Both experimental animals and humans exhibit complex cellular responses upon exposure to xenobiotics and may undergo similar types of metabolic changes leading to adverse outcomes. Exposure to xenobiotics results in perturbation of many cellular events (e.g. oxidative stress, lipid peroxidation, inflammation, genotoxicity, cytotoxicity, etc.), and during this process biochemicals (endogenous metabolites) of a given metabolic pathway are increased, decreased or unaffected. Metabolomics is an emerging medium to high-throughput technology that can automatically identify, quantify and characterize hundreds to thousands of low molecular weight biochemicals simultaneously, using targeted or global analytical approaches, yielding a metabolic fingerprint and understanding of biochemical pathway perturbations. Herein, we illustrate how metabolomics can be utilized to explore the mechanisms of action of xenobiotics which affect different 'key events' contributing to different mode(s) of action. The extensively studied hepatotoxicant carbon tetrachloride (CCl(4)) is specifically described.
"Metabolite changes also indicated altered TCA cycle and nucleotide metabolism. Several biomarkers of CCl 4 -induced hepatotoxicity have been identified, which are related to specific modes of action (Vulimiri et al. 2011). Specifically, lipids, amino acids, and metabolites related to energy metabolism have been reported to be altered coincidently with liver injury after exposure to CCl 4 . "
[Show abstract][Hide abstract] ABSTRACT: Understanding mechanisms of liver injury can enable better preclinical testing and clinical management of patients. Carbon tetrachloride (CCl4), used extensively as a model hepatotoxicant, induces lipid perturbation and increases in plasma bile acids (BAs). An integrated transcriptomics and metabolomics approach was employed to investigate CCl4-induced alterations in lipid and BA metabolism. Sprague-Dawley rats were treated orally with corn oil, 50 (low dose, LD) or 2,000 mg CCl4/kg/d (high dose, HD). Animals were sacrificed at 6, 24 or 72 h. Terminal blood was collected for clinical chemistry and metabolomics analyses. Livers were harvested for histopathology, metabolomics and transcriptomics analyses. Both alanine aminotransferase (ALT) and aspartate aminotransferase (AST) increased in the treated groups with the greatest increases observed in the HD group at 24 and 72 h. Blood cholesterol and triglycerides (TGs) were significantly decreased in the HD group at both 24 and 72 h, and hepatocyte vacuolization was observed at these timepoints. Consistent with the clinical chemistry and histopathological data, metabolomics results showed that levels of total fatty acids increased in the liver but decreased in the blood in the HD group at the 24 and 72 h timepoints. This suggested that lipids accumulate in the liver. Primary BAs increased in both liver and blood, while secondary and conjugated BAs decreased in the liver and increased in the blood, which indicated that the BA conjugation pathway and that BA uptake by the liver were inhibited by CCl4. Results from this study provide a better understanding of the mechanisms of CCl4-induced hepatotoxicity.
"Animal models of acute and chronic liver injury induced by different toxicants have been studied by NMR-based metabonomics like hydrazine, acetaminophen, thioacetamide, etc. (Bollard et al., 2005a; Coen et al., 2003; Constantinou et al., 2007a; Dyrby et al., 2005; Waters et al., 2005). In this aspect CCl 4 induced acute liver injury has been recently approached by different -omics methods (Vulimiri et al., 2011) such as genomics (Chung et al., 2005), proteomics (Wong et al., 2010). The metabonomic approach has employed both NMR (urine and serum Robertson, 2005; Kim et al., 2008; Sanins et al., 1990; Wu et al., 2005) and MS (urine, and plasma Huang et al., 2008; Lin et al., 2009), in order to better delineate the metabolic changes of the CCl 4 -induced injury. "
[Show abstract][Hide abstract] ABSTRACT: The administration of carbon tetrachloride (CCl(4)) has been established as a model of toxin-induced acute and chronic liver injury. In the present study, we investigate the progression of the biochemical response to acute CCl(4)-induced liver injury, capturing metabolic variations during both toxic insult and regeneration using NMR-based metabonomic analysis of liver tissue and plasma. A single dose of CCl(4) (1mL/kg BW) was intraperitoneally administered to male Wister rats sacrificed every 12hours up to 72h post treatment, while healthy animals served as controls. Acquired (1)H NMR spectra of liver tissue extracts and plasma samples were explored with multivariate analysis and the resulted models were correlated with conventional biochemical and histopathological indices of toxicity for monitoring the progression of experimental injury. The metabonomic analysis resulted in discrimination between the subjects under toxic insult (up to 36h) and those at the regenerative phase (peaked at 48h). At 72h normalization of liver's pathology similar to the controls group was apparent. Principal Component Analysis (PCA) trajectories highlighted the time points of the greater degree of toxic insult and the regenerative state. A number of metabolites such as glucose, lactate, choline, formate exhibited variations suggesting CCl(4) induced impairment in essential biochemical pathways as energy metabolism, lipid biosynthesis and transmethylation reactions. The latter provides new evidence of B12 and folate pathways deficiency, indicative of new mechanistic implications possibly by direct inhibition of B12 dependent enzymes by the chlorinated radicals of CCl(4) metabolism.
"Recently, metabolomic profiling has emerged as a powerful tool to assess disease states, as well as the physiologic effects of drugs or environmental exposures [9,10]. For instance, metabolomic profiling has been used to associate the metabolite sarcosine with prostate cancer progression , defining metabolic individuality, and revealing causal effects on genotype . "
[Show abstract][Hide abstract] ABSTRACT: Cigarette smoking is well-known to associate with accelerated skin aging as well as cardiovascular disease and lung cancer, in large part due to oxidative stress. Because metabolites are downstream of genetic variation, as well as transcriptional changes and post-translational modifications of proteins, they are the most proximal reporters of disease states or reversal of disease states.
In this study, we explore the potential effects of commonly available oral supplements (containing antioxidants, vitamins and omega-3 fatty acids) on the metabolomes of smokers (n = 11) compared to non-smokers (n = 17). At baseline and after 12 weeks of supplementation, metabolomic analysis was performed on serum by liquid and gas chromatography with mass spectroscopy (LC-MS and GC-MS). Furthermore, clinical parameters of skin aging, including cutometry as assessed by three dermatologist raters blinded to subjects' age and smoking status, were measured.
Long-chain fatty acids, including palmitate and oleate, decreased in smokers by 0.76-fold (P = 0.0045) and 0.72-fold (P = 0.0112), respectively. These changes were not observed in non-smokers. Furthermore, age and smoking status showed increased glow (P = 0.004) and a decrease in fine wrinkling (P = 0.038). Cutometry showed an increase in skin elasticity in smokers (P = 0.049) but not in non-smokers. Complexion analysis software (VISIA) revealed decreases in the number of ultraviolet spots (P = 0.031), and cutometry showed increased elasticity (P = 0.05) in smokers but not non-smokers.
Additional future work may shed light on the specific mechanisms by which long-chain fatty acids can lead to increased glow, improved elasticity measures and decreased fine wrinkling in smokers' skin. Our study provides a novel, medicine-focused application of available metabolomic technology to identify changes in sera of human subjects with oxidative stress, and suggests that oral supplementation (in particular, commonly available antioxidants, vitamins and omega-3 fatty acids) affects these individuals in a way that is unique (compared to non-smokers) on a broad level.
Genome Medicine 02/2012; 4(2):14. DOI:10.1186/gm313 · 5.34 Impact Factor
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