Gastric Bolus Feeding Rapidly Stimulates Hepatic Protein Synthesis in Neonatal Pigs

Abstract

Growth and protein deposition rates are more rapid during the neonatal period than at any other stage of postnatal life. Feeding stimulates protein synthesis in the liver, as it does in other tissues of the neonatal pig. The purpose of this study was to examine the feeding‐induced time course of the changes in protein synthesis, the proportion of ribosomal protein (rp) mRNAs in polysomes, and translation factor phosphorylation in liver. Neonatal pigs (n=36; 5‐7 day old) received a gastric bolus meal and were sacrificed at fasting and after 30, 60, 90, 120, or 240 min post‐feeding. Liver protein synthesis reached a maximum 30 min post‐feeding, was sustained through 90 min, and returned to baseline by 240 min. The proportion of rp (S4 and S8) mRNAs in polysomes increased within 30 min of feeding, remained high at 120 min, and returned to baseline value by 240 min. Phosphorylation of eukaryotic initiation factor (eIF) 4E binding protein (4EBP1) and rp S6 kinase 1 (S6K1) increased by 30 min, remained elevated to 120 min, and returned to baseline by 240 min. These results suggest that feeding induced a rapid movement of hepatic rp mRNAs into polysomes and increased neonatal liver protein synthesis by enhancing translation initiation. Furthemore, these increases were sustained for at least 90 min after a meal, but returned to baseline by 240 min. (Supported by NIH grants AR‐44474 and DK‐15658 and USDA/ARS 6250510000‐33).