The Expression And Significance Of Tumor Necrosis Factor α In Liver Of Patients With Nonalcoholic Steatohepatitis

Objective: Nonalcoholic steatohepatitis (NASH) is an inherited-metabolic clinicopathological syndrome with histopathologic characters of hepatocyte steatosis, lobular and portal area inflammation and even focal necrosis. It is estimated that the hepatic fibrosis of different degrees is detectable histologically in approximately 30% patients with NASH, so NASH becomes an important cause of cryptogenic cirrhosis, and people become to pay more attention to it. At present, the accurate underlying pathogenesis of NASH is poorly understood. According to the"two attack"theory, one of the most maturest explanatory theories about the mechanisms of NASH, multi factors are responsible for the pathological development of NASH together, for example, insulin resistance (IR), oxidant stress, lipid peroxides, inflammatory cytokines activation , endotoxemia and so on, which are all interrelated and interacted with each other.Insulin resistance (IR) is a pathophysiologic state that the efficacy of intake and utilization glucose decreased in the insulin target tissues: liver, adipose tissue and skeletal muscle, which resulted the balance of glucose metabolism was broken. At present, we think that IR is a chronic non-specific inflammatory persistence state and a core link in the pathogenesis of NASH.Tumor necrosis factor-α(TNF-α) is an important proinflammatory factor and plays an extremely important cytotoxic effect in inflammation and tissue damage. In addition, TNF-αwhich takes part in the genesis of IR is the main cytokine in the development of NASH and liver damage. In this study, We investigate the correlation of the level of serum TNF-αand the expression of TNF-αin the liver with IR, alanine aminotransferase (ALT) and the histological manifestations of liver in patients with NASH, to reveal the effect of TNF-αon the pathogenesis of NASH and to provide theory basis for the prevention and therapy of this kind of diseases.Methods: Forty seven nonalcoholic fatty liver disease (NAFLD) patients who visist to the third affiliated hospital of Hebei medical university and the infectious disease hospital of Shi Jia Zhuang from June 2008 to November 2008 were chosen in our study, consistent with the clinical diagnostic criteria revised by Fatty Liver and Alcoholic Liver Disease Study Group of the Chinese Liver Disease Association in February 2006. All patients were divided into two groups according to serum alanine aminotransferase (ALT) levels or the biopsy pathology: NASH group with 19 patients, and simple steatosis group with 28 patients, and of 18 patients were confirmed by liver biopsy, consisting of NASH group with 10 patients, and simple steatosis group with 8 patients. There were 20 adults in the control group, 12 of them were healthy persons, and 8 of them were persons who received resection of liver hemangiomas.All patients refrained from high fat diet at nighit and fasted for eight to ten hours before hemospasia. Serum ALT, fasting blood glucose (FBG), and fasting insulin (FINS) were measured using an Olympus AU2700 auto-biochemical analyzer and radio-immune assay respectively. Insulin resistance index (HOMA-IR) was calculated according to homeostasis model assessment (HOMA) model, HOMA-IR=(FINS×FBG)/22.5. Enzyme-linked immunosorbent assay (ELISA) was used for quantitative measurement of serum TNF-αconcentration. Haematoxylin-eosin (HE) staining was used for the general pathologic observation of liver, and the percentage of steatotic hepatocytes was calculated. The activity of hepatic inflammation was determined by the histological scoring system designed and validated by Pathology Committee of the NASH Clinical Research Network in USA in 2005. Masson staining was used for the observation of hepatic fibrosis. Immunohistochemical staining (Power VisionTM method) was used to measure the expression of TNF-αin the liver. The expression of TNF-αwas calculated by multifunctional pathological image analyzer (Beijing Aerospace University). The average area density (the percentage of positive area to statistical area) was calculated under 40 power object lens.SPSS 14.0 was used to analyse all data. Result:1. Common datas, biochemical indexes and serum TNF-αlevel: There was no statistical difference in age between NASH group, simple steatosis group and the control group. The level of BMI and HOMA-IR of NASH group and simple steatosis group were higher than that of control group(P <0.05), and there was no statistical difference between NASH group and simple steatosis group(P >0.05). The levels of serum ALT and TNF-αof NASH group were higher than that of simple steatosis group and control group(p<0.01), and there was no statistical difference between simple steatosis group and control group(P >0.05).2. Pathologic changes in liver: The hepatocytes of patients in simple steatosis group presented modest to big bubble steatosis. There was different degree of inflammation and fibrosis in the liver of patients in NASH group.3. The expression of TNF-αin liver: In NASH group TNF-αexpressed mainly in lobule with inflammation and necrosis in liver, also expressed in presinusoidal cell and portal areas. The positive cells were brownish yellow. The quantity of TNF-αexpressed in liver was remarkably higher in NASH group compared with that of simple steatosis group and control group(P<0.01), and there was no statistical difference between simple steatosis group and control group.4. Correlation analysis: In all patients, the serum TNF-αconcentration correlated positively with the level of BMI, HOMA-IR and ALT (r=0.473, 0.986, 0.474, P<0.01). The quantity of TNF-αexpressed in liver of 10 patients who received liver biopsy with NASH correlated positively with the serum levels of TNF-α, ALT and the degree of hepatic inflammation (r =0.980, 0.878, 0.932, P <0.01).Conclusion:1 IR, obesity and TNF-αplayed important roles in the development of NASH.2 The serum TNF-αconcentration of NASH group was higher than that of simple steatosis group and control group. The serum TNF-αconcentration of all persons correlated positively with the serum levels of BMI, HOMA-IR and ALT.3 In NASH group TNF-αexpressed mainly in lobule with inflammation and necrosis in liver. The quantity of TNF-αexpressed in liver of patients with NASH was remarkably higher compared with that in simple steatosis group and control group. The expression of TNF-αin the liver correlated positively with the degree of hepatic inflammation. TNF-αmight be the key inflammatory factor in the pathogenesis of NASH, and play important roles in the development of NASH.