Evidence for prothrombotic effects of exercise and limited protection by aspirin

Acute Myocardial Infarction in a Young Bodybuilder Fighter Pilot

BACKGROUND: Although advanced coronary artery disease in young, healthy fighter pilots is uncommon, an acute cardiac event in flight could be catastrophic.CASE REPORT: After a gym workout, a 31-yr-old F-16 pilot reported severe central chest pain, one vomiting episode, and excessive sweating but no radiation of pain. Electrocardiograph showed ST elevation in V2-V6. Coronary arteriography showed a thrombotic lesion at the proximal left anterior descending (LAD) artery (90%) and one occluded LAD branch with thrombus; the rest of the arteries were normal and ejection fraction was 55%. Primary percutaneous coronary intervention to LAD with one drug-eluting stent was done. The pilot was discharged in stable hemodynamic condition with medication advice. Assessment revealed no significant cardiac risk factors. He did not seek medical care for two central chest pain episodes following a gym workout prior to this event because rest relieved the pain. He gave a history of using commercial protein supplements for bodybuilding in the past 6 yr.DISCUSSION: In this case report, the impact of aggressive gym workouts and chronic use of commercially available bodybuilding protein supplements on cardiovascular health is discussed, as well as aeromedical dilemmas related to this pilot's career. This case sparks debate about whether a highly motivated young pilot with an unexpected cardiac event should be subjected to regular intensive cardiac evaluation throughout his remaining flying career, with permanent flying limitations, or be motivated to pursue a career shift to facilitate noncomplicated career rehabilitation.Jeevarathinam S, Sabei SA, Wardi YA. Acute myocardial infarction in a young bodybuilder fighter pilot. Aerosp Med Hum Perform. 2023; 94(9):719-722.

Platelet Activation Favours NOX2-Mediated Muscle Damage in Elite Athletes: The Role of Cocoa-Derived Polyphenols

Mechanisms of exercise-induced muscle injury with etiopathogenesis and its consequences have been described; however, the impact of different intensities of exercise on the mechanisms of muscular injury development is not well understood. The aim of this study was to exploit the relationship between platelet activation, oxidative stress and muscular injuries induced by physical exercise in elite football players compared to amateur athletes. Oxidant/antioxidant status, platelet activation and markers of muscle damage were evaluated in 23 elite football players and 23 amateur athletes. Compared to amateurs, elite football players showed lower antioxidant capacity and higher oxidative stress paralleled by increased platelet activation and muscle damage markers. Simple linear regression analysis showed that sNOX2-dp and H₂O₂, sCD40L and PDGF-bb were associated with a significant increase in muscle damage biomarkers. In vitro studies also showed that plasma obtained from elite athletes increased oxidative stress and muscle damage in human skeletal muscle myoblasts cell line compared to amateurs’ plasma, an effect blunted by the NOX2 inhibitor or by the cell treatment with cocoa-derived polyphenols. These results indicate that platelet activation increased muscular injuries induced by oxidative stress. Moreover, NOX2 inhibition and polyphenol extracts treatment positively modulates redox status and reduce exercise-induced muscular injury.

Influence of cardiopulmonary exercise test on platelet function in patients with coronary artery diseases on antiplatelet therapy

Background

Cardiac rehabilitation reduces mortality and morbidity rate of patients with coronary artery diseases (CAD); however, acute exercise stimulation may also increase the thrombotic risk through platelet activation. Studies on the effects of cardiac rehabilitation on platelet function have been sparse.

Methods

A total of 28 patients (24 men and 4 women; average age = 54.6 ± 8 years old) with stable CAD were enrolled in this study and divided into Aspirin-treated (n = 11; Aspirin group) and dual-antiplatelet-treated group (DAPT group; n = 17). Symptom-limited cardiopulmonary exercise test (CPET) with a cycle ergometer was performed on all the patients. Before and after CPET, platelet function was evaluated using light transmission aggregometry and whole blood flow cytometry.

Results

All patients completed the CPET without provoked cardiac events, and the mean value of peak oxygen uptake (Peak Vo₂) was 19.3 ± 3 ml/(kg min). Prior to CPET, platelet aggregation was significantly suppressed in DAPT group compared to Aspirin group (43.0 ± 21.5 vs. 72.9 ± 7.5, p < 0.001). CPET promoted platelet aggregation in Aspirin group (72.9 ± 7.5 vs. 80.9 ± 7.6, p = 0.005) and DAPT group (43.0 ± 21.5 vs. 50.1 ± 20.9, p = 0.010), and platelet count was increased in Aspirin (210.9 ± 54.6 vs. 227.5 ± 58.1, p = 0.001) and DAPT group (217.5 ± 63.8 vs. 229.7 ± 63.7, p = 0.001). However, the expression levels of CD62p and PAC-1 were not affected by CPET in both groups.

Conclusion

Symptom-limited CPET enhanced platelet aggregation in patients with CAD despite treatment with antiplatelet, mainly via platelet count augmentation, but not through single platelet activation.

Trial registration: Effects of high intensity interval training versus moderate intensity continue training in cardiac rehabilitation on platelet function of patients with coronary heart diseases: a exploratory randomized controlled trial.

ChiCTR-INR-17010717. Registered 23 February 2017, https://www.chictr.org.cn/edit.aspx?pid=18206&htm=4.

[Résistance à l'aspirine : l'ennemi de mon ami est mon ennemi]

Low dose aspirin is an efficient antiplatelet agent to decrease the risk of occlusive arterial events, however it is not infallible. Aspirin resistance describe its inability to block the formation of thromboxane A2 in platelets and/or to produce an inhibitory effect on platelet aggregation. Detection of aspirin resistance relies on the results of various platelet function tests or on blood and urinary thromboxane metabolites concentrations, but these methods show very low correlation and reproducibility. Moreover, light-transmission aggregometry using arachidonic acid, known as the reference functional assay, requires technical expertise. The incidence rate of aspirin resistance amoung populations suffering from cardiovascular diseases is about 25%, however there is a wide variability depending on the specificity of the used test and the clinical features of the considered population. Aspirin resistance is associated with the recurrence of arterial occlusive events: the odds ratio is about 4 all tests combined, therefore it could be considered as a risk marker. Evidence is lacking regarding the relevance of these tests to resort an intensification of the antithrombotic treatment, and experts recommend to reserve their use for high-risk situations. Nevertheless several studies have explored the effect of dose increases or intake frequency increases, and revealed encouraging results regarding pharmacodynamic endpoints. The reasons for aspirin resistance are numerous, often remain debate, and can accumulate to result in poor response to aspirin.

Evidence for wall shear stress-dependent t-PA release in human conduit arteries: role of endothelial factors and impact of high blood pressure

Tissue plasminogen activator (t-PA) converts plasminogen into the serine protease plasmin, which in turn degrades fibrin clots. This study assessed whether an increase in shear stress is associated in humans in vivo with the release of t-PA in peripheral conduit arteries, the impact of high blood pressure and the role of NO and CYP450-derived epoxyeicosatrienoic acids (EETs). Local t-PA levels were quantified at baseline and during a sustained increase in radial artery wall shear stress induced by hand skin heating (from 34 to 44 °C) in a total of 25 subjects, among whom 8 were newly diagnosed essential hypertensive patients. The impact of the brachial infusion of NO synthase (L-NMMA) and CYP450 inhibitors (fluconazole) on t-PA release was assessed. The increase in shear stress induced by heating was associated with an increase in local t-PA release (from 3.0 ± 0.5 to 19.2 ± 5.5 ng/min, n = 25, P < 0.01). The magnitude of t-PA release was positively correlated with the increase in shear stress (r = 0.64, P < 0.001) and negatively correlated with mean blood pressure (r = -0.443, P = 0.027). These associations persisted after multiple adjustments for confounding factors. Finally, t-PA release was reduced by L-NMMA and to a larger extent by the combination of L-NMMA and fluconazole without a change in shear stress. The increase in wall shear stress in the peripheral conduit arteries induces a release of t-PA by a mechanism involving NO and EETs. The alteration of this response by high blood pressure may contribute to reducing the fibrinolytic potential and enhancing the risk of arterial thrombosis during exercise.

