Mengyi Zhou

Results of a 90-day safety assessment study in mice fed a glucan produced by Agrobacterium sp. ZX09.

Salecan is a novel water-soluble glucan produced by Agrobacterium sp. ZX09. It has potential application as a food additive with a unique chemical composition and excellent physicochemical properties. The objective of this study was to investigate the acute and subchronic toxicity of Salecan. The oral LD50 of Salecan in ICR mice was greater than 3000 mg/kg body weight. In the subchronic study, ICR mice (10/sex/group) were fed diets containing 0%, 1.0%, 2.5% and 5.0% of Salecan (weight/weight) for 13 weeks. Based on the results from the subchronic study, the overall health, body weight gain, food consumption and clinical pathology parameters were comparable between the groups feed Salecan and the control. No dose-related effects were observed in the treated animals. The only exception was the observation that blood glucose in female mice fed Salecan was lower than in the control group. In addition, the fecal matter from Salecan fed mice exhibited increased water content versus the control animals. The no observed adverse effect level (NOAEL) of 14478 mg/kg body weight/day was determined. The results from this study support the conclusion that Salecan is non-toxic at the levels tested and does not pose a risk to human health when used in food.

Loss of mPer2 increases plasma insulin levels by enhanced glucose‐stimulated insulin secretion and impaired insulin clearance in mice

The existence of peripheral oscillators has been shown, and they are critically important for organizing the metabolism of the whole body. Here we show that mice deficient in mPer2 markedly increase circulatory levels of insulin compared with wild type mice. Insulin secretion was more effectively stimulated by glucose, and alloxan, a glucose analogue, induced more severe hyperglycemia in mPer2‐deficient mice. Hepatic insulin degrading enzyme (Ide) displayed an obvious day and night rhythm, which was impaired in mPer2‐deficient mice, leading to a decrease in insulin clearance. Deficiency in mPer2 caused increased Clock expression and decreased expression of Mkp1 and Ide1, possibly underlying the observed phenotypes and suggesting that mPer2 plays a role in regulation of circulating insulin levels.

Laxative effects of Salecan on normal and two models of experimental constipated mice

BackgroundConstipation is one of the most common gastrointestinal complaints with a highly prevalent and often chronic functional gastrointestinal disorder affecting health-related quality of life. The aim of the present study was to evaluate the effects of Salecan on fecal output and small intestinal transit in normal and two models of drug-induced constipation mice.MethodsICR mice were administrated intragastrically (i.g.) by gavage with 100, 200 and 300 mg/kg body weight (BW) of Salecan while the control mice were received saline. The constipated mice were induced by two types of drugs, loperamide (5 mg/kg BW, i.g.) and clonidine (200 μg/kg BW, i.g.), after Salecan treatment while the control mice were received saline. Number, weight and water content of feces were subsequently measured. Small intestinal transit was monitored by phenol red marker meal.ResultsSalecan (300 mg/kg BW) significantly increased the number and weight of feces in normal mice. In two models of drug-induced constipation, Salecan dose-dependently restored the fecal number and fecal weight. The water content of feces was markedly affected by loperamide, but not by clonidine. Treatment with Salecan significantly raised the fecal water content in loperamide-induced constipation mice. Moreover, Salecan markedly stimulated the small intestinal transit in both loperamide- and clonidine-induced constipation model mice.ConclusionsThese results suggest that Salecan has a potential to be used as a hydrophilic laxative for constipation.

Salecan diet increases short chain fatty acids and enriches beneficial microbiota in the mouse cecum.

Salecan, a linear extracellular polysaccharide consisting of β-(1,3)-D-glucan, has potential applications in the food industry due to its excellent toxicological profile and rheological properties. The aim of the present study was to evaluate the effects of dietary supplementation with 8% Salecan on the gastrointestinal microbiota in mice. In the Salecan group, the following significant differences (p<0.05) from the cellulose group were found: increased body weight gain, greater mass of cecum and cecal contents, and higher butyrate concentrations in the cecal and colonic contents at wk 4. Moreover, populations of Lactobacillus and Bifidobacterium increased 3- and 6-fold, respectively, in the cecal contents of mice consuming Salecan. These results suggest that the dietary incorporation of Salecan, by providing SCFAs and increasing beneficial microbiota, may be beneficial in improving gastrointestinal health, and have relevance to the use of Salecan as a dietary supplement for human consumption.

Daily variation in global and local DNA methylation in mouse livers.

