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Somatotropin Enhanced Muscle Protein Synthesis in Growing Pigs Is Not Modulated by Insulin
Author(s) -
Wilson Fiona A,
Nguyen Hanh V,
Suryawan Agus,
Orellana Renan A,
Jeyapalan Asumthia S,
Davis Teresa A
Publication year - 2008
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.22.1_supplement.1114.2
Subject(s) - medicine , endocrinology , insulin , protein biosynthesis , skeletal muscle , eif4g , insulin like growth factor , stimulation , amino acid , protein kinase b , chemistry , growth factor , biology , phosphorylation , translation (biology) , biochemistry , receptor , messenger rna , gene
Chronic, 7‐day treatment of growing pigs with porcine somatotropin (ST) promotes protein synthesis and doubles postprandial levels of insulin, a hormone that enhances translation initiation. This study aimed to determine whether the ST induced increase in skeletal muscle protein synthesis was mediated through an insulin‐induced stimulation of translation initiation. Pancreatic glucose‐amino acid clamps were performed in overnight fasted pigs after 7–10 days of ST (150 μg/kg/d) or vehicle treatment, to reproduce 1) fasted (5 μU/ml), 2) fed (25 μU/ml), and 3) fed‐ST treated (50 μU/ml) insulin levels, while glucose and amino acids were maintained at baseline fasting levels. Fractional protein synthesis rates were determined and translational control mechanisms were examined. Effectiveness of ST treatment was confirmed by reduced urea nitrogen (P<0.001) and elevated IGF‐1 levels (P < 0.01) in plasma. Skeletal muscle protein synthesis was independently increased by both insulin (P < 0.07) and ST (P < 0.05). Insulin enhanced eIF4G·eIF4E complex formation as well as PKB and eIF4G phosphorylation, but ST‐treatment did not alter translation initiation factor activation. We conclude that the ST‐induced stimulation of skeletal muscle protein synthesis in growing pigs is independent of the insulin‐associated activation of translation initiation. (Supported by USDA NRI 2005‐35206‐15273)