Effects of increased concentrations of glucose on platelet reactivity in healthy subjects and in patients with and without diabetes mellitus

Aspirin in the prevention of cardiovascular events in patients with diabetes

Diabetes imparts a substantial increased risk for cardiovascular disease-related mortality and morbidity. Because of this, current medical guidelines recommend prophylactic treatment with once-daily, low-dose aspirin (acetylsalicylic acid) for primary and secondary prevention of cardiovascular (CV) events in high-risk patients. However, only modest reductions in CV events and mortality have been observed with once-daily aspirin treatment in patients with diabetes, including patients with a previous CV event, perhaps because of disparity between aspirin pharmacokinetics and diabetes-related platelet abnormalities. Once-daily aspirin irreversibly inactivates platelets for only a short duration (acetylsalicylic acid half-life, approximately 15-20 minutes), after which time newly generated, active platelets enter the circulation and weaken aspirin's effect. Platelets from patients with diabetes are more reactive and are turned over more rapidly than platelets from normal individuals; the short inhibitory window provided by once-daily aspirin may therefore be insufficient to provide 24-h protection against CV events. Alternative conventional aspirin regimens (e.g. higher daily dose, twice-daily dosing, combination with clopidogrel) and newer formulations (e.g. 24-h, extended-release) have been proposed to overcome the apparent limited efficacy of conventional aspirin in patients with diabetes; however, tolerability concerns and limited clinical efficacy data need to be taken into account when considering the use of such regimens.

The Influence of Haemoglobin A1c Levels on Platelet Aggregation and Platelet Turnover in Patients with Coronary Artery Disease Treated with Aspirin

Background

Hyperglycaemia may attenuate the antiplatelet effect of aspirin and thereby increase the risk of cardiovascular events. We investigated the influence of increased haemoglobin A1c (HbA1c) levels on platelet aggregation and turnover in a large cohort of patients with coronary artery disease (CAD) with type 2 diabetes, prediabetes or no diabetes.

Methods

In this observational study, we included 865 stable CAD patients on 75 mg aspirin as mono-therapy of whom 242 patients had type 2 diabetes and were receiving antidiabetic drugs. Among 623 patients without diabetes, we classified 303 patients with prediabetes (HbA1c ≥5.7–6.4% [39–47 mmol/mol]) naive to antidiabetic drugs. Platelet aggregation was evaluated by the Multiplate Analyzer using arachidonic acid and collagen and by the VerifyNow Aspirin. Platelet turnover was evaluated by immature platelets using flow cytometry and platelet activation by soluble P-selectin.

Results

CAD patients with type 2 diabetes had higher platelet aggregation (all p-values <0.01), platelet turnover (immature platelet count, p<0.01) and platelet activation (p<0.001) than patients without diabetes. CAD patients with prediabetes had increased platelet aggregation (p = 0.02) and platelet count (p = 0.02) compared with patients without diabetes. Increased levels of HbA1c correlated positively with increased platelet aggregation using arachidonic acid (r = 0.19, p<0.0001), collagen (r = 0.10, p<0.01) and VerifyNow (r = 0.15, p<0.0001), and with platelet count (r = 0.08, p = 0.01), immature platelet count (r = 0.11, p<0.001) and soluble P-selectin (r = 0.15, p<0.0001). These associations were mainly evident in non-diabetic and prediabetic CAD patients.

Conclusions

CAD patients with prediabetes and diabetes may have attenuated antiplatelet effect of aspirin compared with CAD patients without diabetes. This may be related to increased platelet count in patients with prediabetes. Increased levels of HbA1c correlated positively, though weakly, with increased platelet aggregation, platelet turnover and platelet activation.

High-risk type-2 diabetes mellitus patients, without prior ischemic events, have normal blood platelet functionality profiles: a cross-sectional study

Background

Patients with type 2 diabetes mellitus (DM) display a predisposition for vascular disease. Platelets taken from vasculopathic diabetic patients, show enhanced stimuli-induced activation and aggregation responses. Aspirin remains the cornerstone antiplatelet agent for secondary prevention of vascular complications among diabetic patients, yet evidence of its efficacy and safety in primary prevention are conflicting. Our aim was to assess whether high risk diabetic patients, without previous ischemic events, have abnormal platelet functionality profiles.

Methods

The study included 82 diabetic patients and 86 matched non-diabetic patients without prior ischemic events nor treatment with anti-platelet medications. Blood samples were analyzed for platelet markers of activation, turnover and leukocyte-platelet interactions.

Results

Our final analysis included 122 males (74 %), with a mean age of 61 years. Mean platelet volume (MPV) was similar between the diabetic patients and controls (9.2 fL for both). Following activation, PAC-1 binding and P-selectin expression were found comparable between the diabetic patients and controls (83 % versus 81 % and 76 % versus 74 %, respectively). Leukocyte-platelet aggregates (LPAs) were similar between the diabetic patients and controls (18 % versus 17 %, respectively). Neutrophil-platelet aggregates (NPAs) and monocyte-platelet aggregates (MPAs) were also found similar in the diabetic patients and controls. Elevated fasting plasma glucose was associated with increased LPAs rates.

