism by which the A2 protein moderates DIC. We used confocal microscopy to analyze the fibrin clot structure in plasma from healthy humans and endotoxemic mice, turbidity assays to examine fibrin polymerization, and a murine model for LPS-induced DIC and introduced a loss-of-function mutation into the A2 protein for fibrin. The mutation of the residue E1567 located in the α2 helix of the folded A2 domain of VWF inhibited binding activity for fibrin, possibly mapping a novel region containing a putative binding site for fibrin. The A2 protein increased the initial rate of change of fibrin polymerization, intercalated into the fibrin network, and modified the resultant clot structure in vitro. Furthermore, ex vivo experiments using plasma from mice with endotoxemia treated with the A2 protein revealed an increased rate of fibrin formation and an altered clot structure as compared with plasma from nontreated sick animals. Moreover, and in contrast to the A2 mutant, the A2 protein improved survival and reduced fibrin deposition and microvascular thrombosis in mice with endotoxemia-induced DIC. Importantly, in vivo and in vitro studies indicated that the A2 protein did not affect experimental thrombosis. Thus, we provide evidence for a novel treatment to attenuate systemic inflammation-induced coagulopathy/DIC via targeting fibrin formation, without an increased risk for bleeding.

Plasma fibrin clot properties and cardiovascular mortality in patients with type 2 diabetes: a long-term follow-up study

Background

Patients with type 2 diabetes mellitus (T2DM) are at high risk of cardiovascular mortality, but the mechanisms behind this remain unclear. Prothrombotic fibrin clot properties have been shown in T2DM and cardiovascular disease. We hypothesized that formation of denser clots, which are resistant to fibrinolysis, has a negative impact on cardiovascular mortality in T2DM.

Methods

We studied 133 T2DM patients aged 43–83 years. Plasma fibrin clot turbidity, permeation, compaction, and efficiency of clot lysis using 3 assays including the determination of maximum concentration (D-D_max) and rate of increase in D-dimer concentration (D-D_rate) released during tissue plasminogen activator-induced degradation, were evaluated at the time of enrollment, along with thrombin generation and fibrinolytic proteins. During a median follow-up period of 72 months, cardiovascular mortality was recorded.

Results

Cardiovascular deaths (n = 16, 12%) occurred more frequently in patients with increased D-D_max (> 4.26 mg/l, hazard ratio [HR] 5.43, 95% confidence interval [CI] 1.99–14.79), or decreased D-D_rate (< 0.07 mg/l/min, HR 2.97, 95% CI 1.07–8.23), or increased peak thrombin (> 283.5 nM, HR 5.65, 95% CI 2.07–15.51). These predictors had an even more potent impact on cardiovascular mortality in patients with prior cardiovascular disease (64.7%) and with corresponding risks as follows: HR 6.18, 95% CI 2.02–18.96; HR 8.98, 95% CI 2.99–26.96; and HR 5.35, 95% CI 1.62–17.72, respectively. Other investigated fibrin variables and fibrinolytic proteins did not associate with cardiovascular mortality. In multivariable analysis, cardiovascular mortality was predicted by D-D_max > 4.26 mg/l, age > 65 years, prior cardiovascular disease, and C-reactive protein > 3 mg/l.

Conclusions

This study is the first to show that formation of denser fibrin clots resistant to fibrinolysis could be a risk factor for long-term cardiovascular mortality in T2DM.

Reductions in plasmin inhibitor and fibrinogen predict the improved fibrin clot lysis 6 months after obesity surgery

