Positive Association of Ascorbate and Inverse Association of Urate with Cognitive Function in People with Parkinson’s Disease

• Published in: Antioxidants 2020-10, Vol.9 (10), p.906
• Main Authors: Spencer, Emma S., Pitcher, Toni, Veron, Gabriel, Hannam, Tracey, MacAskill, Michael, Anderson, Tim, Dalrymple-Alford, John, Carr, Anitra C.
• Format: Article
• Language: English
• Subjects: Alzheimer's disease; Antioxidants; ascorbate; Ascorbic acid; Brain research; Carbonyl compounds; Cognition & reasoning; Cognitive ability; cognitive impairment; Dementia; Dementia disorders; Health aspects; MoCA; Movement disorders; Neurodegenerative diseases; Neurological diseases; Neuropsychology; Oxidative stress; Parkinson disease; Parkinson's disease; Physiological aspects; Plasma; Proteins; Quality of life; Software; Uric acid; Vitamin C
• ISSN: 2076-3921; 2076-3921
• DOI: 10.3390/antiox9100906

Oxidative stress is thought to contribute to the aetiology of neurological disorders such as Parkinson’s disease. Ascorbate (vitamin C) is a potent antioxidant and is associated with neurological and cognitive function. In this study we assessed the ascorbate status of a cohort of people with Parkinson’s disease (n = 215), aged 50–90 years, compared with a cohort of age matched healthy controls (n = 48). The study sample’s cognitive status ranged from normal to mild cognitive impairment and dementia. There was no difference between the Parkinson’s disease and healthy control groups with respect to mean ascorbate status, however, a higher proportion of participants with Parkinson’s disease had hypovitaminosis C (i.e., 23 µmol/L (p = 0.014). Ascorbate concentrations were significantly lower in the cognitively impaired subgroup compared with the normal cognition subgroup in the Parkinson’s disease cohort (p = 0.03). In contrast, urate showed an inverse correlation with cognitive function (r = −0.19, p = 0.007), with higher urate concentrations observed in the cognitively impaired subgroup compared with the normal cognition subgroup (p = 0.015). There was an inverse association between ascorbate status and urate concentrations (r = −0.15, p = 0.017). Plasma protein carbonyls, a measure of systemic oxidative stress, were not significantly different between the Parkinson’s disease cohort and healthy controls, and there was no association with cognitive function (r = 0.09, p = 0.19) or with ascorbate status (r = −0.05, p = 0.45). Overall, our study showed ascorbate status was positively associated with cognitive function in Parkinson’s disease, suggesting that longitudinal studies investigating the temporal sequence of cognitive decline and ascorbate status are warranted.