Mechanism Of Solid-state Fermented Barley Bran On Improving Intestinal Barrier In High-fat Diet Mice

Barley bran has health benefits such as promoting gut microbiota balance,maintaining intestinal functional homeostasis,and improving obesity and metabolic syndrome.Fermentation can promote the release and transformation of active ingredients in food,which is beneficial for improving functional quality.Previous studies have shown that the extract of fermented barley bran by L.plantarum dy-1 had a significant alleviating effect on lipid deposition in Hep G2 cells.To further clarify the functional characteristics and health promotion mechanisms of fermented barley bran by L.plantarum dy-1,this paper constructed C57BL/6J obese mouse model based on high-fat diet,and explored the effects and pathway of solid-state fermented barley bran(SFBB)by L.plantarum dy-1 on lipid metabolism,liver inflammation and intestinal barrier function in mice.Furthermore,combined with faecal microbiota transplantation,the mechanism of SFBB improving intestinal barrier function by regulating gut microbiota was studied.This could provide a certain research foundation and experimental basis for the development of related health products.The main research content and results are as follows:1.SFBB was prepared with L.plantarum dy-1 and the effects of solid-state fermentation on the main components of barley bran were studied.The results showed that the solid-state fermentation conditions for L.plantarum dy-1 were as follows:inoculation amount was 1×10~6 cfu/m L,solid-liquid ratio was 1:1,fermentation time was 72 hours;after fermentation,the polysaccharide composition of barley bran changed significantly,the relative molecular weight decreased from 372 k Da before fermentation to 26.6 k Da,the glucose content in the monosaccharide composition decreased significantly by 44.50%,the arabinose and galactose content increased by3.80 and 3.87 times,respectively,and the xylose content increased from 0 to 15.63%;the results of high-performance liquid chromatography-mass spectrometry analysis showed that solid-state fermentation of L.plantarum dy-1 changed the types and content of free and bound phenolic substances in barley bran,mainly reflected in a decrease in the free content of phenolic acids such as gallic acid and ferulic acid,and a significant increase in the bound content of benzoic acid and 2,4-dihydroxybenzoic acid.2.C57BL/6J obese mouse models were established by high-fat diet to study the effect of SFBB on lipid metabolism and other indicators in obese mice.The correlation between SFBB regulation of gut microbiota and improvement of intestinal barrier was analyzed.The results showed that compared with mice fed with high-fat diet,RBB and SFBB both could effectively reduce the levels of triglyceride(TG),total cholesterol(TC)and low-density lipoprotein(LDL-C)in serum and liver,and increase the content of high-density lipoprotein(HDL-C)in serum;they both could downregulate expression of pro-inflammatory factors,IL-1β、IL-6、TNF-αin the liver and colon and alleviate liver inflammation and intestinal immune barrier damage caused by high-fat diet by suppressing TLR4/My D88/NF-κB pathway and activating Nrf2/HO-1pathway;simultaneously reducing serum lipopolysaccharide levels,increasing colon villus length,and upregulating the relative expression of intestinal tight junction protein m RNA and protein;compared with RBB group mice,the serum lipopolysaccharide level in SFBB group mice was significantly reduced by 24.95%,and the m RNA and protein expression levels of intestinal tight junction protein ZO-1 increased by 0.61 and0.42 times,respectively.The expression levels of NF-κB and TLR4 decreased by 38.35%and 39.58%,respectively,indicating that SFBB had a more significant function in improving intestinal barrier;The 16S r RNA sequencing results showed that compared with RBB,SFBB significantly increased the relative abundance of beneficial bacteria such as Fecalibacterium,Lactobacillus,Romboutsia,and Roseburia,while reducing the relative abundance of harmful bacteria such as Clostridium sensu stricto 1 and Parvibacterium;Spearman analysis showed that the regulatory effect of SFBB on gut microbiota was significantly correlated with intestinal barrier function indicators.3.Antibiotic treated mice were fed in the same cage with barley bran diet obese mice,and faecal microbiota transplantation experimental models were established to study the effects of SFBB combined with faecal microbiota transplantation on lipid metabolism,liver inflammation,and other factors in high-fat diet mice.Furthermore,the mechanism of SFBB improving intestinal barrier by regulating gut microbiota was clarified.The results showed that faecal microbiota transplantation combined with barley bran diet significantly improved lipid metabolism disorders,liver inflammation,intestinal barrier damage,and gut microbiota imbalance.Compared with the SFBB group,the mice cohoused with SFBB(Cohoused-SFBB)group had a 30.85%decrease in serum lipopolysaccharide content and a 15.15%decrease in the relative expression of the inflammatory gene IKK-β,the expression levels of ZO-1 m RNA and protein increased by 0.23 and 0.39 times,respectively;the 16S r RNA analysis results showed that compared with SFBB group,the relative abundance of beneficial bacteria Bifidobacterium and Parasutterella increased in the Cohoused-SFBB group.This further indicated that SFBB could improve intestinal barrier function by regulating the gut microbiota.