| Nonalcoholic fatty liver disease is a kind of chronic liver diseasecharacterized by diffused hepatocyte macrovesicular stertosis withoutexcessive intake of alcohol and other definite liver damage. NAFLD is a groupof clinical and pathological syndrome, including simple hepatic steatosis,nonalcoholic steatohepatitis and NASH-related cirrhosis. With the changes ofhuman lifestyle and diet in recent year, the incidence of NAFLD increasedyear by year. So far, NAFLD has become the most common chronic liverdisease in developed and even developing countries all over the world. Withthe trend of the globalization of obesity and metabolic syndrome as well as theaging population and the effective control of viral hepatitis, NAFLD wouldeventually become one of the most important causes of end stage liver diseasesuch as cirrhosis and hepatic carcinoma.American Association of Clinical Endocrinologists suggested that insulinresistance is the initiating and the central link of NAFLD. In the stage of IR,NAFLD is closely related to the disorder of lipidic metabolism and adiposeaccumulation in hepatocytes. Next comes the lipid peroxidation, and thencomes the inflammation accompanied by cascade reaction of peroxidation.So IR becomes the hot spot to study, prevention and treatment of nonalcoholicfatty liver disease.It is discovered that telmisartan, one of the angiotensin Ⅱreceptorblockers, is not only blocker of the type1receptor of angiotensin Ⅱ, and alsoa partial agonist of PPARγ. It has the capacity to improve glucose, and lipidmetabolism, and retard weight gain by promoting formation of smalladipocytes, whith are metabolically efficient.Therefore, in order to explore the pathogensis of NAFLD and provide potential way for preventing and treating NAFLD patients with telmisatan,NASH rat model with IR was established by high fat diet and then interferedwith telmisartan to investigate its effection of improving IR andsteatohepatitis.Objectives: To establish the model of NASH and explore the effects oftelmisartan on the level of body weight，serum aminotransaminases, lipids andglucose, euglycermic hyperinsulinemia clamp technique, liver histologicpathology, and expressions PPARs, adiponectin2receptor.Methods:1Animal model: male Sprague Dawley rats were fed with common dietfor control and high fat diet for animal model, whith contained1%cholesterol,5%egg yolk powder,10%lard, free eating and drinking.2Experiment designs:40male SD rats were randomly divided into: NCgroup (n=15) normal chow-fed controls. FC group (n=15) high fat-fed controlgroup. FT group (n=10) high fat-fed with telmisartan group. At the end of12thweek,5rats which were randomly selected from each NC and FC were putinto euglycermic hyperinsulinemia clamp technique, and liver tissue HEstaining to determine if NASH SD rat model with IR was successful. Then FTgroup were given telmisartan (5mg.kg-1.d-1) by intragastric administration andcontinue high-fat diet. NC group and FC group were given the same SodiumChloride by intragastric administration intervention, once daily for four weeks.3Body weight, liver wet weight and liver index: Body weight and liverwet weight were weighted from electronic balance, calculating liver index asfollow: LI ration=liver wet weight/body weight.4Determination of insulin sensitivity: Insulin sensitivity was measuredwith glucose infusion rate (GIR) by the euglycermic hyperinsulinemia clamptechnique.5Liver histological examination: The paraffin sections, HE staining, lightmicroscopy of liver pathology.6The expression of PPARs, AT1R and AdipoR2mRNA: the PPARα,PPARγ, AT1R and AdipoR2mRNA expression levels of liver tissue were detected by Semi-quantitative reverse transcriptase polymerase chain reaction.7Serum biochemistry inspection: serum lipids and aminotransferase andother biochemical markers by automatic biochemical analyzer, were detectedin department of biochemistry, the Second Hospital of Hebei MedicalUniversity.Results:1Body weight, liver