| Objective: To establish a NAFLD model in adolescent rats induced by high fat and high cholesterol diet and observe the therapeutic effect of UDCA in the early stage.To definite the characteristics of NAFLD model during this period and determine the dose of UDCA treatment.Methods: 36 SD rats were randomly divided into normal control group(NC group,n = 12)which were given normal diet and high fat and high cholesterol group(n=24)which were given high fat and high cholesterol diet respectively.High fat and high cholesterol group were randomly divided into high fat and high cholesterol model group(HF group,n = 12),dosage of 15 mg/kg/d UDCA group(D1 group,n = 4),dosage of 30 mg/kg/d UDCA group(D2 group,n = 4),large dose of 100 mg/kg/d UDCA group(D3 group,n = 4)after 4 weeks.The NC group continued to give normal diet;HF group,D1 group,D2 group and D3 group continued to give high-fat and high-cholesterol diet.Quantitative UDCA gavage was given to each drug group,while the HF group and NC group were given the same amount of normal saline irrigation,and the total intervention was 4 weeks.4 SD rats in the NC group and HF group were executed in week 4 and 6 respectively,and all SD rats were executed in the eighth week.Collected specimens: Venous blood was collected and analysed liver function and blood lipids.Liver and ileum tissues were collected for pathological analysis.The level of occludin protein expressed in ileum tissues was analysed by the immunohistochemical techniques.Results: 1.Weight of the rats in the HF group was gradually greater than the NC group,and the difference was significant from the third week(P< 0.05).As the dose of UDCA increased,the weight of rats was lighter,but there was no significant difference compared with HF group(P < 0 0.05).The liver weight of HF group was significantly higher than NC group(p< 0.05).With the increase of UDCA dose,the liver weight in rats was lower,and the iver weight in D3 group was significantly lower than HF group(19.44± 0.11 vs 21.88± 0.47,p< 0.05).The liver index both in the NC group and HF group were decreased at first and than increased.The liver index of the HF group was significantly higher than that NC group,and the difference was most obvious in the fourth and eighth weeks(p< 0.05).The higher of the dose of UDCA,the lower of liver index,and the liver index of D3 group was significantly lower than HF group(3.98± 0.08 vs 4.40± 0.14,p< 0.05).2.The AST of the HF group and NC group was decreased at first and then increased.The AST level of the HF group was slightly higher than that of the NC group at week 8(P> 0 0.05).The level of AST was higher as the higher dose of UDCA(P>0.05).The GGT level of SD rats in HF group and NC group decreased gradually(P> 0.05).The higher the UDCA dose,the higher the GGT level.The level of GGT in D2 group was significantly higher than D1 group(0.80± 0.5 vs 0.20± 0.45,P<0.05).The GGT level of the D3 group was significantly higher than the HF group and D1 group(1.00± 0.00 vs 0.25 ± 0.50,P<0.05;1.00± 0.00 vs 0.20± 0.45,P<0.05).The TBA level of HF and NC group was decreased at first and then increased.There was no significant difference between HF group and NC group.The higher the dose of UDCA,the higher the TBA level in rats,but the difference was not significant(P> 0.05).There was no significant change about TG level in the NC group.The TG level of the HF group was decreased at first and then increased.There was no significant difference in TG level around all groups at week 8(P> 0.05).The level of CHO in the NC group and HF group were decreased.The CHO level in the HF group was higher than NC group,and the difference between the 4th week and the 6th week was significant(p<0.05).The CHO level of the rats in each drug group was higher than HF group.The D1 and D3 groups were significantly higher than the HF group(2.34± 0.53 vs 1.69± 0.16,P<0.05;2.29± 0.50 vs 1.69± 0.16,P<0.05).3.The liver pathology change: Lipid deposition,necrosis foci and liver cell edema,part of which was ballooning degeneration,were demonstrated in the liver of HF group.Steatosis in liver were mainly macrovesicular,which consists of some big and medium droplets,and microvesicular steatosis in 4 weeks.But steatosis was aggravated and droplets changed to medium and small shape in 6 weeks.Steatosis was improved and microvesicular steatosis was predominated accompany with macrovesicular steatosis In 8 weeks.The NAS integral performance was significantly higher in week 6 than in week 4,and was slightly lower than week 6(2.25± 0.96 vs.4.25± 0.96 vs.3.75± 1.26,P=0.063).At 8 weeks each drug group compared with HF group,with the increase of UDCA,the greater the liver lipid deposition improved markedly,the lighter liver cell edema,but within the lobule focal point necrosis increase gradually.The NAS integral decreased with the increase of UDCA,and the D3 group was significantly lower than the HF group(2.25± 0.50 vs.3.75± 1.26,p < 0.05).4.Changes in ileum: HE staining: In the HF group,the villi were shortened and widened,part of which were loose and the villi were irregular.Villi in the sixth week was better than the fouth week,and worse than eighth week.With the increase of UDCA dose,the villous edema improved and the arrangement was orderly.D2 and D3 groups are similar,both better than D1 group.Occludin protein immunohistochemical performance: NC group,the HF group and drug group of Occludin protein staining is tan,and continuous distribution in intestinal mucosal epithelial cell membrane and cytoplasm,dyeing score difference was not significant(P > 0.05).However,the HF group was darker than the NC group at fouth week.At sixth and eighth week,the color was lighter than NC group.In the HF group,the staining gradually decreased with time.In week 8,D1 group staining was similar to NC group,and the staining of D2 and D3 groups was lighter than that of NC group,HF and D1 group.Conclusion: 1.Steatosis was improved while hepatocyte injury was aggvarated in Adolescent rats;UDCA could improve the steatosis and cell edema in rats,but as the dose increases hepatocytes were damaged and intestinal mucosal barrier may be injuried.2.The liver function and blood lipids of adolescent rats are changable,and NAFLD can lead to abnormal liver function and dyslipidemia.UDCA can improve liver function,but can not improve blood lipids. |
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