Attenuation of the Febrile Response in Guinea Pigs by Fish Oil Enriched Diets

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Abstract
The influence of dietary lipid manipulation on the fever response to an injection of murine recombinant Interleukin-1 (rIL-1) in guinea pigs was examined. The animals were fed diets identical except for the lipid source for periods of 5 and 6 wk. In vitro thromboxane B2/B3 (TxB2/B3) production in collagen-stimulated whole blood was also measured. One diet was enriched with menhaden oil, high in the omega-3 series of fatty acids. The other diet contained safflower oil, consisting primarily of the omega-6 fatty acid linoleic acid (74%). Animals fed the fish oil-enriched diet for 6 wk not 5 weeks had a blunted fever response after rIL-1 injection. This was associated with a 27% increase (p < 0.05) in total omega-3 fatty acids in plasma phospholipids between weeks 5 and 6 in fish oil-fed animals. Safflower oil-fed animals produced a "normal" febrile response regardless of the duration of feeding. Safflower-fed guinea pigs demonstrated a significant increase in TxB2/B3 production in whole blood after 6 wks that was associated with a 25% increase (p < 0.05) in plasma phospholipid arachidonic acid levels between weeks 5 and 6. Despite significant reductions in phospholipid linoleic acid in animals fed fish oil, arachidonic acid levels remained unchanged. In the guinea pig model used, long-term menhaden oil feeding can significantly blunt the febrile response induced by exogenous Interleukin-1. Also, a high intake of linoleic acid as seen in safflower oil feeding can significantly increase thromboxane production in stimulated whole blood. Thus, the type of fatty acids available at the substrate level could affect the physiologic response to injury and/or infection.