| Objective: Nonalcoholic fat liver disease is a chronic liver diseasecharacterized by hepatocellular steatosis, the etiology of which need toexcluded by any of follows such as virus infection, overdrink of ethanol,chemicals or poisonings intake, radiation and autoimmune diseases. Itspathological process can be divided into simple fatty liver, nonalcoholicsteatohepatitis and NASH-related cirrhosis. NAFLD is related to somefactogenetic, environmental and metabolic. The America EndocrinePhysicians Association has defined it as one component of metabolicsyndrome. Recently, with the changes of lifestyle and dietary structure, themorbidity of NAFLD is rising gradually, which has become one of the mainchronic liver diseases which are harming human health seriously. Thepathogenesis of NAFLD exists "two strikes" theory: the first strike involvesinsulin resistance because of the development of self defense mechanism. Atthis stage, the passway of anti-apoptosis could be activated and theexpressions of anti-inflammatory factors, such as adiponectin andinterleukin-6, are increased. At this period, the lesions at the liver arereversible. The second strike is mainly of lipid peroxidation caused by theincrease of active oxygen metabolism. ROS is bond to the side chain ofpolyunsaturated fatty acids such as biological membrane phosphatide,resulting in change of biological membrane liquidity, increase of permeabilityand damage of the function of nucleic acid and enzyme, making hepatocyteswhich are undergoing fat degeneration develop to apoptosis or necrosis.As a key processes of NAFLD, insulin resistance has become the curetarget of many drugs.White adipose tissue is the important endocrine organs,there exists the causality relation between the rise of adipokines level such asIL-8and NGF, and metabolic disorders and insulin resistance which lead to liver lipid accumulation. PPAR γ is a kind of ligand activated nuclear hormonereceptor, which has high expression in white adipose tissue and has a role ofadjusting the fatty acid metabolism and induction of the adipocytes differen-tiation. The expression of PPARγ increases gradually in the evolutionprocess of adipose cells from former type to mature ones, impactingadipocytes on the growth and the founction state, further influencing theendocrine function of white adipose tissue. So inhibiting its expressionmoderately can alleviate insulin resistance. Uncoupling protein2(UCP2),belonging to the decoupling protein family, can mediate protons transition,promote the energy release in the form of heat and reduce cell oxidative stress,has great significance in the progress of heat and energy metabolism.Telmisartan is a traditional angiotensin Ⅱ receptor blocker, which cannot only suppress AT1receptors, but also has the function as a partial agonistof PPARγ. So it could improves insulin resistance. Studies have confirmed th-at telmisartan can promote the expression of PPARγ in the liver tissue.Never-theless, but in the white adipose tissue whether it have the similar effects hasyet not a research report. This experiment is designed to establish the model ofnonalcoholic steatohepatitis(NASH)and explore the effects of telmisartan onthe level of body weight,serum transaminase, lipid, glucose, insulin resistance,histology and PPARγ,UCP2receptor expression, for future treatment of thedisease and provide new methods and ideas.Methods:1Animal model: Select male Sprague Dawley rats and normal controlgroup were fed with common diet, model group were fed with84%normaldiet+high fat diet, the formula is:1%cholesterol,5%egg yolk powder,10%lard, free eating and drinking.2Designs experiment:40male SD rats were randomly divided into:1.NC group (n=15) normal chow-fed controls,2. FC group (n=15) high fat-fedcontrol group,3. FT group (n=10) high fat-fed with telmisartan group; At theend of12th week,5rats which were randomly selectde from NC group andthe5rats of FC group were put into glucose clamp test,with liver tissue HE staining and to determine if model success. Then FT group were giventelmisartan (5mg.kg-1.d-1) by intragastric administration and continue high-fatdiet. NC group and FC group were given the same Sodium Chloride byintragastric administration intervention, once daily for four weeks.3The changes of body weight, liver wet weight and liver index: Bodyweight and liver wet weight were weighted from electronic balance,calculating liver index: liver wet weight/body weight ratio.4Determination of insulin sensitivity: Insulin sensitivity was measuredwith glucose infusion rate (GIR) by the euglycermic hyper insulinemia clamptechnique.5Liver histological examination: The paraffin sections, HE staining, lightmicroscopy of liver pathology.6The expression of PPARγ, AT1Rand UCP2mRNA: liver and omentaltissue's PPAR γ, liver's AT1and UCP2mRNA expression levels weredetected by Semi-quantitative reverse transcriptase polymerase chain