A novel triple-tracer approach to assess postprandial protein turnover

Antoinette Moran, Gianna Toffolo, Michele Schiavon, Adrian Vella, Katherine Klaus, Claudio Cobelli, K. Sreekumaran Nair

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


Insulin and nutrients have profound effects on proteome homeostasis. Currently no reliable methods are available to measure postprandial protein turnover. A triple-tracer method was developed using phenylalanine stable isotope tracers to estimate appearance rates of ingested (Ra meal) and endogenous phenylalanine and the rate of phenylalanine disposal (Rd). This was compared with the “traditional” dual-tracer method, using one (1-CM)-and two (2-CM)-compartment models. For both methods, [13C6]phenylalanine was given orally, and [15N]phenylalanine was constantly infused; the triple-tracer method added [2H5]phenylalanine, infused at rates to mimic meal [13C6]phenylalanine appearance. Additionally, incorporation of meal-derived phenylalanine into specific proteins was measured after purification by two-dimensional electrophoresis. The triple-tracer approach reduced modeling errors, allowing improved reconstruction of Ra meal with a tracer-to-tracee ratio that was more constant and better estimated Rd. The 2-CM better described phenylalanine kinetics and Rd than 1-CM. Thus, the triple-tracer approach using 2-CM is superior for measuring non-steady-state postprandial protein turnover. This novel approach also allows measurement of postprandial synthesis rates of specific plasma proteins. We offer a valid non-steady-state model to measure postprandial protein turnover and synthesis of plasma proteins that can safely be applied in adults, children, and pregnant women.

Original languageEnglish (US)
Pages (from-to)E469-E477
JournalAmerican Journal of Physiology - Endocrinology and Metabolism
Issue number4
StatePublished - Oct 2018

Bibliographical note

Funding Information:
This project was supported by NIH Grant R01-DK-101402 (A. Moran), a grant from the Cystic Fibrosis Foundation, and the National Center for Advancing Translational Sciences of the NIH Award No. UL1-TR-000114 (University of Minnesota) and UL1-TR-000135 and U24-DK-100469 (Mayo Clinic).

Publisher Copyright:
© 2018 American Physiological Society. All rights reserved.


  • Protein catabolism
  • Protein turnover
  • Stable isotopes


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