Brains of apolipoprotein E deficient mice fed vitamin E deficient diets show alteration in handling alpha tocopherol injected into the cerebral ventricles

Abnormal function of apolipoprotein E (apoE) has been implicated in the incidence of some neurological disorders including dementia. Our recent experiments have shown that apoE deficiency alters the dynamics of alpha tocopherol (vitamin E) handling by brain. In the current investigation, we examined the uptake and retention of tritium-labeled alpha tocopherol that was injected into the lateral cerebral ventricles of apoE-deficient and wild type mice that were fed vitamin E-deficient diet. Eighteen weeks-old, male mice were fed vitamin E-deficient diets for 28 weeks. Labeled cholesterol was injected with the radioactive tocopherol and the cholesterol counts were used as internal standard. After an equilibration time of 48 h, radioactive alpha tocopherol levels in most brain regions were higher in apoE deficient animals when compared with the wild type. Along with our other data, this suggests that the clearance of vitamin E is slower in apoE-deficient brains. Nearly all of the injected alpha tocopherol was unchanged in the brains of both apoE-deficient and wild type animals (even with the additional dietary stress of vitamin E deficiency) suggesting low turnover rate of tocopherol in brain. The data strongly suggest that apoE is a key protein involved with the transport and/or retention of alpha tocopherol in brain.