Background: Low-dose aspirin is ineffective for primary prevention of cardiovascular events in people with body weight greater than 70kg. While the prevalent explanation for this is reduced platelet cyclooxygenase-1 (COX-1) inhibition at higher body weights, supporting data are limited, thereby demanding further investigation of the reason(s) underlying this observation. We propose that aspirin-mediated cyclooxygenase-2 (COX-2) acetylation and the resulting synthesis of 15-epi-lipoxin A4, a specialized pro-resolving mediator, is suboptimal in higher weight individuals, which may contribute to the clinical trial findings.
Methods: To test this hypothesis, we are conducting a double-blind, placebo-controlled, randomized, mechanistic crossover trial. Healthy men and women exhibiting a wide range of body weights take 81mg aspirin and 325mg aspirin for 3 weeks each, following 3-week placebo run-in and wash-out phases. Our target sample size is 90 subjects, with a minimum of 72 completing all visits estimated to be necessary to achieve power adequate to test our primary hypothesis.
Results: Our primary endpoint is the difference in change in plasma 15-epi-lipoxin A4 occurring with each dose of aspirin. Secondary endpoints include lipid mediator profiles, serum bioactive lipid profiles, and other endpoints involved in the resolution of vascular inflammation.
Conclusions: Study enrollment began in November 2021 and is ongoing. The results of this study will improve our understanding of the mechanisms underlying aspirin's role(s) in the prevention of adverse cardiovascular outcomes. They may also lead to additional studies with the potential to inform dosing strategies for patients based on body weight.
Keywords: Inflammation; aspirin; cardiovascular disease; obesity; pro-resolving mediators.