Platelet reactivity and response to aspirin in subjects with the metabolic syndrome

Acetylsalicylic Acid (Aspirin) for Primary Prevention of Cardiovascular Events in Patients with Diabetes: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

BACKGROUND

Evidence regarding using acetylsalicylic acid (aspirin) for the prevention of cardiovascular (CV) events in patients with diabetes mellitus (DM) is inconsistent. Therefore, we performed a meta-analysis.

METHODS

A literature search was performed (January 1990 to February 2022) and publications meeting the inclusion criteria were reviewed, and a meta-analysis was performed using RevMan software. The primary outcome was a composite of CV death, non-fatal myocardial infarction (MI) and stroke. Secondary outcomes included all-cause mortality, individual components of the primary outcome and major bleeding.

RESULTS

The study cohort comprised 33525 diabetic patients from 9 randomized controlled trials. The primary outcome was significantly lower for aspirin vs. placebo (7.9 vs. 8.6, RR (risk ratio) 0.92, 95% CI (confidence interval) 0.86-0.99). All-cause mortality (10 vs. 10.3%, RR 0.97, 95% CI 0.90-1.03), CV death (4.4 vs. 4.7%, RR 0.93, 95% CI 0.83-1.04), non-fatal MI (4.6 vs. 4.8% RR 0.97, 95% CI 0.83- 1.15) and stroke (3.2 vs. 3.5%, RR 0.89, 95% CI 0.75-1.06) were similar between the two treatment groups. Major bleeding was significantly higher for aspirin compared with placebo (3.4 vs. 2.8%, RR 1.18, 95% CI 1.01-1.39).

CONCLUSION

Aspirin use in patients with DM reduces the composite endpoint of CV death, non-fatal MI and stroke compared with a placebo. However, routine use of aspirin for primary prevention among diabetic patients cannot be advised due to the increased risk of major bleeding. These findings suggest careful risk assessment of individual patients.

Higher body mass index raises immature platelet count: potential contribution to obesity-related thrombosis

Higher body mass index (BMI) is a risk factor for thrombosis. Platelets are essential for hemostasis but contribute to thrombosis when activated pathologically. We hypothesized that higher BMI leads to changes in platelet characteristics, thereby increasing thrombotic risk. The effect of BMI on platelet traits (measured by Sysmex) was explored in 33 388 UK blood donors (INTERVAL study). Linear regression showed that higher BMI was positively associated with greater plateletcrit (PCT), platelet count (PLT), immature platelet count (IPC), and side fluorescence (SFL, a measure of mRNA content used to derive IPC). Mendelian randomization (MR), applied to estimate a causal effect with BMI proxied by a genetic risk score, provided causal estimates for a positive effect of BMI on both SFL and IPC, but there was little evidence for a causal effect of BMI on PCT or PLT. Follow-up analyses explored the functional relevance of platelet characteristics in a pre-operative cardiac cohort (COPTIC). Linear regression provided observational evidence for a positive association between IPC and agonist-induced whole blood platelet aggregation. Results indicate that higher BMI raises the number of immature platelets, which is associated with greater whole blood platelet aggregation in a cardiac cohort. Higher IPC could therefore contribute to obesity-related thrombosis.

Role of Reticulated Platelets in Cardiovascular Disease

Human platelets differ considerably with regard to their size, RNA content and thrombogenicity. Reticulated platelets (RPs) are young, hyper-reactive platelets that are newly released from the bone marrow. They are larger and contain more RNA compared to older platelets. In comparison to more mature platelets, they exhibit a significantly higher thrombogenicity and are known to be elevated in patients with an increased platelet turnover such as, diabetics and after acute myocardial infarction. Several studies have shown that RPs correlate with an insufficient antiplatelet response to aspirin and specific P2Y₁₂ receptor inhibitors. In addition, RPs are promising novel biomarkers for the prediction of adverse cardiovascular events in cardiovascular disease. However, the reason for RPs intrinsic hyper-reactivity and their association with ischemic events is not completely understood and the biology of RPs is still under investigation. We here present a structured review of preclinical and clinical findings concerning the role of RPs in cardiovascular disease.

Evaluation of the equivalence of different intakes of Fruitflow in affecting platelet aggregation and thrombin generation capacity in a randomized, double-blinded pilot study in male subjects

BACKGROUND

The water-soluble tomato extract, Fruitflow® is a dietary antiplatelet which can be used to lower platelet aggregability in primary preventative settings. We carried out a pilot study to investigate the range of intakes linked to efficacy and to make an initial assessment of variability in response to Fruitflow®.

METHODS

Platelet response to adenosine diphosphate (ADP) agonist and thrombin generation capacity were monitored at baseline and 24 h after consuming 0, 30, 75, 150 or 300 mg of Fruitflow® in a randomized, double-blinded crossover study in male subjects 30-65 years of age (N = 12). Results were evaluated for equivalence to the standard 150 mg dose.

RESULTS

Results showed that the changes from baseline aggregation and thrombin generation observed after the 75 mg, 150 mg, and 300 mg supplements were equivalent. Aggregation was reduced from baseline by - 12.9 ± 17.7%, - 12.0 ± 13.9% and - 17.7 ± 15.7% respectively, while thrombin generation capacity fell by - 8.6 ± 4.1%, - 9.2 ± 3.1% and - 11.3 ± 2.3% respectively. Effects observed for 0 mg and 30 mg supplements were non-equivalent to 150 mg and not different from baseline (aggregation changed by 3.0 ± 5.0% and - 0.7 ± 10.2% respectively, while thrombin generation changed by 0.8 ± 3.0% and 0.8 ± 3.1% respectively).

CONCLUSIONS

The data suggest that the efficacious range for Fruitflow® lies between 75 mg and 300 mg, depending on the individual. It may be pertinent to personalize the daily intake of Fruitflow® depending on individual platelet response.

TRIAL REGISTRATION

ISRCTN53447583 , 24/02/2021.

