糖尿病肝脏病变中GLUTs和SIRTs表达水平的研究

Expression levels of GLUTs and SIRTs in diabetic liver lesions

目的:研究糖尿病(diabetes mellitus,DM)大鼠肝脏组织及高糖培养下的人肝细胞系LO2中葡萄糖转运体(glucose transporters,GLUTs)和沉默信息调节因子(silent information regulators,SIRTs/sirtuins)的表达情况。方法:(1)选取雄性SD大鼠20只,随机分为正常对照(normal control,NC)组和DM组。DM组大鼠禁食12 h后给予一次性腹腔注射链脲佐菌素(streptozotocin,STZ;60 mg/kg)建立DM模型;NC组大鼠一次性腹腔注射等体积的柠檬酸缓冲液。每2周用血糖测试仪检测大鼠空腹血糖(fasting blood glucose,FBG)和体质量。饲养12周后,1%戊巴比妥钠麻醉大鼠,取材,检测相关血液生化指标;计算肝脏指数;苏木精-伊红(hematoxylin-eosin,HE)染色和过碘酸-席夫(periodic acid-Schiff,PAS)染色观察肝组织病理形态学变化;油红O染色检测肝组织脂质积聚情况;Western blot检测大鼠肝脏组织中GLUTs和SIRTs蛋白表达水平。(2)将LO2细胞在不同葡萄糖浓度中培养48 h后,用光镜观察LO2细胞形态;CCK-8法检测各组细胞活力;Western blot检测高浓度葡萄糖下细胞中GLUTs和SIRTs蛋白表达情况。结果:(1)与NC组相比,DM组大鼠精神萎靡,体质量明显下降,FBG显著升高,肝脏指数显著增加;HE染色显示,DM大鼠肝组织近中央静脉和血窦扩张充血,肝细胞轻度水肿,少量炎症细胞散在浸润;油红O染色显示,DM大鼠肝细胞内弥漫分散红色脂肪小滴;PAS染色显示,DM组大鼠中央静脉区肝细胞内有多量浅紫色圆形小滴弥漫分布于细胞浆内;Western blot结果显示,DM组GLUTs蛋白表达高于NC组,SIRTs蛋白表达低于NC组(P<0.01)。(2)在细胞水平,CCK-8实验结果显示,随着葡萄糖浓度的增加,LO2细胞的活力先增强后减弱:与25 mmol/L葡萄糖组比较,50 mmol/L葡萄糖组细胞活力增强(P<0.01),75、100和125 mmol/L葡萄糖组细胞活力无显著差异(均P>0.05),150、175和200 mmol/L葡萄糖组细胞活力显著减弱(均P<0.01),故后续以150 mmol/L为高糖干预条件。Western blot结果显示,在高糖干预下,细胞中GLUTs和SIRTs表达与动物实验结果一致。结论:高浓度葡萄糖能够造成SD大鼠肝脏损伤,减弱人肝细胞系LO2的活力,而且能够使大鼠肝脏组织和LO2细胞中GLUTs表达升高,SIRTs表达降低。因此,GLUTs和SIRTs家族成员有可能是糖尿病肝损伤的靶蛋白。

AIM:To study the expression of glucose transporters(GLUTs)and silent information regulators(SIRTs/sirtuins)in the liver of diabetic rats and human hepatocytes(LO2 cells)treated with high glucose.METHODS:(1)Twenty male SD rats were randomly divided into normal control(NC)group and diabetes mellitus(DM)group.The rats in DM group were given single intraperitoneal injection of streptozotocin(STZ,60 mg/kg)to establish the DM model,while the rats in NC group were intraperitoneally injected with equal volume of solvent once.Fasting blood glucose(FBG)and body mass were measured every 2 weeks.After 12 weeks of rearing,the blood and liver tissues of the rats were obtained after anesthesia with 1%sodium pentobarbitone,the biochemical indicators of blood were detected,and the liver index was calculated.Hematoxylin-eosin(HE)staining and periodic acid-Schiff(PAS)staining were used to observe liver histopathological changes.Lipid accumulation in liver tissues was detected by oil red O staining.The expression levels of GLUTs and SIRTs family member proteins were detected in rat liver tissues.(2)The LO2 cells were treated with different concentrations of glucose for 48 h.The viability of the cells in each group was measured by CCK-8 assay,and Western blot was used to detected the protein expression levels of GLUTs and SIRTs in the cells.RESULTS:(1)Compared with NC group,the rats in DM group were depressed,lost weight,and the FBG and liver index were significantly increased(P<0.05).The results of HE staining showed that the hepatic sinuses were dilatated and congested near the central vein in DM rats,and mild edema and scattered infiltration of inflammatory cells were found in liver cells.The results of oil red O staining showed the red fat droplets were diffusely scattered within liver cells in DM group.The results of PAS staining showed that there were numerous diffuse light purple circular droplets in the cytoplasm of the liver cells in the central ve-nous area of the DM rats.Western blot showed that the protein levels of GLUTs were higher and the protein levels of SIRTs were lower than those in NC group(P<0.01).(2)The results of CCK-8 assay showed that the viability of LO2 cells was increased in 50 mmol/L glucose group(P<0.01),without significant difference in 75,100 and 125 mmol/L glucose groups(all P>0.05),and decreased in 150,175 and 200 mmol/L glucose groups(all P<0.01).Later,150 mmol/L glu-cose was used as the high-glucose intervention condition.Western blot showed that the protein levels of GLUTs and SIRTs in LO2 cells under high glucose intervention were consistented with the results in animal experiments.CONCLUSION:High concentration of glucose can cause liver damage in SD rats and reduce the viability of human hepatocytes(LO2 cells).It can also increase the expression of GLUTs and decrease the expression of SIRTs in rat liver tissues and LO2 cells.Therefore,GLUTs and SIRTs family members may be the target proteins of diabetes-induced liver injury.