thromboxane-b2 and Diabetic-Angiopathies

Excessive oxidative stress due to hyperglycemia and glycoxidation leads to an increased production of F2-isoprostanes, one of which, 8-iso-PGF2 alpha, reaches high concentrations in plasma and urine in both insulin-dependent and non-insulin-dependent diabetics. This is associated with an increase in platelet activation, reflected by an increased urinary excretion of platelet-derived TxB2. Improved metabolic control or vitamin E supplementation reduces urinary 8-iso-PGF2 alpha and TxB2, whereas aspirin or indobufen reduces TxB2 but not 8-iso-PGF2 alpha. Since TxB2 in the urine seems to represent the common link between diabetes (as well as other risk factors) and the thrombotic complications of vascular disease, platelet activation due to lipid-glycoxidation is an important aspect in the pathogenesis of vascular complications of diabetes mellitus. Among the various plasma coagulation and fibrinolysis factors that are found to be altered in diabetes, the increased level of plasminogen activator inhibitor (PAI-1) in the plasma and in the vessel wall is of the utmost importance. Indeed, it is suspected that the atherosclerotic plaques formed in the presence of high concentrations of PAI-1 are more prone to rupture and ensuing thrombosis. The thrombosis-oriented modifications of blood platelets, coagulation and fibrinolysis are an important cause behind the high prevalence of vascular events in diabetes.

Topics: Blood Coagulation Factors; Cardiovascular Diseases; Diabetes Complications; Diabetes Mellitus; Diabetes Mellitus, Type 1; Diabetes Mellitus, Type 2; Diabetic Angiopathies; Fibrinolysis; Glycosylation; Humans; Oxidative Stress; Plasminogen Activator Inhibitor 1; Platelet Activation; Risk Factors; Thrombosis; Thromboxane B2

Although many data regarding the biosynthesis of thromboxane A2 and prostacyclin in diabetes mellitus have recently appeared in the literature, it is not clear whether an imbalance between the generation of the two prostaglandins might be connected to the vascular complications of diabetes. In the present review we have tried to emphasize the most significant aspects of these studies and we have focused on alterations of platelet prostacyclin receptors and on the effects of circulating immune complexes on platelets of diabetics. It is likely that studies on the release of platelet derived growth factor as well as more precise definitions of its action on vessel wall cells leading to a massive release of prostacyclin, will permit us to ascertain whether an alteration in prostaglandin ratio is linked to the genesis of the vascular complications in diabetics.

Topics: 6-Ketoprostaglandin F1 alpha; Animals; Antigen-Antibody Complex; Blood Platelets; Blood Vessels; Cyclic AMP; Diabetes Mellitus, Experimental; Diabetic Angiopathies; Endothelium; Epoprostenol; Humans; Models, Biological; Platelet Aggregation; Platelet-Derived Growth Factor; Receptors, Cell Surface; Receptors, Epoprostenol; Receptors, Platelet-Derived Growth Factor; Receptors, Prostaglandin; Thromboxane A2; Thromboxane B2

Patients with type 2 diabetes mellitus (T2DM) have reduced aspirin-induced pharmacodynamic effects. This may be attributed to increased platelet turnover rates resulting in an increased proportion of non-aspirin-inhibited platelets during the daily dosing interval. The hypothesis of this study was that an increase in the frequency of drug administration [twice daily (bid) versus once daily (od)] may provide more effective platelet inhibition in T2DM patients.. T2DM patients with stable coronary artery disease were prospectively recruited. Patients modified their aspirin regimen on a weekly basis according to the following scheme: 81 mg/od, 81 mg/bid, 162 mg/od, 162 mg/bid, and 325 mg/od. Pharmacodynamic assessments included light-transmittance aggregometry after arachidonic acid, collagen and adenosine diphosphate stimuli; VerifyNow-Aspirin assay; and serum thromboxane B(2) (TXB(2)) levels. Twenty patients were analyzed. All patients were sensitive and compliant to aspirin irrespective of dose, as assessed by arachidonic acid-induced aggregation. When aspirin was administered once daily, there was no significant effect on platelet reactivity by increasing the once-daily dosing using aspirin-sensitive assays (collagen-induced aggregation and VerifyNow-Aspirin). An increase in aspirin dose by means of a second daily administration was associated with a significant reduction in platelet reactivity assessed by collagen-induced aggregation and VerifyNow-Aspirin between 81 mg/od and 81 mg/bid (P<0.05 for both assays) and between 81 mg/od and 162 mg/bid (P<0.05 for both assays). There was no impact of aspirin dosing regimens on adenosine diphosphate-induced aggregation. A dose-dependent effect of aspirin was observed on serum TXB(2) levels (P=0.003).. Aspirin dosing regimens are associated with different pharmacodynamic effects in platelets from T2DM patients and stable coronary artery disease, with a twice-daily, low-dose aspirin administration resulting in greater platelet inhibition than once-daily administration as assessed by aspirin-sensitive assays and a dose-dependent effect on serum TXB(2) levels. The clinical implications of a modified aspirin regimen tailored to T2DM patients warrant further investigation.. URL: http://www.clinicaltrials.gov. Unique identifier: NCT01201785.