Apoptotic Ablation of Platelets Reduces Atherosclerosis in Mice With Diabetes

OBJECTIVE

People with diabetes are at a significantly higher risk of cardiovascular disease, in part, due to accelerated atherosclerosis. Diabetic subjects have increased number of platelets that are activated, more reactive, and respond suboptimally to antiplatelet therapies. We hypothesized that reducing platelet numbers by inducing their premature apoptotic death would decrease atherosclerosis. Approach and Results: This was achieved by targeting the antiapoptotic protein Bcl-x_L (B-cell lymphoma-extra large; which is essential for platelet viability) via distinct genetic and pharmacological approaches. In the former, we transplanted bone marrow from mice carrying the Tyr15 to Cys loss of function allele of Bcl-x (known as Bcl-x^Plt20) or wild-type littermate controls into atherosclerotic-prone Ldlr^+/- mice made diabetic with streptozotocin and fed a Western diet. Reduced Bcl-x_L function in hematopoietic cells significantly decreased platelet numbers, exclusive of other hematologic changes. This led to a significant reduction in atherosclerotic lesion formation in Bcl-x^Plt20 bone marrow transplanted Ldlr^+/- mice. To assess the potential therapeutic relevance of reducing platelets in atherosclerosis, we next targeted Bcl-x_L with a pharmacological strategy. This was achieved by low-dose administration of the BH3 (B-cell lymphoma-2 homology domain 3) mimetic, ABT-737 triweekly, in diabetic Apoe^-/- mice for the final 6 weeks of a 12-week study. ABT-737 normalized platelet numbers along with platelet and leukocyte activation to that of nondiabetic controls, significantly reducing atherosclerosis while promoting a more stable plaque phenotype.

CONCLUSIONS

These studies suggest that selectively reducing circulating platelets, by targeting Bcl-x_L to promote platelet apoptosis, can reduce atherosclerosis and lower cardiovascular disease risk in diabetes. Graphic Abstract: A graphic abstract is available for this article.

Comparison of Light Transmission Aggregometry With Impedance Aggregometry in Patients on Potent P2Y12 Inhibitors

Since data on the agreement between light transmission aggregometry (LTA) and multiple electrode aggregometry (MEA) in patients on the more potent P2Y₁₂ inhibitors are missing so far, we investigated if the evaluation of the responsiveness to therapy by LTA can be replaced by MEA in 160 acute coronary syndrome (ACS) patients on dual antiplatelet therapy with aspirin and prasugrel or ticagrelor (n = 80 each). Cut-off values for high on-treatment residual platelet reactivity (HRPR) in response to adenosine diphosphate (ADP) or arachidonic acid (AA) were defined according to previous studies showing an association of HRPR with the occurrence of adverse ischemic outcomes. ADP- inducible platelet aggregation was 33% and 37% (P = 0.07) by LTA and 19 AU and 20 AU (P = 0.38) by MEA in prasugrel- and ticagrelor-treated patients, respectively. AA- inducible platelet aggregation was 2% and 3% by LTA and 15 AU and 16 AU by MEA, (all P ≥ 0.3) in patients on prasugrel and ticagrelor, respectively. By LTA, HRPR ADP and HRPR AA were seen in 5%/5% and in 4%/ 13% of patients receiving prasugrel- and ticagrelor, respectively. By MEA, HRPR ADP and HRPR AA were seen in 3%/ 25% and 0%/24% of prasugrel- and ticagrelor-treated patients, respectively. ADP-inducible platelet reactivity by MEA correlated significantly with LTA ADP in prasugrel-treated patients (r = 0.4, P < 0.001), but not in those receiving ticagrelor (r = 0.09, P = 0.45). AA-inducible platelet aggregation by LTA and MEA did not correlate in prasugrel- and ticagrelor-treated patients. Sensitivity/specificity of HRPR by MEA to detect HRPR by LTA were 25%/99% for MEA ADP and 100%/79% for MEA AA in prasugrel-treated patients, and 0%/100% for MEA ADP and 70%/83% for MEA AA in ticagrelor-treated patients. In conclusion, on-treatment residual ADP-inducible platelet reactivity by LTA and MEA shows a significant correlation in prasugrel- but not ticagrelor-treated patients. However, in both groups LTA and MEA revealed heterogeneous results regarding the classification of patients as responders or non-responders to P2Y₁₂ inhibition.

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.

Association of metabolic syndrome with non-thromboembolic adverse cardiac outcomes in patients with atrial fibrillation

Aims

Evidence suggests an excess risk of non-thromboembolic major adverse cardiac events (MACE) associated with atrial fibrillation (AF), particularly in individuals free of overt coronary artery disease (CAD). Metabolic syndrome (MetS) increases cardiovascular risk in the general population, but less is known how it influences outcomes in AF patients. We aimed to assess whether MetS affects the risk of MACE in AF patients without overt CAD.

Methods and results

This prospective, observational study enrolled 843 AF patients (mean-age, 62.5 ± 12.1 years, 38.6% female) without overt CAD. Metabolic syndrome was defined according to the National Cholesterol Education Program. The 5-year composite MACE included myocardial infarction (MI), coronary revascularization, and cardiac death. Metabolic syndrome was present in 302 (35.8%) patients. At 5-year follow-up, 118 (14.0%) patients experienced MACE (2.80%/year). Metabolic syndrome conferred a multivariable adjusted hazard ratio (aHR) of 1.98 for MACE [95% confidence interval (CI), 1.23-3.16; P = 0.004], and for individual outcomes: MI (aHR, 2.00; 95% CI, 1.69-5.11; P < 0.001), revascularization (aHR, 2.33; 95% CI, 1.40-3.87; P = 0.001), and cardiac death (aHR, 2.59; 95% CI, 1.25-5.33; P = 0.011). Following the propensity score (PS)-adjustment for MetS, the association between MetS and MACE (PS-aHR, 1.87; 95% CI, 1.21-3.01; P = 0.012), MI (PS-aHR, 1.72; 95% CI, 1.54-5.00; P = 0.008), revascularization (PS-aHR, 2.18; 95% CI, 1.69-3.11; P = 0.015), and cardiac death (PS-aHR, 2.27; 95% CI, 1.14-5.11; P = 0.023) remained significant.

Conclusion

Metabolic syndrome is common in AF patients without overt CAD, and confers an independent, increased risk of MACE, including MI, coronary revascularization, and cardiac death. Given its prognostic implications, prevention and treatment of MetS may reduce the burden of non-thromboembolic complications in AF.