Prothrombotic and metabolic variables are decreased after obesity surgery, and fibrin clot lysis is increased. It is unknown how fibrinolytic variables are affected, and whether fibrinolytic and metabolic changes predict the enhanced clot lysis. Study aims were to determine fibrinolytic biomarkers before and 6 months after Roux-en-Y gastric bypass (RYGB) and to identify predictors of the RYGB-induced increase in clot lysis. Women (n = 42) and men (n = 18) with obesity underwent RYGB, and factor XIII (FXIII), thrombin activatable fibrinolysis inhibitor (TAFI), plasminogen and plasmin inhibitor (PI) were measured before and 6 months after surgery. Regression analyses identified determinants of the RYGB-induced increase in clot lysis among changes in fibrinogen and in fibrinolytic and metabolic variables. Results showed that after RYGB, FXIII, TAFI, plasminogen and PI were reduced (P < .0005). Reductions in PI (β = -0.59) and fibrinogen (β = -0.35), together with age (β = -0.22) and male sex (β = 0.22), predicted the enhanced clot lysis with the model explaining 56% (P < .0005). Predictors of the reduction in PI were reductions in cholesterol (β = 0.37) and glucose (β = 0.29), together with male sex (β = -0.28), whereas reductions in fibrinogen were predicted by lowering of interleukin-6 (IL-6) (β = 0.32). In conclusion, fibrinolytic variables were reduced 6 months after RYGB. Targeting PI and fibrinogen, by reducing metabolic variables such as glucose, cholesterol and IL-6, has a profibrinolytic effect in obesity.

Fibrin Clot Formation and Lysis in Plasma

Disturbance in the balance between fibrin formation and fibrinolysis can lead to either bleeding or thrombosis; however, our current routine coagulation assays are not sensitive to altered fibrinolysis. The clot formation and lysis assay is a dynamic plasma-based analysis that assesses the patient’s capacity for fibrin formation and fibrinolysis by adding an activator of coagulation as well as fibrinolysis to plasma and measuring ex vivo fibrin clot formation and breakdown over time. This assay provides detailed information on the fibrinolytic activity but is currently used for research only, as the assay is prone to inter-laboratory variation and as it demands experienced laboratory technicians as well as specialized personnel to validate and interpret the results. Here, we describe a protocol for the clot formation and lysis assay used at our research laboratory.

Plasma Fibrin Clot Properties as Determinants of Bleeding Time in Human Subjects: Association with Histidine-Rich Glycoprotein

Aims

Fibrin formation and histidine-rich glycoprotein (HRG) are involved in primary hemostasis and wound healing. Little is known regarding the relationship of clot characteristics, bleeding time, and wound healing.

Methods and Results

We studied 154 patients with coronary artery disease (CAD) and 154 subjects free of CAD matched for age, obesity, and current smoking. We evaluated bleeding time (BT) using standardized skin incisions on a forearm, along with plasma clot permeability (K_s), clot lysis time (CLT), and histidine-rich glycoprotein (HRG). Compared with controls, BT was 45% shorter in CAD cases. CAD patients had 32% lower K_s), clot lysis time (CLT), and histidine-rich glycoprotein (HRG). Compared with controls, BT was 45% shorter in CAD cases. CAD patients had 32% lower p < 0.001). After adjusting for potential confounders, K_s), clot lysis time (CLT), and histidine-rich glycoprotein (HRG). Compared with controls, BT was 45% shorter in CAD cases. CAD patients had 32% lower n = 79, 25.6%) was independently predicted by both short and prolonged BT in CAD cases (OR 21.87, 95% CI 7.41-64.55 and OR 10.17, 95% CI 2.88-35.97) and controls (OR 5.94, 95% CI 2.29-15.41 and OR 14.76, 95% CI 4.29-50.77, respectively).

Conclusions

The study shows that plasma fibrin clot density and HRG may influence BT and that appropriate skin wound healing is associated with medium BT. Translational Perspective. Elucidation of the complex relationships between plasma fibrin clot phenotype and wound healing might have important practical implications.

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.

Aspirin, clopidogrel and prasugrel monotherapy in patients with type 2 diabetes mellitus: a double-blind randomised controlled trial of the effects on thrombotic markers and microRNA levels

BACKGROUND

Despite increased atherothrombotic risk in type 2 diabetes mellitus, (T2DM) the best preventative antithrombotic strategy remains undetermined. We defined the effects of three antiplatelet agents on functional readout and biomarker kinetics in platelet activation and coagulation in patients with T2DM.

