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[Preprint]. 2023 Jun 27:rs.3.rs-3073597.
doi: 10.21203/rs.3.rs-3073597/v1.

Mass Spectrometry in Cerebrospinal Fluid Uncovers Association of Glycolysis Biomarkers with Alzheimer's Disease in a Large Clinical Sample

Matthijs B de Geus  1 , Shannon N Leslie  2 , TuKiet Lam  2 , Weiwei Wang  2 , Pia Kivisakk  1 , Angus C Nairn  2 , Steven E Arnold  1 , Becky C Carlyle  3
Affiliations

Mass Spectrometry in Cerebrospinal Fluid Uncovers Association of Glycolysis Biomarkers with Alzheimer's Disease in a Large Clinical Sample

Matthijs B de Geus et al. Res Sq. .

Update in

Abstract

Background: Alzheimer's disease (AD) is a complex heterogenous neurodegenerative disorder, characterized by multiple pathophysiologies, including disruptions in brain metabolism. Defining markers for patient stratification across these pathophysiologies is an important step towards personalized treatment of AD. Efficient brain glucose metabolism is essential to sustain neuronal activity, but hypometabolism is consistently observed in AD. The molecular changes underlying these observations remain unclear. Recent studies have indicated dysregulation of several glycolysis markers in AD cerebrospinal fluid and tissue.

Methods: In this study, unbiased mass spectrometry was used to perform a deep proteomic survey of cerebrospinal fluid (CSF) from a large-scale clinically complex cohort to uncover changes related to impaired glucose metabolism.

Results: Two glycolytic enzymes, Pyruvate kinase (PKM) and Aldolase A (ALDOA) were found to be specifically upregulated in AD CSF compared to other non-AD groups. Presence of full-length protein of these enzymes in CSF was confirmed through immunoblotting. Levels of tryptic peptides of these enzymes correlated significantly with CSF glucose and CSF lactate in matching CSF samples.

Conclusions: The results presented here indicate a general dysregulation of glucose metabolism in the brain in AD. We highlight two markers ALDOA and PKM that may act as potential functionally-relevant biomarkers of glucose metabolism dysregulation in AD.

Keywords: Alzheimer’s disease; Biomarkers; Cerebrospinal fluid; Glucose metabolism; Mass spectrometry.

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Conflict of interest statement

Conflicts of interest S. Arnold has received honoraria and/or travel expenses for lectures from Abbvie, Eisai, and Biogen and has served on scientific advisory boards of Corte, has received consulting fees from Athira, Cassava, Cognito Therapeutics, EIP Pharma and Orthogonal Neuroscience, and has received research grant support from NIH, Alzheimer’s Association, Alzheimer’s Drug Discovery Foundation, Abbvie, Amylyx, EIP Pharma, Merck, Janssen/Johnson & Johnson, Novartis, and vTv. S.N. Leslie is a current employee of Janssen Pharmaceuticals. B. Carlyle has received grant funding from Ono Pharmaceutical. Other authors report no conflicts of interest.

Figures

Figure 1
Figure 1
Experimental workflow and MS processing. A) Overview of cohort and sample processing. B) Distribution of duplicate CV before (red) and after (blue) filtering of robustly measured peptides; dotted lines indicate median. C) Principal component analyses before and after ComBat batch correction of the data. Dots represent individual samples and are colored by their corresponding batch.
Figure 2
Figure 2
Overview of differentially abundant peptides in CSF in AD. A) Overview of differentially expressed peptides between DEM-AD and any non-AD group. B) MS-intensity levels of 4 peptides differentially expressed in an AD specific pattern (ALDOA: Aldolase-A, BASP1: Brain acid soluble protein 1, PKM: Pyruvate kinase muscle). Red lines indicate mean. C) STRING-DB cluster highlighting the enrichment of proteins involved in energy metabolism in AD CSF. Blue indicates proteins from the GO-term “canonical glycolysis”.
Figure 3
Figure 3
Immunoblotting of ALDOA and PKM indicate the presence of full-length proteins in CSF. A) Normalized band intensities of ALDOA and PKM follow similar intensity pattern across groups as their tryptic peptides (*: p < 0.05). B) MS-intensity of tryptic peptides of both ALDOA and PKM are correlated with the normalized band intensity indicating presence of full-length proteins in CSF.
Figure 4
Figure 4
Measures of metabolites in CSF. A) Levels of glucose and lactate in CSF across groups. (*: p < 0.05) B) MS intensities for ALDOA and PKM peptides correlate negatively with the CSF glucose and lactate levels. C) Peripheral glucose metabolism marker HbA1c did not show a strong correlation with MS intensities for ALDOA and PKM peptides.
Figure 5
Figure 5
Levels of glycolytic enzymes are generally elevated in AD in CSF and brain tissue. Colors represent scaled peptide or protein abundance across all proteins for each individual dataset. †: DEx compared to MCI-AD, *: DEx compared to DEM-AD, #: DEx compared to AD in tissue.
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