Topics: Aged; Aspirin; Coronary Artery Disease; Diabetes Mellitus, Type 2; Diabetic Angiopathies; Dose-Response Relationship, Drug; Drug Administration Schedule; Female; Humans; Male; Middle Aged; Platelet Aggregation; Platelet Aggregation Inhibitors; Prospective Studies; Thromboxane B2

The efficacy of low-dose aspirin in type 2 diabetes mellitus (T2DM) has been questioned. We tested if twice daily dosing of aspirin would be more effective in T2DM, possibly due to increased platelet turnover. A randomised cross-over study compared 75 mg aspirin OD, 75 mg BID and 320 mg OD (≥ 2 week treatment periods) in 25 patients with T2DM and micro- or macrovascular complications. Platelet responses were examined by impedance aggregometry (WBA) and the IMPACT-R aspirin test in whole blood, light transmittance aggregometry in platelet-rich plasma (LTA), and urinary 11-dehydro-thromboxane B2 (TxM). Aspirin 75 mg BID decreased arachidonic acid (AA)-induced WBA compared to 75 mg OD (9.7 ± 4.5 vs. 12.6 ± 3.5 ohm; p = 0.003) or to 320 mg OD (11.5 ± 4.2 Ohms; p = 0.049). WBA responses to collagen were similarly attenuated by BID or high dosing (by 12-14%; p = 0.02 for both). The IMPACT-R showed a better response to 75 mg BID compared to 75 mg OD (p = 0.049), but not to 320 mg OD. AA-induced aggregation by LTA was <6.5% on all occasions, with no differences between aspirin dosages. TxM was reduced after 320 mg OD (p = 0.002), but not 75 mg BID (p = 0.07). Reticulated platelets were highly correlated with mean platelet volume (MPV; r2 = 0.74, p<0.0001). Both markers for platelet turnover were correlated with AA-induced WBA, but neither identified patients who benefited from BID dosing dependably. In conclusion, twice daily dosing improved laboratory responses to aspirin in high risk T2DM patients. Studies of whether BID dosing of aspirin can improve clinical outcomes in such patients are of interest.

Topics: Aspirin; Blood Platelets; Cells, Cultured; Clinical Protocols; Diabetes Mellitus, Type 2; Diabetic Angiopathies; Drug Dosage Calculations; Humans; Microvessels; Platelet Aggregation; Platelet Aggregation Inhibitors; Thromboxane B2

Diabetic patients may have a higher prevalence of platelet aspirin resistance than nondiabetic patients. Our goal was to analyze platelet aspirin responsiveness to various aspirin doses in diabetic and nondiabetic patients.. We examined the effect of aspirin (81, 162, and 325 mg/day for 4 weeks each) on platelet aspirin responsiveness in 120 stable outpatients (30 diabetic patients and 90 nondiabetic patients) with coronary artery disease (CAD) using light transmittance aggregometry (LTA), VerifyNow, platelet function analyzer (PFA)-100, and levels of urinary 11-dehydro-thromboxane B(2) (11-dh-TxB(2)).. In the total group, a low prevalence (0-2%) of aspirin resistance was observed with all aspirin doses as determined by arachidonic acid-induced LTA. Aspirin resistance was higher at the 81-mg dose in diabetic versus nondiabetic patients using collagen-induced LTA (27 vs. 4%, P = 0.001), VerifyNow (13 vs. 3%, P = 0.05), and urinary 11-dh-TxB(2) (37 vs. 17%, P = 0.03). Diabetic patients treated with 81 mg exhibited higher platelet function measured by VerifyNow, collagen- and ADP-induced LTA, and 11-dh-TxB(2) levels (P

Topics: Aged; Aspirin; Blood Platelets; Coronary Disease; Cross-Over Studies; Diabetic Angiopathies; Double-Blind Method; Drug Resistance; Female; Humans; Male; Middle Aged; Platelet Aggregation; Platelet Aggregation Inhibitors; Reference Values; Thromboxane B2

We studied 27 non-insulin-dependent diabetics without apparent atherosclerosis (AS) to investigate whether abnormal platelet function is related to asymptomatic atherosclerosis in diabetes mellitus. The degree of AS was quantitatively evaluated by determining the intimal plus medial thickness (IMT) of the carotid artery wall with ultrasound high-resolution B-mode imaging. Based on our previous finding that the upper threshold of the IMT was 1.1 mm in healthy subjects, the patients were divided into the AS-positive group with the IMT > 1.1 mm, (n = 17) and the AS-negative group with the IMT < 1.1 mm (n = 10). Among five variables measured as the factors concerned with thrombogenesis, only plasma levels of beta-thromboglobulin (beta-TG) and platelet factor 4 (PF4) were significantly higher in the AS-positive group than in the AS-negative group. Chronic administration of pentoxifylline (300 mg/day) significantly reduced the abnormally high plasma levels of beta-TG and PF4 in 7 patients of the AS-positive group to normal levels, without lowering the normal plasma beta-TG and PF4 levels in the remaining 10 patients. Pentoxifylline treatment did not affect the plasma levels of the 3 other variables, von Willebrand factor, 6-keto prostaglandin F1 alpha and thromboxane B2. This study suggests that the progress of atherosclerosis in diabetes mellitus is associated with in vivo platelet activation and platelet activation does not occur in diabetics without carotid atherosclerosis. Pentoxifylline may impede the vicious cycle in which atherosclerosis is accelerated by platelet activation.

