Hepatotoxin-induced hypertyrosinemia and its toxicological significance

Use of alternative protein sources for fishmeal replacement in the diet of largemouth bass (Micropterus salmoides). Part I: effects of poultry by-product meal and soybean meal on growth, feed utilization, and health

Five isonitrogenous and isocaloric diets [containing 54, 30, 15, 10, and 5% fishmeal crude-protein (CP), dry matter (DM) basis] were prepared by replacing fishmeal with poultry by-product meal plus soybean meal to feed juvenile largemouth bass (LMB, with an initial mean body weight of 4.9 g) for 8 weeks. All diets contained 54% CP and 13% lipids. There were four tanks of fish per treatment group (15 fish/tank). The fish were fed twice daily with the same feed intake (g/fish) in all the dietary groups. Results indicated that the inclusion of 15% fishmeal protein in the diet is sufficient for LMB growth. However, some of the fish that were fed diets containing ≤ 15% fishmeal CP had black skin syndrome (characterized by skin darkening and retinal degeneration, as well as intestinal and liver atrophies and structural abnormalities). The concentrations of taurine, methionine, threonine and histidine in serum were reduced (P < 0.05) in fish fed the diets containing 5, 10 and 15% fishmeal CP, compared with the 30 and 54% fishmeal CP diets. Interestingly, the concentrations of tyrosine and tryptophan in serum were higher in fish fed diets with ≤ 15% fishmeal CP than those in the 54% fishmeal CP group. These results indicated that 15% fishmeal CP in the diet containing poultry by-product meal and soybean meal was sufficient for the maximum growth and feed efficiency in LMB but inadequate for their intestinal, skin, eye, and liver health. A reduction in dietary methionine and taurine content and the possible presence of antinutritional factors in the fishmeal replacements diets containing high inclusion levels of soybean meal may contribute to black skin syndrome in LMB. We recommend that the diets of juvenile LMB contain 30% fishmeal CP (DM basis).

GC-MS-based Metabolomic Profiling of Thymoquinone in Streptozotocin-induced Diabetic Nephropathy in Rats

Diabetic nephropathy is a common complication of diabetes mellitus and one of the major etiologies of end-stage renal disease. Specific therapeutic interventions are necessary to treat such complications. The present study was designed to investigate the metabolomic changes induced by thymoquinone for the treatment of diabetic nephropathy, using a rodent model. Rats were divided into three different groups (n = 6 each): control, diabetic, and thymoquinone-treated diabetic groups. Metabolites in serum samples were analyzed via gas chromatography-mass spectrometry. Multiple changes were observed, including those related to the metabolism of amino acids and fatty acids. The correlation analysis suggested that treatment with thymoquinone led to the reversal of diabetic nephropathy that was associated with modulations in the metabolism and proteolysis of amino acids, fatty acids, glycerol phospholipids, and organic acids. In addition, we explored the mechanisms linking the metabolic profiling of diabetic nephropathy, with a particular emphasis on the potential roles of increased reactive oxygen species production and mitochondrial dysfunctions. Our findings demonstrated that metabolomic profiling provided significant insights into the basic mechanisms of diabetic nephropathy and the therapeutic effects of thymoquinone.

Dexamethasone Pretreatment Alleviates Isoniazid/Lipopolysaccharide Hepatotoxicity: Inhibition of Inflammatory and Oxidative Stress

