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

The effect of omega-3 fat emulsion on nitrogen retention and kinetics in re lation to fatty acid profile were investigated in burned rats receiving tot al parenteral nutrition (TPN). A fat emulsion of a structured symmetrical t riacylglycerol containing only eicosapentaenoic acid (EPA) and docosahexaen oic 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 T PN for 7 d. Animals in group C received fat-free TPN (n = 11). Group omega 6 received safflower oil fat emulsion, which accounted for 20% of total cal oric intake (n = 11). Group omega 3 received fat emulsion containing only E PA and DHA (1% of total calories, n = 11), in addition to safflower oil emu lsion (19% of total calories). On day 5, each rat was subjected to 20% full -thickness scald bums. Rats were sacrificed under ether anesthesia 48 h aft er burning. The rats in group C became deficient in omega-6 essential fatty acids. Cumulative nitrogen balance was decreased significantly in group om ega 6. The rates of whole-body protein synthesis were increased significant ly in both groups omega 6 and omega 3. In omega 6, however, the rates of wh ole-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 emulsio n. Significant increases of urinary excretion of total catecholamine were a lso observed. Prostaglandin E-2 and thromboxane B-2 concentrations were not significantly different among three groups. Supplementation with the new o mega-3 fat emulsion, however, improved protein metabolism in burned rats re ceiving TPN. Nutrition 1999; 15:135-139. (C) Elsevier Science Inc. 1999.