Topics: Aged; Arteriosclerosis; beta-Thromboglobulin; Blood Pressure; Carotid Arteries; Carotid Artery Diseases; Cholesterol; Cholesterol, HDL; Diabetes Mellitus, Type 2; Diabetic Angiopathies; Female; Glycated Hemoglobin; Humans; Male; Middle Aged; Pentoxifylline; Platelet Activation; Platelet Factor 4; Prostaglandins F; Thromboxane B2; Triglycerides; Ultrasonography; von Willebrand Factor

The aim of this study was to evaluate the effects of a fish oil preparation (MaxEPA) on hemostatic function and fasting lipid and glucose levels in non-insulin-dependent diabetic (NIDDM) subjects. Eighty NIDDM outpatients aged 55.9 yr (mean SD 11.5 yr) participated in a prospective double-blind placebo-controlled study of MaxEPA capsules (10 g/day) or olive oil (control) treatment over 6 wk. Patients received either MaxEPA or olive oil in addition to preexisting therapy. Metabolic and hemostatic variables were measured before treatment and after 3 and 6 wk. Platelet membrane eicosapentaenoic acid (EPA) content increased in the treatment group (P less than 0.001). MaxEPA supplementation was associated with a significant fall in total triglycerides (P less than 0.001) but did not affect total cholesterol (P = 0.7) compared with control treatment. Fasting plasma glucose increased after 3 wk (P = 0.01) but not after 6 wk (P = 0.17) treatment with MaxEPA. Spontaneous platelet aggregation in whole blood fell in the MaxEPA group (P less than 0.02) after 6 wk, but there were no changes in agonist-induced platelet aggregation, thromboxane generation in platelet-rich plasma, or plasma beta-thromboglobulin and platelet factor IV levels. An increase in clotting factor VII (P = 0.02), without changes in fibrinogen or factor X levels, occurred in the MaxEPA group. Similar reductions in blood pressure were observed in both groups. Dietary supplementation with MaxEPA capsules (10 g/day) in NIDDM subjects is associated with improvement in hypertriglyceridemia but with deleterious effects in factor VII and blood glucose levels. Most indices of platelet function are unaffected by this therapy.

Topics: Blood Glucose; Cardiovascular Diseases; Cholesterol; Diabetes Mellitus, Type 2; Diabetic Angiopathies; Diet, Diabetic; Docosahexaenoic Acids; Drug Combinations; Eicosapentaenoic Acid; Fatty Acids, Omega-3; Female; Fish Oils; Food, Fortified; Hemostasis; Humans; Lipids; Male; Thromboxane B2; Triglycerides

Recent studies indicate that not all diabetic subjects benefit from aspirin therapy. Our objective is to characterize diabetic subjects with aspirin resistance using urine thromboxane, and VerifyNow measures. Our results suggest that cardiovascular disease, microalbuminuria, poor diabetes control, and increased waist circumference help identify aspirin resistance in diabetes.

Topics: Albuminuria; Aspirin; Cohort Studies; Diabetic Angiopathies; Drug Resistance; Female; Glycated Hemoglobin; Humans; Insulin Resistance; Male; Middle Aged; Nephelometry and Turbidimetry; Platelet Aggregation; Platelet Aggregation Inhibitors; Thromboxane B2; Waist Circumference

To investigate the relationship between syndrome differentiation of traditional Chinese medicine (TCM) and characteristic changes of vascular endothelial function in patients with diabetic arterial occlusion (DAO) of lower extremities.. Forty patients with DAO were selected as trial group. Twenty patients among them were attributed to blood stasis syndrome (group A1), and the others were attributed to syndrome of pathogenic dampness-heat attacking the lower limb (group A2) according to syndrome differentiation type of TCM. Patients with diabetes (group B), arteriosclerosis obliterans (group C) and healthy people (group D) were observed as the control groups, respectively. There were 20 cases in each group. Endothelium-dependent dilation (EDD) and endothelium-independent dilation (EID) were measured by high resolution ultrasound in the 100 subjects and the changes of vascular tension factors were also studied.. The results showed that EDD in group A was reduced significantly as compared with that in the groups B, C and D. The levels of vascular contractile factors such as endothelin-1 (ET-1) and thromboxane B2 (TXB2) in group A were higher than those in the groups B, C and D, while the levels of vascular dilatory factors such as nitric oxide (NO) and 6-keto-prostaglandin F1alpha(6-Keto-PGF1alpha) were declined significantly as compared with those in the groups B and D. Linear correlation analysis showed that EDD was correlated positively with the levels of NO and 6-Keto-PGF1alpha, while the levels of ET-1 and TXB2 had negative correlation with EDD. EDD and EID in group A2 were declined significantly as compared with those in group A1.. Our findings indicate that endothelial dysfunction may play an important role in the pathogenesis of DAO and may be associated with syndrome differentiation of TCM.

Topics: 6-Ketoprostaglandin F1 alpha; Aged; Arterial Occlusive Diseases; Diabetes Mellitus, Type 2; Diabetic Angiopathies; Diagnosis, Differential; Endothelin-1; Endothelium, Vascular; Female; Humans; Lower Extremity; Male; Medicine, Chinese Traditional; Middle Aged; Nitric Oxide; Thromboxane B2

Vascular complications are the leading causes of morbidity and mortality in diabetic patients. The contribution of platelets to thromboembolic complications is well documented, but their involvement in the initiation of the atherosclerotic process is of rising interest. Thus, the aim of the present study was to evaluate basal arachidonic acid metabolism in relation to the redox status of platelets in both type 1 and type 2 diabetic patients, in the absence of vascular complications, as compared with respective control subjects. For the first time, we show that basal thromboxane B(2), the stable catabolite of thromboxane A(2), significantly increased in resting platelets from both type 1 and type 2 diabetic patients (58 and 88%, respectively), whereas platelet malondialdehyde level was only higher in platelets from type 2 diabetic subjects (67%). On the other hand, both vitamin E levels and cytosolic glutathione peroxidase activities were significantly lower in platelets from diabetic patients as compared with respective control subjects. We conclude that platelet hyperactivation was detectable in well-controlled diabetic patients without complications. This abnormality was associated with increased oxidative stress and impaired antioxidant defense in particular in type 2 diabetic patients. These alterations contribute to the increased risk for occurrence of vascular diseases in such patients.

