Decreasing the Dietary Ratio of Linoleic Acid (n-6) and Alpha-linolenic Acid (n-3) Does Not Reduce Adiposity or Mitigate Bone Deterioration of Obese Mice (P08-096-19)

Abstract

Abstract Objectives To investigate whether the ratio of n-6: n-3 mainly as linoleic acid (LA, 18:2n-6) and alpha-linolenic acid (ALA, 18:3n-3), when ALA was kept constant, affects adiposity or adiposity-induced changes in bone structure in mice fed a high-fat diet. Since LA is a precursor for arachidonic acid which is the substrate for certain proinflammatory eicosanoids, n-6 fatty acids have been considered to promote inflammation, whereas n-3 fatty acids are considered to have anti-inflammatory properties. Studies show adiposity and inflammation are inversely associated bone mass. Therefore, we hypothesized that decreasing dietary LA content (n-6: n-3 ratio) mitigates high-fat diet (HF) induced adiposity and bone loss. Methods Fifty-two male C57BL/6 mice at 6-wk-old were randomly assigned to 4 treatment groups (n = 13/group) and fed one of the diets as described in the Table below ad libitum for 6 months: a normal-fat diet (NF, 10%en) with n-6 at 6%en or HF diets (45%en) with n-6 at either 9%, 6%, or 3%en, respectively. ALA content in the diets was kept the same for all groups at 1%en, which is above the minimum requirement (0.68%en) for rodents. Diets were formulated with a combination of high oleic sunflower oil, palm oil, safflower oil and flaxseed oil to achieve desired levels of fatty acids. Results Compared to the NF, the HF increased fat mass, percentage body fat, trabecular separation, serum bone resorption marker (tartrate-resistant acid phosphatase), and decreased bone volume/total volume (P < 0.05). The ratio of n-6: n-3 did not significantly affect fat mass, serum bone resorption marker, or any bone structural parameters. Conclusions These data indicate that decreasing the dietary n-6: n-3 ratio by reducing LA intake does not reduce adiposity or improve bone structure in obese mice. Funding Sources USDA ARS Project no. 3062-51000-053-00D. Supporting Tables, Images and/or Graphs