Activation of metabolite receptor GPR91 promotes platelet aggregation and transcellular biosynthesis of leukotriene C4

BACKGROUND

Succinate is a Krebs cycle intermediate whose formation is enhanced under metabolic stress, and for which a selective sensor GPR91 has been identified on various cell types including platelets. Platelet-derived eicosanoids play pivotal roles in platelet activation/aggregation, which is key to thrombus formation and progression of atherothrombosis.

OBJECTIVES

This study aims to decipher the molecular mechanism(s) and potential involvement of eicosanoids in succinate enhanced platelet activation/aggregation.

METHODS

We used liquid chromatography-mass spectrometry (LC-MS)/MS-based lipid mediator profiling to identify eicosanoids regulated by succinate. We ran light transmittance aggregometry and flow cytometry to assess platelet aggregation, P-selectin expression, and platelet-polymorphonuclear leukocyte (PMN) adherence. Various pharmacological tools were used to assess the contributions of GPR91 signalling and eicosanoids in platelet aggregation.

RESULTS

Succinate and two types of synthetic non-metabolite GPR91 agonists-cis-epoxysuccinate (cES) and Cmpd131-potentiated platelet aggregation, which was partially blocked by a selective GPR91 antagonist XT1. GPR91 activation increased production of 12-hydroxy-eicosatetraenoic acid (12-HETE), thromboxane (TX) A2 , and 12-hydroxy-heptadecatrienoic acid (12-HHT) in human platelets, associated with phosphorylation of cytosolic phospholipase A2 (cPLA2 ), suggesting increased availability of free arachidonic acid. Blocking 12-HETE and TXA2 synthesis, or antagonism of the TXA2 receptor, significantly reduced platelet aggregation enhanced by GPR91 signalling. Moreover, platelet-PMN suspensions challenged with succinate exhibited enhanced transcellular biosynthesis of leukotriene C4 (LTC4 ), a powerful proinflammatory vascular spasmogen.

CONCLUSION

Succinate signals through GPR91 to promote biosynthesis of eicosanoids, which contribute to platelet aggregation/activation and potentially vascular inflammation. Hence, GPR91 may be a suitable target for pharmacological intervention in atherothrombotic conditions.

Aronia juice consumption prior to half-marathon race can acutely affect platelet activation in recreational runners

Long-distance running, especially in non-professional runners, can increase cardiac arrest risk by enhancing platelet activation and aggregation. Polyphenols can exert cardioprotective effects by positively influencing platelet function. This study aimed to examine the acute effects of polyphenol-rich aronia juice consumption, before simulation of a half-marathon race, on platelet activation and aggregation with leukocytes in recreational runners. In this acute crossover study,10 healthy male runners (age 30.8 ± 2.3 years) consumed breakfast with 200 mL of aronia juice or 200 mL of placebo. They warmed-up and ran a simulated half-marathon race (21.1 km). Blood was collected at baseline, and at 15 min, 1 h, and 24 h after the run. All variables were analyzed with 4 (time) × 2 (group) ANOVA with repeated measures on both factors. Results revealed a significant effect of group on platelet activation parameters: P-selectin and GPIIb-IIIa expressions significantly decreased in the aronia group compared with the placebo group (F_[1,9] = 10.282, p = 0.011 and F_[1,9] = 7.860, p = 0.021, respectively). The effect of time was significant on both platelet aggregation markers: platelet-monocyte and platelet-neutrophil aggregates were significantly lower after the race (F_[3,7] = 4.227, p = 0.014 and F_[3,7] = 70.065, p = 0.000, respectively), with changes more pronounced in the later. All effects remained when platelets were exposed to an agonist. These results suggest that aronia consumption could counteract the half-marathon race-induced changes in platelet function. Novelty Aronia juice consumption significantly decreased the expression of platelet activation markers but did not affect platelet aggregation. The race itself did significantly reduce platelet-neutrophil aggregation. Aronia juice may serve as a supplement beverage for recreational runners to alleviate enhanced platelet reactivity caused by prolonged running.

Increased exercise-related platelet activation assessed by impedance aggregometry in diabetic patients despite aspirin therapy

Aspirin is widely used for the prevention of thromboembolic diseases, but inhibition of platelet aggregation (PA) is not uniform. Additionally, aspirin has been shown to be ineffective in blunting PA in response to exercise in patients with coronary artery disease (CAD). Limited data exists about platelet function following acute exercise in diabetics taking aspirin. In our study, we aimed to investigate PA before and after exercise stress test in type-2 diabetic patients taking aspirin. Forty-three patients with type-2 diabetes mellitus (DM) and 36 subjects (age- and sex-matched) as control group were included prospectively. All participants were under aspirin (100 mg/day) therapy for at least 1 week. The measures of PA were assessed by impedance aggregometry using arachidonic acid as an agonist (ASPI test). Blood samplings were undertaken before and immediately after treadmill exercise test. At rest, diabetic and control groups had comparable pre-exercise PA (22.97 ± 14.57 versus 22.11 ± 12.71 AU min, p = NS, respectively). After treadmill exercise, both groups showed significantly higher absolute increase (9.02 ± 13.08 and 3.66 ± 5.87 AU min, p < 0.01, p < 0.01, respectively) and percent (%) increase (45.67 ± 49.34 and 24.04 ± 46.59 AU min, p < 0.01, p = 0.01, respectively) in PA. Both absolute increase (p < 0.05) and % increase (p < 0.05) in PA were significantly higher in DM group compared to the control group. Multiple regression analysis revealed that high-sensitive C-reactive protein (p = 0.014) was independent predictor of absolute increase PA. Our study showed that aspirin has limited effect in inhibiting exercise-induced PA, even in the absence of documented CAD. The increase in PA following exercise was significantly greater in patients with DM compared with controls.

Effects of Catheterization on Artery Function and Health: When Should Patients Start Exercising Following Their Coronary Intervention?

Coronary artery disease (CAD) is a leading cause of death worldwide, and percutaneous transluminal coronary angiography (PTCA) and/or percutaneous coronary intervention (PCI; angioplasty) are commonly used to diagnose and/or treat the obstructed coronaries. Exercise-based rehabilitation is recommended for all CAD patients; however, most guidelines do not specify when exercise training should commence following PTCA and/or PCI. Catheterization can result in arterial dysfunction and acute injury, and given the fact that exercise, particularly at higher intensities, is associated with elevated inflammatory and oxidative stress, endothelial dysfunction and a pro-thrombotic milieu, performing exercise post-PTCA/PCI may transiently elevate the risk of cardiac events. This review aims to summarize extant literature relating to the impacts of coronary interventions on arterial function, including the time-course of recovery and the potential deleterious and/or beneficial impacts of acute versus long-term exercise. The current literature suggests that arterial dysfunction induced by catheterization recovers 4-12 weeks following catheterization. This review proposes that a period of relative arterial vulnerability may exist and exercise during this period may contribute to elevated event susceptibility. We therefore suggest that CAD patients start an exercise training programme between 2 and 4 weeks post-PCI, recognizing that the literature suggest there is a 'grey area' for functional recovery between 2 and 12 weeks post-catheterization. The timing of exercise onset should take into consideration the individual characteristics of patients (age, severity of disease, comorbidities) and the intensity, frequency and duration of the exercise prescription.

