|Orellana, Renán - BAYLOR COLLEGE MED|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: October 30, 2008
Publication Date: November 14, 2008
Citation: Davis, T.A., Suryawan, A., Orellana, R.A. 2008. Amino acids and insulin in neonatal growth [abstract]. The 6th International Congress on Farm Animal Endocrinology, Session: Growth and Metabolic Endocrinology, November 14-16, 2008, Roanoke, Virginia. p. 33. Technical Abstract: The rate of growth during the neonatal period is greater than at any other stage of postnatal life, and a majority of the mass increase is skeletal muscle. The rapid growth of skeletal muscle in the neonate is driven by an elevated rate of protein synthesis. Neonates are very efficient at utilizing their dietary amino acids for protein deposition, and this high efficiency is due to a profound stimulation of muscle protein synthesis in response to feeding. 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 activation of many of the positive regulators of the insulin and amino acid signaling pathways are enhanced in neonatal muscle is response to feeding, and this response decreases with development. Thus, the activation of the positive regulators, such as the insulin receptor, insulin receptor-substrate-1, phosphoinositide-3 kinase, phosphoinositide-dependent kinase-1, protein kinase B, mammalian target of rapamycin (mTOR), ribosomal protein S6 kinase-1, eukaryotic initiation factor (eIF) 4E-binding protein 1, and eIF4E associated with eIF4G, is greater in muscle of 7- than in 26-day-old pigs. The activation of negative regulators, including protein tyrosine phosphatase-1B, PTEN, protein phosphatase 2A, and tuberous sclerosis complex 1/2, is lower in 7- than in 26-day-old pigs. The highly sensitive insulin and amino acid signaling pathways in neonatal muscle converge at the master protein kinase, mTOR, resulting in enhanced activation of translation initiation factors that regulate the binding of mRNA to the 40S ribosomal complex. The enhanced activation of these signaling components in response to the post-prandial rise in insulin and amino acids contributes to the high rate of protein synthesis and rapid gain in skeletal muscle mass in neonates.