Effects of activity levels on aortic calcification in hyperlipidemic mice as measured by microPETmicroCT

Cardiovascular disease risk is associated with coronary artery calcification and is mitigated by regular exercise. Paradoxically, elite endurance athletes, who have low risk, are likely to have more coronary calcification, raising questions about the optimal level of activity.

Female hyperlipidemic (Apoe^-/-) mice with baseline aortic calcification were subjected to high-speed (18.5 m/min), low-speed (12.5 m/min), or no treadmill exercise for 9 weeks. ¹⁸F-NaF microPET/CT images were acquired at weeks 0 and 9, and echocardiography was performed at week 9.

In controls, aortic calcium content and density increased significantly. Exercise regimens did not alter the time-dependent increase in content, but the increase in mean density was blunted. Interestingly, the low-speed regimen significantly reduced ¹⁸F-NaF uptake, a marker of surface area. Left ventricular (LV) systolic function was lower while LV diameter was greater in the low-speed group compared with controls or the high-speed group. In the low-speed group, vertebral bone density by CT decreased significantly, contrary to expectations. Male hyperlipidemic (Apoe^-/-) mice were fed a Western diet and also subjected to low-speed or no exercise followed by imaging at weeks 0 and 9. In males, exercise also did not alter the time-dependent increase in aortic calcification. Exercise did not affect ¹⁸F-NaF uptake or bone mineral density, but it blunted the diet-induced LV hypertrophy seen in controls.

These results suggest that, in mice, exercise has differential effects on aortic calcification, cardiac function, and skeletal bone mineral density.