Effect of intravenous ω-6 and ω-3 fat emulsions on nitrogen retention and protein kinetics in burned rats

The effect of ω-3 fat emulsion on nitrogen retention and kinetics in relation to fatty acid profile were investigated in burned rats receiving total parenteral nutrition (TPN). A fat emulsion of a structured symmetrical triacylglycerol containing only eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) (2:1) was prepared. Sprague-Dawley rats were fed by fat-free chow for 2 wk. Then rats were fed exclusively with one of three types of TPN for 7 d. Animals in group C received fat-free TPN (n = 11). Group ω6 received safflower oil fat emulsion, which accounted for 20% of total caloric intake (n = 11). Group ω3 received fat emulsion containing only EPA and DHA (1% of total calories, n = 11), in addition to safflower oil emulsion (19% of total calories). On day 5, each rat was subjected to 20% full-thickness scald burns. Rats were sacrificed under ether anesthesia 48 h after burning. The rats in group C became deficient in ω-6 essential fatty acids. Cumulative nitrogen balance was decreased significantly in group ω6. The rates of whole-body protein synthesis were increased significantly in both groups ω6 and ω3. In ω6, however, the rates of whole-body protein breakdown were increased significantly. In conclusion, the rates of whole-body protein breakdown increased and nitrogen retention was aggravated significantly in animals administered the safflower oil emulsion. Significant increases of urinary excretion of total catecholamine were also observed. Prostaglandin E2 and thromboxane B2 concentrations were not significantly different among three groups. Supplementation with the new ω-3 fat emulsion, however, improved protein metabolism in burned rats receiving TPN.