Effects of intravenous phospholipid on low density lipoprotein turnover in man.

The mechanism of the rise in plasma low density lipoprotein (LDL) levels following intravenous administration of a triglyceride-phospholipid emulsion (Intralipid) has been investigated by measuring LDL turnover in eight healthy subjects. The plasma half-life, and the absolute and fractional catabolic rates of LDL protein (apo-LDL) were unaffected by intragastric Intralipid, whereas apo-LDL half-life was prolonged and its fractional catabolic rate was decreased by intravenous Intralipid. Similar changes were observed after intravenous administration of the egg phospholipid constituent of Intralipid. Accompanying increases in the oleate: linoleate ratio of both high and low density lipoprotein cholesterol esters were secondary to phospholipid exchange between infused and endogenous lecithin. These results suggest that the increased concentration of LDL in plasma following intravenous administration of egg phospholipid-containing emulsions was due, at least in part, to a decrease in the fractional catabolic rate of apo-LDL. The data further suggest a possible relationship between apo-LDL catabolism and the fatty acid composition of LDL.