Increased platelet reactivity and platelet-leukocyte aggregation after elective coronary bypass surgery

Inflammatory mechanisms are activated, and thrombotic complications occur during the initial months after coronary artery bypass grafting (CABG). Therefore, changes over time of platelet activation and platelet-leukocyte interactions after CABG are of interest. Whole-blood flow cytometry was performed before, and 4-6 days, one month, and three months after elective CABG in 54 men with stable coronary artery disease treated with acetylsalicylic acid (ASA). Single platelets and platelet-leukocyte aggregates (PLAs) among monocytes (P-Mon), neutrophils (P-Neu), and lymphocytes (P-Lym) were studied without and with stimulation by submaximal concentrations of ADP, thrombin, and the thromboxane analog U46619. White blood cell counts were increased during the initial postoperative course, and platelet counts were increased after one month. Platelet P-selectin expression was significantly enhanced at one month when stimulated by thrombin and U46619 and at three months with ADP and thrombin. All PLAs subtypes were increased at one month without stimulation in vitro. P-Mon and P-Neu stimulated by ADP, thrombin, or U46619 were significantly increased one month after the operation but decreased compared to baseline at three months. Agonist stimulated P-Lyms were increased at one month and remained increased at three months after ADP stimulation. There was significant platelet activation and formation of PLAs unstimulated and after agonist stimulation by ADP, thrombin, and a thromboxane analog after CABG in patients with stable coronary artery disease irrespective of ASA treatment. Changes observed up to three months after CABG support further studies of the clinical implications of protracted increases in platelet activation and platelet-leukocyte interactions.

Cell adhesion molecules and exercise

Background

An extensive systematic review was undertaken in the current literature in order to explore the role of different types and intensities of exercise in cell adhesion molecules (CAMs), one of the markers of vascular inflammation, endothelial dysfunction, and atherosclerosis.

Methods

Twenty-eight qualifying studies were extensively reviewed to examine the effects of different intensities (low-to-moderate vs. high) and types (aerobic vs. resistance) of exercise on intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and selectins.

Results

Low-to-moderate intensity aerobic exercise favorably decreased CAMs in a variety of subject populations, while CAMs momentarily increased immediately following high-intensity aerobic exercise, which then returned to the pre-exercise level within several hours post-exercise. Resistance exercise, regardless of its intensity, did not significantly influence CAMs.

Conclusion

It is evident that the responses of CAMs are dependent upon the type and intensity of exercise performed. The most common, favorable outcome was a decrease in CAMs following low-to-moderate intensity aerobic exercise, while high-intensity aerobic exercise showed a short-lived, momentary increase in CAMs, which returned to the pre-exercise level within a few hours post-exercise. Resistance exercise, regardless of its intensity, neither significantly increased nor decreased CAMs. Future studies should focus more on the role of exercise in both soluble and membrane-bound CAMs as well as proinflammatory cytokines related to atherosclerosis in order to develop specific exercise programing that can effectively improve vascular inflammation and endothelial health.

Exercise-induced changes in stress hormones and cell adhesion molecules in obese men

Purpose

The current study examined the relationship between exercise-induced changes in stress hormones (epinephrine, norepinephrine, and cortisol) and vascular inflammatory markers (soluble intracellular adhesion molecule-1 [sICAM-1], soluble endothelial selectin [sE-selectin], and soluble vascular adhesion molecule-1 [sVCAM-1]) in obese men over a 24-hour period following exercise at lower and higher intensity.

Patients and methods

Fifteen physically inactive, obese, college-aged men performed a single bout of cycling exercise at lower and higher intensities (lower intensity: 50% of maximal heart rate, and higher intensity: 80% of maximal heart rate) in random order. Overnight fasting blood samples were collected at baseline, immediately postexercise (IPE), 1-hour PE (1-h PE), and 24-hour PE. Changes in stress hormones and inflammatory markers were analyzed with a repeated-measures analysis of variance using Bonferroni multiple comparisons and a linear regression analysis (p<0.05).

Results

sICAM-1, sVCAM-1, epinephrine, and norepinephrine did not change over time, while sE-selectin was significantly lower at 1-h PE (10.25±1.07 ng/mL, p=0.04) than at baseline (12.22±1.39 ng/mL). Cortisol and sICAM-1 were negatively related at 1-h PE following lower-intensity exercise (r²=0.34, p=0.02), whereas cortisol and sVCAM-1 were positively related at IPE following higher-intensity exercise (r²=0.36, p=0.02).

Conclusion

Regardless of intensity, an acute bout of aerobic exercise may lower sE-selectin in sedentary obese men. Responses of cortisol are dependent on exercise intensity, and cortisol may be a key stress hormone playing a major role in regulating sICAM-1 and sVCAM-1.

Acute impact of conventional and eccentric cycling on platelet and vascular function in patients with chronic heart failure

Evidence-based guidelines recommend exercise therapy for patients with chronic heart failure (CHF). Such patients have increased atherothrombotic risk. Exercise can transiently increase platelet activation and reactivity and decrease vascular function in healthy participants, although data in CHF are scant. Eccentric (ECC) cycling is a novel exercise modality that may be particularly suited to patients with CHF, but the acute impacts of ECC cycling on platelet and vascular function are currently unknown. Our null hypothesis was that ECC and concentric (CON) cycling, performed at matched external workloads, would not induce changes in platelet or vascular function in patients with CHF. Eleven patients with heart failure with reduced ejection fraction (HFrEF) took part in discrete bouts of ECC and CON cycling. Before and immediately after exercise, vascular function was assessed by measuring diameter and flow-mediated dilation (FMD) of the brachial artery. Platelet function was measured by the flow cytometric determination of glycoprotein IIb/IIIa activation and granule exocytosis in the presence and absence of platelet agonists. ECC cycling increased baseline artery diameter (pre: 4.0 ± 0.8 mm vs. post: 4.2 ± 0.7 mm; P = 0.04) and decreased FMD%. When changes in baseline artery diameter were accounted for, the decrease in FMD post-ECC cycling was no longer significant. No changes were apparent after CON. Neither ECC nor CON cycling resulted in changes to any platelet-function measures (all P > 0.05). These results suggest that both ECC and CON cycling, at a moderate intensity and short duration, can be performed by patients with HFrEF without detrimental impacts on vascular or platelet function.NEW & NOTEWORTHY This is the first evidence to indicate that eccentric (ECC) cycling can be performed relatively safely by patients with chronic heart failure (CHF), as it did not result in impaired vascular or platelet function compared with conventional cycling. This is important, as acute exercise can transiently increase atherothrombotic risk, and ECC cycling is a novel exercise modality that may be particularly suited to patients with CHF.

