Biochemical and functional alterations associated with hypercholesterolemia in platelets from hypertensive patients

Microvesicles Correlated with Components of Metabolic Syndrome in Men with Type 2 Diabetes Mellitus and Lowered Testosterone Levels But Were Unaltered by Testosterone Therapy

Aims. To investigate how circulating microvesicle phenotypes correlate with insulin sensitivity, body composition, plasma lipids, and hepatic fat accumulation. We hypothesized that changes elicited by testosterone replacement therapy are reflected in levels of microvesicles. Methods. Thirty-nine type 2 diabetic males with lowered testosterone levels were assigned to either testosterone replacement therapy or placebo and evaluated at baseline and after 24 weeks. Microvesicles were analysed by flow cytometry and defined as lactadherin-binding particles within the 0.1-1.0 μm gate. Microvesicles of platelet, monocyte, and endothelial cell origin were identified by cell-specific markers and their expression of CD36 was investigated. Results. Triglycerides correlated positively with all investigated microvesicle phenotypes in this study (p < 0.05), and indicators of hepatic fat accumulation, alanine aminotransferase, and gamma glutamyltransferase correlated with platelet and endothelial microvesicles and CD36-expressing microvesicles from platelets and monocytes (p < 0.05). BMI, waist circumference, and fat percentage correlated with CD36-expressing monocyte microvesicles (p < 0.05), while insulin sensitivity did not correlate with any microvesicle phenotypes. Microvesicle levels were unaffected by testosterone therapy. Conclusions. Metabolic syndrome components and hepatic fat accumulation correlated with microvesicle phenotypes, supporting the involvement of especially CD36 on monocytes in metabolic syndrome pathogenesis. Although testosterone therapy improved body composition measures, microvesicle phenotype levels were unaffected. This trial was registered at ClinicalTrials.gov (NCT01560546).

Increased Mean Platelet Volume in Familial Hypercholesterolemia

Familial hypercholesterolemia (FH) is a genetic disorder of lipoprotein metabolism and increases the risk of premature cardiovascular diseases. In patients with FH, platelet function may be activated; however, the extent of this activation and its etiology are unclear. We aimed to evaluate the mean platelet volume (MPV), a marker of platelet activation, in patients with FH. The study group consisted of 164 patients with FH and 160 control patients. Controls were matched for age, gender, hypertension, and smoking. The MPV was significantly higher in patients with FH than in controls (9.2 ± 0.4 vs 7.9 ± 0.6 fL, respectively; P < .001). Platelet count was significantly lower among patients with FH when compared to control patients (259 ± 51 vs 272 ± 56 × 103/L, respectively; P = .03). In linear regression analysis, MPV was independently associated only with total cholesterol (β = .6, 95% confidence interval: 0.004-0.008, P < .001). We have shown that MPV was increased in patients with FH and that it was independently associated with total cholesterol level.

The influence of statin therapy on platelet activity markers in hyperlipidemic patients after ischemic stroke

INTRODUCTION

Low-density lipoprotein cholesterol (LDL-C) has been reported to increase platelet activation. Reducing the level of LDL-C with statins induces important pleiotropic effects such as platelet inhibition. This association between platelet activity and statin therapy may be clinically important in reducing the risk of ischemic stroke. We investigated the effect of simvastatin therapy on platelet activation markers (platelet CD62P, sP-selectin, and platelet-derived microparticles (PDMPs)) in hyperlipidemic patients after ischemic stroke.

MATERIAL AND METHODS

The study group consisted of 21 hyperlipidemic patients after ischemic stroke confirmed by CT, and 20 healthy subjects served as controls. We assessed the CD62P expression on resting and thrombin-activated blood platelets. CD62P and PDMPs were analyzed by the use of monoclonal antibodies anti-CD61 and anti-CD62 on a flow cytometer. The level of sP-selectin in serum was measured by the ELISA (enzyme-linked immunosorbent assay) method. All markers were re-analyzed after 6 months of treatment with simvastatin (20 mg/day).