Isoniazid (INH) remains a cornerstone key constitute of the current tuberculosis management strategy, but its hepatotoxic potentiality remains a significant clinical problem. Our previous findings succeed to establish a rat model of INH hepatotoxicity employing the inflammatory stress theory in which non-injurious doses of inflammatory-mediating agent bacterial lipopolysaccharides (LPS) augmented the toxicity of INH that assist to uncover the mechanisms behind INH hepatotoxicity. Following LPS exposure, several inflammatory cells are activated and it is likely that the consequences of this activation rather than direct hepatocellular effects of LPS underlie the ability of LPS to augment toxic responses. In this study, we investigated the potential protective role of the anti-inflammatory agent dexamethasone (DEX), a potent synthetic glucocorticoid, in INH/LPS hepatotoxic rat model. DEX pre-treatment successfully eliminates the components of the inflammatory stress as shown through analysis of blood biochemistry and liver histopathology. DEX potentiated hepatic anti-oxidant mechanisms while serum and hepatic lipid profiles were reduced. However, DEX administration was not able to revoke the principal effects of cytochrome P450 2E1 (CYP2E1) in INH/LPS-induced liver damage. In conclusion, this study illustrated the DEX-preventive capabilities on INH/LPS-induced hepatotoxicity model through DEX-induced potent anti-inflammatory activity whereas the partial toxicity seen in the model could be attributed to the expression of hepatic CYP2E1. These findings potentiate the clinical applications of DEX co-administration with INH therapy in order to reduce the potential incidences of hepatotoxicity.

Role of Inflammatory and Oxidative Stress, Cytochrome P450 2E1, and Bile Acid Disturbance in Rat Liver Injury Induced by Isoniazid and Lipopolysaccharide Cotreatment

Isoniazid (INH) remains the core drug in tuberculosis management, but serious hepatotoxicity and potentially fatal liver injury continue to accompany INH consumption. Among numerous theories that have been established to explain INH-induced liver injury, an inflammatory stress theory has recently been widely used to explain the idiosyncrasy. Inflammatory stress usually sensitizes tissues to a drug's toxic consequences. Therefore, the present study was conducted to verify whether bacterial lipopolysaccharide (LPS)-induced inflammation may have a role in enhancing INH hepatotoxicity. While single INH or LPS administration showed no major toxicity signs, INH-LPS cotreatment intensified liver toxicity. Both blood biomarkers and histological evaluations clearly showed positive signs of severe liver damage accompanied by massive necrosis, inflammatory infiltration, and hepatic steatosis. Furthermore, elevated serum levels of bile acid associated with the repression of bile acid synthesis and transport regulatory parameters were observed. Moreover, the principal impact of cytochrome P450 2E1 (CYP2E1) on INH toxicity could be anticipated, as its protein expression showed enormous increases in INH-LPS-cotreated animals. Furthermore, the crucial role of CYP2E1 in the production of reactive oxygen species (ROS) was clearly obvious in the repression of hepatic antioxidant parameters. In summary, these results confirmed that this LPS-induced inflammation model might prove valuable in revealing the hepatotoxic mechanisms of INH and the crucial role played by CYP2E1 in the initiation and propagation of INH-induced liver damage, information which could be very useful to clinicians in understanding the pathogenesis of drug-induced liver injury.

Application of GC/MS-based metabonomic profiling in studying the therapeutic effects of Huangbai-Zhimu herb-pair (HZ) extract on streptozotocin-induced type 2 diabetes in mice

A protocol for metabolic profiling of mice urine was developed based on gas chromatograph-mass spectrometer (GC-MS) to explore metabolic state directly. The intra-day, inter-day, repeatability, and stability RSD for most endogenous compounds were less than 3%. Type 2 diabetic mellitus (T2DM) mice model was induced by high calorie diet combined with streptozocin. Urine from the control, T2DM and Huangbai-Zhimu herb-pair (HZ) treatment mice were enrolled in the subsequent study to show the usefulness of the method. OPLS-DA scores plots demonstrate that the cluster of T2DM mice is separated from that of control mice, while HZ-T2DM mice are located close to control mice, indicating that metabolic profiles of these HZ-T2DM mice are placed toward those of control group. The results illustrate that HZ treatment could lower the level of d-glucose, hexadecanoic acid, octadecanoic acid, propanoic acid, 3-hydroxybutyric acid, and 2,3-dihydroxybutanoic acid in urine of DM mice, meanwhile the results show that HZ treatment could ameliorate T2DM symptoms by intervening the fatty acid metabolism, starch and sucrose metabolism, and glyoxylate and dicarboxylate metabolism. This preliminary application indicated that the method is suitable and reliable for urine metabolic profiling. This study might explain the metabolic effects of T2DM and the mechanisms of action of HZ against T2DM.

