Rodents respond to chronic high fat diet in at least two ways: some of them may readily gain body weight and become obese (termed obesity-prone, OP), and others may not (termed obesity-resistant, OR). Transcriptomic and metabonomic profiling of OP and OR rats has been conducted, showing two sets of significantly different phenotypic profiles in response to 16 weeks of high fat diet. We observed significant differences in transcriptional expression of nearly 80 genes, some of which are known to be involved in lipid metabolism, transport, and ketone body production. The different metabolic profiles in liver tissue extracts, serum, and urine between the two phenotypes can be ascribed to the corresponding pathways identified with multivariate statistical analysis, including fatty acid metabolism, Krebs cycle, and amino acid metabolism. The integration of results from transcriptomic and metabonomic studies revealed that the altered metabolic pathways in OP rats may involve the increased activity of sympathetic nervous system and Krebs cycle, an increased production of ketone bodies, and an adaptive regulatory process to store excessive lipids in liver through reverse cholesterol transport process. These biochemical variations at transcriptional and metabolic levels as a result of dietary intervention highlight the significance of combined "omics" strategy in the mechanistic study of obesity and metabolic disorders.

The pathological development and the drug intervention of type 2 diabetes mellitus (T2DM) involve altered expression of downstream low molecular weight metabolites including lipids and amino acids, and carbohydrates such as glucose. Currently, a small number of markers used for clinical assessment of T2DM treatment may be insufficient to reflect global variations in pathophysiology. In this study, a metabonomic study was performed to determine metabolic variations associated with T2DM and the drug treatments on 74 patients who were newly diagnosed with T2DM and received a 48 week treatment of a single drug, repaglinide, metformin or rosiglitazone. Fasting overnight and 2 h postprandial blood serum of patients were collected at 24 and 48 weeks to monitor the biochemical indices (FPG, 2hPG, HbA1c, etc.). Gas chromatography/mass spectrometer coupled with multivariate statistical analysis was used to identify the alteration of global serum metabolites associated with T2DM as compared to healthy controls and responses to drug treatment. Significantly altered serum metabolites in diabetic subjects include increased valine, maltose, glutamate, urate, butanoate and long-chain fatty acid (C16:0, C18:1, C18:0, octadecanoate and arachidonate), and decreased glucuronolactone, lysine and lactate. All of the three treatments were able to down-regulate the high level of glutamate to a lower level in serum of T2DM patients, but rosiglitazone treatment was able to reverse more abnormal levels of metabolites, such as valine, lysine, glucuronolactone, C16:0, C18:1, urate, and octadecanoate, suggesting that it is more efficient to alter the metabolism of T2DM patients than the other two drugs.

The effects of acute and chronic stress on the production of systemic metabolites were investigated in male Sprague-Dawley (SD) rats. Metabolites excreted in urine were analyzed using GC/MS in conjunction with multivariate and univariate statistical techniques. SD rats were subjected to two kinds of acute stress and chronic unpredictable mild stress, respectively. Metabolic analysis demonstrated that urinary expression of a number of metabolites including glutamate, glutamine, homovanillate, proline, succinate, citrate, and tyrosine altered in the acute stress model in the same way as in the chronic model, while pimelate and hippurate changed in the opposite trend. The results suggested that the stress induced metabolic perturbations were reversible and nonspecific. Metabolic response to chronic combined stress revealed biochemical clues to depression-like symptoms validated by behavior and physiologic results. This study provides a noninvasive and dynamic analytical strategy for the characterization of endogenous metabolic perturbations induced by external stress.

Acute stress may trigger systemic biochemical and physiological changes in living organisms, leading to a rapid loss of homeostasis, which can be gradually reinstated by self-regulatory mechanisms and/ or drug intervention strategy. However, such a sophisticated metabolic regulatory process has so far been poorly understood, especially from a holistic view. Urinary metabolite profiling of SpragueDawley rats exposed to cold temperature (-10°C) for 2 h using GC/MS in conjunction with modern multivariate statistical techniques revealed drastic biochemical changes as evidenced by fluctuations of urinary metabolites and demonstrated the protective effect of total ginsenosides (TGs) in ginseng extracts on stressed rats. The metabonomics approach enables us to visualize significant alterations in metabolite expression patterns as a result of stress-induced metabolic responses and post-stress compensation, and drug intervention. Several major metabolic pathways including catecholamines, glucocorticoids, the tricarboxylic acid (TCA) cycle, tryptophan (nicotinate), and gut microbiota metabolites were identified to be involved in metabolic regulation and compensation required to restore homeostasis.