Cardiorespiratory Fitness Is Associated with Decreased Platelet Reactivity.

PURPOSE: Platelets are key mediators in cardiovascular disease (CVD). Low cardiorespiratory fitness (CRF) is a risk factor for CVD. The purpose of our study was to assess if CRF associates with platelet function. METHODS: Platelet assays and cardiopulmonary exercise testing were conducted in the Framingham Heart Study (n = 3,014). Linear mixed effects models estimated associations between CRF (assessed by peak oxygen uptake [VO2]), and multiple platelet reactivity assays. Models were adjusted for multiple medications, risk factors, relatedness and prevalent CVD. RESULTS: Nineteen associations passed the significance threshold in the fully adjusted models, all indicating higher CRF associated with decreased platelet reactivity. Significant traits spanned multiple platelet agonists. Strongest associations were observed in Multiplate whole blood testing after TRAP-6 (e.g., velocity, beta = -0.563, 95% CI [-0.735,-0.391], p = 1.38E-10), ADP (e.g., velocity, beta = -0.514, 95% CI [-0.681,-0348], p = 1.41E-09), collagen (e.g., velocity, beta = -0.387, 95% CI [-0.549,-0.224], p = 3.01E-06), ristocetin (e.g., AUC, beta = -0.365, 95% CI [-0.522,-0.208], p = 5.17E-06) and arachidonic acid stimulation of platelets (e.g., velocity, beta = -0.298, 95% CI [-0.435,-0.162], p = 3.39E-04), and light transmission aggregometry (LTA) after ristocetin stimulation (e.g., max aggregation, beta = -0.362, 95% CI [-0.540,-0.184], p = 6.64E-05). One trait passed significance threshold in the aspirin sub-sample (LTA ristocetin primary slope, beta = -0.733, 95% CI [-1.134,-0.333], p = 3.30E-04), and another in a model including von Willebrand Factor levels as a covariate (U46619, a thromboxane receptor mimetic, AUC in the Optimul assay, beta = -0.36, 95%CI [-0.551,-0.168], p = 2.35E-04). No strong interactions were observed between the associations and sex, age or body mass index in formal interaction analyses. CONCLUSIONS: Our findings build on past work that shows CRF to be associated with reduced CVD by suggesting decreased platelet reactivity may play a mechanistic role. We found significant associations with multiple platelet agonists, indicating higher CRF may globally inhibit platelets; however, given multiple strong associations after TRAP-6 and ADP stimulation, PAR-1 and purinergic signaling may be most heavily involved. This is notable since each of these receptor pathways are tied to anti-coagulant (DOACs/thrombin inhibitors) and anti-platelet therapies (P2Y12/PAR1/PAR4 inhibitors) for CVD prevention.

Factors that modulate platelet reactivity as measured by 5 assay platforms in 3429 individuals.

Background: Assessment of platelet function is key in diagnosing bleeding disorders and evaluating antiplatelet drug efficacy. However, there is a prevailing "one-size-fits-all" approach in the interpretation of measures of platelet reactivity, with arbitrary cutoffs often derived from healthy volunteer responses. Objectives: Our aim was to compare well-used platelet reactivity assays. Methods: Blood and platelet-rich plasma obtained from the Framingham Heart Study (N = 3429) were assayed using a range of agonists in 5 platelet assays: light transmission aggregometry, Optimul aggregometry, Multiplate impedance aggregometry (Roche Diagnostics), Total Thrombus-Formation Analysis System, and flow cytometry. Using linear mixed-effect models, we determined the contribution of preanalytical and technical factors that modulated platelet reactivity traits. Results: A strong intra-assay correlation of platelet traits was seen in all assays, particularly Multiplate velocity (r = 0.740; ristocetin vs arachidonic acid). In contrast, only moderate interassay correlations were observed (r = 0.375; adenosine diphosphate Optimul Emax vs light transmission aggregometry large area under the curve). As expected, antiplatelet drugs strongly reduced platelet responses, with aspirin use primarily targeting arachidonic acid-induced aggregation, and explained substantial variance (ß = -1.735; P = 4.59 × 10-780; variance proportion = 46.2%) and P2Y12 antagonists blocking adenosine diphosphate responses (ß = -1.612; P = 6.75 × 10-27; variance proportion = 2.1%). Notably, female sex and older age were associated with enhanced platelet reactivity. Fasting status and deviations from standard venipuncture practices did not alter platelet reactivity significantly. Finally, the agonist batch, phlebotomist, and assay technician (more so for assays that require additional sample manipulation) had a moderate to large effect on measured platelet reactivity. Conclusion: Caution must be exercised when extrapolating findings between assays, and the use of standard ranges must be medication-specific and sex-specific at a minimum. Researchers should also consider preanalytical and technical variables when designing experiments and interpreting platelet reactivity measures.

