胸腺肽α1对衰老小鼠肌肉减少症的调控机制

Regulatory mechanism of thymosin α1 on sarcopenia in aging mice

目的 探讨胸腺肽α1对自噬接头蛋白SQSTM1/p62和衰老小鼠肌肉减少症的调节作用。方法 将小鼠成肌细胞(C2C12)分为对照组、地塞米松组、地塞米松+胸腺肽α1组、地塞米松+胸腺肽α1+p62沉默组。采用细胞计数试剂盒-8检测各组细胞增殖活性(450 nm波长的OD值)的变化,并检测各组C2C12的肌管细胞形成情况。另外,将30只SAMP8快速衰老小鼠用随机数表法分为SAMP8组、胸腺肽α1+SAMP8组及胸腺肽α1+p62沉默+SAMP8组,每组小鼠10只。检测各组小鼠的瘦体质量(LBM)与体质量(BM)的比值[LBM/BM(%)]。采用Western blotting法检测各组C2C12和小鼠肌肉组织中p62、肌球蛋白原D(MyoD)、肌原细胞转录因子(MyoG)、肌球蛋白重链(MyHC)、肌肉RING-指蛋白1(MuRF1)和肌肉萎缩相关蛋白(MAFbx)的表达。采用GraphPad PRISM 5.01软件进行数据分析。根据数据类型,组间比较采用t检验。结果 与对照组比较,地塞米松组细胞的增殖活性和肌管细胞形成能力均显著下调(均P<0.05),p62、MyoD、MyoG、MyHC的表达量都减少(均P<0.05),但MuRF1和MAFbx的表达量均增加(均P<0.05)。与地塞米松组比较,地塞米松+胸腺肽α1组的增殖活性和肌管细胞形成能力均显著上调(均P<0.05),而且p62、MyoD、MyoG、MyHC的表达量也都增加(均P<0.05),MuRF1和MAFbx的表达量均减少(均P<0.05)。与地塞米松+胸腺肽α1组比较,地塞米松+胸腺肽α1+p62沉默组的肌管细胞形成能力显著降低(均P<0.05),而且p62、MyoD、MyoG、MyHC的表达量也都减少(均P<0.05),但是MuRF1和MAFbx的表达量均增加(均P<0.05)。与SAMP8组比较,胸腺肽α1+SAMP8组的LBM/BM比值显著上调(P<0.05),p62的表达量增加(均P<0.05),但MuRF1和MAFbx的表达量均减少(均P<0.05)。与胸腺肽α1+SAMP8组比较,胸腺肽α1+p62沉默+SAMP8组的LBM/BM比值显著下调(P<0.05),p62的表达量减少(均P<0.05),但MuRF1和MAFbx的表达量均增加(均P<0.05)。结论 胸腺肽α1通过激活SQSTM1/p62信号从而缓解衰老小鼠的肌肉减少症。

Objective To investigate the regulatory effects of thymosin α1 on autophagy adaptor protein SQSTM1/p62 and on sarcopenia in the aging mice.Methods Mouse myoblasts(C2C12)were divided into control group,dexamethasone group,dexamethasone+thymosin α1 group,and dexamethasone+thymosin α1+p62 silence group.In each group,the proliferative activity(OD at 450 nm wavelength)of cells was examined using cell counting kit-8,and the formation of C2C12 muscle tube cells was detected.In addition,30 SAMP8 rapidly aging mice were divided into SAMP8 group,thymosin α1+SAMP8 group,and thymosin α1+p62 silence+SAMP8 group using random number table method,with 10 mice in each group.The ratio of lean body mass(LBM)to body mass(BM)of each group was detected.The expressions of p62,myosin D(MyoD),myogon transcription factor(MyoG),myosin heavy chain(MyHC),muscle ring-finger protein 1(MuRF1)and muscle atrophy related protein(MAFbx)in C2C12 and muscle tissues were detected by Western blotting.GraphPad PRISM 5.01 was used for statistical analysis.According to the data type,comparison between groups was preformed using t test.Results Compared with the control group,the proliferative activity and myotubule cell formation of dexamethasone group were significantly down-regulated(P<0.05 for both),the expression of p62,MyoD,MyoG and MyHC was decreased(P<0.05 for all),but the expression of MuRF1 and MAFbx was increased(P<0.05 for both).Compared with dexamethasone group,the proliferative activity and myoduct cell formation of dexamethasone+thymosin α1 group were significantly up-regulated(P<0.05 for both),and the expression of p62,MyoD,MyoG and MyHC was increased(P<0.05 for all),while the expression of MuRF1 and MAFbx was decreased(P<0.05 for both).Compared with dexamethasone+thymosin α1 group,the myoduct cell formation of dexamethasone+thymosin α1+p62 silence group was significantly decreased(P<0.05),and the expression of p62,MyoD,MyoG and MyHC was also decreased(P<0.05 for all).However,the expression of MuRF1 and MAFbx was increased(P<0.05 for both).Compared with SAMP8 group,the LBM/BM ratio of thymosin α1+SAMP8 group was significantly up-regulated(P<0.05),and the expression of p62 was increased(P<0.05),but the expression of MuRF1 and MAFbx was decreased(P<0.05 for both).Compared with thymosin α1+SAMP8 group,the LBM/BM ratio in+thymosin α1+p62 silence+SAMP8 group was significantly decreased(P<0.05),and the expression of p62 was decreased(P<0.05).But the expression of MuRF1 and MAFbx was increased(P<0.05 for both).Conclusion Thymosinα1 alleviates sarcopenia in the aging mice by activating SQSTM1/p62 signal.