title: Effect of feeding a high-protein diet following an 18-hour period of feed withholding on mammalian target of rapamycin-dependent signaling in skeletal muscle of mature horses.
abstract: OBJECTIVE
  To determine the effect of refeeding following an 18-hour period of feed withholding on the phosphorylation of translation initiation factors in the skeletal muscle of mature horses.
  
  
  METHODS
  8 adult horses.
  
  
  METHODS
  Following an 18-hour period of feed withholding, horses either continued to have feed withheld (postabsorptive state) or were fed 2 g/kg of a high-protein feed (33% crude protein) at time 0 and 30 minutes (postprandial state). Blood samples were taken throughout the experimental period. At 90 minutes, a biopsy specimen was taken from the middle gluteal muscle to measure the phosphorylation of translation initiation factors and tissue amino acid concentrations. Plasma glucose, insulin, and amino acid concentrations were also measured.
  
  
  RESULTS
  Horses in the postprandial state had significantly higher plasma insulin, glucose, and amino acid concentrations than did those in the postabsorptive state at the time of biopsy. Refeeding significantly increased the phosphorylation state of riboprotein S6 and eukaryotic initiation factor 4E binding protein 1.
  
  
  CONCLUSIONS
  In mature horses, feeding resulted in increased mammalian target of rapamycin signaling and the mechanism appeared to be independent of an increase in Akt phosphorylation at Ser⁴⁷³. Results indicate that adult horses may be able to increase rates of muscle protein synthesis in response to feeding and that dietary amino acids appear to be the main mediators of this effect.
authors.affiliation: Middleburg Agricultural Research and Extension Center, Virginia Tech, Middleburg, VA 20117, USA. klur222@uky.edu
authors.forename: Kristine L
authors.initials: KL
authors.lastname: Urschel
authors.forename: Jeffery
authors.initials: J
authors.lastname: Escobar
authors.forename: L Jill
authors.initials: LJ
authors.lastname: McCutcheon
authors.forename: Raymond J
authors.initials: RJ
authors.lastname: Geor
mesh_terms: D000596:Amino Acids / Q000097:blood; D000821:Animal Feed / Q000032:analysis; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001786:Blood Glucose; D004032:Diet / Q000662:veterinary; D004044:Dietary Proteins / Q000008:administration & dosage / Q000494:pharmacology*; D005260:Female; D005508:Food Deprivation; D005786:Gene Expression Regulation / Q000187:drug effects; D006736:Horses; D007328:Insulin / Q000097:blood; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism; D018482:Muscle, Skeletal / Q000378:metabolism*; D019518:Postprandial Period; D015398:Signal Transduction / Q000502:physiology*; D058570:TOR Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*
chemical_list: D000596:Amino Acids; D001786:Blood Glucose; D004044:Dietary Proteins; D007328:Insulin; D009124:Muscle Proteins; D058570:TOR Serine-Threonine Kinases