DNA methylation is one of the best-characterized epigenetic modifications and has an important biological relevance. Here we showed that global DNA methylation level in mouse livers displayed a daily variation where the peak phases occurred during the end of the day and the lowest level at the beginning of the day in the light-dark or dark-dark cycles. Typical repeat sequence long interspersed nucleotide element-1 (LINE-1) had a similar methylation rhythm to global DNA. DNA methyltransferase 3A (DNMT3A) and ratio of S-adenosylmethionine (SAM) to S-adenosylhomocysteine (SAH) brought a relative forward daily variation to global DNA methylation, and the temporary change in ratio of SAM to SAH had no influence on the DNA methylation level. The rhythm of global DNA methylation was lost and DNA methylation level was increased in Per1-/-Per2-/- double knockout mice, which were in accordance with changes of Dnmt3a mRNA levels and its rhythm. Our results suggest that the daily variation in global DNA methylation was associated with the change of Dnmt3a expression rather than ratio of SAM to SAH.

Loss of A1 Adenosine Receptor Attenuates Alpha-naphthylisothiocyanate-induced Cholestatic Liver Injury in Mice

Cholestasis has limited therapeutic options and is associated with high morbidity and mortality. The A(1) adenosine receptor (A(1)AR) was postulated to participate in the pathogenesis of hepatic fibrosis induced by experimental extrahepatic cholestasis; however, the contribution of A(1)AR to intrahepatic cholestatic liver injury remains unknown. Here, we found that mice lacking A(1)AR were resistant to alpha-naphthyl isothiocyanate (ANIT)-induced liver injury, as evidenced by lower serum liver enzyme levels and reduced extent of histological necrosis. Bile acid accumulation in liver and serum was markedly diminished in A(1)AR(-/-) mice compared with wild-type (WT) mice. However, biliary and urinary outputs of bile acids were significantly enhanced in A(1)AR(-/-) mice. In the liver, mRNA expression of genes related to bile acid transport (Bsep and Mdr2) and hydroxylation (Cyp3a11) was increased in A(1)AR(-/-) mice. In the kidney, A(1)AR deficiency prevented the decrease of glomerular filtration rate caused by ANIT. Treatment of WT mice with A(1)AR antagonist DPCPX also protected against ANIT hepatotoxicity. Our results indicated that lack of A(1)AR gene protects mice from ANIT-induced cholestasis by enhancing toxic biliary constituents efflux through biliary excretory route and renal elimination system and suggested a potential role of A(1)AR as therapeutic target for the treatment of intrahepatic cholestasis.

Endogenous A1 adenosine receptor protects mice from acute ethanol-induced hepatotoxicity.

Previous studies have indicated a critical role of adenosine and its receptors in the pathogenesis of liver diseases. The aim of this study was to determine the contribution of A1 adenosine receptor (A1AR) to acute ethanol-induced hepatotoxicity. Wild-type (WT) and A1AR(-/-) mice were intragastrically administered with ethanol (5 g/kg), and hepatic injury was evaluated 6h thereafter. Mice lacking A1AR were more susceptible to ethanol-induced liver damage than WT mice, as evidenced by higher serum transaminase levels and increased extent of histopathological changes. Ethanol induced triglycerides accumulation in the serum and liver, and this accumulation was augmented in A1AR(-/-) mice. Analysis of gene expression in the liver revealed up-regulated mRNA levels of genes related to lipogenesis (including: FAS, SCD1, ACC1, DGAT2, and PPARγ) in A1AR(-/-) mice after ethanol treatment. In addition, lack of A1AR aggravated lipid peroxidation and superoxide dismutase depletion caused by acute ethanol exposure. A subsequent study revealed that, pretreatment with A1AR antagonist DPCPX increases the sensitivity of mice to ethanol-induced liver injury. In conclusion, these results indicated that endogenous A1AR activation protects mice against acute ethanol-induced liver injury by reducing oxidative stress and decreasing lipid accumulation.

Salecan Enhances the Activities of β-1,3-Glucanase and Decreases the Biomass of Soil-Borne Fungi.

Salecan, a linear extracellular polysaccharide consisting of β-1,3-D-glucan, has potential applications in the food, pharmaceutical and cosmetic industries. The objective of this study was to evaluate the effects of salecan on soil microbial communities in a vegetable patch. Compositional shifts in the genetic structure of indigenous soil bacterial and fungal communities were monitored using culture-dependent dilution plating, culture-independent PCR-denaturing gradient gel electrophoresis (DGGE) and quantitative PCR. After 60 days, soil microorganism counts showed no significant variation in bacterial density and a marked decrease in the numbers of fungi. The DGGE profiles revealed that salecan changed the composition of the microbial community in soil by increasing the amount of Bacillus strains and decreasing the amount of Fusarium strains. Quantitative PCR confirmed that the populations of the soil-borne fungi Fusarium oxysporum and Trichoderma spp. were decreased approximately 6- and 2-fold, respectively, in soil containing salecan. This decrease in the amount of fungi can be explained by salecan inducing an increase in the activities of β-1,3-glucanase in the soil. These results suggest the promising application of salecan for biological control of pathogens of soil-borne fungi.