Total parenteral nutrition containing medium- vs. long-chain triglyceride emulsions elevates plasma cholesterol concentrations in rats.

Male Fischer 344 rats (235-246 g) were fed for 6-14 d by intravenous or intragastric infusion with total parenteral nutrition (TPN) solutions providing 40 or 65% of nonprotein energy as fat from long-chain triglyceride (LCT) or a 3:1 admixture of medium-chain triglyceride (MCT) and LCT emulsions. In three separate experiments, plasma cholesterol concentrations were significantly greater (24-32%) with intravenous infusion of TPN solutions containing MCT-LCT rather than LCT. Plasma cholesterol concentrations in rats were not significantly different with intragastric infusion of TPN solutions containing MCT-LCT rather than LCT. Hepatic total lipid and triglyceride concentrations were not significantly different. Hepatic total cholesterol and esterified cholesterol concentrations were significantly lower in animals given 65% of energy from MCT-LCT rather than LCT emulsions (main effects, two-way ANOVA). The concentration of individual hepatic acyl-CoA esters reflected the fatty acid profiles of the lipid emulsions infused. Total hepatic acyl-CoA concentrations suggested differences in utilization of acyl-CoA esters with intravenous infusion of MCT-LCT rather than LCT and were consistent with rapid oxidation of MCT. These data demonstrate that MCT-LCT elevates plasma cholesterol concentrations compared with LCT emulsions with intravenous, but not with intragastric, infusion of TPN solutions in rats.