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Translational controls of muscle protein synthesis are delayed and prolonged associated with ingestion of a complete meal
Author(s) -
Norton Layne Eiseman,
Layman Donald K,
Garlick Peter,
Brana Diego,
Anthony Tracy G,
Zhao Liying,
Devkota Suzanne,
Walker Dee
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.5.a714-b
Subject(s) - medicine , calorie , meal , endocrinology , ingestion , chemistry , amino acid , phosphorylation , p70 s6 kinase 1 , protein biosynthesis , skeletal muscle , biology , biochemistry , protein kinase b
The time course of muscle protein synthesis (MPS) and translation initiation following a leucine (Leu) dose is well characterized, with the response peaking at 30 min and complete by 120 min ( AJP 282 :–101, 2002). The objective of this study was to determine the time course of MPS and translation factor activities in response to a mixed macronutrient meal. Male rats (300g) were trained for 5d to eat 3 meals/d consisting of 20/50/30% calories from whey protein, carbohydrates and fats, respectively. Plasma and skeletal muscle were collected at time 0 (start time) after a 12 h fast and then at 45, 90, 135, 180 and 300 min after a 4g meal. Measurements include plasma insulin and amino acids, MPS and phosphorylation of translation factors 4E‐BP1 and p70S6 kinase (S6K). MPS was determined in rats killed 10 min after tail vein injection of a flooding dose of D 5 ‐Phe. D 5 ‐Phe incorporation and plasma amino acids were determined by GCMS. Plasma Leu increased at 45 min and remained elevated through 180 min. Phosphorylation of S6K and 4E‐BP1 were tightly correlated with plasma Leu concentrations (r=0.724 & r=0.730 p<0.0001). MPS however, increased at 45 min, peaked at 90 min, and returned to baseline fasting levels by 180 min. In conclusion, sustained plasma levels of Leu direct prolonged signaling via translation factors, but this does not equate to extended upregulation of global MPS. Supported by National Dairy Council & Kraft Foods