POSTPRANDIAL LIPEMIA IS ASSOCIATED WITH INCREASED LEVELS OF APOLIPOPROTEIN A-IV IN THE TRIACYLGLYCEROL-RICH FRACTION AND DECREASED LEVELS IN THE DENSER PLASMA FRACTIONS

Apolipoprotein (apo) A-IV is primarily associated with HDL or with the lipoprotein-free fraction of plasma, and in small amounts with chylom icrons and VLDL. The aim of the present study was to assess the effect of a fatty meal on the postprandial variation in plasma apo A-IV and on its distribution among lipoprotein fractions following absorption o f fat. Twenty healthy male subjects participated in the study. After a n overnight fast, subjects were given a fatty breakfast containing 1 g fat/kg body weight (% energy: fat 65, carbohydrate 20, protein 15). B lood samples were taken every hour during the next 10 h. Apo A-IV was measured by ELISA. Postprandial lipaemia was associated with a moderat e, although significant, increase in the plasma levels of apo A-IV. Ap o A-IV increased from the median baseline value of 0.15 g/l to 0.165 g /l (median + 17 %; P < 0.01) 5 h after fat ingestion. The postprandial peak of apo A-IV occurred 1 h after the triacylglycerol peak. There w ere no statistically significant correlations between baseline lipids, baseline apo A-IV and postprandial changes in apo A-IV levels, or bet ween postprandial changes in lipids and apo A-IV at any time. To asses s apo A-IV distribution among lipoproteins, plasma was fractionated by fast performance liquid chromatography at baseline and 3, 6 and 10 h postprandially. There was a substantial heterogeneity in the apo A-IV distribution among lipoproteins following the fatty meal. At 3 h after fat ingestion, apo A-IV levels increased in the triacylglycerol-rich lipoprotein (TRL) fraction and decreased in the denser plasma fraction . At 6 h after the fatty meal, apo A-IV was still present in the TRL b ut was decreased in the HDL fractions. The findings of the present stu dy support the concept that apo A-IV particles transfer from the dense r plasma fraction to TRL during postprandial lipaemia.