Inflammatory markers after supplementation with marine n-3 or plant n-6 PUFAs: A randomized double-blind crossover study

Omega-3 (n-3) (e.g., EPA/DHA) and omega-6 (n-6) (e.g., linoleic acid [LA]) FAs are suggested to have opposite effects on inflammation, but results are inconsistent and direct comparisons of n-3 and n-6 are lacking. In a double-blind, randomized, and crossover study, females (n = 16) and males (n = 23) aged 30-70 years with abdominal obesity were supplemented with 3-4 g/d EPA/DHA (fish oil) or 15-20 g/d LA (safflower oil) for 7 weeks, with a 9-week washout phase. Cytokines and chemokines (multiplex assay), acute-phase proteins (MALDI-TOF mass spectrometry), endothelial function (vascular reaction index), blood pressure, FA composition (red blood cell membranes/serum/adipose tissue, GC-MS/MS), and adipose gene expression (microarrays, quantitative PCR) were measured. While significant differences between treatments in relative change scores were found for systolic blood pressure (n-3 vs. n-6: -1.81% vs. 2.61%, P = 0.003), no differences between n-3 and n-6 were found for any circulatory inflammatory markers. However, compared with baseline, n-3 was followed by reductions in circulating TNF (-24.9%, P < 0.001), regulated upon activation, normal T cell expressed and secreted (-12.1%, P < 0.001), and macrophage inflammatory protein 1-beta (-12.5%, P = 0.014), and n-6 by lowered TNF (-18.8%, P < 0.001), regulated upon activation, normal T cell expressed and secreted (-7.37%, P = 0.027), monocyte chemoattractant protein-1 (-7.81%, P = 0.020), and macrophage inflammatory protein 1-beta (-14.2%, P = 0.010). Adipose tissue showed significant treatment differences in weight percent of EPA (n-3 vs. n-6: 50.2%∗ vs. -1.38%, P < 0.001, ∗: significant within-treatment change score), DHA (16.0%∗ vs. -3.67%, P < 0.001), and LA (-0.033 vs. 4.91%∗, P < 0.001). Adipose transcriptomics revealed overall downregulation of genes related to inflammatory processes after n-3 and upregulation after n-6, partly correlating with changes in circulatory markers. These data point to tissue-specific proinflammatory effects of high n-6 intake, but a net systemic anti-inflammatory effect as for n-3.