Serum trace element and mineral levels and fecal microbiota in relation to cartilage damage in rheumatoid arthritis patients

The objective of the present study was to evaluate serum trace element and mineral levels as well as taxonomic characteristics of gut microbiota and their association with cartilage damage in patients with rheumatoid arthritis (RA). Materials and methods Serum trace element and mineral levels in 41 healthy controls and 41 RA patients were assessed using inductively-coupled plasma mass-spectrometry. Taxonomic characteristics of fecal microbiota were assessed using 16S metagenomic sequencing. RA patients were characterized by increased cartilage oligomeric matrix protein (COMP) and complement component 3 (C3) levels, indicative of cartilage damage and inflammation. Results Serum Ca, Fe, Se, and Zn levels in RA patients were lower, whereas circulating Cr, Cu, and Mo concentrations exceeded the respective control values. 16S metagenomic sequencing of fecal samples revealed lower relative abundance of Firmicutes and Actinomycetota with a reduction in Firmicutes -to- Bacteroidetes ratio in RA patients. At the class level, the relative abundance of Bacilli, Coriobacteria , and Clostridia in RA patients was lower, whereas that of Bacteroidia and Negativicutes was higher compared to the control group. Tight negative association between serum Zn levels and the abundance of Bacteroidetes and Bacteroidia was observed, whereas correlation between Zn and Firmicutes -to- Bacteroidetes ratio was positive. Multiple linear regression analysis demonstrated that serum COMP level was inversely associated with serum Fe and Se levels, as well as relative abundance of Bacilli and Clostridia , being positively associated with serum Ca and C3 levels. Conclusion These novel findings demonstrate a multilateral relationship between trace element metabolism, gut microbiota, and cartilage damage in RA. © 2025 Elsevier GmbH.