Tryptophan-kynurenine pathway dysregulation and its association with inflammatory biomarkers

In this study we have evaluated a potential value of tryptophan (Trp) and kynurenine pathway (KP) metabolites as biomarkers in different types of acute inflammation and investigated their possible association with classical inflammatory markers (CRP, ESR, and WBC). The study included 100 patients with elevated inflammatory parameters and 50 healthy controls. Chromatographic separation and analysis of samples were performed in positive electrospray ionization mode using a LC-MS/MS API 3200 device. We found that Trp levels decreased significantly in the patient groups, while levels of kynurenine (KYN) and kynurenic acid (KYNA) increased significantly. The Trp/KYN ratio was reduced considerably in the presence of inflammation. Moderate positive correlations were found between KP metabolites and CRP, ESR, and WBC values. It was observed that KP activity increased independently of the source of inflammation. The findings suggest that KP metabolites alone are not definitive for diagnosing inflammation but can serve as complementary biomarkers reflecting the biological severity of inflammation and the immune-metabolic response. Assessing Trp metabolism, particularly when combined with classical markers, can contribute to the molecular understanding of inflammation.