Influence of vascular comorbidities on the antioxidant defense system in Alzheimer's disease

Background and aim: Oxidative stress is a critical factor in the pathophysiology of dementia, but the role of oxidant/antioxidant imbalance in relation to vascular pathology in the onset and progression of Alzheimer's disease (AD) is poorly understood. The aim of this study was the identification of an association between vascular comorbidities/vascular risk factors and plasma levels of antioxidant micronutrients in patients with AD. Patients and methods: 41 patients with AD and 34 controls were included in the study. Atherosclerosis (increased intima-media thickness of the common carotid artery) and/or type 2 diabetes mellitus were diagnosed in 21 AD patients (AD Plus group). 20 patients with AD were free of vascular comorbidities and risk factors (AD group). A neuropsychological assessment (Mini-Mental State Examination, MMSE; Clock drawing test; DemTect) and the measurement of plasma levels of lipophilic micronutrients including retinol (vitamin A), alpha-tocopherol (vitamin E), lutein, zeaxanthin, beta-cryptoxanthin, lycopene, alpha-carotene and beta-carotene by HPLC were performed in all study subjects. Results: Plasma levels of retinol, vitamin E, lutein, zeaxanthin, lycopene and beta-carotene were significantly lower in the AD Plus group than in controls. Furthermore, vitamin A levels were correlated with MMSE scores and the levels of vitamin E, lutein, zeaxanthin and lycopene were correlated with all neuropsychological tests. Conclusion: The depletion of circulating antioxidant micronutrients observed in AD patients is associated with vascular comorbidities and risk factors. The vascular comorbidities of patients with AD should also be identified in light of the presence and degree of depletion of the antioxidant defense system of the organism. This might lead to a better lifestyle-related counselling of patients with AD and their caregivers, with possible positive preventive effects on worsening in the long run. Further studies with a larger patient sample are needed to verify the negative effect of vascular pathology in AD-related oxidative stress.