Toxic effects of chronic low-dose exposure of thioacetamide on rats based on NMR metabolic profiling

Thioacetamide (TAA) is a well-known toxicant and its long term exposure could induce liver fibrosis and cirrhosis. A liver fibrosis rat model was established by consecutive injection of TAA solution for 7 weeks. Serum and urine samples were collected weekly for NMR based metabolomic study. Clinical biochemistry of serum samples revealed liver impairment and fibrosis. Histopathological inspections disclosed severe liver fibrosis and cirrhosis formation, and pathological changes in kidney by long-term TAA administration. Orthogonal partial least squares-discriminant analysis (OPLS-DA) was applied on serum and urine samples to excavate differential metabolites associated with TAA induced impairment and explore the time-dependent metabolic event associated with this xenobiotic perturbation. Integration of metabolomics results with serum biochemical revealed several potential biomarkers for liver fibrosis (2-hydroxybutyrate, 3-hydroxybutyrate and adipate in urine, and phenylalanine, N,N-dimethyl glycine, O-acetyl glycoprotein, N-acetyl glycoprotein and choline in serum). Pathway analysis revealed disturbed pathways concerning tricarboxylic acid (TCA) cycle, pyruvate metabolism, starch and sucrose metabolism, glycolysis or gluconeogenesis, degradation of ketone bodies, butanoate metabolism, and biosynthesis of BCAAs (valine, leucine and isoleucine) and AAAs (phenylalanine, tyrosine and tryptophan). This integrative study should help to develop a systematic understanding of liver fibrosis-related diseases and their metabolic events.

Blood content of tyrosine is an index of glucocorticoid action on metabolism

Glucocorticoid hormones directly or indirectly control virtually all metabolic and physiological processes. Glucocorticoids are also shown to act on a multitude of genes, enzyme systems, and proinflammatory factors, but for these hormones there is no representative index of action on metabolism similar to glucose content in blood for insulin. The absence of such an index prevents the assessment of tissue provision with these hormones under various conditions and seems to be an essential cause of complications associated with the clinical use of glucocorticoid preparations. Considering specific features of tyrosine metabolism and data obtained experimentally and on a clinical model (adrenalectomy in rats and substitution therapy in endocrine disease), blood content of this amino acid seems promising as such an index. Based on comparing results of glucocorticoid treatment in patients with systemic lupus erythematosus with changes in their blood tyrosine contents, the pharmacological effect of glucocorticoid preparations is suggested to be mainly due to compensating a relative shortage of these hormones.

Site and strain-specific variation in gut microbiota profiles and metabolism in experimental mice

Background

The gastrointestinal tract microbiota (GTM) of mammals is a complex microbial consortium, the composition and activities of which influences mucosal development, immunity, nutrition and drug metabolism. It remains unclear whether the composition of the dominant GTM is conserved within animals of the same strain and whether stable GTMs are selected for by host-specific factors or dictated by environmental variables.

Methodology/Principal Findings

The GTM composition of six highly inbred, genetically distinct strains of mouse (C3H, C57, GFEC, CD1, CBA nu/nu and SCID) was profiled using eubacterial –specific PCR-DGGE and quantitative PCR of feces. Animals exhibited strain-specific fecal eubacterial profiles that were highly stable (c. >95% concordance over 26 months for C57). Analyses of mice that had been relocated before and after maturity indicated marked, reproducible changes in fecal consortia and that occurred only in young animals. Implantation of a female BDF1 mouse with genetically distinct (C57 and Agoutie) embryos produced highly similar GTM profiles (c. 95% concordance) between mother and offspring, regardless of offspring strain, which was also reflected in urinary metabolite profiles. Marked institution-specific GTM profiles were apparent in C3H mice raised in two different research institutions.

