The role of α-tocopherol in motor hypofunction with aging in α-tocopherol transfer protein knockout mice as assessed by oxidative stress biomarkers

It has been hypothesized that oxidative stress plays a key role in aging. In order to elucidate the role of the antioxidant network - including α-tocopherol (αT) and αT transfer protein - in aging in vivo, α-tocopherol transfer protein knockout (αTTP^-/-) mice were fed a vitamin-E-depleted diet, and wild-type (WT) mice were fed a diet containing 0.002 wt.% αT from the age of 3 months to 1 1/2 years. The lipid oxidation markers total hydroxyoctadecadienoic acid (tHODE) and 8-iso-prostaglandin F₂α, and antioxidant levels in the blood, liver and brain were measured at 3, 6, 12 and 18 months. tHODE levels in the plasma of αTTP^-/- mice were elevated at 6 months compared to 3 months, and were significantly higher those in WT mice, although they decreased thereafter. On the other hand, tHODE levels in the liver and brain were constantly higher in αTTP^-/- mice than in WT mice. Motor activities decreased with aging in both mouse types; however, those in the αTTP^-/- mice were lower than those in the WT mice. It is intriguing to note that motor activities were significantly correlated with the stereoisomer ratio (Z,E/E,E) of HODE, which is a measure of antioxidant capacity in vivo, in the plasma, in the liver and even in the brain, but not with other factors such as antioxidant levels. In summary, using the biomarker tHODE and its stereoisomer ratio, we demonstrated that αT depletion was associated with a decrease in motor function, and that this may be primarily attributable to a decrease in the total antioxidant capacity in vivo.