L-Arginine(L-Arg),the precursor of nitric oxide(NO),plays an important role in muscle function.Fast-twitch glycolytic fibres are more susceptible to age-related atrophy than slow-twitch oxidative fibres.The effect of L-Arg/NO on protein metabolism of fast-and slow-twitch muscle fibres was evaluated in chickens.In Exp.1,48 chicks at 1 day old were divided into 4 groups of 12 birds and subjected to 4 treatments:basal diet without supplementation or supplemented with 1％L-Arg,and water supple-mented with or without L-nitro-arginine methyl ester(L-NAME,18.5 mM).In Exp.2,48 chicks were divided into 4 groups of 12 birds fed with the basal diet and subjected to the following treatments:tap water(control),tap water supplemented with L-NAME(18.5 mM),or molsidomine(MS,0.1 mM),or 18.5 mM L-NAME+0.1 mM MS(NAMS).The regulatory effect of L-Arg/NO was further investigated in vitro with myoblasts obtained from chicken embryo pectoralis major(PM)and biceps femoris(BF).In vivo,dietary L-Arg supplementation increased breast(+14.94％,P＜0.05)and thigh muscle mass(+23.40％,P＜0.05);whereas,MS treatment had no detectable influence.However,L-NAME treatment blocked the beneficial influence of L-Arg on muscle development.L-Arg decreased(P＜0.05)protein synthesis rate,phosphorylated mTOR and ribosomal protein S6 kinase beta-1(p70S6K)levels in breast muscle,which was recovered by L-NAME treatment.In vitro,L-Arg or sodium nitroprusside(SNP)reduced protein synthesis rate,suppressed phosphorylated mTOR/p70S6K and decreased atrogin-1 and muscle RING finger 1(MuRF1)in myoblasts from PM muscle(P＜0.05).L-NAME abolished the inhibitory effect of L-Arg on protein synthesis and the mTOR/p70S6Kpathway.However,myoblasts from BF muscle showed the weak influence.Moreover,blocking the mTOR/p70S6K pathway with rapamycin suppressed protein synthesis of the 2 types of myoblasts;whereas,the protein expression of atrogin-1 and MuRF1 levels were restricted only in myoblasts from PM muscle.In conclusion,L-Arg/NO/mTOR/p70S6K pathway enhances protein accumulation and muscle development in fast-twitch glycolytic muscle in chickens.L-Arg/NO regulates protein turnover in a muscle fibre specific way,which highlights the po-tential clinical application in fast-twitch glycolytic muscle fibres.

Ruxia Wang;Kelin Li;Li Sun;Hongchao Jiao;Yunlei Zhou;Haifang Li;Xiaojuan Wang;Jingpeng Zhao;Hai Lin

Key Lab for Animal Biotechnology and Disease Control,Department of Animal Science,Shandong Agricultural University,Tai'an,271000,China;Institute of Biological Resources,Jiangxi Academy of Sciences,Nanchang,330096,China

动物营养（英文）

[1]Ruxia Wang;Kelin Li;Li Sun;Hongchao Jiao;Yunlei Zhou;Haifang Li;Xiaojuan Wang;Jingpeng Zhao;Hai Lin-.L-Arginine/nitric oxide regulates skeletal muscle development via muscle fibre-specific nitric oxide/mTOR pathway in chickens)[J].动物营养（英文）,2022(03):68-85

molsidomine,NAME+0,NAMS,atrogin,p70S6Kpathway

Arginine,nitric,oxide,regulates,skeletal,muscle,development,via,specific,mTOR,chickens,precursor,plays,important,role,function,Fast,twitch,glycolytic,fibres,are,more,susceptible,age,related,atrophy,than,slow,oxidative,effect,protein,metabolism,fast,was,evaluated,In,Exp,chicks,day,old,were,divided,into,groups,birds,subjected,treatments,basal,without,supplementation,supplemented,water,arginine,methyl,ester,mM,fed,following,tap,control,regulatory,further,investigated,vitro,myoblasts,obtained,from,embryo,pectoralis,major,PM,biceps,femoris,BF,vivo,dietary,increased,breast,+14,thigh,mass,+23,whereas,had,detectable,influence,However,blocked,beneficial,decreased,synthesis,rate,phosphorylated,ribosomal,kinase,beta,levels,which,recovered,by,sodium,nitroprusside,SNP,reduced,suppressed,RING,finger,MuRF1,abolished,inhibitory,showed,weak,Moreover,blocking,rapamycin,types,expression,restricted,only,conclusion,enhances,accumulation,turnover,highlights,tential,clinical,application

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