Abstract:Objective To explore the effects and mechanisms of modified Dahuang Huanglian Xiexintang on hepatic oxidative stress injury in type 2 diabetes mellitus （T2DM） rats based on the nuclear factor erythroid 2 related factor 2 （Nrf2）/heme oxygenase-1 （HO-1） axis.Method Six ZDF （fa/+） rats were as assigned to the blank group， and 30 ZDF （fa/fa） rats were used to induce the T2DM model by feeding a high-fat diet. After successful modeling， the rats were randomly divided into the model group， metformin group （0.18 g·kg-1）， and low， medium， and high dose groups of modified Dahuang Huanglian Xiexintang （0.54， 1.08， 2.16 g·kg-1）， with six rats in each group. After 12 weeks of drug intervention， the body mass， liver mass， fasting blood glucose （FBG）， and oral glucose tolerance test （OGTT） levels were measured. Serum total cholesterol （TC）， triglycerides （TG）， high-density lipoprotein cholesterol （HDL）， low-density lipoprotein cholesterol （LDL）， alanine aminotransferase （ALT）， and aspartate aminotransferase （AST） levels were detected using an automatic biochemical analyzer. The pathological changes of liver tissue were observed by hematoxylin-eosin （HE） staining. Enzyme-linked immunosorbent assay （ELISA） was used to detect the activity of superoxide dismutase （SOD）， reactive oxygen species （ROS）， glutathione peroxidase （GSH-Px）， and the level of malondialdehyde （MDA） in liver tissues. Immunohistochemistry was used to detect the expression of Nrf2 in the liver. Real time quantitative polymerase chain reaction （Real-time PCR） and Western blot were used to detect the mRNA and protein expression levels of Nrf2 and HO-1 in liver tissues.Result Compared with the normal group， the model group showed a significant increase in body mass， liver mass， and liver index （P<0.01）. Compared with the model group， the metformin group and the medium and high dose groups of modified Dahuang Huanglian Xiexintang showed a significant decrease in body weight， liver mass， and liver index （P<0.01）. Compared with the normal group， the model group showed significantly increased TC， TG， and LDL levels （P<0.01）， and significantly decreased HDL levels （P<0.01）. Compared with the model group， the metformin group and all doses of modified Dahuang Huanglian Xiexintang showed significantly reduced TC levels （P<0.01）， and significantly reduced TG levels （P<0.05）. The medium and high dose groups of modified Dahuang Huanglian Xiexintang showed significantly reduced LDL levels （P<0.05）. The metformin group and all doses of modified Dahuang Huanglian Xiexintang showed significantly increased HDL levels （P<0.05）. Compared with the normal group， the model group showed significantly increased ALT and AST activities （P<0.01）. Compared with the model group， all doses of modified Dahuang Huanglian Xiexintang and the metformin group showed significantly reduced ALT activities （P<0.05） and significantly reduced AST activities （P<0.01）. Compared with normal group， the model group showed significantly increased FBG at all time points （P<0.01）. Compared with the model group， the metformin group and all doses of modified Dahuang Huanglian Xiexintang showed significantly reduced FBG at 8， 10， 12 weeks. The OGTT results showed that compared with the normal group， the model group had significantly increased blood glucose at all time points （P<0.01）. Compared with the model group， the metformin group showed significantly reduced blood glucose at all time points （P<0.01）， and the medium and high dose groups of modified Dahuang Huanglian Xiexintang showed significantly reduced blood glucose at 90， 120 min （P<0.01）. HE pathology showed clear and regular liver cell structure in the normal group， while the model group showed disordered liver cell structure with visible fat vacuoles and a large number of deformed necrotic cells. The liver tissue structure improved in the metformin group and all doses of modified Dahuang Huanglian Xiexintang， with fewer necrotic cells. Compared with the normal group， the model group showed significantly reduced SOD and GSH-Px levels （P<0.01）， and significantly increased ROS and MDA levels （P<0.01）. Compared with the model group， the metformin group and all doses of modified Dahuang Huanglian Xiexintang showed significantly increased SOD and GSH-Px levels （P<0.01）， and significantly reduced MDA levels （P<0.01）. The medium and high dose groups of modified Dahuang Huanglian Xiexintang showed significantly reduced ROS levels （P<0.05）. Compared with the normal group， the model group showed significantly reduced Nrf2 and HO-1 mRNA expression levels （P<0.01）. Compared with the model group， the metformin group and the medium and high dose groups of modified Dahuang Huanglian Xiexintang showed significantly increased Nrf2 and HO-1 mRNA expression levels （P<0.05）. Immunohistochemistry showed that compared with the normal group， the model group had significantly reduced positive expression of Nrf2 and HO-1 （P<0.05）. Compared with the model group， the metformin group and all doses of modified Dahuang Huanglian Xiexintang showed increased positive expression of Nrf2 and HO-1， with a significant increase in brown-yellow granules around the cell nucleus （P<0.05）. Western blot results showed that compared with the normal group， the model group had significantly reduced protein expression of Nrf2 and HO-1 （P<0.01）. Compared with the model group， the metformin group and all doses of modified Dahuang Huanglian Xiexintang showed significantly increased protein expression of Nrf2 and HO-1 （P<0.01）.Conclusion Modified Dahuang Huanglian Xiexintang can significantly improve the general condition and pathological changes of liver tissues in T2DM model rats. This improvement is likely achieved through ameliorating hepatic oxidative stress injury via regulating the Nrf2/HO-1 axis.
