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.