Characterization of Potential Protein Biomarkers for Major Depressive Disorder Using Matrix-Assisted Laser Desorption Ionization/Time-of-Flight Mass Spectrometry

Chieh-Hsin Lin,Jentaie Shiea,Chung-Chieh Hung,Hsien-Yuan Lane,Hung Su

doi:10.3390/molecules26154457

Abstract

Matrix-assisted laser desorption ionization/time-of-flight (MALDI-TOF) mass spectrometry is a sensitive analytical tool for characterizing various biomolecules in biofluids. In this study, MALDI-TOF was used to characterize potential plasma biomarkers for distinguishing patients with major depressive disorder (MDD) from patients with schizophrenia and healthy controls. To avoid interference from albumin—the predominant protein in plasma—the plasma samples were pretreated using acid hydrolysis. The results obtained by MALDI-TOF were also validated by electrospray ionization-quadrupole time-of-flight (ESI-QTOF) mass spectrometry. The analytical results were further treated with principal component analysis (PCA), hierarchical clustering analysis (HCA), and receiver operating characteristic (ROC) curve analysis. The statistical analyses showed that MDD patients could be distinguished from schizophrenia patients and healthy controls by the lack of apolipoprotein C1 (Apo C1), which, in fact, was detected in healthy controls and schizophrenia patients. This protein is suggested to be a potential plasma biomarker for distinguishing MDD patients from healthy controls and schizophrenia patients. Since sample preparation for MALDI-TOF is very simple, high-throughput plasma apolipoprotein analysis for clinical purposes is feasible.

Highlights

Major depressive disorder (MDD) is a common mental disease that can promote disturbed behavior leading to disability and suicide
The ion cluster for patients with schizophrenia was not clearly separated from that of healthy controls and major depressive disorder (MDD) patients. These results suggest that some schizophrenia and MDD patients may share common biomarkers
The literature search results indicated that some apolipoproteins with similar mass range as the potential biomarkers observed in this study have been reported as potential biomarkers for psychiatric diseases

Summary

Introduction

Major depressive disorder (MDD) is a common mental disease that can promote disturbed behavior leading to disability and suicide. Proteins in plasma samples were precipitated with an organic solvent, after which strong acid hydrolysis followed by MALDI-TOF analysis was used to remove abundant proteins and detect potential biomarkers to distinguish MDD patients from healthy controls and patients with other mental diseases. The literature search results indicated that some apolipoproteins with similar mass range as the potential biomarkers observed in this study have been reported as potential biomarkers for psychiatric diseases The levels of such apolipoproteins (i.e., Apo A1, Apo A2, Apo A4, Apo C1, and Apo D) were significantly decreased in the serum of schizophrenia patients in a detected by acid hydrolysis followed by MALDI-TOF analysis. Once plasma samples were obtained from the subjects in each group, these samples were immediately delivered to the laboratory and divided into several parts (100 μL/tube) to avoid the influence of freeze-and-thaw on biological samples, and stored at −80 ◦C until analysis

Chemicals and Materials

Acid Hydrolysis

Mass Spectrometric Analyses

Findings

Multivariate Statistical Analyses