ORIGINAL RESEARCH article
Front. Sports Act. Living
Sec. Exercise Physiology
Volume 7 - 2025 | doi: 10.3389/fspor.2025.1600714
This article is part of the Research TopicEmerging technologies in sports performance: data acquisition and analysisView all 9 articles
Proof-of-concept of a prior validated LC-MS/MS method for detection of N-Lactoyl-Phenylalanine in dried blood spots before, during and after a performance diagnostic test of junior squad triathletes
Provisionally accepted
- German Sport University Cologne, Cologne, Germany
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N-lactoyl-phenylalanine (lac-phe) is an exercise-inducible metabolite that is discussed for suppressing appetite. As no point-of-care lac-phe analysis for frequent sample collection during exercise exists, the objectives of this study were (1) to develop and validate a method for quantifying lac-phe by liquid chromatography tandem mass spectrometry (LC-MS/MS) using 20 µl of capillary blood collected on cellulose-based dried blood spot (dbs) cards (QIAcard® FTA® DMPK-C) and (2) to determine lac-phe dbs concentrations before, during, and after a combined running and cycling performance test protocol in regional junior squad triathletes for proof-of-concept. The validated method (precision < 8 %, accuracy < 7 % in a working range of 0-100 ng/mL, stability > 28 days at -20 °C and 20 °C) was successfully applied in a combined running and cycling performance diagnostic test. Dbs samples were collected by trained researchers at multiple time points – before, during, and after the performance diagnostic test - from 15 female and male junior squad triathletes on two test occasions separated by 3 months and a training period. Lac-phe concentrations increased from 31.5±10 nmol/L at baseline to a maximum of 101.0±40.1 nmol/L at time-to-exhaustion after the second incremental test. 15 min after exercise, lac-phe concentration decreased to 89.7±30.4 nmol/L. No statistical difference between the two test occasions was seen. Sex-specific differences were observed, with female subjects showing significantly higher lac-phe concentrations than male subjects (p < 0.05) at time-to-exhaustion after the first incremental test and at the onset of the second incremental test. No statistically significant correlations were identified between lac-phe and lactate, glucose as well as anthropometric and respiratory parameters. This study introduces a robust method that, for the first time, enables the quantification of lac-phe concentrations not only before and after, but also during a performance test. By applying this approach, it contributes novel insights into the temporal dynamics of exercise-induced alterations in lac-phe concentrations in humans.
Keywords: N-Lactoyl-Phenylalanine1, Appetite2, metabolomics3, Dried Blood Spots4, RED-S5, biomarker6, Athletes7, Endurance Exercise8
Received: 26 Mar 2025; Accepted: 02 Sep 2025.
Copyright: © 2025 Bauhaus, Moeller, Keller, Thomas, Braun, Wahl and Thevis. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Mario Thevis, German Sport University Cologne, Cologne, Germany
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