Effects of estrogen/progestin agents on plasma retinoids and chylomicron remnant metabolism.
Women using estrogen-progestin oral contraceptive agents have a marked decrease in the activity of hepatic triglyceride lipase, an enzyme believed to be involved in the catabolism of lipoprotein remnants. The hypothesis that women receiving these agents have defective remnant processing resulting in elevated chylomicron remnant concentrations in plasma was tested. Retinyl esters, which in humans are transported by intestinally-derived lipoproteins, were used to estimate chylomicron and chylomicron remnant concentrations. Women on a variety of oral contraceptive agents had increased plasma triglyceride concentrations, but only minimally increased fasting retinyl ester concentrations. Retinol and retinyl binding protein were elevated to about 150% of controls (p less than 0.001). Retinyl ester concentrations during active fat absorption were then measured in a second group of women taking a single preparation. Three-hour retinyl ester levels were lower in the treated group than control (p less than 0.05), but the difference had disappeared at six hours. Postheparin plasma hepatic triglyceride lipase was reduced by 46% in the treated group (p less than 0.05). Thus despite reduction in hepatic lipase activity, there was no accumulation of retinyl esters in the contraceptive-treated women to suggest impaired remnant processing.
Gleeson, JM; Dukes, CS; Elstad, NL; Chan, IF; Wilson, DE
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