Conclusions

High risk type-2 diabetes mellitus patients, without prior ischemic events, have normal blood platelet functionality profiles.

The mean platelet volume is significantly associated with higher glycated hemoglobin in a large population of unselected outpatients

AIMS

To examine the association between mean platelet volume (MPV) and glycated hemoglobin (HbA1c) in a large cohort of unselected outpatients.

METHODS

We retrospectively reviewed combined results of complete blood count (CBC) and hemoglobin A1c (HbA1c) performed in all outpatients aged 18 years or older, who were referred to the outpatient clinic of our hospital for routine health check-up during the year 2013.

RESULTS

Cumulative results of both CBC and HbA1c could be retrieved for 4072 male and female outpatients aged 18 years or older. There were significant associations between HbA1c and both MPV (r=0.10; p<0.001) and platelet count (r=0.05; p<0.001), that remained statistically significant after adjusting for age and sex. After stratifying the whole sample of patients for MPV quartiles, there was a significant, positive trend of HbA1c across quartiles of MPV (p<0.001). Similar findings were found when the whole sample was stratified by clinical thresholds of HbA1c (p<0.001), with values of MPV gradually increasing from subjects with normal glucose homeostasis, pre-diabetes and diabetes.

CONCLUSIONS

The results of our investigation, which is supposed to be the largest cohort study on unselected outpatients assessing the relationship between HbA1c and platelets number or size, indicate that elevated MPV is significantly associated with higher HbA1c levels and vice versa.

State-of-the-Art: Hypo-responsiveness to oral antiplatelet therapy in patients with type 2 diabetes mellitus

Diabetes mellitus is a global pandemic, associated with a high burden of cardiovascular disease. There are multiple platelet derangements in patients with diabetes, and antiplatelet drugs remain the first-line agents for secondary prevention as well as for high-risk primary prevention among patients with diabetes. This review provides a summary of oral antiplatelet drug hypo-responsiveness in patients with diabetes, specifically aspirin and Clopidogrel resistance. Topics discussed include antiplatelet testing, definitions used to define hypo-response and resistance, its prevalence, association with clinical outcomes and strategies to mitigate resistance. The role of prasugrel and ticagrelor, as well as investigational agents, is also discussed.

Role of multiligand/RAGE axis in platelet activation

In the context of plaque progression, platelet hyperactivity associated with hyperlipidemia contributes to the development of a pro-thrombotic state. In this context, it has been demonstrated that advanced glycation end products (AGEs) significantly increases platelet activation and receptor for AGEs (RAGE) expression at the platelet surface membrane. In addition to AGEs, other ligands (S100, HMGB1 and amyloid β, among others) of RAGE have raised particular attention in platelet activation. Therefore, in this article we describe platelet hyperactivity by AGEs via RAGE-independent and RAGE-dependent pathways.

Platelet turnover in stable coronary artery disease - influence of thrombopoietin and low-grade inflammation

Background

Newly formed platelets are associated with increased aggregation and adverse outcomes in patients with coronary artery disease (CAD). The mechanisms involved in the regulation of platelet turnover in patients with CAD are largely unknown.

Aim

To investigate associations between platelet turnover parameters, thrombopoietin and markers of low-grade inflammation in patients with stable CAD. Furthermore, to explore the relationship between platelet turnover parameters and type 2 diabetes, prior myocardial infarction, smoking, age, gender and renal insufficiency.

Methods

We studied 581 stable CAD patients. Platelet turnover parameters (immature platelet fraction, immature platelet count, mean platelet volume, platelet distribution width and platelet large cell-ratio) were determined using automated flow cytometry (Sysmex XE-2100). Furthermore, we measured thrombopoietin and evaluated low-grade inflammation by measurement of high-sensitive CRP and interleukin-6.

Results

We found strong associations between the immature platelet fraction, immature platelet count, mean platelet volume, platelet distribution width and platelet large cell ratio (r = 0.61–0.99, p<0.0001). Thrombopoietin levels were inversely related to all of the platelet turnover parameters (r = −0.17–−0.25, p<0.0001). Moreover, thrombopoietin levels were significantly increased in patients with diabetes (p = 0.03) and in smokers (p = 0.003). Low-grade inflammation evaluated by high-sensitive CRP correlated significantly, yet weakly, with immature platelet count (r = 0.10, p = 0.03) and thrombopoietin (r = 0.16, p<0.001). Also interleukin-6 correlated with thrombopoietin (r = 0.10, p = 0.02).

Conclusion

In stable CAD patients, thrombopoietin was inversely associated with platelet turnover parameters. Furthermore, thrombopoietin levels were increased in patients with diabetes and in smokers. However, low-grade inflammation did not seem to have a substantial impact on platelet turnover parameters.

