Determinants of ADP-induced platelet aggregation in diabetes mellitus

Platelet Measurements and Type 2 Diabetes: Investigations in Two Population-Based Cohorts

Type 2 diabetes is a major risk factor for cardiovascular disease. Given the contribution of platelets to atherothrombosis—which in turn is a major contributor to cardiac events, there may be cause to consider platelet function in management of diabetes. Despite the large body of research concerning the role of platelets in cardiovascular complications of type 2 diabetes, evidence from population-based studies of platelet aggregation in diabetes is limited. Mean Platelet Volume (MPV), a cell trait partially associated with markers of platelet activity, is more commonly available. We investigated the association of metabolic syndrome and diabetes with platelet aggregation to three physiological agonists, ADP, collagen, and epinephrine, in the Framingham Heart Study Offspring cohort. We further examined the relationship between MPV measured with Beckman Coulter LH750 instruments and self-reported diabetes as well as MPV and diabetes medication in the UK BioBank cohort, performing the largest such analysis to date. Increased platelet aggregation associated with prevalent diabetes was observed for low concentration epinephrine (0.1 μM) alone and only in analyses of participants stratified either by male sex and/or having metabolic syndrome. Other agonists and concentrations were not significant for prevalent diabetes, or in opposite direction to the main hypothesis (i.e., they showed lower platelet aggregation associated with diabetes). After a median of 18.1 years follow-up, no platelet aggregation trait was associated with increased risk of diabetes (n = 344 cases). As expected, increased MPV was significantly associated with diabetes (β = 0.0976; P = 8.62 × 10⁻³³). Interestingly, sex-stratified analyses indicated the association of MPV with diabetes is markedly stronger in males (β = 0.1232; P = 1.00 × 10⁻³¹) than females (β = 0.0514; P = 7.37 × 10⁻⁵). Among diabetes medications increased MPV was associated with Insulin (β = 0.1341; P = 1.38 × 10⁻¹¹) and decreased MPV with both Metformin (β = 0.0763; P = 1.99 × 10⁻⁶) as well as the sulphonylureas (β = 0.0559; P = 0.0034). Each drug showed the same direction of effect in both sexes, however, the association with MPV was nearly twice as great or more in women compared to men. In conclusion, platelet function as measured by aggregation to ADP, collagen, or epinephrine does not appear to be consistently associated with diabetes, however, MPV is robustly associated suggesting future work may focus on how MPV segments pre-diabetics and diabetics for risk prediction.

Platelet aggregation is not altered among men with diabetes mellitus

AIMS

Platelets are pivotal in arterial thrombosis, and platelet hyperresponsiveness may contribute to the increased incidence of cardiovascular events in diabetes mellitus. Consequently, we hypothesized that increased in vitro platelet aggregation responses exist in men with diabetes mellitus.

METHODS

The Danish Cardiovascular Screening Trial (DANCAVAS) is a community-based cardiovascular screening trial including men aged 65-74 years. Platelet aggregation was tested using 96-well light transmission aggregometry with thrombin receptor-activating peptide (TRAP), adenosine diphosphate, collagen type 1, arachidonic acid and protease-activated receptor-4 in three concentrations. Further, cardiovascular risk factors and coronary artery calcification (CAC), estimated by CT scans and ankle-brachial index, were obtained.

RESULTS

Included were 720 men aged 65-74 years, 110 with diabetes mellitus. Overall, there was no difference in platelet aggregation among men with versus without diabetes mellitus when adjusting for or excluding platelet inhibitor treatment and men with established cardiovascular disease (CVD). This was true for all agonists, e.g., 10 µM TRAP-induced platelet aggregation of median 69% (IQR 53-75) versus 70% (IQR 60-76) in men with versus without diabetes mellitus. Platelet aggregation did not correlate with HbA_1c or CAC. Men with diabetes mellitus displayed higher CAC, median 257 Agatston units (IQR 74-1141) versus median 111 Agatston units (IQR 6-420) in the remaining individuals, p < 0.0001.

