Status of tryptophan metabolites in different stages of chronic kidney disease of non-diabetc etiology

Introduction. Modification of tryptophan metabolism during the progression of chronic kidney disease may have significant pathophysiological consequences. The aim of this study was to investigate the status of metabolic products of tryptophan, indoxyl sulfate and kynurenine in different stages of chronic kidney disease. Material and Methods. In all participants included in the cross-sectional study (n = 66) with previously diagnosed chronic kidney disease, the parameters of renal function were measured: glomerular filtration rate using radionuclide plasma clearance with 99mTc-labelled diethylene triamine penta-acetate and effective renal plasma flow using 131Ilabeled orthoiodohippuric acid. Plasma concentrations of indoxyl sulfate and kynurenine were measured by high-performance liquid chromatography. Results. A significant difference was observed in the concentrations of both metabolites between the observed groups (Group II - measured glomerular filtration rate - 15 - 60 ml/min/1.73 m?; n = 36 vs. Group I measured glomerular filtration rate > 60 l/ min/1.73 m?; n = 26): indoxyl sulfate 1.07 ? 0.89 vs. 2.44 ? 4.05 ?g/ ml, p < 0.001; kynurenine 3.15 ? 0.22 vs. 3.21 ? 0.17 ?g/ml, p < 0.05. The correlation was statistically significant between glomerular filtration rate and kynurenine - r = -0.38, p = 0.001 and indoxyl sulfate - r = 0.56, p ? 0.001; effective plasma renal flow and kynurenine - r = -0.33, p < 0.05 and indoxyl sulfate - r = 0.46, p ? 0.001. Conclusion. There is a significant difference in the plasma concentrations of indoxyl sulfate and kynurenine in the group of patients with glomerular filtration rate of 15 - 60 ml/min/1.73 m? compared to patients with glomerular filtration rate > 60 ml/min/1.73 m?. In patients with chronic kidney disease, plasma concentrations of both metabolites of tryptophan are inversely correlated with the glomerular filtration rate and effective plasma renal flow.