Internal comparison between deuterium oxide (D2O) and L‐[ring‐13C6] phenylalanine for acute measurement of muscle protein synthesis in humans

• Published in: Physiological reports Vol. 3; no. 7; pp. e12433 - n/a
• Main Authors: Wilkinson, Daniel J., Cegielski, Jessica, Phillips, Bethan E., Boereboom, Catherine, Lund, Jonathan N., Atherton, Philip J., Smith, Kenneth
• Format: Journal Article
• Language: English
• Published: United States John Wiley & Sons, Inc 01.07.2015; John Wiley & Sons, Ltd
• Subjects: Amino acids; Deuterium oxide; metabolism; muscle protein synthesis; Oral administration; Original Research; Phenylalanine; Physiology; Protein biosynthesis; Protein synthesis; Pyrolysis; stable isotope tracers; Tracers; muscle protein synthesis; metabolism; Deuterium oxide; stable isotope tracers
• ISSN: 2051-817X; 2051-817X
• DOI: 10.14814/phy2.12433

Stable isotope tracer methodologies are becoming increasingly widespread in metabolic research; yet a number of factors restrict their implementation, such as, i.v infusions, multiple cannulae, tissue samples, and significant cost. We recently validated the sensitivity of the orally administered stable isotope tracer deuterium oxide (D2O) for quantifying day‐to‐day changes in muscle protein synthesis (MPS). This method is less invasive, restrictive, and more cost‐effective than traditional amino acid (AA) tracer techniques. In the present study, we hypothesized the sensitivity of our analytical techniques (GC‐Pyrolysis‐IRMS) would permit D2O‐derived measurements of MPS over much shorter periods (i.e., hours) usually only possible using AA‐tracer techniques. We recruited nine males (24 ± 3 year, BMI: 25 ± 3 kg·m−²) into an internally controlled comparison of D2O versus 13C AA‐tracers. The day before the acute study subjects consumed 400 mL D2O, and on the study day, received a primed (0.3 mg·kg−1) continuous (0.6 mg·kg·h−1) i.v infusion of L‐[ring‐13C6]‐phenylalanine to quantify MPS under both: (1) basal [postabsorptive] and; (2) stimulated [postprandial] that is, consumption of 20 g EAA, conditions. Measures of MPS yielded indistinguishable technique differences with respect to EAA, 13C: 0.065 ± 0.004 to 0.089 ± 0.006%·h−1 (P < 0.05) and D2O: 0.050 ± 0.007 to 0.088 ± 0.008%·h−1 (P < 0.05) with qualitatively similar increases. Our findings reveal that acute measurement of MPS, usually only possible using AA‐tracers, are feasible over shorter periods with orally administered D2O when used in tandem with GC‐Pyrolysis‐IRMS. We conclude that this D2O approach provides a less invasive, cost‐effective, and flexible means by which to quantify MPS acutely over several hours. Amino acid stable isotope tracer methodologies are increasingly used in metabolic research for the measurement of muscle protein synthesis (MPS); yet a number of factors restrict their implementation, such as, i.v infusions, multiple cannulae, tissue samples and significant tracer, and pharmacy costs. The orally administered stable isotope tracer deuterium oxide (D2O) has the potential to provide a less invasive, restrictive and more cost‐effective alternative to these traditional amino acid (AA) tracer techniques. In the present study, we performed an internal comparison between L‐[ring‐13C6] phenylalanine and D2O within the same individuals in order to determine whether D2O could provide a robust, simpler, and less burdensome approach, for use in difficult to study clinical populations where repeated invasive sampling and i.v tracer administration may not be desirable. Measures of MPS yielded indistinguishable technique differences with respect to anabolic stimulus (20 g EAA feed), with qualitatively similar increases observed with both tracers. We conclude that using D2O provides an accurate, less invasive, cost‐effective, and flexible means by which to quantify MPS acutely over a few hours.