title: Mitochondrial and sarcoplasmic proteins, but not myosin heavy chain, are sensitive to leucine supplementation in old rat skeletal muscle.
abstract: Leucine has a major anabolic impact on muscle protein synthesis in young as in old animals. However, myosin heavy chain (MHC), sarcoplasmic and mitochondrial proteins may differently respond to anabolic factors, especially during aging. To test this hypothesis, fractional synthesis rates (FSR) of the three muscle protein fractions were measured using a flooding dose of [1-(13)C] phenylalanine, in gastrocnemius muscle of adult (8 months) and old (22 months) rats, either in postabsorptive state (PA), or 90-120 min after ingestion of a alanine-supplemented meal (PP+A) or a leucine-supplemented meal (PP+L). In adult and old rats, in comparison with PA, leucine stimulated mitochondrial (adult: 0.260+/-0.011 vs 0.238+/-0.012%h(-1); old: 0.289+/-0.010 vs 0.250+/-0.010%h(-1); PP+L vs PA, P<0.05) and sarcoplasmic (adult: 0.182+/-0.011 vs 0.143+/-0.006%h(-1); old: 0.195+/-0.010 vs 0.149+/-0.008%h(-1); PP+L vs PA, P<0.05) protein FSR, but not MHC synthesis in old rats (0.101+/-0.009 vs 0.137+/-0.018%h(-1); PP+L vs PA, P=NS). In conclusion, synthesis of specific muscle protein is activated by leucine supplementation, but MHC may be less sensitive to anabolic factors with aging.
authors.affiliation: Laboratoire de Nutrition Humaine, Centre de Recherche en Nutrition Humaine, Unité du Métabolisme Protéino-Energétique, UMR Université d'Auvergne-INRA, Centre Hospitalier Universitaire, BP 321, 58 rue Montalembert, 63009 Clermont-Ferrand cedex 1, France.
authors.forename: Christelle
authors.initials: C
authors.lastname: Guillet
authors.forename: Aude
authors.initials: A
authors.lastname: Zangarelli
authors.forename: Anne
authors.initials: A
authors.lastname: Mishellany
authors.forename: Paulette
authors.initials: P
authors.lastname: Rousset
authors.forename: Claire
authors.initials: C
authors.lastname: Sornet
authors.forename: Dominique
authors.initials: D
authors.lastname: Dardevet
authors.forename: Yves
authors.initials: Y
authors.lastname: Boirie
mesh_terms: D000375:Aging / Q000502:physiology*; D000409:Alanine / Q000008:administration & dosage; D000818:Animals; D004032:Diet; D007930:Leucine / Q000008:administration & dosage*; D008297:Male; D024101:Mitochondrial Proteins / Q000096:biosynthesis*; D009124:Muscle Proteins / Q000096:biosynthesis*; D018482:Muscle, Skeletal / Q000378:metabolism*; D018995:Myosin Heavy Chains / Q000096:biosynthesis; D010649:Phenylalanine / Q000008:administration & dosage; D051381:Rats; D017208:Rats, Wistar; D012519:Sarcoplasmic Reticulum / Q000378:metabolism
chemical_list: D024101:Mitochondrial Proteins; D009124:Muscle Proteins; D010649:Phenylalanine; D018995:Myosin Heavy Chains; D007930:Leucine; D000409:Alanine