Effects of a single bout of strenuous exercise on platelet activation in female ApoE/LDLR-/- mice

Strenuous physical exercise leads to platelet activation that is normally counterbalanced by the production of endothelium-derived anti-platelet mediators, including prostacyclin (PGI₂) and nitric oxide (NO). However, in the case of endothelial dysfunction, e.g. in atherosclerosis, there exists an increased risk for intravascular thrombosis during exercise that might be due to an impairment in endothelial anti-platelet mechanisms. In the present work, we evaluated platelet activation at rest and following a single bout of strenuous treadmill exercise in female ApoE/LDLR^-/- mice with early (3-month-old) and advanced (7-month-old) atherosclerosis compared to female age-matched WT mice. In sedentary and post-exercise groups of animals, we analyzed TXB₂ generation and the expression of platelet activation markers in the whole blood ex vivo assay. We also measured pre- and post-exercise plasma concentration of 6-keto-PGF_1α, nitrite/nitrate, lipid profile, and blood cell count. Sedentary 3- and 7-month-old ApoE/LDLR^-/- mice displayed significantly higher activation of platelets compared to age-matched wild-type (WT) mice, as evidenced by increased TXB₂ production, expression of P-selectin, and activation of GPIIb/IIIa receptors, as well as increased fibrinogen and von Willebrand factor (vWf) binding. Interestingly, in ApoE/LDLR^-/- but not in WT mice, strenuous exercise partially inhibited TXB₂ production, the expression of activated GPIIb/IIIa receptors, and fibrinogen binding, with no effect on the P-selectin expression and vWf binding. Post-exercise down-regulation of the activated GPIIb/IIIa receptor expression and fibrinogen binding was not significantly different between 3- and 7-month-old ApoE/LDLR^-/- mice; however, only 7-month-old ApoE/LDLR^-/- mice showed lower TXB₂ production after exercise. In female 4-6-month-old ApoE/LDLR^-/- but not in WT mice, an elevated pre- and post-exercise plasma concentration of 6-keto-PGF_1α was observed. In turn, the pre- and post-exercise plasma concentrations of nitrite (NO₂^-) and nitrate (NO₃^-) were decreased in ApoE/LDLR^-/- as compared to that in age-matched WT mice. In conclusion, we demonstrated overactivation of platelets in ApoE/LDLR^-/- as compared to WT mice. However, platelet activation in ApoE/LDLR^-/- mice was not further increased by strenuous exercise, but was instead attenuated, a phenomenon not observed in WT mice. This phenomenon could be linked to compensatory up-regulation of PGI₂-dependent anti-platelet mechanisms in ApoE/LDLR^-/- mice.

Effect of Aspirin Supplementation on Hemostatic Responses in Firefighters Aged 40 to 60 Years

Sudden cardiovascular events account for approximately 45% to 50% of all duty-related deaths among firefighters and a disproportionate number of these fatalities occur after strenuous fire suppression activities. The purpose of this study was to evaluate the effect of acute and chronic aspirin supplementation on hemostatic function before and after live firefighting activities in older firefighters. A double-blind, crossover design included 4 treatments: a 2-week aspirin/placebo treatment ("chronic") and a single prefirefighting aspirin/placebo treatment ("acute"). Hemostatic function was assessed in 24 male firefighters (mean age = 48.2 ± 5.9 years) immediately before and after 18 minutes of live-fire firefighting activity. An acute bout of firefighting activity significantly decreased platelet aggregation time and decreased activated partial thromboplastin time. Compared with placebo, acute aspirin supplementation resulted in a significant increase in epinephrine closure time, which was further augmented by chronic supplementation. Aspirin supplementation had no effect on coagulatory or fibrinolytic factors. Our findings suggest that an acute bout of firefighting leads to increased coagulatory potential in older firefighters. In conclusion, aspirin supplementation had an antiplatelet effect that decreased platelet aggregability at rest and after an acute bout of firefighting compared with placebo.

Meal-induced platelet activation in diabetes mellitus type 1 or type 2 is related to postprandial insulin rather than glucose levels

AIM

Postprandial platelet activation was related to postprandial insulin rather than glucose levels in a previous meal insulin study in type 2 diabetes mellitus (T2DM). We therefore compared postprandial platelet activation in type 1 (T1DM) patients without insulin secretion and T2DM patients with high postprandial insulin levels.

MATERIAL AND METHODS

Patients with T1DM (n=11) and T2DM (n=12) were studied before and 90min after a standardized meal without premeal insulin. Five T1DM patients volunteered for a restudy with their regular premeal insulin. Platelet activation was assessed by flow cytometry, with and without the thromboxane analogue U46619 or ADP, and by whole blood aggregometry (Multiplate®). Effects of insulin (100μU/mL) in vitro were also studied.

RESULTS

Before the meal, glucose, insulin and platelet activation markers other than platelet-leukocyte aggregates (PLAs) were similar in T1DM and T2DM; PLAs were higher in T1DM. Postprandial glucose levels increased more markedly in T1DM (to 22.1±1.4 vs. 11.2±0.6mmol/L) while insulin levels increased only in T2DM (from 24.4±4.4 to 68.8±12.3μU/mL). Platelet P-selectin expression, fibrinogen binding and PLA formation stimulated by U46619 were markedly enhanced (approximately doubled) and whole blood aggregation stimulated by U46619 was increased (p<0.05 for all) after the meal in T2DM patients but not in T1DM patients. The pilot study with premeal insulin in T1DM patients showed postprandial platelet activation when postprandial insulin levels increased. In vitro insulin mildly activated platelets in both groups.

CONCLUSION

Postprandial platelet activation via the thromboxane pathway is related to postprandial hyperinsulinemia and not to postprandial hyperglycaemia in patients with diabetes.

Strenuous exercise induces a hyperreactive rebalanced haemostatic state that is more pronounced in men

Physical exercise is recommended for a healthy lifestyle. Strenuous exercise, however, may trigger the haemostatic system, increasing the risk of vascular thrombotic events and the incidence of primary cardiac arrest. Our goal was to study the effects of strenuous exercise on risk factors of cardiovascular disease. Blood was collected from 92 healthy volunteers who participated in the amateur version of the pro-tour Amstel Gold cycling race, before and directly after the race. Thrombin generation showed a shortening of the lag time and time to peak and an increase of the velocity index. Interestingly, the endogenous thrombin potential measured in plasma decreased due to reduced prothrombin conversion. Platelet reactivity increased and this effect was stronger in men than in women. Lower fibrinogen and higher D-dimer levels after exercise indicated higher fibrin formation. On the other hand, fibrinolysis was also elevated as indicated by a shortening of the clot lysis time. Exercise activated the endothelium (von Willebrand factor (VWF) and active VWF levels were elevated) and the immune system (concentrations IL-6, IL-8, MCP-1, RANTES and PDGF increased). Additionally, an increased cardiac troponin T level was measured post-exercise. Strenuous exercise induces a temporary hyperreactive state in the body with enhanced pro- and anticoagulant responses. As strenuous exercise has a more pronounced effect on platelet function in male subjects, this gives a possible explanation for the higher incidence of sudden cardiac death during exercise compared to women. This trial is registered at www.clinicaltrials.gov as NCT02048462.

