Role of Tocopherol in the Reduction of Mitochondrial NAD

Abstract

Tocopherol deficiency had no effect on phosphate uptake linked to ascorbate–tetramethyl-p-phenylenediamine but did impair energy transfer associated with succinate-linked reduction of NAD. These results suggest that tocopherol deficiency uncouples site 1 but not site 3 related energy transfer.Marked differences were obtained with tocopherol deficiency and methyl linoleate hydroperoxide which showed that the effects of tocopherol deficiency on mitochondrial energy transfer could not be duplicated by in vitro addition of peroxides.Tocopherol administration via the portal vein, 45 min prior to extraction of tissue, reversed the effects of tocopherol deficiency. Intraportal diphenyl-p-phenylenediamine reversed lipid peroxidation but did not substitute for tocopherol in restoration of mitochondrial energy transfer. It was concluded that restoration of antioxidant activity does not assure restoration of energy transfer in tocopherol-deficient mitochondria.These results suggest that there is a specific requirement for tocopherol in succinate-linked reduction of NAD which would imply a cofactor function for tocopherol or a tocopherol-dependent metabolite. It was proposed that coenzyme Q could be a tocopherol-dependent metabolite which is required for energy transfer.