Submitted to: Nutrition Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 14, 2011
Publication Date: January 17, 2012
Citation: Raatz, S.K., Young, L.R., Picklo, M.J., Sauter, E.R., Qin, W., Kurzer, M.S. 2012. Total dietary fat and fatty acid content modify plasma phospholipid fatty acids, desaturase activity indices and urinary prostaglandin E. Nutrition Research. 32:1-7. Interpretive Summary: Consuming a low fat diet is associated with reduced the risk of chronic metabolic diseases. We tested whether a low fat diet or a low fat diet with additional omega-3 (n-3) fat would enhance n-3 content of blood fats (phospholipid fatty acids) and reduce a urinary marker related to fat metabolism(prostaglandin E2) . Phospholipid fatty acids and urinary prostaglandin E2 were measured and enzyme activity (delta 5 and 6 desaturase activities) of fat metabolism were calculated in a cross-over trial in 17 postmenopausal women fed each of three test diets for 8-week feeding periods (40% fat [HF], 20% fat [LF] and a low fat diet + n-3 [23% fat; LFn3]). We hypothesized that LF and LFn3 would enhance n-3 composition of PLFA and reduce urinary PGE2 and that these changes would be associated with alterations in delta 5 and 6 desaturase activity. The phospholipid fatty acid a-linoleic acid, eicosahexaenoic acid, docosahexaenoic acid and total n-3 increased while linolenic acid and arachidonic acid decreased with LFn3. LF resulted in enhanced arachidonic acid and docosahexaenoic acid. HF reduced delta 6 desaturase while both HF and LF increased delta 5 desaturase. Urinary prostaglandin E2 was reduced in response to both the LF and LFn3 diets. The observed effects on lipid metabolism in response to LF and LFn3 may explain the associated risk reduction in chronic metabolic diseases with low fat diets.
Technical Abstract: Compared to diets high in fat, low fat diets are associated with reduced risk of cardiovascular disease. We hypothesized that a low fat (LF; 20% fat) and a low fat high omega-3 (n-3) fatty acid diet (LFn3; 23% fat with 3% as ALA, EPA and DHA) would enhance n-3 composition of PLFA and reduce urinary prostaglandin E2 (PGE2) relative to a high fat diet (HF, 40% fat) and that these changes would be associated with alterations in delta 5 and 6 desaturase (D5D, D6D) activity. Phospholipid fatty acids and urinary PGE2 were measured and D5D and D6D activity indices calculated in a cross-over trial in 17 postmenopausal women fed each of three test diets (HF, LF, LFn3) for 8-week feeding periods. Desaturase activity indices were calculated as D5D: 20:4n-6/20:3n-6 and D6D: 20:3n-6/18:2n-6. PLFA ALA, EPA, DPA, DHA and total n-3 fatty acids increased while LA and ARA decreased with consumption of LFn3. The LF resulted in enhanced ARA and DHA. HF reduced D6D while both HF and LF increased D5D. Urinary PGE2 was reduced in response to both the LF and LFn3 diets. Low fat diets, with or without long chain n-3 fatty acids, promote positive health effects due in part to favorable alteration of PLFA profiles and modification in desaturase activity indices suggesting the type and amount of fat consumed is a modifiable risk factor for the prevention of cardiovascular disease.