Association Of Depression With Kynurenine In End-stage Renal Disease

Background/Objective: Depression is common in patients withend-stage renal disease, with prevalence rates ranging between20%and30%. The pathogenesis of depression in patients with ESRD iscomplicated. The effect of pro-inflammatory cytokines onneurotransmitters has been paid more attention recently. Theindoleamine2,3-dioxygenas（eIDO）activated by a number of cytokinesdegrades tryptophan along the kynurenine pathway, which theconcentrations of serum tryptophan are decreased, and theconcentrations of kynurenine are increased. Eventually, depression isinduced by the reduction of5-hydroxytryptamine (5-HT) level. Theobjective on this study was to examine the relationship betweendepression and degradation of tryptophan in patients with ESRD.Methods:94patients with ESRD on maintenance hemodialysiswere included,25healthy volunteers as the control group. Demographicand clinical variables were obtained. Each patients received21-item BeckDepression Inventory questionnaire to determine the presence or absenceof depression. Biochemical parameters and tryptophan, kynurenine,IL-6 were examined.Results:1. The levels of serum kynurenine and IL-6were higher (P<0.01)and the levels of serum tryptophan were lower (P<0.01) in patients withESRD than those in healthy control group.2. The hemodialysis pattern showed no significant correlationbetween depressive patients with ESRD and non-depressive patients withESRD.3. Depressive symptoms were found in19patients with ESRD. Thelevels of hemoglobin and tryptophan were lower(P<0.05) and the levelsof IL-6and kynureninein were higher (P<0.05) in depressive patientswith ESRD than those in non-depressive patients with ESRD.4. The levels of IL-6and kynurenine had positive correlationsignificantly with BDI scores(respectively, r=0.294,P=0.004;r=0.217,P=0.038). The levels of kynurenine had positive correlation significantlywith the levels of IL-6（r=0.244，P=0.019). But the BDI scores had nosignificant correlation with hemoglobin and tryptophan.Conclusions：1. The prevalence of depression (BDI>14) in patients with ESRDis20.2%.2. Because of the increasing of cytokines activating IDO, tryptophanis metabolized to kynurenine by activated IDO. The levels of IL-6and kynurenine have positive correlation significantly with BDI scores. Thelevels of kynurenine have positive correlation significantly with the levelsof IL-6. The increased kynurenine levels induce production of depression.3. The change of hemodialysis pattern in ESRD patients has norelationship with depressive disorder. How to improve the depression inpatients with ESRD through the change of hemodialysis pattern needs tobe researched further.