Lactate is a possible mediator of the glucose effect on platelet inhibition

Abstract Glucose has been found to impair the inhibition of platelets with aspirin and alter the basal activity of nitric oxide synthase (NOS) in platelets. The aim of this work was to study the effects of glucose on the inhibitory pathways in activated platelets. A short-term incubation of glucose impaired the inhibition of platelet aggregation induced by agents activating an NOS-dependent pathway, such as l-arginine, adenosine and α-tocopherol. However, glucose had no effect on the inhibition induced by iloprost and BW245C, agents that activate the cyclic adenosine monophosphate (cAMP) signaling pathway. Potassium lactate attenuated the effects of the same inhibitors as glucose did. The inhibitors of glucose transport prevented the effect of glucose. Dichloroacetate, known to prevent the conversion of pyruvate to lactate and to decrease lactate in platelets, significantly attenuated the effect of glucose in platelets. The data support the suggestion that the effect of glucose on the inhibition of platelets by agents activating an NOS-dependent pathway is mediated by glucose metabolite lactate.

Mean platelet volume is independently associated with renal dysfunction in stable coronary artery disease

It has been suggested that athero-thrombotic risk progressively increases as the glomerular filtration rate (GFR) declines. Mean platelet volume (MPV) is the most commonly used measure of platelet size, and higher MPV value is independent risk factor for athero-thrombotic disease such as myocardial infarction. We aimed to evaluate the association between estimated GFR and MPV in patients with stable coronary artery disease showing normal to mildly impaired renal function. A total of 471 patients (288 males and 183 females; mean age: 62.5+9.5 years) with angiographically proven CAD were included. The patients were divided into two groups according to the estimated GFR value (GFRlow group: GFR <60 ml/minute per 1.73 m(2) and GFRhigh group: GFR ≥ 60, ml/min per 1.73 m(2)). Estimated GFR was calculated according to the Cockcroft-Gault formula. MPV, high-sensitive C-reactive protein (hsCRP) and other biochemical markers were measured in all patients. Prevalent of CAD was determined by the SYNTAX score. Patients with GFRlow group were of older age, had higher incidence of female gender, current smoker, diabetes, hypertension and hyperlipidemia, lower values of total cholesterol, LDL cholesterol, hemoglobin and platelet count and higher values of BMI, SYNTAX score, hs-CRP and MPV compared with patients with GFRhigh group. Multivariate linear regression analysis showed that the MPV was independently related with diabetes (β=0.189, p<0.001), eGFR (β=-0.267, p<0.001), hs-CRP level (β=0.158, p<0.001) and platelet count (β=-0.116, p=0.002). In conclusion, MPV is independently associated with GFR as well as hsCRP, platelet count and diabetes. These findings may explain, in part, the increase in athero-thrombotic risk with slightly impaired renal function.

Glucose intolerance and insulin resistance as predictors of low platelet response to clopidogrel in patients with minor ischemic stroke or TIA

The relation between high on-treatment platelet reactivity (HPR), and the level of glucose intolerance and insulin resistance (IR) was studied in clopidogrel-treated patients with minor ischemic stroke or TIA. The cohort consisted of 66 patients, 11 of which had known type 2 diabetes mellitus (DM). Platelet aggregation in whole blood (Multiplate™) and metabolic variables were measured 1 month after acute onset of neurological symptoms. Glucose tolerance was measured by Oral Glucose Tolerance Test (OGTT). IR was estimated by homeostasis model assessment HOMA-IR. Patients were categorized as "responders" (R) or "non-responders" (NR) to clopidogrel according to an established cut-off in platelet aggregation induced by adenosine diphosphate (ADP). In total, 14/66 (21%) patients were NR. Impaired glucose tolerance (IGT), impaired fasting glucose (IFG) or DM was seen in 13/14 NR (93%), while for R this was the case in 25/52 (48%), p = 0.001. The percentage of NR was 33% in patients with DM and 35% in patients with IGT or IFG. In the group with normal glucose tolerance (NGT) the percentage of NR was low, 4% (1/28). Fasting plasma glucose (f-PG) was higher for NR than for R, 6.0 (5.5-6.7) mM vs. 5.3 (5.0-6.0) mM, p = 0.023. Glycated hemoglobin (HbA1c) did not differ between NR and R. NR also had higher arachidonic acid-induced platelet aggregation than R, and a tendency towards higher aggregation induced by thrombin receptor agonist peptide (TRAP), indicating that HPR reflects a global platelet hyper-reactivity. HOMA-IR was calculated for 52 of the patients above without known diabetes, 9 of which were NR (17%). NR were significantly more insulin resistant than R, with median HOMA-IR 4.5 (3.0-7.4) compared to 2.1 (1.5-3.2) for R, p = 0.001. HOMA-IR and fasting plasma insulin were the only metabolic variables with significant relationships to ADP-induced platelet aggregation. The results suggest that HPR develops in the pre-diabetic phase. A metabolic disturbance with glucose intolerance and/or high level of IR was a pre-requisite for HPR in the tested cohort. Conversely, normal glucose tolerance combined with normal or mildly elevated HOMA-IR excluded HPR. NR are likely to constitute a high-risk group among patients with ischemic cerebrovascular disease. Measurement of f-PG or HbA1c is insufficient to identify NR, while OGTT and HOMA-IR are more predictive.

