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 en teral administration of eicosapentaenoic acid (EPA) on stress response, cyt okine 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 septi c animals and decreases the immune function. It has also been reported that the administration of fish oil, in contrast, reduces these stress response s and stress-induced immunosuppression. In humans, the effects of soybean o il emulsion and the administration of EPA on stress response and immune fun ction 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 (T PN) with soybean oil emulsion, which accounted for 20% of total calories. S even patients were given oral or enteral administration of 1.8 g/day EPA, i n addition to TPN with soybean oil emulsion. Nine patients served as the co ntrol group; these patients received fat-free IPN. Serum interleukin-6 (IL- 6), C-reactive protein, concanavalin A (con A)- or phytohemagglutinin (PHA) -stimulated lymphocyte proliferation, natural killer cell activity, and str ess hormones were measured. Results The postoperative level of serum IL-6 was significantly higher in t he group receiving soybean oil emulsion than in the fat-free group. Oral or enteral supplementation of EPA with soybean oil emulsion significantly red uced the level of serum IL-6 compared with the patients receiving soybean o il emulsion. Con A or PHA-stimulated lymphocyte proliferation decreased sig nificantly on postoperative day 7 in all groups of patients. The supplement ation of EPA with soybean oil emulsion significantly improved the lymphocyt e proliferation and natural killer cell activity on postoperative day 21 co mpared with the group receiving soybean oil emulsion. Conclusions Soybean oil emulsion amplifies, and the supplementation of EPA reduces, the stress response and stress-induced immumosuppression.