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 improves electrocardiographic signs of myocardial ischemic/hypoxic injury and malignant arrhythmias occurring after exhaustive exercise in rats.

Exercise preconditioning (EP) has a good myocardial protective effect. This study explored whether EP improves electrocardiographic (ECG) signs of myocardial ischemic/hypoxic injury and the occurrence of malignant arrhythmia after exhaustive exercise. A total of 120 male SD rats were randomly divided into the control group (group C), early exercise preconditioning group (group EEP), late exercise preconditioning group (group LEP), exhaustive exercise group (group EE), early exercise preconditioning + exhaustive exercise group (group EEP + EE) and late exercise preconditioning + exhaustive exercise group (group LEP + EE). Changes in heart rate (HR), ST segment, T wave and QT corrected (QTc) intervals on ECG; hematoxylin-basic fuchsin-picric acid (HBFP) staining; and cTnI levels were used to study myocardial injury and the protective effect of EP. Compared with those in group C, the levels of plasma markers of myocardial injury, HBFP staining and ECG in group EE were significantly increased (P < 0.05). Compared with those in group EE, the levels of plasma markers of myocardial injury, HBFP staining and ECG in group EEP + EE and group LEP + EE were significantly decreased (P < 0.05). The results suggested that EP improved ECG signs of myocardial ischemic/hypoxic injury and malignant arrhythmias that occur after exhaustive exercise. The ST segment and T wave could also serve as indexes for evaluating exhaustive exercise-induced myocardial ischemia/hypoxia.

[Effects of long-term moderate-small intensity aerobic exercise on differential expression of proteome in left ventricular muscle of rats].

Objective: To investigate the effects of long-term moderate-small intensity aerobic exercise on the differential expression of proteome in left ventricular muscle of rats, and to screen the target proteins sensitive to moderate-small intensity aerobic exercise stimulation. This study will enrich the basic theory of exercise and fitness and provide new ideas and experimental basis for the rehabilitation treatment of chronic cardiovascular disease. Methods: Twenty male SD rats were randomly divided into exercise group and control group (n=10). The treadmill training model of long-term moderate-small intensity aerobic exercise was established, and the whole protein samples of left ventricular muscle were extracted and separated by two-dimensional gel electrophoresis (2-DE). The two-dimensional gel electrophoresis map was analyzed by Bio PD quest image analysis software. The protein spots with differential expression more than 5 times or down-regulated over 80% after exercise were identified by tandem time-of-flight mass spectrometry (ULGRAFL-FLEX-TOF/TOF). Results: Compared with the group C, the heart weight index of the group E was increased by 32.0%, and the difference was significant (P＜0.05). Compared with the group C, there were 71 protein spots expression were up-regulated≥2 times or down-regulated≥50% in the group E. 4 protein spots expression were up-regulated≥5 times or down-regulated≥80% were identified by mass spectrometry, 3 proteins and 1 unknown protein were identified. Conclusion: After long-term moderate-small intensity aerobic exercise, the rats heart had a good adaptive change, and the proteome of left ventricular muscle changed significantly. Long-term moderate-small intensity aerobic exercise can effective enhance the ability of myocardial antioxidation.

Exercise Preconditioning Increases Beclin1 and Induces Autophagy to Promote Early Myocardial Protection via Intermittent Myocardial Ischemia-Hypoxia.

Exercise preconditioning (EP) provides protective effects for acute cardiovascular stress; however, its mechanisms need to be further investigated. Autophagy is a degradation pathway essential for myocardium health. Therefore, we investigated whether intermittent myocardial ischemia-hypoxia affected Beclin1 and whether the changes in autophagy levels contribute to EP-induced early myocardial protective effects. Rats were trained on a treadmill using an EP model (four cycles of 10 minutes of running/10 minutes of rest). Exhaustive exercise (EE) was performed to induce myocardial injury. Cardiac troponin I (cTnI) and ischemia-hypoxia staining were used to evaluate myocardial injury and protection. Double-labeled immunofluorescence staining and western blot analysis were employed to examine related markers. EP attenuated the myocardial ischemic-hypoxic injury induced by EE. Compared with the control (C) group, the dissociations of Beclin1/Bcl-2 ratio and Beclin1 expression were both higher in all other groups. Compared with the C group, PI3KC3 and the LC3-II/LC3-I ratio were higher in all other groups, whereas LC3-II was higher in the EE and EEP + EE groups. p62 was higher in the EE group than in the C group but lower in the EEP + EE group than in the EE group. We concluded that EP increases Beclin1 via intermittent myocardial ischemia-hypoxia and induces autophagy, which exerts early myocardial protective effects and reduces the myocardial ischemic-hypoxic injury induced by exhaustive exercise.