MATERIALS AND METHODS

56 patients with T2DM were randomised to antiplatelet monotherapy with aspirin 75 mg once daily (OD), clopidogrel 75 mg OD or prasugrel 10 mg OD during three periods of a crossover study. Platelet aggregation (PA) was determined by light-transmittance aggregometry and P-selectin expression by flow cytometry. Markers of fibrin clot dynamics, inflammation and coagulation were measured. Plasma levels of 14 miRNA were assessed by quantitative polymerase chain reactions.

RESULTS

Of the 56 patients, 24 (43%) were receiving aspirin for primary prevention of ischaemic events and 32 (57%) for secondary prevention. Prasugrel was the strongest inhibitor of ADP-induced PA (mean ± SD maximum response to 20μmol/L ADP 77.6 ± 8.4% [aspirin] vs. 57.7 ± 17.6% [clopidogrel] vs. 34.1 ± 14.1% [prasugrel], p < 0.001), P-selectin expression (30 μmol/L ADP; 45.1 ± 21.4% vs. 27.1 ± 19.0% vs. 14.1 ± 14.9%, p < 0.001) and collagen-induced PA (2 μg/mL; 62.1 ± 19.4% vs. 72.3 ± 18.2% vs. 60.2 ± 18.5%, p < 0.001). Fibrin clot dynamics and levels of coagulation and inflammatory proteins were similar. Lower levels of miR-24 (p = 0.004), miR-191 (p = 0.019), miR-197 (p = 0.009) and miR-223 (p = 0.014) were demonstrated during prasugrel-therapy vs. aspirin. Circulating miR-197 was lower in those cardiovascular disease during therapy with aspirin (p = 0.039) or prasugrel (p = 0.0083).

CONCLUSIONS

Prasugrel monotherapy in T2DM provided potent platelet inhibition and reduced levels of a number of platelet-associated miRNAs. miR-197 is a potential marker of cardiovascular disease in this population. Clinical outcome studies investigating prasugrel monotherapy are warranted in individuals with T2DM. Trial registration EudraCT, 2009-011907-22. Registered 15 March 2010, https://www.clinicaltrialsregister.eu/ctr-search/trial/2009-011907-22/GB.

Sex difference in fibrin clot lysability: Association with coronary plaque composition

INTRODUCTION

Fibrin clot lysability is associated with development of cardiovascular disease (CVD). We evaluated sex-differences in fibrin clot lysability and the association with coronary plaque composition determined by computed tomography angiography (CTA).

METHODS

Middle-aged citizens without known CVD were randomly selected from a national registry. A coronary CTA assessed volumes of calcified-, non-calcified-, low-density non-calcified-, and total- plaque using a validated plaque quantification software. A non-enhanced cardiac CT scan assessed the Agatston score. Fibrin structure properties were determined using turbidimetric methods. Plasma concentrations of C-reactive protein and fibrinogen were assessed.

RESULTS

138 individuals (71 women) participated. Men more frequently had coronary plaques compared to women, P < 0.05. Coronary plaque features were comparable between men and women, P > 0.05. Women with total plaque volume > 0 mm³ had lower fibrin clot lysability compared to women with total plaque volume = 0 mm³, adjusted difference [95% confidence interval] 10.28 [1.42-19.15], P = 0.02, and a fibrinogen-dependent lower fibrin clot lysability compared to men with and without coronary plaques, 6.82 [-2.67-16.31], P = 0.16, and 8.73 [-0.43-17.89], P = 0.06, respectively. Fibrinogen correlated with all the coronary plaque features (correlation coefficient r = 0.42-0.57) only in women with total plaque volume > 0 mm³, all P < 0.01.

CONCLUSION

Asymptomatic women with coronary plaques assessed by coronary CTA have reduced fibrin clot lysability compared to both women without coronary plaques and men, suggesting a sex-dependent link between coronary atherosclerosis and fibrin clot lysability.

