title: Increased myogenic repressor Id mRNA and protein levels in hindlimb muscles of aged rats.
abstract: The objective of this study was to determine if levels of repressors to myogenic regulatory factors (MRFs) differ between muscles from young adult and aged animals. Total RNA from plantaris, gastrocnemius, and soleus muscles of Fischer 344 x Brown Norway rats aged 9 mo (young adult, n = 10) and 37 mo (aged, n = 10) was reverse transcribed and then amplified by PCR. To obtain a semiquantitative measure of the mRNA levels, PCR signals were normalized to cyclophilin or 18S signals from the corresponding reverse transcription product. Normalization to cyclophilin and 18S gave similar results. The mRNA levels of MyoD and myogenin were approximately 275-650% (P < 0.001) and approximately 500-1,100% (P < 0.001) greater, respectively, in muscles from aged compared with young adults. In contrast, the protein levels were lower in plantaris and gastrocnemius muscles and similar in the soleus muscle of aged vs. young adult rats. Id repressor mRNA levels were approximately 300-900% greater in fast and slow muscles of aged animals (P < or = 0.02), and Mist 1 mRNA was approximately 50% greater in the plantaris and gastrocnemius muscles (P < 0.01). The mRNA level of Twist mRNA was not significantly affected by aging. Id-1, Id-2, and Id-3 protein levels were approximately 17-740% greater (P < 0.05) in hindlimb muscles of aged rats compared with young adult rats. The elevated levels of Id mRNA and protein suggest that MRF repressors may play a role in gene regulation of fast and slow muscles in aged rats.
authors.affiliation: Laboratory of Muscle, Sarcopenia, and Muscle Diseases, Division of Exercise Physiology, West Virginia University School of Medicine, Morgantown, West Virginia 26506-9227, USA. salway@hsc.wvu.edu
authors.forename: Stephen E
authors.initials: SE
authors.lastname: Alway
authors.forename: Hans
authors.initials: H
authors.lastname: Degens
authors.forename: Dawn A
authors.initials: DA
authors.lastname: Lowe
authors.forename: Gururaj
authors.initials: G
authors.lastname: Krishnamurthy
mesh_terms: D000375:Aging / Q000473:pathology / Q000502:physiology*; D000818:Animals; D001284:Atrophy; D051792:Basic Helix-Loop-Helix Proteins; D001835:Body Weight; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D003893:Desmin / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression / Q000502:physiology; D051798:Inhibitor of Differentiation Protein 1; D051797:Inhibitor of Differentiation Protein 2; D051796:Inhibitor of Differentiation Proteins; D008297:Male; D018482:Muscle, Skeletal / Q000473:pathology / Q000502:physiology*; D017570:MyoD Protein / Q000235:genetics / Q000378:metabolism; D018006:Myogenic Regulatory Factors / Q000235:genetics* / Q000378:metabolism; D018008:Myogenin / Q000235:genetics / Q000378:metabolism; D018994:Myosin Light Chains / Q000235:genetics / Q000378:metabolism; D009363:Neoplasm Proteins; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D012337:RNA, Ribosomal, 18S / Q000235:genetics; D051381:Rats; D011914:Rats, Inbred BN; D011916:Rats, Inbred F344; D012097:Repressor Proteins; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051820:TCF Transcription Factors; D058125:Transcription Factor 7-Like 1 Protein; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic / Q000502:physiology; D051879:Twist-Related Protein 1
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D004268:DNA-Binding Proteins; D003893:Desmin; D051798:Inhibitor of Differentiation Protein 1; D051797:Inhibitor of Differentiation Protein 2; D051796:Inhibitor of Differentiation Proteins; D017570:MyoD Protein; D018006:Myogenic Regulatory Factors; D018008:Myogenin; D018994:Myosin Light Chains; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D012333:RNA, Messenger; D012337:RNA, Ribosomal, 18S; D012097:Repressor Proteins; D051820:TCF Transcription Factors; D058125:Transcription Factor 7-Like 1 Protein; D014157:Transcription Factors; D051879:Twist-Related Protein 1; C105074:Bhlha15 protein, rat; C497454:ID1 protein, rat; C497451:Id2 protein, rat; C503799:MYOG protein, human; C503803:Myog protein, rat; C544912:TCF7L1 protein, human; C553060:Tcf7l1 protein, rat; C497754:Twist1 protein, rat; C063403:myogenic factor 6; C075640:ID3 protein, human