ARS | Publication request: A single bolus meal elicits different regulation of protein synthesis and mTOR signaling in visceral tissues and skeletal muscle of newborn pigs

Submitted to: Pediatric Academic Society
Publication Type: Abstract Only
Publication Acceptance Date: November 18, 2009
Publication Date: May 1, 2010
Citation: Gazzaneo, M.C., Suryawan, A., Orellana, R.A., Murgas-Torrazza, R., Nguyen, H.V., Wilson, F.A., Fiorotto, M.A., Davis, T.A. 2010. A single bolus meal elicits different regulation of protein synthesis and mTOR signaling in visceral tissues and skeletal muscle of newborn pigs [abstract]. In: Proceedings of the 2010 Pediatric Academic Societies Annual Conference, May 1-4, 2010, Vancouver, British Columbia, Canada. Paper No. 2745.4.

Technical Abstract: Neonates, a highly anabolic population, use dietary amino acids efficiently for growth because they can increase protein synthesis in response to feeding to a greater extent than mature animals. The enhancement of protein synthesis after a meal in neonatal pigs is well known, but the time course of the changes in different tissues has not been determined. The aim of this study was to evaluate the time course of the changes in protein synthesis rates and translation initiation factor activation in skeletal muscle and visceral tissues after a meal. Neonatal pigs (n=36; 5-7 day old) received a meal providing one-sixth of daily requirements and were sacrificed at 0, 30, 60, 90, 120, or 240 min after feeding. Protein synthesis increased 30 to 120 min in glycolytic muscles (longissimus dorsi and gastrocnemius), 30 to 90 min in mixed fiber type muscle (masseter), and did not increase in oxidative muscle (soleus) after a bolus meal. Protein synthesis increased in liver 30 to 120 min, jejunum 30 to 60 min and pancreas 30 min post-feeding and did not increase in kidney and heart. Eukaryotic initiation factor (eIF) 4E binding protein (4EBP1) and rp S6 kinase 1 (S6K1) phosphorylation increased 30 to 90 min in all tissues after a meal. In conclusion, these results suggest that feeding stimulates mTOR signaling in skeletal muscle and visceral tissues. However, mTOR activation alone was not sufficient to stimulate protein synthesis in all tissues. Therefore, frequent meals are necessary for sustaining optimal protein synthesis rates and, hence, muscle growth in the neonate.