Sirtuin 6 Ameliorates Alcohol-induced Liver Injury By Reducing Oxidative Stress And Endoplasmic Reticulum Stress In Mice

BackgroundIt is estimated that alcohol-induced cirrhosis accounted for 48.9% among the deaths caused by cirrhosis in the world in 2020,and it also accounted for 0.93% of deaths from various diseases.An epidemiological survey in my country shows that the average prevalence of alcoholic liver disease is 4.5% in the Chinese population,and it shows an upward trend year by year.Therefore,alcoholic liver disease has become a rather serious problem affecting national health in our country.Sirtuins is classified to NAD+-dependent histone/non-histone deacetylases that are highly conserved.Sirtuin 6(SIRT6),as one of its family members,participates in the regulation of many important physiological functions such as metabolism,inflammation,and stress resistance.In recent years,studies have shown that SIRT6 plays a critical role in maintaining the metabolic homeostasis of liver cells.However,the role and molecular mechanism of SIRT6 in alcoholic liver disease remain to be studied.ObjectiveThe objective of this study is to clarify the influence of SIRT6 on the formation of alcoholic liver disease and explore its mechanism.Unreported genes that mediate SIRT6’s influence on the alcoholic liver disease were expected to be discovered and verified.MethodsIn this experiment,male mice aged 8-10 weeks were used to establish a mouse model of alcoholic liver disease by alcohol feeding(8 weeks)and one-time overdose(chronic plus binge ethanol feeding).The mouse model was constructed by hepatic cell-specific knockout and overexpression of SIRT6.H&E staining is used to detect the overall morphology of liver tissue and the size of fat vacuoles;analyze the distribution of inflammatory cells and the content of oxidative stress by immunohistochemistry chloroform/methanol extraction method is used to quantitatively analyze liver fat content;detect the indicators of ALT and AST in serum through biochemical analysis to assess the degree of liver damage;the total RNA and protein of the liver were extracted to detect the expression level of related genes;using the in vitro liver primary cell culture technology to study the regulation effect of SIRT6 on endoplasmic reticulum stress through the overexpression and knockdown of SIRT6 mediated by adenovirus.Meanwhile,the difference in gene expression is systematically analyzed in the whole genome to obtain potential new gene targets regulated by SIRT6 in alcoholic liver disease.Results1.Alcohol stimulation reduces the expression of SIRT6 in the liver;2.In the mouse model of alcoholic liver disease,the knockout of SIRT6 in the liver aggravates liver damage and alcoholic fatty liver,increases oxidative stress and inflammatory cell infiltration;3.In the mouse model of alcoholic liver disease,overexpression of SIRT6 in liver cells can resist liver damage and related pathological changes caused by alcohol;4.The expression of metallothionein gene is regulated by SIRT6 in the mouse model of alcoholic liver disease,overexpression of MT1 in the liver can alleviate liver lipid accumulation,liver damage and oxidative stress caused by SIRT6 knockout;SIRT6cooperates with the transcription factor MTF1 to promote the expression of MT1/2;5.SIRT6 in liver cells can regulate the endoplasmic reticulum stress of the liver under stimulation of alcohol;6.The treatment of TUDCA can reduce liver ER stress caused by alcoholic stimulation,and alleviate patholgical changes of liver in mice that SIRT6 was specifically knock out in hepatic cells;7.SIRT6 has a direct regulatory effect on the expression of ER stress-related genes under stimulation of alcohol.ConclusionOur research results clarify that SIRT6 alleviates hepatic steatosis,oxidative damage and inflammatory cell infiltration under alcohol stimulation.In terms of mechanism,SIRT6 can promote the expression of metallothionein to remove the oxidative stress caused by alcohol metabolism,thereby protecting the liver from alcohol-induced damage;In addition,SIRT6 can also reduce alcohol-induced ER Stress in hepatic cells,lipid accumulation and liver inflammation.This study,for the first time,reveals the role of SIRT6 in alcoholic liver disease and provides some theoretical basis for the prevention and treatment of alcoholic liver disease.