RESULTS

Hyperlipidemic patients presented a significantly higher percentage of CD62+ platelets and higher reactivity to thrombin compared to control subjects. After simvastatin therapy hyperlipidemic patients showed a reduction of the percentage of resting CD62P(+) platelets (p = 0.005) and a reduction of expression and percentage of CD62P(+) platelets after activation by thrombin (median p < 0.05; percentage: p = 0.001). A decrease of sP-selectin levels (p = 0.001) and percentage of PDMPs (p < 0.05) in this group was also observed.

CONCLUSIONS

HMG-CoA reductase inhibitor therapy in stroke patients with hyperlipidemia may be useful not only due to the lipid-lowering effect but also because of a significant role in reduction of platelet activation and reactivity.

Plasma lipidomic profile signature of hypertension in Mexican American families: specific role of diacylglycerols

Both as a component of metabolic syndrome and as an independent entity, hypertension poses a continued challenge with regard to its diagnosis, pathogenesis, and treatment. Previous studies have documented connections between hypertension and indicators of lipid metabolism. Novel technologies, such as plasma lipidomic profiling, promise a better understanding of disorders in which there is a derangement of the lipid metabolism. However, association of plasma lipidomic profiles with hypertension in a high-risk population, such as Mexican Americans, has not been evaluated before. Using the rich data and sample resource from the ongoing San Antonio Family Heart Study, we conducted plasma lipidomic profiling by combining high-performance liquid chromatography with tandem mass spectroscopy to characterize 319 lipid species in 1192 individuals from 42 large and extended Mexican American families. Robust statistical analyses using polygenic regression models, liability threshold models, and bivariate trait analyses implemented in the SOLAR software were conducted after accounting for obesity, insulin resistance, and relative abundance of various lipoprotein fractions. Diacylglycerols, in general, and the DG 16:0/22:5 and DG 16:0/22:6 lipid species, in particular, were significantly associated with systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressure (MAP), as well as liability of incident hypertension measured during 7140.17 person-years of follow-up. Four lipid species, including the DG 16:0/22:5 and DG 16:0/22:6 species, showed significant genetic correlations with the liability of hypertension in bivariate trait analyses. Our results demonstrate the value of plasma lipidomic profiling in the context of hypertension and identify disturbance of diacylglycerol metabolism as an independent biomarker of hypertension.

Low-Density Lipoprotein-Lowering Medication and Platelet Function

Elevated low-density lipoprotein (LDL) cholesterol (LDL-C) levels represent one of the most important risk factors for atherosclerosis and therefore cardiovascular morbidity and mortality. LDL-C operates at different levels and through various classic and non-classic mechanisms. In particular, increased or modified LDL enhances platelet function and increases sensitivity of platelets to several naturally occurring agonists. Agents that lower LDL-C in hypercholesterolemic patients have been shown to interfere with platelet function. Several studies, in fact, suggested that statins exert anti-thrombotic effects largely as a result of an anti-platelet activity. Among the other LDL-C-lowering agents those acting by interfering with cholesterol reabsorption from the gut (cholestyramine, colestipol) do not appear to interfere with platelet function, whereas peroxisome proliferator-activated receptor agonists (such as fibrates) can inhibit platelet function. The full potential of these drugs in vascular protection is only just being realized. Further studies are still needed to elucidate the full therapeutic benefits of these agents in plaque stabilization and thrombosis.

Effects of statins beyond lipid lowering: Potential for clinical benefits

BACKGROUND

The role of statin drugs in the reduction of serum lipids has been well documented. More recently, evidence suggesting that statins may positively impact many organ systems and disease states independent of lipid reduction has emerged. The term "pleiotropic effects" has been used to refer to these properties. We reviewed the evidence exploring such potential effects.

METHODS

A search of the MEDLINE database was conducted for articles published between 1985 to 2005 on the pleiotropic and the lipid-lowering independent effects of statin drugs. The search terms "statin", "HMG-CoA reductase inhibitor", "pleiotropic effects", and "inflammation" were used. English language articles were selected for inclusion along with selected cross-references.

