Abstract :
HDL-phospholipids are determinants in reverse cholesterol transport. They are mostly derived
from triacylglycerol (TG)-rich lipoproteins. Chylomicron size is important, therefore, because it is
related to the ratio surface phospholipids: core TG and, thus, determines the availability of
postprandial phospholipids for transfer to HDL. Eleven healthy young women each ingested four
different fat loads supplemented with retinyl palmitate and containing 60 g sunflower oil (SO), oleic—
sunflower oil (OSO), mixed oil (MO; (g/kg) linoleic acid 480, oleic acid 380, linolenic acid 13) or beef
tallow (BT). At the peak of TG absorption for all loads (4 h) chylomicron diameters, determined by
agarose-gel filtration, were larger after SO compared with OSO (i><0-05) and BT (i>=006) and
after MO compared with BT (P < 0-05). At 6 h chylomicron size was larger after the vegetable oils
compared with BT (P < 0 05 in each case). After each fat load chylomicron size decreased at 6 and
8h compared with that at 4h (P<005) except for OSO. Retinyl ester and TG concentrations were
lower in chylomicrons after BT than after the other fats but not in the chylomicron-free serum
(containing chylomicron remnants), suggesting absorption in the form of very small particles.
Compared with the fasting value, the concentration of the Svedberg unit of flotation 20-400 fraction,
which contains VLDL and chylomicron remnants, was lower 8 h after MO, the only fat to contain
significant amounts of linolenic acid. We conclude that chylomicron size is dependent on the fatty
acid composition of ingested fats and the time-course of digestion, being larger for polyunsaturated
fatty acid-rich fats and in the early phase of digestion. On the basis of retinyl ester concentration
there were no differences between fats in chylomicron-remnant clearance.
