Increased low-density lipoprotein oxidation, but not total plasma protein oxidation, in Alzheimer's disease.

OBJECTIVES: The two most common forms of dementia are Alzheimer's disease (AD), and vascular dementia (VaD). In the overlap of biochemical processes which have been identified in AD and VaD, oxidative stress is believed to contribute to the numerous pathologies of both dementias. DESIGN AND METHODS: This study assessed oxidative damage in total plasma proteins, and isolated LDL in AD patients and age matched controls, in addition total antioxidant capacity (TAC) was measured. RESULTS: Significantly higher LDL protein carbonylation was observed in AD compared to age-matched controls (AD: 4.17+/-0.73 vs. control: 3.85+/-0.86 nmol/mg LDL; p=0.05, 2-tailed Mann-Whitney), in addition to reduced TAC (AD: 924.708+/-174.429 vs. control: 1078.536+/-252.633 microM; p=0.001, 2-tailed Mann-Whitney). No differences were seen in total plasma protein carbonyl content (AD: 3.88+/-0.31 vs. control: 3.98+/-0.48 nmol/mg protein). CONCLUSION: The results further support the view that oxidation events in AD may be specific in nature, and represent functional changes to proteins, rather than random global events.