自发2型糖尿病模型OLETF大鼠肾周脂肪组织水通道蛋白7的表达

Expression of aquaporin 7 in perirenal adipose tissue of Otsuka Long-Evans Tokushima Fatty diabetic rats

目的:观察自发2型糖尿病动物模型OLETF(Otsuka Long-Evans Tokushima Fatty)大鼠不同糖尿病病程阶段肾周脂肪组织水通道蛋白7 mRNA和蛋白表达的变化,探讨其在肥胖和糖尿病发生中的作用。方法:以OLETF大鼠30只为实验组,同种系非糖尿病LETO(Long-Evans Tokushima Otsuka)大鼠18只为正常对照。8周(基线)时两组大鼠各处死6只。随后OLETF大鼠分为未治疗组(OLETF组)12只及盐酸二甲双胍治疗组(OLETF/M组)12只。观察各组大鼠8、18、28周时的体重、血清甘油三酯、胆固醇、丙三醇、葡萄糖耐量试验的血糖与胰岛素水平以及肾周脂肪组织水通道蛋白7(aquaporin7,AQP7)mRNA和AQP7蛋白含量的变化。用Real-time PCR测定AQP7mRNA水平,Western blotting测定AQP7蛋白含量。结果:(1)OLETF组18周均发展为糖尿病[60分钟血糖(25.67±6.78)mmol/L,120分钟血糖(16.19±2.98)mmol/L]。OLETF组大鼠随周龄增加,其体重、血糖、胰岛素、血清甘油三酯均明显增加。血清丙三醇水平先增高后下降,8、18和28周的水平分别为(52.61±11.80)、(156.03±39.56)和(130.84±25.46)μmol/L。(2)OLETF/M组18周时达糖尿病标准[60分钟血糖(18.64±6.67)mmol/L,120分钟血糖(14.13±5.21)mmol/L],但血糖水平低于OLETF组;28周时血糖下降均恢复为糖耐量异常[60分钟血糖(11.72±3.06)mmol/L,120分钟血糖(12.42±2.30)mmol/L]。OLETF/M组的甘油三酯、胆固醇和丙三醇浓度较OLETF组降低。OLETF/M组与OLEFT组比较具体值为:甘油三酯18周(0.88±0.14)vs.(1.09±0.44)mmol/L,28周(1.06±0.51)vs.(2.20±1.51)mmol/L;胆固醇18周(2.18±0.14)vs.(2.30±0.21)mmol/L,28周(1.90±0.19)vs.(2.36±0.35)mmol/L,P<0.05;丙三醇18周(77.28±9.06)vs.(156.03±39.56)μmol/L,P<0.05,28周(58.44±14.03)vs.(130.84±25.46)μmol/L,P<0.01。(3)增加肾周脂肪组织AQP7 mRNA及蛋白表达:随周龄及肥胖增加,18及28周OLETF组AQP7 mRNA表达较同组8周龄大鼠分别上调了67.5%和41.7%,AQP7蛋白表达较同组8周龄大鼠分别上调了21.9%和8.9%;18及28周OLETF/M组AQP7 mRNA表达较同组8周龄大鼠分别上调了25%及8.3%,AQP7蛋白表达较同组8周龄大鼠分别上调了14.6%及1.6%。OLETF及OLETF/M组均呈先增高而后下降的趋势,于18周时增高,28周下降,与血清丙三醇变化趋势一致。OLETF/M组AQP7 mRNA及蛋白表达水平低于同周龄OLETF组,但两组差异无统计学意义。OLETF/M组的体重、胰岛素与OLETF组差异无统计学意义。OLETF/M组AQP7 mRNA及蛋白表达水平低于同周龄OLETF组,但两组差异无统计学意义。结论:内脏脂肪AQP7参与了糖脂代谢,与2型糖尿病和肥胖发病相关。二甲双胍可改善OLETF大鼠的脂代谢和糖代谢紊乱,但对AQP7 mRNA及蛋白表达未见明显影响。