Severe obesity and bariatric surgery alter the platelet mRNA profile

Mechanisms explaining the relationship between obesity and cardiovascular disease (CVD) are needed. Despite growing recognition of the importance of the anucleate platelet transcriptome, low levels of RNA in platelets make assessment difficult. We sought to perform unbiased platelet RNA profiling in obesity by performing a prospective study of severe obesity and weight loss via bariatric surgery on platelet characteristics and mRNA profile in 26 pre-menopausal, non-diabetic women (31.6 ± 8.4 years; BMI 43.0 ± 6.5 kg/m²) who underwent sleeve gastrectomy. Totally, 10 women of similar age with normal BMI served as controls. Platelet activation via flow cytometry was assessed before and after surgery. RNA-sequencing (RNAseq) was performed on platelet isolates from a subset of 13 subjects (eight obese women and five normal-BMI subjects). Platelet count, size, and age did not differ between control and obese women. However, platelet surface P-selectin and CD40 were higher in obesity. RNAseq demonstrated 629 differentially abundant transcripts in obesity. Notably, S100A9 and AGER, established markers of cardiovascular risk, were two of the most highly upregulated transcripts (each > 2.5 fold). At 6 months post-operatively, subjects lost 26.1 ± 5.8% body weight and inducible platelet P-selectin expression was reduced. Expression of 170 transcripts was affected by surgery, but only a small fraction (46/629) were genes found altered in obesity. We demonstrate that obesity is associated with an altered platelet transcriptome and increased platelet activation, which is partly attenuated by bariatric surgery. These observations suggest that platelets may contribute to increased cardiovascular risk in obesity through a variety of mechanisms.

Diabetes and Platelet Response to Low-Dose Aspirin

CONTEXT

Previous studies have suggested less cardioprotective benefit of aspirin in adults with diabetes, raising concerns about "aspirin resistance" and potentially reduced effectiveness for prevention of cardiovascular disease (CVD).

OBJECTIVE

To examine differences in platelet response to aspirin by diabetes status.

DESIGN, SETTING, PARTICIPANTS

We examined platelet response before and after aspirin (81 mg/day for 14 days) in 2113 adults (175 with diabetes, 1,938 without diabetes), in the Genetic Study of Aspirin Responsiveness cohort, who had family history of early-onset CVD.

MAIN OUTCOME MEASURES

In vivo platelet activation (urinary thromboxane B2), in vitro platelet aggregation to agonists (arachidonic acid, adenosine diphosphate, collagen), and platelet function analyzer-100 closure time.

RESULTS

Although adults with diabetes had higher in vivo platelet activation before aspirin, the reduction in in vivo platelet activation after aspirin was similar in those with vs without diabetes. Likewise, the reduction in multiple in vitro platelet measures was similar after aspirin by diabetes status. In regression analyses adjusted for age, sex, race, BMI, smoking, platelet counts, and fibrinogen levels, in vivo platelet activation remained higher in adults with vs without diabetes after aspirin (P = 0.04), but this difference was attenuated after additional adjustment for preaspirin levels (P = 0.10). No differences by diabetes status were noted for any of the in vitro platelet measures after aspirin in fully adjusted models that also accounted for preaspirin levels.

CONCLUSIONS

In vitro platelet response to aspirin does not differ by diabetes status, suggesting no intrinsic differences in platelet response to aspirin. Instead, factors extrinsic to platelet function should be investigated to give further insights into aspirin use for primary prevention in diabetes.

Thrombosis and Vascular Inflammation in Diabetes: Mechanisms and Potential Therapeutic Targets

Cardiovascular disease remains the main cause of morbidity and mortality in patients with diabetes. The risk of vascular ischemia is increased in this population and outcome following an event is inferior compared to individuals with normal glucose metabolism. The reasons for the adverse vascular profile in diabetes are related to a combination of more extensive atherosclerotic disease coupled with an enhanced thrombotic environment. Long-term measures to halt the accelerated atherosclerotic process in diabetes have only partially addressed vascular pathology, while long-term antithrombotic management remains largely similar to individuals without diabetes. We address in this review the pathophysiological mechanisms responsible for atherosclerosis with special emphasis on diabetes-related pathways. We also cover the enhanced thrombotic milieu, characterized by increased platelet activation, raised activity of procoagulant proteins together with compromised function of the fibrinolytic system. Potential new therapeutic targets to reduce the risk of atherothrombosis in diabetes are explored, including alternative use of existing therapies. Special emphasis is placed on diabetes-specific therapeutic targets that have the potential to reduce vascular risk while keeping an acceptable clinical side effect profile. It is now generally acknowledged that diabetes is not a single clinical entity but a continuum of various stages of the condition with each having a different vascular risk. Therefore, we propose that future therapies aiming to reduce vascular risk in diabetes require a stratified approach with each group having a "stage-specific" vascular management strategy. This "individualized care" in diabetes may prove to be essential to improve vascular outcome in this high risk population.

COSMIC project: consensus on the objectives of the metabolic syndrome in clinic

Metabolic syndrome (MetS), a disorder with a high and growing prevalence, is a recognized risk factor for cardiovascular disease (CVD) and type 2 diabetes. It is a constellation of clinical and metabolic risk factors that include abdominal obesity, dyslipidemia, glucose intolerance, and hypertension. Unfortunately, MetS is typically underrecognized, and there is great heterogeneity in its management, which can hamper clinical decision-making and be a barrier to achieving the therapeutic goals of CVD and diabetes prevention. Although no single treatment for MetS as a whole currently exists, management should be targeted at treating the conditions contributing to it and possibly reversing the risk factors. All this justifies the need to develop recommendations that adapt existing knowledge to clinical practice in our healthcare system. In this regard, professionals from different scientific societies who are involved in the management of the different MetS components reviewed the available scientific evidence focused basically on therapeutic aspects of MetS and developed a consensus document to establish recommendations on therapeutic goals that facilitate their homogenization in clinical decision-making.

