Genetic and Environmental Impacts in Major Depressive Disorder are Mediated Via Kynurenine Pathway of Tryptophan Metabolism

We were first to propose up-regulation of KYN pathway of TRY metabolism as an etiological factor in depression: “in depression metabolism of TRY is shunted away from serotonin production, and towards KYN production” since “activity of liver TRY-pyrrolase is stimulated by raised blood corticosteroids levels” (Lapin & Oxenkrug, Lancet, 1969). TRY-pyrrolase, i.e., tryptophan-2,3-dioxygenase (TDO) was the only known enzyme catalyzing TRY...