Postprandial plasma vitamin A metabolism in humans: A reassessment of the use of plasma retinyl esters as markers for intestinally derived chylomicrons and their remnants

We investigated postprandial vitamin A metabolism by measuring retinyl ester, triglyceride, and apolipoprotein (apo)B-48 in the plasma lipoproteins of human subjects before and after fat-feeding. Following a 14-hour fast, eight healthy subjects (two men, six women, 28 to 79 years) were given a fat-rich meal (1 g fat/kg body weight) containing vitamin A (40 retinol equivalents per kilogram body weight). Blood was collected every 3 hours for 12 hours and lipoproteins were isolated by sequential ultracentrifugation. Mean plasma retinyl ester concentration peaked 6 hours after the fat-rich meal, whereas mean plasma triglyceride peaked at 3 hours. Data obtained from hourly samples in 3 subjects showed that changes in the postprandial plasma concentration of retinyl ester occurred 1 to 2 hours after changes in the plasma triglyceride concentration. In triglyceride-rich lipoproteins (TRL) of d