Synovial fluid and plasma n3 long chain polyunsaturated fatty acids in patients with inflammatory arthritis

•Phospholipid fatty acid profiles are similar in plasma and synovial fluid supernatants.•Similarities in fatty acids in plasma and synovial fluid were seen with many rheumatic diagnoses.•Plasma n-3 fatty acid profiles predict synovial fluid levels better than stated fish oil intakes.•Higher n-3 long chain fatty acids in plasma and SF are associated with lesser pain experience.•Fatty acid profiles of mononuclear cells from blood are similar to those from synovial fluid.

Relationships between n-3 long chain polyunsaturated fatty acids (LC-PUFA) in plasma and synovial fluid (SF) were examined in 36 patients with knee effusion within the context of a variety of rheumatic diagnoses and various stated fish oil (FO) intakes (from 0 to 30 mL of standard FO daily) of variable duration. In a sub-group of patients, correlations between PUFA in SF mononuclear cells (MNC) and cell-free supernatants of SF and between SF MNC and peripheral blood (PB) MNC were examined. Correlations were also sought between clinical data (stated FO intake, pain score) and n-3 LC-PUFA.Correlations between plasma n-3 LC-PUFA and SF n-3 LC-PUFA were very strong (r2>0.9, p<0.001). The LC-PUFA profiles of SF supernatants differed from those of MNC. PUFA profiles in PB MNC and SF MNC were similar, except for a higher proportion of DHA in the latter. Positive correlations were observed between stated intakes of FO and EPA in plasma and SF (for both r=0.37, p=0.02) and DHA in plasma (r=0.37, p=0.02) and SF (r=0.36, p=0.03). n-3 LC-PUFA in plasma and SF correlated inversely with pain score (plasma r2=0.16, p<0.02; SF r2 0.32, p=0.001).In conclusion, plasma n-3 LC-PUFA is a strong indicator of SF n-3 LC-PUFA status across a broad range of rheumatic diagnoses and FO intakes. Higher n-3 LC-PUFA in plasma and SF were associated with lesser pain experience.