Sex differences in risk factors for vascular contributions to cognitive impairment & dementia

Vascular contributions to cognitive impairment and dementia (VCID) is the second most common cause of dementia. While males overall appear to be at a slightly higher risk for VCID throughout most of the lifespan (up to age 85), some risk factors for VCID more adversely affect women. These include female-specific risk factors associated with pregnancy related disorders (e.g. preeclampsia), menopause, and poorly timed hormone replacement. Further, presence of certain co-morbid risk factors, such as diabetes, obesity and hypertension, also may more adversely affect women than men. In contrast, some risk factors more greatly affect men, such as hyperlipidemia, myocardial infarction, and heart disease. Further, stroke, one of the leading risk factors for VCID, has a higher incidence in men than in women throughout much of the lifespan, though this trend is reversed at advanced ages. This review will highlight the need to take biological sex and common co-morbidities for VCID into account in both preclinical and clinical research. Given that there are currently no treatments available for VCID, it is critical that we understand how to mitigate risk factors for this devastating disease in both sexes.

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.

Duration of Dual Antiplatelet Therapy Following Drug-Eluting Stent Implantation in Diabetic and Non-Diabetic Patients: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

BACKGROUND

Diabetic patients account for an increasing number of patients undergoing percutaneous coronary intervention (PCI). However, diabetes mellitus (DM) is associated with increased residual platelet activity during dual antiplatelet treatment (DAPT) and DM patients have worse clinical outcomes after PCI as compared to non-DM.

OBJECTIVE

To evaluate efficacy and safety of short duration DAPT (S-DAPT) and long duration DAPT (L-DAPT) after drug eluting stent (DES) implantation in DM and non-DM patients.

METHODS

We searched Medline, Embase, and Cochrane Central Register of Controlled Trials (CENTRAL) to identify randomized controlled trials (RCTs) assessing the effect of S-DAPT versus L-DAPT after DES implantation in DM and non-DM patients. Efficacy endpoints were all-cause mortality, cardiac mortality, myocardial infarction (MI), stent thrombosis (ST), target vessel revascularization (TVR), and composite end point of net adverse clinical events (NACE) (all-cause mortality, cardiac mortality, MI, ST, TVR, stroke, major bleeding). Safety endpoints were major bleeding and stroke. Event rates were compared using a forest plot of relative risk using a random effects model.

RESULTS

We included eight RCTs that randomized 28,318 patients to S-DAPT versus L-DAPT (8234 DM and 20,084 non-DM). S-DAPT was associated with an increased rate of ST in non-DM patients [3.67 (2.04, 6.59)]. There was no significant difference in the rate of all-cause mortality, cardiac mortality, ST, MI, TVR, major bleeding, stroke and NACE with S-DAPT and L-DAPT in DM patients [1.19 (0.72-1.95); 1.25 (0.69, 2.25); 1.52 (0.70, 3.29); 1.33 (0.88, 2.01); 1.39 (0.89, 2.17); 0.92 (0.19, 4.42); 0.98 (0.29, 3.28); and 0.94 (0.57, 1.54) respectively]. Further, there was no significant difference in the rate of all-cause mortality, cardiac mortality, MI, TVR, major bleeding, stroke and NACE with S-DAPT and L-DAPT in non-DM patients [0.93 (0.58, 1.48); 0.75 (0.42, 1.35); 1.52 (0.81, 2.83); 0.99 (0.71, 1.39); 0.72 (0.28, 1.84); 1.01 (0.40, 2.56); and 1.01 (0.77, 1.32) respectively].

CONCLUSION

Compared to L-DAPT, S-DAPT was associated with significant increase in rate of ST in non-DM patients. Duration of DAPT had no significant impact on rates of all-cause mortality, cardiac mortality, MI, ST and TVR among DM patients.

