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Objective To observe morphologic,function and oxidative stress index of islet beta cell in rabbits with hypercholesterolemia,for exploring the influence of high-cholesterol to islet beta cell and intervention effect of atorvastatin.Methods Twenty-four New Zealand white rabbits were randomly divided into control group, cholesterol group and atorvastatin group, each group of eight rabbt. control group:ordinary rabbits feed100g/d was given daily; cholesterol group:ordinary particles100g+1%cholesterol was given daily; Atorvastatin group:ordinary particles100g+1%cholesterol+atorvastatin (2.5mg/kg) was given daily; In weeks0and6weekend,blood lipid levels was assayed, according to the animal model of decision criteria, rabbit serum total cholesterol<3mmol/L as normal, total cholesterol>10mmol/L was considered to be hypercholesterolemia. Sixth weekends, the empty stomach blood were collected for inspected fasting plasma glucose (FPG), insulin (FINS), total cholesterol (TC),low density lipoprotein cholesterol (LDL) and triglyceride(TG), meanwhile, to used the steady state model assessment method for calculation of insulin resistance index (HOMA-IR), insulin secretion index (HOMA-β) and insulin sensitive index (ISI);Orol gavage is used to carry on the oral glucose tolerance test (OGTT), each rabbit after fasting for12hours,25%glucose was gavaged by10ml/kg glucose, respectively collected blood samples after Sugar loading0,30,60,and120min, and immediate detection, the area under blood glucose concentration curve (GAUC) is obtained by using the approximate trapezoidal method.The pancreatic tissue was taken to observe islet morphology and insulin immune response positive cells by immunohistochemical method, to detection proinsulin mRNA expression by RT-PCR, to measure oxidative stress index:malondialdehyde (MDA) and reducing glutathione (GSH) by spectrophotometry.Results1. Before feeding Cholesterol each rabbit fasting blood sugar, fasting insulin levels have no statistical difference (p>0.05), After feeding cholesterol for six weeks, high cholesterol group total cholesterol (TC), low density lipoprotein cholesterol (LDL)concentration was significantly increased than the control group (p<0.05). According to the animal model decision criteria, rabbit high cholesterol model has been successfully established.2. Cholesterol group after Sugar loading30and60min the blood glucose, the date of aera-under-curve(AUC) and the insulin resistance index (HOMA-IR) was increased than control group (P<0.05),and insulin sensitive index (ISI), beta cell function index (HBCI/IR)was lower than control group (P<0.05); The immunohistochemical staining results show, compared with control group, a great deal of beta cell hypertrophy and arrangement disorder were observed in the cholesterol group,in addition, insulin positive expression was increased; RT-PCR test found that the proinsulin mRNA was over-active(P<0.05); Spectrophotometry display that malondialdehyde (MDA) absorbance value was higher than that of the control group (P<0.05), and reducing glutathion (GSH) absorbance value was just the opposite (P<0.05).3.Atorvastatin group the immunohistochemical staining results show insulin positive expression increased,no statistics difference in comparison with high cholesterol group; According to the immunohistochemical results malondialdehyde (MDA) absorbance value was lower (P<0.05),and reducing glutathione(GSH) absorbance value just the reverse(P<0.05). Than,fasting gloucose(FBG),after Sugar load120min blood glucose, HOMA-IR, HBCI/IR, ISI and Proinsulin mRNA express had no significant difference than Cholesterol group(p>0.05).Conclusions1. Hypercholesterolemia may lead to islet beta cell insulin secretion impaired and insulin resistance.2.Oxidation-oxidation system imbalance probably was one of the important mechanism of the hypercholesterolemia caused islet beta cell insulin secretion impaired.3. Atorvastatin can significantly reduced pancreatic tissue oxidative stress level, but have not improved the sugar metabolic disorders induced.by high cholesterol.
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