CONCLUSIONS

Among outpatients with diabetes mellitus, but no CVD and no platelet inhibitor treatment, neither are platelets hyperresponsive in diabetes mellitus, nor is platelet aggregation associated with glycemic status or with the degree of coronary atherosclerosis.

TRIAL REGISTRATION

ISRCTN12157806.

Glycaemic control, smoking habits and diabetes duration affect the extrinsic fibrinolytic system in type I diabetic patients but microangiopathy does not

The fibrinolytic system was studied in 43 type I diabetic patients with long duration of the disease, with or without evidence of microangiopathy, and in 26 control subjects. There were positive and independent correlations between tissue plasminogen activator (tPA) activity after venous occlusion and HbA1c, and between triglycerides and plasminogen activator inhibitor (PAI-1) and tPA antigen concentrations before and after venous occlusion. The tPA activities both at rest and after venous occlusion were higher in the patients. There were no differences with regard to sex, hypertension or nephropathy for the levels of fibrinolytic variables in these patients. Subjects with retinopathy did not differ from those without retinopathy. Diabetes duration showed a significant negative association with tPA activity in multivariate regression analysis. Tobacco-smoking diabetics, as compared to non-smoking, had an increased tPA antigen release at venous occlusion, but also higher PAI-1 levels and reduced specific activity of the tPA protein. When assessed with the new specific assays now available, the fibrinolytic parameters appear to be specific indicators of endothelial dysfunction related to smoking and to degree of glycaemic control in type I diabetic subjects.

Effect of traditional Greek Mediterranean meals on platelet aggregation in normal subjects and in patients with type 2 diabetes mellitus

Patients with type 2 diabetes mellitus have increased risk of cardiovascular disease. Epidemiological studies have shown a correlation between diet and incidence of coronary heart disease. The aim of the study is to determine the effect of a traditional Greek Mediterranean diet on platelet aggregation induced by ADP, arachidonic acid (AA), and especially platelet-activating factor (PAF) on patients with type 2 diabetes mellitus as well as on healthy volunteers. The patients were randomized into two subgroups, A and B. The lipid extracts from traditional Greek Mediterranean-type meals were tested in in vivo for their ability to reduce PAF- or thrombin-induced platelet aggregation. The meals with the most potent anti-aggregating activity were chosen for the diet of both subgroup A and healthy subjects and consumed for a period of 28 days, whereas subgroup B kept to their regular diet that was followed before entering the study. Platelet-rich plasma was isolated before and after the diet, and the ability of platelets to aggregate under the aggregating factors was tested. One-month consumption of diet resulted in a significant reduction in PAF- and ADP-induced aggregation of platelets in both groups of healthy volunteers (PAF and ADP, P < .05) and subgroup A (PAF, P < .001; ADP, P < .05), whereas the AA-induced aggregation was not affected. No effect was observed in subgroup B, which followed the standard diet. Thus the consumption of a traditional Greek Mediterranean diet even for a short period can reduce platelet activity in patients suffering from type 2 diabetes mellitus and in healthy subjects.

Effect of fast-food Mediterranean-type diet on type 2 diabetics and healthy human subjects' platelet aggregation

OBJECTIVE

The aim of our work was to carry out a randomized clinical trial with a fast-food Mediterranean type diet rich in platelet activating factor (PAF) antagonist to investigate the effect on type 2 diabetics and healthy human subject's platelet aggregation.

