Enhancement of myofibrillar proteolysis following infusion of amino acid mixture correlates positively with elevation of core body temperature in rats

• Published in: Journal of Nutritional Science and Vitaminology 2008, Vol.54(6), pp.467-474
• Main Authors: Yamaoka, I.(Otsuka Pharmaceutical Factory Inc., Naruto, Tokushima (Japan). Research and Development Center), Mikura, M, Nishimura, M, Doi, M, Kawano, Y, Nakayama, M
• Format: Article
• Language: English
• Subjects: ACIDE AMINE; AMINO ACIDS; Amino Acids - metabolism; Amino Acids - pharmacology; AMINOACIDOS; anesthesia; Animals; ARN MENSAJERO; ARN MESSAGER; BIODEGRADACION; BIODEGRADATION; Biological and medical sciences; BLOOD PLASMA; BODY TEMPERATURE; Body Temperature - drug effects; Feeding. Feeding behavior; FIBRAS MUSCULARES; FIBRE MUSCULAIRE; Fundamental and applied biological sciences. Psychology; HISTIDINA; HISTIDINE; hypothermia; Infusions, Intravenous; INJECTION; INYECCION; MESSENGER RNA; methylhistidine; Methylhistidines - blood; muscle; Muscle Fibers, Skeletal - metabolism; MUSCLE FIBRES; Muscle Proteins - biosynthesis; Muscle Proteins - metabolism; PLASMA SANGUIN; PLASMA SANGUINEO; protein metabolism; PROTEIN SYNTHESIS; RAT; RATA; RATS; Rats, Sprague-Dawley; RNA, Messenger - metabolism; SINTESIS DE PROTEINAS; SKP Cullin F-Box Protein Ligases - metabolism; SYNTHESE PROTEIQUE; TEMPERATURA DEL CUERPO; TEMPERATURE CORPORELLE; Tripartite Motif Proteins; Ubiquitin - metabolism; Ubiquitin-Protein Ligases - metabolism; Vertebrates: anatomy and physiology, studies on body, several organs or systems
• ISSN: 0301-4800; 1881-7742
• DOI: 10.3177/jnsv.54.467

Administration of an amino acid (AA) mixture stimulates muscle protein synthesis and elevates core body temperature (Tsub(b)), as characteristically found under anesthetic conditions. We tested the hypothesis that not only AA given, but also AA produced by degradation of endogenous muscular protein are provided for muscle protein synthesis, which is further reflected in Tsub(b) modifications. Rats were intravenously administered an AA mixture or saline in combination with the anesthetic propofol or lipid emulsion. We measured plasma 3-methylhistidine (MeHis) concentrations as an index of myofibrillar protein degradation, rectal temperature and mRNA expression of atrogin-1, MuRF-1 and ubiquitin in gastrocnemius and soleus muscles of rats following 3 h infusion of test solutions. Tsub(b) did not differ significantly between conscious groups, but was higher in the AA group than in the saline group among anesthetized rats. Plasma MeHis concentrations were higher in the AA group than in the saline group under both conditions. Plasma MeHis levels correlated positively with Tsub(b) of rats under both conditions. AA administration decreased mRNA levels of atrogin-1 and ubiquitin in gastrocnemius muscle and all mRNA levels in soleus muscle. These results suggest that AA administration enhances myofibrillar protein degradation and that the change is a determinant of Tsub(b) modification by AA administration. However, the mechanisms underlying AA administration-associated enhancement of myofibrillar proteolysis remains yet to be determined.