Relationship between the omega-3 index and specialized pro-resolving lipid mediators in patients with peripheral arterial disease taking fish oil supplements

Background Oral supplementation with n-3 polyunsaturated fatty acids (PUFA) increases the omega-3 index, a biomarker of red blood cell eicosapentaenoic acid and docosahexaenoic acid, and plasma levels of biosynthesis pathway markers and potent lipid mediators involved in the resolution of inflammation among patients with peripheral arterial disease (PAD). Objective We aimed to quantify the association between an upstream change in the omega-3 index and downstream changes in lipid mediator production. Methods We conducted a secondary analysis of the OMEGA-PAD I Trial, a randomized, placebo controlled trial investigating high-dose n-3 PUFA oral supplementation in PAD patients. Eighty subjects were randomized to either 4.4 g of fish oil or placebo for 1 month. Regression analyses using generalized estimating equation techniques were used to investigate the relationship between changes in the omega-3 index and changes in lipid mediators, pre- and post-intervention. Results In the fish oil group, there was a significant increase in the omega-3 index (5 ± 1% to 9 ± 2%, P <.001) as well as in the plasma levels of several downstream lipid mediator pathway markers of resolution, which are involved with the regulation of leukocyte effector function and host defense. A doubling of the omega-3 index correlated with increases of 2.3-fold in 18-hydroxy-eicosapentaenoic acid (HEPE; P <.0001), 1.7-fold in 15-HEPE (P =.03), 1.9-fold in 5-HEPE (P =.04), and 3.6-fold in 4-hydroxy-docosahexaenoic acid (P <.001). Conclusion Among subjects with symptomatic PAD who took oral fish oil supplements for 1 month, observed changes in the omega-3 index were strongly associated with increases in downstream mediators in the biochemical pathways of resolution.