Developmental regulation of the activation of translation initiation factors of skeletal muscle in response to feeding in horses

Ashley L. Wagner Department of Animal and Food Sciences, College of Agriculture, University of Kentucky, Lexington, KY 40546.

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Kristine L. Urschel Department of Animal and Food Sciences, College of Agriculture, University of Kentucky, Lexington, KY 40546.

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DOI:
https://doi.org/10.2460/ajvr.73.8.1241
Volume/Issue:
Volume 73: Issue 8
Online Publication Date:
01 Aug 2012
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Abstract

Objective—To determine whether feeding-induced activation of translation initiation factors, specifically protein kinase B, ribosomal protein S6 kinase (S6K1), ribosomal protein S6 (rpS6), and eukaryotic initiation factor 4E binding protein 1, in horses is affected by age.

Animals—6 yearlings, six 2-year-old horses, and 6 mature horses.

Procedures—After an 18-hour period of feed withholding, horses consumed a high-protein meal (2 g/kg) at time 0 and 30 minutes (postprandial state) or continued to have feed withheld (postabsorptive state). Blood samples were collected for the duration of the experimental procedures and used to determine plasma concentrations of glucose, insulin, and amino acids. At 90 minutes, biopsy specimens were collected from a gluteal muscle and used to measure phosphorylation of translation initiation factors.

Results—Plasma glucose, insulin, and amino acid concentrations were elevated for the postprandial state, compared with results for the postabsorptive state, regardless of age. Phosphorylation of protein kinase B, S6K1, rpS6, and eukaryotic initation factor 4E binding protein 1 was increased for the postprandial state. There was an effect of age with increased phosphorylation of S6K1 at Thr389 and rpS6 at Ser235/236 in the yearlings and mature horses, compared with results for the 2-year-old horses.

Conclusions and Clinical Relevance—Food consumption resulted in an increase in the activation of translation initiation factors, with the highest degree of responsiveness in the yearlings. This indicated that increased muscle accretion seen during growth could be a result of increased rates of muscle protein synthesis in response to a meal stimulus.

Abstract

Objective—To determine whether feeding-induced activation of translation initiation factors, specifically protein kinase B, ribosomal protein S6 kinase (S6K1), ribosomal protein S6 (rpS6), and eukaryotic initiation factor 4E binding protein 1, in horses is affected by age.

Animals—6 yearlings, six 2-year-old horses, and 6 mature horses.

Procedures—After an 18-hour period of feed withholding, horses consumed a high-protein meal (2 g/kg) at time 0 and 30 minutes (postprandial state) or continued to have feed withheld (postabsorptive state). Blood samples were collected for the duration of the experimental procedures and used to determine plasma concentrations of glucose, insulin, and amino acids. At 90 minutes, biopsy specimens were collected from a gluteal muscle and used to measure phosphorylation of translation initiation factors.

Results—Plasma glucose, insulin, and amino acid concentrations were elevated for the postprandial state, compared with results for the postabsorptive state, regardless of age. Phosphorylation of protein kinase B, S6K1, rpS6, and eukaryotic initation factor 4E binding protein 1 was increased for the postprandial state. There was an effect of age with increased phosphorylation of S6K1 at Thr389 and rpS6 at Ser235/236 in the yearlings and mature horses, compared with results for the 2-year-old horses.

Conclusions and Clinical Relevance—Food consumption resulted in an increase in the activation of translation initiation factors, with the highest degree of responsiveness in the yearlings. This indicated that increased muscle accretion seen during growth could be a result of increased rates of muscle protein synthesis in response to a meal stimulus.

Contributor Notes

Dr. Wagner's present address is Cooperative Research Farms, 1919 Huguenot Rd, Ste 200, Richmond, VA 23235.

This manuscript represents a portion of a dissertation submitted by the first author to the University of Kentucky Department of Animal and Food Sciences as partial fulfillment of the requirements for a Doctor of Philosophy degree.

Supported by the University of Kentucky Vice President for Research and the Kentucky Agricultural Experiment Station (Lexington).

Published by the Kentucky Agricultural Experiment Station as paper 11-07-048.

Presented in abstract form at the Experimental Biology Annual Meeting, Anaheim, Calif, April 2010; and the American Dairy Science Association, Poultry Science Association, Asociación Mexicana de Producción Animal, Canadian Society of Animal Science, American Society of Animal Science, and American Society of Animal Science Western Section Joint Annual Meeting, Denver, July 2010.

The authors thank Rosalyn B. Ennis and Jessica C. Gould for assistance with collection and analysis of samples.

Address correspondence to Dr. Urschel (klur222@uky.edu).
Cover American Journal of Veterinary Research
American Journal of Veterinary Research
Publication Date:
01 Aug 2012

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