Plasma lipoprotein distribution, faecal cholesterol excretion, and activities of lipoprotein lipase, hepatic lipase and lecithin:cholesterol acyltransferase in rats fed diets rich in sucrose or sunflower oil.

Plasma HDL2 has been suggested to carry cholesterol to the liver for subsequent excretion in the bile and faeces. The enzymes lipoprotein lipase (LPL), hepatic lipase (HL) and lecithin:cholesterol acyltransferase (LCAT) have been implicated in the centripetal cholesterol transport. Activities of these enzymes, the amount of faecal cholesterol excretion and the level of plasma lipoproteins were determined in male rats fed for 4 weeks on purified diets in which the sunflower oil:sucrose ratio was either 0.03 (group a) or 1.01 (group b). Whole plasma triacylglycerols (TG), unesterified cholesterol (UC) and phospholipids (PL) were highest in group (a). The concentration of cholesteryl esters (CE) was similar in the two groups. Protein, TG and UC of VLDL, and TG, UC, CE and PL of HDL2 were higher in group (a) than in group (b). The HDL3-protein and TG were lowest in group (a). Thus, total weight of VLDL and HDL2 were increased, and HDL3 reduced in group (a), which had also increased activities of HL and adipose tissue LPL. Activity of LCAT was lower, and faecal excretion of cholesterol was reduced by about 50% in group (a) compared to group (b). Accordingly, in the rat increased plasma levels of HDL2 are not necessarily indicative of increased faecal cholesterol excretion.