Arsenic is a ubiquitous contaminant in drinking water. Whereas arsenic can be directly hepatotoxic, the concentrations/doses required are generally higher than present in the US water supply. However, physiological/biochemical changes that are alone pathologically inert can enhance the hepatotoxic response to a subsequent stimulus. Such a '2-hit' paradigm is best exemplified in chronic fatty liver diseases. Here, the hypothesis that low arsenic exposure sensitizes liver to hepatotoxicity in a mouse model of non-alcoholic fatty liver disease was tested. Accordingly, male C57Bl/6J mice were exposed to low fat diet (LFD; 13% calories as fat) or high fat diet (HFD; 42% calories as fat) and tap water or arsenic (4.9 ppm as sodium arsenite) for ten weeks. Biochemical and histologic indices of liver damage were determined. High fat diet (± arsenic) significantly increased body weight gain in mice compared with low-fat controls. HFD significantly increased liver to body weight ratios; this variable was unaffected by arsenic exposure. HFD caused steatohepatitis, as indicated by histological assessment and by increases in plasma ALT and AST. Although arsenic exposure had no effect on indices of liver damage in LFD-fed animals, it significantly increased the liver damage caused by HFD. This effect of arsenic correlated with enhanced inflammation and fibrin extracellular matrix (ECM) deposition. These data indicate that subhepatotoxic arsenic exposure enhances the toxicity of HFD. These results also suggest that arsenic exposure might be a risk factor for the development of fatty liver disease in human populations.

SUMMARY Chronic activation of brain-derived neurotrophic factor (BDNF) receptor TrkB is a potential method to prevent development of obesity, but the short half-life and nonbioavailable nature of BDNF hampers validation of the hypothesis. We report here that activation of muscular TrkB by the BDNF mimetic, 7,8-dihydroxyflavone (7,8-DHF), is sufficient to protect the development of diet-induced obesity in female mice. Using in vitro and in vivo models, we found that 7,8-DHF treatment enhanced the expression of uncoupling protein 1 (UCP1) and AMP-activated protein kinase (AMPK) activity in skeletal muscle, which resulted in increased systemic energy expenditure, reduced adiposity, and improved insulin sensitivity in female mice fed a high-fat diet. This antiobesity activity of 7,8-DHF is muscular TrkB-dependent as 7,8-DHF cannot mitigate diet-induced obesity in female muscle-specific TrkB knockout mice. Hence, our data reveal that chronic activation of muscular TrkB is useful in alleviating obesity and its complications.

Arsenic is a widely-distributed environmental component that is associated with a variety of cancer and non-cancer adverse health effects. Additional lifestyle factors, such as diet, contribute to the manifestation of disease. Recently, arsenic was found to increase inflammation and liver injury in a dietary model of fatty liver disease. The purpose of the present study was to investigate potential mechanisms of this diet-environment interaction via a high throughput metabolomics approach. GC×GC-TOF MS was used to identify metabolites that were significantly increased or decreased in the livers of mice fed a Western diet (a diet high in fat and cholesterol) and co-exposed to arsenic-contaminated drinking water. The results showed that there are distinct hepatic metabolomic profiles associated with eating a high fat diet, drinking arsenic-contaminated water, and the combination of the two. Among the metabolites that were decreased when arsenic exposure was combined with a high fat diet were short-chain and medium-chain fatty acid metabolites and the anti-inflammatory amino acid, glycine. These results are consistent with the observed increase in inflammation and cell death in the livers of these mice, and they point to potentially novel mechanisms by which these metabolic pathways could be altered by arsenic in the context of diet-induced fatty liver disease.

Motivation: Due to the high complexity of metabolome, the comprehensive 2D gas chromatography time-of-flight mass spectrometry (GCÂGC-TOF MS) is considered as a powerful analytical platform for metabolomics study. However, the applications of GCÂGC-TOF MS in metabolomics are not popular owing to the lack of bioinformatics system for data analysis. Results: We developed a computational platform entitled metabolomics profiling pipeline (MetPP) for analysis of metabolomics data acquired on a GCÂGC-TOF MS system. MetPP can process peak filtering and merging, retention index matching, peak list alignment, normalization, statistical significance tests and pattern recognition, using the peak lists deconvoluted from the instrument data as its input. The performance of MetPP software was tested with two sets of experimental data acquired in a spike-in experiment and a biomarker discovery experiment, respectively. MetPP not only correctly aligned the spiked-in metabolite standards from the experimental data, but also correctly recognized their concentration difference between sample groups. For analysis of the biomarker discovery data, 15 metabolites were recognized with significant concentration difference between the sample groups and these results agree with the literature results of histological analysis, demonstrating the effectiveness of applying MetPP software for disease biomarker discovery. Availability: The source code of MetPP is available at http://

Olanzapine (OLZ), an effective treatment of schizophrenia and other disorders, causes weight gain and metabolic syndrome. Most studies to date have focused on the potential effects of OLZ on the central nervous system's mediation of weight; however, peripheral changes in liver or other key metabolic organs may also play a role in the systemic effects of OLZ. Thus, the purpose of this study was to investigate the effects of OLZ on hepatic metabolism in a mouse model of OLZ exposure. Female C57Bl/6J mice were administered OLZ (8 mg/kg per day) or vehicle subcutaneously by osmotic minipumps for 28 days. Liver and plasma were taken at sacrifice for biochemical analyses and for comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry metabolomics analysis. OLZ increased body weight, fat pad mass, and liver-to-body weight ratio without commensurate increase in food consumption, indicating that OLZ altered energy expenditure. Expression and biochemical analyses indicated that OLZ induced anaerobic glycolysis and caused a pseudo-fasted state, which depleted hepatic glycogen reserves. OLZ caused similar effects in cultured HepG2 cells, as determined by Seahorse analysis. Metabolomic analysis indicated that OLZ increased hepatic concentrations of amino acids that can alter metabolism via the mTOR pathway; indeed, hepatic mTOR signaling was robustly increased by OLZ. Interestingly, OLZ concomitantly activated AMP-activated protein kinase (AMPK) signaling. Taken together, these data suggest that disturbances in glucose and lipid metabolism caused by OLZ in liver may be mediated, at least in part, via simultaneous activation of both catabolic (AMPK) and anabolic (mammalian target of rapamycin) pathways, which yields new insight into the metabolic side effects of this drug.