Abstract 13538: Associations Between Circulating Liver Enzymes and Platelet Reactivity

Abstract

Introduction: The liver plays an essential role in thrombopoiesis and coagulation, and circulating liver enzymes are associated with altered platelet counts. However, the role of liver enzymes in the modulation of platelet reactivity remains unclear. Methods: A total of 3,429 Framingham Heart Study participants were included in this study. Platelet reactivity to 8 agonists, including adenosine diphosphate (ADP), thromboxane A 2 mimetic (U46619) and arachidonic acid (AA), was measured using light transmission aggregometry (LTA), Multiplate impedance aggregometry and Optimul aggregometry. Platelet counts and platelet-red blood cell aggregates were enumerated using flow cytometry. Levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were also measured. Associations of platelet reactivity phenotypes with liver circulating liver enzyme levels analyzed using linear mixed-effects models and adjusted for sex, age, relatedness, smoking, aspirin-, and statin-use. To correct for multiple testing, a Bonferroni-correction threshold of P<0.0011 was used to account for multiple comparisons. Results: Higher ALT levels were associated with platelet disaggregation in LTA to ADP (β=0.056, SE=0.02, P=3.54E-04), and with decreased platelet reactivity in response to U46619 in Optimul (EC 50 : β=0.064, SE=0.019, P=7.65E-04). Interestingly, higher AST levels were associated with decreased platelet counts (β=-0.082, SE=0.019, P=1.04E-05), platelet reactivity to U46619 (β=-0.069, SE=0.018, P=1.04E-04) and AA (β=-0.047, SE=0.013, P=3.12E-04), and circulating platelet-red blood cell aggregates (β=-0.062, SE=0.018, P=9.54E-04). Conclusion: Our findings suggest that ALT levels could alter primary platelet aggregation. AST may indirectly modulate platelet counts. In addition, lower AST levels may contribute to platelet hyperresponsiveness. Lastly, ALT and AST levels may have antagonistic effects on the formation of platelet and red blood cell aggregates, which may indirectly influence platelet margination within vessels. Additional studies are underway to examine whether liver fat, a marker of fibrosis associated with cardiovascular disease, is also associated with altered platelet function.