Eating oily fish may reduce inflammation

A new study explains how a diet high in oily fish like salmon and mackerel improves inflammatory conditions, particularly in combination with low doses of aspirin. In a study in the March 7 issue of The Journal of Experimental Medicine, Arita and colleagues identify an anti-inflammatory lipid in humans that is derived from an essential fatty acid in fish oil.

Fatty fish contain large amounts of omega-3 fatty acids–diet-derived essential fatty acids known to benefit patients with cardiovascular disease and arthritis. This research group recently identified a new class of aspirin-triggered bioactive lipids, called resolvins, the activity of which may in part explain the beneficial effects of omega-3 fatty acids. Resolvins are made from the omega-3 fatty acids by cellular enzymes and can reduce inflammation in mice. The main bioactive component of this class of lipids was identified in mice and named resolvin E1.

The researchers have now identified this lipid in plasma taken from volunteers given omega-3 fatty acids and aspirin. Human resolvin E1, the authors show, inhibits both the migration of inflammatory cells to sites of inflammation and the turning on of other inflammatory cells.

This study also reveals a potential pitfall of COX-2 inhibitors, drugs designed to block inflammation, which have been shown to have negative cardiovascular side effects. COX-2 is involved in making resolvin E1 and the authors suggest that inhibition of vascular COX-2 by these inhibitors might block the synthesis of resolvin E1, which would eliminate an important anti-inflammatory pathway. The experiment to prove this idea, however, has yet to be done.