Study On The Mechanisms Of TiO₂ NPs Damage On Liver And Intestines In Metabolic Syndrome Mice And Its Intervention With Probiotics

Titanium dioxide nanoparticles（TiO₂ NPs）is a loosen powder with white color,due to the excellent anti-bacterial,anti-ultraviolet,whitening and other properties of the TiO₂ NPs,they were widely used in the fields of the foods,medicine,personal care and so on.People were ingested numerous TiO₂ NPs by direct or indirect pathway because the extensively used of TiO₂ NPs.Therefore,the safety of the TiO₂ NPs has attached the researchers concern.Metabolism syndrome（Met S）is a kind of pathological condition which the body metabolism of carbohydrates,fat or protein is disordered.Due to the TiO₂ NPs was commonly used in food and medicine industry,the opportunities to contact with TiO₂ NPs was higher by the population who suffered Met S disease than normal person.However,the recent toxicological researches about TiO₂ NPs was commonly focus on the healthy body,while little attention was paid to the Met S population.The aimed of this project was to assess the safety risk of the TiO₂NPs to the Met S disease populations and put forward a probiotic intervention strategy.This thesis reviewed the studies on toxicity and mechanism to hepatic and intestinal of TiO₂ NPs to the healthy population and a part of diseased group,and the advantages of probiotic intervention strategies.This study proved the TiO₂ NPs-induced aggravated effects of Met S mice liver and intestines inflammatory damage by animal experiment.Next,we explored the Lactobacillus rhamnosus GG（LGG）to intervened the toxicity effect of TiO₂ NPs to the Met S mice’s hepatointestinal injury and gut microbiota disorder.We designed a fecal microbiota transplantation（FMT）experiment,which proved the mechanism function of gut microbiota in the liver and intestinal damage induced by TiO₂ NPs in Met S mice.The content of each chapter is described below:The first chapter:We summarized the adverse effects and mechanisms of TiO₂NPs on liver and intestinal barriers in healthy bodies and some disease groups,and the probiotics intervention strategies and its research progress.The second chapter:To explore the aggravating effect of oral exposure of TiO₂NPs on liver and intestinal damage in Met S mice.This study comprehensively assessed the mice’s body indexes,glucose tolerance,histopathological of liver and intestines,accumulation of the TiO₂ NPs and endotoxin in the liver,inflammation and oxidative stress response in the liver and intestines before and after exposure.The results found that exposure with TiO₂ NPs did not affect the formation of Met S models.However,the changes in liver function indicators of Met S mice have increased,liver and intestinal histopathological damage have increased obviously,and the oxidative stress response in liver and intestines have increased significantly.After exposure to the same dose of TiO₂ NPs,the levels of Ti element and endotoxin accumulation in the liver of Met S mice was increased significantly,which may be due to TiO₂ NPs-induced a significant increase in intestinal permeability,and a more significant reduction of tight junction proteins and genes expression.Therefore,resulting in more TiO₂NPs and endotoxin migrated to the liver.The above results demonstrated that TiO₂NPs could further aggravate liver and intestines damage in Met S mice.The third chapter:To study the intervention and protection effect of probiotic LGG on liver and intestinal inflammatory damage caused by TiO₂NPs in Met S mice.This study comprehensively evaluated the body weight,epididymal fat index,glucose tolerance and blood lipid levels of mice before and after exposure.The experimental results showed that LGG could effectively inhibit the formation of Met S which caused by high fructose drinking.In addition,this work assessed the tissue histopathological,hepatic and colon inflammation,colonic tight junction.For the Mte S mice which exposed TiO₂NPs.After intervening the LGG,the results showed that the liver function indicators was normalized,the liver and colon histopathological injuries was recover,the fecal and serum endotoxin levels was reduced,the hepatic and colonic inflammatory cytokine levels was decreased,the levels of anti-inflammatory factors was increased,and the colonic tight junction related protein genes was increased significantly.The above results suggested that LGG could improve the mice metabolic disturbance induced by fructose,and it also relieve the TiO₂NPs-induced liver and intestines inflammatory injury in Met S mice.The fourth chapter:To explore the effect of TiO₂ NPs on gut microbiota and the LGG intervention in Met S mice,the 16S rDNA high-throughput sequencing was used to analyze the alteration of mice gut microbiota.The results showed that TiO₂ NPs could further aggravate changes inαdiversity andβdiversity of gut microbiota in Met S mice.we found that the number of different bacterial flora was increased further compared with normal mice;the relative abundance of bacteria which promoted inflammation was increased significantly;and the prediction and analysis results of KEGG（Kyoto encyclopedia of genes and genomes）metabolic pathways showed that TiO₂NPs could further promote metabolic disorders in Met S mice.After supplementing LGG,the structural and functional changes of the above-mentioned gut microbiota were effectively inhibited.The above results suggested that LGG could inhibit the TiO₂NPs-induced gut microbiota disorder in Met S mice.The fifth chapter mainly explored the mechanism of exacerbating liver and intestinal damage induced by TiO₂NPs in Met S mice.In this study,the gut microbiota of Met S mice exposed to TiO₂ NPs was transplanted to a receptor mouse that scavenged their intestinal microbiota before experiment,and then comprehensively assessed the liver and intestinal damage of receptor mice.It was found that the liver function indexes of the receptor mice were abnormal,the serum endotoxin level was significantly increased,the liver and colon tissue pathology was significant alteration,and the liver and colon inflammatory cytokine levels were significantly increased.The above results showed that the gut microbiota plays an important mediatize role in exacerbating liver and intestinal damage induced by TiO₂ NPs in Met S mice.In summary,this study found that TiO₂ NPs could exacerbate liver and intestine inflammatory injury in Met S mice.TiO₂ NPs could further disrupt gut microbiota disorders in Met S mice.After the LGG intervention,the TiO₂NPs-induced inflammatory damage of the liver and intestines in Met S mice was effectively inhibited,and the structure and function of the gut microbiota were also effectively restored.Moreover,the FMT results suggested that gut microbiota may mediate TiO₂ NPs-induced liver and intestinal inflammation damage in Met S mice.