Sex differences in atherosclerosis and exercise effects

Abstract

i Cardiovascular disease (CVD) is the leading cause of death globally, with atherosclerosis being the main cause of cardiovascular diseases. Atherosclerosis is an inflammatory disease of the blood vessel wall, which over time will cause thickening and hardening of the vessel wall. Atherosclerosis can result in catastrophic vascular events, such as myocardial infarction and stroke. There are distinct sex differences in CVD mortality at different ages, before menopause women have a lower mortality of CVD in comparison to men, which equalises after menopause. In addition to sex differences in the incidence of CVD, there are also distinct sex differences in the phenotype of atherosclerotic plaques, with men generally developing more severe and vulnerable plaques that are at risk of rupture.This thesis aimed to investigate the sex differences in atherosclerosis, in particular how the proteome and pathophysiology differs. In addition, we sought to investigate the potential benefit of an exercise programme, in reducing CVD risks, using a randomised controlled trial including postmenopausal women.Sex differences in atherosclerosis were first investigated via proteomic analysis of human carotid endarterectomy samples. Initially, five intraplaque biopsies were taken from distinct atheroma regions, including; internal control, fatty streak, plaque shoulder, plaque centre, and fibrous cap. Protein extracts from these biopsies were subjected to analysis by mass spectrometry. The novel sampling method was successful in reducing the effect of plaque heterogeneity, a limitation in previous proteomic studies of atherosclerosis, and a number of previously unreported proteins were identified in human carotid atheroma. In addition to this, with the inclusion of multivariate statistical modelling, it was found that 43 proteins significantly discriminated the carotid atheroma between men and women. These proteins were grouped by function, and it was found that atheroma from men was associated with the increased abundance of inflammatory response proteins, including phospholipase-A2 membrane associated and lysozyme C, and atheroma from women was associated with increased abundance of blood coagulation, complement activation, and transport proteins, notably including; antithrombin-III, coagulation factor XII, and afamin. In addition, differences were also ii observed in the abundance of iron metabolism related proteins. These sex differences were further expanded upon from a pathophysiological perspective.Immunohistochemistry stainings of ferritin and transferrin receptor 1 were found significantly increased in the atheroma from men. Moreover, the levels of plasma haemoglobin were also significantly increased in men and were associated with the development of more vulnerable and severe plaque types. The more vulnerable and severe plaque types were also associated with significantly greater macrophage infiltration. In summary, these results are indicative of men developing atheroma with greater inflammation that are more vulnerable, due ...