RESEARCH DESIGN AND METHODS

We extracted lipids from fast-food Mediterranean type foodstuffs, and tested them in vitro for their ability to inhibit or antagonize PAF towards washed rabbit platelets. We chose the foodstuffs that exerted the most potent in vitro anti-PAF activity and fed 22 healthy (group A) and 23 type 2 diabetics (group B) subjects on a diet containing the chosen foodstuffs. The 22 type 2 diabetics (group C) subjects were kept on their regular diet that was being followed before entering the study. Before and after a 4-week diet, all enrolled subjects underwent the following examinations; measurement of total cholesterol, low density lipoprotein (LDL-cholesterol), high density lipoprotein (HDL-cholesterol), triglycerides, glucose, HbA(1c), body mass index (BMI), and platelet aggregation in response to PAF, adenosine 5' diphosphate (ADP) and arachidonic acid (AA).

RESULTS

The chosen diet significantly increased the EC(50) values of PAF and ADP to groups A and B (p<0.05). No statistical difference was observed on the EC(50) value of group C. No statistical differences were detected among Cholesterol, LDL-cholesterol, triglycerides, glucose, HBA(1c), BMI, and EC(50) for AA values, for any of the three groups.

CONCLUSIONS

Consumption of a fast-food Mediterranean type diet rich in PAF antagonist improved platelet response of type 2 diabetics and healthy human subjects against thrombotic, inflammatory and proatherogenic factors.

A cross-sectional evaluation of spontaneous platelet aggregation in relation to complications in patients with type II diabetes mellitus

To clarify the relationship between platelet function and diabetic complications, we investigated spontaneous platelet aggregation (SPA) and agonist-induced platelet aggregation by a particle counting method using light scattering (LS) and by a conventional light transmission method (LT) in 23 age- and sex-matched control subjects and 74 patients with type II diabetes mellitus. We also observed platelets using the FIC-2 (TOA Medical Electronics, Kobe, Japan) flow cytometer and imaging device. Observation by the FIC-2 device showed microaggregates of platelets in samples with increased SPA-LS. SPA-LS was significantly elevated in patients with type II diabetes mellitus as a whole compared with control subjects. SPA-LS also showed significant differences between control subjects and three diabetic patient subgroups with a varying severity of retinopathy, nephropathy, or neuropathy, and the mean values increased along with the increasing severity of complications. On the other hand, although SPA-LT also showed significant differences between these groups, the absolute values were all less than 10%, which we believe does not warrant quantitative analysis. Adenosine-5'-diphosphate (ADP)-induced platelet aggregation failed to show significant differences between controls and subjects with a varying severity of retinopathy by either LS or LT, which indicates that SPA is more sensitive than agonist-induced platelet aggregation in relation to diabetic complications. We observed significant correlations between SPA-LS and the patients' age, hemoglobin A1c (HbA1c) level, plasma fibrinogen level, or 6-keto-PGF1alpha (6KF) to 11-dehydro-thromboxane B2 (TXB2) ratio. Our study demonstrated a close relationship between platelet hyperaggregability and diabetic complications, and a longitudinal prospective study of SPA-LS in diabetic patients is warranted to clarify cause-and-effect relationships.

Platelet reactivity is increased in mild gestational diabetes compared with normal pregnancy

The purpose of this study was to measure blood platelet aggregation in pregnant women with gestational diabetes and its correlation with normal pregnancies. The study group included 10 women with diabetes of pregnancy and a group of 10 healthy pregnant women. We used the method of adenosine diphosphate (ADP) platelet stimulation with three different ADP solutions. The mean platelet aggregation and time in seconds was measured in each patient with the three different solutions. The analysis of our results showed that platelet activity was statistically increased (P < 0.001) in the group of diabetics compared with the group of normal pregnancies. Our conclusion is that platelet activity in patients with gestational diabetes appears to be enhanced, probably as a result of a disturbance in the equilibrium between prostacyclin and thromboxane.

