2013 Annual Report
1a.Objectives (from AD-416):
Consumption of cold water fish, including salmon, has been associated with reductions in cardiovascular health risks. However, the benefits are associated with the fatty acid composition of these fish. Modern fish farming practices result in a change in the composition of oils in farmed vs. wild caught fish. Initial studies indicated that diets prepared from Atlantic salmon raised on a soybean oil rich diet produced insulin resistance in obesity prone mice. In this follow-up study, we will evaluate the mechanisms of insulin resistance and metabolic changes in mice fed diets enriched with protein from salmon raised on fish oil, rapeseed oil, and soybean oil rich diets, with the ultimate goal of guiding the aqua culture industry to produce a product with maximal health benefit.
1b.Approach (from AD-416):
Fillets of Atlantic salmon fed diets where fish oil was partly (80%) replaced with either rapeseed oil (RO) or soy bean oil (SO) will be used to prepare western diets (WD) for a mouse feeding trial. We will replace 50% of the standard dietary protein source (casein) with proteins from salmon fed FO, RO, or SO (WD-FO, WD-RO and WD-SO, respectively) . Due to a large difference in casein and salmon protein digestibility, 50% of the protein in our western-reference diet (WD-Ch) will also be exchanged. A low fat reference group will also be included (LF). Analyses will include: in-depth liver histology; lipidomic profiling of liver and plasma (fatty acids, oxylipins, endocannabioids and ceramides); pyruvate, glucose, and insulin tolerance tests; fecal bacteria DNA purification and pyrosequencing (if economically feasible).
This research relates to objective 4 of the inhouse project, “Determine the impact of dietary lipids on body weight, adiposity, and/or metabolic health indices by assessing their influence on lipoprotein-dependent trafficking of bioactive lipids to adipose and peripheral tissues, their effects on the regulation of metabolic homeostasis, and their interactions with distinct fatty acid desaturase/elongase activity phenotypes". During the reporting period, 60 plasma and liver samples were delivered to ARS and their analysis for an array of lipids and lipid mediators were completed and the final data were analyzed and transmitted to the collaborating Principal Investigator (PI). It was found that the diet of farm raised salmon affected the composition and concentrations of lipids and lipid mediators in the liver and plasma of mice ingesting diets prepared from these fish. Fish fed rapeseed oil and soybean oil based diets produced levels of 18 and 20 carbon omega-3 fatty acids in mice greater than or approaching those produced by fish oil, while soybean oil showed the greatest increases in linoleate and its metabolites in the liver. In combination with earlier studies conducted at the National Institute of Nutrition and Seafood Research (NIFES), these results indicate that rapeseed oil based diets may have significant advantages to the consumer as compared to soybean and animal meal based diets.