RESULTS

Numerous animal and clinical studies support the presence of a spectrum of beneficial effects for statins that are independent of their lipid-lowering properties. These effects are mediated by a variety of mechanisms and they suggest that the therapeutic role of statins may expand.

CONCLUSION

Statins have shown great promise beyond their lipid-lowering effects. Ongoing and future studies will help to further clarify the potential clinical impact of these "pleiotropic effects".

Beyond lipid lowering: the role of statins in vascular protection

The introduction of the hydroxy methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) in 1987 was a major advance in the prevention and treatment of cardiovascular disease. Several landmark clinical trials have demonstrated the benefit of lipid lowering with statins for the primary and secondary prevention of coronary heart disease (CHD), namely The Scandinavian Simvastatin Survival Study (4S), Cholesterol And Recurrent Events (CARE), Long-term Intervention with Pravastatin in Ischemic Disease (LIPID), West of Scotland Coronary Prevention Study (WOSCOPS) and Air Force/Texas Coronary Atherosclerosis Prevention Study (AFCAPS/TexCAPS). Although it is widely accepted that the majority of clinical benefit obtained with statins is a direct result of their lipid-lowering properties, these agents appear to display additional cholesterol-independent or pleiotropic effects on various aspects of cardiovascular disease, including improving endothelial function, decreasing vascular inflammation and enhancing plaque stability. Although the full impact of statin therapy on each of these processes is not fully understood, ongoing studies with current and new statins are likely to shed further light on the potential cholesterol-independent benefits of these agents.

Statin therapy and stroke prevention

Hypercholesterolemia has not traditionally been considered an important risk factor in the pathogenesis of stroke. However, recent studies show that statin therapy significantly reduces ischemic stroke for patients with established coronary artery disease. Statin therapy may reduce stroke through amelioration of precerebral atherosclerosis in the carotid artery and the aorta. Anti-atherosclerotic, anti-inflammatory, and antithrombotic actions of statins occur within the blood and in plaque. Statins may also protect against cerebral ischemia through beneficial modulation of the brain endothelial nitric oxide system. Ongoing studies are exploring the role of statin therapy in the primary prevention of stroke and in the prevention of cognitive decline and multi-infarct cerebrovascular disease.

Coagulofibrinolytic assessment of effects of bezafibrate on hypertriglyceridemia in postmenopausal women

The present study investigates the effect of bezafibrate on lipid levels and coagulofibrinolytic factors. Subjects enrolled in the study included 124 postmenopausal women with hypertriglyceridemia. We examined the levels of tissue plasminogen activator (t-PA), plasminogen activator inhibitor type-1 (PAI-1), and blood coagulation factors VII and X as parameters of coagulofibrinolysis. After 12 weeks of bezafibrate therapy, mean serum triglyceride (TG) and remnant-like particle lipoprotein cholesterol (RLP-C) levels significantly decreased from baseline. Activated factor X levels decreased significantly by 11.3% (P < 0.01) and the ratio of tPA/PAI-1 (0.146+/-0.07) increased significantly by 37.7% from baseline (P < 0.05). The rates of change in activated factor VII and PAI-1 showed a significant positive correlate with the rates of change in TG and RLP-C (P = 0.001). These present findings suggest that bezafibrate improves triglyceride-rich lipoprotein metabolism and coagulofibrinolytic activity by increasing fibrinolysis in postmenopausal women with hypertriglyceridemia.

