Apolipoprotein E exerts selective and differential control over vitamin E concentrations in different areas of mammalian brain

Apolipoprotein E (apoE) is known to be a risk factor for the incidence of Alzheimer's disease (AD). In addition, vitamin E has been reported to have a role in the treatment of AD. We examined the potential interrelationship between vitamin E and apoE in brain. As the first step, we determined the concentrations of α-tocopherol in selected brain regions of apoE-deficient mice at different ages. The mice were fed normal rodent chow. All regions of the brain in apoE-deficient mice contained less α-tocopherol than control samples at 2.5 months of age, the initial time of study. This trend continued for 9.5 months for most regions except the spinal cord and cerebellum. Tocopherol levels in these latter regions of apoE-deficient animals increased to control levels during the study. Serum α-tocopherol and cholesterol levels were high in the apoE-deficient animals; however, the CNS cholesterol levels were the same in apoE-deficient and control mice. This suggests that 1) the decline in brain α-tocopherol in apoE deficiency is not due to overall alterations in lipid metabolism; and 2) the processing of α-tocopherol in brain follows a separate pathway than that of cholesterol. Subcellular concentrations of α-tocopherol were unaltered by apoE deficiency indicating that intracellular handling of tocopherol is not affected by apoE. ApoE may be an important protein controlling vitamin E levels in specific brain regions. Further understanding of the interactions between apoE and vitamin E could be important in the appropriate use of vitamin E in AD.