Neutrophil extracellular traps: a walk on the wild side of exercise immunology

Intense exercise evokes a rapid and transient increase in circulating cell-free DNA (cf-DNA), a phenomenon that is commonly observed in a variety of acute and chronic inflammatory conditions. While the potential value of cf-DNA for the prediction of disease outcome and therapeutic response is well documented, the release mechanisms and biological relevance of cf-DNA have long remained enigmatic. The discovery of neutrophil extracellular traps (NETs) provided a novel mechanistic explanation for increased cf-DNA levels. Now there is increasing evidence that NETs may contribute to cf-DNA in diverse infectious, non-infectious and autoinflammatory conditions, as well as in response to acute exercise. NETs have now been firmly established as a fundamental immune mechanism used by neutrophils to respond to infection and tissue injury. On the other side, aberrant formation of NETs appears to be a driving force in the pathogenesis of autoimmunity and cardiovascular disease. Thus, the emergence of NETs in the 'exercising vasculature' raises important questions considering beneficial effects, as well as occasional adverse effects, of exercise on immune homeostasis. This review gives an overview of the current state of research into the mechanisms of how NETs are released, contribute to host defence and participate in inflammatory disorders. We discuss the impact of exercise-induced NETs, considering a potentially beneficial role in the prevention of lifestyle-related diseases, as well as putative detrimental effects that may arise in elite sports. Finally, we propose that exercise-induced cf-DNA responses could be exploited for diagnostic/prognostic purposes to identify individuals who are at increased risk of cardiovascular events or autoimmunity.

Influence of High Polyphenol Beverage on Stress-Induced Platelet Activation

OBJECTIVES

Platelets are playing a crucial role in acute cardiovascular events. We investigated if physical stress activates platelets and whether this activation can be inhibited by a polyphenol-enriched diet.

METHODS

Blood samples were taken from a total of 103 athletes three weeks before, one day before, immediately as well as 24 hours and 72 hours after a marathon run. Participants were randomized, double-blinded and divided into two groups. One group received a polyphenol-rich beverage the other the same beverage without polyphenols. Besides analysis of platelet counts and impedance-aggregometric-measurement of platelet activity, soluble P-selectin and Endothelin-A measurements were performed.

RESULTS

In the control group, runners showed a 2.2-fold increased platelet aggregation directly after completing a marathon and within the following three days when compared with baseline values (p<0.01). In accordance, significant increases in sP-selectin (57.52ng/ml vs. 94.86ng/ml;p<0.01) were detectable. In contrast, for the group consuming a beverage with increased polyphenol content (upper quartile of study beverage intake) we did not find any increase of platelet aggregation.

DISCUSSION

Physical stress causes a significant increase in platelet activity. Our results demonstrate that a diet enriched in polyphenols is capable of preventing platelet activation. These findings might indicate a diminished cardiovascular stress-reaction following pre-exposition to polyphenol-enriched diet.

Effect of physical training on indices of platelet aggregation and fibrinogen concentration in patients with chronic heart failure

OBJECTIVE

The aim of this study was to determine the effect of long-term physical load on the changes in the fibrinogen concentration and platelet aggregation.

MATERIAL AND METHODS

Platelet aggregation was investigated in 144 patients while fibrinogen concentration in 138 patients with CHF. The patients were divided into the groups of the trained patients and the controls and were investigated as follows: on admission to the hospital (stage 1); after treatment in the hospital (stage 2); after 3 months (stage 3); after 6 months (stage 4); and after 1 year (stage 5). The indices were investigated before and after physical load.

RESULTS

It was determined that fibrinogen concentration significantly increased after physical load in all the treatment stages in both groups of the patients (P=0.045). In the course of the treatment, fibrinogen concentration gradually decreased in the group of the trained patients (P=0.02). Platelet aggregation investigated with ADP significantly increased after physical load in all the stages in both groups of the patients and decreased during the different investigation stages in the groups of the untrained (P=0.02) and trained patients. Platelet aggregation investigated with ADR consistently decreased before physical load during the different investigation stages in the groups of the trained (difference is not significant) and untrained patients (P=0.02).

CONCLUSIONS

Physical training reduces fibrinogen concentration in patients with CHF. It remains unclear whether physical training can have an effect on the decrease in platelet aggregation in patients who have long-term physical training applied.

Effects of Physical (In)activity on Platelet Function

As platelet activation is closely related to the liberation of growth factors and inflammatory mediators, platelets play a central role in the development of CVD. Virtually all cardiovascular risk factors favor platelet hyperreactivity and, accordingly, also physical (in)activity affects platelet function. Within this paper, we will summarize and discuss the current knowledge on the impact of acute and habitual exercise on platelet function. Although there are apparent discrepancies regarding the reported effects of acute, strenuous exercise on platelet activation, a deeper analysis of the available literature reveals that the applied exercise intensity and the subjects' cardiorespiratory fitness represent critical determinants for the observed effects. Consideration of these factors leads to the summary that (i) acute, strenuous exercise can lead to platelet activation, (ii) regular physical activity and/or physical fitness diminish or prevent platelet activation in response to acute exercise, and (iii) habitual physical activity and/or physical fitness also favorably modulate platelet function at physical rest. Notably, these effects of exercise on platelet function show obvious similarities to the well-recognized relation between exercise and the risk for cardiovascular events where vigorous exercise transiently increases the risk for myocardial infarction and a physically active lifestyle dramatically reduces cardiovascular mortality.

Effects of acute and chronic exercise in patients with essential hypertension: benefits and risks

The importance of regular physical activity in essential hypertension has been extensively investigated over the last decades and has emerged as a major modifiable factor contributing to optimal blood pressure control. Aerobic exercise exerts its beneficial effects on the cardiovascular system by promoting traditional cardiovascular risk factor regulation, as well as by favorably regulating sympathetic nervous system (SNS) activity, molecular effects, cardiac, and vascular function. Benefits of resistance exercise need further validation. On the other hand, acute exercise is now an established trigger of acute cardiac events. A number of possible pathophysiological links have been proposed, including SNS, vascular function, coagulation, fibrinolysis, and platelet function. In order to fully interpret this knowledge into clinical practice, we need to better understand the role of exercise intensity and duration in this pathophysiological cascade and in special populations. Further studies in hypertensive patients are also warranted in order to clarify the possibly favorable effect of antihypertensive treatment on exercise-induced effects.

Exercise-induced changes in inflammatory processes: Implications for thrombogenesis in cardiovascular disease

Sedentary lifestyle is a risk factor and a strong predictor for chronic disease and premature death. Low-grade inflammation has been proved a key player in the pathogenesis of cardiovascular disease. Inflammatory processes have been also involved in maintaining the balance between coagulation and fibrinolysis. In addition, an inverse linear dose-response relation between physical activity and mortality risks has also been reported. However, the favorable effects of structured exercise programs and the independent contribution of physical activity to cardiovascular risk are still under investigation. In response to heavy exercise, interleukin-6 (IL-6) is secreted by contracting skeletal muscles, followed by an acute reactant release of C-reactive protein (CRP). Both CRP and IL-6 can stimulate monocyte tissue factor production, provoke platelet hyperreactivity, promote fibrinogen biosynthesis, and enhance microparticle formation and erythrocyte aggregability, thus triggering prothrombotic state. By contrast, regular exercise and physical activity are protective against all-cause mortality through suppressing pro-inflammatory cytokine production, enhancing anti-inflammatory mediators and antioxidant development, and promoting fibrinolytic activity. Low-load resistance exercise also plays an advantageous role in thrombogenesis by reducing inflammatory processes and potentiating fibrinolytic features. In the present review article, we provide an overview of the impact of different modes and intensities of physical activity on vascular inflammation and thrombogenesis.

