Immune modulation by polyunsaturated fatty acids during nutritional therapy: interactions with synthesis and effects of eicosanoids.

OBJECTIVE: Review of the range of action of polyunsaturated fatty acids (PUFAs) on the basis of interactions with eicosanoids. Discussion of the clinical relevance of these actions. DATA SOURCES: Original papers and reviews of the pertinent literature in German and English, covered by repeated MEDLINE searchers. SELECTION CRITERIA: Pertinent original papers and review articles from 1983 on, as well as some significant original papers of earlier origin with main emphasis on studies concerned with the pharmacodynamic interactions between PUFAs, eicosanoids and the immune system.
RESULTS: PUFAs are precursors of eicosanoid formation. Interactions between PUFAs and the immune system are influenced by the rate of synthesis as well as by the efficacy of the various eicosanoids. The rate of eicosanoid synthesis is determined by PUFA turnover. In the absence of essential fatty acid deficiency (EFAD), PUFA turnover depends on the activity of phospholipases. Activities are enhanced under the influence of stress factors such as trauma and sepsis. The efficacy of eicosanoids is determined by the availability of different PUFAs in the cellular phospholipid pool, whereby n-6 and n-3 PUFAs give rise to eicosanoids of different series. The eicosanoids formed from n-3 PUFAs, compared to those derived from n-6 PUFAs, develop similar quality but less intensity of action. Therefore, eicosanoids of different origin induce different effects at a given rate of synthesis.
CONCLUSIONS: Appropriate dietary alterations of the availability of n-6 and n-3 PUFAs together with the resulting influence on synthesis and action of mediators, possibly might serve as a pharmacological tool to influence systemic functions in critically ill patients in the future.