Designer oils low in n-6:n-3 fatty acid ratio beneficially modifies cardiovascular risks in mice
Designer oils low in n-6:n-3 fatty acid ratio beneficially modifies cardiovascular risks in mice
Year: 2009
Authors: Riediger, N.D. Azordegan, N. Harris-Janz, S. Ma, D.W.L. Suh, M. Moghadasian, M.H.
Publication Name: Eur. J. Nutr.
Publication Details: Volume 48; Number 5; Pages 307 – 314.
Abstract:
Cardiovascular benefits of dietary n-3 fatty acids have been shown. However, benefits of n-3 fatty acids as part of a high fat, low n-6:n-3 fatty acid ratio diet has not been fully characterized. Aim of this study is to investigate cardiovascular and metabolic benefits of designer oils containing a low ratio of n-6:n-3 fatty acids in C57BL/6 mice. Three groups of C57BL/6 mice were fed an atherogenic diet supplemented with either a fish oil- or flaxseed oil-based designer oil with an approximate n-6:n-3 fatty acid ratio of 2:1 (treated groups, n = 6 each) or with a safflower oil-based formulation with a high ratio (25:1) of n-6:n-3 fatty acids (control group, n = 6) for 6 weeks. Food intake, body weight, and blood lipid levels were monitored regularly. Fatty acid profile of the heart tissues was assessed. Histological assessment of liver samples was conducted. At the end of the study body weight and food intake was significantly higher in the flax group compared to control. The levels of 20:5n-3 and 22:6n-3 was significantly increased in the heart phospholipids in both flax and fish groups compared to control; tissue 20:4n-6 was significantly reduced in the fish group compared to control. Significant liver pathology was observed in the control group only. Lowering dietary ratio of n-6:n-3 fatty acids may significantly reduce cardiovascular and metabolic risks in mice regardless of the source of n-3 fatty acids. (Author abstract)
Recent dietary recommendations have stressed reducing the dietary n-6:n-3 FA ratio to 2-4:1 from the current intake of 10:1 to 30:1. In this study, a designer oil that contains a desirable fatty acid profile was investigated for effects on cardiovascular and metabolic risk factors. Designer oils with low n-6:n-3 FA ratio as part of an atherogenic diet displayed beneficial effects on cardiovascular risk and tissue composition in mice. Both flax and fish groups showed a significant reduction in plasma TG at week 4, as compared to baseline data. Lower n-6:n-3 FA ratios and higher EPA/DHA concentrations in heart of the flax group (compared to control) may suggest a conversion of ALA to EPA/DHA. Dietary ALA did not significantly reduce tissue AA in most lipid fractions to a level comparable to that achieved by fish oil (EPA/ DHA). A trend toward increased cardiac tissue EPA and DHA as a result of ALA feeding was observed. Histological evaluation revealed a significantly higher degree of steatosis in the control group compared to both fish and flax groups. Additional studies are needed to determine the role of inflammation in hepatic steatosis and insulin resistance. Marginal increases in heart DHA levels were observed in the mice fed with flaxseed oil-based designer oil, indicating an ability of the heart tissue to convert ALA to DHA in mice. Flaxseed based designer oil did not increase heart tissue EPA and DHA to a comparable level as the fish group. Consumption of safflower oil based oil formulation in the control group was associated with both liver steatosis and reduced glycogen content, which may indicate the development of insulin resistance. The authors suggest that further investigations are needed to evaluate whether these pathological changes influence metabolic function, specifically insulin sensitivity and plasma glucose. (Editor's Comments)
Recent dietary recommendations have stressed reducing the dietary n-6:n-3 FA ratio to 2-4:1 from the current intake of 10:1 to 30:1. In this study, a designer oil that contains a desirable fatty acid profile was investigated for effects on cardiovascular and metabolic risk factors. Designer oils with low n-6:n-3 FA ratio as part of an atherogenic diet displayed beneficial effects on cardiovascular risk and tissue composition in mice. Both flax and fish groups showed a significant reduction in plasma TG at week 4, as compared to baseline data. Lower n-6:n-3 FA ratios and higher EPA/DHA concentrations in heart of the flax group (compared to control) may suggest a conversion of ALA to EPA/DHA. Dietary ALA did not significantly reduce tissue AA in most lipid fractions to a level comparable to that achieved by fish oil (EPA/ DHA). A trend toward increased cardiac tissue EPA and DHA as a result of ALA feeding was observed. Histological evaluation revealed a significantly higher degree of steatosis in the control group compared to both fish and flax groups. Additional studies are needed to determine the role of inflammation in hepatic steatosis and insulin resistance. Marginal increases in heart DHA levels were observed in the mice fed with flaxseed oil-based designer oil, indicating an ability of the heart tissue to convert ALA to DHA in mice. Flaxseed based designer oil did not increase heart tissue EPA and DHA to a comparable level as the fish group. Consumption of safflower oil based oil formulation in the control group was associated with both liver steatosis and reduced glycogen content, which may indicate the development of insulin resistance. The authors suggest that further investigations are needed to evaluate whether these pathological changes influence metabolic function, specifically insulin sensitivity and plasma glucose. (Editor's Comments)
