As one of emerging high
As one of emerging high-throughout methods, metabolomics detects metabolites which are ultimate response of biological systems to environmental changes . Metabolomics uncovers metabolic alteration at the systems level. Comparison of global metabolic profiling reflects some unidentified biological features. Gas chromatography/mass spectrometry (GC/MS), liquid chromatography/mass spectrometry, capillary electrophoresis/mass spectrometry and nuclear magnetic resonance are four commonly used analytical platforms . GC/MS enables the separation, identification and quantification of volatile metabolites. Relative strengths of GC/MS are high sensitivity, high reproducibility, mature technology and extensive public databases available for small molecule identification . Metabolomics has been applied to identify candidate biomarkers and investigate the underlying mechanisms of alcoholic liver injury [17,18]. However, the effect of AR inhibitor on alcoholic steatosis has never been deciphered by metabolomics.
Materials and methods
Discussion Disruption of metabolic homeostasis by ethanol contributes to alcoholic fatty liver. Our data revealed the therapeutic effect of AR inhibitor on alcoholic liver steatosis in a mouse model. A significant reduction of sorbitol demonstrated AR was repressed in mice with AR inhibitor treatment. Accordingly, reduced protein expression of AR in mice with AR inhibitor treatment was observed . Previous studies have highlighted the roles of glutathione peroxidase-1 and stearoyl-CoA desaturase 1 in ethanol-induced damage [34,35]. AR involves in carbohydrate metabolism, whereas glutathione peroxidase-1 and stearoyl-CoA desaturase 1 involve in amino AS 602801 metabolism and lipid metabolism, respectively. It is therefore critical to understand how AR inhibition results in a therapeutic intervention for alcoholic steatosis. We first presented the metabolic alterations in pathological condition. Increased myristic acid, palmitic acid, stearic acid and oleic acid indicate that fatty acid biosynthesis is promoted by ethanol. High fatty diet enhances ethanol-induced steatosis in a mouse model of chronic liver injury . The deficiency of stearoyl-CoA desaturase 1 that catalyzes the conversion of stearic acid to oleic acid alleviates alcoholic liver injury in mice . Steatosis, multiple metabolites, metabolite supplementation and gene knockout collectively indicate fatty acid biosynthesis is a key player in alcoholic fatty liver. Additionally, myristic acid, palmitic acid, stearic acid and oleic acid didn't change in ARI group. This suggests AR inhibitor doesn't affect fatty acid biosynthesis. We next described fatty acid biosynthesis in the therapeutic condition. Decreased myristic acid, palmitic acid and stearic acid in saturated fatty acid biosynthesis were observed, while oleic acid in unsaturated fatty acid biosynthesis didn't change in ethanol + ARI group. This indicates AR inhibitor alleviates ethanol-induced steatosis by inhibiting saturated fatty acid biosynthesis. To address whether carbohydrates provide substrates for fatty acid biosynthesis, we assessed carbohydrate metabolic pathways. Metabolites except D-myo-inositol and D-xylitol in galactose metabolism, pentose phosphate pathway and pentose and glucuronate interconversions were induced by ethanol. This suggests galactose metabolism, pentose phosphate pathway and pentose and glucuronate interconversions are promoted in ethanol group. It was interesting that the up-regulation of galactose metabolism, pentose phosphate pathway and pentose and glucuronate interconversions were in agreement with increased fatty acid biosynthesis in ethanol group. Moreover, ethanol enhances hepatic glycolysis that links carbohydrate metabolism with fatty acid biosynthesis and decreased phosphorylation of acetyl-CoA carboxylase in mice [37,38]. In light of these observations, we propose the notion that metabolic flux comes from carbohydrate metabolism is one of the reasons why increased fatty acid biosynthesis is seen in ethanol group. AR inhibitor reduced d-galactose, d-glucose, d-mannose and sorbitol accounted for 80.0% of altered metabolites in galactose metabolism. This suggested AR inhibitor impaired galactose metabolism. Metabolites in galactose metabolism, pentose and glucuronate interconversions and pentose phosphate pathway were reduced by ethanol and AR inhibitor. This indicates galactose metabolism, pentose and glucuronate interconversions and pentose phosphate pathway are inhibited in ethanol + ARI group. The down-regulation of carbohydrate metabolic pathways and saturated fatty acid biosynthesis generates the hypothesis that AR inhibitor suppresses saturated fatty acid biosynthesis by preventing carbon metabolic flux. Reduced sorbitol and d-fructose were both biomarkers in ethanol + ARI group. Importantly, exogenous addition of sorbitol validated the positive role of sorbitol in alcoholic steatosis in vitro. The level of stearic acid was induced by synergy effect of ethanol and sorbitol. This suggests ethanol increases fatty acid biosynthesis via elevation of sorbitol. A recent work reported that the level of fatty acid synthase was significantly higher in livers of mice given fructose-ethanol diet than ethanol diet . These imply AR inhibitor can inhibit saturated fatty acid biosynthesis via suppressing sorbitol and d-fructose.