No abstract

Dietary n-3 long-chain polyunsaturated fatty acid (LCPUFA) supplementation has previously been shown to modify joint-related inflammation in several species, although information in the horse is lacking. We investigated whether dietary supplementation with n-3 LCPUFA would modify experimentally induced synovitis in horses. Twelve, skeletally mature, non-pregnant mares were randomly assigned to either a control diet (CONT) or an n-3 long-chain fatty acid-enriched treatment diet (N3FA) containing 40 g/day of n-3 LCPUFA for 91 days. Blood samples taken on days 0, 30, 60 and 90, and synovial fluid collected on days 0 and 90 were processed for lipid composition. On day 91, joint inflammation was stimulated using an intra-articular (IA) injection of 100 ng of recombinant equine IL-1beta (reIL-1β). Synovial fluid samples taken at post-injection hours (PIH) 0, 4, 8 and 24 were analysed for prostaglandin E2 (PGE2 ), matrix metalloproteinase (MMP) activity and routine cytology. Synovium and articular cartilage samples collected at PIH 8 were analysed for gene expression of MMP 1 and MMP 13, interleukin-1beta (IL-1β), cyclooxygenase 2 (COX-2), tumour necrosis factor-alpha and the aggrecanases, a disintegrin and metalloprotease with thrombospondin motifs (ADAMTS)-4 and ADAMTS-5. A 90-day feeding period of n-3 LCPUFA increased serum phospholipid and synovial fluid lipid compositions of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) compared to CONT horses. The reIL-1β injection caused an inflammatory response; however, there was no effect of dietary treatment on synovial fluid PGE2 content and MMP activity. Synovial tissue collected from N3FA horses exhibited lower expression of ADAMTS-4 compared to CONT horses. Despite the presence of EPA and DHA in the synovial fluid of N3FA horses, dietary n-3 LCPUFA supplementation did not modify synovial fluid biomarkers compared to CONT horses; however, the lower ADAMTS-4 mRNA expression in N3FA synovium warrants further investigation of n-3 LCPUFA as a joint therapy.

-Polyunsaturated omega-3 fatty acids (n-3 PUFA) are a family of essential fatty acids with many biological activities. These fatty acids are incorporated into cell membranes, changing their structural and functional characteristics. N-3 PUFA can act by modulating inflammatory responses at different levels. Omega-3 PUFA can be converted in the body to longer-chain n-3 PUFA at a limited rate and are differently converted in body systems. It appears that when specific longerchain n-3 PUFA are desired these need to be supplemented directly in the diet. In different species some evidence indicates a potential effect on improving insulin sensitivity. Recently, a novel class of n-3 PUFA-derived anti-inflammatory mediators have been recognized, termed E-series and D-series resolvins, formed from EPA and DHA, respectively. N-3 PUFA derived resolvins and protectins are heavily involved in the resolution of inflammation. Supplementation with n-3 fatty acids in horses may help manage chronic inflammatory conditions such as osteoarthritis, equine metabolic syndrome, laminitis, and thereby help to improve longevity of sport horse.