Effects of the Dietary ω3:ω6 Fatty Acid Ratio on Body Fat and Inflammation in Zebrafish (Danio rerio).

Most animals require specific (essential) dietary fatty acids, and deficiencies in these fatty acids typically exert a negative effect on their health at some level. The ω3 and ω6 families of fatty acids are essential polyunsaturated fatty acids (PUFA) or long-chain PUFA (LC-PUFA) for many animals, including humans; however, consensus regarding the recommended dietary levels of these PUFA has not been achieved for any species, including humans. Several studies have proposed that a disproportionately high intake of ω6 PUFA and LC-PUFA promotes inflammation, resulting in chronic inflammatory diseases associated with metabolic syndrome.10,22 This ‘high’ intake is difficult to describe accurately because both individual as well as regional diversity in the dietary intake of ω3 and ω6 fatty acids exist globally. Over the last century, diets in the western hemisphere have shifted to a dramatically increased consumption of total lipids. This increase in total fat consumption is associated with increases in ω6 PUFA and ω6 LC-PUFA intakes and corresponding decreases in ω3 PUFA and ω3 LC-PUFA.16 The shift in the dietary ω3:ω6 ratio, toward ω6 and away from ω3 fatty acids, in industrialized societies has been proposed to be the major factor contributing to inflammatory diseases.22 This proinflammatory effect is often attributed to the production of arachidonic acid metabolites, which act as potent proinflammatory and plaque forming molecules, from ω6 fatty acids, like linoleic acid.7 However, many antiinflammatory mediators also are produced during the metabolism of ω6. Several studies support a possible association between a reduced risk of coronary heart disease and increased dietary ω6 PUFA.7 The American Heart Association Science Advisory Panel has stated, “At present, there is little direct evidence that supports a net proinflammatory, proatherogenic effect of linoleic acid (18:2 ω6) in humans.”11 The authors of a recent review19 concluded that reducing the intake of dietary ω6 fatty acid did not change the levels of arachidonic acid in the plasma, serum, or erythrocytes of adults who consumed western-type, high-fat diets. Other scientists18 have suggested that specific proportional combinations of ω3 and ω6 fatty acids may actually decrease the concentrations of proinflammatory cytokines. Zebrafish continue to gain popularity as an animal model for cardiovascular disease.4 For example, blood vessel plaques formed in zebrafish that consumed a high-cholesterol (4%) diet, mimicking atherosclerosis in humans.24 Recent advances in the area of zebrafish nutrition25 allow the use of formulated diets, wherein the levels of specific nutrients, such as fatty acids, can be modified to evaluate response. The current study evaluated the effects of different dietary ω3:ω6 fatty acid ratios on weight gain, body composition, and inflammatory response proteins in the zebrafish.