2011 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 During the reporting period, the analysis of the 390 samples delivered to ARS in the previous cycle was completed and the final data was transmitted to the collaborating PI. SRI personnel prepared and delivered an additional 100 samples for analysis and the data has been acquired and analyzed for this final set of samples. Data will be transmitted upon final quality review. The ingestion of omega-3 fatty acids enriched lipoprotein particle in omega-3 fatty acids and many of there oxygenated metabolites, while reducing levels of some omega-6 fatty acids. Improvements in vascular endothelial function were correlated with changes in omega-3 fatty acid metabolites in low and high density lipoprotein fractions. However, different individuals showed different shifts in metabolite patterns, suggesting the presence of distinct metabolic phenotypes within the study group. Therefore, while the impact of dietary lipids on bioactive metabolites in lipoprotein particles may be associated with the beneficial effects of omega-3 fatty acid rich diets, “one size fits all” dietary recommendations may not maximize health benefits in the US population. Results from these studies have been presented at domestic conferences, and manuscripts are in preparation.