POSTPRANDIAL PLASMA RETINYL ESTER RESPONSE IS GREATER IN OLDER SUBJECTS COMPARED WITH YOUNGER SUBJECTS - EVIDENCE FOR DELAYED PLASMA-CLEARANCE OF INTESTINAL LIPOPROTEINS

Postprandial vitamin A and intestinal lipoprotein metabolism was studied in 86 healthy men and women, aged 19-76 yr. Three independent experiments were carried out. In the first experiment, a supplement dose of vitamin A (3,000 retinol equivalents [RE]) was given without a meal to 59 subjects, aged 22-76 yr. In the second experiment, 20 RE/kg body wt was given with a fat-rich meal (1 g fat/kg body wt) to seven younger subjects (aged < 50 yr) and seven older subjects (aged ≥ 50 yr). In both experiments, postprandial plasma retinyl ester response increased significantly with advancing age (P < 0.05). In the third experiment, retinyl ester-rich plasma was infused intravenously into nine young adult subjects (aged 18-30 yr) and nine elderly subjects (aged ≥ 60 yr), and the rate of retinyl ester disappearance from plasma during the subsequent 3 h was determined. Mean (±SE) plasma retinyl ester residence time was 31±4 min in the young adult subjects vs. 57±8 min in the elderly subjects (P < 0.05). These data are consistent with the concept that increased postprandial plasma retinyl ester concentrations in older subjects are due to delayed plasma clearance of retinyl esters in triglyceride-rich lipoproteins of intestinal origin.