Elevated Kynurenine Levels in Patients with Primary Sjögren’s Syndrome

Abstract

Objective We aimed to investigate the plasma levels of tryptophan (Trp) and its metabolites in patients with primary Sjögren’s syndrome (pSS). Methods The study included 34 pSS patients and 42 healthy individuals, and serum Trp and kynurenine (Kyn) concentrations were measured by liquid chromatography with tandem mass spectrometry. Trp degradation was predicted using the ratio of Kyn and Trp concentrations (Kyn/Trp). Results In our study, the mean serum Trp concentration was found to be considerably lower in the pSS group than in the control group (P = .001). The levels of Kyn (P = .019) and the Kyn/Trp ratio (P < .001) were significantly higher in the pSS group than in the control group. The Kyn/Trp ratio was negatively correlated with C-reactive protein (r = −0.369, P = .032). Conclusion We found that Kyn pathway metabolism was altered in patients with pSS. This suggests that Trp metabolism may be closely linked to the disease pathogenesis of pSS.

A systematic review and meta-analysis of the kynurenine pathway of tryptophan metabolism in rheumatic diseases

“…Thus, 24 studies were selected for analysis ( Table 1 ) ( 26 – 49 ). The risk of bias, presented in Supplementary Table 3 , was moderate in 14 studies ( 26 – 35 , 37 , 41 , 44 , 45 , 47 ), and low in the remaining 10 ( 34 , 36 , 38 – 40 , 42 , 43 , 46 , 48 , 49 ). The initial certainty of evidence was low for all studies (rating 2, ⊕⊕⊝⊝) given their cross-sectional design.…”

“…We identified 21 studies (23 comparator groups) reporting tryptophan concentrations in a total of 1,526 RD patients (mean age 48 years, 24% males) and 1,404 healthy controls (mean age 43 years, 38% males; Table 1 ) ( 26 – 38 , 40 – 42 , 44 , 46 – 49 ). Ten were conducted in Europe ( 26 – 29 , 32 – 37 ), and 11 in Asia ( 30 , 31 , 38 , 40 – 42 , 44 , 46 – 49 ).…”

“…We identified 21 studies (23 comparator groups) reporting tryptophan concentrations in a total of 1,526 RD patients (mean age 48 years, 24% males) and 1,404 healthy controls (mean age 43 years, 38% males; Table 1 ) ( 26 – 38 , 40 – 42 , 44 , 46 – 49 ). Ten were conducted in Europe ( 26 – 29 , 32 – 37 ), and 11 in Asia ( 30 , 31 , 38 , 40 – 42 , 44 , 46 – 49 ). Six study groups included patients with RA ( 28 , 31 , 34 , 36 , 38 , 41 ), five with pSS ( 29 , 33 , 44 , 46 , 47 ), four with SLE ( 27 , 30 , 32 , 35 ), three with AS ( 38 , 40 ), two with SSc ( 26 , 37 ), and one with BD ( 42 ), FMF ( 48 ), and axSpA ( 49 ), respectively.…”

“…Ten were conducted in Europe ( 26 – 29 , 32 – 37 ), and 11 in Asia ( 30 , 31 , 38 , 40 – 42 , 44 , 46 – 49 ). Six study groups included patients with RA ( 28 , 31 , 34 , 36 , 38 , 41 ), five with pSS ( 29 , 33 , 44 , 46 , 47 ), four with SLE ( 27 , 30 , 32 , 35 ), three with AS ( 38 , 40 ), two with SSc ( 26 , 37 ), and one with BD ( 42 ), FMF ( 48 ), and axSpA ( 49 ), respectively. Liquid chromatography was used in 21 study groups ( 27 – 38 , 40 – 42 , 44 , 46 , 48 , 49 ), a spectrofluorimetric assay in one ( 26 ), and an enzyme-linked immunosorbent assay (ELISA) in the remaining one ( 47 ).…”

“…Six study groups included patients with RA ( 28 , 31 , 34 , 36 , 38 , 41 ), five with pSS ( 29 , 33 , 44 , 46 , 47 ), four with SLE ( 27 , 30 , 32 , 35 ), three with AS ( 38 , 40 ), two with SSc ( 26 , 37 ), and one with BD ( 42 ), FMF ( 48 ), and axSpA ( 49 ), respectively. Liquid chromatography was used in 21 study groups ( 27 – 38 , 40 – 42 , 44 , 46 , 48 , 49 ), a spectrofluorimetric assay in one ( 26 ), and an enzyme-linked immunosorbent assay (ELISA) in the remaining one ( 47 ). Among the liquid chromatography-based assays, seven used fluorimetric detection ( 27 – 33 ), and the remaining 14 mass spectrometry ( 34 – 38 , 40 – 42 , 44 , 46 , 48 , 49 ).…”