Effects of high-amount-high-intensity exercise on in vivo platelet activation: modulation by lipid peroxidation and AGE/RAGE axis

Physical activity is associated with cardiovascular risk reduction, but the effects of exercise on platelet activation remain controversial. We investigated the effects of regular high-amount, high intensity aerobic exercise on in vivo thromboxane (TX)-dependent platelet activation and plasma levels of platelet-derived proteins, CD40L and P-selectin, and whether platelet variables changes may be related to changes in high-density lipoprotein (HDL) and in the extent of oxidative stress and oxidative stress-related inflammation, as reflected by urinary isoprostane excretion and endogenous soluble receptor for advanced glycation end-products (esRAGE), respectively. Urinary excretion of 11-dehydro-TXB₂ and 8-iso-prostaglandin (PG)F(2α) and plasma levels of P-selectin, CD40L and esRAGE were measured before and after a eight-week standardised aerobic high-amount-high-intensity training program in 22 sedentary subjects with low-to-intermediate risk. Exercise training had a clear beneficial effect on HDL cholesterol (+10%, p=0.027) and triglyceride (-27%, p=0.008) concentration. In addition, a significant (p<0.0001) decrease in urinary 11-dehydro-TXB₂ (26%), 8-iso-PGF(2α) (21%), plasma P-selectin (27%), CD40L (35%) and a 61% increase in esRAGE were observed. Multiple regression analysis revealed that urinary 8-iso-PGF(2α) [beta=0.33, SEM=0.116, p=0.027] and esRAGE (beta=-0.30, SEM=31.3, p=0.046) were the only significant predictors of urinary 11-dehydro-TXB₂ excretion rate over the training period. In conclusion, regular high-amount-high-intensity exercise training has broad beneficial effects on platelet activation markers, paralleled and possibly associated with changes in the lipoprotein profile and in markers of lipid peroxidation and AGE/RAGE axis. Our findings may help explaining why a similar amount of exercise exerts significant benefits in preventing cardiovascular events.

Effect of aerobic interval training and caffeine on blood platelet function

PURPOSE

Hyperactive platelets contribute to the thrombotic response in humans, and exercise transiently increases platelet function. Caffeine is routinely used by athletes as an ergogenic aid, but the combined effect of exercise and caffeine on platelet function has not been investigated.

METHODS

Twelve healthy males were randomly assigned to one of four groups and undertook four experimental trials of a high-intensity aerobic interval training (AIT) bout or rest with ingestion of caffeine (3 mg·kg(-1)) or placebo. AIT was 8 × 5 min at approximately 75% peak power output (approximately 80% V˙O2peak) and 1-min recovery (approximately 40% peak power output, approximately 50% V˙O2peak) intervals. Blood/urine was collected before, 60, and 90 min after capsule ingestion and analyzed for platelet aggregation/activation.

RESULTS

AIT increased platelet reactivity to adenosine diphosphate (placebo 30.3%, caffeine 13.4%, P < 0.05) and collagen (placebo 10.8%, caffeine 5.1%, P < 0.05) compared with rest. Exercise placebo increased adenosine diphosphate-induced aggregation 90 min postingestion compared with baseline (40.5%, P < 0.05), but the increase when exercise was combined with caffeine was small (6.6%). During the resting caffeine protocol, collagen-induced aggregation was reduced (-4.3%, P < 0.05). AIT increased expression of platelet activation marker PAC-1 with exercise placebo (P < 0.05) but not when combined with caffeine.

CONCLUSION

A single bout of AIT increases platelet function, but caffeine ingestion (3 mg·kg(-1)) does not exacerbate platelet function at rest or in response to AIT. Our results provide new information showing caffeine at a dose that can elicit ergogenic effects on performance has no detrimental effect on platelet function and may have the potential to attenuate increases in platelet activation and aggregation when undertaking strenuous exercise.

Postprandial platelet activation is related to postprandial plasma insulin rather than glucose in patients with type 2 diabetes

Postprandial hyperglycemia is associated with platelet activation. We thus investigated if meal-induced platelet activation could be attenuated by meal insulin. A randomized, double-blind, cross-over study was performed to compare postprandial platelet activation after premeal injections of placebo or insulin aspart (0.1 and 0.2 units/kg) in 18 patients with type 2 diabetes mellitus (T2DM). Platelet activation was assessed by flow cytometry, without and with stimulation by the thromboxane analog U46619 or ADP. Measurements were before and after premeal blood glucose standardization (to 6-7 mmol/L by insulin infusion, if needed) and at 90 min after the meal. Premeal insulin reduced postprandial hyperglycemia by 2-3 mmol/L compared with placebo. Postmeal insulin levels were doubled with placebo and further elevated with insulin injections. The standardized meal enhanced U46619-induced platelet P-selectin expression by 23% after placebo; this response was more than doubled after premeal insulin. U46619-induced fibrinogen binding was unchanged after meal intake with placebo but was markedly enhanced (by ~50-60%) after premeal insulin. Postprandial platelet activation correlated positively to postprandial insulin levels and inversely to glucose levels. Premeal insulin infusion was also associated with platelet activation. Our results suggest that postprandial insulin rather than glucose accounts for postprandial platelet activation in T2DM patients.

Platelets selectively enhance lymphocyte adhesion on subendothelial matrix under arterial flow conditions

Platelet adhesion at sites of cardiovascular injury may facilitate leukocyte deposition. We asked if and how platelets enhance lymphocyte adhesion on different subendothelial matrix protein (SEMP)-coated surface at arterial shear stress. Hirudinised whole blood was subjected to an arterial shear rate (500 s(-1)) in a Cone and Plate(let) analyser (CPA) for 5 minutes using plates coated with bovine serum albumin (BSA), collagen, fibrinogen, von Willebrand factor (vWF), or fibronectin. Platelet and lymphocyte adhesion were monitored by CPA and flow cytometry. Exposure of blood to collagen, fibrinogen, and vWF-coated surfaces induced platelet activation. The most marked effect was seen with collagen-coating, which markedly enhanced the adhesion of all lymphocyte subpopulations compared to BSA-coating. Fibrinogen-coating supported both T and NK cell adhesion, while vWF-coated surface only enhanced NK cell deposition. In contrast, fibronectin enhanced neither platelet activation nor lymphocyte adhesion. Moreover, platelets preferentially facilitated adhesion of large CD4(+) and CD8(+) T cells and NK cells, and of small B cells. Enhanced cell adhesion of larger lymphocytes was associated with elevated platelet conjugation and higher lymphocyte expression of PSGL-1, Mac-1, and CD40L. The enhancement of lymphocyte adhesion was totally platelet-dependent, and was abolished in platelet-depleted blood. Moreover, blockade of the platelet adhesion molecules P-selectin, GPIIb/IIIa, and CD40L attenuated platelet-dependent lymphocyte deposition. In conclusion, platelets support lymphocyte adhesion on SEMP-coated surfaces under arterial shear. The enhancement is selective for large T and NK cells and small B cells.

Thrombosis, physical activity, and acute coronary syndromes

Acute coronary syndromes (ACS) are common, life-threatening cardiac disorders that typically are triggered by rupture or erosion of an atherosclerotic plaque. Platelet deposition and activation of the blood coagulation cascade in response to plaque disruption lead to the formation of a platelet-fibrin thrombus, which can grow rapidly, obstruct coronary blood flow, and cause myocardial ischemia and/or infarction. Several clinical studies have examined the relationship between physical activity and ACS, and numerous preclinical and clinical studies have examined specific effects of sustained physical training and acute physical activity on atherosclerotic plaque rupture, platelet function, and formation and clearance of intravascular fibrin. This article reviews the available literature regarding the role of physical activity in determining the incidence of atherosclerotic plaque rupture and the pace and extent of thrombus formation after plaque rupture.

