Exercise preconditioning promotes myocardial GLUT4 translocation and induces autophagy to alleviate exhaustive exercise-induced myocardial injury in rats.

Exercise preconditioning (EP) is a line of scientific inquiry into the short-term biochemical mediators of cardioprotection in the heart. This study examined the involvement of autophagy induced by energy metabolism in myocardial remodelling by EP and myocardial protection. A total of 120 healthy male Sprague Dawley (SD) rats were randomly divided into six groups. Plasma cTnI, HBFP staining and electrocardiographic indicators were examined in the context of myocardial ischemic/hypoxic injury and protection. Western blotting and fluorescence double labelling were used to investigate the relationship between energy metabolism and autophagy in EP-resistant myocardial injury caused by exhaustive exercise. Compared with those in the C group, the levels of myocardial ischemic/hypoxic injury were significantly increased in the EE group. Compared with those in the EE group, the levels of myocardial ischemic/hypoxic injury were significantly decreased in the EEP + EE and LEP + EE groups. Compared with that in the EE group, the level of GLUT4 in the sarcolemma was significantly increased, and the colocalization of GLUT4 with the sarcolemma was significantly increased in the EEP + EE and LEP + EE groups (P < 0.05). LC3-II and LC3-II/LC3-I levels of the EEP + EE group were significantly elevated compared with those in the EE group (P < 0.05). The levels of p62 were significantly decreased in the EEP + EE and LEP + EE groups compared with the EE group (P < 0.05). EP promotes GLUT4 translocation and induced autophagy to alleviate exhaustive exercise-induced myocardial ischemic/hypoxic injury.

Exercise Preconditioning Promotes Autophagy to Cooperate for Cardioprotection by Increasing LC3 Lipidation-Associated Proteins.

The cardioprotection of exercise preconditioning (EP) has been well documented. EP can be divided into two phases that are the induction of exercise preconditioning (IEP) and the protection of exercise preconditioning (PEP). PEP is characterized by biphasic protection, including early exercise preconditioning (EEP) and late exercise preconditioning (LEP). LC3 lipidation-mediated autophagy plays a pivotal role in cardioprotection. This study aimed to investigate the alterations of LC3 lipidation-associated proteins during EP-induced cardioprotection against myocardial injury induced by exhaustive exercise (EE) was used in a rat model of EP. These rats were subjected to an intermittent exercise consisting of four periods, with each period including 10 min of running at 30 m/min and 0% grade (approximately 75% VO2max) followed by 10 min of intermittent rest. A model of EE-induced myocardial injury was developed by subjecting rats to a consecutive running (30 m/min, 0% grade) till exhaustion. Following EEP, the colocalization of LC3 with Atg7 was significantly increased, and LC3-I, LC3-II, LC3-II/LC3-I, Atg7, Atg4B, and Atg3 levels were significantly increased. Atg7, Atg4B, and Atg3 mRNAs were all significantly upregulated, and LC3 mRNAs tended to be higher. Following LEP, Atg4B, and Atg3 levels were significantly increased. Atg7, Atg4B, and Atg3 mRNAs were all significantly upregulated, and LC3 mRNAs tended to be higher. A group of rats were subjected to EEP followed by EE, and the co-localization of LC3 with Atg7 was significantly increased, while LC3-I, LC3-II, LC3-II/LC3-I, Atg7, Atg4B, and Atg3 levels were also significantly increased. Moreover, there was a significant increase in the co-localization of LC3 with Atg7, LC3-I, LC3-II, Atg7, and Atg4B levels during LEP followed by EE. The formation of autophagosome during LEP followed by EE may have been weaker than that during EEP followed by EE due to the lower lipidation of LC3. EP may promote autophagy to maintain cell homeostasis and survival, which cooperates for cardioprotection of alleviating exhaustive exercise-induced myocardial injury by increasing LC3 lipidation-associated proteins. There is a difference between EEP and LEP in terms of the mechanisms of cardioprotection afforded by these respective conditions. The positive regulation of transcription and translation level of LC3 lipidation-associated proteins may all be involved in the mechanism of EEP and LEP, while compared with LEP, the regulation of translation level of EEP is more positively to promote autophagy.