THE EFFECT OF INCREASING LEVELS OF FISH OIL CONTAINING STRUCTURED TRIGLYCERIDES ON PROTEIN-METABOLISM IN PARENTERALLY FED RATS STRESSED BY BURN PLUS ENDOTOXIN

This report investigates the effect of various levels of medium-chain/ fish oil structured triglycerides on protein and energy metabolism in hypermetabolic rats. Male Sprague-Dawley rats (192 to 226 g) were cont inuously infused with isovolemic diets that provided 200 kcal/kg per d ay and 2 g of amino acid nitrogen per kilogram per day. The percentage of nonnitrogen calories as structured triglyceride was varied: no fat , 5%, 15%, or 30%. A 30% long-chain triglyceride diet was also provide d as a control to compare the protein-sparing abilities of these two t ypes of fat. Nitrogen excretion, plasma albumin, plasma triglycerides, and whole-body and liver and muscle protein kinetics were determined after 3 days of feeding. Whole-body protein breakdown, flux, and oxida tion were similar in all groups. The 15% structured triglyceride diet maximized whole-body protein synthesis (p < .05). Liver fractional syn thetic rate was significantly greater in animals receiving 5% of nonpr otein calories as structured triglyceride (p < .05). Muscle fractional synthetic rate was unchanged. Plasma triglycerides were markedly elev ated in the 30% structured triglyceride-fed rats. The 30% structured t riglyceride diet maintained plasma albumin levels better than those di ets containing no fat, 5% medium-chain triglyceride/fish oil structure d triglycerides, or 30% long-chain triglycerides. Nitrogen excretion w as lower in animals receiving 30% of nonnitrogen calories as a structu red triglyceride than in those receiving 30% as long-chain triglycerid es, but this difference did not reach statistical significance (p = .1 ). These data suggest that protein metabolism is optimized when struct ured triglyceride is provided at relatively low dietary fat intakes.