Mechanisms involved in vitamin E transport by primary enterocytes and in vivo absorption.
It is generally believed that vitamin E is absorbed along with chylomicrons. However, we previously reported that human colon carcinoma Caco-2 cells use dual pathways, apolipoprotein B (apoB)-lipoproteins and HDLs, to transport vitamin E. Here, we used primary enterocytes and rodents to identify in vivo vitamin E absorption pathways. Uptake of [(3)H]alpha-tocopherol by primary rat and mouse enterocytes increased with time and reached a maximum at 1 h. In the absence of exogenous lipid supply, these cells secreted vitamin E with HDL. Lipids induced the secretion of vitamin E with intermediate density lipoproteins, and enterocytes supplemented with lipids and oleic acid secreted vitamin E with chylomicrons. The secretion of vitamin E with HDL was not affected by lipid supply but was enhanced when incubated with HDL. Microsomal triglyceride transfer protein inhibition reduced vitamin E secretion with chylomicrons without affecting its secretion with HDL. Enterocytes from Mttp-deficient mice also secreted less vitamin E with chylomicrons. In vivo absorption of [(3)H]alpha-tocopherol by mice after poloxamer 407 injection to inhibit lipoprotein lipase revealed that vitamin E was associated with triglyceride-rich lipoproteins and small HDLs containing apoB-48 and apoA-I. These studies indicate that enterocytes use two pathways for vitamin E absorption. Absorption with chylomicrons is the major pathway of vitamin E absorption. The HDL pathway may be important when chylomicron assembly is defective and can be exploited to deliver vitamin E without increasing fat consumption.
Anwar
Kamran
K
Molecular and Cellular Biology Program, School of Graduate Studies, State University of New York Downstate Medical Center, Brooklyn, NY 11203, USA.
Iqbal
Jahangir
J
Hussain
M Mahmood
MM
D000818:Animals; D001647:Bile Acids and Salts / Q000502:physiology; D002352:Carrier Proteins / Q000037:antagonists & inhibitors; D020895:Enterocytes / Q000378:metabolism*; D007408:Intestinal Absorption / Q000502:physiology*; D008075:Lipoproteins, HDL / Q000502:physiology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008823:Micelles; D019301:Oleic Acid / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D014810:Vitamin E / Q000378:metabolism*
D001647:Bile Acids and Salts; D002352:Carrier Proteins; D008075:Lipoproteins, HDL; D008823:Micelles; C106092:microsomal triglyceride transfer protein; D014810:Vitamin E; D019301:Oleic Acid