Feeding Rapidly Stimulates Protein Synthesis in Skeletal Muscle of Neonatal Pigs by Enhancing Translation Initiation

Food consumption increases protein synthesis in most tissues by promoting translation initiation, and in the neonate, this increase is greatest in skeletal muscle. In this study, we aimed to identify the currently unknown time course of changes in the rate of protein synthesis and the activation of factors involved in translation in neonatal muscle after a meal. After overnight food deprivation, 36 5- to 7-d-old piglets were administered a nutritionally complete bolus i.g. meal and were killed immediately before or 30, 60, 90, 120, or 240 min later. The increase in skeletal muscle protein synthesis peaked 30 min after the meal and this was sustained through 120 min, returning to baseline thereafter. The relative proportion of polysomes to nonpolysomes was higher only after 30 min. Protein kinase B phosphorylation peaked 30 min after feeding and returned to baseline by 90 min. The phosphorylation of mammalian target of rapamycin, eukaryotic initiation factor (eIF) 4E binding protein (4E-BP1), ribosomal protein S6, and eIF4G was increased within 30 min of feeding and persisted through 120 min, but all had returned to baseline by 240 min. The association of 4E-BP1.eIF4E was reduced and eIF4E.eIF4G increased 30 min after receiving a meal, remaining so for 120 min, before returning to baseline at 240 min. Thus, in neonates, food consumption rapidly increased skeletal muscle protein synthesis by enhancing translation initiation and this increase was sustained for at least 120 min after the meal but returned to baseline by 240 min after the feeding. J. Nutr. 139: 1873-1880, 2009.