PMID- 11053498
OWN - NLM
STAT- MEDLINE
DCOM- 20001208
LR  - 20240109
IS  - 0022-3166 (Print)
IS  - 0022-3166 (Linking)
VI  - 130
IP  - 11
DP  - 2000 Nov
TI  - Stimulation of in vitro rat muscle protein synthesis by leucine decreases with 
      age.
PG  - 2630-5
AB  - Aging is characterized by a decrease of muscle mass associated with a decrease in 
      postprandial anabolism. This study was performed to gain a better understanding 
      of the intracellular mechanisms involved in the stimulation of muscle protein 
      synthesis by amino acids and their role in the decrease of muscle sensitivity to 
      food intake during aging. The effects of amino acids or leucine alone were 
      assessed in vitro on epitrochlearis muscle from young, adult and old rats. 
      Protein synthesis was assessed by incorporation of radiolabeled phenylalanine 
      into protein and p70 S6 kinase activity by incorporation of (32)P into a 
      synthetic substrate. Amino acids, at physiologic concentrations, stimulated 
      muscle protein synthesis (P < 0.05) and leucine reproduced this effect. The 
      intracellular targets of amino acids were phosphatidylinositol 3' kinase and the 
      rapamycin-sensitive pathways mammalian target of rapamycin (mTOR)/p70 S6 kinase. 
      In old rats, the sensitivity of muscle protein synthesis to leucine was lower 
      than in adults (P < 0.05) and this paralleled the lesser ability of leucine to 
      stimulate the rapamycin-sensitive pathways (P < 0.05). We demonstrated that amino 
      acids and leucine stimulate muscle protein synthesis and that aging is associated 
      with a decrease in this effect. However, because aged rats are still able to 
      respond normally to high leucine concentrations, we hypothesize that a 
      nutritional manipulation increasing the availability of this amino acid to muscle 
      could be beneficial in maintaining the postprandial stimulation of protein 
      synthesis.
FAU - Dardevet, D
AU  - Dardevet D
AD  - Human Nutrition Research Center of Clermont-Ferrand and Institut National de la 
      Recherche Agronomique, Unite d'Etude du Metabolisme Azote, 63122 Ceyrat, France.
FAU - Sornet, C
AU  - Sornet C
FAU - Balage, M
AU  - Balage M
FAU - Grizard, J
AU  - Grizard J
LA  - eng
PT  - Journal Article
PL  - United States
TA  - J Nutr
JT  - The Journal of nutrition
JID - 0404243
RN  - 0 (Amino Acids)
RN  - 0 (Chromones)
RN  - 0 (Enzyme Inhibitors)
RN  - 0 (Flavonoids)
RN  - 0 (Immunosuppressive Agents)
RN  - 0 (Morpholines)
RN  - 0 (Muscle Proteins)
RN  - 0 (Phosphoinositide-3 Kinase Inhibitors)
RN  - 31M2U1DVID (2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one)
RN  - GMW67QNF9C (Leucine)
RN  - SJE1IO5E3I (2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one)
RN  - W36ZG6FT64 (Sirolimus)
SB  - IM
MH  - Aging/*metabolism
MH  - Amino Acids/metabolism/pharmacology
MH  - Animals
MH  - Chromones/pharmacology
MH  - Enzyme Inhibitors/pharmacology
MH  - Flavonoids/pharmacology
MH  - Immunosuppressive Agents/pharmacology
MH  - Leucine/*metabolism/pharmacology
MH  - Male
MH  - Morpholines/pharmacology
MH  - Muscle Proteins/*biosynthesis/drug effects
MH  - Phosphoinositide-3 Kinase Inhibitors
MH  - Rats
MH  - Rats, Wistar
MH  - Sirolimus/pharmacology
EDAT- 2000/10/29 11:00
MHDA- 2001/02/28 10:01
CRDT- 2000/10/29 11:00
PHST- 2000/10/29 11:00 [pubmed]
PHST- 2001/02/28 10:01 [medline]
PHST- 2000/10/29 11:00 [entrez]
AID - 10.1093/jn/130.11.2630 [doi]
PST - ppublish
SO  - J Nutr. 2000 Nov;130(11):2630-5. doi: 10.1093/jn/130.11.2630.