Abstract
It is important to evaluate the metabolism of exogenous lipoproteins because chylomicron remnants have been recognized to be atherogenic. We prepared three kinds of test meal as follows: BI; carbohydrate (C) 63g, protein (P) 18g, long chain triglyceride (LCT) 4.3g. BII; C 53g, P 18g, medium chain triglyceride (MCT) 8g, LCT 5.5g. Bill; C 53g, P 18g, LCT 13.5g. We administered these test meals to four healthy men (mean age 30 yrs.) and obtained their plasma after 0, 1, 2 and 3 hours of loading.
After administration of BI and BII, the apolipoprotein B-48/B-100 ratio in triglyceride rich lipoproteins (TRL, d<1.006), which was determined by analytical SDS polyacrylamide gel electrophoresis, increased to the maximum value after one hour and thereafter rapidly decreased. In contrast, on loading of BIII, this ratio consistently increased during the course of the experiment. Plasma insulin levels behaved like the apo B-48/B-100 ratio: large insulin responses were found after administering BI and BII while the obvious peak of insulin responses was not observed after feeding BIII.
Although the apo B-48/B-100 ratio in TRL decreased after reaching its maximum value, triglyceride levels in TRL continued to increase throughout the period of experiment on BI and BII, reflecting stimulated secretion of endogenous very low density lipoprotein. On the other hand, total cholesterol levels in low density lipoprotein (LDL) decreased after administration of BI and BII probably due to increased activity of LDL receptors during the postprandial phase.
It is worth nothing that the clearance of intestine originated lipoproteins was greatly affected by differences in food composition, especially free fatty acids. It is likely that this metabolic process was mediated through insulin responses.