The evolving role of statins in the management of atherosclerosis

Significant advances in the management of cardiovascular disease have been made possible by the development of 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase inhibitors--"statins." Initial studies explored the impact of statin therapy on coronary artery disease (CAD) progression and regression. Although the angiographic changes were small, associated clinical responses appeared significant. Subsequent large prospective placebo-controlled clinical trials with statins demonstrated benefit in the secondary and primary prevention of CAD in subjects with elevated cholesterol levels. More recently, the efficacy of statins has been extended to the primary prevention of CAD in subjects with average cholesterol levels. Recent studies also suggest that statins have benefits beyond the coronary vascular bed and are capable of reducing ischemic stroke risk by approximately one-third in patients with evidence of vascular disease. In addition to lowering low-density lipoprotein (LDL) cholesterol, statin therapy appears to exhibit pleiotropic effects on many components of atherosclerosis including plaque thrombogenicity, cellular migration, endothelial function and thrombotic tendency. Growing clinical and experimental evidence indicates that the beneficial actions of statins occur rapidly and yield potentially clinically important anti-ischemic effects as early as one month after commencement of therapy. Future investigations are warranted to determine threshold LDL values in primary prevention studies, and to elucidate effects of statins other than LDL lowering. Finally, given the rapid and protean effects of statins on determinants of platelet reactivity, coagulation, and endothelial function, further research may establish a role for statin therapy in acute coronary syndromes.

Palmitate induces structural alterations in nuclei of cardiomyocytes

The objective of this study was to examine the hypothesis that the alterations of cardiac nuclei, that has been noted in some cardiomyopathies, can be produced by palmitate, a saturated fatty acid present in high circulating concentrations in patients with conditions associated with a high probability of developing cardiomyopathy. Cardiomyocytes isolated from embryonic chick ventricle were maintained in culture for 72 h and then treated with palmitate, 100 microM for 24 h. Cells were stained with acridine orange or Giemsa and examined microscopically. Cell size and nuclear size were examined by forward light scatter during flow cytometry. Cells were permeabilized and their nuclei were stained with propidium iodide and examined by flow cytometry on populations of 10,000 cells. Cardiomyocytes treated with palmitate displayed changes in nuclear appearance as nuclei were larger, relative to cell size, with more intense acridine orange staining in a peripheral location. Nucleoli were often disrupted. Palmitate produced a significant (P < 0.001) and 17% increase in nuclear size compared to untreated cells using flow cytometry analysing forward light scatter to estimate nuclear and whole cells size. There were no significant changes in the size of the whole cell and ratio of nucleus to whole cell was significantly (P < 0.01) increased compared to control cells. Fluorescent activating cell sorting analysis of propidium iodide stained nuclei demonstrated that the nuclear enlargement was not due to cell mitosis as the proportion of nuclei in Go/G1, S or M was not changed by palmitate. In summary, these studies identify that palmitate can induce structural abnormalities of cardiomyocytes nuclei by producing increased nuclear size and nucleolar destruction.

Influence of hypercholesterolemia and endothelin-3 pre-treatment on the effects of shear forces on platelet aggregation and cyclic GMP content

Shear forces induce platelet aggregation and stimulate the endothelial production of anti-aggregatory factors. Among them, endothelin-3 (ET-3) has been reported to reduce aggregation and to increase platelet cyclic GMP (cGMP) content. Since hypercholesterolemia modifies both platelet aggregability and endothelial function, we compared in 14 hypercholesterolemic and 15 normocholesterolemic subjects the influences of shear forces (240 and 650 s(-1)) on platelet aggregation and cGMP content, and their modulation by ET-3. Spontaneous maximal aggregation occurred earlier and at a greater extent in hypercholesterolemic than in normocholesterolemic subjects (63+/-2 vs 46+/-6% P < 0.01). Pre-treatment with ET-3 abolished the shear-induced facilitation of maximal aggregation in platelets of normocholesterolemic (from 70+/-2 to 52+2% at 240 s(-1) and from 73+/-1 to 59+/-2S at 650s(-1); P < 0.05) and hypercholesterolemic (from 78+/-3 to 64+/-2 at 240 s(-1) and from 78+/-2 to 66+/-3 at 650 s(-1); P < 0.05) subjects. cGMP content did not significantly differ between normocholesterolemic and hypercholesterolemic subjects (6.1+/-0.5 vs 6.9+/-0.7 pmol/10(9) platelets). It was reduced in platelets submitted to shear forces (P < 0.05). This shear-dependent reduction was suppressed by ET-3 pre-treatment. These results demonstrate that shear forces enhance platelet aggregation and diminish their cGMP content. ET-3 reduces the pro-aggregating effects of shear, suggesting a rise in cGMP content as a dynamic associated mechanism.