Neutrophil-derived S100 calcium-binding proteins A8/A9 promote reticulated thrombocytosis and atherogenesis in diabetes

Platelets play a critical role in atherogenesis and thrombosis-mediated myocardial ischemia, processes that are accelerated in diabetes. Whether hyperglycemia promotes platelet production and whether enhanced platelet production contributes to enhanced atherothrombosis remains unknown. Here we found that in response to hyperglycemia, neutrophil-derived S100 calcium-binding proteins A8/A9 (S100A8/A9) interact with the receptor for advanced glycation end products (RAGE) on hepatic Kupffer cells, resulting in increased production of IL-6, a pleiotropic cytokine that is implicated in inflammatory thrombocytosis. IL-6 acts on hepatocytes to enhance the production of thrombopoietin, which in turn interacts with its cognate receptor c-MPL on megakaryocytes and bone marrow progenitor cells to promote their expansion and proliferation, resulting in reticulated thrombocytosis. Lowering blood glucose using a sodium-glucose cotransporter 2 inhibitor (dapagliflozin), depleting neutrophils or Kupffer cells, or inhibiting S100A8/A9 binding to RAGE (using paquinimod), all reduced diabetes-induced thrombocytosis. Inhibiting S100A8/A9 also decreased atherogenesis in diabetic mice. Finally, we found that patients with type 2 diabetes have reticulated thrombocytosis that correlates with glycated hemoglobin as well as increased plasma S100A8/A9 levels. These studies provide insights into the mechanisms that regulate platelet production and may aid in the development of strategies to improve on current antiplatelet therapies and to reduce cardiovascular disease risk in diabetes.

Disordered haematopoiesis and athero-thrombosis

Atherosclerosis, the major underlying cause of cardiovascular disease, is characterized by a lipid-driven infiltration of inflammatory cells in large and medium arteries. Increased production and activation of monocytes, neutrophils, and platelets, driven by hypercholesterolaemia and defective high-density lipoproteins-mediated cholesterol efflux, tissue necrosis and cytokine production after myocardial infarction, or metabolic abnormalities associated with diabetes, contribute to atherogenesis and athero-thrombosis. This suggests that in addition to traditional approaches of low-density lipoproteins lowering and anti-platelet drugs, therapies directed at abnormal haematopoiesis, including anti-inflammatory agents, drugs that suppress myelopoiesis, and excessive platelet production, rHDL infusions and anti-obesity and anti-diabetic agents, may help to prevent athero-thrombosis.

Metabolic syndrome update

The metabolic syndrome is a multiplex risk factor for atherosclerotic cardiovascular disease and type 2 diabetes. It is composed of atherogenic dyslipidemia, elevated blood pressure, insulin resistance and elevated glucose, a pro-thrombotic state, and a pro-inflammatory state. Excess energy intake and concomitant obesity are the major drivers of the syndrome. Lifestyle intervention can reverse metabolic risk factors, but at times, drug therapies or bariatric surgery may be required to control more overt risk factors.

Modification of platelet proteins by malondialdehyde: prevention by dicarbonyl scavengers

The thromboxane synthase converts prostaglandin H(2) to thromboxane A(2) and malondialdehyde (MDA) in approximately equimolar amounts. A reactive dicarbonyl, MDA forms covalent adducts of amino groups, including the ε-amine of lysine, but the importance of this reaction in platelets was unknown. Utilizing a novel LC/MS/MS method for analysis of one of the MDA adducts, the dilysyl-MDA cross-link, we demonstrated that dilysyl-MDA cross-links in human platelets are formed following platelet activation via the cyclooxygenase (COX)-1/thromboxane synthase pathway. Salicylamine and analogs of salicylamine were shown to react with MDA preferentially, thereby preventing formation of lysine adducts. Dilysyl-MDA cross-links were measured in two diseases known to be associated with increased platelet activation. Levels of platelet dilysyl-MDA cross-links were increased by 2-fold in metabolic syndrome relative to healthy subjects, and by 1.9-fold in sickle cell disease (SCD). In patients with SCD, the reduction of platelet dilysyl-MDA cross-links following administration of nonsteroidal anti-inflammatory drug provided evidence that MDA modifications of platelet proteins in this disease are derived from the COX pathway. In summary, MDA adducts of platelet proteins that cross-link lysines are formed on platelet activation and are increased in diseases associated with platelet activation. These protein modifications can be prevented by salicylamine-related scavengers.

Drug delivery and therapeutic impact of extended-release acetylsalicylic acid

Current treatment guidelines recommend once-daily, low-dose acetylsalicylic acid (ASA; aspirin) for secondary prevention of cardiovascular events. However, the anti-thrombotic benefits of traditional ASA formulations may not extend over a 24-h period, especially in patients at high risk for a recurrent cardiovascular event. A next-generation, extended-release ASA formulation (ER-ASA) has been developed to provide 24-h anti-thrombotic coverage with once-daily dosing. The pharmacokinetics of ER-ASA indicates slower absorption and prolonged ASA release versus immediate-release ASA, with a favorable safety profile. ER-ASA minimizes systemic ASA absorption and provides sustained antiplatelet effects over a 24-h period.

Clopidogrel resistance response in patients with coronary artery disease and metabolic syndrome: the role of hyperglycemia and obesity

BACKGROUND

Despite the proven benefits of clopidogrel combined aspirin therapy for coronary artery disease (CAD), CAD patients with metabolic syndrome (MS) still tend to have coronary thrombotic events. We aimed to investigate the influence of metabolic risk factors on the efficacy of clopidogrel treatment in patients with CAD undergoing percutaneous coronary intervention (PCI).

METHODS

Cohorts of 168 MS and 168 non-MS subjects with CAD identified by coronary angiography (CAG) were enrolled in our study. MS was defined by modified Adult Treatment Panel III criteria. All subjects had taken 100 mg aspirin and 75 mg clopidogrel daily for more than 1 month, and administered loading doses of 600 mg clopidogrel and 300 mg aspirin before PCI. Blood samples were taken 24 h after the loading doses of clopidogrel and aspirin. Platelet aggregation was measured using light transmittance aggregometry (LTA) and thrombelastography (TEG). Clopidogrel resistance was defined as more than 50% adenosine diphosphate (ADP) induced platelet aggregation as measured by TEG.

RESULTS

Platelet aggregation inhibition rate by ADP was significantly lower in patients with MS as measured both by TEG (55% ± 31% vs. 68% ± 32%; P < 0.001) and LTA (29% ± 23% vs. 42% ± 29%; P < 0.001). In the multivariate analysis, elderly [OR (95% CI): 1.483 (1.047-6.248); P = 0.002], obesity [OR (95% CI): 3.608 (1.241-10.488); P = 0.018], high fasting plasma glucose level [OR (95% CI): 2.717 (1.176-6.277); P = 0.019] and hyperuricemia [OR (95% CI): 2.583 (1.095-6.094); P = 0.030] were all statistically risk factors for clopidogrel resistance. CAD patients with diabetes and obesity were more likely to have clopidogrel resistance than the CAD patients without diabetes and obesity [75% (61/81) vs. 43% (67/156); P < 0.001].

