Amino acid availability and age affect the leucine stimulation of protein synthesis and eIF4F formation in muscle
- 1 December 2007
- journal article
- research article
- Published by American Physiological Society in American Journal of Physiology-Endocrinology and Metabolism
- Vol. 293 (6), E1615-E1621
- https://doi.org/10.1152/ajpendo.00302.2007
Abstract
We have previously shown that a physiological increase in plasma leucine for 60 and 120 min increases translation initiation factor activation in muscle of neonatal pigs. Although muscle protein synthesis is increased by leucine at 60 min, it is not maintained at 120 min, perhaps because of the decrease in plasma amino acids (AA). In the present study, 7- and 26-day-old pigs were fasted overnight and infused with leucine (0 or 400 μmol·kg−1·h−1) for 120 min to raise leucine within the postprandial range. The leucine was infused in the presence or absence of a replacement AA mixture (without leucine) to maintain baseline plasma AA levels. AA administration prevented the leucine-induced reduction in plasma AA in both age groups. At 7 days, leucine infusion alone increased eukaryotic initiation factor (eIF) 4E binding protein-1 (4E-BP1) phosphorylation, decreased inactive 4E-BP1·eIF4E complex abundance, and increased active eIF4G·eIF4E complex formation in skeletal muscle; leucine infusion with replacement AA also stimulated these, as well as 70-kDa ribosomal protein S6 kinase, ribosomal protein S6, and eIF4G phosphorylation. At 26 days, leucine infusion alone increased 4E-BP1 phosphorylation and decreased the inactive 4E-BP1·eIF4E complex only; leucine with AA also stimulated these, as well as 70-kDa ribosomal protein S6 kinase and ribosomal protein S6 phosphorylation. Muscle protein synthesis was increased in 7-day-old (+60%) and 26-day-old (+40%) pigs infused with leucine and replacement AA but not with leucine alone. Thus the ability of leucine to stimulate eIF4F formation and protein synthesis in skeletal muscle is dependent on AA availability and age.Keywords
This publication has 31 references indexed in Scilit:
- Developmental regulation of the activation of signaling components leading to translation initiation in skeletal muscle of neonatal pigsAmerican Journal of Physiology-Endocrinology and Metabolism, 2006
- Leucine supplementation improves muscle protein synthesis in elderly men independently of hyperaminoacidaemiaThe Journal of Physiology, 2006
- Regulation of cardiac and skeletal muscle protein synthesis by individual branched-chain amino acids in neonatal pigsAmerican Journal of Physiology-Endocrinology and Metabolism, 2006
- Physiological rise in plasma leucine stimulates muscle protein synthesis in neonatal pigs by enhancing translation initiation factor activationAmerican Journal of Physiology-Endocrinology and Metabolism, 2005
- Anabolic signaling deficits underlie amino acid resistance of wasting, aging muscleThe FASEB Journal, 2004
- Guidelines for reporting statistics in journals published by the American Physiological SocietyAmerican Journal of Physiology-Endocrinology and Metabolism, 2004
- Regulation of neonatal liver protein synthesis by insulin and amino acids in pigsAmerican Journal of Physiology-Endocrinology and Metabolism, 2004
- Nutrient-Independent and Nutrient-Dependent Factors Stimulate Protein Synthesis in Colostrum-Fed Newborn PigsPediatric Research, 1995
- PHAS-I as a Link Between Mitogen-Activated Protein Kinase and Translation InitiationScience, 1994
- Cleavage of Structural Proteins during the Assembly of the Head of Bacteriophage T4Nature, 1970