Changes of tryptophan metabolism in Japanese runners during an ultra-marathon race
Under the assumption that tryptophan (TRP) metabolism may be modulated by the intensity, duration, and total exercise/energy expenditure of the ultra-marathon, we evaluated the changes in two major TRP metabolic pathway substances [serotonin (5-HT) and kynurenine (KYN)] during a two-day ultra-marathon race.
Blood was sampled at three different time points: before the race (baseline), after running 45 km on the first day, and after running 135 km on the second day.
Serum TRP concentrations decreased in proportion to the distance covered, and the levels after running 135 km were significantly lower than at baseline and after running 45 km. Serum serotonin (5-HT) concentrations increased significantly after running 45 km but reduced towards baseline levels after running 135 km. Serum kynurenine (KYN) concentrations hardly changed after running 45 km but increased significantly after running 135 km compared with after running 45 km values. Serum FFAs levels increased significantly after running 45 km compared with baseline values, and they elevated even further after running 135 km. Serum albumin concentrations reduced significantly after running 45 km but remained at almost the same level after running 135 km. Serum 5-HT levels tended to be consistently correlated to the completion times on the first and second days.
Serum 5-HT concentrations are known to be associated with central fatigue, and may predict exercise performance. KYN levels appeared to reflect the intensity of physical exercise, and its pathway may play a role in reactive oxygen species scavenging systems during a long-duration exercise.
KeywordsExercise intensity Exercise performance Kynurenine Serotonin Tryptophan Ultra-marathon
We thank the volunteer runners for their generous participation in our study together with the chairman and organizing committee of the Maranic race. We also thank Ms. Fujii, T., Ms. Kubo, Y., Ms. Nakanishi, N., Ms. Ito, Y., Ms. Higuchi, K., and Ms. Watanabe, M. for technical assistance.
Compliance with ethical standards
The protocol was approved by the Institutional Review Board of the Nagoya City University Graduate School of Medical Sciences and by the chairman and organizing committee of the race.
Conflict of interest
The authors declare no conflicts of interest that are directly relevant to the content of this article.
All procedures performed in studies involving human participants were in accordance with study approval by the Institutional Review Board of the Nagoya City University Graduate School of Medical Sciences and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
Informed consent in writing was obtained from each subject enrolled in the study.
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