Measuring Protein Turnover in the Field: Implications for Military Research

Abstract

Protein turnover reflects the continual synthesis and breakdown of body proteins, and can be measured at a whole-body (i.e. aggregated across all body proteins) or tissue (e.g. skeletal muscle only) level using stable isotope methods. Evaluating protein turnover in free-living environments, such as military training, can help inform protein requirements. We undertook a narrative review of published literature with the aim of reviewing the suitability of, and advancements in, stable isotope methods for measuring protein turnover in field research. The 2 primary approaches for measuring protein turnover are based on precursor- and end-product methods. The precursor method is the gold-standard for measuring acute (over several hours) skeletal muscle protein turnover, whereas the end-product method measures chronic (over several weeks) skeletal muscle protein turnover and provides the opportunity to monitor free-living activities. Both methods require invasive procedures such as the infusion of amino acid tracers and muscle biopsies to assess the uptake of the tracer into tissue. However, the end-product method can also be used to measure acute (over 9–24 h) whole-body protein turnover noninvasively by ingesting 15N-glycine, or equivalent isotope tracers, and collecting urine samples. The end-product method using 15N-glycine is a practical method for measuring whole-body protein turnover in the field over short (24 h) time frames and has been used effectively in recent military field research. Application of this method may improve our understanding of protein kinetics during conditions of high physiological stress in free-living environments such as military training.

Pre-sleep protein supplementation does not improve performance, body composition, and recovery in British Army recruits (part 1)

“…There was no group interactions for energy expenditure at week 6 (F [3,65] = 0.829, p = 0.483, ƞ p 2 = 0.037) or week 12 (F[3,65] = 0.912, p = 0.440, ƞ p 2 = 0.040; Table 3).…”

“…For example, nitrogen balance can underestimate the amount of protein needed to maintain a positive urinary nitrogen balance by underestimating nitrogen losses ( 63–65 ). Furthermore, the nitrogen balance method does not estimate whole-body protein synthesis compared to more sophisticated methods such as the amino acid oxidation method or the use of an oral tracer (i.e., N-glycine) ( 65 ). Nevertheless, for the purpose of this study, nitrogen balance methodology was able to demonstrate chronic changes in whole-body protein balance ( 26 ).…”

Nutrición animal: Texto de formación universitaria

“…El cuerpo animal está formado por miles de proteínas diferentes, cada una con una función específica, tales como componentes estructurales de las células y tejidos, así como enzimas, hormonas y proteínas activas secretadas por las células inmunitarias, proteínas secretadas por la glándula mamaria. Las proteínas corporales están en continua síntesis y degradación a lo largo de la vida, proceso conocido como recambio proteico, para lo cual se requiere un suministro continuo de aminoácidos (Hinde et al, 2021). Algunos aminoácidos pueden reciclarse a partir de la descomposición de proteínas corporales viejas; sin embargo, el proceso es imperfecto, por lo que necesariamente se requiere consumir proteína en la dieta para abastecer la demanda de aminoácidos del organismo, a fin de lograr ganancia y preservar la masa muscular (Wirth et al, 2020).…”

Comprehensive assessment of post-prandial protein handling by the application of intrinsically labelled protein in vivo in human subjects

“…protein synthesis and oxidation). Stable isotope-labelled amino acid methodologies are commonly applied to assess the individual aspects of protein metabolism in vivo in human subjects (10)(11)(12)(13)(14) . For example, the infusion of stable isotope-labelled amino acids is commonly applied to assess basal, post-absorptive or post-prandial muscle protein synthesis rates.…”