Catabolism of newly formed triglyceride-rich lipoproteins and serum high density lipoproteins in rats fed soybean phospholipid and soybean oil.

Previous research has shown that serum cholesterol and apolipoprotein (apo) A-I were lower and serum apoB was higher in rats fed soybean phospholipid (PL) than in rats fed soybean oil. Secretion of cholesterol and apoA-I, but not apoB, from the liver and intestine was lower in rats fed soybean PL. In the present study catabolism of newly formed triglyceride (TG)-rich lipoproteins, from the liver and intestine, and of serum high density lipoproteins (HDL) were compared in rats fed soybean PL and in rats fed soybean oil. The following results were seen: Feeding of soybean PL was related to more TG and less cholesterol in intestinal lymph chylomicrons (CM) and hepatic very low density lipoproteins (VLDL) than was feeding of soybean oil. A lesser amount of the TG, labeled with [3H]oleate in CM and hepatic VLDL, was incorporated into the adipose tissue and muscle in vivo. The clearance of CM-TG from plasma was higher, but that of VLDL-TG and apoB labeled with [3H]lysine was lower. The catabolism of 125I-labeled HDL from the plasma was lower while hepatic uptake of 125I-labeled HDL, in vivo and in vitro, was higher. These results indicate that soybean PL modifies the catabolism of the respective serum lipoproteins. Therefore, we suggest that changes in both the catabolism and secretion of lipoproteins are responsible for the altered serum lipid and apolipoprotein patterns found in rats fed soybean PL.