Study On Intestinal Inflammation And Injury And Expression Of Fungi-related Pattern Recognition Receptors In NAFLD Mice

Background and AimNon-alcoholic fatty liver disease（NAFLD）is a group of metabolic liver injury diseases characterized by excessive fat deposition in hepatocytes.Currently,the pathogenesis of NAFLD is not clear.The objectives of this study were to establish a mouse model of NAFLD using a Western high-fat diet and a mouse model of nonalcoholic steatohepatitis（NASH）using a choline methionine-deficient diet,to examine colonic inflammation and injury in two disease stages,and to examine colonic and hepatic tissue patterns in different disease stages of NAFLD.This observational study was conducted to find out the pattern of specific pattern recognition receptor changes and to provide new ideas and basis for subsequent studies of NAFLD.MethodsWild-type male C57BL/6j mice were randomly grouped into 10 mice per group,including 4W high-fat diet（HFD）,4W control diet（CON）,4W methionine and choline deficient diet（MCD）,and 12W methionine and choline deficient diet（MCD）.The mice were weighed and their general conditions were observed.After the mice were executed,the corresponding specimens were taken and the liver histopathological changes and the degree of steatosis were observed by HE staining and oil red O staining.RT-qPCR was used to detect the intestinal inflammatory factors TNF-α and IL-1β mRNA expression levels,and HE staining was used to observe terminal colon injury and inflammation.RT-qPCR was used to detect the mRNA expression levels of fungi-related pattern recognition receptors in intestinal and liver tissues.Results1.NAFLD mouse model was successfully constructed:HE staining of liver in 4W HFD group showed hepatic steatosis but no inflammatory reaction,HE staining of liver in 12W HFD and MCD groups showed obvious hepatocyte steatosis and inflammatory reaction,and liver oil red O staining was more visualized to support hepatocyte steatosis,4W HFD group mouse model was approximated as NAFL model,12W HFD and MCD mice models were approximated as NASH models.2.Assessment of intestinal inflammatory status in NAFLD mice with different disease states:’the colon lengths of mice in 4W HFD,12W HFD and MCD groups were significantly shorter than those in the CON group（p<0.05）,and the colon shortening was more severe in the 12W HFD group than in the 4W HFD group.HE staining of the terminal colon showed that the colonic tissue of NASH mice had disorganized glandular arrangement,infiltration of inflammatory cells in the mucosal layer,presence of cup cells and reduction of glandular fossa structures,and the expression of pro-inflammatory factor TNF-α was increased in the colon of both NAFL and NASH mice compared with the CON group（p<0.05）.3.Pattern recognition receptor expression:compared with the CON group in the 4W HFD group,the expression of Dectin-3 and TLR2 was decreased and CD36 was increased in liver tissue,and the expression of Dectin-2 and CD36 was decreased and TLR2 was increased in colon tissue.compared with the CON group in the 12W HFD group,the expression of DC-SIGN was decreased in liver tissue,and the expression of Dectin-1,Dectin-2,CD36,TLR2,and Mincle expression was increased in liver tissue,and DC-SIGN,CD36,TLR2,and Mincle expression was decreased in colon tissue.in the MCD group compared with the CON group,Langerin expression was decreased in liver tissue,Dectin-2 and CD36 expression was increased in colon tissue,and DC-SIGN expression was decreased in colon tissue,and CD36 expression was increased in colon tissues,and the differences were statistically significant.Conclusions1.The mouse HFD and MCD diet-induced fatty liver models can well simulate the pathophysiological changes of clinical NAFLD patients,and provide a good experimental model to investigate the mechanism of NAFLD development.2.NAFLD is accompanied by inflammation and injury of the intestinal tract along with hepatic steatosis,and the colonic injury of NAFLD mice is further aggravated with the aggravation of the disease.3.The expression of colonic and hepatic fungal pattern recognition receptors in NAFLD mice is disturbed,and most of the pattern recognition receptors show downregulation in the intestine.