Antioxidant and inflammatory biomarkers for the identification of prodromal Parkinson's disease

Objectives: We explored the role of oxidative stress and inflammatory molecules as potential Parkinson (PD) biomarkers and correlated biological with non-motor abnormalities (olfactory impairment and dysautonomia), in patients with idiopathic REM behavior disorder (iRBD) (prodromal PD) and established PD. Methods: We recruited 11 iRBD and 15 patients with idiopathic PD (Hohen&Yahr 1-3, on L-DOPA and dopamine agonists combination therapy) and 12 age- and sex-matched controls (CTRL). We measured total olfactory score (TOS), autonomic function [deep breathing (DB), lying to standing (LS) and Valsalva manoeuvre (VM) ratios], blood reduced glutathione (Br-GSH), oxidative stress and inflammatory markers (neopterin). Results: Anosmia was similarly prevalent in iRBD (36%) and PD (33%) patients, but absent in CTRL Orthostatic hypotension was more common among iRBD (73%) and PD (60%) than in CTRL (25%). By univariable ordinal logistic regression, TOS, Br-GSH, LS and VM ratio worsened from CTRL to iRBD and PD groups. Only reduced Br-GSH levels (p = 0.037, OR = 0.994; 95%CI 0.988-1.000) were independently associated to PD. TOS correlated with Br-GSH (R = 034, p = 0.037), VM ratio (R = 0.43, p = 0.015), and neopterin (rho = 0.39, p = 0.016). Conclusions: Reduced systemic antioxidant capacity is found in prodromal and overt PD and may represent, in association with olfactory loss and cardiovascular dysautonomia, a useful biomarker for an integrative, early diagnosis of PD. (C) 2016 Elsevier B.V. All rights reserved.