The Physiological Adaptation Of Mitochondrial Fusion And Fission To Aging And Endurance Training In Rat Muscle

Objective: Mitochondria play a central role in energy metabolism and others cellular functions, mitochondrial morphology is diverse and dynamic, the Fission/fusion dynamics balance can be seasoned with the cell's energy demand. Several evidences have demonstrated that proteins participating in the generation of the mitochondrial network may be involved in the control of mitochondrial energy metabolism. The purpose of this study was to investigate the changes of Mfn and Fis1 and Drp1 both during the rats aging and after endurance training, and its mechanism or what role it plays in muscular mitochondrial energy metabolism in response to a long-term endurance training so as to offer theory support and experiment foundation for the positive effects of endurance training in counteracting the aging. .Methods: Forty-eight male SD rats were divided into six groups: five month age control group(5MC), five month age trained group(5MT), fifteen month age control group(15MC), fifteen month age trained group(15MT), twenty month age control group(20MC) and twenty month age trained group(20MT). Moderate endurance exercise (64%VO2max) was imposed on the groups of rats aged 2 month, 12 month and 17 month as trained in a treadmill (5°, 15m/min, 60 min, once per day for 5 days) for 12 wk, respectively. Throughout this experiment, control rats remained sedentary in their cages. After 12 weeks, 24 hours after trained, the rats were anesthetized, then detected the body composition, and the skeletal muscle (typeⅠand typeⅡ) was rapidly excised to test the parameters in mitochondrial morphology, respiration function and free radical metabolism, mitochondrial protein and mRNA which taking part in mitofusin and mitofision including Mfn1,Mfn2,Fis1 and Drp1. Results: 1. Body mass and body fat percentage of rats increased during the aging progress. Body fat percentage of rats markedly decreased after endurance training. 2. Aging-associated increase in mitochondrial biogenesis was found in rat skeletal muscle, endurance training can induce increase in number density of subsarcolemmal (SS) mitochondria and in volume density of intermyofibrillar (IMF) mitochondria in all groups. 3. Mitochondrial respiratory function decreased during the aging progress, endurance training can diminish the decline of respiratory function of mitochondria in skeletal muscle, irrespective of age. 4. ROS from mitochondrial increased during the aging of rats. Endurance training can improve the redox state in mitochondria. 5. The expression of Mfn1 and Mfn2 and those proteins decreased during the aging process, yet those increased after a long-term endurance training. 6. The expression of Drp1 and Fis1 and those proteins increased not only during the aging process but also after a long-term endurance training.Conclusion: 1.The dynamics balance between Fission and fusion incline to induce fragmented mitochondria during the aging process; 2. The level of the dynamics balance between Fission and fusion is higher than untrained mice after a long-term endurance training. 3. We hypothesized that mitochondrial ROS production might contribute to induce the expression of mitochondrial fission/fusion gene both during the rats aging and after endurance training. 4. Endurance training is not only responsible for providing signals that effect mitochondrial biogenesis, but also for promoting the dynamics balance of mitochondrial fusion and fission.