CONCLUSIONS

CAD patients with MS appeared to have poorer antiplatelet response to clopidogrel compared to those without MS. Obesity, diabetes and hyperuricemia were all significantly associated with clopidogrel resistance.

Loss of the insulin receptor in murine megakaryocytes/platelets causes thrombocytosis and alterations in IGF signalling

Aims

Patients with conditions that are associated with insulin resistance such as obesity, type 2 diabetes mellitus, and polycystic ovary syndrome have an increased risk of thrombosis and a concurrent hyperactive platelet phenotype. Our aim was to determine whether insulin resistance of megakaryocytes/platelets promotes platelet hyperactivation.

Methods and results

We generated a conditional mouse model where the insulin receptor (IR) was specifically knocked out in megakaryocytes/platelets and performed ex vivo platelet activation studies in wild-type (WT) and IR-deficient platelets by measuring aggregation, integrin α_IIbβ₃ activation, and dense and α-granule secretion. Deletion of IR resulted in an increase in platelet count and volume, and blocked the action of insulin on platelet signalling and function. Platelet aggregation, granule secretion, and integrin α_IIbβ₃ activation in response to the glycoprotein VI (GPVI) agonist collagen-related peptide (CRP) were significantly reduced in platelets lacking IR. This was accompanied by a reduction in the phosphorylation of effectors downstream of GPVI. Interestingly, loss of IR also resulted in a reduction in insulin-like growth factor-1 (IGF-1)- and insulin-like growth factor-2 (IGF-2)-mediated phosphorylation of IRS-1, Akt, and GSK3β and priming of CRP-mediated platelet activation. Pharmacological inhibition of IR and the IGF-1 receptor in WT platelets recapitulated the platelet phenotype of IR-deficient platelets.

Conclusions

Deletion of IR (i) increases platelet count and volume, (ii) does not cause platelet hyperactivity, and (iii) reduces GPVI-mediated platelet function and platelet priming by IGF-1 and IGF-2.

Time-Dependent Effects of Aspirin on Blood Pressure and Morning Platelet Reactivity

Aspirin is used for cardiovascular disease (CVD) prevention by millions of patients on a daily basis. Previous studies suggested that aspirin intake at bedtime reduces blood pressure compared with intake on awakening. This has never been studied in patients with CVD. Moreover, platelet reactivity and CVD incidence is highest during morning hours. Bedtime aspirin intake may attenuate morning platelet reactivity. This clinical trial examined the effect of bedtime aspirin intake compared with intake on awakening on 24-hour ambulatory blood pressure measurement and morning platelet reactivity in patients using aspirin for CVD prevention. In this randomized open-label crossover trial, 290 patients were randomized to take 100 mg aspirin on awakening or at bedtime during 2 periods of 3 months. At the end of each period, 24-hour blood pressure and morning platelet reactivity were measured. The primary analysis population comprised 263 (blood pressure) and 133 (platelet reactivity) patients. Aspirin intake at bedtime did not reduce blood pressure compared with intake on awakening (difference systolic/diastolic: −0.1 [95% confidence interval, −1.0, 0.9]/−0.6 [95% confidence interval, −1.2, 0.0] mm Hg). Platelet reactivity during morning hours was reduced with bedtime aspirin intake (difference: −22 aspirin reaction units [95% confidence interval, −35, −9]). The intake of low-dose aspirin at bedtime compared with intake on awakening did not reduce blood pressure of patients with CVD. However, bedtime aspirin reduced morning platelet reactivity. Future studies are needed to assess the effect of this promising simple intervention on the excess of cardiovascular events during the high risk morning hours.

Impairment of Wound Healing in Patients With Type 2 Diabetes Mellitus Influences Circulating MicroRNA Patterns via Inflammatory Cytokines

OBJECTIVE

MicroRNAs (miRNA/miR) are stably present in body fluids and are increasingly explored as disease biomarkers. Here, we investigated influence of impaired wound healing on the plasma miRNA signature and their functional importance in patients with type 2 diabetes mellitus.

APPROACH AND RESULTS

miRNA array profiling identified 41 miRNAs significantly deregulated in diabetic controls when compared with patients with diabetes mellitus-associated peripheral arterial disease and chronic wounds. Quantitative real-time polymerase chain reaction validation confirmed decrease in circulating miR-191 and miR-200b levels in type 2 diabetic versus healthy controls. This was reverted in diabetic subjects with associated peripheral arterial disease and chronic wounds, who also exhibited higher circulating C-reactive protein and proinflammatory cytokine levels compared with diabetic controls. miR-191 and miR-200b were significantly correlated with C-reactive protein or cytokine levels in patients with diabetes mellitus. Indeed, proinflammatory stress increased endothelial- or platelet-derived secretion of miR-191 or miR-200b. In addition, dermal cells took up endothelial-derived miR-191 leading to downregulation of the miR-191 target zonula occludens-1. Altered miR-191 expression influenced angiogenesis and migratory capacities of diabetic dermal endothelial cells or fibroblasts, respectively, partly via its target zonula occludens-1.

CONCLUSIONS

This study reports that (1) inflammation underlying nonhealing wounds in patients with type 2 diabetes mellitus influences plasma miRNA concentrations and (2) miR-191 modulates cellular migration and angiogenesis via paracrine regulation of zonula occludens-1 to delay the tissue repair process.

Suboptimal inhibition of platelet cyclooxygenase 1 by aspirin in systemic lupus erythematosus: association with metabolic syndrome

OBJECTIVE

Low-dose aspirin prevents platelet aggregation by suppressing thromboxane A2 (TXA2 ) synthesis. However, in some individuals TXA2 suppression by aspirin is impaired, indicating suboptimal inhibition of platelet cyclooxygenase 1 (COX-1) by aspirin. Because patients with systemic lupus erythematosus (SLE) have increased risk of thrombotic events, many receive aspirin; however, the efficacy of aspirin in SLE has not been determined. We examined the hypothesis that aspirin response is impaired in SLE.

METHODS

We assessed the effect of aspirin by measuring concentrations of the stable metabolite of TXA2 , serum thromboxane B2 (sTXB2 ), before and after treatment with daily aspirin (81 mg) for 7 days in 34 patients with SLE and 36 control subjects. The inability to suppress sTXB2 synthesis to <10 ng/ml represents suboptimal inhibition of platelet COX-1 by aspirin.

