Résumé
AIM:To investigate the influence of calorie restriction ( CR) on contractility and mitochondrial bi-osynthesis in different types of rat skeletal muscles .METHODS:CR rat model was set up by feeding 60%normal food in-take of control rat every day for 8 weeks.Soleus (SOL) and extensor digitorum longus (EDL) were isolated under anesthe-sia.The twitch tension, titanic tension and fatigue resistance of SOL and EDL in response to electrical stimulation were measured to reflect the contractile function of the muscles .The copy number ratio of mitochondrial gene cytochrome C oxi-dase subunit I ( COX I) to nuclear gene β-actin was determined to evaluate the mitochondrial biosynthesis .ATP content was measured to mirror mitochondrial function .RESULTS:Compared with control group , CR for 8 weeks significantly in-creased twitch tension and titanic tension of both SOL and EDL , but only improved fatigue resistance in SOL .Markedly in-crease in ATP content in both skeletal muscles by CR intervention was observed , especially in SOL .Although CR activated AMP-activated protein kinase (AMPK) in both 2 muscles, up-regulation of mitochondrial biosynthesis and transcription of mitochondrial regulatory genes peroxisome proliferator-activated receptor γcoactivator 1α( PGC-1α) and nuclear respirato-ry factor ( NRF) was only observed in SOL .CONCLUSION:CR for 8 weeks enhanced the contractility of both rat SOL and EDL in response to electrical stimulation , especially in SOL composed of slow-twitch fibers.The mechanisms may be related to the activation of AMPK and the promotion of mitochondrial biosynthesis in SOL .
Résumé
Aim This study was aimed to explore the influence and mechanism of the long-term exercise on skeletal muscle contraction and mitochondrial biosyn-thesis in different muscle fibers.Methods Soleus (SOL)and extensor digitorum longus (EDL)were i-solated from SD male rats with platform running train-ing for eight weeks.The changes of contractility under different electrical stimulation were observed, mito-chondrial biosynthesis,including ATP content,mito-chondrial DNA,the gene expression of PGC-1αand NRF were also detected.Results Long-term endur-ance exercise can improve twitch tension and titanic tension of SOL and EDL ,but only enhanced the fa-tigue resistance in SOL.ATP contents were significant-ly increased in the two types of muscles,but mtDNA content,PGC-1αexpression and NRF translation were only obviously enhanced in SOL,in accompanied with an increase in p-AMPK/AMPK protein ratio.Conclu-sion Long-term endurance exercise increased skeletal muscle contractility and improved the anti-fatigue abili-ty in SOL,which may be associated with increase in mitochondrial biosynthesis via activated AMPK-PGC-1αaxis.