Urinary 8-hydroxy-2′-deoxyguanosine level and plasma paraoxonase 1 activity with Alzheimer's disease

Background: Alzheimer's disease (AD) is the most frequent cause of dementia and age is the most important risk factor for AD. Aging is associated with increased free radical production and oxidative stress plays an important role in the pathogenesis of AD. 8-Hydroxy-2'-deoxyguanosine (8-OHdG) is a biomarker indicating oxidative DNA damage. Parakonase 1 (PON1) is a high-density lipoprotein (HDL)-associated antioxidant enzyme and prevents especially oxidation of low-density lipoproteins. The aim of this study is to measure urinary 8-OHdG levels and serum PON1 activity in patients with AD. Methods: A total of 21 elderly patients diagnosed with moderate AD (10 men and 11 women, aged 76+/-7.8 years) were included in the study. A total of 20 healthy elderly volunteers (11 men and nine women, aged 81+/-7.2 years) were enrolled as a control group. Levels of urinary 8-OHdG, serum PON1 activity and lipid profile were determined in patients and controls. Results: Urinary 8-OHdG levels were significantly increased, but serum PON1 activity was significantly decreased in patients compared to controls. Lipid profile did not show a difference between the groups. There was a negative correlation between 8-OHdG levels and PON1 activity only in the patient group (r=-0.536). Analytical performance characteristics of the methods used were satisfactory. Conclusions: In this study, evidence of increased oxidative DNA damage was determined in AD patients as well as decreased serum PON1 activity. Oxidant stress and oxidative DNA damage are important pathological processes in AD. The biomarkers, urinary 8-OHdG level and serum PON1 activity can be used to determine and monitor the status of patients with AD.