A new system to detect native microaggregates of platelets in vivo, with a novel platelet aggregometer employing laser light scattering

Circulating platelets are susceptible to various stimuli in vessels, and a certain portion of platelets may thereby form native microaggregates (NMAs), which can be visualized by a bother scanning electron microscopy (SEM). We developed an easy method to evaluate the existence and extent of NMAs and the subsequent spontaneous platelet aggregation (SPA) induced by not any agonist but stirring force with a novel platelet aggregometer (PA-200; Kowa, Tsukuba, Japan) employing a particle-counting method based on laser light scattering. In this system, platelet-rich plasma obtained by a delicate centrifugation was infused in a cuvette to replace the content and to avoid stirring shear. An insertion attachment was designed in a coaxial shape to maintain a constant sample volume. Our data indicated that NMAs, tentatively defined as a "small" division by their light scattering (25-400 of the intensity threshold), could be detected by not only a complicated SEM but also by our simple system with the PA-200 in a few minutes. No correlation was found in the comparison of the existence of NMAs and the SPA generation, in aliquot platelets, respectively. These results suggested that NMAs and SPA might be mutually different cluster and have meanings as representations of platelet status.

Platelet hypoaggregability in hereditary hypertriglyceridemic rats: relation to plasma triglycerides

To define better the relationships between lipid metabolism disturbances and platelet aggregation we have examined these parameters in hereditary hypertriglyceridemic and control Lewis rats. Hereditary hypertriglyceridemic rats are hypertensive and have high plasma triglycerides but not elevated plasma total cholesterol. In the present study, we have demonstrated that platelets from hereditary hypertriglyceridemic rats have lowered initial rate and maximal aggregation after stimulation with thrombin or ADP in comparison with controls. These two strains did not differ significantly in the inhibition of platelet aggregation by the thromboxane A2 receptor inhibitor, SQ 29 548. In hereditary hypertriglyceridemic rats, the thrombin response, as well as the contribution of the thromboxane A2-sensitive pathway, were positively associated with the plasma level of triglycerides. Similar trend was found in Lewis rats. However, the slopes of these relationships were reduced in hereditary hypertriglyceridemic rats. These alterations of the aggregatory responses in hereditary hypertriglyceridemic rats were independent of blood pressure and plasma cholesterol level. In conclusion, our results showed a clear-cut platelet hypoaggregability to both thrombin and ADP in hypertensive hypertriglyceridemic rats. This hypoaggregability was not due to an impaired function of the thromboxane A2 pathway but could be connected with disturbances of lipid metabolism.

Vascular effects of statins in stroke

BACKGROUND

Recent clinical trials and meta-analyses of beta-hydroxy-beta-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) have demonstrated a reduction in ischemic stroke in patients with a history of coronary artery disease both with and without elevations of serum cholesterol. This review summarizes clinical trials of these compounds and their recent impact on stroke and explores the underlying vascular mechanisms of their actions.

SUMMARY OF REVIEW

Use of statins in patients with vascular disease has been shown to lower the incidence of stroke by approximately 30%. Statins exhibit a number of antiatherosclerotic and antithrombotic properties that likely underlie the recently observed reductions in cerebrovascular disease. Statins reduce inflammatory, proliferative, and thrombogenic processes in plaque, making it less likely to rupture. Additionally, they reverse the endothelial dysfunction and platelet activation accompanying hypercholesterolemia and may reduce the tendency to thrombosis.

CONCLUSIONS

Hypercholesterolemia has reemerged as a risk factor for ischemic stroke. Statins protect against thromboembolic stroke through multiple beneficial effects within the vascular milieu. Further data are awaited to support the growing importance of cholesterol as a risk factor for ischemic stroke and the benefits of statin therapy in patients with cerebrovascular disease.

