Effects of exercise of different intensities on the angiogenesis, infarct healing, and function of the left ventricle in postmyocardial infarction rats

Abstract

Lifestyle interventions, including physical exercise, are feasible options for the prevention and treatment of cardiovascular diseases. In this study, the effects of exercise of different intensities on the infarct region, function, and angiogenesis of the left ventricle (LV) in postmyocardial infarction (MI) rats were investigated and the levels of vascular endothelial growth factor (VEGF) proteins in the LV and plasma were examined. Male Sprague-Dawley rats were randomly assigned to six groups. The exercise-trained rats observed a daily 60-min treadmill routine 5 days/weeks for 6 weeks. Different treadmill speeds were used in the high-intensity exercise (HIE), moderate-intensity exercise (MIE), and low-intensity exercise (LIE) groups, whereas the untrained rats remained sedentary (Sed). At 6 weeks, all rats underwent either an acute MI operation or a sham (Sh) MI operation 24 h after their last treadmill exercise or the corresponding Sed protocol. They were then killed 7 days after recovery. Echocardiographic and hemodynamic measurements were taken at the end of the experimental protocol. The infarct regions were analyzed using Masson's trichrome staining, whereas intramyocardial microvessels were detected using Factor VIII-related antigen staining. The cardiac VEGF protein levels were determined by western blotting analysis, and plasma VEGF concentrations were examined by enzyme-linked immunosorbent assay. Compared with the corresponding parameters in the Sed-Sh group, LV function did not significantly ameliorate and microvessel density did not increase in the MIE-Sh group. Compared with the Sed-MI group, the MIE-MI and HIE-MI groups had significantly reduced LV infarct size, improved hemodynamic parameters, and increased fractional shortening, scar thickness, and microvessel density, these parameters did not significantly change in the LIE-MI group. In addition, the MIE-MI and HIE-MI rats had significant differences in hemodynamic parameters and microvessel density. Compared with those of the Sed-MI group, the heart and plasma of the exercise-trained rats in the MIE-MI and HIE-MI groups displayed higher levels of VEGF protein, but the difference between the MIE-MI and HIE-MI groups was not significant. Moderate-intensity running before acute MI improved LV function, reduced scar size, and increased scar thickness and microvessel density in post-MI rats. Exercise at a higher intensity could have further small effects. LIE may be beneficial, but it would not be sufficient to improve MI. Moderate-intensity and high-intensity running upregulated the expression of VEGF protein and increased microvessels, which may have partly improved cardiac function after MI in this study.