The impact of dietary long-chain polyunsaturated fatty acids on bone and cartilage in gilts and sows

Dietary long-chain PFO including arachidonic acid (ARA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) are precursors for several inflammatory mediators. The objective of this study was to characterize the effects of dietary PFO supplementation on bone, cartilage, and synovial fluid in 2 ages of pigs. Sows and gilts were fed either control corn/soybean meal based diets or the control diet supplemented with PFO from Gromega (PFO; JBS United, Sheridan, IN). Sows were fed their diets for 24.5 mo and slaughtered at 43 mo while gilts were fed their diets from weaning until slaughter at 111 kg. Cartilage was harvested from both humeroulnar joints of 14 sows (7/treatment) and 16 gilts (8/treatment) within 30 h of slaughter for fatty acid analysis and explant cultures. Synovial fluid was collected from the carpal joints of each pig postmortem. The right fused radius/ulna was collected for computed tomography (CT) analysis. Cortical width and density were determined and trabecular density was measured at the distal radius. Cartilage explants were allocated to 24-well culture plates with 2 discs per well and cultured over 72 h at 37°C in serum-free Dulbecco’s modified Eagle’s medium: nutrient mixture F-12 (Ham) medium. Six wells/pig were treated with 10 ng/mL of recombinantporcine interleukin-1 (rpIL-1). At 24, 48, and 72 h of culture, media were removed and reserved for analysis of proteoglycans, nitric oxide (NO), and PGE₂ concentrations. The CT scans of the radius/ulna from gilts revealed no differences for cortical width and bone density. Sows fed PFO had greater cortical width of the proximal ulna (P < 0.05) and decreased cortical width of the distal radius (P < 0.05). Sows fed PFO had increased DHA (P < 0.01) and a decrease in the omega-6 to omega- 3 ratio (P < 0.05) in cartilage. Gilts fed PFO had increased DHA (P < 0.01), C22:1 (P < 0.01), and docosapentaenoic acid (P < 0.01) and a tendency for increased EPA (P = 0.093) concentrations in cartilage. Changes in dietary fatty acids in the gilts and sows had no effect on the variables tested in vitro. Although the PFO diet increased omega-3 incorporation into chondrocytes, the biological significance is unclear since concentrations of ARA were at least 9-fold higher than EPA or DHA. Therefore, if omega-3 fatty acids can mitigate inflammation in joints, the benefit would likely either be the result of systemic changes in inflammatory mediators orhigher concentrations in the diet.