亮氨酸促进老龄大鼠骨骼肌肥大模型蛋白合成相关信号的表达

LEUCINE PROMOTES PROTEIN SYNTHESIS RELATED SIGNAL EXPRESSION IN SKELETAL MUSCLE HYPERTROPHY MODEL OF AGED RATS

目的探讨老龄大鼠骨骼肌代偿性肥大过程中补充亮氨酸对骨骼肌肥大的影响及可能机制。方法18只24月龄雄性SD大鼠,采用右侧腓肠肌远端腱切术建立骨骼肌肥大模型。手术24 h后,随机分为亮氨酸补充低剂量组[n=5,Leu1,175 mg/(kg bw)]、亮氨酸补充高剂量组[5只,Leu2,350 mg/(kg bw)]以及生理盐水对照组(8只,saline),每日1次,共7 d。最后一次灌胃结束12 h后取材,检测血清胰岛素含量、骨骼肌质量、mTOR、P70S6K、rps6及其相应磷酸化蛋白表达水平。结果与对照组相比,补充亮氨酸组血清中胰岛素水平均显著性增加(P<0.05,P<0.05);与假手术侧相比,手术侧比目鱼肌和跖肌肌肉质量均显著性增加(P<0.05);与对照组手术侧相比,低剂量亮氨酸补充组手术侧跖肌的质量显著增加(P<0.05),跖肌mTOR、p70s6k和rps6及其相应磷酸化蛋白表达显著升高(P<0.05),而高剂量组则无显著性增加。结论低剂量亮氨酸补充和远端腱切术协同促进骨骼肌肥大,但存在肌纤维类型特异性,这可能与胰岛素、mTOR及其下游信号通路激活有关。

Objective To investigate the effects of leucine supplementation on skeletal muscle in aged rats during skeletal muscle compensatory hypertrophy and its possible mechanism.Methods Eighteen male Sprague-Dawley rats(24 months old)were treated with distal tenotomy of gastrocnemius muscle in the right hind limb.Twenty-four hourt after surgery,they were randomly divided into low-dose leucine supplementation group(Leu1,175mg/(kg·d),n=5),high-dose leucine supplementation group(Leu2,350 mg/(kg·d),n=5)and control group supplemented with saline(n=8).The experiment lasted for 7d.Twenty hour after the last 12h intragastric administration,rats were sacrificed and collected samples.Serum insulin,skeletal muscle mass,the proteins of mTOR/p-mTOR,p70S6k/P-p70s6k/p70s6k and P-rps6/rps6 expression were measured.Results Compared with the control group,the level of serum insulin significantly increased in Leu1 and Leu2 groups.The muscle mass of plantaris and soleus in all groups was significantly increased(P<0.05).Compared with the control group,the muscle mass of plantaris underwent tenotomy in Leu1 group was significantly increased.Compared with control group,relative expression of P-mTOR/mTOR,P-p70s6k/p70s6k and P-rps6/rps6 in skeletal muscle in Leu1 group was increased significantly,while there was no significant increase in Leu2 group.Conclusion Leucine supplementation and distal tenotomy synergistically promoted skeletal muscle hypertrophy in aging rats,but the response existed difference according to muscle fiber type,which may be related to insulin and mTOR signal pathways.