Zhongguo quanke yixue (Nov 2022)
Effects of High-intensity Interval Training on Cardiac Structure and Function in a Rat Model of Myocardial Infarction
Abstract
Background As one exercise program of cardiac rehabilitation, the role of high-intensity interval training (HIIT) in improving myocardial infarction is still controversial, and the mechanism is unclear. Objective To investigate the effect of HIIT on improving the cardiac structure and function in a rat model of myocardial infarction. Methods An experiment was conducted from September 2020 to October 2021. From a random sample of 78 3-month-old male SD rats, 56 were eventually included, and 14 of them were randomly selected as sham-surgery group (Sham group) , and the remaining 42 rats were equally randomized into MI-sedentary group (MI-SED group) , MI-HIIT group (MI-HIIT group) , and MI-medium-intensity continuous training (MI-MICT group) after being used for preparing a model of acute myocardial infarction (AMI) . Sham group and MI-SED group were not trained, MI-HIIT group received high-intensity and medium-intensity training alternately, MI-MICT group received medium-intensity continuous training. After 1 week of AMI modeling, MI-HIIT and MI-MICT groups received 8 weeks of training. At the end of 4 weeks of training, 7 rats in each of the 4 groups were randomly selected for detecting cardiac ultrasound, and weighing body weight, then were sacrificed, and their heart weight and serum tumor necrosis factor (TNF-α) were measured, cardiac mass index was calculated, and heart tissues were measured using H&E staining, Masson's Trichrome staining and immunohistochemical staining. At the end of 8 weeks of training, the same operation was performed on the remaining 7 rats in each of the groups. Results After 4 weeks of training, the standardized cardiac mass index of MI-HIIT group was higher than that of each of the other three groups (P<0.05) . The sham group had higher ejection fraction (EF) , fractional shortening (FS) and left ventricular end-systolic posterior wall thickness (LVPWs) than MI-HIIT and MI-MICT groups (P<0.05) . MI-SED group had lower EF, FS, and LVPWs, and higher left ventricular end-systolic diameter (LVESD) than MI-HIIT and MI-MICT groups (P<0.05) . After 8 weeks of training, MI-HIIT group had lower body weight than sham and MI-SED groups, higher heart weight than sham, MI-SED and MI-MICT groups, and higher standardized cardiac mass index than sham and MI-MICT groups (P<0.05) . MI-HIIT group demonstrated higher EF, LVESD, left ventricular end-diastolic diameter (LVEDD) , left ventricular end-systolic anterior wall thickness (LVAWs) than sham and MI-SED groups (P<0.05) . Moreover, MI-HIIT group also showed higher FS and LVPWs than MI-SED group (P<0.05) . HE staining results showed that MI-HIIT group had significantly improved inflammatory changes of heart tissue and more closely arranged myocardial cells at the end of the 8th week of training compared with at the end of 4 weeks of training. Masson's Trichrome staining results showed that after 8 weeks of training, the proportion of myocardial fibrillar collagen in myocardial tissues of MI-SED group was higher than that of MI-HIIT and MI-MICT groups. Immunohistochemical results showed that MI-HIIT group had more newly formed blood vessels in cardiac tissues than sham and MI-SED groups after 4 and 8 weeks of training, so did the MI-MICT group. The number of newly formed blood vessels in cardiac tissues of MI-HIIT group was more than that in MI-MICT group after 8 weeks of training. MI-HIIT group had higher serum TNF-α than MI-SED group after 4 weeks of training. After 8 weeks of training, the serum TNF-α in MI-HIIT group was higher than that in MI-MICT group. Conclusion HIIT performed in the early stage of AMI could improve cardiac mass index, induce early inflammatory response in myocardial tissue, reduce myocardial fibrosis, promote angiogenesis and ventricular remodeling. HIIT had better overall effect than MICT.
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