Quantifying the contribution of dietary protein to whole body protein kinetics: examination of the intrinsically-labeled proteins method.

Quantifying the contribution of dietary protein to whole body protein kinetics: examination of the intrinsically-labeled proteins method. Am J Physiol Endocrinol Metab. 2019 Apr 02;: Authors: Wolfe RR, Park S, Kim IY, Starck C, Marquis BJ, Ferrando AA, Moughan PJ Abstract Intrinsically-labeled dietary proteins have been used to trace various aspects of digestion and absorption, including quantifying the contribution of dietary protein to observed post-prandial amino acid and protein kinetics in human subjects. Quantification of the rate of appearance in peripheral blood of an unlabeled (tracee) amino acid originating from an intrinsically-labeled protein (exogenous Ra) requires the assumption that there is no dilution of the isotope enrichment of the protein-bound amino acid in the gastrointestinal tract (GIT) or across the splanchnic bed. It must also be assumed that the effective volume of distribution (pV) into which the tracer and tracee appear can be reasonably estimated by a single value, and that any recycling of the tracer is minimal and thus does not affect calculated rates. We have assessed these assumptions quantitatively using values from published studies. We conclude that the use of intrinsically-labeled proteins as currently described to quantify exogenous Ra systematically underestimates the true value. When used with the tracer-determined rates of amino acid kinetics, underestimation of exogenous Ra from the intrinsi...
Source: American Journal of Physiology. Endocrinology and Metabolism - Category: Physiology Authors: Tags: Am J Physiol Endocrinol Metab Source Type: research