| Nonalcoholic fatty liver disease (NAFLD) is a chronic disease characterized by hepatic steatosis and varying degrees of liver injury, inflammation and fibrosis without reason of alcohol abuse. Nonalcoholic steatohepatiti(sNASH)has been implicated as a major risk factor for cryptogenic cirrhosis. With people's living standards being improved, NAFLD has now been recognized as one of the most common type of chronic liver diseases and might lead to important public health problems. Despite the high prevalence of NAFLD and its potential for serious sequelae, the underlying etiologic factors that determine disease progression of fatty liver to NASH and cirrhosis are poorly understood. In fact, obesity, type 2 diabetes and dyslipidemia frequently coexist with NAFLD. Insulin resistance is an underlying factor in these metabolic disorders and could play a critical role in the pathogenesis of NAFLD.Suppressor of cytokine signaling-3(SOCS-3) is a crucial member of recently discovered SOCS family, which performs functions by suppressing the janus kinase and signal transducer and activation of transcription pathway. It is one of the key regulators of many cytokine signaling, including IL-6. Studies shows that overexpression of suppressor of cytokine signaling (SOCS)-3 in liver leads to insulin resistance and an increase of sterol regulatory element-binding protein (SREBP)-1c, the key regulator of fatty acid synthesis in liver. Thus, reducing expression of SOCS proteins in liver presents a novel approach to treatment/prevention of hepatic steatosis.In this research, we established the NASH rat model and intervened with Telmisartan to evaluate the efficacy in improving IR and steatohepatitis , and measured the levels of ser. IL-6 and tissular expression of SOCS-3, SREBP-1c in rat liver. It has far-reaching significance to further explore the pathogenesis of NASH and suggest a number of interesting opportunities for developing improved therapeutic approaches to the hepatic steatosis and several components of the metabolic syndrome associated with diabetes and obesity.Objective:①To establish nonalcoholic steatohepatitis rat model by high fat diet.②To investigate the role of SOCS-3 in the development of nonalcoholic steatohepatitis.③To explore the effect of Telmisartan on high-fat diet induced NASH in experimental rats and its possible molecular mechanisms.Methods:Totally 35 SD male rats were assigned randomly into 3 groups: control group with 10 rats (groupA) ,giving basic diet; model group with 15 rats (groupB) and Telmisartan treated group (groupC) with 10 rats, giving a high fat diet that consisted of 88% basic diet, 10% lard oil and 2% cholesterol. They were fed in standard condition and free of drinking and eating. After the model was successfully established, rats in groupC are given Telmisartan (5 mg·kg- 1·d-1) from the end of the 12th week by intragastric administration, while rats in nomal and model control were given normal sodium of the same volume as Telmisartan, once daily. Recorded the weight of animals every week and adjusted the dosage according to the weight changes. The work was done continuously until the end of the 16th week and then all rats were killed.①Observed the general state of livers and then completely resected and weighed.②Liver tissue sections were stained with HE and were studied under a light microscope to observe the pathological alteration.③Blood sample were collected for detection of ser. triglyceride(TG), cholesterol(CHO), high-density lipoprotein cholesterol(HDL-C), alanine aminotransferase(ALT), aspartate amino transferase(AST)④Glucometer and chemiluminescence were used respectively to detect the blood glucose and the ser. insulin, and then calculate the HOMA-IR according to formula⑤The level of ser. IL-6 was determined by radioimmunity⑥Semiquantitative RT-PCR was used to determine the mRNA level of SOCS-3 and SREBP-1c in liver tissue.Results:1 The rats fed with high fat diet developed steatohepatitis at the 12th week. We can make a conclusion that 12weeks of high fat diet could induce NASH in male SD rats.2 Weight,Liver exponentWeight of model group was much higher than nomal control (P <0.01). Weight of Telmisartan treated group was higher than nomal control (P <0.05), but much lower than model group (P <0.01).The liver weight of model group and treated group were markedly higher than nomal control (P <0.01). The treated group was much lower than model group (P <0.01).Liver exponent of model group and treated group were much higher than nomal control (P <0.01). The treated group was lower than model group and the differences has notable significance (P <0.05).3 TG,TC,HDL-C,ALT,ASTTG of model group was higher than nomal control (P <0.05). There was no significant difference between model group and treated group (P >0.05). TC and HDL-C of model group and treated group were much higher than nomal control (P <0.01). There was no significant difference between model group and treated group (P >0.05). ALT of model group and treated group were much higher than nomal control (P <0.01) and treated group was much lower than model group (P <0.01). AST of model group was higher than nomal control (P <0.01). There was a decreasing tendency in treated group compared to model group but the difference was not notable (P >0.05).4 FBG,FINS HOMA-IRFBG of model group was much higher than nomal control (P <0.01). Treated with drugs reduced FBG markedly (P <0.01). There were no significant difference between model group and treated group (P >0.05). FINS of model group and treated group were much higher than nomal control (P <0.01). Treated group was much lower than model group (P <0.01).HOMA-IR of model group and treated group were much higher than nomal control (P <0.01). Treated group was much lower than model group (P <0.01).5 the level of ser. IL-6The ser. IL-6 content of model group was much higher than nomal control (P <0.05). There was no significant difference between nomal control and treated group (P >0.05). Compared to model group, there was a decreasing tendency in treated group but the difference was not notable (P >0.05).6 The NASH rat model was established successfully with 12 weeks'high fat diet. Diffuse macrovesicular steatosis mixed with inflammatory cell infiltration appeared in livers of model group. Hepatic steatosis was developed gradually. Severe hepatic steatosis, espacially around central vein, was found at 16th week. Lobular inflammation, periportal inflammation and degeneration, focal necrosis even bridging necrosis were found in model group, perisinusoidal cell fibrosis appeared in a few rat livers. Telmisartan can remarkably relieve the hepatic steatosis, from a certain extent improve the inflammation and fibrosis in NASH rat model hepatic tissue.7 SOCS-3,SREBP-1c mRNA expressionSOCS-3 mRNA expression of model group was much higher than nomal control (P<0.01). SOCS-3 mRNA expression of Telmisartan treated group was higher than nomal control (P <0.01), but lower than the model group (P <0.05). SREBP-1c mRNA expression of model group was much higher than nomal control (P <0.01). SREBP-1c mRNA expression of Telmisartan treated group was higher than nomal control (P <0.01), but lower than the model group (P <0.01).8 correlated analysisSOCS-3 mRNA expression was positively correlated with the level of ser. IL-6, SREBP-1c mRNA expression and HOMA-IR (r= 0.369, 0.698, 0.643; P <0.05,P <0.01,P <0.01).Conclusion:1.High fat diet can successfully establish the NASH rat model.2.SOCS-3, SREBP-1c, IL-6 may play an important role in development of NASH.3.Telmisartan can exerts therapeutical effect through remarkably relieving the hepatic steatosis, improving hepatic function and insulin resistance and degrading SOCS-3, SREBP-1c mRNA expression. |
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