Topics: alpha-Tocopherol; Antioxidants; Blood Glucose; Cholesterol; Cholesterol, HDL; Cholesterol, LDL; Diabetes Mellitus, Type 1; Diabetes Mellitus, Type 2; Diabetic Angiopathies; Glutathione Peroxidase; Glycated Hemoglobin; Humans; Lipid Peroxidation; Lipoxygenase; Middle Aged; Platelet Activation; Platelet Aggregation; Prostaglandin-Endoperoxide Synthases; Reference Values; Thromboxane B2; Triglycerides

Topics: Aspirin; Blood Platelets; Diabetic Angiopathies; Drug Resistance; Humans; Platelet Aggregation; Thromboxane B2

To study the change of vascular tension factors (VTF), including vascular contractile factors as endothelin-1 (ET-1), thromboxane A2 (TXA2) and vascular dilatory factors as nitric oxide (NO), prostacyclin (PGI2), in different stage of peripheral diabetic arterial occlusion (PDAO), and to preliminarily explore the clinical significance of these changes.. VTF in 40 diabetic patients, 15 of 2nd stage and 25 of 3rd stage, were observed by measuring level of ET-1, NO, TXB2 and 6-keto-PGF1alpha in blood plasma with RIA assay.. (1) ET-1 and TXB2 levels in all patients were higher than those in control (P < 0.05 and P < 0.01), those in patients of 3rd stage was higher than those of 2nd stage, showing significant difference (P < 0.05). (2) NO and 6-keto-PGF1alpha levels in all patients was lower than those in control, but showed no significant difference between patients of various stages (P > 0.05).. There are changes of VTF in patients with PDAO, manifesting as increase of vascular contractive factors and decrease of vascular dilative factor. The changes are diffrent in various stages, the vascular contractive and thrombotic factors in patients of 3rd stage are higher than those in patients of 2nd stage, but the injury on vascular dilative factors in the two stages showed insignificant difference.

Topics: 6-Ketoprostaglandin F1 alpha; Aged; Aged, 80 and over; Diabetes Mellitus, Type 2; Diabetic Angiopathies; Endothelin-1; Epoprostenol; Female; Humans; Lower Extremity; Male; Middle Aged; Nitric Oxide; Thromboxane A2; Thromboxane B2; Vasomotor System

Thromboxane B2, a stable metabolite of thromboxane A2, was studied in type 2 diabetic patients to evaluate the role played by prostaglandins in the onset of vascular complications.. The study was carried out in 30 subjects, 20 of whom were diabetics and 10 controls. Thromboxane B2 was assayed using the "Biotrak Thromboxane B2" kit.. In the first group of control subjects, the mean value of TXB2 was 6.39 +/- 0.89 pg/ml; in the second group, including diabetic patients without vascular complications, TXB2 levels were 8.89 +/- 1.51; in the third, consisting of diabetic patients with microangiopathy, the mean level was 46.28 +/- 6.82; in the fourth, including patients with micro- and macroangiopathy, the mean level was 98.78 +/- 17.15; the fifth group, with a mean value of 41.00 +/- 9.86, included diabetic patients with cerebral vasculopathy. Thromboxane B2 was correlated with glycemia but the results were not statistically significant (r = 0.28; p < 0.05). The correlation with the years since onset of diabetes was positive and statistically significant (r = 0.49; p < 0.05).. In conclusion, the authors emphasise that TXB2 is present in the circulation in diabetes in steadily increasing quantities over time since the onset of diabetes, leading to chronic vasoconstriction which in turn leads to a deterioration of vascular lesions in the districts where hypoglycemia has already caused the activation of neurotransmitter hormones with consequent slowing down of the blood flow and progressive tissue hypoxia.

Topics: Age of Onset; Blood Glucose; Cerebrovascular Disorders; Diabetes Mellitus, Type 2; Diabetic Angiopathies; Humans; Middle Aged; Prostaglandins; Thromboxane A2; Thromboxane B2; Vasoconstriction

We analyzed the in vitro effects of sorbitol and fructose on platelet function. Sorbitol and fructose increased platelet aggregation induced with adenosine diphosphate (ADP) or collagen in whole blood, but had no effect in platelet-rich plasma. The concentration that increased basal aggregation by 50% with ADP as the inducer was 12.89 +/- 1.55 mmol/L for fructose, and 18.99 +/- 2.01 mmol/L for sorbitol. When collagen was the inducer, these concentrations were 15.02 +/- 0.98 mmol/L for fructose, and 12.94 +/- 1.57 mmol/L for sorbitol. Both sugars increased, in a concentration-dependent way, the proaggregatory effect of erythrocytes, and erythrocyte uptake of adenosine. Time to uptake of 50% adenosine was 2.1 +/- 0.3 min in control samples, 0.14 +/- 0.01 min in the presence of fructose, and 0.23 +/- 0.03 min with sorbitol. Both sugars reduced vascular prostacyclin synthesis, with 50% inhibitory concentrations of 26.48 +/- 1.97 mmol/L for fructose, and 39.53 +/- 2.81 mmol/L for sorbitol. Both sugars also increased arterial lipid peroxidation by 30% (sorbitol) and 23% (fructose). We conclude that these two sugars enhance platelet function and disrupt the thromboxane/prostacyclin ratio.

