IMPAIRED ABILITY OF PATIENTS WITH FAMILIAL ISOLATED VITAMIN-E-DEFICIENCY TO INCORPORATE ALPHA-TOCOPHEROL INTO LIPOPROTEINS SECRETED BY THE LIVER

Plasma and lipoprotein α-tocopherol concentrations of four patients with familial isolated vitamin E deficiency and six control subjects were observed for 4 d after an oral dose (~15 mg) of RRR-α-tocopheryl acetate labeled with six deuterium atoms (d6-tocopherol). Chylomicron d6-tocopherol concentrations were similar in the two groups. d6-Tocopherol concentrations of plasma, very low (VLDL), low (LDL), and high (HDL) density lipoproteins were similar in the two groups only during the first 12 h; then these were significantly lower, and the rate of disappearance faster, in the patients. The times (t(max)) of the maximum chylomicron d6-tocopherol concentrations were similar for the two groups, but t(max) values in the controls increased in the order: chylomicrons < VLDL ≤ LDL ~ HDL, while the corresponding values in the patients were similar to the chylomicron t(max). Thus, plasma d6-tocopherol in controls increased during chylomicron and VLDL catabolism, whereas in patients it increased only during chylomicron catabolism, thereby resulting in a premature and faster decline in the plasma tocopherol concentration due to a lack of d6-tocopherol secretion from the liver. We suggest that these patients are lacking or have a defective liver 'tocopherol binding protein' that incroporates α-tocopherol into nascent VLDL.