Gut Microbiota-mediated Anti-obesity Effects And Mechnistic Insights Of Protein-bound ?-glucan From Coriolus Versicolor

Coriolus versicolor(CV)has been traditionally used as edible fungi in China with high medical value.The bioactive component of CV is considered as polysaccharopeptides(polysaccharide-peptide complexes).The widely studied polysaccharopeptides,namely PSP and PSK,were mainly isolated from the deep layer-cultivated mycelia of CV and showed anti-inflammatory,antioxidant,analgesic,immunomodulatory and antitumor effects.Actually,the fruiting bodies of CV are the main source when used as functional food.Nevertheless,rare information about the chemical structures and biological activities especially on anti-obesity of polysaccharides from this medical part is available.Therefore,this project has conducted in-depth research on the anti-obesity effect and mechanism of PBG extracted from the fruiting bodies of CV.Firstly,the dried fruiting bodies of CV were processed,boiled with hot water,precipitated with ethanol,purified by DEAE Fast Flow chromatography and Superdex-200gel-permeation chromatography,and a protein-bound ?-glucan(named as PBG)was obtained.The chemical structure was well elucidated with overall consideration of monosaccharide composition,amino acid composition,methylation analysis,FT-IR and1D/2D-NMR spectra data.With molecular weight of 54 k Da,the polysaccharide fraction PBG was composed of a(l?4)-?-/(1?3)-?-D-glucopyranosyl group as backbone with branches attached at O-6 site.The amino acid moiety was mainly composed of alanine,methionine,histidine,tyrosine,aspartic acid,tryptophan and lysine.Secondly,the anti-obesity effects of PBG were evaluated by examining the changes of body fat distribution and accumulation,adipocytokines,inflammatory cytokines and expression of intestinal barrier related proteins in obese mice.The results showed that PBG treatment apparently attenuated fat area in high fat diet(HFD)-fed mice,and dramatically reduced the triglyceride contents,total bile acid,leptin,TNF-?,IL-1?,IL-17 A and IL-6 in serum.The adiponectin content was correspondingly increased and hepatic lipid droplets were decreased.Moreover,after PBG treatment,the serum LPS levels in HFD-fed mice were significantly reduced,and the expression of the tight junction components,zonula occludens-1 and occludin-1 was increased.These results above indicated that PBG has an potent anti-obesity effects and anti-inflammatory by improving the intestinal barrier integrity and thus decreasing the leakage of microbial LPS from gut into circulation.Thirdly,the regulatory effects of PBG on gut microbiota in HFD-induced obese mice were explored by fecal transplantation from obese to lean mice using 16 S RNA analysis.The data showed that high fat diet could induce obesity with upregulation of Firmicutes/Bacteroidetes(F/B)ratio.The microbial regulation of PBG treatment on HFD-induced mice was based on decrease of LPS-derived bacteria Proteobacteria and Desulfovibrio,thereby reducing the LPS content rather than on the F/B ratio.More importantly,PBG could specifically promote the growth of probiotic Akkermansia.Subsequently,the in vitro fermentation and transcriptome sequencing techniques were conducted to analyze the mechanism by which PBG could promote the colonization of Akkermansia.The results suggested that PBG indirectly promoted the growth of Akkermansia by improving the intestinal environment,stimulating the lipid metabolism of the host through several signaling pathway including arachidonic acid metabolism,linoleic acid metabolism,ether lipid metabolism,glycolipid metabolism,and bile acid secretion.Finally,we investigated whether PBG had an anticancer effect on obesity-related complication through Akkermansia regulation.An obese tumor model was constructed and the mice were treated with PBG alone or combined with 5-fluorouracil(5-FU).Compared with 5-FU group,the combination therapy of 5-FU and PBG showed significant inhibition on tumor growth and considerable increase of Akkermansia content,indicating that PBG exert its anti-obesity effects in combination therapy by increasing the content of Akkermansia.In addition,at the early stage of obese tumor mice,Akkermansia could inhibit the tumor growth,while at the late stage,Akkermansia showed compromised anticancer effects.All in all,PBG exhibited anticancer and anti-obesity effects in combination therapy by regulating gut microbiota profile.Taken together,in this project,we have for the first time identified a protein-bound?-glucan(PBG)from the dried fruiting bodies of Coriolus versicolor.The excellent anti-obesity effects of PBG have been confirmed and the mechanism of microbial regulation properties has been elucidated.Our results will pave the way to the products development of Coriolus versicolor,especially providing valuable scientific proofs for the development of health care products and clinically used anticancer adjuvant.