Effect of evening primrose oil on platelet aggregation in rabbits fed an atherogenic diet

Evening primrose oil (Oenothera biennis) is a rich source of omega-6 series fatty acids. We report here the effects of dietary supplementation with evening primrose oil (EPO) on platelet aggregation as the main factor in arterial thrombus formation in an experimental model of atherogenesis in rabbits. A total of 40 male white New Zealand rabbits were divided into four groups (n = 10 animals/group): 1: normal diet, 2: atherogenic diet (ATD), 3: normal diet enriched with 15% EPO, 4: ATD + EPO. Each group was kept on the diet for 6 weeks. We determined serum lipid profile, platelet aggregation in whole blood, platelet thromboxane B2 production and platelet lipid peroxides. The atherogenic diet increased platelet aggregation (135% when ADP was used, and 185% when collagen was used as the inducer). Evening primrose oil reduced hyperaggregation to the values obtained in rabbits fed with the normal diet. Thromboxane synthesis was increased from 0.18 to 2.28 nmol/10(9) platelets); EPO reduced this value to 1.38 nmol/10(9) platelets. Lipid peroxides were increased by ATD from 0.27 to 0.81 nmol/10(8) platelets; EPO prevented this increase (0.35 nmol/10(8) platelets). In conclusion, EPO reduced platelet hyperaggregability in rabbits fed an atherogenic diet.

Platelet-dependent thrombin generation in patients with hyperlipidemia

OBJECTIVES

We evaluated coagulability as determined by platelet-dependent thrombin generation in hypercholesterolemic patients before and after treatment with pravastatin and in hypertriglyceridemic patients to investigate the usefulness of coagulability as an index of atherosclerosis and to determine the importance of treating hyperlipidemia.

BACKGROUND

An understanding of the interaction between platelets and the plasma coagulation system is important for clarifying the mechanism of the procoagulant process.

METHODS

We assessed coagulability in 58 patients with hypercholesterolemia (serum total cholesterol level > or = 220 mg/dl, age 56.5 +/- 1.5 years [mean +/- SEM]), 37 patients with hypertriglyceridemia (serum triglyceride level > or = 200 mg/dl, age 59.5 +/- 1.7 years), 13 patients with hypercholesterolemia plus hypertriglyceridemia (age 51.4 +/- 3.1 years) and 75 normal subjects (age 52.2 +/- 1.7 years). We also studied platelet-dependent thrombin generation in patients with hypercholesterolemia before and after treatment with pravastatin. Calcium chloride was added to 0.5 ml of platelet-rich plasma (150 x 10(9)/liter) to initiate coagulation. Ten microliters of the sample was transferred into 90 microliters of 3.8% sodium citrate at 10-min intervals for 30 min. A chromogenic substrate, S-2238, was added to each sample, and absorbance was measured spectrophotometrically at a wavelength of 405 nm to determine thrombin generation.

RESULTS

Platelet-dependent thrombin generation was increased in patients with hypercholesterolemia and patients with hypercholesterolemia plus hypertriglyceridemia (p < 0.01) compared with patients with hypertriglyceridemia and control subjects. Treatment with pravastatin normalized thrombin generation.

CONCLUSIONS

Hypercholesterolemia, but not hypertriglyceridemia, was associated with increased platelet-dependent thrombin generation. Pravastatin normalized the generation of thrombin.

Alteration of lymphocyte membrane phospholipids and intracellular free calcium concentrations in hyperlipidemic subjects

Hypercholesterolemia has been proposed to influence cell functions via changes in membrane composition. The aim of the present study was to determine whether the membrane phospholipid composition of human lymphocytes is modified in hypercholesterolemia and whether these changes are accompanied by functional modifications. The phospholipid fatty acid contents and intracellular free calcium concentrations were determined in peripheral blood lymphocytes from 13 subjects with serum total cholesterol levels ranging from 4.6 to 8.8 mmol/l. The spontaneous basal rate of thymidine incorporation in lymphocyte of hypercholesterolemic individuals increased, while its relative stimulation by ConA was less effective. Important changes in membrane lipid composition, consisting mainly of decrease of the mass of phospholipids, and of associated polyunsaturated fatty acids were observed in hypercholesterolemia. In contrast, the cell cholesterol content was significantly increased. The intracellular free calcium concentration was enhanced and strongly associated with circulating cholesterol levels, cell cholesterol content and phospholipid fatty acids. These results indicate that hypercholesterolemia is accompanied by profound changes in lymphocyte membrane lipid composition and Ca(2+) handling.