Platelet function profiles in patients with diabetes mellitus

Patients with diabetes mellitus (DM) are at high risk for several cardiovascular disorders such as coronary heart disease, stroke, peripheral arterial disease, and congestive heart failure. DM has reached epidemic proportions and its strong association with coronary artery disease is responsible for increased cardiovascular morbidity and mortality. DM patients are characterized by platelet hyperreactivity, which contribute to the enhanced atherothrombotic risk of these subjects. Several mechanisms are involved in the hyperreactive platelet phenotype characterizing DM patients. Furthermore, a large proportion of DM patients show inadequate response to standard antiplatelet treatments and high rate of adverse recurrent cardiovascular events despite compliance with standard antiplatelet treatment regimens. Therefore, new antiplatelet treatment regimens are warranted in DM patients to reduce their atherothrombotic risk. The present manuscript provides an overview on the current status of knowledge on platelet function profiles in patients with DM and therapeutic considerations.

Mean Platelet Volume Associated With Aortic Distensibility, Chronic Inflammation, and Diabetes in Patients With Stable Coronary Artery Disease

We aimed to assess the effective factors on high mean platelet volume (MPV) in patients with stable coronary artery disease (CAD). A total of 411 patients (247 males and 164 females; mean age: 61.7 ± 9.9 years) with angiographically proven CAD were included. The patients were divided into 2 groups according to the median MPV value (MPVlow group <9.5 fL and MPVhigh group ≥9.5 fL). The SYNTAX score, high sensitive C-reactive protein (hsCRP) levels, and frequencies of diabetes and hypertension were higher in MPVhigh group compared to MPVlow group. Aortic distensibility (AD) and platelet count of patients in MPVhigh group were lower than patients in MPVlow group ( P < .05, for all). Multivariate linear regression analysis showed that MPV was independently related with diabetes (β = 0.135, P = .007), hsCRP (β = 0.259, P < .001), platelet count (β = −0.144, P < .001), and AD (β = −0.425, P < .001). High MPV value is independently related to AD, as well as diabetes, hsCRP, and platelet count in patients with stable CAD.

Association of Mean Platelet Volume and Pre- and Postinterventional Flow With Infarct-Related Artery in ST-Segment Elevation Myocardial Infarction

Platelets play a role in the pathogenesis of ST-segment elevation myocardial infarction (STEMI). We assessed the relationship between mean platelet volume (MPV) on admission and pre- and postinterventional flow with the infarct-related artery (IRA) in patients with STEMI. We prospectively included 840 patients with STEMI who underwent primary percutaneous coronary intervention (PCI). The patients were divided into 3 groups according to MPV tertiles. Pre- and post-PCI Thrombolysis In Myocardial Infarction (TIMI) flow grade was determined. Initial TIMI flow grade 3 was accepted as patent IRA. After the primary PCI, normal flow was defined as post-PCI TIMI flow 3. When the MPV was increased, the incidence of pre-PCI patent IRA ( P = .004) and post-PCI normal TIMI flow ( P < .001) was significantly decreased. Multivariate analysis showed that MPV was independently associated with post-PCI TIMI flow grade.

Effect of glycemic control on response to antiplatelet therapy in patients with diabetes mellitus and ST-segment elevation myocardial infarction

Impaired glycemic control (GC) is a troubling clinical condition with an unclear prognostic value that is frequent in diabetics, especially in the setting of acute coronary syndrome. Residual platelet reactivity can be also affected by GC. We evaluated the relation between response to dual antiplatelet therapy and GC in diabetics with STEMI treated with primary coronary angioplasty (PCI). Sixty diabetic patients were prospectively enrolled in the study. All patients were treated with clopidogrel and aspirin. Platelet reactivity (whole blood aggregation and phosphorylation of vasodilator-stimulated phosphoprotein, VASP) were assessed serially before and 24 hours, 7 days, and 30 days after the PCI. Blood glucose >8.5 mmol/L on admission was an independent predictor of a impaired clopidogrel response measured with platelet reactivity index (PRI) >50% on admission (OR 7.8, 95% CI 1.4-17.7, p<0.02) and 24 hours after PCI (OR 13.1, 95% CI 3.4-28.1, p<0.01). In conclusion, diabetic patients with STEMI and glycemia >8.5 mmol/L on admission is related to a poorer response to clopidogrel. There were no interaction between glycated hemoglobin level or glycemia on admission and platelet reactivity measured with collagen, arachidonic acid or thrombin receptor agonist peptide-induced aggregation. Further clinical studies of the role of GC in the efficacy of antiplatelet agents are warranted.

