Antioxidants in Alzheimer's disease-vitamin C delivery to a demanding brain

Abstract

Levels of several antioxidants and related markers were measured in cerebrospinal fluid (CSF) and plasma of 10 Alzheimer's disease (AD) patients and 10 controls. Daily dosage of vitamin C was significantly correlated with both plasma (R=0.662; p=0.0015) and CSF level (R=0.639, p=0.0024). Plasma and CSF vitamin C levels were also highly correlated R=0.793, p<0.0001). Similarly, daily dosage of Vitamin E was significantly correlated with plasma vitamin E (R=0.681; p=0.0009) and showed a trend toward correlation with CSF vitamin E (R=0.422, p=0.06).

There were no significant differences between groups in absolute CSF or plasma levels of any analyte. However, the CSF: plasma ratio of vitamin C was significantly greater in the AD patients compared to the controls (p=0.048). In a subset of AD patients, hippocampal volume was significantly correlated with plasma (R²=0.833; p=0.004) and CSF (R² =0.603; p=0.04) vitamin C levels, and inversely correlated with CSF:plasma vitamin C ratio (R² =0.717; p=0.016). We conclude that oral vitamin C supplements are delivered to the brain, and speculate that the increased CSF: plasma ratio of vitamin~C in AD reflects increased antioxidant consumption by the AD brain.