| In this study,we firstly investigated the growth of Lactobacillus plantarum LZU-J-TSL6 and LZU-S-ZCJ mixes in Astragalus aqueous extracts under different conditions,and obtained fermented Astragalus by submerged fermentation.Subsequently,the active ingredients yield and the in vitro antioxidant capacity of fermented Astragalus were evaluated.The changes of short-chain fatty acids and differential metabolites in the system before and after fermentation were further analyzed by GC-MS and UPLC-MS/MS to elucidate the material basis of fermented Astragalus.Then,the preventive effect of fermented Astragalus on dextran sulfate sodium(DSS)-induced colitis in mice were further explored.To further elucidate the protective mechanism of fermented Astragalus against ulcerative colitis,we evaluated the modulating effects of fermented Astragalus on mechanical,chemical,immune and biological barriers of intestinal mucosa in mice.The results showed that:(1)Under the following conditions,Lactobacillus plantarum LZU-S-ZCJ: LZU-J-TSL6 mixing ratio was 1:3,the concentration of the Astragalus extract was 0.5 g/m L,the inoculation amount was 3%,the fermentation temperature was 36℃,and the fermentation time was 36 h.The growth and metabolism of Lactobacillus plantarum in Astragalus extract was ideal.(2)The total polysaccharide yield significantly decreased,total flavonoid and total acid yield significantly increased.in vitro,the scavenging ability of hydroxyl radical and superoxide anion radical as well as total antioxidant capacity of fermented Astragalus significantly increased.(3)The contents of 7 short-chain fatty acids in fermented Astragalus increased,among which isobutyric acid,butyric acid,acetic acid and isovaleric acid increased most significantly compared with unfermented Astragalus.11 metabolites such as raffinose,progesterone,3,4-dihydroxybenzaldehyde,aminocaproic acid and uridine were greatly increased as differential metabolites in fermented Astragalus.The above metabolites improved the ability of fermented Astragalus to combat colitis and regulated the intestinal mucosal barrier effectively.(4)Prophylactic fermented Astragalus supplementation effectively improved clinical symptoms related to ulcerative colitis such as reduced body weight,shortened colonic length,reduced DAI score,and histopathological lesion.(5)Fermented Astragalus played a protective role in regulating the intestinal mucosal mechanical and chemical barriers by improving the tight junction structure and mucin expression,as well as restoring the apoptosis homeostasis of intestinal cells.(6)Fermented Astragalus played a protective role in regulating the intestinal mucosal immune barrier.On the one hand,it alleviates intestinal inflammation by regulating the balance of cytokines related to the Th1/Th2/Th17/Treg immune axis;on the other hand,it resists intestinal oxidative stress caused by immune disorder by activating Nrf2 signaling.(7)Fermented Astragalus played a protective role in regulating the intestinal mucosal biological barrier by reconstructing intestinal microbiota diversity,inhibiting the abundance of harmful bacteria such as Shigella and Oscillospira,specifically increasing the abundance of Akkermansia and Alistipes,and producing abundant short-chain fatty acids to mediate intestinal inflammation.In conclusion,this study demonstrated that submerged fermentation is an effective technology to improve the disease-suppressive ability of Astragalus.And the fermented Astragalus modulates the four-pronged intestinal mucosal barrier mechanism of mechanical,chemical,immune,and biological barriers,exerting multiple holistic protective effects on the intestinal mucosal barrier,so as to effectively prevent the occurrence of ulcerative colitis.This study laid a foundation for further research on the mechanism of fermented Astragalus in treating ulcerative colitis and provided a microbiological idea for the modernization of traditional Chinese medicine. |
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