|Murphy, Eric - University Of North Dakota|
Submitted to: Lipids Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/20/2015
Publication Date: 12/22/2015
Citation: Picklo, M.J., Murphy, E.J. 2015. A high-fat, high-oleic diet, but not a high-fat, saturated diet, reduces hepatic alpha-linolenic acid and eicosapentaenoic acid content in mice [epub ahead of print]. http://link.springer.com/article/10.1007%2Fs11745-015-4106-9.
Interpretive Summary: Omega 3 (n3) fatty acids are essential fatty acids that are important for cardiovascular health, immune health, and nervous system health. In this work, we studied the metabolism of the plant-based n3 fatty acid alpha-linolenic acid (ALA). We examined, in mice, how ALA metabolism to other types of n3 is affected by the presence of oleic acid and saturated fatty acids, fatty acids which make up the bulk of total fats consumed by Americans. Our data suggest that consuming too much oleic acid reduces the amount of n3 fatty acids in the liver and that saturated fatty acids increases the amount of n3. These data are the first to show that n3 fatty acid metabolism is regulated by the amounts of oleic and saturated fatty acids in the diet.
Technical Abstract: Considerable research centers upon the role of linoleic acid (LNA; 18:2n6) as a competitive inhibitor of a-linolenic (ALA; 18:3n3) metabolism; however, little data exist as to the impact of saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA) on ALA metabolism. We tested the hypothesis that a high SFA diet, compared to a high MUFA (oleic acid 18:1n9) diet, reduces ALA conversion to LCn3. Mice were fed for 12 weeks on three diets: (1) a control, 16% fat energy diet consisting of similar levels of SFA and MUFA (2) a 50% fat energy high MUFA energy diet (35% MUFA and 7% SFA) or (3) a 50% fat energy, high SFA energy diet (34% SFA, 8% MUFA). ALA and LNA remained constant. Analysis of hepatic lipids demonstrated a selective reduction (40%) in ALA but not LNA and a 35% reduction in eicosapentaenoic acid (EPA; 20:5n3) in the high MUFA mice compared to the other groups. Loss of ALA was reflected to a greater extent in the neutral lipid fraction, while decreases in phospholipid esterified EPA and docosapentaenoic acid (DPA; 22:5n3) were evident. Docosahexaenoic acid (DHA; 22:6n3) content was elevated by the high SFA diet. Expression of Fads1 ('5 desaturase) and Fads2 ('6 desaturase) was elevated by the high MUFA and reduced by the high SFA diet. These data indicate that a high MUFA diet, but not a high SFA diet, reduces ALA metabolism and point to selective hepatic disposition of ALA vs LNA.