Platelet-dependent thrombin generation in patients with diabetes mellitus: effects of glycemic control on coagulability in diabetes

OBJECTIVES

This study sought to assess the usefulness of platelet-dependent thrombin generation as an index of coagulability in diabetes and to determine the effect of glycemic control on coagulability in diabetes.

BACKGROUND

It is important to investigate the interaction of platelets and the coagulation factors to clarify the processes of the coagulation system in detail.

METHODS

Platelet-rich plasma (150 X 10(9)/liter), 0.5 ml, was prepared, and 40 mmol/liter of calcium chloride was added to initiate clotting. S-2238 was added to each sample in a microtiter plate every 10 min, and the absorbance of the released color product at 2 min was measured spectrophotometrically at a wavelength of 405 nm using a microtiter plate reader as thrombin generation. We measured the platelet-independent thrombin generation in patients with non-insulin-dependent diabetes mellitus grouped according to glycemic control.

RESULTS

Platelet-dependent thrombin generation at 30 min after calcium chloride addition was significantly higher in 23 patients with poorly glycemic-controlled non-insulin-dependent diabetes mellitus without complications, such as diabetic retinopathy, nephropathy and neuropathy (hemoglobin [Hb] A1c >/= 9.0%) than in 46 healthy normal subjects (448 +/- 75 vs. 165 +/- 28 mU/min, p < 0.001). Thrombin generation in 31 well controlled diabetic patients without complications (Hb A1c < 9.0%) was intermediate (240 +/- 72 mU/min) between those of the poorly controlled group and healthy normal subjects. Platelet-poor plasma from diabetic patients increased platelet-dependent thrombin generation in normal subjects.

CONCLUSIONS

Coagulability is evidently enhanced in patients with non-insulin-dependent diabetes mellitus compared with that in healthy normal subjects on the basis of assessments of the platelet-dependent thrombin generation, and good glycemic control may help to correct a hypercoagulable state in diabetic patients.

Platelet cytosolic Ca2+ and membrane dynamics in patients with primary hypercholesterolemia. Effects of pravastatin

This study was designed to evaluate the relationships between platelet cytosolic Ca2+ concentration ([Ca2+]i) and plasma lipids in patients with primary hypercholesterolemia. In a double-blind, placebo-controlled trial, we determined platelet [Ca2+]i in the presence and virtual absence of extracellular Ca2+ and the effects of prolonged treatment with pravastatin, a selective inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase. Platelet [Ca2+]i and membrane microviscosity were determined in 22 normotensive hypercholesterolemic men. Platelet [Ca2+]i was observed to vary with in vivo plasma lipid characteristics: in untreated patients, [Ca2+]i determined at low extracellular Ca2+ concentration was significantly associated with plasma triacylglycerols (P = .008) and with the total cholesterol to HDL cholesterol ratio (P = .044). Triacylglycerol levels also correlated inversely with the external Ca(2+)-dependent [Ca2+]i rise. Pravastatin treatment reduced plasma total cholesterol (-20 +/- 3%), LDL cholesterol (-30 +/- 3%), triacylglycerols (-17 +/- 6%), and apoB levels (-25 +/- 4%) and simultaneously decreased platelet [Ca2+]i measured in a low-Ca2+ medium by 14 +/- 6% (P = .03). However, [Ca2+]i values remained positively correlated with the total cholesterol to HDL cholesterol ratio (P = .04). Prvastatin treatment did not induce marked changes in membrane microviscosity, although the changes in trimethylaminodiphenylhexatriene anisotropy were inversely correlated with those of HDL cholesterol. These results indicate that plasma lipids can modulate cytosolic Ca2+ in platelets by affecting Ca2+ transport pathways that are dependent and independent of Ca2+ influx.