The Role Of Mitochondria In Aging And Postponed Aging By Aerobic Exercise

In order to understand the role of mitochondria in aging, we have determined the alternation of mitochondrial lipid peroxidation, antioxidant defense capacity, complex activity and genome in liver, heart and skeletal muscle from 2 month-old rats and 22 month-old rats(n = 8, respectively). Taking swimming training as aerobic exercise model, we have also determined the effect of exercise on mitochondria of different tissues from endurance-trained 22 month-old rats(n = 8, trained for 3 months) in order to understand the role of mitochondria in postponed aging by aerobic exercise.The results showed:1. The level of lipid peroxidation of mitochondria in skeletal muscle form aged rats was higher significantly than from young rats. In aged liver, the level of lipid peroxidation increased without significance. No changes was observed in aged heart. The antioxidant defense capacities of mitochondria increased significantly in aged liver and skeletal muscle and no changes were observed in aged heart. The level of lipid peroxidation of mitochondria decreased significantly in liver and skeletal muscle but not in heart from aerobic exercise-trained aged rats than from aged rats. All three tissues from endurence-trained rats had more powerful antioxidant defense capacity than from aged rats.2. The activities of complex I and IV decreased significantly in aged liver from aged rats than in young rats. The activities of complex II decreased without significance in aged liver. No changes of the activities of complex II were observed in aged liver. The activities of complex I decreased significantly in heart from aged rats than in young rats. The activities of complex II and III decreased and IV increased without significance in aged heart. The activities of complex I, II and IV decreased significantly in aged skeletal muscle and no changes in complex III. The activities of complex I, II and IV increased significantly and activities of III increased without significance in aged aerobic exercise-trained liver and skeletal muscle. The activities of complex I and IV increased significantly and activities of II and III increased without significant in aged aerobic exercise-trained heart.3. The mitochondrial DNA deletions were detected in five aged liver from eight and in two aerobic exercise-trained aging liver from eight. The estimate of the average proportion of deleted moleculars in the liver showed they represented 0.0012% and 0.00047% respectively from aged and exercise-trained aging rats. The mitochondrial DNA deletions were detected only in one aged liver from eight aging rat and it represented 0.0075% expressed as proportion of deleted moleculars. No mitochondrial deletions were detected in heart and other samples.The results suggest that there is impairment of mitochondrial function accompaniedwith increase of lipid peroxidation and antioxidation defense capacity adaptation in skeletal muscle and liver of aged rats. Oxidative damage and mitochondrial mutation are important factors result to aging.Aerobic exercise improves the antioxidation defense capacity in exercise old rats. It also reduces the mitochondrial lipid peroxidation in skeletal muscle and liver of exercise aged rats. Subsequently the function of mitochondria is ameliorated and the frequency of mitochondrial DNA mutation is decreased. All these factors represent a positive circle which contributes to postponed aging.It's noticeable that there are differences in sensitivity of mitochondrial damage by reactive oxygen species, the decrease extent of mitochondrial function and the proportion of mitochondrial DNA deletion. There are least aged-associated alteration in heart mitochondria in three tissues of rats.