Bipolar disorder (BD) is a chronic psychiatric illness which, among other things, is characterized by cerebral dysfunctions, cognitive disorders and sleep disturbances. The neurobiological basis of these processes remains unclear. In recent years, studies have focused on the role of immune-inflammatory mechanisms induced by the tryptophan metabolism pathway (TRP) and the kynurenine pathway (KYN). Emerging data correlates TRP and KYN metabolites with BD's pathophysiology and course. The purpose of this review is to search the available data on the involvement of KYN's pathway in the pathophysiology, the clinical presentation and the course of BD. A systematic literature review was conducted using web-based search engines provided by PubMed (for Medline database) and Google Scholar. The search languages were English and Greek and the entries Key phrases used for the research were: bipolar disorder, depression, mania, tryptophan, kynurenine pathway, cognitive dysfunction, sleep disorder, neuroimmunology, neuroinflammation manuscripts written or published in English and Greek language. The KYN pathway is actively involved in the pathophysiology of BD. The increase in neurotoxic weight of the neuroprotective derivatives of the pathway is associated with cognitive impairment that accompany the clinical presentation of the disease. In addition, some of these metabolites are also suspected of sleep disorders in BD. Further studies are needed to investigate the mechanisms involved. The KYN pathway is a highly interesting field of encounter and interaction of the immune inflammatory system with the CNS, both involved in the pathophysiology of BD in a variety of ways. Future research can focus on clarifying the role of the metabolites of this pathway, potentially highlighting new therapeutic goals. Additionally, consideration could be given to approaching the metabolites of the KYN pathway as biomarkers for early detection, staging and monitoring of BD patients.

Key words: Bipolar disorder, tryptophan, kynurenine, cognitive impairment, sleep disorders, serotonin.

Ger. Konstantinou, C.C. Papageorgiou, E. Angelopoulos (page 338)

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