Depression is the most common disabling psychiatric disease, with a high prevalence and mortality. Chronic unpredictable mild stress (CUMS) is a well-accepted method used to mimic clinical depression. Recent evidence has consistently suggested that the cumulative effects of CUMS could lead to allostatic overload in the body, thereby inducing systemic disorders; however, there are no previous systematic metabonomics studies on the main stress-targeted tissues associated with depression. A non-targeted gas chromatography-mass spectrometry (GC-MS) approach was used to identify metabolic biomarkers in the main stress-targeted tissues (serum, heart, liver, brain, and kidney) in a CUMS model of depression. Male Sprague-Dawley rats were randomly allocated to the CUMS group (n = 8) or a control group (n = 8). Multivariate analysis was performed to identify the metabolites that were differentially expressed between the two groups. There were 10, 10, 9, 4, and 7 differentially expressed metabolites in the serum, heart, liver, brain and kidney tissues, respectively, between the control and CUMS groups. These were linked to nine different pathways related to the metabolism of amino acids, lipids, and energy. In summary, we provided a comprehensive understanding of metabolic alterations in the main stress-targeted tissues, helping to understand the potential mechanisms underlying depression. An increasing body of evidence has revealed that the cumulative effect of stress can trigger allostatic overload 1-3. "Allostatic load" refers to the effects of prolonged continuous or intermittent activation of effectors involved in allostasis 4-6. Allostatic load has been associated with many diseases, such as cardiovascular disease, diabetes, stroke, chronic kidney disease, abdominal obesity, and depression 7,8. These all involve the whole body. Thus, the stress-induced allostatic overload involved in depression is focused on in our study. Depression is a seriously debilitating psychiatric disease, characterized by high mortality and morbidity. The chronic unpredictable mild stress (CUMS) model, a well-accepted animal model of depression, is used to explore the mechanisms underlying depression 9-11. One proposed mechanism involves allostatic load, a multidimensional biologic construct that involves biomarkers across the physiologic domains of neuroendocrine, autonomic, immune, and metabolic function 7. Allostatic overload resulting from CUMS in animal models causes atrophy of neurons in the hippocampus and prefrontal cortex 4,5 , myocardial ischemia 9 , abnormal hepatic metabolism 12 , and poor kidney outcomes 8,13. Thus, the impact of stress involves the whole body and depression is linked to multiple diseases such as cardiovascular disease 9. However, there are no previous systematic metabonomics studies focusing on the main stress-targeted tissues. Thus, the aim of the present study was to provide a panoramic and systematic view of metabolic alterations in stress-targeted tissues (serum, heart, liver, brain, and kidney) in the conte...