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

OBJECTIVE: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. 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 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 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 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. 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.

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