Evidence of increased oxidative damage in subjects with mild cognitive impairment.

OBJECTIVE To determine if increased levels of oxidative damage are present in the brains of persons with mild cognitive impairment (MCI), a condition that often precedes Alzheimer disease (AD). METHODS The authors assessed the amount of protein carbonyls, thiobarbituric acid-reactive substances (TBARS), and malondialdehyde in the superior and middle temporal gyri (SMTG) and cerebellum of short postmortem interval and longitudinally evaluated normal subjects and those with MCI and early AD. RESULTS Elevated levels of protein carbonyls (approximately 25%), malondialdehyde (approximately 60%), and TBARS (approximately 210%) were observed in the SMTG of individuals with MCI and early AD vs normal control subjects. The elevation in TBARS was associated with the numbers of neuritic but not diffuse plaques. Levels of protein carbonyls increased as delayed verbal memory performance declined. CONCLUSION Oxidative damage occurs in the brain of subjects with mild cognitive impairment, suggesting that oxidative damage may be one of the earliest events in the onset and progression of Alzheimer disease.