Regulators of protein metabolism are affected by cyclical nutritional treatments with diets varying in protein and energy content

J Nutr Biochem. 2012 Nov;23(11):1467-73. doi: 10.1016/j.jnutbio.2011.09.009. Epub 2012 Feb 2.


There is evidence that the E3 ubiquitin ligases muscle ring finger-1 (MuRF1) and atrogin-1, which mediate the ubiquitination of certain proteins and thereby their proteolysis, are regulated by cyclical nutritional treatments varying in lysine content. In order to explore further the regulatory mechanisms involved in metabolic adaptation to dietary changes, we investigated the effects of daily variations in energy [2800 (E-) followed by 3200 kcal/kg (E+)], protein [230 (P+) followed by 150g/kg (P-)] or both [E-P+ followed by E+P-] on muscle protein metabolism in 2-week-old male broiler chickens. Growth performance was similar for all treatments. Expression of atrogin-1 and MuRF1 was changed by alternation of diets varying in protein (higher expression with P- vs. P+) and energy content (higher expression with E- vs. E+). The expression of atrogin-1 was regulated with mixed diets (increase in E+P- vs. E-P+) but not that of MuRF1. Such regulation may involve the mammalian target of rapamycin (mTOR), which was more phosphorylated with P+ than with P-. Eukaryotic initiation factor 4E binding protein, p70S6 kinase and ribosomal protein S6, which are mTOR targets known to control protein synthesis, were highly activated by increased protein content (P+ vs. P-). The mechanisms coordinating the protein synthesis/proteolysis balance remain to be characterized.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animal Nutritional Physiological Phenomena*
  • Animals
  • Chickens / metabolism
  • Chickens / physiology*
  • Diet*
  • Dietary Proteins / pharmacology*
  • Energy Intake
  • Eukaryotic Initiation Factor-4E / genetics
  • Male
  • Muscle Proteins / metabolism
  • Muscle, Skeletal / drug effects
  • Muscle, Skeletal / growth & development
  • Muscle, Skeletal / metabolism
  • Phosphorylation
  • Protein Biosynthesis
  • Proteins / metabolism*
  • Ribosomal Protein S6 / genetics
  • Ribosomal Protein S6 Kinases, 90-kDa / genetics
  • SKP Cullin F-Box Protein Ligases / metabolism
  • TOR Serine-Threonine Kinases / metabolism
  • Ubiquitin-Protein Ligases / metabolism


  • Dietary Proteins
  • Eukaryotic Initiation Factor-4E
  • Muscle Proteins
  • Proteins
  • Ribosomal Protein S6
  • SKP Cullin F-Box Protein Ligases
  • Ubiquitin-Protein Ligases
  • Ribosomal Protein S6 Kinases, 90-kDa
  • TOR Serine-Threonine Kinases