title: 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.
abstract: 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 less than 1.006 g/mL, retinyl ester similarly peaked at 6 hours, whereas triglyceride as well as apoB-48 peaked at 3 hours. Although retinyl esters were found mainly in TRL in the initial postprandial period (84%, 3 hours; 83%, 6 hours), in fasting and postprandial plasma, particularly 9 or more hours after fat-feeding, a large percentage of plasma retinyl esters were in low-density lipoproteins (LDL) (44%, fasting; 9%, 3 hours; 9%, 6 hours; 19%, 9 hours; 32%, 12 hours). A small percentage of retinyl esters were also found in postprandial high-density lipoproteins (HDL) (2% to 7%). ApoB-48 was not detected in LDL of fasting or postprandial plasma.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: US Department of Agriculture Human Nutrition Research Center on Aging, Tufts University, Boston, MA 02111.
authors.forename: S D
authors.initials: SD
authors.lastname: Krasinski
authors.forename: J S
authors.initials: JS
authors.lastname: Cohn
authors.forename: R M
authors.initials: RM
authors.lastname: Russell
authors.forename: E J
authors.initials: EJ
authors.lastname: Schaefer
mesh_terms: D000328:Adult; D000368:Aged; D001057:Apolipoproteins E / Q000097:blood; D015415:Biomarkers / Q000097:blood*; D002784:Cholesterol / Q000097:blood; D002914:Chylomicrons / Q000097:blood*; D004435:Eating; D005260:Female; D006801:Humans; D007408:Intestinal Absorption; D007700:Kinetics; D008074:Lipoproteins / Q000097:blood*; D008297:Male; D008875:Middle Aged; D013997:Time Factors; D014280:Triglycerides / Q000097:blood; D014801:Vitamin A / Q000031:analogs & derivatives / Q000097:blood*
chemical_list: D001057:Apolipoproteins E; D015415:Biomarkers; D002914:Chylomicrons; D008074:Lipoproteins; D014280:Triglycerides; D014801:Vitamin A; D002784:Cholesterol