ARS | Publication request: Somatotropin enhanced muscle protein synthesis in growing pigs is not modulated by insulin

Submitted to: Federation of American Societies for Experimental Biology Conference
Publication Type: Abstract Only
Publication Acceptance Date: February 18, 2008
Publication Date: April 5, 2008
Citation: Wilson, F.A., Nguyen, H.V., Suryawan, A., Orellana, R.A., Jeyapalan, A.S., Davis, T.A. 2008. Somatotropin enhanced muscle protein synthesis in growing pigs is not modulated by insulin [abstract]. Federation of American Societies for Experimental Biology Conference: Today's Research: Tomorrow's Health. Session: Animal Growth, April 5-9, 2008, San Diego, California. C287, Abstract #1114.2.

Technical Abstract: 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.