Topics: 6-Ketoprostaglandin F1 alpha; Adenosine; Adenosine Diphosphate; Adult; Animals; Aorta; Blood Glucose; Blood Platelets; Collagen; Diabetic Angiopathies; Epoprostenol; Erythrocytes; Fructose; Humans; Hyperglycemia; In Vitro Techniques; Lipid Peroxidation; Male; Platelet Activation; Platelet Aggregation; Rats; Rats, Wistar; Sorbitol; Thromboxane B2

Using fura-2, a fluorescence indicator, we evaluated the changes of platelet cytosolic free calcium concentration ([Ca2+]i) and its role in regulation of thromboxane B2 (TXB2) synthesis in patients with diabetes mellitus (DM group, n = 27) and in healthy subjects (control group, n = 15). The A23187-evoked elevation of [Ca2+]i and TXB2 production were higher in the DM group than in the control group (P < 0.01 respectively). The rise in [Ca2+]i was correlated positively with TXB2 production. In contrast, stimulation with arachidonic acid, TXB2 production was unaltered between the groups, although arachidonate-induced [Ca2+]i was higher in the DM group than in the control group (P < 0.05). The results suggested that changes in platelets [Ca2+]i in diabetic subjects may contribute to increase in TXB2 synthesis, involved libration of free arachidonate from membrance phospholipids by the action of phospholipases. Since no significant difference was found between the diabetic patients with microangiopathy (n = 13) and without microangiopathy (n = 14), the results above may be involved in the development of diabetic microangiopathy.

Topics: Biological Transport, Active; Blood Platelets; Calcium; Diabetes Mellitus; Diabetic Angiopathies; Female; Humans; Male; Thromboxane B2

We studied the effects of glycated lipoproteins of low- and high-density (LDL and HDL) on platelets and vascular endothelial cells. After pretreatment for 5 minutes at 37 degrees C, the thrombin-induced synthesis of thromboxane B2 in washed platelets was significantly increased by glycated LDL as compared with native LDL (198.9 +/- 16.2 vs 90.3 +/- 29.4 ng/10(9) platelets, n = 8, p less than 0.01). Platelet aggregation was also increased by glycated LDL as compared with native LDL. After treatment with platelet-rich plasma for 5 hours at 37 degrees C, these values were suppressed by native HDL vs the control (buffer), but not by glycated HDL. Abnormalities in the release of 6-keto prostaglandin F1 alpha and lactate dehydrogenase from vascular endothelial cells were also induced by glycated LDL and/or HDL. These observations suggest that abnormalities induced in platelets and vascular endothelial cells by glycated lipoproteins may play an important role in the development of atherosclerosis in patients with diabetes mellitus.

Topics: 6-Ketoprostaglandin F1 alpha; Adult; Blood Platelets; Diabetic Angiopathies; Dinoprostone; Endothelium, Vascular; Female; Glycation End Products, Advanced; Glycosylation; Humans; In Vitro Techniques; Lipoproteins, HDL; Lipoproteins, LDL; Male; Platelet Aggregation; Thromboxane B2

To investigate the possible relevance of free radicals and prostanoids to the mode of initiation and/or evolution of microangiopathy in diabetes mellitus, we measured serum lipid peroxides (LPO), an accepted index of intravascular free radicals, and plasma 11-dehydrothromboxane B2 (11-dehydro-TXB2), a stable metabolite of vasoactive thromboxane A2 released from platelets, in 95 patients with normolipidemic type 2 (non-insulin-dependent) diabetes mellitus at different stages of the disease. In general, either LPO or 11-dehydro-TXB2 was significantly greater in the patients, as a group, than in the matched controls (3.82 vs. 2.65 nmol/ml, P < 0.01 for LPO; and 17.3 vs. 5.8 pg/ml, P < 0.01 for 11-dehydro-TXB2). In patients, both LPO and 11-dehydro-TXB2 increased according to the severity of their diabetic retinopathy. A highly significant positive correlation existed between the LPO values and 11-dehydro-TXB2 in the patients (r = 0.64, P < 0.0001), while there was no such relationship in the controls (r = 0.18, P = NS). No difference in serum levels of apolipoproteins A-I, A-II, B, C-II, C-III, or E was observed between the patients and controls. Short-term glycemic control (25 cal/kg of standardized body weight/day, for 8 weeks) resulted in a small but significant reduction in LPO (4.2 vs. 4.6 nmol/ml, control; P < 0.05) without alteration in 11-dehydro-TXB2. There was a tendency towards deterioration in LPO according to the improvement in glycemic control. These results appear consistent with the view that, in addition to LPO, the release of TXA2 from activated platelet in the human circulation could be an important factor for the initiation and/or evolution of microangiopathy in diabetic patients even when they are not apparently hyperlipidemic. Further, the results of the present study emphasize the notion that more tight control of serum lipids is worthy of serious consideration in preventing the advance of diabetic microangiopathy.

Topics: Aged; Apolipoproteins; Biomarkers; Blood Glucose; Cholesterol; Cholesterol, HDL; Diabetes Mellitus, Type 2; Diabetic Angiopathies; Diabetic Nephropathies; Diabetic Retinopathy; Female; Free Radicals; Glycated Hemoglobin; Humans; Lipid Peroxidation; Lipid Peroxides; Male; Middle Aged; Reference Values; Thromboxane B2; Triglycerides

Increased free radical activity may contribute to thrombosis via effects on platelet aggregation and the prostanoid balance. To investigate this further we studied 15 Type 1 diabetic patients with retinopathy, matched with uncomplicated Type 1 patients for age, duration of diabetes and HbA1, together with matched healthy non-diabetic control subjects. The oxidative effects of free radicals as total diene conjugates and lipid peroxides were measured, together with redox status extracellularly as plasma albumin-thiols and intracellularly as erythrocyte superoxide dismutase activity. Platelet count, aggregation of platelets in whole blood to collagen, thromboxane B2, and prostacyclin stimulating factor (PGI2SF) were also assessed. Free radicals measured as lipid peroxides were significantly higher (9.6 (8.1-11.6) mumol l-1 (median and interquartile range) in diabetic patients with retinopathy than in control subjects (8.1 (7.4-9.2) mumol l-1; p less than 0.05). There were also significant reductions in redox status both extracellularly as plasma albumin thiols (408 (383-473) vs 490 (456-517) mumol l-1, p less than 0.001) and intracellularly as erythrocyte superoxide dismutase activity (34 (27-41) vs 44 (36-51) g l-1, p less than 0.05) between patients with retinopathy and control subjects. Platelet counts were increased in diabetic patients with retinopathy (p less than 0.05), as was collagen-induced platelet aggregation (p less than 0.01). Prostacyclin stimulating factor was reduced in patients with retinopathy (p less than 0.05) and correlated within the plasma with lipid peroxides (r = -0.53, p less than 0.04) and albumin thiols (r = 0.64, p less than 0.01). The results suggest that diabetic patients, particularly with retinopathy, are under oxidative stress and have an increased thrombotic tendency with increased platelet reactivity and a reduction in prostacyclin stimulating factor.

