Liver alpha-tocopherol transfer protein and its mRNA are differentially altered by dietary vitamin E deficiency and protein insufficiency in rats

To study how the expression of alpha-tocopherol transfer protein (alpha-TTP) and its mRNA are affected by protein and vitamin E status, Long-Evans male weanling rats were fed a vitamin E-deficient (DE), high vitamin E (HE, 5 g/kg diet of all-rac-alpha-tocopheryl acetate) or control (C) diet for 12 wk in Experiment 1; and fed a low-protein (LP) or control (C) diet for 6 wk in Experiment 2. The high and deficient vitamin E status of HE and DE groups in Experiment 1 were confirmed by changes in plasma pyruvate kinase activity as well as the concentrations of alpha-tocopherol in plasma and liver. As shown by the Northern and Western Blot Analysis, the expression of alpha-TTP in the liver of the DE group was significantly lower than, while that of the HE group was not different from, that of the controls. In contrast, the alpha-TTP mRNA levels did not differ among the C, DE and HE groups. alpha-Tocopherol in most peripheral tissues of rats fed the LP diet in Experiment 2 was significantly lower than that of the C. Both the alpha-TTP and its mRNA were significantly lower in the LP group than in the C. The results suggested that dietary vitamin E does not affect alpha-TTP gene expression except that the protein levels in the liver were lowered by vitamin E deficiency. On the other hand, protein inadequacy appeared to down-regulate the expression of the alpha-TTP gene.