Urine metabolites are correlated with elevated urine inflammatory factors in rheumatoid arthritis at early stage

Abstract Aim: The levels of urine metabolites, rheumatoid factor (RF) and inflammatory factors are altered in rheumatoid arthritis (RA) and osteoarthritis (OA) patients. However, the level of them has not been quantitatively evaluated yet, as well as the correlation between the urine metabolites, RF and inflammatory factors. This research aims to investigate the urine metabolites and inflammatory factors from patients with OA and early rheumatoid arthritis (e-RA) to explore the relationship between the urine metabolites and RF or inflammatory factors. Methods: A total of 455 individuals were included in this study. Urine specimen was collected from 190 healthy volunteers, 26 osteoarthritis patients and 239 RA patients in which 37 subjects were diagnosed as early stage RA (e-RA). Metabolites in urine were extracted and analyzed with liquid chromatography-mass spectrometry (LC-MS) technique. Urine RF and inflammatory factors were measured with MSD V-Plex Proinflammatory Panel 1 Human Kit. Results: RF and nine of the inflammatory factors were significantly elevated in e-RA compared with OA and controls. Nine kinds of metabolites levels were found to positively correlated with urine RF level, two of which including 2-Methylnaphthalene (r= 0.636, p= 0.00195) and 3,4-Dihydroxy-L-phenylalanine (r= 0.524, p= 0.0149) were significantly elevated in e-RA group. Conclusion: Urine from e-RA patients exhibited different levels of metabolites, rheumatoid factor (RF) and inflammatory factors from patients without RA and OA. Nine metabolites showed significant positive correlation with RF level. Among these nine metabolites, 2-Methylnaphthalene (r= 0.636, p= 0.00195) and 3,4-Dihydroxy-L-phenylalanine (r= 0.524, p= 0.0149) elevated at early stage of RA, which could serve as a marker for arthritis screening and early diagnostic.