RESULTS

Aspirin almost completely suppressed sTXB2 in control subjects to median 1.5 ng/ml (interquartile range [IQR] 0.8-2.7) but had less effect in patients with SLE (median 3.1 ng/ml [IQR 2.2-5.3]) (P = 0.002). A suboptimal effect of aspirin was present in 15% (5 of 34) of the patients with SLE but not in control subjects (0 of 36) (P = 0.023). Incomplete responders were more likely to have metabolic syndrome (P = 0.048), obesity (P = 0.048), and higher concentrations of C-reactive protein (CRP) (P = 0.018).

CONCLUSION

The pharmacologic effect of aspirin is suboptimal in 15% of patients with SLE but in none of the control subjects, and the suboptimal response was associated with metabolic syndrome, obesity, and higher CRP concentrations.

Effects of bioactive-rich extracts of pomegranate, persimmon, nettle, dill, kale and Sideritis and isolated bioactives on arachidonic acid induced markers of platelet activation and aggregation

BACKGROUND

The beneficial effect of fruit- and vegetable-rich diets on cardiovascular health is partly attributed to the effect of their bioactive compounds on platelet function. The aim of this study was to investigate the effects of bioactive-rich plant extracts and isolated bioactive metabolites on platelet function. Blood samples from healthy subjects (n = 4) and subjects with metabolic syndrome (n = 4) were treated with six extracts of bioactive-rich plants consumed as traditional foods in the Black Sea region, or with human metabolites of the bioactives quercetin and sulforaphane. Markers of arachidonic acid induced platelet activation and platelet-leucocyte aggregation were assessed using flow cytometry.

RESULTS

In subjects with metabolic syndrome, kale extract significantly inhibited agonist induced P-selectin expression (P = 0.004). Sulforaphane-cysteine-glycine, a human plasma metabolite of the related glucosinolate, glucoraphanin, significantly inhibited P-selectin and GPIIb-IIIa expression (P = 0.020 and 0.024, respectively) and platelet-neutrophil aggregation (P = 0.027). Additionally, pomegranate extract significantly inhibited GPIIb-IIIa expression (P = 0.046) in subjects with metabolic syndrome. In healthy subjects only dill extract significantly inhibited agonist induced P-selectin expression (P = 0.025).

CONCLUSION

These data show that bioactive-rich extracts of kale and pomegranate that are consumed as traditional plant foods of Black Sea area countries were effective in modulating platelet function.

Relation of aspirin response to age in patients with stable coronary artery disease

Recent studies have suggested that clopidogrel response may vary significantly with age. Limited data are available exploring the age dependency of ex vivo aspirin response in young and old patients with stable coronary artery disease. Patients with stable coronary artery disease (n = 583) who had been treated with aspirin 75 to 325 mg/day for ≥1 week were recruited from a general cardiology practice. The study cohort was divided into 2 groups: patients aged <75 years (n = 438) and patients aged ≥75 years (n = 145). Aspirin response was determined using the VerifyNow Aspirin Test, and resistance was defined as ≥500 or 550 aspirin reaction units (ARU). The independent predictive value of age on VerifyNow score (as a continuous function) was determined using multivariate linear regression, adjusted for gender, body mass index, and diabetes mellitus. Younger and older patients had similar baseline clinical profiles, including relative doses of aspirin therapy. The mean VerifyNow Aspirin Test score was significantly higher in patients aged ≥75 years: 450 ± 54 versus 434 ± 53 ARU (p = 0.0007). After accounting for the primary covariates, age remained a predictor of VerifyNow score (p = 0.007). Aspirin resistance on the basis of the 500-ARU cutoff was higher in older patients (19% vs 11%, p = 0.009), but there was no difference when the 550-ARU cutoff was used (7% vs 5%, p = 0.40). In conclusion, aspirin response differs significantly by age in patients with stable CAD.

Primary and secondary prevention of cardiovascular disease in diabetes with aspirin

Diabetes is associated with an increased cardiovascular risk. The role for aspirin in diabetes is of high clinical interest. Guidelines recommend that primary prevention of cardiovascular disease (CVD) in diabetes with aspirin should be based on the individual risk for CVD. New mechanistic studies suggest that enhanced platelet turnover may partly contribute to the fact the primary prevention studies found unequivocal results in diabetes. There is initial evidence that a potential future modification of dosages in diabetes may counteract the enhancement in platelet turnover in diabetes. The use of aspirin in diabetic patients for secondary prevention of CVD is supported by key evidence. The aim of the review is to present recent studies on aspirin for prevention of CVD in diabetes and to highlight its role also in view of new mechanistic and clinical studies with aspirin. Novel aspects of aspirin, e.g. its potential role for the prevention of cancer, are also presented.

Variability in the response to antiplatelet treatment in diabetes mellitus

Atherothrombosis is a leading cause of death in patients with diabetes mellitus. Among factors contributing to the diabetic prothrombotic state, platelet activation plays a pivotal role. Numerous studies have investigated the benefits of antiplatelet therapy for primary and secondary cardiovascular prevention in diabetic patients. However, there are limited evidences that low-dose aspirin may be effective in this clinical setting. Several disease-specific factors have been identified as potential determinants of aspirin treatment failure. In this review, the main determinants of interindividual variability in response to antiplatelet agents are discussed, with particular emphasis on the pharmacokinetic and pharmacodynamic mechanisms of clinical efficacy and safety of antiplatelet drugs in patients with diabetes mellitus.

Suboptimal inhibition of platelet cyclooxygenase-1 by aspirin in metabolic syndrome

Interindividual variation in the ability of aspirin to inhibit platelet cyclooxygenase-1 (COX-1) could account for some on-treatment cardiovascular events. Here, we sought to determine whether there are clinical phenotypes that are associated with a suboptimal pharmacological effect of aspirin. In a prospective, 2-week study, we evaluated the effect of aspirin (81 mg) on platelet COX-1 in 135 patients with stable coronary artery disease by measuring serum thromboxane B(2) (sTxB(2)) as an indicator of inhibition of platelet COX-1. A nested randomized study compared enteric-coated with immediate-release formulations of aspirin. We found that sTxB(2) was systematically higher among the 83 patients with metabolic syndrome than among the 52 patients without (median: 4.0 versus 3.02 ng/mL; P=0.013). Twelve patients (14%) with metabolic syndrome, but none without metabolic syndrome, had sTxB(2) levels consistent with inadequate inhibition of COX (sTxB(2) ≥13 ng/mL). In linear regression models, metabolic syndrome (but none of its individual components) significantly associated with higher levels of log-transformed sTxB(2) (P=0.006). Higher levels of sTxB(2) associated with greater residual platelet function measured by aggregometry-based methods. Among the randomized subset, sTxB(2) levels were systematically higher among patients receiving enteric-coated aspirin. Last, urinary 11-dehydro thromboxane B(2) did not correlate with sTxB(2), suggesting that the former should not be used to quantitate aspirin's pharmacological effect on platelets. In conclusion, metabolic syndrome, which places patients at high risk for thrombotic cardiovascular events, strongly and uniquely associates with less effective inhibition of platelet COX-1 by aspirin.

