2012 Annual Report 1a.Objectives (from AD-416): To determine how omega-3 fatty acid supplementation alters the concentration and distribution of oxygenated PUFA metabolites in lipoprotein particles. 1b.Approach (from AD-416): A 4-week human feeding study will be conducted using pharmaceutical grade omega-3 fatty acids, collecting fasted plasma, isolating lipoproteins, and assessing the impact on lipid and oxylipid profiles within the esterified lipid pool. 3.Progress Report: This is the final report for the Agreement 58-5306-0-195 titled “Impact of Omega 3 fatty acid feeding on lipoprotein oxylipid distribution in healthy humans” terminated in February 2012. All planned experiments were completed prior to the start of FY2013. Substantial results were realized over the 2 years of the project. Capitalizing on the human resources infrastructure of colleagues at the Sanford Research Institute/University of South Dakota, samples were obtained from a number of human omega-3 feeding trials, and novel information was obtained regarding the responses of human subjects to this treatment. First, we determined that omega-3 fatty acids in circulation exhibit a threshold behavior, and that as this threshold is approached, they become harder to change. Therefore, as a persons concentration of omega-3 fatty acids increase, the amount required to produce a change in these levels increases. Moreover, there is a relationship between body mass and this response, such that larger individuals need to consume more to obtain the same benefit. These findings suggest that dietary recommendations for omega-3 fatty acid intake to maintain a beneficial level may be improved by considering the subjects weight. In addition, we have also found that the lipoprotein particles are a rich source of oxygenated lipid mediators, and that each lipoprotein particle displays a unique profile of these mediators. Moreover, omega-3 fatty acid consumption impacts different classes of oxylipins within different lipoproteins to a different degree. Specifically, omega-3 fatty acid consumption decreases pro-inflammatory oxylipins with the very low density lipoprotein particles while increasing the anti-inflammatory lipids in this pool. These findings are consistent with the benefits to vascular inflammation noted for omega-3 fatty acid ingestion, and offer a novel mechanism for cardiovascular risk reduction beyond lowering of low density lipoprotein cholesterol. Together these findings have enhanced our understanding of the impact of omega-3 fatty acids on lipoprotein metabolism and advance the goals of the parent Project 5306-51530-019-00D, Linking Foods, Behavior and Metabolism to Promote a Healthy Body Weight.