Antioxidant defences and oxidative stress markers in erythrocytes and plasma from normally nourished elderly Alzheimer patients

Objectives: to investigate blood markers of oxidative stress, and enzymatic and non-enzymatic antioxidants in normally nourished elderly people with Alzheimer's disease. Design: case-control study. Subjects: twenty patients with Alzheimer's disease and 23 elderly control subjects, living at home, free from disease and not undergoing any treatment known to have a strong influence on blood oxidative stress markers or antioxidant defence systems. Methods: we performed a nutritional evaluation, including anthropometric and biological measures and a 3-day dietary record. We determined concentrations of antioxidant vitamins (alpha -tocopherol, retinol) and malondialdehyde in plasma and erythrocytes. We also measured erythrocyte enzymatic activities of glutathione peroxidase and copper-zinc superoxide dismutase. Results: the two groups were similar in age, body, mass index, dietary record and serum albumin concentration. After adjustment for age, sex and cardiovascular co-morbidity, mean plasma concentration of alpha -tocopherol was lower in those with Alzheimer disease than in control subjects (15 +/- 3.5 mg/l compared with 18.2 +/- 3.5; P=0.002), as was the mean plasma concentration of retinol (0.54 +/-0.2 mg/l ts 0.7 +/-0.2; P=0.014). The mean concentration of free plasma malondialdehyde was higher in those with Alzheimer's disease (0.70 +/-0.2 mmol/l is 0.5 +/-0.1; P=0.036). In Alzheimer disease patients, free plasma malondialdehyde concentrations were inversely correlated with levels of alpha -tocopherol (P=0.002) and retinol (P=0.025). Erythrocyte levels of vitamins and enzymatic activities were similar in the two groups. Conclusion: lower plasma concentrations of alpha -tocopherol and retinol in normally nourished elderly patients with Alzheimer's disease than in controls could suggest that these antioxidant vitamins had been consumed as a result of excessive production of free radicals.