Evaluation of salivary heme oxygenase‐1 as a potential biomarker of early Parkinson's disease

ABSTRACT Background and Hypothesis To date, there are no chemical analytes, including biochemical indices of oxidative stress, metabolites of α‐synuclein protein, and differential protein expression patterns on proteomic profiling, for use in clinics as a diagnostic biomarker of idiopathic PD. Objectives Heme oxygenase‐1 has been implicated in the pathogenesis of PD. The objective of this study is to ascertain whether salivary heme oxygenase‐1 may serve as a biomarker for early idiopathic PD. Methods Fifty‐eight PD patients and 59 non‐neurological disease controls were recruited. Levels of heme oxygenase‐1 expression were assayed using enzyme‐linked immunosorbent assay and western blot analysis of whole, unstimulated saliva. Analyses were adjusted by sex, l ‐dopa exposure, and relevant comorbidities. Results We documented: (1) the presence of 32‐kDa heme oxygenase‐1 protein in human saliva; (2) significantly higher mean heme oxygenase‐1 protein concentrations in saliva of PD patients relative to control values; (3) no variability in salivary heme oxygenase‐1 levels with sex, age, l ‐dopa equivalence, or comorbidities; and (4) significantly higher mean salivary heme oxygenase‐1 concentrations in patients with H & Y stage 1 PD (early) than control subjects and stage 2 and stage 3 PD patients. The area under the receiver operating characteristic curve that separated controls from PD H & Y stage 1 was 76% (95% confidence interval: 63‐90). Conclusions Salivary heme oxygenase‐1 concentrations may provide a useful, noninvasive, and relatively inexpensive biomarker of early idiopathic PD. © 2018 International Parkinson and Movement Disorder Society