The influence of low-grade inflammation on platelets in patients with stable coronary artery disease

Inflammation is likely to be involved in all stages of atherosclerosis. Numerous inflammatory biomarkers are currently being studied, and even subtle increases in inflammatory biomarkers have been associated with increased risk of cardiovascular events in patients with coronary artery disease (CAD). Low-grade inflammation may influence both platelet production and platelet activation potentially leading to enhanced platelet aggregation. Thrombopoietin is considered the primary regulator of platelet production, but it likely acts in conjunction with numerous cytokines, of which many have altered levels in CAD. Previous studies have shown that high-sensitive C-reactive protein (CRP) independently predicts increased platelet aggregation in stable CAD patients. Increased levels of CRP, fibrinogen, interleukin-6, stromal cell-derived factor-1, CXC motif ligand 16, macrophage migration inhibitory factor, RANTES, calprotectin, and copeptin have been associated with increased risk of cardiovascular events in CAD patients. Additionally, some of these inflammatory markers have been associated with enhanced platelet activation and aggregation. However, CRP and other inflammatory markers provide only limited additional predictive value to classical risk factors such as smoking, blood pressure, and cholesterol levels. Existing data do not clarify whether inflammation simply accompanies CAD and increased production and aggregation of platelets, or whether a causal relationship exists. In this review, we provide a comprehensive overview of inflammatory markers in stable CAD with particular emphasis on platelet production, activation, and aggregation in CAD patients.

Coronary artery disease-associated genetic variants and biomarkers of inflammation

INTRODUCTION

Genetic constitution and inflammation both contribute to development of coronary artery disease (CAD). Several CAD-associated single-nucleotide polymorphisms (SNPs) have recently been identified, but their functions are largely unknown. We investigated the associations between CAD-associated SNPs and five CAD-related inflammatory biomarkers.

METHODS

We genotyped 45 CAD-associated SNPs in 701 stable CAD patients in whom levels of high-sensitivity C-reactive protein (hsRCP), interleukin-6, calprotectin, fibrinogen and complement component 3 levels had previously been measured. A genetic risk score was calculated to assess the combined risk associated with all the genetic variants. A multiple linear regression model was used to assess associations between the genetic risk score, single SNPs, and the five inflammatory biomarkers.

RESULTS

The minor allele (G) (CAD risk allele) of rs2075650 (TOMM40/APOE) was associated with lower levels of high-sensitivity C-reactive protein (effect per risk allele: -0.37 mg/l [95%CI -0.56 to -0.18 mg/l]). The inflammatory markers tested showed no association with the remaining 44 SNPs or with the genetic risk score.

CONCLUSIONS

In stable CAD patients, the risk allele of a common CAD-associated marker at the TOMM40/APOE locus was associated with lower hsCRP levels. No other genetic variants or the combined effect of all variants were associated with the five inflammatory biomarkers.

Elevated NT-proBNP is associated with unfavorably altered plasma fibrin clot properties in atrial fibrillation

BACKGROUND

Dense fibrin clot formation and hypofibrinolysis have been reported in atrial fibrillation (AF). It is unclear which factors affect fibrin clot properties in AF.

METHODS AND RESULTS

We investigated plasma fibrin clot permeability (K_s), clot lysis time (CLT), endogenous thrombin potential (ETP) as well as other coagulation and fibrinolysis parameters along with N-terminal pro-B-type natriuretic peptide (NT-proBNP) in 160 AF patients (median age, 70.5years). Previous stroke (n=15; 9.4%) was associated with decreased K_s (P=0.04) and longer CLT (P=0.005), together with higher antiplasmin (P=0.03) and lower tissue-type plasminogen activator (P=0.01). Lower K_s (P=0.04) and tendency towards longer CLT (P=0.10) were observed in patients with a left atrium diameter>40mm. Patients with a CHA₂DS₂-VASc score of 3 or more (82.5%) were characterized by higher thrombin-activatable fibrinolysis inhibitor antigen (P=0.009). K_s was inversely correlated with log NT-proBNP (r=-0.34, P<0.0001), plasminogen activator inhibitor-1 (PAI-1) antigen (r=-0.24, P=0.002) and C-reactive protein (r=-0.18, P=0.02), while CLT was positively correlated with log NT-proBNP (R=0.61, P<0.0001) and ETP (r=0.37, P<0.0001), which were interrelated (r=0.59, P<0.0001). After adjustment for potential confounders, PAI-1 (odds ratio [OR]: 1.14; 95% confidence interval [CI]: 1.02-1.26) was the only independent predictor of low K_s (the lowest quartile,≤6×10^-9cm²), while NT-proBNP (OR: 1.21; 95% CI: 1.12-1.31) and PAI-1 (OR: 1.30; 95% CI: 1.12-1.51) both predicted prolonged CLT (the top quartile,≥109min).

