Fat Reduction Function Of Flammulina Velutipe Dietary Fiber Analyzed By Intestinal Flora-metabolomics-proteomics

Flammulina velutipes(F.velutipes),as the third largest edible fungus in the world,is widely distributed in China.It has many physiological functions such as immune regulation,anti-oxidation and blood lipid reduction,etc.F.velutipes is rich in dietary fiber(DF),which has great capacity of water and oil holding.So it could increase satiety,promote gastrointestinal peristalsis,reduce lipid accumulation and reduce the time of toxins staying in the body.At present,the pharmacological activity of DF has been studied extensively at home and abroad.But the mechanism of reducing fat is still unclear in F.velutipes DF.In this study,to evaluate the effect of reducing fat in vivo,DF were extracted from F.velutipes fruit bodies,and its physicochemical properties,content determination,structural characterization were systematically studied with techniques of TMT quantitative and LC-MS/MS and so on.The F.velutipes DF(Fv-DF)was extracted from the fruiting body of F.velutipes by alkali extraction,the extraction rate was 27%(w/w),the water holding capacity was 7.52 ± 0.39 g/g,the oil holding capacity was 1.44 ± 0.23 g/g,and the swelling capacity was 6.90 ± 0.56 m L/g through physical and chemical tests;PMP-HPLC method was used to detect monosaccharide composition,and glucose was the highest monosaccharide in Fv-DF.Acid,alkali and salt methods were applied to detect the content of cellulose,hemicellulose and lignin,respectively.The content of cellulose was the highest,reaching 63.22 ± 1.71%.At the same time,the content of soluble DF(SDF)and insoluble DF(IDF)was measured.The content of SDF was 2.16 ± 0.1%,and the content of IDF was 77.02 ± 0.02%.Then,XRD,FT-IR and DLS were used to detect and analyze that there were crystalline and amorphous diffraction peaks in the structure of Fv-DF,and there were absorption peaks characterized by cellulose,hemicellulose and lignin.The solubility is not good in aqueous solution.Obese rat models were established with high-fat diet.Then Fv-DF(2,1.5 and 1 g/kg in high,medium and low dose groups)was given for 6 weeks.It was found that Fv-DF could reduce the weight,organ index,BMI index and Lee,s index of obese rats caused by high-fat diet,reduce the levels of total cholesterol(TC),triglyceride(TG)and low-density lipoprotein(LDL-C)and increase the level of high-density lipoprotein(HDL-C)in serum,increase the activity of glutathione peroxidase(GSH-Px)and decrease the content of malondialdehyde(MDA)in liver,improve the pathological changes of liver and reduce the enlargement of adipose cells in adipose tissue.Omics technique and association analysis were used to further explore the mechanism of fat reduction in Fv-DF.Firstly,through proteomic analysis,it was found that Fv-DF could regulate the expression of SIRT3,PLIN2 and ISOC1 proteins and participate in such signal pathways of tra nscriptive misregulation in cancer,calcium signaling pathway and phospholipase D signaling pathw ay,which play a role in regulating energy metabolism,enhancing fat decomposition,reducing food intake and reducing obesity.Then,the non targeted metabonomic analysis found that the Fv-DF reg ulated the level of lipid and amino acid metabolites in serum and participated in the signaling pat hways of biosynthesis of unsaturated fatty acids,linear acid metabolism,spingolipid metabolism an d tryptophan metabolism,which play a role in reducing lipid accumulation.16 S r DNA technology was used to analyze the changes of intestinal microbiota,and it was found that Fv-DF could impr ove the abundance of beneficial bacteria which reduce the lipid accumulation and weight of rats,s uch as Lachnospiraceae＿NK4A136＿group,Roseburia,Eubacterium＿ruminantium＿group,Bacteroides,Alloprevotella and Allobaculum.Thus,Fv-DF could regulate the level of blood lipid and oxidative stress in obese rats,and reduce the organ index of obese rats to reduce weight.Fv-DF also could increase the expression of key proteins,regulate the level of lipid and amino acid metabolites in serum,regulate the abundance of beneficial flora,reduce the abundance of harmful flora,and regulate lipid metabolism.Further omics association analysis showed that there was a significant correlation between key proteins and differential metabolites,as well as between bacterial populations and differential metabolites.It was concluded that SIRT3 might regulate bacterial populations of Bacteroides and Alloprevotella.