Effects of eicosapentaenoic and γ-linolenic acids (dietary lipids) on pulmonary surfactant composition and function during porcine endotoxemia

Study objectives: To investigate whether a diet enriched with fish and borage oils, with their high polyunsaturated fatty acid (PUFA) content, alters surfactant composition and function during endotoxemia. Design: Prospective, randomized, blinded, controlled animal study. Setting: Research laboratory at a medical center. Participants: Thirty-six 15- to 25-kg, disease-free, castrated male pigs. Diets and measurements: Three groups of pigs (n = 12 per group) were fed for 8 days diets containing either ω-6 fatty acids (FAs) (corn oil; diet A), or ω-3 FAs (fish oil; diet B), or a combination of ω-6 and ω-3 FAs (borage and fish oils; diet C). Eight of 12 pigs in each group received a 0.1-mg/kg bolus of Escherichia coli endotoxin followed by a continuous infusion (0.075 mg/kg/h). One lung was subsequently isolated ex vivo, and pressure-volume curves were measured. The contralateral lung was lavaged, and surfactant was analyzed for total and individual phospholipids and FA composition. Minimum and maximum surface tension was measured by bubble surfactometry. Results: Pigs fed either diet B or C had increased oleic acid (C(18:1) ω-9), eicosapentaenoic acid (EPA; C(20:5) ω- 3), docosahexaenoic acid (C(22:6) ω-3), and total ω-3 and monounsaturated FAs in their surfactant PUFA pools. The relative percentage of linoleic acid (C(18:2) ω-6) and total ω-6 FAs were significantly lower from pigs fed diets B and C compared with diet A. Palmitic acid (C(16:0)) concentrations, the primary FA in surfactant, had a tendency to be lower in pigs fed diets B and C. There were no demonstrable effects on surfactant function or pulmonary compliance. Conclusions: Diets containing EPA or EPA and γ-linolenic acid altered the PUFA composition of pulmonary surfactant, but without demonstrable effects on surfactant function during porcine endotoxemia.