Fig. 6

Relation between control-normalized serum and synovial fluid (SF) lipid levels per OA cohort. Ratios of lipid species concentrations between early OA and control (A) and between late OA and control (B) were calculated separately for SF and serum. The horizontal and vertical auxiliary lines at 1.5 indicate lipid species with median serum and/or SF concentrations that are at least 1.5-fold higher than their medians in healthy controls. The diagonal auxiliary line is the line of identity, above which median phospholipid or sphingolipid species concentrations are higher in serum than in SF compared with controls. Each dot represents a lipid species that is color-coded to its lipid class. Cer, ceramide; HexCer, hexosylceramide; LPC, lysophosphatidylcholine; PC, phosphatidylcholine; PC O, ether-linked phosphatidylcholine; PE, phosphatidylethanolamine; PE P, phosphatidylethanolamine-based plasmalogen; SM, sphingomyelin