Eicosanoid Production following One Bout of Exercise in Middle-Aged African American Pre- and Stage 1 Hypertensives

Endothelial dysfunction and a sedentary lifestyle may be involved in the development of hypertension which is proliferative among middle-aged African Americans (AA). Signaling molecules derived from the oxidation of 20-carbon fatty acid molecules known as eicosanoids influence vascular tone. The relationship between aerobic fitness and eicosanoid formation following exercise in middle-aged African American hypertensives is unknown. Purpose. To determine the relationship between aerobic capacity and eicosanoid formation after a bout of moderate-intensity exercise in middle-aged AA hypertensives. Methods. Ten sedentary hypertensive AA underwent 50 min of aerobic exercise at 65% VO₂max. Urine was collected for 24 hr on two occasions, prior to testing and immediately following the bout of exercise. Urinary metabolites of prostacyclin (6-keto PGF_1α) and thromboxane (11-dTXB₂) were measured during the day and night periods by high-performance liquid chromatography (HPLC). Results. 6-keto PGF_1α levels significantly increased (P = .04) following the bout of exercise compared to the control day. There was a significant relationship (r = .49, P < .05) between 6-keto PGF_1α levels and VO₂max during the exercise day. Conclusion. Based on this preliminary study, there appears to be a relationship between aerobic capacity and exercise-induced 6-keto PGF_1α production in middle-aged hypertensive AAs. AAs with lower VO₂max had lower 6-keto PGF_1α formation.

Short-term treadmill running as a model for studying cell-free DNA kinetics in vivo

BACKGROUND

Increased plasma concentrations of cell-free DNA (cf-DNA) are considered a hallmark of various clinical conditions. Despite intensive research in this field, limited data are available concerning the time course of release and clearance of cf-DNA in vivo.

METHODS

We extracted cf-DNA from plasma samples taken before and immediately after a 10-km cross-country run, and from samples taken before, immediately after, and 30 min after exhaustive short-term treadmill exercise. The contribution of nuclear (nDNA) and mitochondrial DNA (mtDNA) was measured by quantitative real-time PCR. The incremental treadmill exercise setup was exploited to delineate the precise sequencing and timing of cf-nDNA, lactate, and high-mobility group box 1 protein (HMGB1) release during the exercise and recovery phases.

RESULTS

Postexercise plasma cf-nDNA concentrations in cross-country and treadmill runners were significantly increased, by 7.6-fold and 9.9-fold, respectively (P < 0.001). cf-nDNA concentrations were not correlated with age, sex, or body mass index. Plasma concentrations of cf-nDNA and HMGB1 in postexercise samples of treadmill runners were significantly correlated (r = 0.84; P = 0.004). cf-mtDNA concentrations were not affected by treadmill exercise. Time-course analyses demonstrated that cf-nDNA is released within minutes after the onset of exercise and is rapidly cleared from the circulation after the cessation of exercise. Nearly congruent kinetics for cf-nDNA, lactate, and HMGB1 were observed during the exercise phase.

CONCLUSIONS

A single bout of exhaustive short-term treadmill exercise constitutes a versatile model system suitable for addressing basic questions about cf-DNA biology.

Cardiovascular screening in young athletes in Sarajevo Canton

Potential risk of sudden death during sports participation makes screening of competitive athletes of vital importance. Congenital cardiac anomalies and non-atherosclerotic, acquired myocardial conditions are primary causes underlying exercise-induced cardiac death in young patients. Since cardiovascular conditions are the leading causes of non-traumatic, exercise-induced cardiac events, cardiovascular screening preceding sports participation in mandatory. The objectives of this study were to determine prevalence of cardiac conditions through cardiovascular screening of young athletes and to establish preventive strategy. The study was conducted at the Sports Medicine Center of Sarajevo Canton and at the Pediatric Clinic of University of Sarajevo Clinics Centre in the period 2007-2009. The study was supported by Canton Sarajevo Ministry of Health and Ministry of sports, science and culture. The study targeted a group of 214 athletes, 8-18 years of age with average age being 15.26. The group was subdivided into five groups according to the age. After taking the anamnesis (family, personal and cardiological) patients were subjected to the measuring of body mass and height, blood pressure and heart rate and oxygen saturation, recording of 12-lead ECG, specialist examination (pediatrician, sports medicine specialist and cardiologist) and complete heart echocardiography. No examined athletes expressed subjective discomfort. Congenital cardiac anomalies were not diagnosed in any athlete. Also, cardiovascular abnormalities requiring additional evaluation, positive cardiac anamnesis, abnormal auscultatory findings, hypertension or abnormal ECG findings were not recognized in any patient. Moderate correlation was found among the left ventricle mass and heart rate (p<0.05). In order to minimalize or even possibly prevent the risk of sudden cardiac death it is necessary to establish an adequate strategy of cardiovascular screening of young athletes.

Platelet reactivity in diabetic patients subjected to acute exercise stress test

BACKGROUND

Previous studies have reported ambiguous results regarding the effect of acute exercise on platelet reactivity in healthy and cardiac patients.

OBJECTIVES

We aimed to assess platelet reactivity among diabetic patients before and immediately after an acute exercise stress test.

METHODS

Patients (controls: mean age 53.1 ± 12.1 years; four males; body mass index 27.0 ± 5.7 kg/m(2); HbA(1c) 6.0 ± 1.1%, n = 8) and diabetic patients (52.9 ± 11.3; six males; body mass index 30.7 ± 2.2 kg/m(2); HbA(1c) 7.8 ± 1.7%, n = 8) referred for diagnostic nuclear exercise stress test were recruited. Blood samples obtained at rest and immediately post-exercise were stimulated with adenosine diphosphate (ADP), collagen and arachidonic acid. Expression of CD41 (pan-platelet marker) and CD62p (platelet stimulation marker) were measured by flow cytometry. Aspirin responsiveness was measured using VerifyNow.

RESULTS

Although peak systolic blood pressure was significantly higher in the diabetics compared with nondiabetics (186.3 ± 25.4 vs. 157.1 ± 19.1, respectively, P = .028), peak exercise heart rate was similar (156.5 ± 8.3 vs. 155.5 ± 12.1 for diabetics and nondiabetics, respectively). No differences were observed between groups for aspirin resistance. Platelet stimulation with ADP exhibited significantly lower CD62p-positive cell population (%) in the diabetic patients both prior to and following the exercise stress test (P = .03). In addition, although not significant, platelet stimulation was higher post-exercise in the diabetic patients (6.3 ± 4.7% vs. 12.0 ± 5.6%, for pre- and post-exercise, respectively, P = .2) with no difference in controls (9.2 ± 5.5% vs. 8.9 ± 5.9%).

CONCLUSION

Platelet stimulation in diabetic patients is blunted and might be explained by the prolonged exposure of platelets to multiple diabetic risk factors.

