Increased bilirubin levels in de novo Parkinson's disease.
OBJECTIVE
Oxidative stress is a central pathogenic mechanism of Parkinson's disease (PD), and the heme oxygenase (HO) bilirubin pathway is one of the main mammalian antioxidative defences. Indeed, there is growing evidence of HO-bilirubin upregulation from early phases of PD. Our aim was to investigate bilirubin as a possible biomarker of PD diagnosis and progression.


METHODS
A cross-sectional case-control study was performed to evaluate differences in bilirubin levels between newly diagnosed, drug-naïve PD subjects and controls. Afterwards, PD subjects were included in a 2-year longitudinal study to evaluate disease progression in relation to baseline bilirubin levels.


RESULTS
Seventy-five de novo PD subjects were selected and matched with 75 controls by propensity score. Analysis of variance showed higher bilirubin levels in PD patients compared with controls (P < 0.001). Linear regression analysis failed to show a relationship between bilirubin and Unified Parkinson's Disease Rating Scale (UPDRS) part III (P = 0.283) at baseline evaluation. At 2-year follow-up, indirect relationships between bilirubin levels and UPDRS part III (P = 0.028) and between bilirubin levels and levodopa-equivalent daily dosage (P = 0.012) were found.


CONCLUSIONS
Parkinson's disease subjects showed higher levels of bilirubin compared with controls. Bilirubin increase might be due to HO overexpression as a compensatory response to oxidative stress occurring from early stages of PD.
Department of Neuroscience, Reproductive Science and Odontostomatology, Federico II University, Naples, Italy.
M
M
Moccia
M
M
Picillo
R
R
Erro
K
K
Longo
M
M
Amboni
G
G
Santangelo
R
R
Palladino
R
R
Allocca
O
O
Caporale
M
M
Triassi
M T
MT
Pellecchia
P
P
Barone
C
C
Vitale
D000368:Aged; D001663:Bilirubin / Q000097:blood*; D015415:Biomarkers / Q000097:blood; D016022:Case-Control Studies; D003430:Cross-Sectional Studies; D018450:Disease Progression; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000097:blood*
D015415:Biomarkers; D001663:Bilirubin
HO; Parkinson; bilirubin; biomarker; diagnosis; heme; motor; progression