A summary of our work: effects of intravenous ω-6 and ω-3 fat emulsions on nitrogen retention and protein kinetics in burned rats

Abstract

The effect of w-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 E 2 and thromboxane B 2 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.