Inflammatory cytokines and atrial fibrillation: current and prospective views

Atrial fibrillation (AF) is the most common sustained arrhythmia and a challenging clinical problem encountered in daily clinical practice. There is an increasing body of evidence linking inflammation to a broad spectrum of cardiovascular conditions including AF. Historical evidence supports an association between AF and inflammation and is consistent with the association of AF with inflammatory conditions of the heart, such as myocarditis and pericarditis. AF has been associated with myocardial oxidative stress, and antioxidant agents have demonstrated antiarrhythmic benefit in humans. Increased plasma interleukin (IL)-6, C-reactive protein (CRP), and plasma viscosity support the existence of an inflammatory state among "typical" populations with chronic AF. These indexes of inflammation are related to the prothrombotic state and may be linked to the clinical characteristics of the patients (underlying vascular disease and comorbidities), rather than simply to the presence of AF itself. It has been suggested that inflammation may have a role in the development of atrial arrhythmias after cardiac surgery, and that a genetic predisposition to develop postoperative complications exists. Cytokines can have a prognostic significance; IL-6 levels, CRP, and other cytokines may have prognostic value in AF. Cytokine lowering therapies, statins, angiotensin converting enzyme inhibitors and other anti-inflammatory agents may have a role in the treatment of AF. The present article provides an overview of the evidence linking inflammatory cytokines to AF and their therapeutic and prognostic implications.

Predictors of exercise-induced platelet reactivity in patients with chronic stable angina

OBJECTIVE

Previous studies have shown that exercise increases platelet reactivity in patients with coronary artery disease (CAD). However, the response of platelet reactivity to exercise is considerably variable and its predictors are poorly known.

METHODS

We studied 214 consecutive patients (age 61.9 +/- 9 years, 167 men) with stable angina and obstructive coronary artery disease. All patients underwent a symptom-limited treadmill exercise stress test. Venous blood samples were collected before and at peak exercise. Platelet reactivity was assessed by the platelet function analyzer system as the time for flowing whole blood to occlude a collagen-adenosine diphosphate ring (closure time: shorter times = higher reactivity). Both closure time at peak exercise and the exercise-induced change in closure time from rest were assessed as an expression of exercise-related platelet reactivity.

RESULTS

Closure time decreased significantly with exercise in the whole population (from 95.9 +/- 22 to 81.2 +/- 18 s, P < 0.001). The only variable significantly associated with closure time at peak exercise was hematocrit (P = 0.003). Basal systolic blood pressure (P = 0.023) and lack of nitrate use (P = 0.03), on the contrary, were the only variables significantly associated with increased exercise-induced closure time change. Peak hematocrit maintained an independent association with peak closure time in multivariable analysis, although the correlation was mild. No variable, on the contrary, was associated with exercise-induced platelet reactivity after correction for basal closure time values at multivariable analyses.

CONCLUSION

Among stable coronary artery disease patients, platelet reactivity after exercise cannot be reliably predicted by several common clinical and laboratory variables.

Influence of statin treatment on platelet inhibition by clopidogrel - a randomized comparison of rosuvastatin, atorvastatin and simvastatin co-treatment

OBJECTIVES

Possible interactions between clopidogrel and atorvastatin, simvastatin or rosuvastatin (a 'non-CYP3A4' metabolized statin) were investigated in a randomized prospective study using sensitive and specific ex vivo platelet function tests.

METHODS

Patients with coronary artery disease participating in a double-blind study comparing lipid-lowering effects of atorvastatin (20-80 mg OD; n = 22) and rosuvastatin (10-40 mg OD; n = 24) were studied before and after 2 weeks treatment with clopidogrel 75 mg OD after completed statin dose titration. In addition, 23 patients were randomized to open-label simvastatin 40 mg OD.

RESULTS

Clopidogrel inhibited 10 mumol L(-1) ADP-induced platelet aggregation by 40 +/- 27%, 57 +/- 28% and 51 +/- 29%, respectively, in patients on rosuvastatin, atorvastatin and simvastatin treatment. The other platelet tests yielded similar results. No dose-dependent effects of rosuvastatin or atorvastatin co-treatment on clopidogrel efficacy were observed.

CONCLUSIONS

Treatment with CYP3A4 metabolized statins, atorvastatin or simvastatin, did not attenuate the platelet inhibitory effect of clopidogrel maintenance treatment compared with the non-CYP3A4 metabolized, rosuvastatin.

Effect of exercise on platelet activation during aspirin or clopidogrel intake in healthy men

Sudden strenuous exercise increases the risk of ischemic cardiac events in patients with coronary artery disease. The exact mechanism behind this observation is unknown, but platelet activation induced by exercise may be of importance. We hypothesized that brief strenuous exercise would activate platelets in healthy men, assessed by the Platelet Function Analyzer 100 and light transmittance aggregometry. Nearly all participants exhibited increased platelet reactivity after exercise measured by the Platelet Function Analyzer 100, whereas only minor changes were detected by light transmittance aggregometry. A significant increase in plasma von Willebrand Factor was also found in response to exercise. In conclusion, platelet activation occurs during exercise in healthy individuals. This activation is not prevented by use of aspirin or clopidogrel, and may partly be explained by an increase in plasma von Willebrand Factor.

Longitudinal platelet reactivity to acute psychological stress among older men and women

Platelet reactivity to acute stress is associated with increased cardiovascular disease risk; however, little research exists to provide systematic methodological foundations needed to generate strong longitudinal research designs. Study objectives were: 1) to evaluate whether markers of platelet function increase in response to an acute psychological stress test among older adults, 2) to establish whether reactivity remains robust upon repeated administration (i.e. three occasions approximately 1 year apart), and 3) to evaluate whether two different acute speech stress tasks elicit similar platelet responses. The 149 subjects (mean age 71 years) gave a brief impromptu speech on one of two randomly assigned topics involving interpersonal conflict. Blood samples drawn at baseline and post-speech were assayed using flow cytometry for platelet responses on three outcomes (% aggregates, % P-selectin expression, and % fibrinogen receptor expression). Three-level hierarchical linear modeling analyses revealed significant stress-induced increases in platelet activation on all outcomes (p < 0.001). No significant habituation on any measure was found. Additional reactivity differences were associated with male gender, history of myocardial infarction, and use of aspirin, statins, and antidepressants. The results demonstrate that laboratory acute stress tests continued to produce robust platelet reactivity on three activation markers among older adults over 3 years.

Treadmill exercise in claudicants on aspirin results in improved antioxidant status but only minimal platelet activation

The consequence of exercise on platelets remains controversial and adverse effects may result from repeated ischaemia reperfusion injury. We investigated platelet activation (platelet P-selectin (PS), and activated glycoprotein (Gp) IIb/IIIa), platelet-monocyte aggregates (PMA) and total plasma antioxidant status (TPAS) in claudicants after exercise. Twenty claudicants, taking 75 mg of aspirin daily, were subjected to repeated treadmill testing (3 km/h, 10% inclination). Blood was sampled before and after exercise. Activated GpIIb/IIIa, PS and PMA were quantified with flow cytometry. TPAS was quantified using a decolourisation assay. Percent positive cells for PS (pre-exercise 3.76% vs. 40 min post-exercise 4.10%; P < 0.05) and platelet-monocyte aggregates (pre-exercise: 25.31% vs. 40 min post-exercise 26.99%; P < 0.05) were significantly higher after exercise. Relative median fluorescence (RMF) for activated GpIIb/IIIa was significantly higher 40 min after exercise (pre-exercise: 3.04 vs. 40 min post-exercise: 4.01; P < 0.05). TPAS was significantly higher post-exercise (pre-exercise: 1.31 mmol/l vs. 1 min post-exercise: 1.40 mmol/l and 40 min post-exercise: 1.38 mmol/l; P < 0.01). Following moderate exercise, 'aspirin treated claudicants' show marginal platelet activation, PMA formation and a favourable improvement in antioxidant status. Further studies are required to assess the effect of additional antiplatelet agents and the significance of platelet-monocyte interactions. The possibility that aspirin contributes to the TPAS changes following exercise needs to be investigated.