The investigators have recently discovered a metabolic biomarker which predicts Parkinson's disease (PD) at the early stages in patients and in animal models. The aim of BIOPARK is to investigate how the biomarker evolves in advanced PD stage, when diagnosis confirmation is higher, an in de novo PD patients who come from a different geographical area than those of the publication (since it is known that the metabolome is largely influenced by lifestyle). They will also evaluate if the biomarker is able to distinguish patients with a parkinsonian syndrome often confused with parkinson's disease, i.e. Multiple System Atrophy (MSA).

Parkinson's disease (PD) affects more than 7 million people worldwide and represents a growing health and socio-economic burden. It is an incurable neurodegenerative disease, and the search for biomarkers that allow reliable early diagnosis and provide new therapeutic targets is essential to find cures for PD.

In a recently published preclinical and clinical study, the investigators have identified in 2 rat models of PD and a primate model and in 2 human cohorts from biobanks significant deregulations of 6 serum metabolites: acetoacetate, betaine, beta-hydroxybutyrate, creatine, pyruvate and valine. From these 6 metabolites, they built a composite biomarker, which allowed to classify de novo parkinsonian patients against controls (healthy subjects) with an accuracy (defined as the ratio (correctly classified/total) of 82.6%. This study demonstrated for the first time that a common metabolic dysregulation occurs early in either animal models or in PD patients, thus providing an unbiased diagnostic tool as well as major hypothesis for the understanding of the pathophysiology of the disease and the development of innovative therapeutic approaches.

The goal of BIOPARK is to improve the clinical diagnosis of early PD using the blood biomarker.

To this end, the investigators will study whether the biomarker is able to differentiate between patients with PD >5 years and already treated with dopaminergic drugs (thus with a very high diagnostic confirmation) and patients suffering from other neurodegenerative diseases often confused with it, mainly Multiple Systeme Atrophy (MSA). Furthermore, the investigators hope to confirm the preliminary results on a new cohort of de novo patients.

For that aim, they will use the already optimized method for biomarker discovery, i.e. Nuclear Magnetic Resonance (NMR)-based metabolomics on patient serum.

Inclusion Criteria:

• Patients with de novo Parkinson's disease, without dopaminergic treatment
• Patients with advanced Parkinson's disease (> 5years) with dopaminergic treatment
• Patients with multiple system atrophy

Exclusion Criteria:

• Patients with deep brain stimulation
• Other neurodegenerative diseases
• patients protected by french law (pregnant or lactating women, prisoners, ...)

The study population consists of patients coming for consultation or admission to day clinic of the neurologic department of the university hospital Grenoble.