Conclusion/Significance

Strain-specific data were suggestive of genetic determination of the composition and activities of intestinal symbiotic consortia. However, relocation studies and uterine implantation demonstrated the dominance of environmental influences on the GTM. This was manifested in large variations between isogenic adult mice reared in different research institutions.

Application of GC/MS-based metabonomic profiling in studying the lipid-regulating effects of Ginkgo biloba extract on diet-induced hyperlipidemia in rats

AIM

To evaluate the lipid-regulating effects of extract from Ginkgo biloba leaves (EGB) using pharmacological methods and metabonomic profiling in a rat model of diet-induced hyperlipidemia.

METHODS

EGB was orally administered at a dose level of 40 mg/kg in both the EGB-prevention and -treatment groups. All rat samples obtained were examined for known and potential biomarkers and enzyme activity using commercial assay kits and GC/MS-based metabonomic profiling coupled with principal component analysis (PCA).

RESULTS

The data obtained from the assay kits indicated that EGB reduced total cholesterol and low density lipoprotein cholesterol levels and increased high density lipoprotein cholesterol levels in rat plasma obtained from both the EGB-prevention and -treatment groups compared with those of the diet-induced hyperlipidemia group. EGB also increased the activities of lipoprotein lipase and hepatic lipase and excretion of fecal bile acid in rats from the EGB-prevention and-treatment groups. Using GC/MS-based metabonomic analysis, more than 40 endogenous metabolites were identified in rat plasma. PCA of rat plasma samples obtained using GC/MS produced a distinctive separation of the four treatment groups and sampling points within each group. Metabolic changes during hyperlipidemia formation and improvement resulting from EGB treatment were definitively monitored with PCA score plots. Furthermore, elevated levels of sorbitol, tyrosine, glutamine and glucose, and decreased levels of citric acid, galactose, palmitic acid, arachidonic acid, acetic acid, cholesterol, butyrate, creatinine, linoleate, ornithine and proline, were observed in the plasma of rats treated with EGB.

CONCLUSION

EGB exerts multi-directional lipid-lowering effects on the rat metabonome, including limitation of the absorption of cholesterol, inactivation of HMGCoA and favorable regulation of profiles of essential polyunsaturated fatty acid (EFA). Further experiments are warranted to explore the mechanisms of action underlying the lipid-regulating effects of EGB against hyperlipidemia.

NMR-based metabolic profiling and metabonomic approaches to problems in molecular toxicology

We have reviewed the main contributions to the development of NMR-based metabonomic and metabolic profiling approaches for toxicological assessment, biomarker discovery, and studies on toxic mechanisms. The metabonomic approach, (defined as the quantitative measurement of the multiparametric metabolic response of living systems to pathophysiological stimuli or genetic modification) was originally developed to assist interpretation in NMR-based toxicological studies. However, in recent years there has been extensive fusion with metabolomic and other metabolic profiling approaches developed in plant biology, and there is much wider coverage of the biomedical and environmental fields. Specifically, metabonomics involves the use of spectroscopic techniques with statistical and mathematical tools to elucidate dominant patterns and trends directly correlated with time-related metabolic fluctuations within spectral data sets usually derived from biofluids or tissue samples. Temporal multivariate metabolic signatures can be used to discover biomarkers of toxic effect, as general toxicity screening aids, or to provide novel mechanistic information. This approach is complementary to proteomics and genomics and is applicable to a wide range of problems, including disease diagnosis, evaluation of xenobiotic toxicity, functional genomics, and nutritional studies. The use of biological fluids as a source of whole organism metabolic information enhances the use of this approach in minimally invasive longitudinal studies.