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.