Submitted to: Osteoarthritis and Cartilage
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/28/2012
Publication Date: 5/4/2012
Citation: Baker, K., Matthan, N., Lichtenstein, A.H., Niu, J., Guermazi, A., Roemer, F., Grainger, A., Nevitt, M., Clancy, M., Lewis, C. 2012. Association of plasma n-6 and n-3 polyunsaturated fatty acids with synovitis in the knee: the MOST study. Osteoarthritis and Cartilage. 20(5):382-387. Interpretive Summary: Osteoarthritis is a painful joint disorder and is thought to be exacerbated by inflammation. The type of fat found in fish, termed omega-3 acids (n-3 PUFAs), has anti-inflammatory properties and may be beneficial in decreasing rates of osteoarthritis. The study goal was to determine whether people consuming diets containing high levels of omega-3 fatty acid would have lower rates of osteoarthritis than those consuming diets containing low levels of omega-3 fatty acids. Dietary omega-3 fatty acid intake was estimated by measuring plasma phospholipid fatty acid composition using gas chromatography. The extent of osteoarthritis was determined by magnetic resonance imaging scores. The mean age of the study subjects was 60 years, mean body mass index was 30, and there were an equal number of women and men in the study. For selected measures of osteoarthritis higher plasma phospholipid concentrations of omega-3 fatty acids were associated with lower osteoarthritis scores, for both women and men. These data suggest that higher intakes of omega-3 fatty acids, primarily those omega-3 fatty acids found in fish may reduce the risk developing or severity of osteoarthritis. Regular fish intake is currently recommended to decrease heart disease risk and may also be beneficial for osteoarthritis.
Technical Abstract: In osteoarthritis (OA) the synovium is often inflamed and inflammatory cytokines contribute to cartilage damage. Omega-3 polyunsaturated fatty acids (n-3 PUFAs) have anti-inflammatory effects whereas omega-6 polyunsaturated fatty acids (n-6 PUFAs) have, on balance, proinflammatory effects. The goal of our study was to assess the association of fasting plasma phospholipid n-6 and n-3 PUFAs with synovitis as measured by synovial thickening on contrast enhanced (CE) knee MRI and cartilage damage among subjects in the Multicenter Osteoarthritis Study (MOST). MOST is a cohort study of individuals who have or are at high risk of knee OA. An unselected subset of participants who volunteered obtained CE 1.5 T MRI of one knee. Synovitis was scored in six compartments and a summary score was created. This subset also had fasting plasma, analyzed by gas chromatography for phospholipid fatty acid content, and non-CE MRI, read for cartilage morphology according to the Whole-Organ Magnetic Resonance Imaging Score (WORMS) method. The association between synovitis and cartilage morphology and plasma PUFAs was assessed using logistic regression after controlling for the effects of age, sex, and BMI. 472 out of 535 subjects with CE MRI had complete data on synovitis, cartilage morphology and plasma phospholipids. Mean age was 60 years, mean BMI 30, and 50% were women. We found an inverse relation between total n-3 PUFAs and the specific n-3, docosahexaenoic acid with patellofemoral cartilage loss, but not tibiofemoral cartilage loss or synovitis. A positive association was observed between the n-6 PUFA, arachidonic acid, and synovitis. In conclusion, systemic levels of n-3 and n-6 PUFAs which are influenced by diet, may be related to selected structural findings in knees with or at risk of OA. Future studies manipulating the systemic levels of these fatty acids may be warranted to determine the effects on structural damage in knee OA.