Platelet activation in obesity and metabolic syndrome

Obesity is associated with increased cardiovascular disease. Metabolic syndrome (MS) identifies substantial additional cardiovascular risk beyond the individual risk factors, and is a powerful predictor of cardiovascular events even regardless of body mass index, thus suggesting a common downstream pathway conferring increased cardiovascular risk. Platelet hyper-reactivity/activation plays a central role to accelerate atherothrombosis and is the result of the interaction among the features clustering in obesity and MS: insulin resistance, inflammation, oxidative stress, endothelial dysfunction. Interestingly, the same pathogenic events largely account for the less-than-expected response to antiplatelet agents, namely low-dose aspirin. The proposed explanations for this phenomenon, besides underdosing of drug and/or reduced bioavailability, subsequent to excess of adipose tissue, include enhanced platelet turnover, leading to unacetylated COX-1 and COX-2 in newly formed platelets as a source of aspirin-escaping thromboxane formation; extraplatelet sources of thromboxane, driven by inflammatory triggers; and enhanced lipid peroxidation, activating platelets with a mechanism bypassing COX-1 acetylation or limiting COX-isozyme acetylation by aspirin. This review will address the complex interactions between platelets and the pathogenic events occurring in obesity and MS, trying to translate this body of mechanistic information into a clinically relevant read-out, in order to establish novel strategies in the prevention/treatment of atherothrombosis.

Metabolic syndrome and hepatic resection: improving outcome

OBJECTIVE

A review of the peri-operative risk associated with hepatic resection in patients with metabolic syndrome (MetS) and identification of measures for the improvement of cardiometabolic disturbances and liver-related mortality.

BACKGROUND

MetS and its hepatic manifestation non-alcoholic fatty liver disease (NAFLD) are associated with an increased operative mortality in spite of a significant improvement in peri-operative outcome after hepatic resection.

METHODS

A review of the English literature on MetS, liver resection and steatosis was performed from 1980 to 2011 using the MEDLINE and PubMed databases.

RESULTS

MetS is a predictor of NAFLD and patients with multiple metabolic risk factors may harbour non-alcoholic steatohepatitis (NASH) predictive of operative and cardiovascular mortality. Pre-operative diagnosis of unsuspected NASH with the selective use of a liver biopsy can modify the operative strategy by limiting the extent of hepatic resection, avoiding or altering the pre-operative chemotherapy regimen and the utilization of portal vein embolization. Thiazolidinediones are therapeutic for MetS and NASH and Vitamin E for active NASH; however, their utility in improving the peri-operative outcome after hepatic resection is unknown. A short-term regimen for weight loss improves post-operative patient and liver-related outcomes in patients with >30% steatosis. Cardiovascular disease associated with MetS or NAFLD should be managed aggressively. Peri-operative measures to minimize thrombotic events and acute renal injury secondary to the pro-inflammatory, prothrombotic state of MetS may further improve the outcome.

CONCLUSION

Potential candidates for hepatic resection should be screened for MetS as the pre-operative identification of NASH, short-term treatment of significant steatosis, cardiovascular risk assessment and optimization of each component of MetS may improve the peri-operative outcome in this high-risk subset of patients.

LDL from obese patients with the metabolic syndrome show increased lipid peroxidation and activate platelets

AIMS/HYPOTHESIS

This study assessed oxidative stress in LDL from obese patients with the metabolic syndrome and compared it with that in LDL from type 2 diabetic patients or control volunteers. It also determined the effect on platelets of LDL from the three groups.

METHODS

The profiles of lipids, fatty acids and fatty acid oxidation products were determined in LDL isolated from plasma of patients with the metabolic syndrome, patients with type 2 diabetes and volunteers (n = 10 per group). The effects of LDL from the participant groups on the platelet arachidonic acid signalling cascade and aggregation were investigated.

RESULTS

Compared with LDL from control volunteers, LDL from obese metabolic syndrome and type 2 diabetic patients had lower cholesteryl ester, higher triacylglycerol and lower ethanolamine plasmalogen levels. Proportions of linoleic acid were decreased in phosphatidylcholine and cholesteryl esters in LDL from both patient groups. Among the markers of lipid peroxidation, oxidation products of linoleic acid (hydroxy-octadecadienoic acids) and malondialdehyde were increased by 59% and twofold, respectively in LDL from metabolic syndrome and type 2 diabetic patients. LDL from metabolic syndrome and type 2 diabetic patients were equally potent in activating the platelet arachidonic acid signalling cascade through increased phosphorylation of p38 mitogen-activated protein kinase and cytosolic phospholipase A(2), and through increased thromboxane B(2) formation. LDL from patients with the metabolic syndrome and type 2 diabetes potentiated platelet aggregation by threefold and 3.5-fold respectively, whereas control LDL had no activating effects on platelets.

CONCLUSIONS/INTERPRETATION

The metabolic syndrome in obese patients, without or with diabetes, is associated with increased oxidative stress in LDL, which triggers platelet activation.

Morbid obesity and metabolic syndrome in Ossabaw miniature swine are associated with increased platelet reactivity

BACKGROUND

Metabolic syndrome (MetS) and type 2 diabetes mellitus in humans are associated with increased platelet activation and hyperreactivity of platelets to various agonists. Ossabaw swine develop all the hallmarks of MetS including obesity, insulin resistance, hypertension, dyslipidemia, endothelial dysfunction, and coronary artery disease when being fed excess calorie atherogenic diet. We hypothesized that Ossabaw swine with MetS would exhibit increased platelet reactivity compared with lean pigs without MetS.

