PS-C28-6: HIGH TESTOSTERONE AND LOW ESTRADIOL SERA LEVELS ARE ASSOCIATED WITH UNSTABLE PLAQUE COMPOSITION IN MEN WITH SEVERE CAROTID ATHEROSCLEROSIS

Abstract

Background and Objectives: Ischemic strokes caused by the rupture of unstable atherosclerotic plaques in the carotid arteries, are leading causes of mortality and disability worldwide. Sex differences exist in plaque composition, where men are more likely to develop unstable plaques than women. Sex hormones affect vascular reactivity and inflammation, but it remains unclear if they are involved in plaque instability and how their role differs in men and women. Herein, we investigated the association between circulating endogenous sex hormone levels and plaque composition/instability in men and women with severe carotid atherosclerosis. Design and method: Pre-operative fasting blood samples and plaque specimens were collected from post-menopausal women and men greater than 55 years old with severe carotid atherosclerosis who underwent a carotid endarterectomy at McGill-affiliated hospitals in Montreal, Canada. Plaque composition and stability were examined by experienced vascular pathologists according to gold-standard histological classifications. Liquid chromatography-tandem mass spectrometry-based methods were developed to quantify endogenous sex hormones, 17ß-estradiol (E2), testosterone, androstenedione, and dehydroepiandrosterone, in sera samples. Results: Subjects (n = 460) had a mean age of 71.0 ± 9.0, were 68.9% male, and had various comorbidities (hypercholesterolemia [82.6%], hypertension [84.6%], type 2 diabetes [34.5%]). Clinical characteristics were similar among post-menopausal women (n = 143) and men (n = 317) with stable versus unstable plaques. Men had a significantly greater proportion of unstable versus stable plaques compared to women (men unstable: 61.5%, women unstable: 41.3%; P < 0.001), characterized predominantly by a large lipid-rich core, hemorrhage, and high presence of inflammatory cell infiltration. Men with unstable plaques had significantly higher levels of testosterone than men with stable plaques (P = 0.004). In men, testosterone levels were inversely associated with fibrosis (P < 0.05), while directly associated with unstable plaque features, including greater lipid core size (P < 0.05), and a greater presence of foam cells (P < 0.05), neovascularization (P < 0.01), and plaque (P < 0.01) and cap inflammation (P < 0.05). No associations were observed between testosterone levels and plaque features in women. Endogenous E2 levels were inversely associated with neovascularization (P < 0.05) and plaque and cap inflammation (P < 0.001) in men, while inversely associated with fibrosis levels in women (P < 0.05). Conclusion: Our findings suggest that higher testosterone and lower E2 levels are associated with unstable plaque composition in men with carotid atherosclerotic disease and may partly explain the higher proportion of unstable plaques observed among men than women of similar age and comorbidity status. Instead, in women, estradiol appears to play a detrimental role in plaque instability by inversely affecting fibrous tissue levels (a key stabilizing feature of plaques).