Even when laced with syrup, cod-liver oil is disgusting, but it is an important source of omega-3-docosapentaenoic fatty acid (DPA). After being swallowed, DPA is converted into specialized proresolving lipid mediators (SPMs), including protectin and resolvin. SPMs are naturally produced by leukocytes and are essential for repairing the damage caused to tissues by inflammation, such as during inflammatory bowel disease (IBD). Gobbetti et al. found that mice with induced IBD have up-regulated protectin and resolvin pathways. If mice were treated with SPMs, their colons lengthened and ulceration was reduced (independently of the anti-inflammatory cytokine interleukin-10). Protectin and resolvin almost appear to lubricate neutrophils by preventing them from sticking to the lining of blood vessels and escaping to invade the colon. The next step is to find out what causes normal inflammatory repair to fail during IBD.
Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1617290114 (2017).