Protective Effect And Mechanism Of Portulaca Oleracea.L Dietary Fiber On Cadmium Exposure In Mice

Cadmium（Cd）is a highly toxic heavy metal pollutant.Due to the diversity of pollution pathways and the long-term,cumulative and irreversible potential toxic effects,foodborne Cd exposure is a serious threat to human health.Portulaca oleracea L.as one of medicine edible plants,contain dietary fiber,protein,minerals and other nutrients,have the functions of anti-inflammatory,anti-antioxidant anti-bacterial and regulating intestinal microecology.Dietary fiber supplement was proved to be an effective chelating heavy metal ion strategy,it can also prevent diseases by regulating the banlance of the gut microbiota.Therefore,this study aims to study the effect and mechanism of Portulaca oleracea.L on alleviating Cd toxicity,so as to develop a new dietary strategy to solve Cd toxicity.The main research results are as follows:In this study,the adsorption capacity of Portulaca oleracea L.whole powder（Por.L）and its insoluble dietary fiber（PIDF）for Cd was measured by simulating gastrointestinal environment in vitro.It was found that PIDF showed stronger adsorption capacity of Cd than Por.L in intestinal environment.Then,we took C57BL/6 mice as the research object,and established the mouse model of Cd exposure through 100 mg/L Cd Cl₂ in drinking water.The results showed that Por.L was more effective than PIDF in reducing Cd accumulation in vivo.The physiological mechanism of Por.L reducing Cd toxicity was further analyzed.It was found that Por.L could reduce Cd induced oxidative stress toxicity by scavenging free radicals and alleviating lipid peroxidation on cell membrane.At the same time,Por.L regulated the gut microbiota,increased the abundance of Lactobacillus and Faecalibaculum,thus regulating the balance and homeostasis of the intestinal environment.PIDF showed anti-Cd toxicity in inhibiting liver and kidney inflammation mediated by TLR4/My D88/NF-κB signal pathway.Based on the observation that the protective effect of Por.L was better than that of PIDF in Cd-exposed mice,we further isolated Portulaca oleracea L.soluble dietary fiber（PSDF）with the"enteric-liver axis"as the entry point.We found that PSDF inhibited intestinal reabsorption and basolateral export of bile-Cd by inhibiting the FXR-FGF15 axis in the small intestine of Cd-treated mice,and decreasing the expression of organic solute transporters OSTαand OSTβon the cell membrane.At the same time,the bile acid synthesizes rate-limiting enzymes of CYP7A1 and CYPB81,which play a negative feedback regulation mechanism,further stimulated the synthesis and secretion of bile acid,and effectively blocked the enterohepatic circulation of Cd.PSDF also protected mucus layer,intestinal epithelium and gut microbiota by inhibiting the FXR-FGF15 axis to reduce intestinal Cd absorption.PSDF played a protective role in maintaining mucus synthesis and the integrity of intestinal epithelial cells,inhibiting the activation of colonic TLR4/My D88/NF-κB signaling pathway,and reducing the release of inflammatory factors（TNF-α,IL-1βand IL-6）.In addition,PSDF could increase the relative abundance of Lactobacillus and Ruminococcaceae＿UCG-014 by regulating the composition and structure of gut microbiota,reduce the relative abundance of Lachnospiraceae＿NK4A136＿group.and increase the production of short-chain fatty acids with anti-inflammatory properties to maintain intestinal microecological balance in Cd-exposed mice.In conclusion,based on the effect of toxic mechanisms induced by Cd and novel diet strategies for restricting metal accumulation and regulating intestinal immunity mediated by Portulaca oleracea L.and its dietary fiber.This study provided a guidance for the scientific analysis of the harm for foodborne Cd and the method of antagonizing the biotoxicity for Cd.