Multicenter Study of Blood Biomarkers of Mitochondrial and Peroxisomal Metabolism to Differentiate Idiopathic Parkinson's Disease From Related Conditions

With the aging of the population due to an increase in longevity, the number of people with Parkinson's disease is increasing (166,712 in France, as of December 31, 2015) and the number of patients with motor or cognitive-behavioral disorders is already a major public health challenge (1). In neurodegenerative diseases, the current strategy is to identify the disease early and, if possible, to consider therapeutic measures to slow down the progression of the disease.

Classically, when faced with the early stages of Parkinsonism, the investigators differentiate idiopathic Parkinson's disease (IPD) from atypical Parkinsonian syndromes (AP), which include multiple system atrophy (MSA), corticobasal degeneration (CBD), and progressive supranuclear palsy (PSP), for which the prognoses are more severe and the therapies less effective. In the early stage of the disease, when the symptoms are not do no yet differentiate the diseases, the differential diagnosis between IPD and PSP is a real challenge for clinicians (2). Cerebral MRI can help in the diagnosis but is most often only an indicator, as it may be normal in the early stages of the disease (2). The recent emergence of targeted therapies, specific to tauopathies or synucleinopathies, makes it essential to establish a diagnosis as early as possible in order to curb the evolution of the disease (3).

The investigators propose here a first study on the analysis of biomarkers of neurodegeneration from lipid metabolism allowing to discriminate IPD and AP from peripheral blood. Two recent studies have provided evidence of the discriminatory character of neurofilament blood testing in the early phases of parkinsonism (4,5). On the other hand, to our knowledge, none of them has studied markers from mitochondrial and peroxisomal metabolism, which could play a key role in the pathophysiology of these diseases (6,7,8,9,10).

Our strategy will therefore be to study idiopathic or atypical Parkinsonism subjects with a clearly established diagnosis in a cross-sectional manner, and to identify one or more blood markers of neurodegeneration predictive of IPD or AP, hypothesizing that these markers will be at significantly different levels between the two groups (descriptive analysis). The markers studied will include markers of neurodegeneration, markers of mitochondrial function, peroxisomal function and oxidative stress. The investigators will then study the correlations between these biomarkers and motor scores of disease severity.