The effects of different exercise training protocols on mitochondrial dynamics in skeletal and cardiac muscles of Wistar rats

Background Mitochondrial fission and fusion both contribute to maintaining mitochondrial function and optimizing bioenergetic capacity. Objective The aim of this study was to compare the effect of aerobic and resistance training on mitochondrial fission and fusion markers in skeletal and cardiac muscles of Wistar rats. Method 24 male Wistar rats were randomly divided into four groups of moderate-intensity interval training (MIIT), high-intensity interval training (HIIT), resistance training (RT) and control (CON). The MIIT and HIIT groups performed treadmill exercises with an intensity of 60-65% and 80-85% of the maximum speed, respectively, while the RT group performed resistance training with an intensity of 30-60% of the rat's body weight for 8 weeks. The soleus (SOL), extensor digitorum longus (EDL) and left ventricular tissues were used to evaluate markers of mitochondrial fission and fusion PGC-1 alpha (fusion/fission), Opa-1 (fusion), Fis-1 (fission), Drp-1 (fission), Mfn-1 and Mfn-2 (fusion) genes expression. Results In all three tissues, a significant increase in some mitochondrial fusion markers was observed after 8 weeks of training (p = < 0.0001-0.0452). Furthermore, a significant decrease in cardiac mitochondrial fission markers was observed in all three groups (p = < 0.0001-0.0156). This reduction in some markers was evident in the SOL tissue of the HIIT group (p < 0.0001 for Drp-1 and p = 0.0007 for Fis-1) and in the EDL tissue of the RT group (p = 0.0005 for Fis-1 and p = 0.0012 for Drp-1). The mitochondrial fission/fusion markers in the heart (p = 0.0007-0.0449) and SOL (p = 0.0050-0.0258) tissues of the HIIT group had more changes than the RT group, while the mitochondrial fission markers in the EDL tissue of the RT group had a lower level than the HIIT (p = 0.0087 for Drp-1) and MIIT (p = 0.0130 for Fis-1 and p = 0.0010 for Drp-1) groups. Conclusion Our study demonstrated that HIIT, through better regulation of mitochondrial fusion and fission than RT, improves mitochondrial dynamics in cardiac and SOL tissues.