reaction(RT-PCR) to investigate the impact of expression level, including telmisartanon PPAR γ mRNA and AT1R,UCP2mRNA.The ATP content in liver tissuewere detected By colorimetric method.7Blood serum biochemistry inspection: Serum samples from usingautomatic biochemical analyzer detection of serum lipids andaminotransferase, and other biochemical markers of change, from the Hospitalof Hebei Medical University, the second assist of biochemical room.Results:1The condition of the body weight, liver weight and liver index ofrats in each group: The NASH rat model was successfully established withhigh fat diet for sixteen weeks.The mean body weight, liverweight, and liverindex of model group(597.51±15.62,21.93±1.65and3.67±0.23%,respectively) were increased significantly compared with normalgroup(523.37±18.43%,12.39±0.96and2.37±0.17%, respectively)(p＜0.01).Compared with model group, the treatment group (559.65±15.80,16.10±1.13and2.88±0.17%, respectively) were decreased markedly(p＜ 0.01,0.01and0.01, respectively).2The changes in insulin sensitivity: The difference between the groupssignificantly, February2comparison showed NC group was significantlyhigher than the other two groups, and the FT group were higher than FCgroup.3Histological analysis: Steatosis and inflammation were not seen incontrolled group, while severe lipid degeneration were found in modelgroup(p＜0.01),especially around central vein. Lobular inflammation,periportal inflammation and degeneration, focal necrosis were found in themodel group. There has significant difference between normal group andmodel group (p＜0.01). Steatosis showed improved in the treatment group,compared with model group(p＜0.05).Inflammation showed significantimproved in the treatment group, compared with model group(p＜0.05).4Serum biochemical index：(1) Serum ALT and AST level(U/L) of modelgroup(97.57±9.02and221.00±26.52, respectively) were increasedsignificantly compared with normal group(43.14±8.38and121.86±10.35)(p＜0.01). Compared with model group, ALT and AST level of the treatmentgroup(71.00±10.41and153.29±16.46, respectively)were decreased markedly(p＜0.01).(2) Serum TC and TG level (mmol/L) of model group (1.41±0.17, and0.73±0.17, respectively) were increased significantly comparedwith normal group(0.78±0.16, and0.27±0.08, respectively)(p＜0.01,0.01,respectively).The value of the treatment group drop to (1.22±0.24, and0.60±0.13, respectively), compared with that of model group have nostatistical difference(p＞0.05); Serum HDL-C level (mmol/L) of modelgroup(0.73±0.07) were significantly decreased compared with normalgroup(0.92±0.05)(p＜0.01). Compared with model group, the treatmentgroup(0.79±0.04) were increased, but have no significant difference(p＞0.05);(3)serum glucose:fasting blood glucose(mmol/L)level of modelgroup(11.88±2.13) were increased markedly compared with normalgroup(5.53±1.13)(P＜0.01), Compared with model group,the treatmentgroup(9.22±1.40) were significantly decreased, have statistical difference(p＜ 0.05).5The expression of PPARγ, UCP2and AT1RmRNA:The expression of liver PPARγ in model group(0.167±0.015, respectively)were decreased significantly compared with that of normal group(0.389±0.014,respectively)(p＜0.01).Compared with model group, the treatmentgroup(0.308±0.018, respectively)were increased remarkably(p＜0.01); Theexpression of omental PPAR γ in model group(0.476±0.012, respectively)were increased significantly compared with that of normalgroup(0.185±0.026,respectively)(p＜0.01). Compared with model group, thetreatment group(0.291±0.010, respectively)were decreased remarkably(p＜0.01); The expression of liver UCP2in model group(0.321±0.022,respectively) were increased significantly compared with that of normalgroup(0.198±0.016,respectively)(p＜0.01).Compared with model group, thetreatment group(0.342±0.016)were decreased,but the difference is notsignificant;the expression of AT1RmRNA in model group(0.321±0.022)were increased significantly compared with that of normal group(0.198±0.016), Compared with model group, the treatment group(0.342±0.016)were increased, but have no significant difference(p＞0.05).6Content of ATP: The content of liver ATP in model group(3.54±0.81, respectively) were decreased significantly compared with that of normal group(5.50±0.59, respectively)(p＜0.01). Compared with model group, the treat-ment group (3.39±0.53) were decreased, but the difference is not significant.Conclusion:The rats model of NASH has been successfully established by fat-richdiet after16weeks. Telmisartan can improve glucose, lipid metabolism andinsulin resistance while attenuating weight gain, alleviate steatosis,inflammation and necrosis, decrease blood TC, TG, so telmisartan play aneffective role in the treatment of NASH and IR. Its molecular mechanism of treatment may be related to activing PPARγ receptor, specific binging to theAT1receptors. |
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