Major depressive disorder (MDD) is a common neuropsychiatry disorder with high prevalence and recurrence rate, but the misdiagnosis rate is inevitable due to the shortage of objective laboratory-based diagnostic criteria. This study is focused on the disturbance of lipid metabolism, providing potential biomarkers for diagnosing.

Lipid metabolism-related molecules in plasma of 42 drug-naïve MDD patients and 49 healthy people were measured by liquid chromatography-mass spectrometry. Further to evaluate the diagnostic values of changed metabolites, these molecules were evaluated by the receiver operating characteristic curve. Based on the significant role of phosphatidylcholine (PC) disturbance in depression, oxidization of PCs, oxidation of 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine (OxPAPC), IL-8 and caspase-3 in hippocampus, and serum of chronic lipopolysaccharide (cLPS) depression mice were detected by ELISA.

Compared with healthy control, MDD patients expressed higher 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (16:0-16:0 PC, DPPC), 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine (16:0-20:4 PC, PAPC), 1-palmitoyl-2-stearoyl-sn-glycero-3-phosphocholine (16:0-18:0 PC), glycocholic acid, taurocholic acid, glycoursodeoxycholic acid, and chenodeoxycholic acid glycine conjugate, and lower 1-heptadecanoyl-2-hydroxy-sn-glycero-3-phosphocholine (LPC 20:0). The 16:0-20:4 PC showed the great diagnostic value for MDD with an area under the curve (AUC) of 0.9519, and combination of 16:0 PC, 16:0-18:0 PC, and 16:0-20:4 PC exhibited the highest diagnostic value with AUC of 0.9602. OxPAPC was certified increase in hippocampus and serum of cLPS depression mice, which further supported PCs disorder participated in depression.

This research offers 16:0-20:4 PC as the latent diagnostic indicator for MDD and hints the important role of PCs in depression.