Advanced glycation end products induce a prothrombotic phenotype in mice via interaction with platelet CD36

Diabetes mellitus has been associated with platelet hyperreactivity, which plays a central role in the hyperglycemia-related prothrombotic phenotype. The mechanisms responsible for this phenomenon are not established. In the present study, we investigated the role of CD36, a class-B scavenger receptor, in this process. Using both in vitro and in vivo mouse models, we demonstrated direct and specific interactions of platelet CD36 with advanced glycation end products (AGEs) generated under hyperglycemic conditions. AGEs bound to platelet CD36 in a specific and dose-dependent manner, and binding was inhibited by the high-affinity CD36 ligand NO(2)LDL. Cd36-null platelets did not bind AGE. Using diet- and drug-induced mouse models of diabetes, we have shown that cd36-null mice had a delayed time to the formation of occlusive thrombi compared with wild-type (WT) in a FeCl(3)-induced carotid artery injury model. Cd36-null mice had a similar level of hyperglycemia and a similar level of plasma AGEs compared with WT mice under this condition, but WT mice had more AGEs incorporated into thrombi. Mechanistic studies revealed that CD36-dependent JNK2 activation is involved in this prothrombotic pathway. Therefore, the results of the present study couple vascular complications in diabetes mellitus with AGE-CD36-mediated platelet signaling and hyperreactivity.

The relationship between levels of von Willebrand factor and mean platelet volume in subjects with isolated impaired fasting glucose

Background

To understand the heterogeneity of platelets, we investigated the correlation between von Willebrand factor (vWf) and mean platelet volume (MPV) in subjects with isolated impaired fasting glucose (IFG).

Material/Methods

We selected 48 subjects with isolated IFG and 48 normoglycemic control subjects matched for age, sex, and body mass index. We measured levels of vWf and MPV in all subjects.

Results

The levels of vWf and MPV were significantly higher in the isolated IFG group than the control group (p<0.05) Also, vWf level was positively correlated with MPV level in subjects in the isolated IFG group (r=0.452, p=0.001).

Conclusions

Our results suggest that vWf seems to be profoundly related to platelet volume in subjects with isolated IFG.

Platelet function in patients with diabetes mellitus: from a theoretical to a practical perspective

Patients with diabetes mellitus have an increased prevalence of vascular disease. Pathologic thrombosis associated with atherosclerotic plaque rupture is a major cause of morbidity and mortality. Platelets are intimately involved in the initiation and propagation of thrombosis. Evidence suggests that platelets from patients with type 2 diabetes have increased reactivity and baseline activation compared to healthy controls. We review the pathophysiology of platelet hyperreactivity in DM patients and its implications in clinical practice, with particular focus on acute coronary syndromes, percutaneous coronary intervention, and novel antiplatelet agents.

Platelet abnormalities in diabetes mellitus

Patients with diabetes mellitus (DM) have accelerated atherosclerosis, which is the main underlying factor contributing to the high risk of atherothrombotic events in these patients. Atherothrombotic complications are the leading cause of morbidity and mortality in patients with DM. Among factors contributing to the prothrombotic condition which characterise patients with DM, platelet hyperreactivity plays a pivotal role. Platelets of DM patients are characterised by dysregulation of several signalling pathways leading to intensified adhesion, activation and aggregation. Multiple mechanisms are involved in platelet dysfunction of patients with DM, which can be categorised as follows: a) hyperglycaemia, b) insulin deficiency and resistance, c) associated metabolic conditions, and d) other cellular abnormalities.The present manuscript aims to provide an overview on the current status of knowledge on platelet abnormalities that characterise patients with DM.

Mean platelet volume is associated with insulin resistance in non-obese, non-diabetic patients with coronary artery disease

BACKGROUND AND PURPOSE

Mean platelet volume (MPV), an indicator of platelet activation, has been shown to be elevated in patients with coronary artery disease (CAD) in some studies. Insulin resistance contributes to increased platelet activation and it is one of the risk factors for CAD. The aim of this study was to assess the relationship between insulin resistance and MPV in non-obese, non-diabetic patients with CAD.

METHODS AND SUBJECTS

Seventy-seven non-obese, non-diabetic CAD patients were divided into two groups, insulin resistant and insulin sensitive according to the homeostasis model assessment insulin resistance index (HOMA-IR). The insulin-resistant group was composed of 45 patients (30 males/15 females; mean age 59.8±11.1 years). The insulin-sensitive group was composed of 32 patients (17 males/15 females; mean age 58.9±12.2 years).