CONCLUSION

In AF patients prothrombotic fibrin clot properties assessed ex vivo are determined by PAI-1 and NT-proBNP and this phenotype is associated with prior ischemic stroke.

Consistent platelet inhibition with ticagrelor 60 mg twice-daily following myocardial infarction regardless of diabetes status

Diabetes increases cardiovascular risk and reduces pharmacodynamic response to some oral antiplatelet drugs. This study aimed to determine whether ticagrelor 60 mg twice daily (bid) provided potent and consistent platelet inhibition in patients with vs without diabetes in the PEGASUS-TIMI 54 platelet function substudy. Out of 180 patients studied, 58 patients were randomised to and had received at least four weeks of ticagrelor 60 mg bid, with 20 (34 %) having diabetes, 58 patients received ticagrelor 90 mg bid, with 12 (21 %) having diabetes, and 64 patients received placebo, with 18 (28 %) having diabetes. Blood was sampled pre- and 2 hours post-maintenance dose. In patients treated with ticagrelor 60 mg bid, on-treatment platelet reactivity to ADP, as determined by light transmission aggregometry (LTA), VerifyNow and VASP, was similar in patients with vs without diabetes (LTA post-dose, ADP 20 µM: 29 ± 14 vs 34 ± 10 %, respectively; p = 0.19). A consistent inhibitory effect of ticagrelor 60 mg bid was observed pre- and post-dose regardless of diabetes status, even in insulin-treated patients. Patients with diabetes did not have an increased incidence of high platelet reactivity in either ticagrelor group. Platelet reactivity was similar in patients with diabetes treated with ticagrelor 60 mg vs 90 mg bid. Pharmacokinetics of ticagrelor were not affected by diabetes status. In conclusion, ticagrelor 60 mg bid is equally effective at reducing platelet reactivity in patients with and without diabetes, yielding a consistently high level of platelet inhibition regardless of diabetes status.

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.

Effect of Diabetes and Glycemic Control on Ischemic Stroke Risk in AF Patients: ATRIA Study

BACKGROUND

Diagnosed diabetes mellitus (DM) is a consistently documented risk factor for ischemic stroke in patients with atrial fibrillation (AF).

OBJECTIVES

The purpose of this study was to assess the association between duration of diabetes and elevated hemoglobin A1c (HbA1c) with risk of stroke among diabetic patients with AF.

METHODS

We assessed this association in the ATRIA (Anticoagulation and Risk Factors in Atrial Fibrillation) California community-based cohort of AF patients (study years 1996 to 2003) where all events were clinician adjudicated. We used Cox proportional hazards regression to estimate the rate of ischemic stroke in diabetic patients according to time-varying measures of estimated duration of diabetes (≥3 years compared with <3 years) and HbA1c values (≥9.0% and 7.0% to 8.9% compared with <7.0%), focusing on periods where patients were not anticoagulated.

RESULTS

There were 2,101 diabetic patients included in the duration analysis: 40% with duration <3 years and 60% with duration ≥3 years at baseline. Among 1,933 diabetic patients included in the HbA1c analysis, 46% had HbA1c <7.0%, 36% between 7.0% and 8.9%, and 19% ≥9.0% at baseline. Duration of diabetes ≥3 years was associated with an increased rate of ischemic stroke compared with duration <3 years (adjusted hazard ratio [HR]: 1.74, 95% confidence interval [CI]: 1.10 to 2.76). The increased stroke rate was observed in older (age ≥75 years) and younger (age <75 years) individuals. Neither poor glycemic control (HbA1c ≥9.0%, adjusted HR: 1.04, 95% CI: 0.57 to 1.92) nor moderately increased HbA1c (7.0% to 8.9%, adjusted HR: 1.21, 95% CI: 0.77 to 1.91) were significantly associated with an increased rate of ischemic stroke compared with patients who had HbA1c <7.0%.

