Indolamine 2,3-dioxygenase (IDO) inhibitors as a potential treatment for somatic symptoms

Abstract

Somatic symptoms can be seen together with many psychiatric diseases and can present themselves in many different ways. Various studies on somatization suggest that the kynurenine pathway, which is the major degradation pathway of tryptophan, may be associated with somatic symptoms. In addition to the effect of various kynurenine metabolites, degradation of tryptophan and a decrease in serotonin and melatonin synthesis may also be responsible for the emergence of somatic symptoms. Indoleamine 2,3-dioxygenase (IDO), which is a rate limiting enzyme of the kynurenine pathway, plays a central role in the regulation of the pathway. Dysregulation of the kynurenine pathway by induction of the IDO may cause somatic symptoms. From this point of view, inhibitors of the IDO can be used for the dysregulation of the pathway. Thus, both the increase in the harmful metabolites of the kynurenine pathway can be reduced, and the endogenous serotonin and melatonin synthesis can be increased by shifting the pathway to serotonin and melatonin. In this respect, IDO inhibitors could possibly be used for somatic symptoms.