Omega-3 fatty acids and joint health, possible actions

Fatty acid-derived compounds appear to play an important role in bone and joint health. Numerous lipid-derived hormones (eicosanoids), derived from arachidonic acid (AA, an omega-6 fatty acid) and eicosapentaenoic acid (EPA, an omega-3 fatty acid), regulate the inflammatory process and influence the general health status of the skeletal system in the body. In general, eicosanoids (prostaglandins, leukotrienes, and related compounds) from omega-6 fatty acids are more potent and more pro-inflammatory compared to the omega-3 fatty acids 1. Prostaglandins produced from omega-3 fatty acids are weaker counterparts of the omega-6 derivatives and are less inflammatory, sometimes even anti-inflammatory.

In dogs, it is estimated that as much as 20% of those older than one year are affected by osteoarthritis (OA). OA is a degenerative joint disease that is characterized by cartilage breakdown over time. OA is the most common cause of lameness in dogs. Though there is no cure at this moment for this disease, treatments are necessary to relieve pain and help the affected animal remain active. A significant pathophysiological factor in the progression of osteoarthritis is synovial tissue inflammation in the affected joint area. The inflammation process is accompanied by increased expression of several critical inflammatory signaling molecules including cytokines, angiogenic factors, adhesion molecules, and inducible cyclooxygenase (or COX-2). COX is the enzyme that catalyzes the conversion of AA and EPA to their respective prostaglandin (PG) species (AA to PGE2 and EPA to PGE3). In one human study, Benito MJ et al. 2 showed that synoviocytes from OA patients produced significantly more PGE2, a strong pro-inflammatory factor, than the cells from control subjects in an in vitro culture system.

Omega-3 fatty acids are recommended to arthritic dogs primarily because of their antagonistic actions against that of the omega-6 fatty acids. In this sense, omega-3 fatty acids serve as an adjuvant treatment with COX inhibitors in controlling the symptoms of joint disease. Diets with a high amount of omega-3 fatty acids are formulated and marketed for dietary management of adult arthritic dogs such as described at a Purina website. These food products are sold only through veterinarians.

References

  1. Watkins BA, Lippman HE, Le Bouteiller L, Li Y, Seifert MF. Bioactive fatty acids: role in bone biology and bone cell function. Prog Lipid Res 2001;40:125-148.
  2. Benito MJ, Veale DJ, FitzGerald O, van den Berg WB, Bresnihan B. Synovial tissue inflammation in early and late osteoarthritis. Ann Rheum Dis 2005;64:1263-1267.

Key Points

  • Lipid-derived hormones (eicosanoids) synthesized from AA and EPA mediate the inflammatory process and influence the general health status of the skeletal system throughout the body.
  • COX is the enzyme that catalyzes the conversion of AA and EPA to their respective prostaglandin species (AA to PGE2 and EPA to PGE3).
  • Omega-3 fatty acids are recommended for arthritic dogs primarily because of their antagonistic actions against that of the omega-6 fatty acids, which are the source of many pro-inflammatory factors.