Duan Yu min, Yuan Zhen fang, Yao Jun, Zhang Ting ting, Chen Cheng, Guo Xiao hui
Department of Endocrinology, Peking University First Hospital, Beijing 100034, China.
Beijing Da Xue Xue Bao Yi Xue Ban. 2011 Feb 18;43(1):117-22.
To observe perirenal adipose tissue aquaporin 7 (AQP7) mRNA and protein expression in the spontaneous type 2 diabetes animal model Otsuka Long-Evans Tokushima Fatty (OLETF) rats in different stages of diabetes and explore the role of AQP7 in obesity development and diabetes.
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 untreated 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).
(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 serum 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,P<0.05];serum glycerol [at week 18 (77.28 ± .06) vs. (156.03 ± 39.56)μmol/L,P<0.05,at week 28 (58.44 ± 14.03) vs. (130.84 ± 25.46)μmol/L, P<0.01]. (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.
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.
观察自发性2型糖尿病动物模型大耳白兔（OLETF）大鼠糖尿病不同阶段肾周脂肪组织水通道蛋白7（AQP7）mRNA和蛋白表达，探讨AQP7在肥胖及糖尿病发生发展中的作用。
选取OLETF大鼠30只，同品系非糖尿病大耳白兔（LETO）大鼠18只作为年龄匹配的正常对照。8周龄（基线）时，两组各处死6只大鼠。其余OLETF大鼠分为未治疗组（OLETF组，n = 12）和盐酸二甲双胍治疗组（OLETF/M组，n = 12）。于8、18、28周龄时测量大鼠体重，检测生化指标，包括血清甘油三酯、胆固醇、甘油、血糖和胰岛素水平（口服葡萄糖耐量试验OGTT），并获取肾周脂肪组织（PAT）检测AQP7 mRNA表达（实时荧光定量PCR法）和AQP7蛋白相对表达（蛋白质印迹法）。
（1）OLETF组大鼠于18周龄时出现糖尿病[60 min血糖：（25.67±6.78）mmol/L，120 min血糖：（16.19±2.98）mmol/L]。大鼠体重及OGTT的生化指标，包括血清甘油三酯、血清胆固醇、血糖和胰岛素水平随年龄增加而升高。血清甘油水平于18周龄时升高，但在28周龄时下降。8、18、28周龄时血清甘油水平分别为（52.61±11.80）μmol/L、（156.03±39.56）μmol/L和（130.84±25.46）μmol/L。（2）OLETF/M组大鼠于18周龄时出现糖尿病[60 min血糖：（18.64±6.67）mmol/L，120 min血糖：（14.13±5.21）mmol/L]，但28周龄时血糖水平[60 min血糖：（11.72±3.06）mmol/L，120 min血糖：（12.42±2.30）mmol/L]低于18周龄时。OLETF/M组大鼠体重及OGTT的生化指标，包括血清甘油三酯、血清胆固醇、血清甘油和胰岛素水平与OLETF组大鼠无显著差异。两组比较：血清甘油三酯[18周龄时：（0.88±0.14）与（1.09±0.44）mmol/L；28周龄时（1.06±0.51）与（2.20±1.51）mmol/L]；血清胆固醇[18周龄时（2.18±0.14）与（2.30±0.21）mmol/L，28周龄时（1.90±0.19）与（2.36±0.35）mmol/L，P<0.05]；血清甘油[18周龄时（77.28±0.06）与（156.03±39.56）μmol/L，P<0.05，28周龄时（58.44±14.03）与（130.84±25.46）μmol/L，P<0.01]。（3）肾周脂肪组织AQP7 mRNA和蛋白水平表达：随大鼠年龄增长及肥胖发生，与8周龄时同组大鼠相比，OLETF组AQP7 mRNA表达在18周龄时增加67.5%，28周龄时增加41.7%，OLETF组AQP7蛋白表达在18周龄时增加21.9%，28周龄时增加8.9%，OLETF/M组AQP7 mRNA表达在18周龄时增加25%，28周龄时增加8.3%，OLETF/M组AQP7蛋白表达在18周龄时增加14.6%，28周龄时增加1.6%。不仅OLETF组，OLETF/M组AQP7 mRNA和蛋白表达在18周龄时升高，28周龄时降低，与血清甘油情况一致。在OLETF/M组，AQP7 mRNA和蛋白水平表达低于年龄匹配的OLETF组，尽管两组间无统计学差异。
内脏脂肪组织AQP7可能参与糖尿病和肥胖相关的糖脂代谢。二甲双胍可改善OLETF大鼠糖脂代谢，但对肾周脂肪组织AQP7 mRNA和AQP7蛋白表达无影响。
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