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Title: Enhanced skeletal muscle protein synthesis rates in pigs treated with somatotropin requires fed amino acids levels

Author
item WILSON, FIONA - BAYLOR COLLEGE MED
item Suryawan, Agus
item ORELLANA, RENÁN - BAYLOR COLLEGE MED
item NGUYEN, HANH - BAYLOR COLLEGE MED
item JEYAPALAN, ASUMTHIA - BAYLOR COLLEGE MED
item GAZZANEO, M. CAROLINE - BAYLOR COLLEGE MED
item Davis, Teresa

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 6/11/2008
Publication Date: 7/1/2008
Citation: Wilson, F.A., Suryawan, A., Orellana, R.A., Nguyen, H.V., Jeyapalan, A.S., Gazzaneo, M.C., Davis, T.A. 2008. Enhanced skeletal muscle protein synthesis rates in pigs treated with somatotropin requires fed amino acids levels [abstract]. The American Dairy Science Association and the American Society of Animal Science Joint Annual Meeting, July 7-11, 2008, Indianapolis, Indiana. Journal of Animal Science, 86(E-Suppl. 2) and the Journal of Dairy Science, 91(E-Suppl. 1), Session: Growth and Development: Historical Perspective and Future Direction. p. 312.

Interpretive Summary:

Technical Abstract: Chronic somatotropin (pST) treatment in pigs increases skeletal muscle protein synthesis and circulating insulin, a known promoter of protein synthesis. Previously, we showed that the pST-mediated rise in insulin alone could not account for the pST-induced increase in protein synthesis. This study aimed to determine whether the pST-induced increase in insulin promotes skeletal muscle protein synthesis when amino acids are not limiting and are provided at fed levels, and whether the response is associated with enhanced translation initiation factor activation. Growing pigs were treated with pST (180 µg/kg/day, n=18) or saline (n=18) for 7 days, then pancreatic-glucose-amino acid clamps were performed to obtain plasma insulin levels equivalent to fasted or fed-pST treated pigs. Amino acids were raised to fed levels at both fasted and fed insulin concentrations; glucose was maintained at fasting levels throughout. Treatment with pST decreased plasma urea nitrogen and increased insulin-like growth factor(-1) levels (P<0.001), confirming effectiveness of treatment. Skeletal muscle protein synthesis was increased by pST treatment and by insulin and/or amino acid infusion (P<0.001). When amino acids were raised to fed levels, in the presence or absence of fed insulin concentrations, muscle protein synthesis rates were higher in pigs treated with pST than saline (P<0.02). Fed amino acids, with or without raised insulin concentrations, increased the phosphorylation of S6K1 and 4EBP1, decreased the inactive 4EBP1•eIF4E complex association, and increased active eIF4E•eIF4G complex formation (P<0.02). However, treatment with pST did not alter translation initiation factor activation. We conclude that the pST-induced stimulation of muscle protein synthesis requires fed levels of amino acid, but this response is not mediated by mRNA binding to the ribosomal complex.