Primary platelet activation in recent-onset type 1 diabetes mellitus

CD11b+ bone marrow-derived monocytes are the major leukocyte subset responsible for retinal capillary leukostasis in experimental diabetes in mouse and express high levels of CCR5 in the circulation

We investigated the phenotype of cells involved in leukostasis in the early stages of streptozotocin-induced diabetes in mice by direct observation and by adoptive transfer of calcein-AM-labeled bone marrow-derived leukocytes from syngeneic mice. Retinal whole mounts, confocal microscopy, and flow cytometry ex vivo and scanning laser ophthalmoscopy in vivo were used. Leukostasis in vivo and ex vivo in retinal capillaries was increased after 2 weeks of diabetes (Hb A(1c), 14.2 ± 1.2) when either donor or recipient mice were diabetic. Maximum leukostasis occurred when both donor and recipient were diabetic. CD11b(+), but not Gr1(+), cells were preferentially entrapped in retinal vessels (fivefold increase compared with nondiabetic mice). In diabetic mice, circulating CD11b(+) cells expressed high levels of CCR5 (P = 0.04), whereas spleen (P = 0.0001) and retinal (P = 0.05) cells expressed increased levels of the fractalkine chemokine receptor. Rosuvastatin treatment prevented leukostasis when both recipient and donor were treated but not when donor mice only were treated. This effect was blocked by treatment with mevalonate. We conclude that leukostasis in early diabetic retinopathy involves activated CCR5(+)CD11b(+) myeloid cells (presumed monocytes). However, leukostasis also requires diabetes-induced changes in the endothelium, because statin therapy prevented leukostasis only when recipient mice were treated. The up-regulation of the HMG-CoA reductase pathway in the endothelium is the major metabolic dysregulation promoting leukostasis.

The relationship between glycemic control and platelet activity in type 2 diabetes mellitus

AIMS

Platelet activity and aggregation potential, which are essential components of thrombogenesis and atherosclerosis, can be conveniently estimated by measuring mean platelet volume (MPV) as part of whole blood count. It has been shown that MPV was significantly higher in diabetes mellitus (DM); however, the effect of glycemic control on MPV has not been studied. The aim of this study was to investigate the relationship among MPV, glycemic control, and micro- and macrovascular complications in type 2 DM.

METHODS

Seventy patients with type 2 DM and 40 age- and sex-matched healthy individuals were enrolled. Diabetic patients were grouped into those with glycated hemoglobin (HbA1c) levels <or=7% (Group A, n=35 patients) and those with HbA1c >7% (Group B, n=35 patients). Initially, both groups were compared with regard to MPV, HbA1c, serum lipid levels, coronary artery disease, retinopathy, neuropathy, and nephropathy. Thereafter, Group B was called to monthly visits to obtain improved control glycemic control, which was defined as achievement of HbA1c <or=7%. At the end of 3 months of follow-up, Group B was reevaluated.

RESULTS

MPV was significantly higher in patients with DM than in controls (8.7+/-0.8 fl vs. 8.2+/-0.7 fl, P=.002). In diabetic patients, there was a significant positive correlation between MPV and HbA1c levels (r=.39, P=.001) but not diabetic vascular complications. When we compared the two diabetic groups, Group B patients had significantly higher MPV than Group A (9.0+/-0.7 fl vs. 8.4+/-0.8 fl, P=.01). Thirty patients (86%) of Group B achieved improved glycemic control at the end of the 3 months. MPV of the patients with improved glycemic control were significantly decreased compared to baseline MPV (8.4+/-0.8 fl vs. 9.0+/-0.7 fl, P=.003).

CONCLUSIONS

Our results suggested a close relationship between poor glycemic control and increased platelet activity in patients with type 2 DM. Furthermore, platelet activity recovered through improved glycemic control, which may prevent the possible role of platelets in cardiovascular events in these patients.

Elevated concentrations of soluble adhesion molecules and large platelets in diabetic patients: are they markers of vascular disease and diabetic nephropathy?

P-selectin, E-selectin, and mean platelet volume are markers associated with platelet reactivity that have been demonstrated to be increased in diabetes. We were particularly interested to see if there was a difference in mean platelet volume and selectins between diabetics and nondiabetics, and in diabetics with and without nephropathy, and whether there was a correlation between mean platelet volume and selectins. One hundred and fourteen diabetic patients and 31 healthy controls were investigated. Plasma levels of P-selectin and E-selectin were higher in the diabetic group than in controls (P = .001 and P = .007, respectively) and in diabetic patients with proteinuria than in patients without proteinuria (P = .002 and P = .004, respectively). Protein excretion was lower in patients with low mean platelet volume values (P = .004). In conclusion, elevated platelet volume and high selectin values may play a role in the development of vasculopathies and complications in diabetes mellitus. Further studies are needed to prove these results.

