Indolelactic acid as a potential metabolic biomarker for diagnosing gout.

Gout is a heterogeneous disease caused by the deposition of monosodium urate crystals in joints, but its pathogenesis is currently poorly understood. The discovery of novel biomarkers is necessary for the early detection and diagnosis of gout. The present study aimed to characterize the metabolic profile of patients with gout using metabolomics, and to uncover the underlying pathological mechanisms leading to gout development. Serum samples were collected from 49 healthy participants and 47 patients with gout. Using ultra-high-performance liquid chromatography Orbitrap Exploris mass spectrometer non-target metabolomics technology, with a variable importance in the projection >1 and a false discovery rate adjusted P<0.05 was used, while a biomarker panel was screened using receiver operating characteristic (ROC) analysis. The potential differentially expressed markers related to gout were identified by ROC analysis, and the erythrocyte sedimentation rate, uric acid, alanine transaminase, aspartate aminotransferase, creatinine, triglyceride, total cholesterol, high-density lipoprotein and low-density lipoprotein levels were significantly different in the group of patients with gout compared with those in healthy individuals. A total of 186 differentially expressed metabolites were identified, with 156 differential metabolites upregulated and 30 downregulated in the patients with gout compared with healthy individuals. Pathway analysis demonstrated that D-glutamine and D-glutamate metabolism may serve key roles in gout. Compared with healthy people, the indolelactic acid (ILA) level of patients with gout was significantly higher. ILA may serve as a potential biomarker for the diagnosis of gout and could be used to detect or predict gout progression in the future.