Objective: To evaluate serum bilirubin concentration in Parkinson’s disease (PD) compared to healthy controls (HC) and to investigate its associations with motor and non-motor features in our population from southern Spain.

Background: Oxidative stress is one of the main pathways studied in PD etiopathology and heme oxygenase (HO) is an important enzyme which regulates oxidative balance. HO converts heme molecules in carbon monoxide, iron and biliverdin/bilirubin and it is described HO upregulation in dopaminergic cells exposed to oxidative stress. Increased levels of bilirubin have been found in PD patients compared to controls and are interpreted as a consequence of oxidative enzymes overexpression in central nervous system.

Methods: We included 401 PD patients (48% males, 63±12 years) and 309 HC (48% males, 58±16 years), and total bilirubin plasma levels was measured. We excluded subjects on treatment with statins or chemotherapy, liver disease and hemolytic anemia. Demographic data were collected in both groups as well as clinical manifestations and complications of dopaminergic therapy in PD patients. We evaluated severity of PD with Hoehn & Yahr scale. To compare bilirubin levels between groups we analyzed data with binary logistic regression and multivariante analysis adjusted by age and gender. In PD group, bilirubin levels were also correlated with clinical characteristics.

Results: Bilirubin levels were significantly higher in PD patients than HC subjects (PD: 0.58 ± 0.27 mg/dl, HC: 0.43 ± 0.2 mg/dl; p<0.005). In PD patients we demonstrated a negative correlation between bilirubin levels and Hoehn & Yahr stage (p<0.05) with increased levels in early stages of PD. We identified higher bilirubin levels in PD patients with dysphagia, falls and visual hallucinations (p<0.05) but no other significant differences were found regarding the clinical manifestations.

Conclusions: Increased bilirubin levels might be related to PD etiopathology as a serum biomarker of oxidative stress dysregulation. In early stages of disease, with lower Hoehn & Yahr stage, these higher levels might translate overexpression of oxidative enzymes.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/increased-bilirubin-levels-in-parkinsons-disease-from-southern-spain/