RESULTS

Insulin and HOMA-IR values were significantly higher in insulin-resistant CAD patients than in insulin-sensitive CAD patients. The MPV values were significantly higher in insulin-resistant CAD patients than in insulin-sensitive CAD patients (8.6±1.0 fl vs. 8.0±0.7 fl; respectively, p=0.01). The MPV was poorly correlated with HOMA-IR (r=0.30, p=0.054) and insulin (r=0.22, p=0.053).

CONCLUSIONS

We have shown that MPV was significantly elevated in insulin-resistant non-obese, non-diabetic CAD patients when compared to insulin-sensitive non-obese, non-diabetic CAD patients.

Acute coronary thrombosis in a patient with diabetes and severe hyperglycemia

The pathophysiological processes responsible for acute coronary events in diabetic patients, in addition to the conventional factors associated with plaque rupture, include an enhanced prothrombotic state. This enhanced prothrombotic state results from multiple abnormalities of the coagulation system including platelet activation, impaired fibrinolysis and increased activity of the coagulation cascade. Studies have also demonstrated that severe hyperglycemia can result in an exacerbation of the underlying pro-thrombotic state, indicating that patients with extreme hyperglycemia are subject to an even greater thrombotic risk. The present case illustrates the thrombotic hazards associated with severe hyperglycemia.

Inhibition of platelet GPIIb-IIIa and P-selectin expression by aspirin is impaired by stress hyperglycemia

Increased aspirin resistance may contribute to the increase in thrombotic events observed in patients with type 2 diabetes. In this study, we examined if acute exposure to increased plasma glucose impaired the inhibitory effects of aspirin on platelet activation. Whole-blood samples were incubated with 100 (euglycemia), 200, 300, and 600 mg/dl glucose followed by incubation with aspirin [acetylsalicylic acid (ASA)]. Using flow cytometry, GPIIb-IIIa and P-selectin were analyzed in unstimulated and arachidonic acid (AA)-stimulated platelets. In euglycemic blood, AA caused a significant increase in platelet GPIIb-IIIa expression [unstimulated: 59.5+/-8.2 total fluorescence intensity (TFI), AA stimulated: 319.6+/-42.7 TFI, P=.002] and P-selectin (4.4+/-0.7 and 179.5+/-38.5 TFI, P<.001). In vitro, ASA significantly inhibited both GPIIb-IIIa expression (36.5%) and P-selectin expression (81%; P<.005). However, increased blood glucose (200 mg/dl) significantly impaired the inhibitory effect of ASA (84% for GPIIb-IIIa, P<.005; 48% for P-selectin, P=NS). Increasing glucose to 600 mg/dl completely overwhelmed the inhibitory effect of ASA. A statistically significant interaction between glucose concentration and ASA dose was found (P<.001 for GPIIb-IIIa and P=.004 for P-selectin). In vitro, concentration-dependent stress hyperglycemia significantly impaired the inhibitory effects of aspirin on human platelet GPIIb-IIIa and P-selectin expression. Under acute hyperglycemic conditions, the effectiveness of ASA to inhibit platelets via the AA-activation pathway may be significantly reduced.

Metabolic syndrome is a predictor for an ECG sign of no-reflow after primary PCI in patients with acute ST-elevation myocardial infarction

BACKGROUND AND AIM

The purpose of this study was to evaluate both the predictive value of metabolic syndrome (MS) on no-reflow phenomenon and 30-day clinical outcomes on patients undergoing primary percutaneous coronary intervention (PCI) for acute ST-elevation myocardial infarction (STEMI).

METHODS AND RESULTS

One hundred and twelve consecutive patients (mean age 57+/-11 years, 94 male) with acute STEMI treated with primary PCI were analysed prospectively. Sum of ST-segment elevation was obtained immediately before and 60 min after the restoration of TIMI-3 flow. The difference between two measurements was accepted as the amount of ST-segment resolution and was expressed as summation operatorSTR. summation operatorSTR<50% was accepted as ECG sign of no-reflow phenomenon. Metabolic syndrome was defined based on Adult Treatment Panel-III criteria. The no-reflow was found in 22.3% of the entire group and was significantly higher in patients with MS than those without MS (43.7% vs. 13.7%, p<0.001). There was no significant difference in no-reflow between patients who had both MS and diabetes mellitus (DM) and patients who had MS but not DM (42.5% vs. 50%, respectively; p>0.05).

CONCLUSION

The presence of MS may play an important role in the occurrence of no- reflow in STEMI treated with primary PCI.

Cardiovascular risk factors are reduced with a low dose of acarbose in obese patients with polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is defined by menstrual irregularity, hyperandrogenism, chronic anovulation, and enlarged ovaries with multiple follicles. Polycystic ovary syndrome is highly prevalent in women, affecting up to 10% of all women of reproductive age and reducing the possibility of spontaneous conception. In addition to altering reproductive function, PCOS has systemic implications, especially in the cardiovascular system. Cardiovascular risk (CVR) in PCOS patient increases because of insulin resistance, elevated androgen levels, and association with obesity. Those alterations promote cardiovascular risk factors, such as endothelial dysfunction, elevated homocysteine levels, left ventricular hypertrophy, and reduced high-density lipoprotein (HDL) cholesterol (1).

