Lipid emulsion rich in n-3 polyunsaturated fatty acids elicits a pro-resolution lipid mediator profile in mouse tissues and in human immune cells

Background: Lipid emulsions are a key component of total parenteral nutrition (TPN) and are administered to patients who are unable to ingest their daily required calories orally. Lipid emulsions rich with n-6 (ω-6) PUFAs are known to cause parenteral nutrition-associated liver disease and have inflammatory side effects, whereas n-3 PUFA-rich emulsions have favourable clinical outcomes.

Objectives: The present study used targeted lipid mediator analysis to investigate the metabolism of a n-3 PUFA-rich lipid emulsion and a n-6 PUFA-rich lipid emulsion in a mouse model of TPN and in primary human monocyte-derived macrophages (MDMs) and CD4+ T cells.

Results: Mice given n-3 PUFA-based TPN for 7 d had a less proinflammatory lipid mediator profile compared with those receiving n-6 PUFA-based TPN. This was characterized by higher concentrations of specialized pro-resolving mediators (SPMs) and endocannabinoids, including resolvin D (RvD) 1, maresin (MaR) 1, MaR2, protectin D1 (PD1), protectin DX (PDX), and the endocannabinoids eicosapentaenoyl ethanolamide (EPEA) and docosahexaenoyl ethanolamide (DHEA) in the liver and RvD1, 17R-RvD1, RvD2, RvD3, RvD5, MaR1, MaR2, PD1, PDX, and EPEA and DHEA in the spleen. The spleen was identified as a source of high lipid mediator and SPM formation as lipid mediator concentrations were on average 25-fold higher than in the liver. Additionally, n-3 PUFA-treated primary human MDMs produced RvD5 and the endocannabinoids EPEA and DHEA, which was associated with an increased IL-10 secretion. In contrast, primary human CD4+ T cells showed only an increase in SPM precursors and an increase in the endocannabinoids EPEA and DHEA, which was associated with reduced cytokine expression.

Conclusions: This demonstrates that lipid mediators, particularly SPMs and endocannabinoids from spleen, could play a key role in facilitating the favorable clinical outcomes associated with the use of n-3 PUFA-rich lipid emulsions in TPN.