Alteration in lipoprotein composition with intravenous compared to intragastric fat-free feeding in the rat.

Rats were fed continuously for 7 d with fat-free total parenteral nutrition solutions delivered intravenously (IV) or intragastrically (IG) to determine changes in plasma lipoprotein composition due to elimination of intestinal nutrient absorption. IV feeding resulted in significantly lower plasma levels of apoA-I and A-IV, which are synthesized by the intestine, and in a 40% reduction in the weight of intestinal mucosa. Higher apoE levels in plasma, a greater proportion of apoE-enriched HDL1 particles and proportionately more HDL cholesterol were observed in IV- than in IG-fed animals. IV feeding also resulted in lower apoC-II levels in the HDL fraction. These differences in plasma apolipoprotein and HDL composition suggest alterations in lipoprotein metabolism with IV compared to IG feeding in the rat.