ANTIOXIDANT DEFENSE SYSTEMS IN THE BRAINS OF TYPE-II DIABETIC MICE

The specific activities of superoxide dismutase, catalase, and glutath ione S-transferase (mu subtype) were significantly lower in the brains of mice with type II diabetes than in the brains of control mice. On the other hand, the specific activity of glutathione peroxidase was un altered. The concentration of vitamin E, but not that of total glutath ione and ascorbate, was increased in the brains of the type II diabeti c mice. The relative amount of polyunsaturated fatty acids (as determi ned with soybean lipoxygenase) was increased in whole brains and crude synaptosomal membranes of the type II diabetic mice. Endogenous level s of thiobarbituric acid-positive material were decreased in both whol e brain homogenates and crude synaptosomal membranes of the db/db mice . Susceptibility of lipids within whole brain homogenates and crude sy naptosomal membranes of mice with type II diabetes to peroxidation wit h iron/ascorbate was also markedly decreased compared with that of con trols. Vitamin E is known to quench lipid peroxidation. Therefore, dec reased lipid peroxidation in the type II mouse brain may be due to inc reased vitamin E content.