Objective：To observe perirenal adipose tissue aquaporin 7（AQP7） mRNA and protein expression in the spontaneous type 2 diabetes animal model Otsuka Long-Evans Toku-shima Fatty（OLETF） rats in different stages of diabetes and explore the role of AQP7 in obesity development and diabetes.Methods： OLETF rats（n=30） were studied,with the same strains of non-diabetic Long-Evans Tokushima Otsuka（LETO） rats（n=18） used as age-matched normal controls.After 8 weeks（baseline）,6 rats in each of the two groups were sacrificed.Then the rest of the OLETF rats were divided into untrea-ted group（OLETF group,n=12） and metformin hydrochloride treated group（OLETF/M group,n=12）.At the age of 8,18 and 28 weeks,their body weights were obtained,and biochemical items were measured including serum triglyceride,cholesterol,glycerol,glucose and insulin levels with oral glucose tolerance test（OGTT）,and the perirenal adipose tissue（PAT） was obtained to measure the AQP7 mRNA expression（by Real-time PCR） and AQP7 protein relative expression（by Western blotting）.Results：（1） OLETF group rats developed diabetes at week 18 [60 min glucose：（25.67±6.78）mmol/L,120 min glucose：（16.19±2.98）mmol/L].The body weights and biochemical items including se-rum triglyceride,serum cholesterol,glucose and insulin levels of OGTT,were increased with the rats＇ age.The serum glycerol level was increased at week 18,but decreased at week 28.The serum glycerol level at weeks 8,18,28 were（52.61±11.80）μmol/L,（156.03±39.56）μmol/L and（130.84±25.46）μmol/L,respectively.（2） OLETF/M group rats developed diabetes at week 18 [60 min glucose：（18.64±6.67）mmol/L,120 min glucose：（14.13±5.21）mmol/L],but the glucose level at week 28 [60 min glucose：（11.72±3.06）mmol/L,120 min glucose：（12.42±2.30）mmol/L] became lower than that at week 18.The body weights and Biochemical items including serum triglyceride,serum cholesterol,serum glycerol and insulin levels of OGTT of the OLETF/M group rats,were of no significant difference from those of the OLETF group rats.The two groups were compared： in serum triglyceride [at week 18：（0.88±0.14） vs.（1.09±0.44）mmol/L;at week 28（1.06±0.51） vs.（2.20±1.51）mmol/L];serum cholesterol [at week 18（2.18±0.14） vs.（2.30±0.21）mmol/L,at week 28（1.90±0.19） vs.（2.36±0.35）mmol/L,P0.05];serum glycerol [at week 18（77.28±9.06） vs.（156.03±39.56）μmol/L,P0.05,at week 28（58.44±14.03） vs.（130.84±25.46）μmol/L,P0.01].（3） Expression of perirenal adipose tissue AQP7 mRNA and protein levels： with rats age and obesity developed,compared with the same group rats at 8 week,the AQP7 mRNA expression of OLETF group increased 67.5% at 18 week and 41.7% at 28 week respectively,the AQP7 protein expression of OLETF group increased 21.9% at 18 week and 8.9% at 28 week respectively,the AQP7 mRNA expression of OLETF/M group increased 25% at 18 week and 8.3% at 28 week respectively,the AQP7 protein expression of OLETF/M group increased 14.6% at 18 week and 1.6% at 28 week respectively.AQP7 mRNA and protein expression were increased at 18 weeks and decreased at 28 weeks not only in OLETF groups but also in OLETF/M groups as it were consistent with serum glycerol.In the OLETF/M group,the expression of AQP7 mRNA and protein levels were lower than those in age-matched OLETF groups,though there was no statistic difference between the two groups. In the OLETF/M group,the expression of AQP7 mRNA and protein levels were lower than those in the age-matched OLETF group,though there was no statistic difference between the two groups.Conclusion： AQP7 of visceral adipose tissue may participate in glucose and lipid metabolism associated with diabetes and obesity.Metformin can improve OLETF rat glucose and lipid,but not contribute to AQP7 mRNA and AQP7 protein expression of perirenal adipose tissue.