Topics: Adult; Biological Factors; Blood Glucose; Diabetes Mellitus, Type 1; Diabetic Angiopathies; Diabetic Retinopathy; Female; Glycated Hemoglobin; Humans; Lipid Peroxides; Male; Malondialdehyde; Reference Values; Serum Albumin; Sulfhydryl Compounds; Superoxide Dismutase; Thromboxane B2

A decrease in the vitamin E content of human diabetic platelets is closely associated with the accelerated platelet aggregation and platelet prostaglandin metabolism seen in patients with diabetes mellitus. We investigated the effect of vitamin E supplementation on these abnormalities of physiological function and prostaglandin metabolism in 14 non-insulin dependent diabetics with proliferative retinopathy. ADP-induced platelet aggregation was inhibited in vitro by the addition of vitamin E in a dose-dependent manner. However, in lower concentrations considered to be physiological doses in vivo, significantly greater inhibition was observed in diabetic platelets than in the control platelets. Next, alpha-tocopheryl nicotinate was administered to diabetics at a daily dose of 600 mg. The platelet vitamin E content was restored to control levels in 13 of the 14 patients after 2-4 weeks of daily administration. The ADP-induced platelet aggregation rate, platelet thromboxane B2 (TXB2, a stable metabolite of TXA2, a vasoconstrictor production, and plasma TXB2 level were low in all 14 diabetics. In contrast, plasma 6-keto-PGF 1 alpha (a stable metabolite of PGI2, a vasodilator) was significantly increased and therefore the 6-keto-PGF 1 alpha/TXB2 ratio in plasma was restored to within normal limits. These results indicate that vitamin E may improve platelet function and prostaglandin metabolism in diabetes mellitus and may be able to provide further beneficial effects in relation to the development of diabetic vascular complications.

Topics: 6-Ketoprostaglandin F1 alpha; Adenosine Diphosphate; Blood Glucose; Blood Platelets; Diabetes Mellitus, Type 2; Diabetic Angiopathies; Female; Glycated Hemoglobin; Humans; Male; Middle Aged; Platelet Aggregation; Platelet Aggregation Inhibitors; Reference Values; Thromboxane B2; Time Factors; Vitamin E

Platelet aggregation, platelet cAMP levels and thromboxane B2 (TXB2) synthesis had been investigated in 40 diabetics (20 with microangiopathy and 20 without) and 24 normal controls. The washed platelets, but not platelet rich plasma (PRP), from the diabetics show greater sensitivity to aggregation in response to thrombin, collagen and arachidonic acid than controls (P less than 0.05). Platelets from the diabetics contain the significantly decreased cAMP levels (P less than 0.01) and synthesize the significantly greater amount of TXB2 (P less than 0.01) when induced by thrombin or collagen. Conversion of exogenously added arachidonic acid to TXB2 remained unchanged (P greater than 0.05). cAMP levels in platelets from the diabetics exhibited a significant negative linear correlation with thrombin- and collagen-induced TXB2 synthesis. There was no significant difference in platelet aggregation, platelet cAMP levels and platelet TXB2 synthesis between the diabetics with and without microangiopathy. It was suggested that in the diabetic platelets: The observed increase in platelet thromboxane A2 (TXA2) synthesis should be due to the increased activity of arachidonic acid-metabolizing system, most likely at phospholipase site; the elevated platelet TXA2 levels should inhibit platelet membrane-associated adenylate cyclase which lowered the cAMP levels in platelets; and this alternation should be the mechanism of platelet hyperaggregability, which might contribute in some way to diabetic microangiopathy.

Topics: Adult; Blood Platelets; Cyclic AMP; Diabetes Mellitus; Diabetes Mellitus, Type 1; Diabetes Mellitus, Type 2; Diabetic Angiopathies; Female; Humans; Male; Middle Aged; Platelet Aggregation; Thromboxane B2

Plasma concentrations of 6-keto-PGF1 alpha and thromboxane B2 (TXB2) were measured in 55 diabetics and 30 controls with radioimmunoassay. The correlation between diabetic microangiopathy and the ratio of TXB2 and 6-keto-PGF1 alpha was analysed. Diabetics were divided into three groups according to the change of retina and renal function. Group A, diabetics without microangiopathy; group B, diabetics with slight microangiopathy; and group C, diabetics with severe microangiopathy. The results showed that the ratio of TXB2/6-keto-PGF1 alpha was higher in B and C groups (0.997 +/- 0.31 1.10 +/- 0.25 means +/- S) than in the controls (0.72 +/- 0.17 means +/- S) (P less than 0.01). Group A patients had slightly higher level of the ratio (0.85 +/- 0.20 means +/- S) than the controls but the difference was not significant. The results suggest that the TXB2 and 6-keto-PGF1 alpha imbalance exists only in diabetics with microangiopathy and their imbalance might have more significance in the pathogenesis of diabetic microangiopathy than their individual change.

