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BackgroundNonalcoholic fatty liver disease (NAFLD) is the most common liver disease in the world. Hydrogen sulfide (H2S) plays an important role in physiology and pathophysiology of liver. However, whether exogenous H2S could mitigate the hepatic steatosis in mice remains unclear. The aim of this study is to evaluate the effects of H2S on fatty liver.MethodsC57BL/6 mice were fed with either a high-fat diet (HFD) or a normal fat diet (NFD) for 16 weeks. After 12 weeks of feeding, the HFD-fed mice were injected one time per day with NaHS or saline for the followed 4 weeks.ResultsCompared to NFD, HFD could induce an accumulation of lipids in liver and a damage of hepatic structure. Compared to saline treatment, in the liver of HFD fed mice H2S treatment could significantly (1) recover the structure; (2) decrease the accumulation of lipids including triglyceride (TG) and total cholesterol (TC); (3) decrease the expression of fatty acid synthase (FAS) and increase the expression of carnitine palmitoyltransferase-1 (CPT-1); (4) reduce malondialdehyde (MDA) levels; (5) increase the activities of superoxide dismutase (SOD) and glutathione peroxidase (GPx).ConclusionH2S could mitigate the fatty liver by improving lipid metabolism and antioxidant potential in HFD-induced obese mice.

Six hexacyclic triterpene acids (1-6), named euscaphic acids A-F, and eight known triterpene acid compounds (7-14) were isolated from an ethanolic extract of twigs of Euscaphis japonica. Compounds 8 and 10 were isolated for the first time from a natural source. Triterpenes 1-6 possess hexacyclic skeletons with a 13α,27-cyclopropane ring. Structural elucidation of compounds 1-6 was established by spectroscopic methods, especially 2D NMR techniques ((1)H-(1)H COSY, HMQC, HMBC, and NOESY). Compounds 3, 4, and 14 showed significant cytotoxicity against different cancer cell lines [IC50 = 2.54 (NCI-H460), 3.61 (MCF-7), and 3.27 μM (CEM) for 3, 4, and 14, respectively].

BackgroundErythritol is a four-carbon sugar alcohol with sweetening properties that is used by the agro-food industry as a food additive. In the yeast Yarrowia lipolytica, the last step of erythritol synthesis involves the reduction of erythrose by specific erythrose reductase(s). In the earlier report, an erythrose reductase gene (YALI0F18590g) from erythritol-producing yeast Y. lipolytica MK1 was identified (Janek et al. in Microb Cell Fact 16:118, 2017). However, deletion of the gene in Y. lipolytica MK1 only resulted in some lower erythritol production but the erythritol synthesis process was still maintained, indicating that other erythrose reductase gene(s) might exist in the genome of Y. lipolytica.ResultsIn this study, we have isolated genes g141.t1 (YALI0D07634g) and g3023.t1 (YALI0C13508g) encoding two novel erythrose reductases (ER). The biochemical characterization of the purified enzymes showed that they have a strong affinity for erythrose. Deletion of the two ER genes plus g801.t1 (YALI0F18590g) did not prevent erythritol synthesis, suggesting that other ER or ER-like enzymes remain to be discovered in this yeast. Overexpression of the newly isolated two genes (ER10 or ER25) led to an average 14.7% higher erythritol yield and 31.2% higher productivity compared to the wild-type strain. Finally, engineering NADPH cofactor metabolism by overexpression of genes ZWF1 and GND1 encoding glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase, respectively, allowed a 23.5% higher erythritol yield and 50% higher productivity compared to the wild-type strain. The best of our constructed strains produced an erythritol titer of 190 g/L in baffled flasks using glucose as main carbon source.ConclusionsOur results highlight that in the Y. lipolytica genome several genes encode enzymes able to reduce erythrose into erythritol. The catalytic properties of these enzymes and their cofactor dependency are different from that of already known erythrose reductase of Y. lipolytica. Constitutive expression of the newly isolated genes and engineering of NADPH cofactor metabolism led to an increase in erythritol titer. Development of fermentation strategies will allow further improvement of this productivity in the future.Electronic supplementary materialThe online version of this article (10.1186/s12934-018-0982-z) contains supplementary material, which is available to authorized users.