Small Molecules Originated from Tryptophan and their Clinical Significance as Potential Biomarkers

L-tryptophan is an essential amino acid necessary for the human body to function. Its degradation occurs through two metabolic pathways. Approximately 95 % of the Ltryptophan available in the body is converted via the kynurenine pathway, while the remainder is degraded via the serotonin pathway. Properly maintained balance between the concentrations of individual small molecular metabolites is extremely important to maintain homeostasis in the human body, and its disruption could lead to the development of numerous neurological, neurodegenerative, neoplastic, as well as cardiovascular diseases. Recent reports have suggested that by controlling the levels of selected L-tryptophan metabolites (potential biomarkers), it is possible to diagnose numerous diseases, monitor their course, and assess patient prognosis.The aim of this paper is to review the currently important clinical applications of selected biomarkers from the L-tryptophan metabolism pathways that would be helpful in early diagnosis, monitoring the course and treatment of serious diseases of affluence, which ultimately could improve the patients' quality of life, as well as support targeted therapy of the aforementioned diseases.Since the biochemical biomarkers determination in body fluids presents the ideal minimally invasive tool in the patents' diagnosis and prognostication, this study emphasizes the current trends and perspectives of application of analysis of selected L-tryptophan metabolites named kynurenine and serotonin-derived small compounds in the routine medical procedures.