出版社：American Society for Biochemistry and Molecular Biology
摘要：It is generally believed that vitamin E is absorbed along withchylomicrons. However, we previously reported that human coloncarcinoma Caco-2 cells use dual pathways, apolipoprotein B (apoB)-lipoproteinsand HDLs, to transport vitamin E. Here, we used primary enterocytesand rodents to identify in vivo vitamin E absorption pathways.Uptake of [3H]-tocopherol by primary rat and mouse enterocytesincreased with time and reached a maximum at 1 h. In the absenceof exogenous lipid supply, these cells secreted vitamin E withHDL. Lipids induced the secretion of vitamin E with intermediatedensity lipoproteins, and enterocytes supplemented with lipidsand oleic acid secreted vitamin E with chylomicrons. The secretionof vitamin E with HDL was not affected by lipid supply but wasenhanced when incubated with HDL. Microsomal triglyceride transferprotein inhibition reduced vitamin E secretion with chylomicronswithout affecting its secretion with HDL. Enterocytes from Mttp-deficientmice also secreted less vitamin E with chylomicrons. In vivoabsorption of [3H]-tocopherol by mice after poloxamer 407 injectionto inhibit lipoprotein lipase revealed that vitamin E was associatedwith triglyceride-rich lipoproteins and small HDLs containingapoB-48 and apoA-I. These studies indicate that enterocytesuse two pathways for vitamin E absorption. Absorption with chylomicronsis the major pathway of vitamin E absorption. The HDL pathwaymay be important when chylomicron assembly is defective andcan be exploited to deliver vitamin E without increasing fatconsumption.Supplementary key words lipoproteins • tocopherol • HDL • chylomicrons • oleic acid
Abbreviations: apoA-I, apolipoprotein A-I; FPLC, fast-performance liquid chromatography; IDL, intermediate density lipoprotein; MTP, microsomal triglyceride transfer protein; OA, oleic acid; P407, poloxamer 407; pIpC, polyinosinic-polycytidylic ribonucleic acid
-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 [3H]
