Submitted to: Journal of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: 4/27/2007
Publication Date: 7/8/2007
Citation: Wilson, F.A., Nguyen, H.V., Suryawan, A., Orellana, R.A., Fleming, J.G., Jeyapalan, A.S., Davis, T.A. 2007. Modulation of protein synthesis by somatotropin and insulin in skeletal muscle of growing pigs [abstract]. Journal of Animal Science, Proceeding of the 2007 Annual Meeting of the American Society of Animal Science, July 8-12, 2007, San Antonio, Texas. 85(Suppl. 1):M144, p. 49. Interpretive Summary:
Technical Abstract: Chronic treatment of pigs with porcine somatotropin (pST) for 7 days increases feed efficiency by both promoting whole body protein synthesis in the fed state and reducing whole body protein degradation during fasting. pST-treated pigs have higher plasma insulin levels than vehicle-treated controls. This study aims to determine whether the increase in protein synthesis of pST-treated pigs is mediated through an insulin-induced stimulation of translation initiation. Growing pair-fed, weight-matched pigs were treated with pST (150 µg/kg/day, n=18) or vehicle (n=18) for 7 to 10 days. Pancreatic glucose-amino acid clamps were performed in overnight fasted pigs to attain plasma insulin levels of 5, 25 and 50 µU/ml, equivalent to reported insulin levels in 1) fasted control and fasted ST-treated, 2) fed control, and 3) fed-pST treated pigs, respectively. Amino acid and glucose levels were maintained at fasting levels. Skeletal muscle protein synthesis was measured with the flooding dose method, and western blotting was used to identify changes in the abundance and activation of translation initiation factors in muscle. Statistical analysis was performed using ANOVA. Plasma levels of urea nitrogen were lowered (P<0.001) and insulin-like growth factor-1 levels increased (P<0.005) in pST-treated pigs, indicating effectiveness of pST treatment. Insulin increased protein synthesis in muscle of control (P=0.01) and pST-treated (P=0.07) pigs. Treatment with pST also increased muscle protein synthesis (P<0.05). The abundance of the active translation initiation complex eIF4G-eIF4E and the phosphorylation of eIF4G in muscle mirrored the changes in muscle protein synthesis in response to insulin, however there was no clear effect of pST. We conclude that both insulin and pST stimulate protein synthesis in skeletal muscle of growing pigs.