The role of fatty acids in the management of osteoarthritis
Oct 01, 2004
Osteoarthritis is a chronic and potentially debilitating disease involving the disruption of metabolic homeostasis within the articular chondrocyte. Specifically, osteoarthritis involves an increased ratio of cartilage-degrading enzymes (matrix metalloproteinases, or MMPs) to their normal inhibitors, tissue inhibitors of metalloproteinases (TIMPs). It is the imbalance of TIMPs and MMPs that contributes to the pathologic breakdown of cartilage. Dietary fatty acids can help to correct this imbalance by modulating the production of inflammatory mediators.
N-3 fatty-acid types
Dietary fats are an important component of canine diets. They supply a concentrated source of energy as well as essential fatty acids, such as linoleic acid and α-linolenic acid. Due to dogs' inability to produce these fatty acids and their metabolic need for them, linoleic acid and α-linolenic acid must be supplied in the diet. Furthermore, these fatty acids serve as substrates for further desaturation and chain elongation to longer 20- and 22-carbon fatty acids.Vegetable oils—such as flaxseed, soybean, and canola oils—contain amounts of α-linolenic acid ranging from 7% to more than 50% of the oil's total fatty-acid content. Alpha-linolenic acid can be metabolized into the long-chain n-3 fatty acids, eicosapentaenoic acid and docosahexaenoic acid. However, the conversion rate of α-linolenic acid to eicosapentaenoic acid and docosahexaenoic acid is low. In dogs fed diets containing α-linolenic acid or fish oil at the same n-6:n-3 fatty-acid ratio, fish oil supplementation resulted in significantly greater eicosapentaenoic acid and docosahexaenoic acid enrichment in both the plasma and neutrophils than the group consuming the α-linolenic acid supplemented diet.1 Furthermore, even when α-linolenic acid was fed at levels of more than 20% of total energy, there was no docosahexaenoic acid enrichment in the plasma or neutrophils.1 The findings are similar in primates and people—studies reveal inefficient conversion of dietary α-linolenic acid to eicosapentaenoic acid.2-4 Even though α-linolenic acid and eicosapentaenoic acid are both n-3 fatty acids, they need to be considered separately because they're metabolized differently. The dietary n-6:n-3 fatty-acid ratio or the total n-3 fatty-acid content does not include the possible anti-inflammatory potential of a diet.5
Fatty acids and eicosanoid synthesis