| Background:Critical limb ischemia is a serious state of peripheral vascular disease in the elderly,which often leads to limb necrosis,amputation and increased death.It is very important to preserve and improve the function of ischemic skeletal muscle.However,there is still a lack of effective treatment.At present,exercise therapy is relatively reliable,economical and effective,but its mechanism is unclear.Exercise can promote the production of irisin,which is a new myokin and closely related to energy metabolism.The mitochondria are the energy factories of skeletal muscle cells.The dynamic stability maintained by mitochondrial dynamics and mitophagy is related to the survival of skeletal muscle cells.Purpose:The purpose of this study is to explore the mechanism of irisin,and its precursor protein FNDC5 and mitochondria in exercise to improve the function of ischemic skeletal muscle,in order to provide a new treatment strategy for clinical.Methods:In this study,60 14-month-old male C57BL/6J mice were used to establish the critical limb ischemia model.To analyze the effects of moderate exercise program about four weeks after operation on ischemic limb function,gastrocnemius muscle weight and index and serum irisin level.And to explore the potential mechanism of exercise on ischemic skeletal muscle from the aspects of gastrocnemius muscle tissue morphology,mitochondrial function,m RNA and protein.Results:(1)The serum irisin level in the exercise group was significantly higher than that in the sedentary group(P<0.01).Exercise also significantly increased the expression levels of FNDC5 and its m RNA.(2)After the operation,all health indexes of mice recovered step by step,no mice died,and the weight of mice in the exercise group was significantly lower than that in sedentary group on the 28 th day after the operation,while the weight and index of ischemic gastrocnemius muscle were significantly increased(P<0.01),and the scores of limb tissue damage and function were relatively low(P < 0.05).It was found that the arrangement of the muscle fibers in the exercise group was more regular,and the cross sectional area,perimeter and feret diameter of the muscle fibers were improved,while the cross sectional area of the muscle fibers was improved significantly(P<0.05).The number of TUNEL positive cells and the fibrotic area of skeletal muscle in the exercise group decreased compared with that in the sedentary group(P < 0.01,P < 0.05).The ultrastructural analysis showed that the width of H-zone and the sarcomere length in the ischemic skeletal muscle exercise group increased compared with that in the sedentary group(P < 0.05,P < 0.01).(3)Through the detection of mitochondrial autophagy related protein expression and m RNA transcription level,it was found that exercise training in ischemic skeletal muscle tissue increased FNDC5,LC3-?/LC3-?,Atg12,ATG5,TFAM,BNIP,Beclin,Atg7 expression levels were statistically significant(P<0.05)except ATG5,while the expression levels of Atg12,Beclin,Atg7 increased significantly(P<0.01),and P62declined(P<0.05).At the same time,exercise also significantly increased the expression levels of LC3B,Atg12,Beclin m RNA(P<0.01),and ATG5m RNA(P<0.05).Conclusions:(1)Moderate exercise is safe and reliable for the treatment of critical limb ischemia in aged mice.Moderate exercise improves the ultrastructure of skeletal muscle in ischemic limb,inhibits the apoptosis and fibrosis of ischemic skeletal muscle cells.It increased the weight and weight ratio of ischemic skeletal muscle and promoted the recovery of skeletal muscle function after critical limb ischemia;(2)Exercise may play a protective and therapeutic role by up regulating FNDC5/Irisin signaling pathway,promoting mitochondrial fission and fusion and mitophagy.(3)FNDC5 / Irisin is expected to become a therapeutic target to intervene patients with CLI,and achieve exercise replacement therapy. |
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