Effect Of Serum Adiponectin And The Expression Of Liver's Adiponectin Receptor-2 In The Pathogenesis Of Non-alcoholic Fatty Liver Disease

Objective:Male Sprague-Dawley rat model of non-alcoholic fatty liver disease (NAFLD) was established by fat-riched diet, serum adiponectin concentration, the expression of adiponectin receptor 2 in the liver and the correlation of them with the histological manifestations of liver were assayed to delineate the effect of adiponectin on the pathogenesis of NAFLD.Methods:30 male SD rats weighed 150g±10g were randomly divided into two groups of 15 rats for each group after fed normally for a week. Control group fed with standard diet while fat-riched diet group fed with standard diet added by 10% lard and 2% cholesterol. All rats were sacrificed after been fasted more than 10 hours at the end of the 12th week. Serum was isolated for serological tests after rats were paralysede and weighted. Weight of liver and liver index were calculated, color and texture of liver were observed. Liver tissue were sunk into 10% formaldehyde solution and prepared to do pathological observation. The expression of adiponectin receptor 2 mRNA were also detected. Serum fasting blood glucose (FBG), triglyceride (TG) and fasting insulin (FINS) were measured by colorimetric method and chemiluminescence assay respectively. Insulin resistance index (IRI) were caculated according to HOMA model (IRI=(FINS×FBG)/22.5). Enzyme-linked immunosorbent assay (ELISA) was used for quantitative measurement of serum adiponectin. Hematoxylin-eosin staining was for the general pathologic observation; The pathologic histology follow the diagnostic criteria published by Chinese Society of Hepatology, CMA. Reverse transcription polymerase chain reaction (RT-PCR) was used to observe the expression of liver adiponectin receptor 2 mRNA. SPSS13.0 was used to process all data. Quantitative data were expressed as x±s. T-test was for the comparison between two groups. Differences were considered statistically significant at P<0.05. Simple correlation and linear-regression analysis were used for correlation analysis.Result:1 The general manifestation of rats:Compared with control group, the liver index of the rats in model group were remarkably higher than that in control group(P<0.01). At the end of 12th week, the liver of control rats present mahogany and bright,but the model rat present yellowish brown and was cohesive to adjacent tissue and the section of liver was greasy and dim. 2 Serological changes:The serum adionectin of control group were significant lower than that of control rats (p<0.01), triglyceride and insulin resistance index of model rats were higher than that of control rats (p<0.05),while fasting blood glucose was resemble between two groups.3 Pathologic changes:The hepatocytes of the model rats presented modest to severe big bubble steatosis. There were different stages of inflammation and fibrosis in the livers of model rats. The quantitive evaluation of steatosis, inflammation were 2.82+0.21,2.33+0.52 in model rats and 0.00+0.00,0.65+0.28 in control rats respectively. There were aboundent difference between two groups (both P<0.01). 4 The expression of adiponectin receptor 2 mRNA:On the basis of the result of RT-PCR, adiponectin receptor 2 were found aboundent in the liver. The expression of adiponectin receptor 2 of model rats are higher than that of the control rats.5 Correlation analysis: In model rats the serum adiponectin concentration inverse correlated with steatosis, inflammation positively, r=-0.87(p<0.01),r=-0.75(p<0.01).The expression of adiponectin receptor 2 of model rats livers correlated with steatosis, inflammation negatively, r=-0.84(p<0.01),r=-0.86(p<0.01).Stepwise multiple regression analysis showed that the decrease of expression of adiponectin receptor 2 in liver was an independent risk factor for steatosis. The regressive equation was Y=-2.052-6.56X5. (Y: steatosis; X5: the expression of adiponectin receptor 2). The coefficient of determination (designated as R2) was R2=0.704.Conclusion:1 NAFLD model rats can be successfully established by fat-riched diet.2 The serum Adiponectin concentration and Adiponectin receptor 2 mRNA expression of model rat were lower significantly than that of control rat,which were thought to be the key factors in the pathogenesis of non-alcoholic steatohepatitis.3 The lower serum adiponectin concentration and weaker expression of adiponectin receptor 2 were correlated with the lipid metabolism disorder,the disturbance of carbohydrate metabolism and the insulin resistance. 4 The Adiponectin concentration can be a new index which were used to reflected the degree of steatosis and inflammation at liver.