| 【Background&Objective】Hepatitis B virus(HBV)infection is a serious public health problem,with approximately 93 million individuals chronically infected in our country,accounting for about 1/3 of patients with chronic hepatitis B worldwide.Alcoholic liver disease(ALD)is a chronic liver disease induced by long-term heavy drinking,including alcoholic fatty liver disease,alcoholic steatohepatitis(AH)and AH-associated liver fibrosis,cirrhosis,and hepatocellular carcinoma.In recent years,with the change of dietary habit and development of our society,the production and consumption of alcoholic beverages have grown rapidly in China.The morbidity of ALD is increasing by years.The concern is that a great portion of chronic hepatitis B(CHB)patients are suffering concomitant alcoholic liver disease.However,it lacks large scale epidemiological investigation of these comorbidities currently,and the study on the disease is limited.Liver is a key metabolic organ,participating in the metabolism pathways of glucose,fat,and protein.Cholesterol homeostasis plays an important role in maintaining normal physiological functions.Cholesterol metabolizes mainly in the liver as well.Dysregulation of cholesterol results in many diseases.Whereas the effect of ALD combined with HBVinfection on cholesterol metabolism remains unknown.In our study,we construct a novel mouse model of ALD combined with HBV persistence to explore the influence on cholesterol metabolism and the potential mechanism.【Methods】Six-week-old male FVB/Ncrl mice were hydrodynamically injected with a pGEM-4Z-1.3HBV or control vector and then fed with an ethanol or control diet for 6weeks.The changes of body weight,hepatitis B e antigen(HBeAg),liver histology,serum alanine aminotransferase(ALT),aspartate aminotransferase(AST),triglycerides,cholesterol and liver cholesterol levels were observed.Then cholesterol metabolism-related molecules such as sterol regulatory element-binding protein 1(SREBP-1),sterol regulatory element-binding protein 2(SREBP-2),3-hydroxy-3-methylglutaryl coenzyme A reductase(HMGCR),low density lipoprotein receptor(LDLR),proprotein convertase subtilisin/kexin type 9(PCSK9),cholesterol 7 alpha-hydroxylase(CYP-7α),sterol27-hydroxylase(CYP-27A1)and other metabolism pathways involved in export transportation and de-esterification were measured.Hepatitis B X(HBx),Hepatitis B surface(HBs)or Hepatitis B core(HBc)protein expression plasmid was constructed and transfected in HepG2 cells with ethanol stimulation.The expression of above molecules was analyzed.【Results】Characteristic hepatic HBV persistence and alcoholic fatty liver were present in this model.The liver cholesterol level was increased significantly in the chronic alcoholconsumption combined with HBV group compared with the other groups.SREBP-2 and HMGCR,important for cholesterol biosynthesis,were up-regulated in the combined treatment group while CYP-7α,a key enzyme in cholesterol degradation,was significantly decreased.LDLR,responsible for clearing circulating LDL,was down-regulated via the increase of PCSK9.Overexpression of HBc protein with ethanol stimulation in HepG2 cells resulted in the significant enhancement in HMGCR and SREBP-2 levels and obvious inhibition of LDL intaking and CYP-7α expression.【Conclusions】Chronic alcohol consumption combined with HBV led to an accumulation of cholesterol in the liver.This accumulation involved the up-regulation of cholesterol biosynthesis via SREBP-2/HMGCR and the down-regulation of cholesterol degradation through CYP-7α.In addition,the enhanced expression of PCSK9 induced decrease of LDLR,which resulted in the disorder of LDL clearance in the plasma.Besides,HBc protein may be involved in the alteration of cholesterol metabolism. |