CONCLUSIONS

Duration of diabetes is a more important predictor of ischemic stroke than glycemic control in patients who have diabetes and AF.

The Influence of Haemoglobin A1c Levels on Platelet Aggregation and Platelet Turnover in Patients with Coronary Artery Disease Treated with Aspirin

Background

Hyperglycaemia may attenuate the antiplatelet effect of aspirin and thereby increase the risk of cardiovascular events. We investigated the influence of increased haemoglobin A1c (HbA1c) levels on platelet aggregation and turnover in a large cohort of patients with coronary artery disease (CAD) with type 2 diabetes, prediabetes or no diabetes.

Methods

In this observational study, we included 865 stable CAD patients on 75 mg aspirin as mono-therapy of whom 242 patients had type 2 diabetes and were receiving antidiabetic drugs. Among 623 patients without diabetes, we classified 303 patients with prediabetes (HbA1c ≥5.7–6.4% [39–47 mmol/mol]) naive to antidiabetic drugs. Platelet aggregation was evaluated by the Multiplate Analyzer using arachidonic acid and collagen and by the VerifyNow Aspirin. Platelet turnover was evaluated by immature platelets using flow cytometry and platelet activation by soluble P-selectin.

Results

CAD patients with type 2 diabetes had higher platelet aggregation (all p-values <0.01), platelet turnover (immature platelet count, p<0.01) and platelet activation (p<0.001) than patients without diabetes. CAD patients with prediabetes had increased platelet aggregation (p = 0.02) and platelet count (p = 0.02) compared with patients without diabetes. Increased levels of HbA1c correlated positively with increased platelet aggregation using arachidonic acid (r = 0.19, p<0.0001), collagen (r = 0.10, p<0.01) and VerifyNow (r = 0.15, p<0.0001), and with platelet count (r = 0.08, p = 0.01), immature platelet count (r = 0.11, p<0.001) and soluble P-selectin (r = 0.15, p<0.0001). These associations were mainly evident in non-diabetic and prediabetic CAD patients.

Conclusions

CAD patients with prediabetes and diabetes may have attenuated antiplatelet effect of aspirin compared with CAD patients without diabetes. This may be related to increased platelet count in patients with prediabetes. Increased levels of HbA1c correlated positively, though weakly, with increased platelet aggregation, platelet turnover and platelet activation.

Calprotectin and platelet aggregation in patients with stable coronary artery disease

BACKGROUND

Recent studies suggest that the inflammation-associated protein calprotectin may be implicated in the pathogenesis of coronary artery disease (CAD). However, the impact of calprotectin levels on platelet aggregation in CAD patients has never been investigated.

OBJECTIVES

We investigated the association between calprotectin levels and platelet aggregation in stable, high-risk CAD patients receiving aspirin as mono antiplatelet therapy. Furthermore, we aimed to investigate independent clinical and laboratory determinants of calprotectin levels.

METHODS

We performed a cross-sectional study including 581 stable, high-risk CAD patients. All patients received 75 mg aspirin daily as mono antiplatelet therapy. Platelet aggregation was assessed by 1) impedance aggregometry (Multiplate Analyzer) using arachidonic acid (AA) and collagen as agonists and by 2) the VerifyNow Aspirin Assay. Low-grade inflammation was evaluated by calprotectin, high-sensitive C-reactive-protein (hs-CRP) and interleukin-6. Platelet activation was assessed by soluble P-selectin, and cyclooxygenase-1 inhibition was evaluated by serum thromboxane B2, both measured by ELISA.

