NUTRITIONAL REGULATION OF CELL AND ORGAN GROWTH, DIFFERENTIATION, AND DEVELOPMENT
Location: Children Nutrition Research Center (Houston, Tx)
Title: Postnatal ontogeny of skeletal muscle protein synthesis in pigs
Submitted to: Journal of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: April 27, 2007
Publication Date: July 8, 2007
Citation: Davis, T.A., Suryawan, A., Orellana, R.A., Fiorotto, M.L. 2007. Postnatal ontogeny of skeletal muscle protein synthesis in 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):630, p. 445.
The neonatal period is characterized by rapid growth and elevated rates of synthesis and accretion of skeletal muscle proteins. The fractional rate of muscle protein synthesis is very high at birth and declines rapidly with development. The elevated capacity for muscle protein synthesis in the neonatal pig is driven by the high ribosome content and, together with an increased efficiency of the translation process, promotes accelerated protein synthesis rates. Feeding profoundly stimulates muscle protein synthesis in neonatal pigs, and the response decreases with age. The feeding-induced stimulation of muscle protein synthesis is modulated by an enhanced sensitivity to the post-prandial rise in insulin and amino acids. The developmental decline in the response to insulin and amino acids parallels a marked fall in the feeding-induced activation of translation initiation factors that regulate the binding of mRNA to the 40S ribosomal complex. The abundance and activation of many known positive regulators of the nutrient- and insulin-signaling pathways that are involved in translation initiation are high and that for many negative regulators are low in skeletal muscle of younger pigs. Thus, the activation and/or abundance of the positive regulators, insulin receptor, insulin receptor-substrate-1, phosphoinositide-3 kinase, phosphoinositide-dependent kinase-1, protein kinase B, mammalian target of rapamycin, raptor, ribosomal protein S6 kinase-1, eukaryotic initiation factor (eIF) 4E-binding protein 1, and eIF4E associated with eIF4G are greater in 7- than in 26-day-old pigs. The activation of negative regulators, protein tyrosine phosphatase-1B, PTEN, protein phosphatase 2A, and tuberous sclerosis complex 1/2 are lower in 7- than in 26-day-old pigs. The developmental changes in the abundance and activation of these signaling components likely contribute to the high rate of protein synthesis and rapid gain in skeletal muscle mass in neonates.