Amino Acid and Whole Body/Muscle Protein Turnover

Metabolic Solutions offers project design assistance and a mass spectrometry service to help researchers to study amino acid metabolism and whole body and muscle protein turnover using stable isotope methods.

List of Amino Acid Metabolism Services

  • Amino acid kinetics
  • Amino acid oxidation to carbon dioxide
  • Transamination
  • Metabolic fate of dietary amino acids
  • Extracellular intermediates

Amino Acid Metabolism

The quantitation of amino acid metabolism in human subjects can be achieved with stable isotope tracers. Historically, protein and amino acid nutrition was based on the nitrogen (N) balance technique. However, further research showed that a major portion of body protein is continuously degraded and resynthesized, but remains in N balance. Stable isotope techniques can dissect the relative contributions of protein synthesis and degradation in relation to body N balance. Furthermore, stable labeled amino acid tracers can be utilized to determine how amino acid metabolism is affected by various nutritional and non-nutritional factors.


The following examples offer useful protocols for studying aspects of amino acid metabolism and kinetics.

Amino Acid OxidationBranched-chain amino acids as fuels
Amino Acid RequirementsTotal sulfur amino acid requirements in young men
Protein TurnoverAge attenuates leucine oxidation after eccentric exercise

If you need protocol information on how to conduct amino metabolism tracer studies, the following technical paper is available: Amino Acid Isotope Tracer Studies.

Protein Turnover

Tracer methods using isotopically-labeled compounds are ideal to explore dynamic aspects of protein metabolism in the whole organism. The infusion of a tracer is coupled with the measurement of end products of nitrogen metabolism (Picou and Taylor-Roberts Model) or with the determination of the enrichment of isotope (15N or 13C) in plasma following administration of a labeled amino acid (Waterlow Model). When this latter approach is combined with measurements of 13C in expired carbon dioxide or 15N in urinary urea or ammonia, the components of whole body amino acid flux and whole body protein synthesis and catabolism can be determined.

Muscle Protein Turnover

Metabolic Solutions can determine muscle protein turnover using a deuterium oxide labeling method. Oral doses of deuterium oxide are administered to subjects. The alpha-hydrogen of alanine of protein is labeled during metabolism with alanine transaminase. Previs et al. (Am J Physiol 286:E665-E672, 2004) have demonstrated that deuterium oxide administration can be used to quantitate muscle protein synthetic rates in humans.

List of Protein Turnover Services

  • Whole body protein synthesis/breakdown assessment
  • Flooding dose turnover techniques
  • Muscle protein synthesis
  • Lipoprotein synthesis and kinetics
  • Deuterium oxide labeling studies

If you need protocol information on how to conduct whole body protein turnover tracer studies, the following technical paper is available: Protein Turnover Tracer Studies.

Published Amino Acid and Protein Turnover Studies Analyzed By Metabolic Solutions

  1. Pasiakos SM, Margolis LM, McClung JP, Cao JJ, Whigham LD, Combs GF, and Young AJ. Whole-body protein turnover response to short-term high-protein diets during weight loss: a randomized controlled trial. Int J Obes Epub ahead of print, Oct 29, 2013.“Whole-body protein turnover responses to high-protein diets during weight loss were investigated using 1-13C-leucine infusion.”
  2. Wagner AL, Urschel KL, Betancourt A, Adams AA, and Horohov DW. Effects of advanced age on whole-body protein synthesis and skeletal muscle mechanistic target of rapamycin signaling in horses.“Whole-body protein synthesis was measured with a 4-hour primed constant infusion of 1-13C-phenylalanine in horses. After the infusions, a gluteus medius muscle biopsy was collected for determination of muscle protein synthesis rates.”
  3. Yang Y, Breen L, Burd NA, Hector AJ, Churchward-Venne TA, Josse AR, Tarnopolsky MA, and Phillips SM. Resistance exercise enhances myofibrillar protein synthesis with graded intakes of whey protein in older men. Br J Nutr. 108(10):1780-8, 2012.“Infusion of 1-13C-leucine and ring-13C6-phenylalanine and collection of muscle biopsies were used to ascertain whole-body leucine oxidation and muscle protein synthesis.”
  4. Niemczyk S, Sikorska H, Wiecek A, Zukowska-Szczechowska E, Zalecka K, Gorczynska J, Kubik M, Czerwienska B, Gosek K, Veldhuis JD, Wagner DA, Gaudreau P, Hakonen T, Kay SW, Jouhikainen T, and Schaefer F. A super-agonist of growth hormone-releasing hormone causes rapid improvement of nutritional status in patients with chronic kidney disease. Kidney Int. 77(5):450-8, 2009.
    “In this study, a new GH-releasing hormone super-agonist (AKL-0707) was evaluated for improved anabolism and nutritional status of nondialyzed patients with stage 4-5 chronic kidney disease.”
  5. Mehrotra R, Bross R, Wang H, Appell M, Tso L, and Kopple JD. Effect of high-normal compared with low-normal arterial pH on protein balances in automated peritoneal dialysis patients. Am J Clin Nutr. 90(6):1532-40, 2009.
    “Tested the hypothesis that in peritoneal dialysis patients with an arterial pH of 7.43-7.45 are associated with more-positive nitrogen balance. Used a primed, continuous infusion of 1-13C-leucine to determine leucine flux and whole-body protein turnover.”
  6. Miller SL, Gaine PC, Maresh CM, Armstrong LE, Ebbeling CB, Lamont LS, and Rodriguez NR. The effects of nutritional supplementation throughout an endurance run on leucine kinetics during recovery.“Determined the effect of nutritional supplementation on whole body leucine kinetics using a primed, continuous infusion of 1-13C-leucine.”