The effect of exercise on cardiometabolic health, atherosclerosis and cardiac remodelling

Abstract

Exercise reduces cardiovascular risk and results in physiological remodelling of the heart, to meet the increased demands of the exercising muscles. However, the mechanism of risk reduction and the nature of cardiac remodelling are not currently well defined. The aim of this thesis was to gain insights into the mechanisms behind the effect of exercise on cardiometabolic health, atherosclerosis and cardiac remodelling.

A prospective study into the effects of exercise on cardiometabolic health was conducted in young male army recruits. We described for the first time that moderate and high intensity exercise is associated with enhanced high density lipoprotein function as well as a less atherogenic lipoprotein profile.

We also prospectively assessed the effect of moderate and high intensity exercise on cardiac remodelling in these subjects, using echocardiography. We found that exercise training was associated with a “dose dependent” increase in cardiac chamber size. We provide a novel description of the “Soldier’s heart”,

where soldiers could be considered “occupational athletes” with cardiac dimensions exceeding “normal” reference ranges, but with normal systolic function and myocardial strain.

We also assessed exercise induced cardiac remodelling (EICR) in elite road cyclists and soccer players using cardiac magnetic resonance imaging. Contrary to our hypothesis; that different sport dependent loads would results in differential cardiac remodeling; fitness level rather than sport type was more strongly correlated with EICR. A unique finding was of relative lateral wall hypertrophy in athletes with reduced regional radial and circumferential strain.

To complement our human studies, we assessed exercise in an early and late-stage mouse model of atherosclerosis to determine the effects of exercise on plaque size and composition at different stages of atheroma plaque development. Exercise resulted in a less atherogenic lipid profile, with less plaque stenosis in both early and late stage disease. The effect was more pronounced in early stage disease, suggesting that early intervention with exercise is likely important.

This body of work provides important insights into our understanding of the effects of exercise on cardiometabolic health, atherosclerosis and cardiac remodelling.