Effect of endurance training on accumulation of age-associated mitochondrial DNA deletions in old rats.

有人提出，肌肉能量产物代谢的年龄相关性下降是由于线粒体DNA(MtDNA)缺失在几个物种中积累造成的(Linnane等人，1989)。然而，尚未在大鼠骨骼肌中成功检测到与年龄相关的mt DNA缺失(Filser等人，1997年)。众所周知，运动可以改善肌肉新陈代谢，然后可能有助于防止随着年龄的增长而积累mtDNA缺失。就我们所知，到目前为止，人们对运动对mtDNA缺失积累的影响知之甚少。本研究的目的是检测大鼠骨骼肌中与年龄相关的mtDNA缺失，并检测耐力训练是否影响不同类型骨骼肌中mtDNA缺失随年龄的增加。本研究选用Wistar雄性大鼠45只(10周29只，90周16只)。将幼年大鼠分为3组(20m/m in训练组、30m/m in训练…组老年大鼠分为两组(20m/min训练组和对照组)。训练方案为60min，5d/wk，10wk。采用聚合酶链式反应(PCR)技术对比目鱼(Soleus)和足底分枝杆菌(Pla)的线粒体DNA进行分析。检查与年龄相关的4.8kb缺失(常见缺失)的存在以及每只大鼠检测到的缺失产物的数量。通过每组大鼠的数量来评估常见缺失的存在，并通过计算每只大鼠可见的缺失产物来估计缺失的数量。2只青年大鼠(6.9%)和9只老年大鼠(56.3%)在SOL中有共同缺失，而2只青年大鼠(6.9%)和15只老年大鼠(93.8%)在聚乳酸中有共同缺失。无论是青年组还是老年组，耐力训练对共同缺失的出现均无影响。在老年组中，常见缺失的发生率在解放军高于SOL。随着年龄的增长，聚乳酸基因缺失的数量显著增加(p&lt；0.01)。而SOL基因缺失数目在青年组和老年组之间无显着性差异。在任何一组中，都没有观察到训练对缺失数目的影响。在青年组中，SOL组的mtDNA缺失产物数高于PLA组。然而，在老年组，SOL的值低于PLA。因此，我们可以检测到大鼠骨骼肌中与年龄相关的mtDNA缺失的积累，而本研究中没有观察到耐力训练对此的影响。此外，mtDNA缺失的累积可以根据纤维类型的不同而特定。较少

It has been proposed that age-associate decline of muscle metabolism of energy product are resulted from the accumulation of mitochondrial DNA (mtDNA) deletions in several species (Linnane et al., 1989). However, age-associated mt DNA deletions have not been successfully detected in the rat skeletal muscles (Filser et al., 1997). Exercise has been known to improve the muscle metabolism and then may have a benefit to prevent the accumulation of mtDNA deletions with age. As long as we know, little has been known about the effects of exercise on the accumulation of mtDNA deletions so far. The purpose of this study was to detect the age-associated mtDNA deletions in the rat skeletal muscles, and to examine whether endurance training effects on the accumulation of mtDNA deletions with age in different type of skeletal muscle. We used forty five Wistar male rats (10 wks : n=29, 90 wks : n=16) in this study. Young rats were divided into three groups (20 m/min training group, 30 m/min training … More group and control group) and old rats were divided into two groups (20 m/min training group and control group). The training protocol consisted of 60 min, 5 days/wk for 10 wks. MtDNA of m. soleus (SOL) and m.plantaris (PLA) were analyzed by polymerase chain reaction (PCR). The presence of age-associated 4.8-kb deletion (common deletion) and the number of deletion products detected per rat were examined. The presence of common deletion was evaluated by the number of rats in each group and the number of deletion was estimated by counting the deletion products visualized per rat. Two of the young rats (6.9%) and nine of the old rats (56.3%) had common deletion in SOL, while two of the young rats (6.9%) and fifteen of the old rats (93.8%) had in PLA. No effect of the endurance training on the presence of common deletion was seen in either the young group or the old group. In the old group, the presence of common deletion was higher in PLA than that in SOL. The numbers of deletion in PLA increased with age significantly (p<0.01). However the numbers of deletion in SOL showed no significant difference between the young and the old groups. The training effect on the numbers of deletion was not observed in any groups. In the young group, the number of mtDNA deletion products in SOL was higher than that in PLA. In the old group, however, the value was lower in SOL than in PLA.In conclusion, we could detect the accumulation of age-associated mtDNA deletions of the rat skeletal muscles, and observed no endurance training effect on that in this study. Moreover, the accumulation of mtDNA deletions can be specific according to fiber types. Less