Abstract
BACKGROUND: Evidence suggests that natural metabolites produced by intestinal microorganisms may have beneficial or harmful effects on osteoarthritis (OA). This could include menaquinones, which are bacterially-synthesized, biologically-active vitamin K forms abundant in the intestinal microbiome. OBJECTIVES: The overall goal of this study was to evaluate the association of intestinally-derived menaquinones with obesity-related OA. METHODS: This case-control study used data and biospecimens derived from a subgroup of Johnston County Osteoarthritis Study participants. Fecal menaquinone concentrations and microbial composition were determined in 52 obese participants with hand and knee OA and 42 age- and sex-matched obese participants without OA. The inter-relationships among fecal menaquinones were evaluated using principal component analysis. The differences in alpha and beta diversities and microbial composition across menaquinone clusters were evaluated using ANOVA. RESULTS: The samples were clustered into the following 3 groups: cluster 1 characterized by higher fecal menaquinone-9 and -10 concentrations, cluster 2 characterized by lower overall menaquinone concentrations, and cluster 3 characterized by higher menaquinone-12 and -13 concentrations. Overall, fecal menaquinone clusters did not differ between participants with or without OA (P = 0.707). Microbial diversity did not differ across the fecal menaquinone clusters (all F-test P > 0.12). However, the relative abundance of bacterial taxa differed among clusters, with higher abundance of Coprococcus, Prevotella, and Eggerthella in cluster 2 than in cluster 1; higher abundance of Oscillospira, Dorea, Eubacterium, and Bacteroides in cluster 3 than in cluster 1; and higher abundance of Prevotella, Sutterella, and Dorea in cluster 3 than in cluster 2 (all P < 0.001). CONCLUSION: Menaquinones were variable and abundant in the human gut, but the fecal menaquinone clusters did not differ with OA status. Although the relative abundance of specific bacterial taxa differed among fecal menaquinone clusters, the relevance of these differences with respect to vitamin K status and human health is uncertain.