MATERIALS AND METHODS

Ossabaw swine were fed high caloric, atherogenic diet for 44 weeks to induce MetS (n = 10) and were compared with lean controls without MetS that had been fed normal calorie standard diet (n = 10). Light transmittance aggregometry was performed using adenosine diphosphate (ADP), collagen, thrombin, and arachidonic acid (AA) at different concentrations. Dose response curves and EC50 were calculated. Glucose tolerance testing and intravascular ultrasound study of coronary arteries were performed.

RESULTS

MetS pigs compared with lean controls were morbidly obese, showed evidence of arterial hypertension, elevated cholesterol, low-density lipoprotein/high-density lipoprotein, and triglycerides, and insulin resistance. Platelets from MetS pigs were more sensitive to ADP-induced platelet aggregation than leans (EC50: 1.83 ± 1.3 μM vs 3.64 ± 2.2 μM; P = 0.02). MetS pigs demonstrated higher platelet aggregation in response to collagen than lean pigs (area under the curve: 286 ± 74 vs 198 ± 123; P = 0.037) and a trend for heightened response to AA (AUC: 260 ± 151 vs 178 ± 145; P = 0.13). No significant difference was found for platelet aggregation in response to thrombin.

CONCLUSIONS

MetS in Ossabaw swine is associated with increased reactivity of platelets to ADP and collagen. The Ossabaw swine may be a practical, large animal model for the study of certain aspects of platelet pathophysiology and examine vascular devices in a metabolic environment comparable to humans with MetS.

Effect of omega-3 fish oil on cardiovascular risk in diabetes

PURPOSE

Diabetes and cardiovascular disease are major public health concerns worldwide and are leading causes of morbidity and mortality. People with type 2 diabetes are at an increased risk for cardiovascular disease. Diet has a substantial affect on the progression of many diseases, including diabetes, cardiovascular disease, osteoporosis, and arthritis. Omega-3 polyunsaturated fatty acids (long-chain polyunsaturated fatty acids [LC-PUFA]) have long been attributed to the maintenance of health and may be of benefit in reducing cardiovascular risk. The purpose of this review is to investigate the possible roles of omega-3 in reducing cardiovascular risk in patients with diabetes.

METHODS

A literature search was conducted from the Medline, EBSCO, and EMBASE databases. Articles that addressed diabetes, cardiovascular disease, or omega-3 were included.

RESULTS

Reviews and studies reported an association with fish and omega-3 LC-PUFA consumption and decreased total cardiovascular mortality (approximately 15%-19%), along with decreased platelet activation and aggregation, improved lipid profiles, including reduction of triglycerides and very low-density lipoprotein (VLDL), decreased inflammation, and lowered blood pressure.

CONCLUSION

Diets higher in fish and omega-3 LC-PUFA may reduce cardiovascular risk in diabetes by inhibiting platelet aggregation, improving lipid profiles, and reducing cardiovascular mortality. Fish and omega-3 LC-PUFA can be recommended to people with diabetes and included into a diabetes management program.

Adiponectin diminishes platelet aggregation and sCD40L release. Potential role in the metabolic syndrome

The proinflammatory and proatherogenic mediator, soluble CD40 ligand (CD40L), is increased in the metabolic syndrome (MS) and released from platelets. We hypothesized that adiponectin modulates platelet function, and we sought to evaluate the association of adiponectin and sCD40L levels with platelet aggregation in MS and the effects of adiponectin on platelet aggregation and activation. Platelet aggregation and circulating adiponectin, sCD40L and P-selectin were determined in 30 controls and 30 patients with MS. Also, in vitro studies were performed in platelet-rich plasma from nine healthy volunteers. Adiponectin receptors were demonstrated by Western blotting and flow cytometry. ADP and epinephrine platelet aggregation was measured after preincubation with adiponectin. sCD40L and P-selectin secretion was measured in the supernatants by ELISA. Patients with MS had higher sCD40L and P-selectin than controls (5.96 +/- 0.50 vs. 4.28 +/- 0.41 ng/ml, P < 0.05, and 151 +/- 8 vs. 122 +/- 9 ng/ml, P < 0.05). By contrast, adiponectin was lower in patients with MS than in controls (5.25 +/- 0.30 vs. 7.35 +/- 0.34 microg/ml, P < 0.001). Higher platelet aggregation was found in MS. Adiponectin inversely correlated with P-selectin (R = -0.35, P = 0.009), sCD40L (r = -0.24, P = 0.05) and epinephrine and collagen induced aggregation (r = -0.80, P = 0.005; r = -0.70, P = 0.011). Platelets express the receptors for adiponectin. Platelet aggregatory response to epinephrine and ADP significantly decreased following preincubation with adiponectin (96 +/- 4 vs. 23 +/- 3%, P < 0.001, and 102 +/- 9 vs. 85 +/- 9%, P = 0.004). Adiponectin prevented platelet sCD40L release (1.63 +/- 0.15 vs. 2.04 +/- 0.20 ng/ml, P < 0.001). Enhanced platelet aggregation and activation markers are found in MS associated with low adiponectin concentrations. Novel evidence is provided demonstrating that adiponectin has antithrombotic properties, since it inhibits platelet aggregation and platelet activation.

Development of an improved assay system for activated platelet counts and evaluation by aspirin monitoring

Platelets represent a linkage among inflammation, thrombosis, and atherogenesis, and enhanced platelet activation is regarded as a risk for thrombotic disorders. The level of P-selectin expressed (CD62P) on the platelet surface is a useful marker of activated platelets (aPLT). Although CD62P has been measured briefly by flow cytometry using an anti-CD62P antibody, the assay remains imprecise and we tried to establish stable conditions for its measurement. The levels of aPLT are increased significantly by many factors, such as meals, sampling and keeping conditions, centrifugation, and the timing of fixation. For optimal results, sampling should be performed quickly in a K(2)-ethylenediaminetetraacetic acid (EDTA) containing a sample tube, and whole blood should be fixed with 666 mmol/L formaldehyde plus 167 mmol/L glyoxal for 5 min. After washing with phosphate buffered saline (PBS), the fixed platelets were reacted with anti-CD62P antibody for 20 min and measured by flow-cytometric detection for aPLT. The coefficient of variation of our aPLT assay was 10.4%. We also examined basic experiments to test the clinical application of our aPLT assay by monitoring aspirin therapy. The levels of aPLT after the administration of aspirin for 3 days were significantly lower than those in the group that did not receive aspirin. These results suggest that the aPLT assay is an effective analytical procedure for measuring platelet reactivity.