The Expression Of Serum IGF-1 And Hepatic IGF-1R In Pathological Process Of Liver Cirrhosis

Background: Liver cirrhosis is a common digestive system disease, which is usually secondary to various kinds of chronic liver diseases. It is histologically characterized by the development of fibrous bands and the conversion of normal liver architecture into structurally well-defined regenerative nodules in response to liver injury. Cirrhosis is a leading cause of morbidity and mortality worldwide accounting for one million deaths per year. The most common causes of liver cirrhosis in developed countries are infection with hepatitis C virus(HCV), alcoholism and non-alcoholic fatty liver disease(NAFLD). Infection with hepatitis B virus(HBV) represents the most common etiology of the disease in sub-Saharan Africa and most parts of Asia. Plenty of evidence suggests that liver cirrhosis is an independent risk factor for liver cancer, which could increase the risk of hepatocellular carcinoma(HCC). However the carcinogenesis mechanisms involved in the pathological physiological changes of liver cirrhosis are still not very clear.Insulin-like growth factor(IGF) signaling has been regarded as an important autocrine, paracrine and endocrine factor to maintain the function of various tissues and organs. IGF-1 was mainly synthesized by liver(about 90%) under normal conditions, even though this protein can be produced by other cells of the human body. Many studies have shown that IGF 1 can promote the progress of various kinds of cancers, including hepatocellular carcinoma. Insulin-like growth factor receptor I(IGF-1R), which is the most important receptor of IGF-1, has been found upregulated in many kinds of cancer tissues and play important roles in the invasiveness, metastasis, sensitivity to the radiation and chemotherapy of the tumor and the prognosis of patients. However, the role of IGF-1/IGF-1R in the pathological physiological process of liver cirrhosis is not clear. Previous research had reported that serum IGF-1 was decreased in cirrhosis patients, which seemed contradict to their positive roles in carcinogenesis. In our study, we aimed to investigate the circulating levels of serum IGF-1 and the intrahepatic IGF-1R expression during the progression of chronic liver disease. Overall, we investigated the molecular mechanisms behind the progression of chronic liver disease into HCC.1. Serum IGF-1 levels in liver cirrhosisCarbon tetrachloride(CCl4) induced liver cirrhosis mice model was established in 12 weeks. Serum samples of the mice and clinical patients were calculated. Serum ALT and AST were tested by kit; H&E(Hematoxylin and eosin) and Masson stains were conducted to inspect if the model was established successfully. Serum IGF-1 of the mice and patients was tested by ELISA(Enzyme linked Immunosorbent Assay). Hepatosomatic index of the mice were calculated and compared between different groups. The H&E staining manifested focal necrosis, cell degeneration and inflammatory cell infiltration, which was a result of acute inflammation from 1 to 8 weeks of CCl4 administration. Liver cirrhosis, accompanied by signs of inflammation, was observed at week 12, after a 12w-treatment by CCl4, the progression of fibrosis was evident together with karyopyknosis. Livers of all model and control groups were also stained with Masson’s trichrome. Serum AST and ALT of the mice in model group were increased in the whole modeling period. Serum IGF-1 levels dramatically decreased from the 12 weeks according to the ELISA result of the mice, and serum IGF-1 showed a significant decrease in patients with liver cirrhosis. Hepatosomatic indexes of the mice in 12 week were dramatically decreased, which indicated that the parenchymal of the liver were atrophied. We speculated that the damaged liver function which was secondary to the parenchymal atrophy of the liver was the main reason for the decrease of serum IGF-1 in liver cirrhosis.2. Expression of hepatic IGF-1R in mice and patients with liver cirrhosisLiver samples of the mice and cirrhosis patients were calculated. The immunohistochemistry staining for IGF-1R expression in mice livers showed IGF-1R was upregulated in 12 week of the model group. The immunohistochemistry staining for IGF-1R expression in livers of clinical patients showed IGF-1R was upregulated in liver cirrhosis patients. Western-blot analysis was utilised to further investigate the regulatory mechanism behind the increase of hepatic IGF-1R in murine liver fibrosis. Phosphorylation of AKT and IRS1 was down-regulated at week 12 after CCl4 treatment, which indicated the activation of IGF-1R/IRS1/AKT pathway was attenuated. Moreover, the protein levels of p-GSK-3β and p-Fox O3 a were also down-regulated at the 12 weeks, namely, GSK-3β and FOXO3 a were activated. What is more, the levels of Fox O3 a at week 12 were increased in CCl4-treated mice. FOXO3 a can combine with the promotor of IGF-1R gene and regulate the gene expression.Conclusion: Serum IGF-1 was decreased in liver cirrhosis condition. The involved mechanism lies in the fact that the cirrhosis pathological changes cause the atrophy of the liver parenchyma, which dramatically damaged the synthesizing function of the liver. As a result of the decrease of serum IGF-1, the activation of IGF-1R/IRS-1/AKT pathway was attenuated and the inhibition of AKT to GSK-3β and FOXO3 a was relieved. GSK-3β can promote the expression of FOXO3 a, and FOXO3 a can promote the expression of IGF-1R by combining with the promotor of IGF-1R gene.