Non-targeted Metabolomics Profiling of Plasma Samples From Patients With Major Depressive Disorder

Abstract

Background: Major depressive disorder (MDD) is a neuropsychiatric disorder caused by multiple factors. Although there are clear guidelines for the diagnosis of MDD, the direct and objective diagnostic methods remain inadequate thus far.

Methods: This study aims to discover peripheral biomarkers in patients with MDD and promote the diagnosis of MDD. Plasma samples of healthy controls (HCs, n = 52) and patients with MDD (n = 38) were collected, and then, metabolism analysis was performed using ultrahigh-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS). Heatmap analysis was performed to identify the different metabolites. Meanwhile, receiver operating characteristic (ROC) curves of these differential metabolites were generated.

Results: Six differential metabolites were found by LC-MS/MS analysis. Three of these were increased, including L-aspartic acid (Asp), diethanolamine, and alanine. Three were decreased, including O-acetyl-L-carnitine (LAC), cystine, and fumarate. In addition, LAC, Asp, fumarate, and alanine showed large areas under the curve (AUCs) by ROC analysis.

Conclusion: The study explored differences in peripheral blood between depressed patients and HCs. These results indicated that differential metabolites with large AUCs may have the potential to be promising biomarkers for the diagnosis of MDD.

Keywords: LC-MS/MS; biomarkers; diagnosis; major depressive disorder; non-targeted metabolomics; plasma; receiver operating characteristic curve.

Figure 1

Metabolomics analysis of plasma samples from HCs and patients with MDD. (A) Discriminant analysis of the orthogonal partial least squares (OPLS-DA) method (R²X = 0.796, R²Y = 0.883, Q² = 0.671). (B) Permutation tests performed with 200 random permutations in OPLS-DA models showing R² (green circles) and Q² (blue squares) values from the permuted analysis (left) as significantly lower than the corresponding original R² and Q² values (right) (R² = 0.433, Q² = −0.812).

Figure 2

Differential metabolites in plasma of HC and MDD. (A) Levels of metabolites were determined by LC–MS/MS, including LAC, Asp, cystine, diethanolamine, alanine, and fumarate, in the HC group (n = 52) and the MDD group (n = 38). (B) Heatmap of the differential metabolites in plasma (HC vs. MDD). Blue, positive correlation; red, negative correlation. Student's t-test and Mann–Whitney U-test were used for the comparison of two groups in which data obeyed normal and abnormal distribution, respectively. ^*p < 0.05, ^**p < 0.01, and ^***p < 0.001.

Figure 3

Heatmap of the correlation matrix among differential metabolites.

Figure 4

Judgment of the diagnostic value of differential metabolites. Receiver operating characteristic (ROC) analysis showing the diagnostic performances of these differential metabolites: the areas under the curve (AUCs) values of LAC, Asp, fumarate, and alanine were 0.871, 0.873, 0.858, and 0.859, respectively (A–D).