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Model to assess muscle protein turnover: domain of validity using amino acyl-tRNA vs. surrogate measures of precursor pool.
Am J Physiol Endocrinol Metab 2003; 285(5):E1142-9AJ

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.

Authors+Show Affiliations

Department of Information Engineering, University of Padova, Italy.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Comparative Study
Journal Article
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

14534080

Citation

Toffolo, Gianna, et al. "Model to Assess Muscle Protein Turnover: Domain of Validity Using Amino acyl-tRNA Vs. Surrogate Measures of Precursor Pool." American Journal of Physiology. Endocrinology and Metabolism, vol. 285, no. 5, 2003, pp. E1142-9.
Toffolo G, Albright R, Joyner M, et al. Model to assess muscle protein turnover: domain of validity using amino acyl-tRNA vs. surrogate measures of precursor pool. Am J Physiol Endocrinol Metab. 2003;285(5):E1142-9.
Toffolo, G., Albright, R., Joyner, M., Dietz, N., Cobelli, C., & Nair, K. S. (2003). Model to assess muscle protein turnover: domain of validity using amino acyl-tRNA vs. surrogate measures of precursor pool. American Journal of Physiology. Endocrinology and Metabolism, 285(5), pp. E1142-9.
Toffolo G, et al. Model to Assess Muscle Protein Turnover: Domain of Validity Using Amino acyl-tRNA Vs. Surrogate Measures of Precursor Pool. Am J Physiol Endocrinol Metab. 2003;285(5):E1142-9. PubMed PMID: 14534080.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Model to assess muscle protein turnover: domain of validity using amino acyl-tRNA vs. surrogate measures of precursor pool. AU - Toffolo,Gianna, AU - Albright,Robert, AU - Joyner,Michael, AU - Dietz,Niki, AU - Cobelli,Claudio, AU - Nair,K Sreekumaran, PY - 2003/10/10/pubmed PY - 2003/12/3/medline PY - 2003/10/10/entrez SP - E1142 EP - 9 JF - American journal of physiology. Endocrinology and metabolism JO - Am. J. Physiol. Endocrinol. Metab. VL - 285 IS - 5 N2 - 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. SN - 0193-1849 UR - https://www.unboundmedicine.com/medline/citation/14534080/Model_to_assess_muscle_protein_turnover:_domain_of_validity_using_amino_acyl_tRNA_vs__surrogate_measures_of_precursor_pool_ L2 - http://www.physiology.org/doi/full/10.1152/ajpendo.00106.2003?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub=pubmed DB - PRIME DP - Unbound Medicine ER -