[Changes in hepatic phase Ⅱ detoxification enzymes and their mechanism in metabolic associated steatohepatitis (MASH) induced by MCD diet in mice].

Objective: To investigate the changes in hepatic phase II detoxification enzymes and their mechanism in metabolic associated steatohepatitis (MASH) induced by a methionine-choline-deficient (MCD) diet in mice. Methods: Ten C57BL/6J mice were randomly divided into two groups, with five mice in each group, and fed with a control diet (NCD group) and a methionine-choline-deficient diet (MCD group) for four consecutive weeks to establish the MASH model in mice. Mice body weight was recorded weekly. Mice peripheral blood and liver tissue samples were collected after four weeks. The liver histopathological changes were observed by hematoxylin-eosin staining and Sirius red staining in liver tissue. The levels of plasma alanine aminotransferase (ALT), aspartate aminotransferase (AST) and triglycerides were measured by an automatic biochemical analyzer. Triglyceride and total cholesterol were used to evaluate the lipid accumulation condition in the liver of mice with Oil red O staining. Real-time fluorescence quantitative PCR was used to detect the expression of liver inflammatory factors interleukin (IL)-1β and monocyte chemoattractant protein-1 (MCP-1) condition. Transcriptome sequencing and bioinformatics were used to analyze the changes in gene expression profiles in the liver of mice and screen differentially expressed genes. The expression conditions of phase Ⅱ detoxification enzymes glutathione S-transferase mu 4 (GSTM4), dihydronicotinamide riboside:quinone oxidoreductases (NQO-2), sulfotransferase 1β1 (SULT1β1), and uridine diphosphate glucuronosyltransferase 2 family, polypeptide A3(UGT2A3) were verified by real-time fluorescent quantitative PCR. Plasma malondialdehyde content, total antioxidant capacity (T-AOC), plasma and liver glutathione content were determined using commercial kits. The expression of nuclear factor E2-related factor 2 (Nrf2), GSTM4, and UGT1A6 was examined by Western blotting. The independent sample t-test was used for comparison between the groups. Results: The body weight of mice in the MCD group showed a gradual downward trend, while the body weight of mice in the NCD group did not change significantly following four weeks of different dietary feeding. The MCD group mice liver had yellow-white appearance with round edges. The liver/body mass index was significantly lower in the NCD group (t=3.216, P<0.01). Hematoxylin-eosin staining showed that hepatocytes in the MCD group had an occurrence of fatty degeneration accompanied by inflammatory cell infiltration, with a higher NAFLD activity score (NAS) compared to the NCD group (t=7.155, P<0.001). Sirius red staining showed that the the liver of the MCD group had mildly increased periportal fibers. Plasma biochemical tests indicated that plasma ALT, AST, and triglyceride levels were significantly higher in the MCD group than those in the NCD group (t=8.920, P<0.001; t=6.696, P<0.001; t=3.904, P<0.01). Oil red O staining showed that a large number of lipid droplets accumulated in the liver tissue of the MCD group and were more severe than those in the NCD group (t=7.405, P<0.001). The triglyceride content was significantly higher in the liver of the mice in the MCD group than that in the NCD group (t=3.559, P<0.01), and the expression of inflammatory factors IL-1β and MCP-1 was significantly increased (t=2.562 and 2.391, respectively, P<0.05). Transcriptome sequencing analysis showed that the expression profile of genes related to lipid metabolism was changed in the liver tissue of the mice in the MCD group. The expression of multiple phase Ⅱ detoxification enzymes was significantly downregulated. Real-time fluorescence quantitative PCR verification demonstrated that the expression of four phase Ⅱ detoxification enzymes GSTM4, NQO2, SUIL1β1, and UGT2A3 were significantly lower in the liver of the mice in the MCD group than those in the NCD group (t=2.498, 3.570, 3.768, and 4.166, respectively, P<0.05). The detection kit showed that compared with the NCD group, the malondialdehyde content in the liver of mice in the MCD group increased (t=3.601, P<0.01), while the plasma total glutathione (t=11.93, P<0.001) and reduced glutathione levels were significantly reduced (t=3.635, P<0.01). The total antioxidant capacity of the liver decreased (t=2.872, P<0.05), and the total glutathione and reduced glutathione levels in the liver were significantly increased (t=3.175 and 3.064, P<0.05). Western blotting showed that the expression of Nrf2, GSTM4, and UGT1A6 proteins was significantly lower in the MCD group than that in the NCD group (t=3.385, 2.990, 2.168, P<0.05). Conclusions: The expressions of multiple phase Ⅱ detoxification enzymes and antioxidant capacity are reduced in the liver of MASH mice induced by the MCD diet, and its mechanism is related to the down-regulation of the expression of the upstream regulatory factor Nrf2 protein.