Blood coagulability and fibrinolysis in streptozotocin-induced diabetic rats

Attenuation of type-1 diabetes-induced cardiovascular dysfunctions by direct thrombin inhibitor in rats: a mechanistic study

Chronic diabetes is associated with ventricular dysfunctions in the absence of hypertension and coronary artery diseases. This condition is termed as diabetic cardiomyopathy (DCM). There is no favourable treatment available for the management of diabetic cardiomyopathy. Recent studies have reported increase in circulating thrombin level among diabetic patients which is responsible for hypercoagulability of blood. Thrombin induces inflammation and fibrosis, and enhances cardiac cell growth and contractility in vitro. In this study, we have investigated the effects of argatroban; a direct thrombin inhibitor against DCM in streptozotocin-induced type-1 diabetes. Diabetes was induced by single dose of streptozotocin (STZ; 50 mg/kg, i.p.) in male Sprague-Dawley rats. After 4 weeks of diabetes induction, the animals were treated with argatroban (0.3 and 1 mg/kg, i.p. daily) for the next 4 weeks. The effect of argatroban was evaluated against diabetes-associated cardiac dysfunction, structural alteration and protein expression. STZ-induced diabetic rats exhibited significant decline in left ventricular functions. Four weeks of treatments with argatroban significantly improved ventricular functions without affecting heart rate. Further, it also protected heart against structural changes induced by diabetes as shown by reduction in fibrosis, hypertrophy and apoptosis. The improvement in cardiac functions and structural changes was associated with significant reduction in left ventricular expression of thrombin receptor also termed as protease-activated receptor-1 or PAR1, p-AKT (ser-473), p-50 NFκB and caspase-3 proteins. This study demonstrates beneficial effects of argatroban via improvement in cardiac functions and structural changes in STZ-induced DCM. These effects may be attributed through reduction in cardiac inflammation, fibrosis and apoptosis.

Plasma lipids affect dabigatran etexilate anticoagulation in rats with unbalanced diabetes mellitus

BACKGROUND

Dabigatran etexilate (DE) has similar stroke prevention efficacy in patients with and without diabetes mellitus (DM). However, the benefit of reducing major bleeding was not seen in diabetics. Thus, this study investigated anticoagulant responses to DE and the biological predictors of this response in a DM model.

METHODS

Experiments were performed in six control (C), eight DE-treated control (CD), five diabetic (D), and eight DE-treated diabetic (DD) rats. Dabigatran etexilate (50 mg/kg/day) was administered in chow for 12 weeks. At the end of the study, plasma glucose, triglycerides, total cholesterol (TC), high-density lipoprotein cholesterol, low-density lipoprotein cholesterol (LDL-C), and plasma creatinine were measured. Correlations were ascertained with the diluted thrombin time (dTT).

RESULTS

When corrected for similar DE intake, dTT was significantly higher in DD than CD rats (P < 0.001). There was a significant negative correlation between creatinine clearance (CCr) and dTT (r = -0.91, P < 0.01) in DD rats. In addition, dTT was positively correlated with TC (r = 0.96, P < 0.01), LDL-C (r = 0.75, P = 0.04), and glucose (r = 0.83, P = 0.02). In multiple regression analysis, CCr (r = -0.81, P = 0.01), TC (r = 0.93, P < 0.001), and LDL-C (r = 0.74, P < 0.01) remained the only independent predictors of dTT.

CONCLUSIONS

The results show a significantly more intense DE-induced anticoagulation in diabetic rats that does not seem to be solely related to altered kidney function, and demonstrate that plasma cholesterol can significantly affect DE anticoagulation in this setting.

N-acetylcysteine attenuates systemic platelet activation and cerebral vessel thrombosis in diabetes

Objective

We previously demonstrated that diabetes exacerbates stroke-induced brain injury, and that this correlates with brain methylglyoxal (MG)-to-glutathione (GSH) status. Cerebral injury was reversed by N-acetylcysteine (NAC). Here we tested if the pro-thrombotic phenotype seen in the systemic circulation and brain during diabetes was associated with increased MG-glycation of proteins, and if NAC could reverse this.

Methods

The streptozotocin (STZ)-induced mouse model of type 1 diabetes was used. Thrombus formation in venules and arterioles (pial circulation) was determined by intravital videomicroscopy using the light-dye method. Circulating blood platelet-leukocyte aggregates (PLAs) were analyzed by flow cytometry 1 wk before other measurements. GSH and MG levels in platelets were measured by HPLC. MG-modified proteins, glutathione peroxidase-1 (GPx-1), and superoxide dismutase-1 (SOD1) levels were detected in platelets by western blot at 20 weeks. Proteins involved in coagulation were quantified by ELISA. NAC (2 mM) was given in drinking water for 3 weeks before the terminal experiment.

