Mitochondrial and sarcoplasmic proteins, but not myosin heavy chain, are sensitive to leucine supplementation in old rat skeletal muscle.
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.
Guillet
Christelle
C
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.
Zangarelli
Aude
A
Mishellany
Anne
A
Rousset
Paulette
P
Sornet
Claire
C
Dardevet
Dominique
D
Boirie
Yves
Y
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
D024101:Mitochondrial Proteins; D009124:Muscle Proteins; D010649:Phenylalanine; D018995:Myosin Heavy Chains; D007930:Leucine; D000409:Alanine