Comparison of myocardial ischemic/hypoxic staining techniques for evaluating the alleviation of exhaustive exercise-induced myocardial injury by exercise preconditioning.

Exercise preconditioning (EP) can alleviate myocardial ischemic/hypoxic injury by inducing endogenous cardioprotection. Hematoxylin-eosin (HE), hematoxylin-basic fuchsin-picric acid (HBFP), and chromotrope-2R brilliant green (C-2R BG) staining have been used to visualize myocardial ischemic/hypoxic changes in previous EP studies, but comprehensive evaluation and comparisons of these methods are lacking. This study evaluated ischemic/hypoxic changes in adjacent myocardial sections by HE, HBFP, and C-2R BG and compared the characteristics of sections stained by these three methods to show changes associated with exercise-induced myocardial ischemic/hypoxic injury. Rats were randomly divided into four groups: control (C), exercise preconditioning (EP), exhaustive exercise (EE), and exercise preconditioning + exhaustive exercise (EP + EE). Adjacent myocardial sections were stained as described above and compared to evaluate the effects of exercise-induced myocardial ischemic/hypoxic injury. The three staining methods revealed consistent localization patterns of myocardial ischemic/hypoxic injury in all groups. Results suggest that EP can alleviate exhaustive exercise-induced myocardial ischemic/hypoxic injury, and the three staining methods are suitable for the histological study of exercise-induced myocardial ischemic/hypoxic injury and protection. HE staining is a simple procedure but is not specific for myocardial ischemic/hypoxic injury. HBFP and C-2R BG staining can be used to specifically visualize myocardial ischemic/hypoxic injury.

[Study on 4 weeks medium intensity aeraobic exercise induce the difference expression of the proteomics in rat atrial muscle].

OBJECTIVE: To investigate the effect of moderate-intensity aerobic exercise on the differential expression of rat atrial muscle Proteomics and genes, which provide research basis for the rehabilitation of chronic cardiovascular diseases and exercise -induced cardiac remodeling research. METHODS: Twenty male SD rats were randomly divided into control group and experimental group (n=10) according to body weight. Rats in the experimental group were trained (6 days per week),which lasted for 4 weeks of moderate-intensity aerobic exercise at a rate of 24 m·min-1 for 40 min (load intensity equivalent to 60%~70% VO2max). The proteins were separated by two dimensional gel electrophoresis, and the tandem time-of- flight mass spectrometer technique was used to identify 13 candidate target protein spots. The expression levels of these 13 protein spots were up-regulated more than 5 times or down -regulated to below 1/5. The mRNA of six target proteins were detected by reverse transcription-polymerase chain reaction (RT-PCR). RESULTS: By software analysis, the experimental group compared with the control group, there were 8 protein points which their expression reduced more than 4/5 and 5 protein points up-regulated more than 5 times, 13 proteins were identified by mass spectrometry protein spots, the final identification results acquired 8 proteins and a unknown protein of molecular mass 54 KDa, such as:pyruvate dehydrogenase E1α1, mitochondrial aconitate hydratase, protein disulfide isomerase A3, methylmalonic acid semialdehyde dehydrogenase, mitochondrial dihydrolipoic acid dehydrogenase, isovaleryl coenzyme A dehydrogenase, glutathione synthetase, mitogen-activated protein kinase 3 and so on. Compared with the control group, the mRNA expression of methylmalonic acid semialdehyde dehydrogenase in the atrial muscle of rats was decreased after 4 weeks of moderate aerobic exercise (P<0.05), the mRNA expression levels of mitochondria Ⅱ lipoic acid dehydrogenase, protein disulfide isomerase A3, mitochondrial aconitate hydratase and glutathione synthetase were decreased (P>0.05); The mRNA expression level of isopentenyl-CoA dehydrogenase was increased (P>0.05). The results indicated that the mRNA expression level was not completely consistent with the changes in mass spectrometry identification results. CONCLUSIONS: The 4 weeks moderate-intensity aerobic exercise induced ignificant changes of rats atrial muscle protemics. The majority of the 13 identified target proteins in this experiment are energy metabolism enzymes. The majority of the expression of the target protein and the mRNA expression in the atrial muscle is inconsistent and different. Exercise may affect the regulation of gene transcription or downstream translation and modification of these target proteins, resulting in the change of differential expression.