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

已经提出，与年龄相关的能量产物的肌肉代谢的下降是由几个物种中线粒体DNA（mtDNA）缺失的积累引起的（Linnane等人，1989年）。然而，尚未在大鼠骨骼肌中成功检测到年龄相关的mtDNA缺失（Filser等人，1997年）。众所周知，运动可以改善肌肉代谢，然后可能有助于防止随着年龄的增长mtDNA缺失的积累。据我们所知，到目前为止，关于运动对mtDNA缺失积累的影响还知之甚少。本研究旨在检测大鼠骨骼肌中与年龄相关的线粒体DNA缺失，并探讨耐力训练是否影响不同类型骨骼肌中线粒体DNA缺失随年龄的累积。本研究使用45只Wistar雄性大鼠（10周：n=29，90周：n=16）。幼鼠分为3组（20 m/min训练组、30 m/min训练组 关于我们 老年大鼠分为2组（20 m/min训练组和对照组）。训练方案为60 min，5 d/wk，共10 wk。聚合酶链反应（PCR）分析比目鱼肌（SOL）和跖肌（PLA）。检查年龄相关的4.8-kb缺失（常见缺失）的存在和每只大鼠检测到的缺失产物的数量。通过每组中大鼠的数量评价共同缺失的存在，并通过计数每只大鼠可见的缺失产物来估计缺失的数量。SOL常见缺失2只（6.9%），老年大鼠9只（56.3%）; PLA常见缺失2只（6.9%），老年大鼠15只（93.8%）。无论是青年组还是老年组，耐力训练对常见缺失的存在都没有影响。在老年组中，PLA的共同缺失率高于SOL。PLA基因缺失数随年龄增长而显著增加（p<0.01）。SOL基因缺失数在青年组和老年组之间无显著性差异。在任何组中均未观察到训练对缺失数量的影响。青年组SOL中mtDNA缺失产物的数量高于PLA。在老年组，SOL组的缺失值低于PLA组。因此，我们可以检测到与年龄相关的大鼠骨骼肌线粒体DNA缺失的积累，并且在本研究中没有观察到耐力训练对其的影响。此外，mtDNA缺失的积累可以根据纤维类型而特异性地进行。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