Mean platelet volume in patients with type 2 diabetes mellitus

AIM OF THE STUDY

To evaluate mean platelet volume (MPV) in type 2 diabetic versus non-diabetic patients, as well as to investigate the associations between MPV and diabetic complications.

MATERIALS AND METHODS

This study included 416 patients divided into two groups. Group A comprised 265 type 2 diabetic patients (131 men) with a mean age of 67.4 +/- 9.5 years and a mean diabetes duration of 14.5 +/- 5.7 years. Group B comprised 151 non-diabetic patients (74 men) with a mean age of 68.6 +/- 9.1 years. MPV (blood samples anticoagulated with sodium citrate) was measured in two blood cell counters (Sysmex SF 3000 and Cell-Dyn 3700).

RESULTS

MPV was significantly higher (P = 0.01) in group A (14.2 +/- 2.2 fl) than in group B (7.1 +/- 1.2 fl). In group A MPV was significantly higher (P = 0.043) in patients with retinopathy (15.8 +/- 1.3 fl) than in patients without retinopathy (10.9 +/- 1.1 fl) and also significantly higher (P = 0.044) in patients with microalbuminuria (15.6 +/- 1.2 fl) than in patients without microalbuminuria (10.1 +/- 1.2 fl). No association, however, was found in group A between MPV and age, gender, duration of diabetes, insulin dependency, BMI, HbA1c, coronary artery disease or dyslipidaemia.

CONCLUSIONS

MPV is higher in type 2 diabetic patients than in non-diabetic patients. Among type 2 diabetic patients MPV is higher in those who have microvascular complications (retinopathy or microalbuminuria).

Mean platelet volume in Type 2 diabetic patients

BACKGROUND

Altered platelet morphology and function have been reported in patients with diabetes mellitus. They are likely to be associated with the pathological processes and increased risk of vascular disease seen in these patients. We aimed to determine the mean platelet volume (MPV) in diabetics compared to nondiabetics, to see if there is a difference in MPV between diabetics with and without macro- and microvascular complications, and to determine the correlation between MPV and fasting blood glucose, glycosylated hemoglobin (HbA(1)c), patient age, and duration of diabetes, respectively.

METHODS

We measured MPV in 145 consecutive Type 2 diabetic patients and 100 nondiabetic control subjects without known coronary artery disease who had complete blood count on venous blood sample taken into tripotassium EDTA, using a Roche Minos cell counter and automatic blood counter (CELL-DYN 3500). The blood glucose level was measured by glucose oxidase method and HbA1c by calorimetrical method in the autoanalyser. Statistical evaluation was performed by SPSS for Windows statistics programme using multivariate logistical regression analysis, Student's t, and Pearson correlation tests.

RESULTS

MPV was significantly higher and the mean platelet counts were significantly lower in diabetics compared to age- and sex-matched nondiabetic healthy controls [10.62+/-1.71 fl vs. 9.15+/-0.86 fl (P=.00), 260.38+/-68.65 x 10(9)/l vs. 292.33+/-79.19 x 10(9)/l (P=.001)], respectively.

CONCLUSIONS

Our results show significantly higher MPV in diabetic patients than in the nondiabetic controls. This suggests that platelets may play a role in the micro- and macrovascular complications of diabetic patients.

Increased synthesis of thromboxane A(2) and expression of procoagulant activity by monocytes in response to arachidonic acid in diabetes mellitus

Thromboxane A(2) (TXA(2)) synthesis and expression of procoagulant activity (PCA) were investigated in mononuclear cells and monocytes prepared from a control and a Type 2 diabetic group. Monocytes from the diabetic group produced 2.10+/-0.81 ng of TXB(2)/5 x 10(5) monocytes compared to 1.26+/-0.43 ng/5 x 10(5) monocytes by the control group (P<0.01, n=11) when incubated in autologous plasma containing arachidonic acid (200 microg/ml). When monocytes were incubated in buffer containing arachidonic acid (20 microg/ml), cells from the diabetic group produced 1.65+/-0.68 ng of TXB(2)/5 x 10(5) monocytes compared to 1.07+/-0.31 ng/5 x 10(5) monocytes by the control group (P<0.02, n=12). Expression of PCA was examined in mononuclear cell preparations. Basal and maximally stimulated PCA with lipopolysaccharide (4.2 microg/ml) were not different between control and diabetic groups. However, arachidonic acid induced a four-fold (P<0.001) increase in PCA in the diabetic group. This activity was characterized as tissue factor. Increased synthesis of TXA(2) and expression of PCA may potentiate thrombosis and increase fibrin deposition, events that play primary roles in the development of vascular disease.

