Administration of Structured Lipid Composed of MCT and Fish Oil Reduces Net Protein Catabolism in Enterally Fed Burned Rats

Abstract

The effects of enteral feeding with safflower oil or a structured lipid (SL) derived from 60% medium-chain triglyceride (MCT) and 40% fish oil (MCT/fish oil) on protein and energy metabolism were compared in gastrostomy-fed burned rats (30% body surface area) by measuring oxygen consumption, carbon dioxide production, nitrogen balance, total liver protein, whole-body leucine kinetics, and rectus muscle and liver protein fractional synthetic rates (FSR, %/day). Male Sprague-Dawley rats (195 .+-. 5 g) received 50 ml/day of an enteral regimen containing 50 kcal, 2 g amino acids, and 40% nonprotein calories as lipid for three days. Protein kinetics were estimated by using a continuous L-[1-14C] leucine infusion technique on day 2. Thermally injured rats enterally fed MCT/fish oil yielded significantly higher daily and cumulative nitrogen balances (p .ltoreq. 0.025) and rectus muscle (39%) FSR (p .ltoreq. 0.05) when compared with safflower oil. MCT/fish oil showed a 22% decrease (p .ltoreq. 0.005) in percent flux oxidized and a 7% (p .ltoreq. 0.05) decrease in total energy expenditure (TEE) versus safflower oil. A 15% increase in liver FSR was accompanied by a significant elevation (p .ltoreq. 0.025) in total liver protein with MCT/fish oil. This novel SL shares the properties of other structured lipids in that it reduces the net protein catabolic effects of burn injury, in part, by influencing tissue protein synthetic rates. The reduction in TEE in unique to MCT/fish oil and may relate to the ability of fish oil to diminish the injury response.