Select dietary fatty acids attenuate cardiopulmonary dysfunction during acute lung injury in pigs

We examined the effect of substituting linoleic acid (LA) with eicosapentaenoic acid (EPA) and γ-linolenic acid (γ-LA), precursors of trienoic and monoenoic eicosanoids, respectively, on acute lung injury (ALI). Three groups (n = 8/group) of pigs were fed enteral diets containing LA (diet A), EPA (diet B), or EPA + γ-LA (diet C) for 8 days. ALI was then induced with a 0.1 mg/kg bolus of Escherichia coli endotoxin followed by a continuous infusion for 4 h (0.075 mg · kg^-1 · h^-1). Pulmonary arterial and capillary wedge pressures, cardiac index (CI), arterial blood gases, arterial O₂ content, and plasma thromboxane B₂ (TxB₂) were measured. Arterial PO₂ decreased at 20 min in animals fed diet A. This change was attenuated with diets B and C. The EPA- and EPA + γ-LA-enriched diets attenuated the fall in O₂ delivery at 20 min, an improvement that was sustained throughout the 4-h study period with the EPA + γ-LA-enriched diet only. This improvement in O₂ delivery was due not only to the improved arterial PO₂, but also to the maintenance of CI at 20 min in animals fed diets B and C and throughout the 4-h study period in animals fed diet C. At 4 h, TxB₂ increased 10-fold over baseline in animals fed diet A, whereas in animals fed diets B and C the increase was only 3-fold. These decreased TxB₂ levels in animals fed diets B and C correlate with an attenuation in the increase in pulmonary vascular resistance that was observed at 20 min after endotoxin infusion in animals fed diet A. These data suggest that specialized enteral diets enriched in EPA + γ-LA improve gas exchange and O₂ delivery, presumably in part through a modification of TxB₂ production with a decrease in pulmonary vascular resistance and an increase in CI, during ALI.