weight and liver index of rats in each group:The NASH rat model was successfully established with high fat diet forsixteen weeks. The mean body weight, liver weight and liver index of rat inFC group (597.51±15.62,21.93±1.65and3.67±0.23%,respectively) wereincreased significantly compared with rat in NC group (523.37±18.43%,12.39±0.96and2.37±0.17%, respectively)(P＜0.01).Compared with FC group,the three values of rat in FT(559.65±15.80,16.10±1.13and2.88±0.17%,respectively) were decreased significantly(P＜0.01).2Changes in insulin sensitivity: The difference between the groupssignificantly. Pairwise comparisons among the three groups showed NC groupwas significantly higher than the other two groups, and the FT group werehigher than FC group.3Histological analysis:Steatosis and inflammation were not seen in NCgroup,while the FC group was diffuse macrovesicular or microvesicularsteatosis, the bullous based mixed steatosis, the liver cells of fattydegeneration were more than2/3, especially around central vein. Lobularinflammation, periportal inflammation and degeneration, focal necrosis werefound in FC group. There was significant difference between NC and FCgroup (P＜0.01). Steatosis in FT group showed significantly improved,compared with FC group(P＜0.05). Inflammation in FT group also showedsignificantly improved, compared with FC group(p＜0.05).4Serum biochemical parameters：(1) Serum alanine aminotransferase andaspartate aminotransferase level(U/L) of FC group(97.57±9.02and221.00±26.52, respectively) were increased significantly compared with NCgroup(43.14±8.38and121.86±10.35)(P＜0.01). Compared with FC group, ALT and AST level of the FT group(71.00±10.41and153.29±16.46,respectively)were decreased markedly(P＜0.01).(2) Serum TC and TG level(mmol/L) of FC group(1.41±0.17,and0.73±0.17, respectively) wereincreased significantly compared with NC group(0.78±0.16, and0.27±0.08,respectively)(P＜0.01,0.01, respectively). The two values of the FT groupwere observed some extent of decrease(1.22±0.24, and0.60±0.13,respectively), without statistical difference compared with that of FC group(P＞0.05); Serum HDL-C level (mmol/L) of FC group(0.73±0.07) weresignificantly decreased compared with NC group(0.92±0.05)(P＜0.01).Compared with FC group, the FT group(0.79±0.04) were increased, but haveno significant difference(P＞0.05).(3)Serum glucose: fasting blood glucose(mmol/L) levels of FC group (11.88±2.13) were increased markedly comparedwith NC group(5.53±1.13)(P＜0.01), Compared with FC group, the FTgroup(9.22±1.40) were significantly decreased(P＜0.05).5Expressions of PPARα, PPARγ, AdipoR2and AT1RmRNA:The expressions of PPARα, PPARγ and AdipoR2mRNA in FC group ofthe liver tissue(0.207±0.017,0.167±0.015and0.236±0.028, respectively)were decreased significantly compared with that of NC group(0.449±0.025,0.389±0.014and0.431±0.015, respectively)(P＜0.01).Compared with FCgroup, the FT group(0.376±0.014,0.308±0.018and0.340±0.020,respectively)were increased remarkably(P＜0.01), the expression of AT1RmRNA of the liver tissue in FC group（0.321±0.022） were increasedsignificantly compared with that of NC group（0.198±0.016）. Compared withFC group, the expression of AT1R mRNA FT group（0.342±0.016）was of nosignificant difference(P＞0.05).Conclusion: The rats model of NASH has been successfully establishedby fat-rich diet after16weeks. Telmisartan can improve glucose, lipidmetabolism and insulin resistance while attenuating weight gain, alleviatesteatosis, inflammation and necrosis, decrease blood TC, TG, improve IR andliver pathology of NASH rats. Therefore, telmisartan might play an effectiverole in the treatment of NASH. Its molecular mechanism of treatment may be related to activing PPARγand PPARα, binging and blocking the AT1receptor. It is not clear in this study whether telmisartan activates PPARα/γdirectly or through blocking AT1receptor. Further research in this aspect isneeded. |
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