{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,28]],"date-time":"2026-04-28T05:28:58Z","timestamp":1777354138722,"version":"3.51.4"},"reference-count":124,"publisher":"MDPI AG","issue":"15","license":[{"start":{"date-parts":[[2022,7,31]],"date-time":"2022-07-31T00:00:00Z","timestamp":1659225600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"FEDER\u2014Fundo Europeu de Desenvolvimento Regional","award":["IF\/00092\/2014\/CP1255\/CT0004"],"award-info":[{"award-number":["IF\/00092\/2014\/CP1255\/CT0004"]}]},{"name":"FCT\u2014Funda\u00e7\u00e3o para a Ci\u00eancia e a Tecnologia","award":["IF\/00092\/2014\/CP1255\/CT0004"],"award-info":[{"award-number":["IF\/00092\/2014\/CP1255\/CT0004"]}]},{"name":"FCT and FEDER (European Union)","award":["IF\/00092\/2014\/CP1255\/CT0004"],"award-info":[{"award-number":["IF\/00092\/2014\/CP1255\/CT0004"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["IJMS"],"abstract":"<jats:p>Depression is a common and serious disorder, characterized by symptoms like anhedonia, lack of energy, sad mood, low appetite, and sleep disturbances. This disease is very complex and not totally elucidated, in which diverse molecular and biological mechanisms are involved, such as neuroinflammation. There is a high need for the development of new therapies and gaining new insights into this disease is urgent. One important player in depression is the amino acid tryptophan. This amino acid can be metabolized in two important pathways in the context of depression: the serotonin and kynurenine pathways. These metabolic pathways of tryptophan are crucial in several processes that are linked with depression. Indeed, the maintenance of the balance of serotonin and kynurenine pathways is critical for the human physiological homeostasis. Thus, this narrative review aims to explore tryptophan metabolism (particularly in the serotonin and kynurenine pathways) in depression, starting with a global overview about these topics and ending with the focus on these pathways in neuroinflammation, stress, microbiota, and brain-derived neurotrophic factor regulation in this disease. Taken together, this information aims to clarify the metabolism of tryptophan in depression, particularly the serotonin and kynurenine pathways.<\/jats:p>","DOI":"10.3390\/ijms23158493","type":"journal-article","created":{"date-parts":[[2022,8,1]],"date-time":"2022-08-01T02:06:42Z","timestamp":1659319602000},"page":"8493","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":262,"title":["Tryptophan Metabolism in Depression: A Narrative Review with a Focus on Serotonin and Kynurenine Pathways"],"prefix":"10.3390","volume":"23","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-8231-1560","authenticated-orcid":false,"given":"Ana Salom\u00e9","family":"Correia","sequence":"first","affiliation":[{"name":"OncoPharma Research Group, Center for Health Technology and Services Research (CINTESIS), Rua Doutor Pl\u00e1cido da Costa, 4200-450 Porto, Portugal"},{"name":"Institute of Biomedical Sciences Abel Salazar (ICBAS), University of Porto, Rua de Jorge Viterbo Ferreira 228, 4050-313 Porto, Portugal"},{"name":"CINTESIS@RISE, Faculty of Medicine, University of Porto, Alameda Hern\u00e2ni Monteiro, 4200-319 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1283-1042","authenticated-orcid":false,"given":"Nuno","family":"Vale","sequence":"additional","affiliation":[{"name":"OncoPharma Research Group, Center for Health Technology and Services Research (CINTESIS), Rua Doutor Pl\u00e1cido da Costa, 4200-450 Porto, Portugal"},{"name":"CINTESIS@RISE, Faculty of Medicine, University of Porto, Alameda Hern\u00e2ni Monteiro, 4200-319 Porto, Portugal"},{"name":"Department of Community Medicine, Health Information and Decision (MEDCIDS), Faculty of Medicine, University of Porto, Rua Doutor Pl\u00e1cido da Costa, 4200-450 Porto, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2022,7,31]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"2529","DOI":"10.1001\/jama.2018.17824","article-title":"The Challenges of Improving Treatments for Depression","volume":"320","author":"Cuijpers","year":"2018","journal-title":"JAMA"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"16065","DOI":"10.1038\/nrdp.2016.65","article-title":"Major depressive disorder","volume":"2","author":"Otte","year":"2016","journal-title":"Nat. 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