Chronic stress is closely linked to clinical depression, which could be assessed by a chronic unpredictable mild stress (CUMS) animal model. We present here a GC/MS-based metabolic profiling approach to investigate neurochemical changes in the cerebral cortex, hippocampus, thalamus, and remaining brain tissues. Multi-criteria assessment for multivariate statistics could identify differential metabolites between the CUMS-model rats versus the healthy controls. This study demonstrates that the significantly perturbed metabolites mainly involving amino acids play an indispensable role in regulating neural activity in the brain. Therefore, results obtained from such metabolic profiling strategy potentially provide a unique perspective on molecular mechanisms of chronic stress.

Abstract:In this paper, we present a tissue metabonomic method with an optimized extraction procedure followed by instrumental analysis with gas chromatography/time-of-flight mass spectrometry (GC/TOFMS) and spectral data analysis with multivariate statistics. Metabolite extractions were carried out using three solvents: chloroform, methanol, and water, with design of experiment (DOE) theory and multivariate statistical analysis. A two-step metabolite extraction procedure was optimized using a mixed solvent of chloroform-methanol-water (1:2:1, v/v/v) and then followed by methanol alone. This approach was subsequently validated using standard compounds and liver tissues. Calibration curves were obtained in the range of 0.50-125.0 μg/mL for standards and 0.02-0.25 g/mL acceptable for liver tissue samples. For most of the metabolites investigated, relative standard deviations (RSD) were below 10% within a day (reproducibility) and below 15% within a week (stability). Rat liver tissues of carbon tetrachloride-induced acute liver injury models (n = 10) and healthy control rats (n = 10) were analyzed which demonstrated the applicability of the developed procedure for the tissue metabonomic study.

The effect of hyperlipidemia and inflammation on endothelial functions was studied. The enrolled included control (basic chow), hyperlipidemia and fenofibrate-treated groups (high fat diet). The hyperlipidemia model was set up by four-week atherogenic diet, followed by a 16-week treatment in the fenofibrate-treated group (fenofibrate 40 mg/kg every day) and without treatment in the hyperlipidemia group, respectively. In the 20th week, serum lipid level and NO levels were measured, and the expression of vascular cell adhesion molecule-1 (VCAM-1) and cell adhesiveness in aortic endothelia observed by computer-aided system. Compared with the control group, hyperlipidemia rats showed lower levels of NO and increases in leukocyte accumulation on the endothelial surface, also stronger and more extensive endothelial expression of VCAM-1. In fenofibrate-treated group, the expression of VCAM-1 and leukocyte accumulation on the endothelial surface was decreased, while serum levels of NO were increased as compared with hyperlipidemia group. Hyperlipidemia can inhibit the NO activity and promote the damage of VACA-1 to aortic endothelia. Fenofibrate can effectively prevent the pathogenesis of atherosclerosis by restoring NO levels and down-regulating the VCAM-1 expression.