Topics: 6-Ketoprostaglandin F1 alpha; Adolescent; Adult; Aged; Diabetic Angiopathies; Female; Humans; Male; Middle Aged; Thromboxane B2

Topics: Adolescent; Adult; Aged; Cyclic AMP; Diabetes Mellitus; Diabetic Angiopathies; Female; Humans; Male; Middle Aged; Platelet Aggregation; Thromboxane B2

Streptozotocin diabetes in rats was complicated by spontaneous hypertension (SHR) and myocardial infarction (MIC), considered as "risk groups". Renal function was assessed on the basis of blood urea nitrogen (BUN) and albuminuria. BUN increased by 36% in Wistar diabetic group, by 100% in SHR + diabetes, and by 51% in MIR + diabetes. Morphologic changes were assessed by estimation of PAS-positive glycosaminoglycans and measurement of vascular wall thickness of glomerular arterioles. The risk groups showed exaggerated tendency for development of diabetic angiopathy. A significant imbalance between TXA2 and prostacyclin was found, which was reflected by TXB2/6-keto-PGF1 alpha (the stable metabolites of TXA2 and prostacyclin, respectively) ratio, which increased by 38% in Wistar diabetic rats, by 61% in SHR + diabetes, and by 133% in MIR + diabetes. These changes correlated very well with increased platelet aggregability (r = 0.70; p less than 0.05) and with increased lipid peroxide level (r = 0.60; p less than 0.05), but neither with total plasma cholesterol (r = 0.20), nor with plasma triglycerides (r = 0.34). Lipid peroxides increased 5-fold in Wistar diabetic rats, 6-fold in SHR + diabetes, and 5.5-fold in MIR + diabetes. A causative relationship between TXA2/PGI2 imbalance and lipid peroxide changes on one hand, and diabetic angiopathy, on the other, was suggested.

Topics: Animals; Blood Vessels; Diabetes Mellitus, Experimental; Diabetic Angiopathies; Hypertension; Kidney; Lipid Peroxides; Lipids; Male; Myocardial Infarction; Pancreas; Platelet Aggregation; Prostaglandins F; Rats; Rats, Inbred SHR; Rats, Inbred Strains; Thromboxane B2

It has been speculated that platelet activation may contribute to the evolution of vascular complications in patients with Type I diabetes mellitus. To address this hypothesis, we measured the plasma and urinary metabolites of thromboxane, presumably of platelet origin, and of prostacyclin, derived from endothelial cells, in addition to more conventional indexes of platelet function. Urinary excretion of the metabolites 2,3-dinor-thromboxane B2 and 2,3-dinor-6-keto-prostaglandin F1 alpha did not differ between diabetics with or without retinopathy and nondiabetic controls. Furthermore, measurement of platelet granule constituents, the aggregation responses to ADP or arachidonic acid, and levels of serum thromboxane B2 failed to discriminate between the groups. The institution of tight diabetic control with multiple daily injections of insulin failed to alter either urinary metabolite excretion or plasma levels of 11-dehydro-thromboxane B2. Conversely, insulin-induced hypoglycemia failed to alter the concentrations of plasma or urinary thromboxane metabolites in nondiabetic volunteers, despite a mean 60-fold increase in plasma epinephrine. These studies suggest that platelet activation does not precede the development of microvascular complications in patients with Type I diabetes who lack clinical evidence of macrovascular disease and have normal renal function. Furthermore, it is unlikely that platelet activation due to intermittent hypoglycemia contributes to the reportedly accelerated development of retinopathy in such patients, when they are subject to tight diabetic control.

Topics: 6-Ketoprostaglandin F1 alpha; Adolescent; Adult; Blood Platelets; Diabetes Mellitus, Type 1; Diabetic Angiopathies; Epoprostenol; Humans; Insulin; Platelet Aggregation; Thromboxane B2; Thromboxanes

Haemostatic variables were assessed in 43 patients, 28 insulin-dependent and 15 non insulin-dependent. Maximum aggregation by low concentrations of adenosine diphosphate (ADP) or arachidonic acid and elevated plasma concentrations of TxB2, Factor VIII, vWF:Ag, RCoF and fibronectin (Fnct) indicated a hypercoagulable state. The manifestation of vasculopathy was associated with elevated concentrations of RCoF, Fnct, Hbalc, cholesterol and triglycerides, while impaired fibrinolysis was demonstrated by decreased t-PA levels and the absence of crosslinked fibrin degradation products (XL-FDP).

Topics: Adolescent; Adult; Aged; Blood Coagulation; Diabetic Angiopathies; Female; Fibrin Fibrinogen Degradation Products; Fibronectins; Hemostasis; Humans; Male; Middle Aged; Platelet Aggregation; Thromboxane B2; Tissue Plasminogen Activator

We compared the ability of aspirin to suppress platelet aggregation and thromboxane synthesis in ten normal subjects and ten patients with diabetic angiopathy and high rate of entry of new platelets into the circulation. When single doses of 100 to 1,000 mg aspirin were ingested daily for 1 month, there were time gaps between doses in which platelets from diabetics and normals aggregated and formed thromboxane ex vivo in response to the combination of arachidonic acid plus collagen. Similar gaps were also found for diabetics, but not for normals, following four daily doses (every six hours) of 25 or 100 mg. Our data show that dose schedules of aspirin which may suffice in normals are not effective in patients with diabetic angiopathy, presumably because these patients have a high rate of entry of new platelets into the circulation. We suggest that continual suppression of platelet thromboxane synthesis and aggregation by low-dose, "slow-release" preparations of aspirin would be an ideal long-term approach for the prevention of thrombosis in patients with a high rate of entry of new platelets into the circulation.

