Background and Objective: Cardiac mitochondrial dysfunction is well recognized in ischemic heart disease, and mitochondria appear to play an important role in the exercise-induced cardioprotective effects observed after myocardial infarction. Brief, intermittent periods of blood-flow occlusion protect the heart from injury; however, the underlying mechanism remains unclear. This study aimed to determine the effects of intermittent leg blood-flow occlusion and aerobic exercise on cardiac mitochondrial dynamics in a rat model of myocardial infarction.
Methods: This experimental study included 25 male Wistar rats aged 8-10 weeks and was conducted at the Histogenotech Laboratory Animal Breeding and Maintenance Center in Tehran. The animals were divided into five groups of five: healthy control, myocardial infarction, myocardial infarction plus occlusion, myocardial infarction plus exercise, and myocardial infarction plus exercise and occlusion. Myocardial infarction was induced by two intraperitoneal doses of isoproterenol (100 mg/kg.day). Intermittent leg blood-flow occlusion comprised three cycles of 5-minute occlusion followed by 5-minute reperfusion. Aerobic exercise was performed five days per week for six weeks. MFN1 and Drp1 gene expression was measured using real-time PCR.
Results: Compared with the healthy group, myocardial infarction was associated with decreased cardiac MFN1 expression (0.120±0.013 vs 1.003±0.095) and increased Drp1 expression (4.937±0.209 vs 1.011±0.184) (P<0.05). Compared with the myocardial infarction group, MFN1 increased and Drp1 decreased significantly in the occlusion (MFN1=0.298±0.028; Drp1=3.99±0.136), exercise (MFN1=0.409±0.010; Drp1=3.57±0.432), and exercise-plus-occlusion groups (MFN1=0.659±0.027; Drp1=1.765±0.022; P<0.05).
Conclusion: Aerobic exercise and intermittent leg blood-flow occlusion improve cardiac mitochondrial dynamics by regulating mitochondrial fission and fusion in male rats with myocardial infarction. Combining aerobic exercise with intermittent blood-flow occlusion produces a greater effect.