Comparison of platelet aggregability in Japanese type 2 diabetic patients with and without microalbuminuria

Microalbuminuria is associated with higher cardiovascular morbidity and mortality in Type 2 (non-insulin-dependent) diabetic patients. This study was designed to assess whether Type 2 diabetic patients with microalbuminuria (urinary albumin excretion rate (AER) 20-200 microgram min-1) is associated with alterations in platelet aggregability as compared with those with normal urinary albumin excretion (AER < 20 microgram min-1). Platelet aggregability was compared between 21 Japanese Type 2 diabetic patients with microalbuminuria and 21 individually pair-matched (for age, sex, body mass index, treatment, and HbA1c level) patients with normoalbuminuria. The in vitro platelet aggregation induced by 1.0 and 3.0 mumol l-1 ADP and 0.5 and 1.0 mg l-1 collagen was measured using platelet-rich plasma. No significant differences were observed between the two groups in the values for maximum percent platelet aggregation, percent aggregation at 3 min, and aggregation velocities after adding ADP or collagen. Microalbuminuric patients had significantly higher mean values for systolic (p < 0.004) and diastolic (p < 0.02) blood pressures and plasma fibrinogen level (p < 0.03) as compared with the respective mean values in normoalbuminuric patients. The results suggest that Japanese microalbuminuric Type 2 diabetic patients do not differ in the degree of platelet aggregability as compared with normoalbuminuric patients, despite an increase in certain other coronary risk factors.

Platelet function and composition in heart transplant recipients compared with nontransplanted coronary patients

Accelerated coronary artery disease seems to be the main condition limiting long-term survival after heart transplantation. Ninety-one heart transplant recipients were compared with 94 nontransplanted coronary artery disease patients in an attempt to identify the factors responsible for the accelerated form of coronary artery disease occurring after heart transplantation. Among the parameters examined, heart transplant recipients exhibited a higher plasma level of insulin (8.5 +/- 0.5 versus 6.2 +/- 0.3 mIU/l, p = 0.002), a lower plasma level of vitamin E (14.8 +/- 0.4 versus 16.9 +/- 0.7 mg/l, p = 0.03), a higher platelet cholesterol-to-phospholipid ratio (8.9 +/- 0.3 versus 7.6 +/- 0.3, p = 0.007), and an increased response to ADP-induced platelet aggregation (for the first wave, 29.1 +/- 0.9% of maximal aggregation versus 25.1 +/- 1.0%, p = 0.002; for the second wave, 21.4 +/- 1.4% versus 15.9 +/- 1.1%, p = 0.002, after adjustment for hematocrit), but no untoward changes in the level of fibrinogen, plasminogen activator inhibitor-1, antithrombin III, or lipoprotein(a). In addition, platelet aggregation in patients who required retransplantation as a result of severe coronary artery disease was similar before and after retransplantation. This suggests that severe coronary artery disease is not the cause of platelet hyperaggregability. In multiple-regression analysis, ADP-induced platelet aggregation in heart transplant recipients was significantly positively related to blood glucose (r = 0.50, p less than 0.001) and inversely related to n-3 fatty acids from platelet phospholipids (r = 0.40, p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Increased inositol phosphate accumulation in platelets from patients with NIDDM

We evaluated thrombin-induced inositol phosphate accumulation in [3H]inositol-labeled platelets prepared from patients with non-insulin-dependent diabetes mellitus. There were no significant differences in [3H]inositol incorporation into and contents of phosphoinositides between the diabetic patients and their age-matched control subjects. Thrombin induced a dose- and time-dependent accumulation of inositol phosphate. The accumulation of [3H]inositol trisphosphate and [3H]inositol bisphosphate by thrombin stimulation were significantly enhanced in platelets from the diabetic patients, although the accumulation of [3H]inositol monophosphate did not differ between the diabetic patients and the control subjects. In addition, the platelet aggregation rate induced by thrombin was also significantly enhanced in the diabetic patients in correlation with the enhanced inositol phosphate accumulation. These results suggest that increased inositol phosphate accumulation may cause accelerated platelet functions in diabetes mellitus.