Topics: Adenosine Triphosphate; Adult; Arachidonic Acid; Arachidonic Acids; Aspirin; Blood Platelets; Collagen; Diabetes Mellitus; Diabetic Angiopathies; Drug Administration Schedule; Female; Humans; Male; Malondialdehyde; Middle Aged; Platelet Aggregation; Thromboxane B2

Patients with diabetes mellitus manifest increased in vitro platelet aggregation and increased synthesis of the proaggregant and vasoconstrictor, thromboxane A2 (TXA2). We studied the effects of continuous insulin infusion treatment on platelet aggregation and arachidonic acid (AA)-stimulated platelet TXA2 synthesis (15 and 30 s post-AA, 1 mM) in 16 type I diabetic patients. Strict glycemic control was induced with the Biostator for 2 days and maintained for 12-14 days with continuous subcutaneous insulin infusion (CSII). The average premeal plasma glucose level (4/day) fell from 184 +/- 15, before treatment, to 107 +/- 6 mg/dl on the final day (P less than 0.001). After control, platelet synthesis of TXA2, measured by radioimmunoassay of its stable metabolite, immunoreactive TXB2 (iTXB2), decreased in all patients (30 s: 276 +/- 31 versus 199 +/- 28 ng iTXB2/ml/5 X 10(5) platelets; P less than 0.05). The reduction in platelet iTXB2 synthesis (15 and 30 s) was greater in poorly controlled patients (HbA1c greater than 12%; N = 8), and for all patients the decrease in iTXB2 (15 and 30 s) was correlated with the prestudy HbA1c level (15 s: r = 0.6; P less than 0.01). In contrast, platelet aggregation responses did not improve during intensive insulin treatment. The ED50 for AA (dose producing 50% maximum aggregation at 1 min) was unchanged after 2 wk of treatment and the ED50 for aggregation induced by ADP fell significantly in patients with HbA1c greater than 12% (2.8 +/- 1.3 versus 1.2 +/- 0.6 microM; P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adenosine Diphosphate; Adolescent; Adult; Arachidonic Acid; Arachidonic Acids; Blood Glucose; Blood Platelets; Diabetes Mellitus, Type 1; Diabetic Angiopathies; Female; Humans; Insulin; Insulin Infusion Systems; Lipoproteins; Male; Middle Aged; Platelet Aggregation; Thromboxane A2; Thromboxane B2

Platelet thromboxane B2 production was studied in forty-seven non-insulin-dependent diabetics by incubating platelets with increasing concentrations of arachidonic acid. In comparison with thirty-two healthy subjects, diabetics showed increased thromboxane B2 production at 0.7 mmol/l (mean: 236 pmol/10(8) platelets, SEM 201-277; v. 135, 105-174; P less than 0.05) and at 1.0 mmol/l (673, 613-739; v. 405, 377-486, P less than 0.01) but not at 0.5 mmol/l. Patients were subdivided according to the presence or absence of vascular complications. Patients without microangiopathy showed significantly greater thromboxane B2 production than healthy subjects at all the arachidonic-acid concentrations (P less than 0.02 or less). Patients with microangiopathy had platelet thromboxane production similar to that observed in healthy subjects at all the arachidonic-acid concentrations (P greater than 0.30) but significantly lower than that of non-microangiopathic patients at 0.5 (P less than 0.01) and at 0.7 mmol/l arachidonic acid (P less than 0.05). These results indicate that non-insulin-dependent diabetics have increased production of platelet thromboxane B2 only when they do not have microvascular complications.

Topics: Adult; Aged; Arachidonic Acid; Arachidonic Acids; Blood Platelets; Cholesterol; Diabetes Mellitus, Type 2; Diabetic Angiopathies; Female; Humans; Male; Middle Aged; Thromboxane B2; Thromboxanes; Triglycerides

Concentrations of the stable antiaggregatory prostacyclin metabolite 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) and of the proaggregatory thromboxane A2 metabolite thromboxane B2 were measured by radioimmunoassay in plasma from 53 diabetics. In 33 of these patients the ability of platelets to produce thromboxane B2 during spontaneous clotting was also studied. Plasma 6-keto-PGF1 alpha concentrations were higher (p less than 0.05) in the diabetics (mean 107.7 +/- SE 7.6 ng/l) than in non-diabetic controls matched for age and sex (87.5 +/- 4.7 ng/l), and diabetics with microangiography (n = 28) and higher (p less than 0.01) concentrations (124.3 +/- 10.8 ng/l) than those without microangiography (n = 25; 89.2 +/- 9.3 ng/l). Plasma thromboxane B2 concentrations were also higher (p less than 0.01) in the diabetics (mean 218.5 +/- SE 25.3 ng/l) than in the controls (127.7 +/- 9.8 ng/l), but this increase was not related to microangiography. The ability of platelets to generate thromboxane B2 did not differ between the diabetics (181.4 +/- 16.4 microgram/l) and controls (195.8 +/- 11.8 microgram/l). Platelets of diabetics with microangiopathy or taking oral hypoglycaemic agents (n = 19), however, produced decreased amounts of thromboxane B2 during clotting. Plasma concentrations of 6-keto-PGF1 alpha and thromboxane B2 were not related to concentrations of glucose, haemoglobin A1, high-density lipoprotein cholesterol, cholesterol, triglycerides, magnesium, or creatinine. These results suggest that in diabetics with microangiopathy a balance between prostacyclin and thromboxane A2 is shifted to dominance by prostacyclin.

Topics: 6-Ketoprostaglandin F1 alpha; Adolescent; Adult; Aged; Blood Coagulation; Blood Platelets; Diabetes Mellitus; Diabetic Angiopathies; Female; Humans; Hypoglycemic Agents; Male; Middle Aged; Thromboxane B2; Thromboxanes