| Ganoderma lucidum had been used in medicine for a long time in our country and has been regarded as one of medicinal and edible foods.There are many kinds of Ganoderma lucidum.One of them is Ganoderma atrum(G.atrum)which was also called “Xuanzhi” because of its black cap and stalk.G.atrum was described with slightly sweet taste,flat,non-toxic,and it is good for kindey function,urine metabolism and inappetence in the “Compendium of Materia Medica”.It was reported there are various active constituents in G.atrum,they are polysaccharides,peptides and amino acids,triterpenes,alkaloids and nucleosides,sterols,furans and inorganic elements,etc.,in which polysaccharide is an important constituent with many functional activities.Our team had confirmed the structures and conformation characteristics of polysaccharides from the fruiting body of G.atrum.Moreover,we also found that polysaccharide from G.atrum(PSG)have many functional activities,such as immunomodulation,anti-tumor,anti-aging,hypoglycemic effects and so on.Our previous results indicated that PSG can significantly improve the glucose and lipids metabolism and alleviate the related complications in type 2 diabetic rats.However,the studies on the digestion and fermentation behaviors of PSG and the mechanisms of PSG based on gut microbiota in type 2 diabetic rats have not yet been carried out.Therefore,PSG was subjected for these studies,its digestion and fermentation behaviors in vitro and in vivo and its mechanisms on type 2 diabetic rats based on gut microbiota were discussed.The main contents and conclusions were summarized as follows:1.The gastrointestinal digestion behaviors and fermentation behaviors with gut microbiota of the polysaccharide from G.atrum in vitro were studied with the simulated digestive and fermentative methods which were established in our laboratory.The results showed the molecular weight of PSG steadily decreased from 198.00 ± 0.30 k Da to 147.10 ± 0.30 k Da and non free monosaccharides generated throughout simulated gastric and intestinal digestion in vitro,and PSG promoted the production of short chain fatty acids(SCFAs)and declined p H in the fermentation with gut microbiota in vitro.These results may provide information that PSG was not entirely digested in gastric and intestinal digestion and was mainly degraded in the large intestine and promoted the production of SCFAs.2.The safety and fermentation behaviors of PSG in healthy mice which were taken different doses of PSG orally were studied.The results found that PSG has no side effects on healthy mice,but can reduce fecal p H,increase fecal moisture and promote the production of SCFAs.The fecal p H in the low dose of PSG group(PSGL),medium dose of PSG group(PSG-M)and high dose of PSG group(PSG-H)decreased to 8.40 ± 0.40,8.50 ± 0.30,and 8.40 ± 0.10,respectively.The concentrations of SCFAs in PSG-H group was significantly higher than control group.PSG can also significantly reduce the p H in colonic contents and promote the production of SCFAs.The colonic p H in PSG-L,PSG-M and PSG-H groups decreased to 7.50 ± 0.32,7.56 ± 0.32 and 7.33 ± 0.78,respectively.Moreover,PSG promoted the SCFAs in caecal contents,but increased the caecal p H.The caecal p H in PSG-L,PSG-M and PSG-H groups increased to 7.75 ± 0.11,7.74 ± 0.29 and 7.73 ± 0.26,respectively.3.The effects on intestinal health of PSG in type 2 diabetic rats were evaluated.The type 2 diabetic rats(blood glucose level ? 11.1 mmol/L)were successfully constructed by combining high-fat diet with injection of streptozotocin(STZ)in tail vein.The results indicated that PSG could effectively reduce the p H in feces,caecal and colonic contents in type 2 diabetic rats,promote the production of SCFAs in feces,caecum and colon and increase the fecal moisture.The high dose of PSG(PH)had better effects,the p H in feces,caecal and colonic contents of PH group were 6.53 ± 0.13,7.88 ± 0.18,and 7.34 ± 0.34,respectively.While the concentrations of total SCFAs in feces,caecum and colon of PH group were 4.40 ± 1.18,11.16 ± 0.63 and 5.77 ± 1.49 m M,and the fecal moisture of PH group was 60.00 ± 2.36 %.These results proved that PSG could improve type 2 diabetic rats by promoting the production of SCFAs and declining intestinal p H through its fermentation in vivo.4.The effects of PSG on colon microbiota in type 2 diabetic rats and the information about the key microbiota were explored with two kinds of analytical methods which are denaturing gradient gel electrophoresis(DGGE)and 16 S r RNA high-throughput sequencing.The results with the two methods were consistent.PSG could significantly alter the colon microbiota composition and increase the ? diversity indexes.The ? diversity analysis showed that the composition of colon microbiota was significantly different from the model group after administration of PSG.The LEf Se analysis showed that PSG could promote the growth of beneficial bacterium,such as Bifidobacterium,Turicibacter,Blautia,Coprococcus and so on,and PSG could inhibit the growth of harmful bacterium such as Enterococcus,Dorea,Leuconostoc,et al.PICRUST analysis found that PSG could significantly affect a variety of pathways activities which including carbohydrates digestion and absorption,mineral absorption,glycan biosynthesis and metabolism and so on.In addition,it was also found that colon microbiota genera with relative abundance higher than 0.1% is significantly related to diabetes-related indicators,including body weight,fasting blood glucose and SCFAs.These results indicated that PSG could alleviate the symptoms of type 2 diabetic rats by regulating the composition of colon microbiota and the change of key microbiota.These results suggested that PSG was not entirely digested in gastric and intestinal digestion and was mainly degraded in the large intestine and promoted the production of SCFAs.PSG could alleviate the symptoms of type 2 diabetic rats by regulating the composition of colon microbiota and the change of key genera. |
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