MALDI-MS CEREBROSPINAL FLUID (CSF) N-GLYCAN PROFILES IN NEURODEGENERATIVE DISEASES

Glycosylation is a key post-translational protein modification in different biological functions such as cellular adhesion, recognition and signalling, and changes in protein glycosylation have been recognized in different neurodegeneration disorders [1]. Alzheimer's Disease (AD) and Parkinson's Disease (PD) are the most common neurodegenerative diseases. Both pathologies are multifactorial diseases presenting clinically heterogeneous symptoms and prognosis and ultimately resulting in neurons loss of functions and death. AD and PD are diagnosed by clinical and neuropsychological criteria, only proved by post-mortem autopsy. Therefore, there is a great need of diagnostic tools able of detecting the diseases in their early stages when preventative therapies could ameliorate patients' conditions before irreversible neuronal damages. We performed Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry (MALDI-MS) CSF N-glycosylation analysis of released and permethylated N-glycans from a cohort including 21 AD, 11 mild cognitive impairment (MCI), 19 PD patients and 19 control subjects (age- and gender-matched). PD-CSF spectra denoted a significant increase of high-mannose 5 (M5, m/z 1579.8), agalactosylated biantennary (G0, m/z 1661.8), agalactosylated bisected biantennary (G0B, m/z 1906.9) bisected, agalactosylated core fucosylated N-glycans (G0BF, m/z 2081.0). Although no unique profile emerged for AD and MCI, principal component analysis (PCA) allows to separate AD and MCI in two categories, according to bisecting-N-glycans relative intensities. AD1 and MCI1 showed significant increase of bisecting structures and an overall decrease of sialylated species compared to healthy controls, while AD2 and MCI2 showed a slightly reduction of those species. Interestingly, the observed divergences in MCI1 and MCI2 glycosylation profiles reflected the different clinical follow-up of the respective class of patients: 5 MCI1 patients out 5 converted to AD within 36 months from diagnosis, while all the MCI2 subjects (6 out 6) remained stable over the time, suggesting that increasing amount of N-glycans with bisected GlcNAc is a biochemical hallmark of AD in the pre-dementia phase [2]. MALDI-MS CSF N-glycome profiling enabled detection of peculiar changes in subject affected by neurodegenerative diseases, helpful in monitoring diseases development and progression, thus representing a source of potential biomarkers and therapeutic targets.