The pathophysiological mechanism of depression is complex and its etiology remains unclear. Metabolomics can be used to monitor multiple metabolic pathways simultaneously, thereby investigating the mechanisms of depression onset and its regulation. Therefore, we studied the metabolic profile of urine samples from a rat model of depression for identifying potential metabolic biomarkers associated with depression. The depression model of rats was induced by 14-d simulated microgravity (SMG) treatment. Principal component analysis and orthogonal partial least squares discriminate analysis were performed to classify and identify the differences of endogenous metabolites in urine between the normal and depressed rats. Multivariate statistical analysis revealed distinct separation between the urinary metabolic profiles of SMG-treated and control rats. Citric acid, oxalosuccinic acid, creatine, proline, cyclic AMP, L-dihydroxyphenylalanine (DOPA), phenylacetylglycine, 5-hydroxyindole acetaldehyde, succinylcholine, deoxyuridine, 3-hydroxyhippuric acid, glutamine, and 5-hydroxytryptophan levels were significantly reduced, whereas indole-3-acetaldehyde, xanthurenic acid, taurine, kynurenic acid, hippuric acid, 5-hydroxyindoleacetic acid, 2-phenylethanol glucuronide, 2-isopropyl-3-oxosuccinate, and adrenaline levels were elevated significantly in model group. These biochemical changes were related to tryptophan, arginine, proline, and phenylalanine metabolism, and perturbations in energy metabolism. These details of depression will be helpful to the clinical diagnosis of depression caused by space and gravity.
Keywords: Metabolomics; Simulated microgravity; Ultra-high performance liquid chromatography coupled to triple-quadrupole mass spectrometry; Ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry.
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