Effects of soybean oil emulsion and eicosapentaenoic acid on stress response and immune function after a severely stressful operation

OBJECTIVE: To investigate the effects of soybean oil emulsion and oral or enteral administration of eicosapentaenoic acid (EPA) on stress response, cytokine production, protein metabolism, and immune function after surgery for esophageal cancer. SUMMARY BACKGROUND DATA: It has been reported that safflower oil, rich in n-6 polyunsaturated fatty acid (n-6 PUFA), affects the survival rate of septic animals and decreases the immune function. It has also been reported that the administration of fish oil, in contrast, reduces these stress responses and stress-induced immunosuppression. In humans, the effects of soybean oil emulsion and the administration of EPA on stress response and immune function after surgery have not been established. METHODS: Patients who underwent esophagectomy with thoracotomy were divided into three groups. Seven patients were fed by total parenteral nutrition (TPN) with soybean oil emulsion, which accounted for 20% of total calories. Seven patients were given oral or enteral administration of 1.8 g/day EPA, in addition to TPN with soybean oil emulsion. Nine patients served as the control group; these patients received fat-free TPN. Serum interleukin-6 (IL-6), C-reactive protein, concanavalin A (con A)- or phytohemagglutinin (PHA)-stimulated lymphocyte proliferation, natural killer cell activity, and stress hormones were measured. RESULTS: The postoperative level of serum IL-6 was significantly higher in the group receiving soybean oil emulsion than in the fat-free group. Oral or enteral supplementation of EPA with soybean oil emulsion significantly reduced the level of serum IL-6 compared with the patients receiving soybean oil emulsion. Con A- or PHA-stimulated lymphocyte proliferation decreased significantly on postoperative day 7 in all groups of patients. The supplementation of EPA with soybean oil emulsion significantly improved the lymphocyte proliferation and natural killer cell activity on postoperative day 21 compared with the group receiving soybean oil emulsion. CONCLUSIONS: Soybean oil emulsion amplifies, and the supplementation of EPA reduces, the stress response and stress-induced immunosuppression.