Increased intracellular calcium mobilization in platelets from patients with type 2 (non-insulin-dependent) diabetes mellitus

Enhanced platelet functions have been reported in patients with diabetes mellitus. Our recent study demonstrated that phosphoinositide turnover is increased in platelets from diabetic patients. In the present study, we evaluated the abnormality in platelet intracellular calcium mobilization in patients with Type 2 (non-insulin-dependent) diabetes mellitus using fura-2, a fluorescent calcium indicator. Washed platelets were prepared from six diabetic patients with increased platelet aggregation rates (DM-A group), seven diabetic patients with normal platelet aggregation rates (DM-B group), and eight age-matched healthy control subjects. The basal intracellular free calcium concentrations in platelets were similar among the three groups. Thrombin (0.025-0.1 U/ml) induced a dose-dependent increase in intracellular calcium in both the presence and the absence of extracellular calcium. This increase in the presence of extracellular calcium, which depends on calcium influx and release, was significantly higher in the DM-A group than in the DM-B and control groups. However, there was no significant difference between the control group and the DM-B group. In the absence of extracellular calcium, thrombin-induced calcium increase, which depends only on calcium release, was also significantly enhanced in the DM-A group. Furthermore, the calcium increase stimulated by platelet-activating factor (10 nmol/l) with and without extracellular calcium was significantly higher in the DM-A group than in the other groups. Additionally, calcium ionophore A23187 (100 nmol/l) caused a significantly higher calcium increase in the DM-A group with extracellular calcium, while the calcium increase without extracellular calcium showed no significant difference among the three groups. These observations suggest that enhanced intracellular calcium mobilization due to increased calcium influx and release may be closely related to platelet hyperfunctions in diabetes mellitus.

Catecholamines and blood glucose control in type 1 diabetes

To evaluate the influence of blood glucose control on serum catecholamine levels (which reflect both plasma and platelet levels), six healthy non-diabetic subjects, seven well-controlled Type 1 diabetic patients, and six poorly controlled Type 1 diabetic patients were studied before (baseline) and after standardized exercise. A significant correlation was found between serum noradrenaline and HbA1 at baseline (r = 0.53, p less than 0.025) and after exercise (r = 0.71, p less than 0.001). Similar results were found for serum adrenaline (r = 0.68, p less than 0.005 and r = 0.61, p less than 0.005, respectively) and consequently total serum catecholamine content (r = 0.65, p less than 0.005 and r = 0.75, p less than 0.001, respectively). However, no relationship was found between serum catecholamine levels and actual blood glucose levels, age, body mass index or insulin dose. A moderate correlation was found between systolic blood pressure and serum levels of noradrenaline and total catecholamines after exercise (r = 0.48 and r = 0.48, both p less than 0.025).

A new hypoglycemic agent, midaglizole, blunts diabetic platelet aggregation: a possible role of alpha 2 blockade

A newly developed alpha 2 blocker, midaglizole (DG-5128, 2-[2-(4,5-dihydro-1H-imidazol-2-yl)-1-phenylethyl] pyridine dihydrochloride sesquihydrate) has been shown to have a hypoglycemic action in healthy controls as well as in diabetics. Since human platelets are rich in alpha 2 receptors, the effects of midaglizole on platelet aggregation were investigated. In normal controls, ADP- or epinephrine-induced platelet aggregation was significantly inhibited 2 h after oral administration of 300 mg midaglizole. Midaglizole also suppressed diabetic platelet aggregation stimulated by 10 or 100 microM epinephrine and delayed the initiation of collagen-induced aggregation at 30 micrograms/ml. In vitro addition of midaglizole at 9 or 90 microM significantly inhibited epinephrine-induced platelet aggregation. Furthermore, long-term administration of midaglizole suppressed diabetic platelet aggregation induced by 0.5-1 microM ADP or 1 microM epinephrine. These results suggest that alpha 2 blockade not only blunts diabetic epinephrine-induced platelet aggregation but also affects ADP- or collagen-stimulated platelet aggregation, indicating that this alpha 2 blocker may offer a new approach to the treatment of diabetic microangiopathy.