Trends among platelet function, arterial calcium, and vascular function measures.

Arterial tonometry and vascular calcification measures are useful in cardiovascular disease (CVD) risk assessment. Prior studies found associations between tonometry measures, arterial calcium, and CVD risk. Activated platelets release angiopoietin-1 and other factors, which may connect vascular structure and platelet function. We analyzed arterial tonometry, platelet function, aortic, thoracic and coronary calcium, and thoracic and abdominal aorta diameters measured in the Framingham Heart Study Gen3/NOS/OMNI-2 cohorts (n = 3,429, 53.7% women, mean age 54.4 years ±9.3). Platelet reactivity in whole blood or platelet-rich plasma was assessed using 5 assays and 7 agonists. We analyzed linear mixed effects models with platelet reactivity phenotypes as outcomes, adjusting for CVD risk factors and family structure. Higher arterial calcium trended with higher platelet reactivity, whereas larger aortic diameters trended with lower platelet reactivity. Characteristic impedance (Zc) and central pulse pressure positively trended with various platelet traits, while pulse wave velocity and Zc negatively trended with collagen, ADP, and epinephrine traits. All results did not pass a stringent multiple test correction threshold (p < 2.22e-04). The diameter trends were consistent with lower shear environments invoking less platelet reactivity. The vessel calcium trends were consistent with subclinical atherosclerosis and platelet activation being inter-related.

What is the context? Prior research has reported that measures of vascular system-influencing proteins such as angiopoietin-2, arterial calcium plaque formation, and arterial stiffness assessed by tonometry are associated with CVD risk.Since activated platelets produce and release vascular proteins like angiopoietin when activated, and microparticles that interact with endothelium, release of the foregoing mediators could provide one way in which vascular structure and platelet function influence each other.To our knowledge, no prior studies have directly investigated associations between these measures in a large sample. This investigation relates platelet function to arterial tonometry, aortic and arterial diameter, and arterial calcium measures in the Framingham Heart Study (FHS) Gen3/NOS/OMNI-2 cohorts (n = 3,429).What's new? Generally, higher arterial calcium measures trended with higher platelet reactivity, whereas larger aortic diameters trended with lower platelet reactivity.Arterial tonometry measures had positive and negative trends with platelet functions, including platelet measures with opposite relations to negative-inverse carotid-femoral pulse wave velocity (niCFPWV) and characteristic impedance (Zc). All tonometry, calcium, and diameter results did not reach a more stringent multiple testing threshold (p < 2.22e-04).What's the impact? The aortic diameter trends are consistent with lower shear stress invoking less platelet reactivity.The vessel calcium trends are consistent with increased vascular calcium buildup that could provoke platelet activation, thereby contributing to increased blood clot risk. Conversely, increased platelet activation could contribute to increased inflammation and thrombosis, leading to calcification in the arterial wall.

Alcohol intake including wine drinking is associated with decreased platelet reactivity in a large population sample.

BACKGROUND: Alcohol consumption is linked to decreased platelet function. Whether this link is dependent on sex or type of beverage remains unclear. METHODS: Cross-sectional data were obtained from the Framingham Heart Study (N = 3427). Alcohol consumption was assessed by using standardized medical history and Harvard semi-quantitative food frequency questionnaires. Five bioassays measured 120 platelet reactivity traits across agonists in whole-blood and platelet-rich plasma samples. Linear mixed-effects models adjusted for age, sex and aspirin use, hypertension, body mass index, cholesterol, high-density lipoprotein, triglycerides, smoking and diabetes evaluated associations between platelet reactivity and alcohol consumption. Beta effects, the regression coefficients that estimate the amount of change in each unit of the predictor variable whereas all other predictor variables remain fixed, for heavy alcohol consumption were compared with effects of aspirin use. RESULTS: Alcohol consumption was associated with decreased platelet reactivity, with more associations among wine and liquor compared with beer. Many platelet-alcohol associations in the full sample (86%, P < 0.01) had larger effect sizes in females. Lower light transmission aggregometry adenosine diphosphate (1.82 µM) maximum aggregation (P = 2.6E-3, 95% CI = -0.07, -0.02, ß = -0.042) and area under the curve (P = 7.7E-3, 95% CI = -0.07, -0.01, ß = -0.039) were associated with white wine consumption; however, red wine had no associations with platelet reactivity. The effect of aspirin use was on average 11.3 (±4.0) times greater than that of heavy drinking in our full sample. CONCLUSIONS: We confirm associations between alcohol consumption and decreased platelet reactivity. Effects appeared larger for liquor and wine intake and in our female cohort. Red wine consumption is not associated with lower platelet function, contrasting with prior population studies. Although we report an inhibitory relationship between alcohol intake and platelet function, these effects appear much smaller than that of aspirin use.

The association between platelet reactivity and lipoprotein levels in Framingham Heart Study participants.