Different effects of strenuous exercise and moderate exercise on platelet function in men

BACKGROUND

Platelets play an important role in the pathogenesis of cardiovascular diseases. It is also noticed that on one hand, regular exercise can reduce the risk of cardiovascular diseases, and on the other hand, vigorous exercise provokes sudden cardiac death. We therefore hypothesize that various intensities of exercise may affect platelet function differently.

METHODS AND RESULTS

Strenuous and moderate exercise (about 50% to 55% of peak oxygen consumption, VO2peak) on a bicycle ergometer in 10 sedentary and 10 physically active healthy young men was executed on two separate occasions. Blood samples were collected before and immediately after exercise. A newly designed tapered parallel plate chamber was used to assess platelet adhesiveness. Platelet aggregation induced by ADP was evaluated by the percentage of reduction in single platelet count. beta-Thromboglobulin (beta-TG) and platelet factor 4 (PF4) were measured by ELISA. In addition, a similar study on 5 patients with stable angina were also conducted. Our results showed that (1) in the sedentary healthy group, platelet adhesiveness and aggregation were increased by strenuous exercise and depressed by moderate exercise; (2) in the active healthy group, platelet adhesiveness and aggregation were enhanced by severe exercise, whereas only aggregation was decreased by moderate exercise; (3) in the patients with stable angina, platelet adhesiveness and aggregation were enhanced by strenuous exercise and adhesiveness was suppressed by moderate exercise; (4) the degree of hemoconcentration induced by acute exercise tended to be related to the severity of exercise in all subjects; and (5) although severe exercise elevated beta-TG and PF4, there were no significant changes in beta-TG, PF4, and the ratio of beta-TG to PF4 in healthy subjects after exercise.

CONCLUSIONS

It is concluded that platelet adhesiveness and aggregability may be sensitized by strenuous exercise in both healthy subjects and patients with stable angina. In contrast, platelet function can be suppressed significantly by moderate exercise in the healthy and tends to be depressed in patients with stable angina. The former may increase the risk of cardiac arrest and the latter may protect us from cardiovascular diseases. In addition, the effects of acute exercise tend to be more pronounced in the sedentary than in the active.

Effects of acute exercise on the changes of lipid profiles and peroxides, prostanoids, and platelet activation in hypercholesterolemic patients before and after treatment

The effects of acute exercise on the changes of plasma lipid profiles and peroxides, prostanoids and platelet activation in hypercholesterolemic patients before and after pravastatin 5 mg twice daily treatment for 4 weeks was studied in 30 (M/F = 21/9, age = 52 +/- 7, Mean +/- SD) patients with plasma total cholesterol level > 240 mg/dl. Pravastatin significantly reduced plasma total and low density lipoprotein cholesterol levels as expected. All patients before and after treatment and 30 healthy controls performed a treadmill exercise test using the standard Bruce protocol. The cardiac performance was similar in all groups. Treadmill exercise did not influence lipid levels after plasma volume correction. Hypercholesterolemic patients had significantly higher pre-exercise levels of malondialdehyde, thromboxane beta 2 and beta-thromboglobulin than after treatment or than pre-exercise levels in the control group. Treatment with lipid lowering drug pravastatin lowered the levels of these three parameters. At peak exercise, superoxide dismutase activity and 6-keto-PGF1 alpha were elevated. At 10 min post exercise only malondialdehyde returned to pre-exercise levels. The superoxide dismutase, thromboxane B2 and beta-thromboglobulin remained significantly higher. In the control subjects plasma beta-thromboglobulin and thromboxane 2 returned to pre-exercise levels. These results suggest that hypercholesterolemia may induce lipid peroxidation and platelet activation in resting status. Lowering of plasma cholesterol of pravastatin causes a concomitant decrease in plasma malondialdehyde, thromboxane and beta-thromboglobulin suggesting a decrease in lipid peroxidation and platelet activation. These changes were more pronounced in the hypercholesterolemic patients. Pravastatin treatment attenuated the increase in both malondialdehyde, beta-thromboglobulin and the prostanoids, but not to the level of normal subjects.

Platelet aggregation and fatty acid composition of platelets in type 1 diabetes mellitus

A raised content of arachidonic acid in platelets from diabetic patients with retinopathy was found without differences in platelet aggregation: platelet aggregability was not related to platelet fatty acid composition. In diabetes, platelet aggregation was inversely correlated to non-esterified fatty acids in plasma and may suggest an inhibiting effect. Mean platelet volume was raised in the diabetic patients, but without hyperaggregability. The findings do not exclude a relationship between platelet fatty acids and platelet aggregability, but suggest that variations in levels of non-esterified fatty acids in plasma might interfere with platelet aggregation.