[Effects of telmisartan on the expression of adiponectin and its receptors in testes of type 1 diabetic rats].

ABSTRACT

OBJECTIVE: To explore the effects of telmisartan on the expressions of adiponectin and adiponectin receptor and its signal transduction pathway AMP-activated protein kinase (AMPK), Akt/endothelial nitric oxide synthase (Akt/e-NOS/NO) and examine the possible protective mechanisms of telmisartan in testis of type 1 diabetic rats. METHODS: A total of 27 male Sprague-Dawley rats were randomly divided into normal control (NC, n=8) group and diabetic model (n=19) group. Diabetes was induced by an intraperitoneal injection of streptozotocin (STZ). And 16 established diabetic rats were randomly divided into diabetic control (DM, n=8) and diabetic treated with telmisartan (DT, n=8) groups. Group DT received a lavage of telmisartan while groups NC and DM had an equal volume of normal saline by gavage. At the end of 8-week of telmisartan treatment, the animals were sacrificed after harvesting of blood samples. Bilateral testes were extracted and epididymis was minced for preparing sperm suspension. Blood samples were used to detect the related parameters. Some tresticular tissues were fixed in neutral 40% formaldehyde solution and processed for histological analysis. And the remaining testicular tissues were immediately placed into liquid nitrogen and then stored in a -70 °C refrigerator until analyses. The levels of insulin and sex hormone were detected by radioimmunoassay. The levels of adiponectin, interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) were assayed by enzyme-linked immunosorbent assay (ELISA). The mRNA expression of testicular adiponectin and its receptor was assessed by real-time fluorescent quantitative polymerase chain reaction (PCR). The protein expressions of testicular adiponectin, adiponectin receptor, AMPK, P-AMPK, AKT, P-AKT and e-NOS were analyzed by Western blot. RESULTS: There was significant pathological changes in testes in group DM than that in group NC. The levels of P-AKT/AKT, e-NOS and NO were significantly increased in group DM than those in group NC [(1.54 ± 0.27) vs (1.00 ± 0.00), (1.56 ± 0.26) vs (1.00 ± 0.00), (1.75 ± 0.28) vs (1.08 ± 0.02) µmol/g, all P<0.05]. The levels of serum adiponectin,testicular adiponectin and its receptor 1, and the ratio of P-AMPK to AMPK significantly decreased in group DM than that in group NC [(622.46 ± 95.86) vs (2 022.07 ± 51.13)ng/ml, (0.66 ± 0.09) vs (1.00 ± 0.00), (0.68 ± 0.05) vs (1.00 ± 0.00), (0.34 ± 0.11) vs (1.00 ± 0.00), all P<0.05]. There was no significant difference in the expression of adiponectin receptor 2 between group DM and NC [(1.02 ± 0.13) vs (1.00 ± 0.00), P>0.05]. After 8-week telmisartan treatment, the pathological changes of testes became alleviated in diabetic rats. The levels of P-AKT/AKT, e-NOS and NO significantly decreased in group DT than those in group DM [(1.24 ± 0.39) vs (1.54 ± 0.27), (1.16 ± 0.47) vs (1.56 ± 0.26), (1.35 ± 0.30) vs (1.75 ± 0.28) µmol/g, all P<0.05]. The serum and testicular levels of adiponectin and testicular adiponectin receptor 1 significantly increased in group DT than those in group DM [(1 051.55 ± 102.55) vs (622.46 ± 95.86), (0.84 ± 0.09) vs (0.66 ± 0.09), (0.80 ± 0.07) vs (0.68 ± 0.05), all P<0.05]. No significant difference existed in the ratio of P-AMPK to AMPK in testes or the expression of adiponectin receptor 2 between group DM and NC [(0.65 ± 0.52) vs (0.34 ± 0.11), (1.02 ± 0.15) vs (1.02 ± 0.13), all P>0.05]. CONCLUSION: Telmisartan may reduce the injury degree of testes and play protective roles in testicular tissues in diabetic rats by regulating the expressions of adiponectin, adiponectin receptor and the signal pathways mediated by adiponectin receptor.