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Tryptophan in Nutrition and Health 2.0

Department of Physiology, Johann-Friedrich-Blumenbach-Institute for Zoology and Anthropology, Faculty of Biology Georg August University Göttingen, Göttingen and Goettingen Research Campus, Am Türmchen 3, D-33332 Gütersloh, Germany
Indian Scientific Education and Technology Foundation, Lucknow 226002, India
Department of Neurobiology, Medical University of South Carolina, 173 Ashley Avenue, BSB 403, Charleston, SC 29425, USA
Department of Neurology, University of Texas Medical Branch, 301 University Boulevard, Galveston, TX 77555, USA
Author to whom correspondence should be addressed.
Int. J. Mol. Sci. 2023, 24(8), 7112;
Received: 21 March 2023 / Revised: 6 April 2023 / Accepted: 7 April 2023 / Published: 12 April 2023
(This article belongs to the Special Issue Tryptophan in Nutrition and Health 2.0)
This editorial summarizes the eight articles that have been collected for the Special Issue entitled “Tryptophan in Nutrition and Health 2.0,” and demonstrates their relevance to the field. Tryptophan is a rate-limiting essential amino acid, the metabolites of which are important endogenous molecular mediators of physiology and pathophysiology (Figure 1).
Tryptophan deficiency manifests itself rapidly under stress, inflammation, and catabolic conditions [1]. Modulation of the tryptophan metabolism can prevent age-related diseases, including cognitive and physical decline [1,2]. Endogenous metabolites, such as indole-3-propionic acid, can act as potent protective agents [2]. The kynurenine-to-tryptophan ratio constitutes a novel relevant biomarker for assessing organism and ecosystem health [3]. UVB enhances the antiproliferative activity of kynurenine and kynurenic acid in melanoma cells [4]. The measurement of altered metabolites in melanoma patients can be used to improve diagnosis and treatment assessment [5]. The neuroprotective tryptophan derivative melatonin can determine the brain–heart crosstalk [6]. New data suggest a modulatory role of serotonin biosynthesis in the reprogramming of somatic cells to a pluripotent state [7]. Activation of the kynurenine and indolamine pathways of the tryptophan metabolism is linked to a plethora of neuropsychiatric disorders [8]. Transcranial magnetic stimulation can elevate brain serotonin levels, thereby restoring normal neurotransmission. The tryptophan metabolism can be influenced to prevent and reverse premature aging characterized by inflammation and oxidative stress [1,2]. Targeting tryptophan and the tryptophan pathway can enable novel strategies for diagnosis, prevention, treatment, and rehabilitation to improve, maintain, and restore health [1,2,3,4,5,6,7,8].

Author Contributions

B.P. wrote the original draft of the manuscript. S.K.S., K.S. and M.A.P. reviewed the manuscript and edited the original draft. S.K.S. contributed to the writing of the manuscript and supported the corresponding author and editor, B.P., in focusing on the final tryptophan metabolites that are the topic of this Special Issue. K.S. performed related research in collaboration with the corresponding author and editor, B.P., and contributed to the writing of the manuscript. M.A.P. performed related research in collaboration with the corresponding author and editor, B.P., and contributed to the writing of the manuscript. All authors have read and agreed to the published version of the manuscript.


This research received no external funding.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Not applicable.


Burkhard Poeggeler wishes to thank the coauthors for reviewing and expanding on this editorial. All authors have read and agreed to the published version of the manuscript. As a Guest Editor, Burkhard Poeggeler values the efforts and contributions of all authors. The support of the reviewers was critical in determining which manuscripts were selected for publication.

Conflicts of Interest

The authors declare no conflict of interest.


  1. Kanova, M.; Kohout, P. Tryptophan: A unique role in the critically ill. Int. J. Mol. Sci. 2021, 22, 11714. [Google Scholar] [CrossRef] [PubMed]
  2. Konopelski, P.; Mogilnicka, I. Biological Effects of Indole-3-Propionic Acid, a Gut Microbiota-Derived Metabolite, and Its Precursor Tryptophan in Mammals’ Health and Disease. Int. J. Mol. Sci. 2022, 23, 1222. [Google Scholar] [CrossRef] [PubMed]
  3. Jamshed, L.; Debnath, A.; Jamshed, S.; Wish, J.V.; Raine, J.C.; Tomy, G.T.; Thomas, P.J.; Holloway, A.C. An emerging cross-species marker for organismal health: Tryptophan-kynurenine pathway. Int. J. Mol. Sci. 2022, 23, 6300. [Google Scholar] [CrossRef] [PubMed]
  4. Walczak, K.; Kazimierczak, P.; Szalast, K.; Plech, T. UVB radiation and selected tryptophan-derived AhR ligands—Potential biological interactions in melanoma cells. Int. J. Mol. Sci. 2021, 22, 7500. [Google Scholar] [CrossRef] [PubMed]
  5. Hubková, B.; Valko-Rokytovská, M.; Čižmárová, B.; Zábavníková, M.; Mareková, M.; Birková, A. Tryptophan: Its metabolism along the kynurenine, serotonin, and indole pathway in malignant melanoma. Int. J. Mol. Sci. 2022, 23, 9160. [Google Scholar] [CrossRef] [PubMed]
  6. Bekała, A.; Płotek, W.; Siwicka-Gieroba, D.; Sołek-Pastuszka, J.; Bohatyrewicz, R.; Biernawska, J.; Kotfis, K.; Bielacz, M.; Jaroszyński, A.; Dabrowski, W. Melatonin and the brain–heart crosstalk in neurocritically ill patients—From molecular action to clinical practice. Int. J. Mol. Sci. 2022, 23, 7094. [Google Scholar] [CrossRef] [PubMed]
  7. Sinenko, S.A.; Kuzmin, A.A.; Skvortsova, E.V.; Ponomartsev, S.V.; Efimova, E.V.; Bader, M.; Alenina, N.; Tomilin, A.N. Tryptophan hydroxylase-2-mediated serotonin biosynthesis suppresses cell reprogramming into pluripotent state. Int. J. Mol. Sci. 2023, 24, 4862. [Google Scholar] [CrossRef] [PubMed]
  8. Giron, C.G.; Lin, T.T.Z.; Rebecca, L.D.; Kan, R.L.D.; Zhang, B.B.B.; Yau, S.Y.; Kranz, G.S. Non-invasive brain stimulation effects on biomarkers of tryptophan metabolism: A scoping review and meta-analysis. Int. J. Mol. Sci. 2022, 23, 9692. [Google Scholar] [CrossRef] [PubMed]
Figure 1. Three tryptophan pathways leading to endogenous indolamines, kynurenines and indoles.
Figure 1. Three tryptophan pathways leading to endogenous indolamines, kynurenines and indoles.
Ijms 24 07112 g001
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MDPI and ACS Style

Poeggeler, B.; Singh, S.K.; Sambamurti, K.; Pappolla, M.A. Tryptophan in Nutrition and Health 2.0. Int. J. Mol. Sci. 2023, 24, 7112.

AMA Style

Poeggeler B, Singh SK, Sambamurti K, Pappolla MA. Tryptophan in Nutrition and Health 2.0. International Journal of Molecular Sciences. 2023; 24(8):7112.

Chicago/Turabian Style

Poeggeler, Burkhard, Sandeep Kumar Singh, Kumar Sambamurti, and Miguel Angelo Pappolla. 2023. "Tryptophan in Nutrition and Health 2.0" International Journal of Molecular Sciences 24, no. 8: 7112.

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