Genetic, morphological and isotopic population structure of lake whitefish (Coregonus clupeaformis) in northern Lake Winnipeg and Playgreen Lake

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Mavros, William V.
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A 61-day study was designed to assess the effects of the level of dietary linolenic acid (LNA) and its ratio to linoleic acid (LA) on plasma lipoproteins (LP) and the fatty acid composition of the platelet phospholipids (PL) in twelve normolipidemic men. The study consisted of four diet periods: a 7-day pre-emperimental period and two 18-day experimental periods separated by an 18-day washout period. Diets supplied 53% of total energy as carbohydrate, 14% as protein and 33% as fat. Added fat accounted for 79% of the total fat or 29% of total energy. A mixture of fats (MF) was provided during the pre-experimental and washout periods. Subjects were randomly assigned to receive two or three experimental diets containing: i) 100% low linolenic canola oil (LLNA), ii) 85% regular canola oil and 15% sunflower oil (CAN), or iii) 67% regular canola oil, 15% flax oil, and 18% sunflower oil (FLAX). The experimental diets provided similar amounts of LA but different amounts of LNA. The LA/LNA ratios and the LNA levels of the diets were 6.3, 4.3 and 2.5, and 4%, 6% and 11% respectively. Fasting 12-hour blood samples were analyzed for plasma lipids and LP. Platelets were isolated from the plasma and the fatty acid composition of the phosphatidylcholine (PC), phosphatidylethanolamine (PE) and alkenylacyl ethanolamine phosphoglyceride (PPE) fractions were determined. Plasma total cholesterol (TC) and low density lipoprotein cholesterol (LDL-C) decreased on all experimental diets. Plasma triplycerides (TG) and high density lipoprotein cholesterol (HDL-C) decreased (p<0.05; p<0.03, resp.) on the FLAX diet, whereas very low density lipoprotein cholesterol (VLDL-C) decreased (p<0.01) on the CAN diet. Fatty acid analyses indicated that LNA levels of PL increased on the experimental diets. Levels of eicosapentaneoic acid (EPA) increased on the FLAX diet but very unaffected by the LLNA and CAN diets. Levels of long chain (LC) n-3 PUFA decreased on the LLNA diet, were unchanged on the CAN diet, but showed a trend towards increased levels on the FLAX diet. By contrast, platelet AA levels and n-6 LC PUFA levels decreased on all experimetnal diets. Thus, the LLNA diet (LA/LNA ratio of 6.3) reduced n-3 LC PUFA levels in platelet PL, primarily as a result of a decrease in the DPA level. Diets with lower LA/LNA ratios (2.5 and 4.3) maintained total n-3 LC PUFA levels, however only the diet with the lowest LA/LNA ratio increased platelet EPA levels.