| Hyperlipidemia is a key risk factor in inducing fatty liver,hypertension,atherosclerosis and cerebrovascular diseases.It has been demonstrated that the polysaccharide of some mushrooms has the activity of inhibiting lipid accumulation,however,little are known about what is the mechanism behind it in vivo.Our previous studies have verified that polysaccharide(PEPE)from fruiting bodies of Pleurotus eryngii(King Oyster Mushroom)are capable of decreasing the lipid content.In this study,we have set up a P.eryngii mycelium solid-state fermentation approach to produce the polysaccharide(PESF)of P.eryngii,which showed a similar lipid-lowring efficacy with polysaccharide(PEPE)from fruiting bodies;Meanwhile,through building constitutive over-expressed key genes,production of the polysaccharide PESF was increased significanly.Lastly,we have investigated the lipid-lowering efficiency and mechanism of the polysaccharide(PESF)of P.eryngii mycelium by solid-state fermentation by using several animals and cell-line models and verified the correlation between the lipid-lowering activity and the changes of gut microbiome structure;The results can be summaried as following:1.The P.eryngii polysaccharide is obtained by mycelium solid-state fermentation using lignocellulosic waste,corn-cob and wheat bran.HPLC assays indicate that PESF has a similar composition to that of PEPE.Meanwhile,PESF has no detectable toxicity and is able to significantly inhibit foam-cell formation in murine macrophage cells(RAW264.7)induced by oxidized low density lipoprotein.It indicated that P.eryngii mycelium solid-state fermentation can be used as an economic and environmental mode of production for the active polysaccharide of inhibiting lipid accumulation.2.Based on the whole genome sequencing data of P.eryngii,the key enzyme gene sequences in the pathway of P.eryngii polysaccharide synthesis,including UGP,PGM,laccase,were blasted and cloned,by referring to informations about other species.Four modificated strains were build by genetic engineering method,which was used to increase production of polysaccharide.3.PESF’s lipid-lowering efficiency and mechanism were detected in zebrafish and mice models.It indicates that PESF has the in vivo activity of inhibiting lipid accumulation not only significantly reducing lipids accumulation in the body of zebrafish larvae induced by high fat diet(HFD),but also able to significantly decreasing accumulation of lipids in livers induced by HFD through blocking gut lipid attachment and absorption in both zebrafish larvae and adult models.Furtherly,in a high-fat-load mouse model,PESF remarkably decreased the lipid levels of total triglyceride,and low-density lipoprotein cholesterol.Our findings suggest that PESF can be used as a valuable lipid-lowering food additive or raw materials for producing lipid-lowering drugs for hypolipidemic and hepatoprotective treatments.4.In the mice hyperlipidemic model,16S rRNA gene sequencing technique was used to analyze the changes of the gut microflora structure effected by PESF.And it was confirmed that PESF could regulate and restore the gut microbiome structure ecological imbalance and dysfunction caused by HFD to normal.PESF could focus on some kinds of bacterium in gut microbiome,significantly promoted the growth of the Lactobacillus genus,and inhibited the growth of the Staphylococcus,Aerococcus,Corynebacterium genus,also could promote the growth of Bacteroidales_S24-7,Lachnoclostridium,Enterorhabdus and inhibited the growth of Turicibacter.PESF could improve and restore the disorder of transport of carbohydrates and amino acids metabolism in the gut microbiome caused by a HFD.5.The correlation between the changes of gut microbiome structure and the changes of blood lipids after the intervention of PESF on HFD in mice model were analyzed,which indicated that the effect of PESF on blood lipids was consistent with that on the structure of gut microbiome.The Lactobacillus whose growth was promoted by PESF significantly showed negatively correlated with blood lipids(TG,LDL),while,the Staphylococcus,Aerococcus,Corynebacterium whose growth was inhibited by PESF showed positively correlated with blood lipids(TC,LDL,etc.).Collectively,to our knowledge,findings in this study firstly incidate that the Pleurotus eryngii polysaccharide is able to be increasd by the genetically engineered overexpressed strains.PESF has the activity of lowering blood lipid through regulating the structure of gut microbiome and inhibiting the absorption of exogenous lipids;Our findings provide an important evidence for the close relationship between the polysaccharide and gut microbiome. |
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