Effects of endotoxin on pigs prefed ω-3 vs. ω-6 fatty acid-enriched diets

We investigated in a porcine model whether ω-3 fatty acids modify the physiological response to sepsis. For 8 days, 16 male pigs were fed a diet containing 18% fat by weight enriched with either ω-3 or ω-6 fatty acids (FA). A group of six pigs receiving their regular diet served as controls. The ω-3 FA-supplemented pigs had elevated levels of ω-3 FA in their serum- free FA, serum phospholipid (PL), and platelet PL levels compared with either of the other groups. On the ninth day, the unanesthetized pigs were injected with 0.3 mg/kg of endotoxin (Escherichia coli) intravenously. The animals had a significant decrease in their arterial O₂ pressure (Pa(O₂)) [from 84.4 ± 6.8 (SD) to 64 ± 9.4, and from 83.1 ± 7.2 to 55.9 ± 6.3 mmHg in the ω-6 FA and regular diet groups, respectively]. The Pa(O₂) did not decrease in the ω-3 FA pigs. The ω-3 FA group had significantly lower pulmonary vascular resistance (541 ± 205 dyn · s · cm^-5) 20 min after endotoxin compared with either the ω-6 FA or regular diet groups (797 ± 233 and 1.102 ± 552 dyn · s · cm^-5, respectively) and more normal blood pressure compared with the other two groups. Plasma thromboxane (Tx) B₂ and 6- ketoprostaglandin F(1α) (6-keto-PGF(1α)) levels were lowest in the ω-3 FA diet group and highest in the regular diet group. The fall in Pa(O₂) was correlated with changes in plasma levels of TxB₂ measured at the same time as the Pa(O₂) (r = -0.64, P < 0.02) and with changes in plasma levels of 6- keto-PGF(1α) (r = -0.51, P < 0.05). It is possible with a short-term diet containing high amounts of ω-3 FA to increase plasma and platelet concentrations of ω-3 FA. These diets reduced the rise in plasma eicosanoid levels and maintained arterial oxygenation, arterial blood pressure, and more normal pulmonary vascular resistance in response to intravenous endotoxin.