Mean platelet volume in patients with metabolic syndrome and its relationship with coronary artery disease

BACKGROUND

Mean platelet volume (MPV) is an indicator of platelet activation which is a central process in the pathophysiology of coronary heart disease. The metabolic syndrome (MS) is characterized as the clustering of closely associated and interdependent atherosclerotic risk factors. MS has also been shown to be strongly associated with poor outcome in patients with coronary artery disease (CAD). The present study was designed to investigate MPV values in patients MS and to interrogate the association with CAD.

METHODS

We measured MPV in 205 consecutive patients with metabolic syndrome (mean age, 53+/-7 years) and 140 control subjects without metabolic syndrome (mean age, 52+/-6 years). All patients were selected from individuals who underwent coronary angiography in our hospital with a suspicion of coronary artery disease. To evaluate the severity of coronary artery disease, the patients with MS were subdivided depending upon the coexistence of coronary artery disease: normal coronary arteries, having coronary stenotic lesions of <50%, and having coronary stenotic lesions of >50%.

RESULTS

The MPV was significantly higher in patients with MS than in the control group (10.19+/-1.49 fl vs 8.21+/-1.02 fl, p<0.001). According to the CAD severity, there were no statistically significant differences in MPV among these subgroups.

CONCLUSION

We have shown for the first time that patients with MS have higher MPV compared to control subjects with normal coronary angiograms and to be associated with CAD. Hence MPV can be used as a follow up marker in patients with MS in the point of CAD.

Ancillary studies in the Bypass Angioplasty Revascularization Investigation 2 Diabetes (BARI 2D) Trial: Synergies and opportunities

The definitive power of randomized controlled trials (RCTs) to characterize the efficacy of putative therapeutic approaches cannot be overestimated. Such trials are expensive, and their implementation requires prolonged and intensive commitments by both investigators and subjects. Accordingly, enhancing their value, in a sense increasing the "scientific return on investment," is a laudatory objective. Ancillary studies afford a great opportunity to do so. They permit acquisition of new knowledge, elucidation of cause/consequence relation, and delineation of pathogenetic mechanisms at a much lower cost than would be possible if they were performed independently of the parent RCTs. In addition, their utility is enhanced by internal consistency under the rubric of the parent trial and the presumed external validation of the parent trial. Several ancillary studies undertaken in conjunction with the Bypass Angioplasty Revascularization Investigation 2 Diabetes (BARI 2D) trial provide cogent examples. They seek to delineate causal connections linking the accelerated coronary disease typical of diabetes with phenomena such as genetic predisposition to altered expression of cytokines and fibrinolytic system proteins, inflammation, procoagulation, insulin-induced impairment of fibrinolysis, insulin resistance, and the response to insulin-sensitizing and insulin-providing treatment strategies.

Inhibitory effects of cardiotonic pills on platelet function in dogs fed a high-fat diet

Insulin resistance and the consequent metabolic disorders are associated with a state of platelet hyperactivity. Oxidative stress is responsible for the persistent platelet activation. We sought to study the inhibitory effect of cardiotonic pills, an oral herbal component, on platelet function in a dog model with insulin resistance induced by high-fat feeding. We fed 18 dogs with a high-fat diet and six dogs with normal chow as control for 6 months. Then, six dogs were fed with a high-fat diet and received additional aspirin (250 mg/day), and another six dogs received additional cardiotonic pills (1,000 mg/day) for 4 months. Time-course changes in metabolic parameters and platelet function were detected. After high-fat feeding for 6 months, 18 dogs developed a series of metabolic disorders including obesity, dyslipidemia, oxidative stress and insulin resistance. In addition, a platelet hyperactivity state, characterized by increased agonist (arachidonic acid, ADP and collagen) induced platelet aggregation, platelet expression of adhesion molecules (P-selectin and GP IIb/IIIa), and platelet intracellular calcium concentration, was indicated. Cardiotonic pills showed a significant antioxidative activity by presenting an increase in plasma superoxide dismutase and decrease in erythrocyte glutathione, as well as a lipid-lowering effect (decrease in both plasma cholesterol and triglyceride). Either aspirin or cardiotonic pills could significantly reverse the platelet hypersensitivity and hyperfunction. Compared with aspirin, cardiotonic pills showed a more exaggerated inhibitory effect on platelet function (a significantly decreased collagen-stimulated platelet aggregation, and expression of adhesion molecules). In conclusion, cardiotonic pills inhibited platelet hyperfunction in dogs with insulin resistance. This inhibitory effect may mainly be explained by antioxidative activity and metabolic control.

