Preliminary Study On The Toxic Effect Of Aflatoxin B₁ On Rat Liver And The Effect Of Chitooligosaccharide On Its Intervention And Mechanism

Aflatoxin B₁（AFB₁）is a highly toxic mycotoxin that can cause liver damage and even liver cancer in humans and animals.The main sources of pollution of the body exposed to AFB₁ are crops and their processed products,which seriously threaten the health of humans and animals.Chitooligosaccharide（COS）derived from natural substances has good anti-oxidation,anti-tumor and immunity-enhancing properties.It is easily soluble in water and easily absorbed by the body.At present,there are many studies on the biological properties of COS,but there are few studies on the prevention of acute liver injury caused by AFB₁.This paper is mainly divided into two parts:The first part is to explore the persistent effects of AFB₁ on rat liver and gene after a single acute injection;Based on the research in the first part,the second part explores the intervention effect of COS on AFB₁-induced acute liver injury and its functional effect on regulatory genes by establishing an animal model.The specific methods and results are as follows:（1）At the phenotypic level,the sustained effects of a single injection of 1（LA group）and 2 mg/kg AFB₁（HA group）on the liver of rats were studied after normal feeding for 2（LA-2d and HA-2d group）and 7 days（LA-7d and HA-7d group）.The effects of AFB₁ on the liver were investigated by rat body weight,liver coefficient and pathological indexes,liver function indexes,antioxidant enzymes SOD and GSH-Px activities,lipid peroxide MDA content and apoptosis rate.The results showed that compared with the control group（CK group）,the liver function index,the content of MDA in liver and the number of hepatocyte apoptosis in the model groups（LA-2d,LA-7d,HA-2d and HA-7d group）increased to the highest on the second day after modeling.However,the liver coefficients changed most significantly on day 7 after modeling.Liver pathology sections showed that liver damage was not alleviated,and the activity levels of antioxidant enzymes GSH-Px and SOD were low.Thus,it can be seen that acute single exposure to AFB₁ has persistent injury effect on rat liver.In conclusion,acute single exposure of AFB₁ has sustained damage to the liver of rats.（2）The effects of a single injection of 1 and 2 mg/kg AFB₁ on liver genes in rats were studied by RNA-Seq technique.By analyzing sequencing data,there were 1246,356,2354 and 855 DEGs in model group compared with CK group,respectively.The DEGs enriched in LA-2d and HA-2d mainly exist in carbohydrate,lipid and amino acid metabolism-related pathways,while the DEGs in LA-7d and HA-7d are mainly in cell cycle regulation,inflammatory response and oxidative response.mechanism enriched.In DEGs,Lama5 and Gtse1 genes related to proliferation,differentiation and metastasis of HCC cells and Fabp4 gene related to inflammatory response were highly expressed in the model group,while Bcl6 gene was highly expressed in the group 7 days after modeling,and the expression level was higher than that in the group 2 days after modeling.Therefore,acute exposure to AFB₁ can cause a large number of gene disorders,but with the extension of the influence time,only one third of the genes still have significant differences.Analysis of their functions revealed that a single acute exposure to AFB₁ persistently affects genes associated with liver disease.（3）The antioxidant activity of COS was detected by DPPH method,and a rat model of acute liver injury was established by single-dose injection of 1 mg/kg AFB₁ to explore the intervention effect of COS on AFB₁-induced acute liver injury.The intervention effect of COS was analyzed by analyzing the changes of body weight,liver coefficient and pathological changes,liver function indexes,antioxidant enzymes SOD and GSH-Px activities,lipid peroxide MDA content and apoptosis rate of rats during the experimental period.The results showed that:COS has strong free radical scavenging ability and high antioxidant activity.COS pretreatment can inhibit AFB₁-induced acute liver injury by increasing antioxidant enzyme activity and inhibiting hepatocyte apoptosis.（4）To investigate the effects of COS preconditioning on the gene expression and function of acutely exposed liver of AFB₁ based on RNA-Seq technology.Analysis of sequencing data found that compared with the control group,the genes in the AFB₁ and HCOS groups contained 1059 and 52 DEGs,respectively.Compared with the AFB₁group,the HCOS group had 965 DEGs.Through the KEGG enrichment analysis,it was found that these genes were mostly enriched in the pathways of metabolism,oxidation and cell cycle regulation.It can be concluded that COS intervention can reduce the influence of AFB₁ on liver genes and alleviate the changes in liver genes function induced by AFB₁.In conclusion,from the analysis of phenotype and genotype,a single acute exposure of AFB₁ can cause persistent liver damage.The number and function of DEGs are also related to the dose of AFB₁ and the duration of influence.In addition,potential genes that can treat liver disease can be found by analyzing persistently affected genes.COS has a good effect on acute injury caused by AFB₁.The intervention mechanism may be that COS can alleviate AFB₁ induced liver metabolic disorder,oxidative stress response and massive proliferation of liver cells.