Δ-Aminolevulinate dehydratase and glutathione peroxidase activity in Alzheimer's disease

Alzheimer’s disease (AD) is a neurodegenerative pathology that affects elderly people all over the world. Several studies have demonstrated that oxidative stress is an aggravating factor for AD development and progression. Therefore, this study aimed to evaluate the activity of two oxidative stress markers, glutathione peroxidase (GPx) and δ -aminolevulinate dehydratase ( δ -ALA-D), as well as correlate them with blood metal levels and AD progression. For this purpose, 88 elderly individuals were divided in two groups: AD group (34 patients diagnosed with AD) and control group (34 subjects paired by age with the AD group). The Mini-Mental State Examination and the Clinical Dementia Rating (CDR ) were used as tools to classify the AD progression. GPx and δ -ALA-D activities were measured in all subjects through blood tests. Both enzymes’ activities were decreased in AD patients when compared to the age-matched control group, regardless of the CDR. Moreover, GPx activity was positively correlated with selenium levels in the blood; and the δ -ALA-D activity was negatively correlated with blood cop- per levels. Taken together, our results indicated that, for the first time, blood δ -ALA-D activity was significantly inhibited in AD patients. While literature reports conflicting data regarding GPx activity in AD patients, the δ - ALA-D activity seems to be a more consistent tool to be applied as an earlier AD marker