Serum Myeloperoxidase Activity Is Associated with Hoehn-Yahr Staging and Striatal Dopamine-Transporter Binding in Parkinson's Disease.

BACKGROUND: The blood concentration of myeloperoxidase (MPO) is related to the severity of many age-related inflammatory diseases. However, it is unknown whether enzyme activity in the blood provides information on the degree of functional disability of Parkinson's disease (PD), a multifactorial disease in which aging and inflammation play an important role. OBJECTIVE: The aim of the study was to discern the relationship between MPO activity in blood serum and the clinical characteristics of PD, assessed by disease rating scales and neuroimaging methods. METHODS: This cross-sectional study included 217 participants (114 patients and 103 controls). Disease rating scales included the Hoehn-Yahr scale, the International Parkinson and Movement Disorder Society-sponsored revision of the Unified Parkinson's Disease Rating Scale motor section (MDS-UPDRS), and the Schwab-England Daily Living scale. The neuroimaging study was based on dopamine transporter single-photon emission computed tomography (DAT-SPECT) and specific binding ratio (SBR) quantification of (123)I-Ioflupane on basal ganglia. RESULTS: The findings revealed that serum MPO activity significantly increased in PD patients (P < 0.0001). MPO activity correlated with the degree of clinical impairment measured with rating scales and with striatal DAT availability assessed with DAT-SPECT. Multivariate linear regression, correcting for all confounding factors, shows that the Hoehn-Yahr staging (P = 0.004) and left striatum specific binding ratio (SBR) (P < 0.05) are predictors of serum MPO activity, along with dysthyroidism and statins use (P < 0.005). MPO activity cutoff greater than 40.350 U/L differentiated patients from controls with good accuracy (78.9%). CONCLUSIONS: In PD, MPO activity in blood serum is associated with the stage of functional disability, apart from dysthyroidism and use of statins, assessed with the Hoehn-Yahr scale and  striatal DAT binding.