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ARS Home » Plains Area » Houston, Texas » Children's Nutrition Research Center » Research » Publications at this Location » Publication #113227
Title: DEVELOPMENTAL CHANGES IN THE FEEDING-INDUCED STIMULATION OF TRANSLATION INITIATION IN SKELETAL MUSCLE AND LIVER OF NEONATAL PIGS

Author
item Davis, Teresa
item NGUYEN, HANH - BAYLOR COLLEGE OF MED
item SURYAWAN, AGUS - BAYLOR COLLEGE OF MED
item BUSH, JILL - BAYLOR COLLEGE OF MED
item JEFFERSON, LEONARD - PENN STATE UNIV COLL MED
item KIMBALL, SCOT - PENN STATE UNIV COLL MED

Submitted to: American Journal of Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/17/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary: Researchers have learned that muscle tissue grows faster than other types of tissue in newborns. After neonates eat food, the protein synthesis in their muscles increases markedly, at a much higher rate than in other kinds of tissues. We wanted to find out about the mechanism that regulates this process. We have knowledge of the system that regulates this in cells in culture, and we wanted to find out whether the process works the same way in newborns. We used piglets as models for our study, and examined their protein synthesis after feeding. Our results showed that parts of the piglets' system operated in a manner similar to that in a cell culture. Protein synthesis is greatly upregulated in the newborn. This new understanding of a growth-support process may have future application to questions involving the growth of newborn babies.

Technical Abstract: The rapid gain in skeletal muscle mass in the neonate is associated with a marked elevation in skeletal muscle protein synthesis in response to feeding. The feeding-induced response decreases with development. To determine whether the response to feeding is regulated at the level of translation initiation, the expression, phosphorylation, and function of a number of eukaryotic initiation factors (eIF) were examined. Pigs at 7 an 26 days of age were either fasted overnight or fed porcine milk following an overnight fast. In muscle of 7-day-old pigs, the hyperphosphorylated form of the eIF4E repressor protein, 4E-BP1, was undetectable in the fasting state but rose to 60% of total 4E-BP1 after feeding; eIF4E phosphorylation was unaffected by feeding status. The amount of eIF4E in the inactive 4E-BP1 X eIF4E complex was reduced by 80% and the amount of eIF4E in the active eIF4E X eIF4G complex was increased 14-fold in muscle of 7-day-old pigs following feeding. The amount of 70 kDa ribosomal protein S6 (p70S6) kinase in the hyperphosphorylated form rose 2.5-fold in muscle of 7-day-old pigs after feeding. Each of these feeding-induced responses was blunted in muscle of 26-day-old pigs. EIF2B activity in muscle was unaffected by feeding status but decreased with development. Feeding produced similar changes in eIF characteristics in liver and muscle, however, the developmental changes in liver were not as apparent as in skeletal muscle. Thus, the results demonstrate that the developmental change in the acute stimulation of skeletal muscle protein synthesis by feeding is regulated by the availability of eIF4E for 48S ribosomal complex formation. The results further suggest that the overall developmental decline in skeletal muscle protein synthesis involves regulation by eIF2B.