RESULTS

Calprotectin levels correlated positively with platelet aggregation according to Multiplate Analyzer (r=0.12, p=0.01). Additionally, calprotectin was positively associated with leukocytes (r=0.33, p<0.0001), hs-CRP (r=0.31, p<0.0001), interleukin-6 (r=0.28, p<0.0001), soluble P-selectin (r=0.10, p=0.02) and serum thromboxane B2 (r=0.10, p=0.02). Type 2 diabetes mellitus was an independent predictor of increased calprotectin levels (p=0.004), and trends were seen for body mass index (p=0.06) and smoking (p=0.07). Compliance with aspirin was confirmed by low serum thromboxane B2 levels in all patients (median [25%;75%]: 1.07 [0.52;1.87] ng/mL).

CONCLUSION

Calprotectin levels correlated positively, though weakly, with platelet aggregation and activation as well as serum thromboxane B2 in high-risk, stable CAD patients treated with aspirin.

Plasma fibrin clot phenotype independently affects intracoronary thrombus ultrastructure in patients with acute myocardial infarction

Determinants of intracoronary thrombus (ICT) composition in patients with ST-elevation myocardial infarction (STEMI) are largely unknown. We sought to investigate whether plasma fibrin phenotype and platelet reactivity affect ICT ultrastructure. We assessed the content of fibrin, platelets and erythrocytes including polyhedrocytes by scanning electron microscopy on the surface and inside ICT aspirated from 80 STEMI patients within 12 hours since chest pain onset. Plasma fibrin clot permeability (Ks), which indicates the average pore size, lysis time (t50 %), platelet reactivity index (PRI) and ADP-induced platelet aggregation (ADP5, 20µM) were evaluated on admission. All patients received aspirin and 45 (56.3 %) 600 mg of clopidogrel, 80 (60-120) min prior to aspiration. Higher content of fibrin (61.6 vs 34.3 %, P< 0.0001) and platelets (8.2 vs 4.8 %, P=0.018) and lower erythrocyte content (15.8 vs 42.9 %, P< 0.0001) were found on ICT surface compared with its inner part. After adjustment for fibrinogen, in both ICT parts fibrin content was correlated with Ks (r≤-0.55, P< 0.0001) and t50 % (r≥ 0.29, P≤ 0.02) but not with PRI and ADP5,20µM. Polyhedrocytes were observed in 16 (20 %) patients and their large amount expressed as ≥ 50 % fields of view covered by polyhedrocytes was associated with the lower PRI values (40 vs 69 %, P=0.015), but not Ks or t50 %. By multivariate regression, Ks (β=-0.62, P< 0.0001), clopidogrel pretreatment (β=-0.36, P< 0.001), ischemia time (β=0.19, P=0.044) and family history (β=0.18, P=0.049) independently predicted fibrin content in the whole ICT (R²=0.65, P< 0.0001). Formation of denser plasma fibrin clots is independently associated with high fibrin content within the ICT in STEMI.

Metabolic syndrome, platelet activation and the development of transient ischemic attack or thromboembolic stroke

Stroke is the second most common cause of mortality in the world today, where transient ischemic attack (TIA) is a period of focal ischemia, the symptoms of which resemble a thromboembolic stroke. Contrary to stroke, TIA symptoms typically last less than one hour and necrosis is absent. Stroke is often preceded by TIA, making it an important predictor of future ischemic events. The causal role of atherosclerosis in the development of TIA is well established, however, research indicates that the atherosclerotic process begins years earlier with the development of metabolic syndrome, which affects approximately 45% of the adult population worldwide. Metabolic syndrome is present if three or more of the following is present: increased waist circumference, increased triglycerides, decreased HDL, increased fasting glucose and hypertension. This syndrome causes systemic inflammation that activates the coagulation system and may cause the formation of pathological thrombi. The role of platelets in stroke has been studied and platelet activation pathways identified. ADP and thromboxane A(2) are the most common activators of platelets in normal physiology. Several pharmacological treatments have been employed to prevent the activation of platelets, the most common of which include aspirin and P2Y(12)-inhibitors. Although treatment is administered strokes and subsequent TIAs are very common in individuals that suffered an initial event. This indicates that research needs to be done in order to elucidate new therapeutic targets, but also to better treat ischemic events to not only decrease the amount of recurring events but also decrease stroke mortality worldwide.