Page 60 - ITPS-6-2

INNOSC Theranostics

and Pharmacological Sciences

COMMENTARY
Tryptophan metabolism in schizophrenia

2
Dilceu Silveira Tolentino Júnior *, Heberson Teixeira da Silva ,
1
Alessandro Martins Ribeiro , Tales Alexandre Ferreira-Aversi , and
2
1
Lízia Colares Vilela 1
1 Federal University of the Jequitinhonha and Mucuri Valley, Teófilo Otoni, Minas Gerais, Brazil
2 Department of Physics, Federal University of Alfenas, Alfenas, Minas Gerais, Brazil

This commentary aims to emphasize the molecular mechanisms involved in the
pathophysiology of schizophrenia and in the onset of the disease addressed in an article
recently published by Carvalho et al. In addition, it is necessary to gather recent
[1]
and updated information on the role of tryptophan and its metabolites, emphasizing
the relationship of this amino acid and its metabolites in the pathophysiology of
schizophrenia, with a focus on the kynurenine pathway and, above all, its possible
[2]
associations with the mental illnesses .
Carvalho et al. reported that when tryptophan crosses the blood–brain barrier, its
metabolites exert different actions on the central nervous system (CNS) . Important
[1]
neuroactive metabolites resulting from tryptophan metabolism, including serotonin,
melatonin, 3-hydroxykynurenine (3-HK), quinolinic, and kynurenic acid (KYNA), have
been associated with neuropsychiatric diseases such as schizophrenia .
[2]
Schizophrenia is a disorder that shows a functional imbalance of the dopaminergic
system, causing cognitive and emotional functions to be altered due to changes in the
*Corresponding author: dopaminergic response. These changes can be divided into two subgroups of symptoms:
[3]
Dilceu Silveira Tolentino Júnior positive and negative . Positive symptoms, such as delusions, hallucinations, psychoses,
(dilceujunior@bol.com.br) paranoia, disordered thinking, and disorganized speech, occur as a result of dopaminergic
Citation: Júnior DST, hyperactivity in the mesolimbic area. Negative symptoms, such as demotivation, violent
da Silva HT, Ribeiro AM, et al., emotional behavior, social isolation, cognitive impairment, and slow speech, occur due
(2023), Tryptophan metabolism [3]
in schizophrenia. INNOSC to dopaminergic hypoactivity in prefrontal cortex projections .
Theranostics and Pharmacological Tryptophan is an essential amino acid that is not synthesized by the body and,
Sciences, 6(2): 0435.
https://doi.org/10.36922/itps.0435 therefore, needs to be obtained from the diet; it is present in the vast majority of foods.
About 90% of ingested tryptophan is bound to plasma albumin and only 10% is found
Received: April 13, 2023
in free form in the bloodstream . Non-esterified fatty acids are essential for the balance
[4]
Accepted: July 19, 2023 between the tryptophan in free form and the tryptophan bound to albumin, as they
Published Online: August 4, 2023 compete with this amino acid for binding to plasma albumin, consequently increasing
the level of free tryptophan in plasma .
[5]
Copyright: © 2023 Author(s).
This is an Open-Access article This acid amine is a substrate for the production of several neuroactive molecules
distributed under the terms of the
Creative Commons Attribution with biological activities, such as serotonin (5-hydroxytryptamine [5-HT]), melatonin,
License, permitting distribution, 3-HK, quinolinic acid (QA), and KYNA, among others . The two main known pathways
[6]
and reproduction in any medium, of tryptophan metabolism are 5-HT and kynurenine. About 95% of tryptophan obtained
provided the original work is
properly cited. from the diet is metabolized through the kynurenine pathway, and only about 1% of
tryptophan is converted to 5-HT in the CNS, while the rest is converted to proteins and
Publisher’s Note: AccScience
[6]
Publishing remains neutral with melanin .
regard to jurisdictional claims in
published maps and institutional As shown in Figure 1, tryptophan is a substrate for the synthesis of
affiliations. 5-hydroxytryptamine, also known as serotonin (5-HT), in the CNS. Tryptophan
Volume 6 Issue 2 (2023) 1 https://doi.org/10.36922/itps.0435