Model to assess muscle protein turnover: Domain of validity using amino acyl-tRNA vs. surrogate measures of precursor pool

Gianna Toffolo, Robert Albright, Michael Joseph Joyner, Niki Dietz, Claudio Cobelli, K Sreekumaran Nair

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

Current models to measure protein turnover across muscle bed are based on many surrogate measures of amino acyl-tRNA. We measured muscle protein turnover based on tracer-to-tracee ratios of the stable isotopes of leucine, phenylalanine, and ketoisocaproate (KIC) in artery and vein and muscle amino acyl-tRNA and muscle tissue fluid (TF) in 26 healthy subjects. A three-compartment model calculation based on arteriovenous and tRNA measurements was first performed and its domain of validity assessed. The results were then compared with those using simpler approaches based on surrogate measures of tRNA such as those of TF and KIC and a one-compartment model based on arteriovenous amino acids. In 96% of cases, the model using tRNA was applicable, but only in a lower percentage of cases were the results using surrogate measures applicable. Protein breakdown, protein synthesis, and shunting of amino acids from artery to vein were consistently underestimated, and fluxes of amino acid from artery to intracellular compartment and from intracellular compartment to vein were overestimated, when surrogate measures were used. The one-compartment model also underestimated protein breakdown and synthesis. Measurements using tissue fluid gave results closer to those based on tRNA. In conclusion, a three-compartment model using arteriovenous samples and amino acyl-tRNA provides measurements of muscle protein turnover of acceptable precision in 96% of cases. The precision was unacceptable in a substantial percentage of cases, and the accuracy of the estimation of protein fluxes was significantly affected when surrogate measures were used.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Endocrinology and Metabolism
Volume285
Issue number5 48-5
StatePublished - Nov 2003

Fingerprint

RNA, Transfer, Amino Acyl
Muscle Proteins
Transfer RNA
Veins
Arteries
Muscle
Proteins
Amino Acids
Muscles
Tissue
Fluids
Fluxes
Phenylalanine
Leucine
Isotopes
Healthy Volunteers
Protein Domains

Keywords

  • Leucine
  • Modeling
  • Muscle protein turnover
  • Phenylalanine

ASJC Scopus subject areas

  • Physiology
  • Endocrinology
  • Biochemistry

Cite this

Model to assess muscle protein turnover : Domain of validity using amino acyl-tRNA vs. surrogate measures of precursor pool. / Toffolo, Gianna; Albright, Robert; Joyner, Michael Joseph; Dietz, Niki; Cobelli, Claudio; Nair, K Sreekumaran.

In: American Journal of Physiology - Endocrinology and Metabolism, Vol. 285, No. 5 48-5, 11.2003.

Research output: Contribution to journalArticle

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