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Cited by 222Muscle metabolism and nutritionRuminant Nutrition and Digestive PhysiologyRNA and protein synthesis mechanisms

Isoleucine and Leucine Independently Regulate mTOR Signaling and Protein Synthesis in MAC-T Cells and Bovine Mammary Tissue Slices

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Appuhamy, J. A. D. Ranga Niroshan, Knoebel, Nicole A., Nayananjalie, W. A. Deepthi, Escobar, Jeffery, Hanigan, Mark D.·2012·The Journal of Nutrition
DOI 10.3945/jn.111.152595
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Abstract

Understanding the regulatory effects of individual amino acids (AA) on milk protein synthesis rates is important for improving protein and AA requirement models for lactation. The objective of this study was to examine the effects of individual essential AA (EAA) on cellular signaling and fractional protein synthesis rates (FSR) in bovine mammary cells. Omission of L-arginine, L-isoleucine, L-leucine, or all EAA reduced (P < 0.05) mammalian target of rapamycin (mTOR; Ser2448) and ribosomal protein S6 (rpS6; Ser235/236) phosphorylation in MAC-T cells. Phosphorylation of mTOR and rpS6 kinase 1 (S6K1; Thr389) decreased (P < 0.05) in the absence of L-isoleucine, L-leucine, or all EAA in lactogenic mammary tissue slices. Omission of L-tryptophan also reduced S6K1 phosphorylation (P = 0.01). Supplementation of L-leucine to media depleted of EAA increased mTOR and rpS6 and decreased eukaryotic elongation factor 2 (Thr56) phosphorylation (P < 0.05) in MAC-T cells. Supplementation of L-isoleucine increased mTOR, S6K1, and rpS6 phosphorylation (P < 0.05). No single EAA considerably affected eukaryotic initiation factor 2-α (eIF2α; Ser51) phosphorylation, but phosphorylation was reduced in response to provision of all EAA (P < 0.04). FSR declined when L-isoleucine (P = 0.01), L-leucine (P = 0.01), L-methionine (P = 0.02), or L-threonine (P = 0.07) was depleted in media and was positively correlated (R = 0.64, P < 0.01) with phosphorylation of mTOR and negatively correlated (R = -0.42, P = 0.01) with phosphorylation of eIF2α. Such regulation of protein synthesis will result in variable efficiency of transfer of absorbed EAA to milk protein and is incompatible with the assumption that a single nutrient limits protein synthesis that is encoded in current diet formulation strategies.

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  • Isoleucine acts as an intermediate to drive muscle protein synthesis and reduce the rate of protein breakdown.

    “Similar to leucine and valine, isoleucine acts as an intermediate to drive muscle protein synthesis and reduce the rate of protein breakdown [27].”

    From Nutraceuticals in the Prevention and Treatment of the Muscle Atrophy (2021) · cites this paper as [27]

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Research works printed but not linked: 2

  1. Sprengel C. Von den substanzen der ackerkrume und des untergrundes (About the substances in the plow layer and the subsoil). Journal fu ¨r Technische und O ¨konomische Chemie. 1828;3:42-99.
  2. NRC. Nutrient requirements of dairy cattle. 7 ed. Washington, DC: National Academy Press; 2001.

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Authors
Appuhamy, J. A. D. R. N., Knoebel, N. A., Nayananjalie, W. A. D., Escobar, J., & Hanigan, M. D.
Affiliations
Virginia Tech (US)
Corresponding author
Hanigan, Mark D.
ORCID
Venue
The Journal of Nutrition
Publisher
Elsevier BV
Published
2012-03
Volume
142
Issue
3
Pages
484-491
ISSN
0022-3166 (ISSN-L)
DOI
10.3945/jn.111.152595
OpenAlex
W2129260297
Cited by
222
References
43
Citations by year
2026: 9 · 2025: 14 · 2024: 19 · 2023: 18 · 2022: 18 · 2021: 16 · 2020: 20 · 2019: 24 · 2018: 23 · 2017: 17 · 2016: 13 · 2015: 6 · 2014: 8 · 2013: 11 · 2012: 6
FWCI
4.70
Type
journal article
Language
en
Open access
Licence
Locations
  • Journal of Nutrition (publishedVersion)
  • PubMed (publishedVersion)
Funders
U.S. Department of Agriculture (NC-1040)
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Cell Biology › Muscle metabolism and nutrition
  • Life Sciences › Agricultural and Biological Sciences › Agronomy and Crop Science › Ruminant Nutrition and Digestive Physiology
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › RNA and protein synthesis mechanisms
Keywords
isoleucine, leucine, mTOR signaling, protein synthesis, mammary epithelial cells, MAC-T cells, bovine mammary tissue, essential amino acids, fractional protein synthesis rate, ribosomal protein S6, S6K1, eIF2α, elongation factor 2, lactation, milk protein synthesis, amino acid requirements, tryptophan, methionine
MeSH terms
Amino Acids, Essential, Animals, Animal Nutritional Physiological Phenomena, Cattle, Cell Line, Female, Isoleucine, Lactation, Leucine, Mammary Glands, Animal, Milk Proteins, Nutritional Requirements, Phosphorylation, Signal Transduction, Eukaryotic Initiation Factor-2, Dietary Supplements, TOR Serine-Threonine Kinases

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