Results

Thrombus development was accelerated by diabetes in a time-dependent manner. % PLAs were significantly elevated by diabetes. Plasma activated plasminogen activator inhibitor type 1 levels were progressively increased with diabetes duration, with tail bleeding time reduced by 20 wks diabetes. Diabetes lowered platelet GSH levels, GPx-1 and SOD-1 expression. This was associated with higher MG levels, and increased MG-adduct formation in platelets. NAC treatment partly or completely reversed the effects of diabetes.

Conclusion

Collectively, these results show that the diabetic blood and brain become progressively more susceptible to platelet activation and thrombosis. NAC, given after the establishment of diabetes, may offer protection against the risk for stroke by altering both systemic and vascular prothrombotic responses via enhancing platelet GSH, and GSH-dependent MG elimination, as well as correcting levels of antioxidants such as SOD1 and GPx-1.

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Diabetes elevates dicarbonyl stress leading to enhanced thrombosis in the brain.

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Glutathione levels decrease leading to impaired elimination of methylglyoxal in platelets during diabetes.

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Platelet proteins are glycated and platelets form aggregates with leukocytes in diabetes.

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Diabetes increases circulating levels of plasminogen activator inhibitor-1.

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NAC, via GSH synthesis, reverses the platelet activation, protein glycation and pro-coagulation responses & protects against thrombosis in the diabetic brain.

Combination approaches to attenuate hemorrhagic transformation after tPA thrombolytic therapy in patients with poststroke hyperglycemia/diabetes

To date, tissue type plasminogen activator (tPA)-based thrombolytic stroke therapy is the only FDA-approved treatment for achieving vascular reperfusion and clinical benefit, but this agent is given to only about 5% of stroke patients in the USA. This may be related, in part, to the elevated risk of symptomatic intracranial hemorrhage, and consequently limited therapeutic time window. Clinical investigations demonstrate that poststroke hyperglycemia is one of the most important risk factors that cause intracerebral hemorrhage and worsen neurological outcomes. There is a knowledge gap in understanding the underlying molecular mechanisms, and lack of effective therapeutics targeting the severe complication. This short review summarizes clinical observations and experimental investigations in preclinical stroke models of the field. The data strongly suggest that interactions of multiple pathogenic factors including hyperglycemia-mediated vascular oxidative stress and inflammation, ischemic insult, and tPA neurovascular toxicity in concert contribute to the BBB damage-intracerebral hemorrhagic transformation process. Development of combination approaches targeting the multiple pathological cascades may help to attenuate the hemorrhagic complication.

Enhancement of the coagulation system in spontaneously hypertensive and hyperlipidemic rats

As a risk factor for cardiovascular and cerebrovascular disease, hypertension and hyperlipidemia are believed to provoke vascular damage leading to a hypercoagulative state. The aim of the present study was to investigate the coagulative and fibrinolytic activity and hepatic mRNA expression of the coagulative factors in spontaneously hypertensive and hyperlipidemic female rats (SHHR:>150 mmHg of systolic blood pressure, >150 mg/dl of plasma cholesterol). Plasma levels of fibrinogen, thrombin-antithrombin III (ATIII) complexes and ATIII in the SHHR at 9 months of age increased significantly compared with those of age-matched Sprague-Dawley rats (SD). In the SHHR, the hepatic mRNA expression of the alpha- and beta-chains, but not the gamma-chain of fibrinogen and prothrombin was significantly enhanced. Therefore, the hyperfibrinogenemia in the SHHR was demonstrated to be due to the increase in hepatic mRNA expression of alpha- and beta-chains of fibrinogen. The pathological findings of the aortic arch from the 9-month old SHHR were cytoplasmic vacuolization and intimal thickening in the endothelium. These results suggest that hypercoagulation concomitant with the increase in hepatic mRNA expression of fibrinogen components may contribute to the development of atherosclerosis in the SHHR.

Coagulation and fibrinolysis parameters in type 2 diabetic patients with and without diabetic vascular complications

OBJECTIVES

To investigate the markers of endogenous coagulation/fibrinolysis and vascular endothelial cell function, and to assess the relationships between hemostatic parameters and diabetic vascular complications in type 2 diabetic patients.

MATERIALS AND METHODS

Coagulation and fibrinolysis parameters were measured in 92 type 2 diabetic patients (43 male, 49 female, mean age 50.1 +/- 13.4 years) with (n = 44) and without (n = 48) vascular diabetic complications, and in 40 nondiabetic healthy subjects (20 male, 20 female, mean age 49.8 +/- 15.1 years). Common lipid parameters were also measured.

