좌골신경 손상 후 규칙적인 운동이 축삭재생, 비복근과 가자미근의 근 비대에 미치는 영향

Abstract

The purpose of the study was to identify the effect of regular exercise on axonal regrowth, soleus and gastrocnemius hypertrophy via inducing Akt/mTOR signaling pathway (study I: axonal regrowth and muscle hypertrophy proteins activation, study II: differences of axonal regrowth and muscle hypertrophy between muscle types by time point of exercise.) The experiment animals recruited in study I and study II were divided into 3 groups and 5 groups that is, the experimental groups were classified into control (n=10), sedentary 7 days (n=10) and 14 days (n=10) after SNI, and by exercise for 7 days (n=10) and 14 days (n=10) after SNI of study I respectively. Also study II was classified into normal group (Norm, n=10), sedentary after SNI (SAI, n=10), exercise before SNI (EBI, n=10), exercise after SNI (EAI, n=10), exercise before & after SNI (EBAI, n=10) respectively. The rats in exercise group were forced to run on treadmill device (study I: 8m/min, study II: 15m/min) for 20min once a day for 2 weeks. Identification of GAP-43 expression level and DRG neurite outgrowth length around nucleus, and muscle fiber size in ipsilateral soleus were analyzed by immunofluorescence method. Also, expression level of proteins for axonal regrowth and muscle hypertrophy was analyzed with a Western blot. The results obtained in this study were as follows; Study I: axonal regrowth and muscle hypertrophy activation 1) Axonal regrowth ① Neurite outgrowth length around nuclei in DRG showed more significant differences in exercise than sedentary group. ② Expression level of GAP-43 showed significant difference in injured sciatic nerve of exercise than sedentary group. ③ Axonal regrowth involved GAP-43 expression showed significant increase at nerve distal to damaged site in exercise when compared to that in sedentary group. ④ Expression level of ERK1/2 in exercise group showed significant difference at an early stage of regeneration after nerve injury. ⑤ Expression level of CREB in exercise group showed significant difference at an early stage of regeneration after nerve injury. ⑥ Expression level of ATF3 and c-Jun as transcription factors in exercise group showed significant difference at an early stage of regeneration after nerve injury. 2) Activation of muscle hypertrophy ① Expression level of ERK1/2 showed significant difference in ipsilateral soleus of exercise than that of sedentary group. ② Expression level of Akt showed significant difference in ipsilateral soleus of exercise than that of sedentary group. ③ Expression level of mTOR showed significant difference in ipsilateral soleus of exercise than that of sedentary group. ④ Phosphorylation level of 4E-BP1 showed significant difference in ipsilateral soleus of exercise than that of sedentary group. Study II: axonal regrowth and muscle hypertrophy between soleus and gastrocnemius 1) Axonal regrowth ① Expression level of GAP-43 showed significant differences by time point of exercise at pre and post sciatic nerve injury. ② Expression level of ERK1/2 showed significant differences by time point of exercise at pre and post sciatic nerve injury. ③ Expression level of Akt showed significant differences by time point of exercise at pre and post sciatic nerve injury. ④ Expression level of mTOR showed significant differences by time point of exercise at pre and post sciatic nerve injury. 2) Activation of muscle hypertrophy in type I muscle ① Expression level of ERK1/2 by time point of exercise at pre and post SNI showed significant difference in ipsilateral soleus. ② Expression level of Akt by time point of exercise at pre and post SNI showed significant difference in ipsilateral soleus. ③ Expression level of mTOR by time point of exercise at pre and post SNI showed significant difference in ipsilateral soleus. ④ Expression level of 4E-BP1 by time point of exercise at pre and post SNI showed significant differences in ipsilateral soleus. 3) Activation of muscle hypertrophy in type II muscle ① Expression level of ERK1/2 by time point of exercise at pre and post SNI showed significant difference in ipsilateral gastrocnemius. ② Expression level of Akt by time point of exercise at pre and post SNI showed significant difference in ipsilateral gastrocnemius. ③ Expression level of mTOR by time point of exercise at pre and post SNI showed significant difference in ipsilateral gastrocnemius. ④ Expression level of 4E-BP1 by time point of exercise at pre and post SNI showed significant difference in ipsilateral gastrocnemius. 4) Differences in activation of muscle hypertrophy between type I and type II muscles ① ERK1/2 expression showed significant difference between type I and type II muscles. ② Akt expression showed significant difference between type I and type II muscles. ③ mTOR expression showed significant difference between type I and type II muscles. ④ p-4E-BP1 expression showed significant difference between type I and type II muscles.