Abnormalities of coagulation, platelet function, and fibrinolysis associated with syndromes of insulin resistance

Insulin resistance that accompanies obesity, hypertension, polycystic ovary syndrome, and the early phases of type 2 diabetes is characterized by a prothrombotic state. The prothrombotic state is a reflection of the direct effects of hyperinsulinemia and associated metabolic abnormalities (postprandial hyperglycemia, increased free fatty acids, and hypertriglyceridemia) on platelets, coagulation, and fibrinolysis. Therapies that improve insulin sensitivity and thereby decrease insulin resistance, hyperinsulinemia, and metabolic abnormalities decrease the prothrombotic state.

Integrated Management of Patients with Diabetes Mellitus and Ischemic Heart Disease: PCI, CABG, and Medical Therapy

Modern coronary revascularization strategies are based on studies performed in the 1970s and 1980s that compared coronary artery bypass surgery with standard medical therapy available at the time. Studies comparing surgical and percutaneous revascularization followed, demonstrating similar long-term outcome among thousands of randomized patients. The largest of these trials, the Bypass Angioplasty Revascularization Investigation (BARI), cast doubt on the generalizability of these findings to all subgroups, finding that patients with diabetes mellitus and multivessel disease had worse long-term outcome with an initial strategy of percutaneous transluminal coronary angioplasty (PTCA). Indeed, patients with diabetes mellitus are at increased risk for cardiovascular morbidity and mortality, while the benefit of standard therapies in these patients is attenuated by the underlying metabolic abnormalities and significant comorbidities associated with the diabetic state. However, surgical and percutaneous revascularization techniques continue to evolve. Similarly, modern medical therapy is markedly superior to that available during these early studies, with demonstrable benefit in primary and secondary prevention of vascular events in both diabetic and nondiabetic patients. Ongoing trials will define the impact of current treatment modalities in this important and growing population.

Type 2 diabetes mellitus: a cardiovascular perspective

Diabetes mellitus is a disease, which is at the epitome of cardiovascular risk factors causing considerable morbidity and mortality. In addition to microvascular complications, there is two- to six-fold increased risk of macrovascular diseases, such as coronary artery disease, peripheral artery disease and stroke. While the mortality from coronary artery disease in patients without diabetes has declined over the past 20 years, the mortality in men with type 2 diabetes mellitus has not changed. Furthermore, the prevalence of diabetes in the UK has increased by 30% since 1991 and the same among the world population in 2010 is expected to be twice in 1990. This dramatic increase has serious implications from a cardiovascular perspective and thus the aggressive management of blood pressure, dyslipidaemia and blood glucose in diabetes is of vital importance. The aim of this review is to evaluate the current evidence and to discuss the implications of type 2 diabetes and its relevance to clinical practice in cardiology. We address this broad subject in discussing (i) the pathophysiology of cardiovascular disease in the setting of type 2 diabetes and (ii) the prevalence of cardiovascular risk, complications and prognostic implications in type 2 diabetes, with a discussion of current therapeutic interventions for the prevention or delay of these consequences where relevant.

Platelet function, coagulopathy, and impaired fibrinolysis in diabetes

Diabetes and the metabolic syndrome, including insulin resistance, that underlies it are hyper-coagulable states. Increased platelet reactivity,augmented activity of the coagulation system,and impaired fibrinolysis are characteristic and understood to a remarkable extent. In aggregate,these derangements contribute to accelerated atherosclerosis, premature coronary artery dis-ease, and a profound toll from both.

Relation of augmented platelet reactivity to the magnitude of distribution of atherosclerosis

The extent of luminal involvement of atherosclerotic vascular disease and platelet reactivity portend subsequent cardiovascular events. This study was designed to determine whether platelet reactivity correlates with the extent of the territorial distribution of vascular disease. Blood was obtained from 130 patients who had known atherosclerotic vascular disease categorized as being in > or =1 of the following territories: coronary artery disease (CAD; n = 89), cerebrovascular disease (n = 36), and peripheral arterial disease (n = 61). Platelet reactivity, i.e., the activation of platelets in response to a low concentration of adenosine diphosphate (0.2 micromol/L), was measured using flow cytometry. Patients with vascular disease in >1 territory compared with those with disease in only 1 territory had greater platelet reactivity with respect to P-selectin expression (p = 0.01). The percentages of platelets expressing P-selectin (mean +/- SD) were 6.4 +/- 4.2 in patients who had involvement of 1 territory (n = 88), 10.0 +/- 6.8 in those who had involvement of 2 territories (n = 28), and 10.1 +/- 9.9 in those who had involvement of 3 territories (n = 14). Patients who had CAD and diabetes mellitus had greater P-selectin expression than did those who had CAD without diabetes (p <0.02 for interaction). Thus, platelet reactivity is greater in patients who have more extensive territorial distribution of atherosclerotic vascular disease and in those who have CAD and diabetes mellitus. Accordingly, patients who have more widely distributed vascular disease are likely to derive particular benefit from antiplatelet regimens that suppress platelet function to a greater extent.