RESULTS

The plasma levels of fibrinogen, antithrombin III (AT III), plasminogen activator inhibitor-1 (PAI-1), von Willebrand factor (vWF) activity and prothrombin time were found to be significantly increased in the type 2 diabetic patients compared with the healthy subjects. Glycosylated hemoglobin lc was inversely correlated with plasma protein S and activated prothrombin time. Protein C and S activities were positively correlated with plasma vWF activity, and were negatively correlated with plasma t-PA levels. vWF activity was negatively correlated with plasma t-PA levels. AT III levels were positively correlated with plasma total cholesterol levels, plasma low density lipoprotein cholesterol levels, plasma triglycerides and D-dimer levels. Plasma PAI-1 levels and factor V activity in diabetic patients with microvascular complications were significantly higher than those of the diabetic patients without microvascular complications. The plasma PAI-1 and platelet count were increased in patients with diabetic retinopathy compared with the diabetic patients without retinopathy. Plasma PAI-1 levels and factor VII activity were significantly higher in the diabetic patients with nephropathy than in diabetic patients without nephropathy. Plasma concentrations of fibrinogen and PAI-1 were significantly higher in the diabetic patients with neuropathy than the diabetic patients without neuropathy.

CONCLUSIONS

The data demonstrated that patients with type 2 diabetes mellitus had a hypercoagulable state and hypofibrinolysis, thereby indicating that activation of coagulation with a reduced fibrinolytic activity may contribute to the increased risk of vascular disease in type 2 diabetic patients.

Age-related changes in coagulation, fibrinolysis, and platelet aggregation in male WBN/Kob rats

We investigated the age-related changes in blood coagulation, fibrinolysis, and platelet aggregation in male WBN/Kob rats, animals that exhibit spontaneously diabetes mellitus at more than 6 months of age. The rats aged 6 months or more showed significant hyperglycemia, hypoinsulinemia, and hyperlipidemia. As changes in coagulation parameters, the data indicated significant increases in factors II, V, VII, VIII, IX, X, and XII activities; a significant decrease in antithrombin III activity in rats more than 6 months of age; significant increases in fibrinogen level and factor XI activity; and significant decreases in prothrombin time and activated partial thromboplastin time in those more than 9 months of age. As changes in fibrinolytic parameters, the animals showed significant decreases in plasminogen and tissue-type plasminogen activator, and significant increases in alpha2-plasmin inhibitor and plasminogen activator inhibitor at more than 6 months of age. In addition, there were significant correlations between the plasma levels of coagulation/fibrinolytic markers and the 4-hour fasting glucose or lipids. Furthermore, they displayed significant increases in ADP- or collagen-induced platelet aggregation and in cholesterol/phospholipid molar ratio in platelets at more than 9 months of age. The increase in cholesterol/phospholipid ratio may be responsible for hyperaggregation of platelets in diabetic animals. These findings suggest that WBN/Kob rats are suitable for research on blood coagulation abnormalities in diabetes. However, further studies are needed to clarify the details of the mechanisms involved.

Ultrastructural changes and immunohistochemical localization of nitric oxide synthase, advanced glycation end products and NF-kappa B in aorta of streptozotocin treated Mongolian gerbils

To evaluate the relationship among the induction of nitric oxide synthase (NOS), advanced glycation end products (AGEs) and NF-kappa B for vascular damage in hyperglycemia, we injected Mongolian gerbils intravenously with 150 mg/kg streptozotocin (STZ) and observed over the next one year the resulting aortic changes by immunohistochemical and electron microscopical techniques. After STZ treatment, hyperglycemia was confirmed and body weight transiently decreased. Morphological observation revealed no remarkable changs in vascular endothelial cells or vascular smooth muscle cells in the aorta at one week after STZ administration. After 4 weeks increased collagen fibrils were observed in the pericellular spaces of media. At one year after STZ administration, increased collagen fibrils and thickened elastic fibers were found around the vascular smooth muscle cells with vacuolization and increased cytoplasmic organellae compared with non-treated animals of the same age. Immunohistochemically endothelial constitutive NOS (ecNOS) was localized in the endothelium of the aorta of Mongolian gerbils. At one year after STZ administration, the reaction products of iNOS, AGEs and NF-kappa B in vascular endothelial cells and smooth muscle cells were much more greatly increased than at one week and 4 weeks. After STZ administration, the localization of NOS, AGEs and NF-kappa B was observed in the aorta, which suggests these factors play important roles in the pathogenesis of vasculopathy in diabetes mellitus.