BACKGROUND: Hypertriglyceridemia is an independent risk factor for major adverse cardiovascular events, though the mechanisms linking triglycerides and platelet function with thrombosis, remain elusive. The aim of this study was to assess the association between platelet function and triglyceride levels. METHODS: We included participants from the Framingham Heart Study Third Generation cohort, OMNI, and New Offspring Spouse cohort who attended the third examination cycle (2016-2019). Eligible participants were categorized into four triglyceride subgroups. RESULTS: The study comprised a total of 1897 (55.53 %) participants with normal TG levels; 883 (25.85 %) participants with high-normal TGs; 378 (11.07 %) with borderline high TGs; and 258 (7.55 %) participants with hypertriglyceridemia. After adjusting for age, sex, alcohol consumption, aspirin, statin and P2Y12 inhibitors, the levels of ADP-induced platelet aggregation were inversely associated with total cholesterol levels (P < 0.0001). Platelet disaggregation was associated with low-density lipoprotein and high-density lipoprotein cholesterol levels (P < 0.0001). Lastly, in a shear-stress chamber assay mimicking arterial flow velocities, TG levels in the normal-high group were associated with increased levels of collagen-dependent thrombogenicity (ß = 24.16, SE = 6.65, P < 0.0001). CONCLUSION: Triglyceride levels are associated with altered platelet activation and aggregation. Furthermore, increased platelet-driven thrombogenicity is directly associated with triglyceride levels after adjusting for medications and other covariates.

Serotonin-Affecting Antidepressant Use in Relation to Platelet Reactivity.

Depression is an independent risk factor of cardiovascular disease morbidity. Serotonin is a key neurotransmitter in depressive pathology, contained within platelets, and is a weak activator of platelets. Our study assessed the link between platelet reactivity traits, depression, and antidepressant (AD) use in a large population sample. Our study was conducted in the Framingham Heart Study (n = 3,140), and AD use (n = 563) and aspirin use (n = 681) were noted. Depression was measured using the Center for Epidemiological Studies-Depression (CES-D) survey. Platelet reactivity traits were measured across multiple agonists using five distinct assays. We utilized a linear mixed effects model to test associations between platelet traits and depression, adjusting for age, sex, aspirin use, and AD use. Similarly, we analyzed trait associations with any AD use, serotonin-affecting ADs, and norepinephrine-affecting ADs, respectively. There were strong associations with reduced platelet function and AD use, particularly with serotonin-affecting medications. This included lower Optimul epinephrine maximal aggregation (P = 4.87E-13), higher U46619 half maximal effective concentration (P = 9.09E-11), lower light transmission aggregometry (LTA) adenosine diphosphate (ADP) final aggregation (P = 1.03E-05), and higher LTA ADP disaggregation (P = 2.28E-05). We found similar associations with serotonin-affecting ADs in an aspirin-taking subset of our sample. There were no significant associations between platelet traits and depression. In the largest study yet of AD use and platelet function we show that antidepressants, particularly serotonin-affecting ADs, inhibit platelets. We did not find evidence that depressive symptomatology in the absence of medication is associated with altered platelet function. Our results are consistent with AD use leading to platelet serotonin depletions, decreased stability of platelet aggregates, and overall decreased aggregation to multiple agonists, which may be a mechanism by which ADs increase risk of bleeding and decrease risk of thrombosis.

Conserved motifs on the cytoplasmic face of the protein translocation channel are critical for the transition between resting and active conformations.

The Sec61 complex is the primary cotranslational protein translocation channel in yeast (Saccharomyces cerevisiae). The structural transition between the closed inactive conformation of the Sec61 complex and its open and active conformation is thought to be promoted by binding of the ribosome nascent-chain complex to the cytoplasmic surface of the Sec61 complex. Here, we have analyzed new yeast Sec61 mutants that selectively interfere with cotranslational translocation across the endoplasmic reticulum. We found that a single substitution at the junction between transmembrane segment TM7 and the L6/7 loop interferes with cotranslational translocation by uncoupling ribosome binding to the L6/7 loop from the separation of the lateral gate transmembrane spans. Substitutions replacing basic residues with acidic residues in the C-terminal tail of Sec61 had an unanticipated impact upon binding of ribosomes to the Sec61 complex. We found that similar charge-reversal mutations in the N-terminal tail and in cytoplasmic loop L2/3 did not alter ribosome binding but interfered with translocation channel gating. These findings indicated that these segments are important for the structural transition between the inactive and active conformations of the Sec61 complex. In summary our results have identified additional cytosolic segments of the Sec61 complex important for promoting the structural transition between the closed and open conformations of the complex. We conclude that positively charged residues in multiple cytosolic segments, as well as bulky hydrophobic residues in the L6/7-TM7 junction, are required for cotranslational translocation or integration of membrane proteins by the Sec61 complex.