title: Potential role for Id myogenic repressors in apoptosis and attenuation of hypertrophy in muscles of aged rats.
abstract: Aging attenuates the overload-induced increase in myogenic regulatory transcription factor (MRF) expression and the extent of muscle enlargement. To identify whether mRNA levels of repressors of the MRFs are greater in overloaded muscles from aged animals, overload was achieved in plantaris muscle of aged (33 mo; n = 14) and adult (9 mo; n = 17) rats. After 14 days, plantaris muscles in the overloaded limb were ~25% and 6% larger in adult and aged rats, respectively, compared with the contralateral limb. Hypertrophied muscles of adult rats had significantly greater levels of mRNA and protein levels for myogenin and MyoD compared with control muscles, but neither MRF increased with overload in muscles of aged rats. Muscles of aged rats had greater Id mRNA (150-700%) and protein repressor (200-6,000%) levels compared with adult rats. BAX and caspase 9 protein levels were 9,500% and 300% greater, respectively, in both control and hypertrophied muscles of aged rats compared with young adult rats. These data are consistent with the hypothesis that aging increases Id transcripts that activate apoptotic pathways involving BAX. This may contribute to sarcopenia by attenuating MRF protein levels in muscles of old animals.
authors.affiliation: Laboratory of Muscle, Sarcopenia, and Muscle Diseases, Division of Exercise Physiology, West Virginia University School of Medicine, Morgantown, West Virginia 26506, 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: Gururaj
authors.initials: G
authors.lastname: Krishnamurthy
authors.forename: Cheryl A
authors.initials: CA
authors.lastname: Smith
mesh_terms: D000375:Aging / Q000502:physiology*; D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D015415:Biomarkers; D001835:Body Weight / Q000502:physiology; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D006984:Hypertrophy; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D017570:MyoD Protein / Q000378:metabolism; D018008:Myogenin / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011916:Rats, Inbred F344; D012097:Repressor Proteins / Q000235:genetics / Q000502:physiology*; D051028:bcl-2-Associated X Protein
chemical_list: C494828:Bax protein, rat; D015415:Biomarkers; D017570:MyoD Protein; C503803:Myog protein, rat; D018008:Myogenin; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D012097:Repressor Proteins; D051028:bcl-2-Associated X Protein; C506435:Casp9 protein, rat; D053453:Caspase 9; D020169:Caspases