Abstract
Protein synthesis (PS) increases after a meal in neonates, but the time course of the changes in PS in different tissues after a meal is unknown. We aimed to evaluate the changes in tissue PS, mammalian target of rapamycin complex 1 (mTORC1) activation, and proportion of ribosomal protein (rp) mRNAs in polysomes over 4 h after a bolus meal in neonatal pigs (n = 6/group; 5- to 7-d-old). The results show a more sustained increase in PS in glycolytic compared with mixed fiber type muscles and no changes in oxidative muscles. PS increased in liver, jejunum, and pancreas but not in kidney and heart. Feeding did not affect AMP-activated protein kinase or RAS-related GTP binding B activation. Phosphorylation of tuberous sclerosis complex 2, proline-rich Akt substrate of 40 kD, mTOR, eukaryotic initiation factor 4E binding protein, and rp S6 kinase 1 increased in all tissues after feeding. The proportion of mRNAs encoding rp S4 and S8 in liver polysomes increased within 30 min postfeeding. These results suggest that feeding stimulates mTORC1 signaling in muscle and viscera, but mTORC1 activation alone is not sufficient to stimulate PS in all tissues.
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Abbreviations
- AA:
-
amino acids
- AMPK:
-
AMP-activated protein kinase
- BCAA:
-
branched-chain AA
- EAA:
-
essential AA
- 4EBP1:
-
eukaryotic initiation factor 4E binding protein 1
- GAPDH:
-
glyceraldehyde 3-phosphate dehydrogenase
- mTORC1:
-
mammalian target of rapamycin complex 1
- ODC:
-
ornithine decarboxylase
- PRAS40:
-
proline-rich Akt substrate of 40 kDa
- PS:
-
protein synthesis
- Rag:
-
Ras-related GTP binding protein
- rp:
-
ribosomal protein
- S6K1:
-
rp S6 kinase 1
- TAA:
-
total AA
- TSC2:
-
tuberous sclerosis complex 2
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Acknowledgements
We thank Rosemarie Almonaci and Sharon Rannels for technical assistance, Jerome Stubblefield and Rickey Bryant for animal care, E. O'Brian Smith for statistical assistance, Adam Gillum for graphics, and Linda Weiser for secretarial assistance.
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Supported, in part, by the National Institutes of Health grants R01 AR-44474, R01 DK15658, and K08 AR-51563 and the USDA/ARS under Cooperative Agreement number 6250510000-33.
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Gazzaneo, M., Orellana, R., Suryawan, A. et al. Differential Regulation of Protein Synthesis and mTOR Signaling in Skeletal Muscle and Visceral Tissues of Neonatal Pigs After a Meal. Pediatr Res 70, 253–260 (2011). https://doi.org/10.1203/PDR.0b013e3182276cfa
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DOI: https://doi.org/10.1203/PDR.0b013e3182276cfa
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