PMID- 32835365
OWN - NLM
STAT- MEDLINE
DCOM- 20201125
LR  - 20211204
IS  - 1525-3163 (Electronic)
IS  - 0021-8812 (Print)
IS  - 0021-8812 (Linking)
VI  - 98
IP  - 9
DP  - 2020 Sep 1
TI  - Pathways regulating equine skeletal muscle protein synthesis respond in a 
      dose-dependent manner to graded levels of protein intake.
LID - 10.1093/jas/skaa268 [doi]
LID - skaa268
AB  - Activation of the mechanistic target of rapamycin (mTOR)-controlled anabolic 
      signaling pathways in skeletal muscle of rodents and humans is responsive to the 
      level of dietary protein supply, with maximal activation and rates of protein 
      synthesis achieved with 0.2 to 0.4 g protein/kg body weight (BW). In horses, few 
      data are available on the required level of dietary protein to maximize protein 
      synthesis for maintenance and growth of skeletal muscle. To evaluate the effect 
      of dietary protein level on muscle mTOR pathway activation, five mares received 
      different amounts of a protein supplement that provided 0, 0.06, 0.125, 0.25, or 
      0.5 g of crude protein (CP)/kg BW per meal in a 5 x 5 Latin square design. On 
      each sample day, horses were fasted overnight and were fed only their protein 
      meal the following morning. A preprandial (0 min) and postprandial (90 min) blood 
      sample was collected and a gluteus medius muscle sample was obtained 90 min after 
      feeding the protein meal. Blood samples were analyzed for glucose, insulin, and 
      amino acid concentrations. Activation of mTOR pathway components (mTOR and 
      ribosomal protein S6 [rpS6]) in the muscle samples was measured by Western 
      immunoblot analysis. Postprandial plasma glucose (P = 0.007) and insulin (P = 
      0.09) showed a quadratic increase, while total essential amino acid (P < 0.0001) 
      concentrations increased linearly with the graded intake of the protein 
      supplement. Activation of mTOR (P = 0.02) and its downstream target, rpS6 (P = 
      0.0008), increased quadratically and linearly in relation to the level of protein 
      intake, respectively. Comparisons of individual doses showed no differences (P > 
      0.05) between the 0.25 and 0.5 g of protein intake for either mTOR or rpS6 
      activation, indicating that protein synthesis may have reached near maximal 
      capacity around 0.25 g CP/kg BW. This is the first study to show that the 
      activation of muscle protein synthetic pathways in horses is dose-dependent on 
      the level of protein intake. Consumption of a moderate dose of high-quality 
      protein resulted in near maximal muscle mTOR pathway activation in mature, 
      sedentary horses.
CI  - (c) The Author(s) 2020. Published by Oxford University Press on behalf of the 
      American Society of Animal Science. All rights reserved. For permissions, please 
      e-mail: journals.permissions@oup.com.
FAU - Loos, Caroline M M
AU  - Loos CMM
AD  - Department of Animal and Food Sciences, University of Kentucky, Lexington, KY.
FAU - McLeod, Kyle R
AU  - McLeod KR
AD  - Department of Animal and Food Sciences, University of Kentucky, Lexington, KY.
FAU - Stratton, Sophie C
AU  - Stratton SC
AD  - Department of Animal and Food Sciences, University of Kentucky, Lexington, KY.
FAU - van Doorn, David A
AU  - van Doorn DA
AD  - Equivado Consultancy B.V., Utrecht, The Netherlands.
FAU - Kalmar, Isabelle D
AU  - Kalmar ID
AD  - Department of Nutrition, Genetics and Ethology, Ghent University, Gent, Belgium.
FAU - Vanzant, Eric S
AU  - Vanzant ES
AD  - Department of Animal and Food Sciences, University of Kentucky, Lexington, KY.
FAU - Urschel, Kristine L
AU  - Urschel KL
AD  - Department of Animal and Food Sciences, University of Kentucky, Lexington, KY.
LA  - eng
PT  - Journal Article
PL  - United States
TA  - J Anim Sci
JT  - Journal of animal science
JID - 8003002
RN  - 0 (Blood Glucose)
RN  - 0 (Dietary Proteins)
RN  - 0 (Insulin)
RN  - 0 (Muscle Proteins)
RN  - EC 2.7.11.1 (TOR Serine-Threonine Kinases)
SB  - IM
MH  - Animals
MH  - Blood Glucose/analysis
MH  - Diet/veterinary
MH  - Dietary Proteins/*analysis
MH  - Dietary Supplements/*analysis
MH  - Fasting
MH  - Female
MH  - Horses/*physiology
MH  - Insulin/blood
MH  - Muscle Proteins/metabolism
MH  - Muscle, Skeletal/drug effects
MH  - Postprandial Period/drug effects
MH  - Protein Biosynthesis/*drug effects
MH  - Random Allocation
MH  - Signal Transduction/*drug effects
MH  - TOR Serine-Threonine Kinases/*metabolism
PMC - PMC7497812
OTO - NOTNLM
OT  - dietary protein
OT  - equine
OT  - mechanistic target of rapamycin
OT  - muscle protein synthesis
EDAT- 2020/08/25 06:00
MHDA- 2020/11/26 06:00
PMCR- 2021/08/24
CRDT- 2020/08/25 06:00
PHST- 2020/07/08 00:00 [received]
PHST- 2020/08/18 00:00 [accepted]
PHST- 2020/08/25 06:00 [pubmed]
PHST- 2020/11/26 06:00 [medline]
PHST- 2020/08/25 06:00 [entrez]
PHST- 2021/08/24 00:00 [pmc-release]
AID - 5896557 [pii]
AID - skaa268 [pii]
AID - 10.1093/jas/skaa268 [doi]
PST - ppublish
SO  - J Anim Sci. 2020 Sep 1;98(9):skaa268. doi: 10.1093/jas/skaa268.